Influence of molecular weight, temperature, and extensional rheology on melt blowing process stability for linear isotactic polypropylene

In this work, three linear isotactic polypropylenes with different weight-average molecular weights, M-w, and comparable polydispersities were used to produce nonwovens by melt blowing technology at two different temperatures, T. The air/polymer flow rate was changed to maintain the same average fiber diameter, resulting in a different broadness of fiber diameter distribution, which was quantified by the coefficient of variation, CV. The elasticity of the material was evaluated by the reptation-mode relaxation time, lambda(1), and the Rouse-mode reorientation time, lambda(2), determined from the deformation rate dependent shear viscosity data. Extensional rheology was evaluated using uniaxial extensional viscosity measured over a very wide range of strain rates (2 x 10(4) s(-1)-2 x 10(6) s(-1)) using entrance pressure drop and Gibson methods. An obtained plateau value of uniaxial extensional viscosity at the highest extensional strain rates, eta(E,infinity) (normalized by the three times zero-shear rate viscosity, eta(0)), and the minimum uniaxial extensional viscosity, eta(E,min), were related to M-w and T using simple equations. It has been found that the stability of fiber production captured by CV depends exclusively on the extensional properties of the polypropylene melts, namely, eta(E,U,)infinity/3 eta(0) and eta(E,U,min). These findings are important especially with regard to the stable production of polymeric nanofibers by melt blowing technology

Modern Electric Traction of Skoda Plzen Vehicles

The electric traction vehicle producting plant SKODA Plzen - Transportations develops and produces electric traction drives with the top technological niveau. Electric vehicles are delivered to transport institutions in Czech Republic as well as abroad. Many Ma, and PhD. graduates of the University of Zilina take part in this successful activity.<br /

Evaluation of Thermally Induced Degradation of Branched Polypropylene by Using Rheology and Different Constitutive Equations

In this work, virgin as well as thermally degraded branched polypropylenes were investigated by using rotational and Sentmanat extensional rheometers, gel permeation chromatography and different constitutive equations. Based on the obtained experimental data and theoretical analysis, it has been found that even if both chain scission and branching takes place during thermal degradation of the tested polypropylene, the melt strength (quantified via the level of extensional strain hardening) can increase at short degradation times. It was found that constitutive equations such as Generalized Newtonian law, modified White-Metzner model, Yao and Extended Yao models have the capability to describe and interpret the measured steady-state rheological data of the virgin as well as thermally degraded branched polypropylenes. Specific attention has been paid to understanding molecular changes during thermal degradation of branched polypropylene by using physical parameters of utilized constitutive equations

The role of endoscopic retrograde cholangiopancreatography in choledochal cysts and/or abnormal pancreatobiliary junction in children

Introduction : Biliary cysts with an abnormal pancreatobiliary junction are one of the most common pancreatobiliary malformations. The main symptom is cholestasis; endoscopic retrograde cholangiopancreatography (ERCP) plays a key role in diagnosis. Aim : Retrospective evaluation of ERCP performed to diagnose abnormalities of the pancreatobiliary junction. Material and methods : We retrospectively evaluated ERCP performed to diagnose abnormalities of the pancreatobiliary junction, mainly choledochal cysts, in 112 children between 1990 and 2011. Results : We performed 112 examinations of 50 children with abnormal pancreatobiliary junction and choledochal cysts (15 males and 35 females, average age: 5 years, range: 1 month – 15 years). Cysts were associated with a common channel in 37 (74%) cases, were not associated with a common channel in 9 (18%) cases, and in 3 (6%) cases the common channel lacked cysts. We performed endoscopic papilla sphincterotomy on 33 (66%) patients; endoscopic drainage was performed 62 times, including 17 patients without papilla sphincterotomy. In 15 (30%) cases, we only performed sphincterotomy. Extraction of lithiasis was done in 2 (4%) cases. Both ERCP and magnetic resonance cholangiopancreatography (MRCP) were performed on 13 patients. There was concordance of the choledochal cyst and of the type of cyst in both methods; however, common channels could not be observed by MRCP. There was 1 serious complication (perforation after sphincterotomy) and 11 (9%) mild adverse events. Conclusions : When performed at an expert centre, ECRP is a safe and reliable procedure for children with choledochal cysts and/or an abnormal pancreatobiliary junction. Endoscopic retrograde cholangiopancreatography remains a reasonable alternative because MRCP has a limited ability to diagnose the precise anomalies of the pancreatobiliary junction and has no therapeutic capabilities

Pitfalls of commercially available HPV tests in HPV68a detection.

BackgroundHuman papillomavirus 68 (HPV68) is a probable carcinogenic HPV genotype which is included in almost all HPV screening assays and exists as two genetically variable subtypes (HPV68a and HPV68b). Routine HPV sample testing has shown that the cobas 4800 HPV Test (Roche) provides higher false-negative rates for HPV68 status than PapilloCheck HPV-Screening (Greiner Bio-One). The aim of our study was to evaluate the efficacy of cobas 4800 in HPV68 detection.MethodsA total of 2,145 cervical/cervicovaginal samples from women aged 17-88 were tested for HPV68 status using the cobas 4800 and PapilloCheck HPV tests. Viral load was assessed by quantitative PCR in all of the HPV68-positive cases. HPV68a/b subtyping was performed with real-time PCR followed by high resolution melting curve analysis, and was subsequently confirmed by Sanger sequencing.ResultsCobas 4800 detected HPV positivity in only 13/33 HPV68 single-genotype infection cases. Viral load was comparable across both tested subgroups. HRM analysis and Sanger sequencing identified the HPV68a subtype in all of the 20 instances of cobas 4800 false negatives. HPV68a and HPV68b were detected in 3/13 and 10/13 cases identified as other HPV-positive by cobas 4800.ConclusionThe HPV68a subtype was missed by cobas 4800 in more than 85% of all HPV68a-positive cases. Therefore, commercially available assays may underestimate HPV68 prevalence

Conjugated Hyperbilirubinemia in Infants: Is There Still a Role for ERCP?

Over a twenty-year period, we performed 255 ERCP procedures in infants aged up to 1 year. ERCP was indicated in cholestatic infants with suspicion of biliary obstruction. The most common diagnosis was biliary atresia (48%), choledochal cysts (13%), and choledocholithiasis (4%). The procedure complication rate was 13.7%. Hyperamylasemia occurred in 12.9%. More severe complications were rare‐0.8% of ERCP procedure. There were no cases of postprocedural pancreatitis or death. Our study has proved that ERCP is a safe and reliable method in this age group. Its high specificity and negative predictive value for extrahepatic biliary atresia can prevent unnecessary surgeries in patients with normal bile ducts or endoscopically treatable pathologies