Presence Of EVA Research Articles

ARTERIAL STIFFNESS ESTIMATED BY BRACHIAL OSCILLOMETRY PREDICTS PROGRESSION TO HYPERTENSION IN PATIENTS WITH NORMAL AMBULATORY BLOOD PRESSURE

Objective: There is growing evidence that arterial stiffness can precede hypertension (HTN). This study aimed to assess the predictive value of Pulse Wave Velocity, estimated by brachial oscillometry (ePWV), for incident HTN in patients with initially normal ambulatory BP measurement (ABPM) after one year of follow-up. Design and method: This retrospective, observational, longitudinal study included all consecutive patients referred to a HTN Unit with suspected naïve HTN, without prior pharmacological treatment. EVA was defined according to ePWV exceeding the 90th percentile of its age group (Mobil-O-Graph, IEM®). Incident HTN was defined as ABPM at follow-up > 130/80 mmHg or prescription of antihypertensive medication. Standard clinical tests and ABPM were performed at baseline and after 12 months. Results: 223 consecutive patients with ABPM <130/80 mmHg entered the study, with 155 women (69.5%), a mean age of 47.9 years (±13.5), mean office BP of 128/73 (±13/8), mean ABPM of 118/73 (±7/5) mmHg and mean estimated PWV of 7.74 m/s (±1.7). At baseline, 51.1% of patients showed EVA. At follow-up, after a mean time of 1,1 years, 114 participants presented elevated ABPM. After adjustment for age, gender and ambulatory BP, presence of EVA at baseline was associated with progression to HTN at follow-up (OR:2,5;IC:1,4-4,6;p = 0.003). Furthermore, the pattern of PWV-EVA and incident HTA according to age were superimposable (Image). Arterial stiffness defined as ePWV > 10 m/s was also significantly associated with incident HTN, but showed a completely different distribution in age compared with incident HTN. Of note, arterial stiffness at follow-up was mainly determined by EVA at baseline (OR:6.1;IC:3.2-11.6;p = 0.001), but not by BP traits. Conclusions: Arterial damage, characterized as early vascular aging according to estimated PWV by brachial oscillometry, doubles the probability of sustained HTN one year after initial assessment in naïve patients with normal ABPM at baseline, independently of ambulatory and or office blood pressure at baseline. On the other hand, the main determinant of arterial stiffness at follow-up was elevated ePWV at baseline, but not blood pressure traits.

The EVA Study: Early Vascular Aging in Women With History of Preeclampsia.

Background Early vascular aging (EVA) is associated with higher risk of adverse cardiovascular events and can be estimated noninvasively by assessing arterial hemodynamics. Women with a history of preeclampsia have increased risk of cardiovascular disease, but underlying mechanisms are incompletely understood. We hypothesized that women with a history of preeclampsia display persistent arterial abnormalities and EVA in the postpartum period. Methods and Results We performed a comprehensive, noninvasive arterial hemodynamic evaluation in women with a history of preeclampsia (n=40) and age-matched controls with previous normotensive pregnancies (n=40). We used validated methods integrating applanation tonometry with transthoracic echocardiography to obtain measures of aortic stiffness, steady and pulsatile arterial load, central blood pressure, and arterial wave reflections. Presence of EVA was defined as aortic stiffness higher than that predicted from reference values based on the participant's age and blood pressure. The association of preeclampsia with arterial hemodynamic variables was assessed with multivariable linear regression, and the association of severe preeclampsia with EVA was assessed with multivariable logistic regression, adjusted for confounders. We found that women with a history of preeclampsia had greater aortic stiffness, steady arterial load, central blood pressure, and arterial wave reflections when compared with controls. We observed a dose-response relationship, with the greatest abnormalities observed in subgroups with severe, preterm, or recurrent preeclampsia. Women with severe preeclampsia had 9.23 times greater odds of having EVA as compared with controls (95% CI, 1.67-51.06, P=0.011) and 7.87 greater odds of EVA as compared with women with nonsevere preeclampsia (95% CI, 1.29-47.77, P=0.025). Conclusions Our study comprehensively characterizes arterial hemodynamic abnormalities after preeclampsia and suggests that specific subgroups of women with a history of preeclampsia exhibit greater alterations in arterial hemodynamics related to arterial health. Our findings have important implications for understanding potential links between preeclampsia and cardiovascular events, and suggest women with severe, preterm, or recurrent preeclampsia as subgroups who may deserve intensification of efforts for prevention and early detection of cardiovascular disease.

