New insight into the formation of structural defects in poly(vinyl chloride)

The monomer conversion dependence of the formation of the various types of defect structures in radical suspension polymerization of vinyl chloride was examined via both H-1 and C-13 NMR spectrometry. The rate coefficients for model propagation and intra- and intermolecular hydrogen abstraction reactions were obtained via high-level ab initio molecular orbital calculations. An enormous increase in the formation of both branched and internal unsaturated structures was observed at conversions above 85%, and this is mirrored by a sudden decrease in stability of the resulting PVC polymer. Above this threshold-conversion, the monomer is depleted from the polymer-rich phase, and the propagation rate is thus substantially reduced, thereby allowing the chain-transfer processes to compete more effectively. In contrast to the other defects, the chloroallylic end groups were found to decrease at high conversions. On the basis of the theoretical and experimental data obtained in this study, this decrease was attributed to copolymerization and abstraction reactions that are expected to be favored at high monomer conversions. Finally, a surprising increase in the concentration of the methyl branches was reported. Although a definitive explanation for this behavior is yet to be obtained, the involvement of transfer reactions of an intra- or intermolecular nature seems likely, and (in the latter case) these could lead to the presence of tertiary chlorine in these defects

Influence of health interventions on quality of life in seriously ill children at the end of life : a systematic review protocol

Background: Seriously ill children suffer from numerous symptoms at the end of their lives, including pain, anxiety, and restricted communication. There are currently no comprehensive overviews of which health interventions have proven benefits and which have proven detrimental effects on the quality of life of children in an end-of-life context. In order to identify potential quality indicators to eventually improve care, a systematic review of available evidence is needed. The aim of the current systematic review will be to make an overview of the influence of health interventions on associated outcomes related to quality of life at the end of life in seriously ill children. Methods: A systematic search will be conducted in MEDLINE, Embase, CENTRAL, CINAHL, and Web of Science. We will include quantitative empirical designs looking into the influence of a health intervention on (proxies of) quality of life at the end of life in seriously ill children. Three independent authors will review titles and abstracts and screen full texts against eligibility criteria. One reviewer will carry out full data extraction and quality assessment, and a 20% random sample will be extracted and assessed by two independent reviewers. We will use the QualSyst Tool for assessment of the quality of the included studies (QualSyst Tool) for quality assessment; overall strength of the body of evidence will be assessed using the Grading of Recommendations Assessment Development, and Evaluation (GRADE) approach. An overview table of health interventions will be discussed through narrative synthesis. Should sufficient homogeneous publications arise, we will perform meta-analyses with a random-effects model. Our protocol adheres to the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) checklist for study protocols. Discussion: As part of a larger project, we will use the results of this review to identify a first set of quality indicators for the care for children at the end of life. Reviewing the current span of evidence and identifying research gaps will uncover future research priorities into the care for children at the end of life

Simple peptide quantification approach for MS-based proteomics quality control

Despite its growing popularity and use, bottom-up proteomics remains a complex analytical methodology. Its general workflow consists of three main steps: sample preparation, liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS), and computational data analysis. Quality assessment of the different steps and components of this workflow is instrumental to identify technical flaws and avoid loss of precious measurement time and sample material. However, assessment of the extent of sample losses along with the sample preparation protocol, in particular, after proteolytic digestion, is not yet routinely implemented because of the lack of an accurate and straightforward method to quantify peptides. Here, we report on the use of a microfluidic UV/visible spectrophotometer to quantify MS-ready peptides directly in the MS-loading solvent, consuming only 2 mu L of sample. We compared the performance of the microfluidic spectrophotometer with a standard device and determined the optimal sample amount for LC-MS/MS analysis on a Q Exactive HF mass spectrometer using a dilution series of a commercial K562 cell digest. A careful evaluation of selected LC and MS parameters allowed us to define 3 mu g as an optimal peptide amount to be injected into this particular LC-MS/MS system. Finally, using tryptic digests from human HEK293T cells and showing that injecting equal peptide amounts, rather than approximate ones, result in less variable LC-MS/MS and protein quantification data. The obtained quality improvement together with easy implementation of the approach makes it possible to routinely quantify MS-ready peptides as a next step in daily proteomics quality control

Prevalence of atopy, asthma and COPD in an urban and a rural area of an African country

SummaryThe objectives of this study were to determine the prevalence of asthma, atopy and COPD in Rwanda and to identify risk factors. The survey was conducted in Kigali, the Capital of Rwanda, and in Huye District, a rural area located in southern Rwanda.MethodsA total of 2138 subjects were invited to participate in the study.1920 individuals (90%) answered to questionnaires on respiratory symptoms and performed spirometry, 1824 had acceptable spirograms and performed skin-prick test. In case of airflow obstruction (defined as pre-bronchodilator ratio FEV1/FVC < LLN) a post bronchodilator spirometry was performed. Reversibility was defined as an increase in FEV1 of 200 ml and 12% above baseline FEV1 after inhalation of 400 mcg of salbutamol.ResultsThe mean age was 38.3 years; 48.1% of participants were males and 51.9% females. Airflow obstruction was found in 256 participants (14%); 163(8.9%) subjects were asthmatics and 82 (4.5%) had COPD. COPD was found in 9.6% of participants aged 45 years and above. 484 subjects had positive skin-prick tests (26.5%); house dust mite and grass pollen mix were the main allergens. Risk factors for asthma were allergy, female gender and living in Kigali. COPD was associated with cigarette smoking, age and male sex.Conclusionthis is the first study which shows the prevalence of atopy, asthma and COPD in Rwanda. Asthma and COPD were respectively diagnosed in 8.9% and 4.5% of participants. COPD was diagnosed in 9.6% of subjects aged ≥45 years.The prevalence of asthma was higher in urban compared to rural area

A Conserved EAR Motif Is Required for Avirulence and Stability of the Ralstonia solanacearum Effector PopP2 In Planta

(extract) Overall, this study reveals high conservation of the PopP2 effector in Korean R. solanacearum strains isolated from commercially cultivated tomato and pepper genotypes. Importantly, our data also indicate that the PopP2 conserved repressor motif could contribute to the effector accumulation in plant cells