The application of the synergistic effect between the crystal structure of poly(lactic acid) (PLA) and the presence of ethylene vinyl acetate copolymer (EVA) to produce highly ductile PLA/EVA blends

In this paper, we produced ethylene vinyl acetate copolymer (EVA)-filled poly(lactic acid) (PLA) blends by extrusion and injection moulding. We annealed the injection-moulded specimens at 80 °C, 100 °C, 120 °C and 140 °C to produce various crystal structures in PLA. Then we investigated the cross-effect between the crystal structure of PLA and the presence of EVA on the mechanical, impact, calorimetric, thermomechanical and heat deflection temperature properties of the blends. We found a synergistic toughening effect between the crystal structure of PLA that developed during annealing and the presence of dispersed EVA particles in the PLA matrix. The blend had a very high impact strength of over 65 kJ m−2, which is three times higher than the impact strength of acrylonitrile butadiene styrene copolymer (~ 20 kJ m−2), and thus it is very promising for technical applications.

High-resolution melt (HRM) analysis for detection of SNPs associated with pyrethroid resistance in the southern cattle fever tick, Rhipicephalus (Boophilus) microplus (Acari: Ixodidae)

The southern cattle fever tick, Rhipicephalus (Boophilus) microplus, is the most economically important ectoparasite of cattle worldwide. A limitation for sustainable control and eradication is the emergence of acaricide resistance among tick populations. Molecular diagnostic tools offer the opportunity to detect resistance rapidly, which can be complemented with confirmatory bioassays with larvae and adult ticks that are more resource and time consuming to generate. Synthetic pyrethroid resistance is one of the most prevalent and well-studied forms of resistance in arthropods, being linked with target site alterations in the sodium ion channel gene. Here, we report research on a novel molecular method to detect mutations in the para-sodium channel gene of R. microplus associated with acaricide resistance that is based on quantitative PCR high-resolution melt (HRM) analysis. Genomic DNA fragments of domains II and III of the para-sodium channel gene were amplified by real-time PCR in the presence of EVA®Green dye to test resistant and susceptible reference ticks from the U.S., Brazil, and Mexico. Larval packet tests with discriminating doses and a modified lethal time analysis were performed to confirm resistance to permethrin, cypermethrin, deltamethrin, and flumethrin in laboratory strains. Tick specimens collected from cattle that were inspected at the United States Port-of-Entry at the Texas-Mexico border were also genotyped. Previously described mutations associated with pyrethroid resistance (T170C, C190A, G184C, and T2134A) were successfully detected by qPCR-HRM in different genotypes and confirmed by sequencing. A novel non-synonymous SNP located at domain III (C2136A) and the G215T mutation in domain II, previously described only in Asian R. microplus and R. australis, were also detected with the HRM and confirmed by sequencing. This technique could be adapted for high-throughput screening, detection, and discovery of allele-specific mutations in cattle tick outbreak populations to inform eradication strategies in the USA. This knowledge could also be applied to integrated control programs in other parts of the world where R. microplus is endemic and where similar SNPs have been identified associated with pyrethroid resistance. This study highlights the existence of several mutations in the para-sodium channel gene in different combinations in field populations of R. microplus from Mexico.

Transparent blown films from poly(lactide) and poly(ethylene-co-vinyl acetate) compounds: Structure and property

The application range of poly(lactide), PLA, films is limited due to the brittleness and notch-sensitivity. In this work, thin films with balanced properties were fabricated by melt blowing of PLA and poly(ethylene-co-vinyl acetate) (EVA) blends. The film thickness is dependent on the taken-up speed and reached to around 10 μm at the taken-up speed over 14 m/min. The presence of EVA not only significantly enhanced the tensile toughness and notch-resistance of the PLA films but also retained high transmittance. The films exhibited anisotropic mechanical performances which were correlated to the micro-morphology differences between the take-up direction (DD) and the transversal direction (TD) as characterized by atomic force microscope. In addition, the EVA with 80 wt% VA units showed better overall modification effect on the PLA films than the EVA with 60 wt% VA units. Superior mechanical properties of PLA/EVA (80/20) blends such as tensile strength of 50–60 MPa, elongation at break up to 230% and tear strength of 85 kN/m were achieved in the DD direction. Meanwhile, balanced properties were also achieved in TD direction. Moreover, a transmittance of around 90% was obtained for the PLA/EVA films which are comparable to neat PLA films. A high enough VA unit content is crucial for superior mechanical properties and high transparency.

Plasticized chitosan/polyolefin films produced by extrusion

Plasticized chitosan and polyethylene blends were produced through a single-pass extrusion process. Using a twin-screw extruder, chitosan plasticization was achieved in the presence of an acetic acid solution and glycerol, and directly mixed with metallocene polyethylene, mPE, to produce a masterbatch. Different dilutions of the masterbatch (2, 5 and 10wt% of plasticized chitosan), in the presence of ethylene vinyl acetate, EVA, were subsequently achieved in single screw film extrusion. Very small plasticized chitosan domains (number average diameter <5μm) were visible in the polymeric matrix. The resulting films presented a brown color and increasing haze with chitosan plasticized content. Mechanical properties of the mPE films were affected by the presence of plasticized chitosan, but improvement was observed as a result of some compatibility between mPE and chitosan in the presence of EVA. Finally the incorporation of plasticized chitosan affected mPE water vapor permeability while oxygen permeability remained constant.

Oxygen permeability and the mechanical and thermal properties of (low‐density polyethylene)/poly (ethylene‐co‐vinyl acetate)/organoclay blown film nanocomposites

Various (low‐density polyethylene)/poly(ethylene‐co‐vinyl acetate) (LDPE/EVA) nanocomposites containing organoclay were prepared by one‐ and two‐step procedures through melt blending. The resultant nanocomposites were then processed via the film blowing method. From the morphological point of view, X‐ray diffraction and optical microscopy studies revealed that although a prevalent intercalated morphology was evident in the absence of EVA, a remarkable increase of organoclay interlayer spacing occurred in the EVA‐containing systems. The advantages of the addition of EVA to the LDPE/organoclay nanocomposites were confirmed in terms of oxygen barrier properties. In other words, the oxygen transmission rates of the LDPE/EVA/organoclay systems were significantly lower than that of the LDPE/organoclay sample. The LDPE/EVA/organoclay films had better mechanical properties than their counterparts lacking the EVA, a result which could be attributed to the improvement of the organoclay reinforcement efficiency in the presence of EVA. Differential scanning calorimetry and thermogravimetric analysis experiments were performed to follow the effects of the EVA and/or organoclay on the thermal properties of LDPE. Finally, the films produced from the two‐step‐procedure compound showed enhanced oxygen barrier properties and mechanical behavior as compared to the properties of the films produced via the one‐step procedure. J. VINYL ADDIT. TECHNOL., 19:132–139, 2013. © 2013 Society of Plastics Engineers

Thermal and morphological properties of high‐density polyethylene/ethylene–vinyl acetate copolymer composites with polyhedral oligomeric silsesquioxane nanostructure

AbstractThe demand for improved properties of common polymers keeps increasing, and several new approaches have been investigated. In the study reported here, composites with a polymer matrix comprising a blend of high‐density polyethylene with ethylene–vinyl acetate copolymer (EVA), and with polyhedral oligomeric silsesquioxane (POSS) as a nanostructure, were processed and characterized in terms of their thermal and morphological properties. For the preparation of the composites, the concentrations of the blend components (0, 50 and 100 wt%) and of the POSS (0, 1 and 5 wt%) were varied. X‐ray diffraction results indicated that the presence of EVA in the composites led to the appearance of crystalline domains at lower POSS concentrations. Transmission and scanning electron microscopy showed that samples with 1 wt% of POSS had a homogeneous distribution in the polymer matrix with average dimensions of ca 150 nm. However, the formation of aggregates occurred in samples with 5 wt% of POSS. Differential scanning calorimetry and thermogravimetic analyses indicated that the POSS did not affect the melt and degradation temperatures of the polymer matrix. POSS underwent aggregation at higher concentrations during the composite processing, indicating a solubility limit of around 1 wt%. The presence of EVA in the composite favors POSS aggregation due to an increase in the polarity of the polymer matrix. Copyright © 2009 Society of Chemical Industry

Nonisothermal crystallization kinetics and determination of surface‐folding free energy of PP/EVA/OMMT nanocomposites

AbstractCrystalline structures, nonisothermal crystallization behavior and surface folding free energy of polypropylene (PP)/poly(ethylene‐co‐vinyl acetate) (EVA) blend‐based organically modified montmorillonite (OMMT) nanocomposites were investigated by use of wide angle X‐ray scattering (WAXS) and differential scanning calorimetry (DSC) techniques. Nonisothermal crystallization kinetic analysis was performed using Avrami equation modified by Jeziorny as well as combined Avrami‐Ozawa method. Surface folding free energy and activation energy for PP and nanocomposite samples were also determined employing Hoffman‐Lauritzen's and Vyazovkins's approaches, respectively. The results obtained from transmission electron microscopy (TEM) showed that presence of EVA, which attracts most of the layered silicates, reduces number density of heterogeneous nuclei in the matrix and as a consequence, decreases the nucleation rate. Incorporation of EVA, PP‐g‐MA and OMMT results in a decrease of the chain surface folding free energy level. It was shown that although, OMMT acts as a barrier against the PP macromolecular motion but interestingly, it increases the overall crystallization rate. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 47: 674–684, 2009

Compatibilization of low‐density polyethylene/plasticized starch blends by reactive compounds and electron beam irradiation

AbstractBlends based on various compositions of low‐density polyethylene (LDPE) and plasticized starch (PLST) were prepared by melt extrusion and molding in the form of sheets under hot press. The rheology properties during mixing were studied in terms of torque and temperature against mixing time. The structural properties of LDPE/PLST blends before and after electron beam irradiation was characterized by IR spectroscopy, tensile mechanical testing, and scanning electron microscopy (SEM). The torque‐time curves during the mixing process showed that the values of torque in the first region of mixing for pure LDPE or LDPE/PLST blends are higher in the presence of the compatibilizer PEMA than that in the presence of EVA. In addition, the stability of mixing was attained after a short time in the presence of PEMA. The IR spectroscopy suggests that the compatibilization by EVA and PEMA compounds proceeds through the formation of hydrogen bonding during mixing and this compatibility was improved after electron beam irradiation. The stress–strain curves of pure LDPE and its blends with PLST showed the behavior of tough polymers with yielding properties. The SEM micrographs of the fracture surfaces give supports to the effect of EVA and PEMA as compatibilizers and the effect of electron beam irradiation. POLYM. COMPOS., 2008. © 2008 Society of Plastics Engineers

Mechanical and sorption properties of poly(ethylene-co-vinyl acetate)(EVA) compatibilized acrylonitrile butadiene rubber/natural rubber blend systems

Poly (ethylene-co-vinyl acetate) (EVA) has been used as a compatibilizer for heterogeneous natural rubber/acrylonitrile butadiene rubber (NR/NBR) blends. NR/NBR (50/50) blends were compatibilized with varying amounts, from 0 to 10 parts per hundred rubber (phr), of EVA. The compatibility of the blend components in presence of EVA has been evaluated in terms of mechanical and sorption characteristics. The mechanical properties were found to be improved by the addition of EVA upto 6 phr. The solvent resistance of the compatibilized samples has been observed to be higher compared to the uncompatibilized blends; attributed to the increased interfacial adhesion between the blend components. DSC studies showed a shift of glass transition temperatures of the blend components towards higher temperatures indicating increased rigidity of the matrix in presence of EVA.

Impact Modification of Polyoxymethylene (POM)

AbstractPolyoxymethylene (POM) was blended with various weight percentages of ethylene propylene diene terpolymer (EPDM) and ethylene vinyl acetate copolymer (EVA) separately in a twin screw extruder under optimum conditions. The mechanical properties of the blends such as tensile strength, impact strength and % elongation were measured. Increasing content of EPDM and EVA up to 7.5% increases the impact strength of POM. Addition of elastomer beyond 7.5% decreases the impact strength due to the poor adhesion between plastic and elastomer phase. POM/EPDM blends compatibilised with EVA showed improved impact strength. The present study reveals that the impact strength of POM can be improved by blending with EPDM and EVA. The incorporation of EVA as compatibiliser into POM/EPDM causes significant improvement in impact strength. Scanning electron microscopy (SEM) reveals enhanced adhesion of POM and EPDM in the presence of EVA up to the extent 5 parts per hundred of resin (phr) resulting in improved dispersion of the elastomer in the plastic matrix.

Poly(butyleneterephthalate)‐poly(ethylene‐co‐vinylacetate) polymer blends. Part II

AbstractThe more distinctive morphological features which appear in the micrographs of fracture surfaces of polymer blends of poly(butyleneterephthalate)(PBTP) with poly(ethylene‐covinylacetate) (EVA), obtained by polymerizing in different conditions dimethylterephthalate (DMT) and 1,4‐butanediol (4G) in the presence of EVA (with 4 percent w/w of vinylacetate, VA,), are shown and discussed. The micrograph investigation clearly points out that the adhesion between EVA particles and PBTP matrix increases with the extent of reaction between PBTP and EVA and, for the same time of reaction, by changing from an anchor to a paddle agitator. The mean diameter of the particles is also affected by time of reaction and by the geometry of the agitator, decreasing when the adhesion increases.