Thermal study of the effect of several solvents on polymerization of acrylonitrile and their subsequent pyrolysis

The polymerization of acrylonitrile to polyacrylonitrile (PAN) has been studied using several solvents: N,N-dimethylformamide (DMF), hexane, toluene, water, and in bulk form (no solvent). The addition of DMF is the only case where both monomer and polymer are soluble in the solvent. Thermal analyses of the resultant products after polymerization have been performed by differential scanning calorimetry and pyrolysis–gas chromatography: mass spectrometry. The effect of the solvents employed as media for polymerization is interpreted from the results of the thermal and structural (X-ray diffraction) methods. The polymer samples obtained when using water or toluene as solvents have the greater content of amorphous components compared to the others. The amide molecules are difficult to completely eliminate in the product obtained after the polymerization reaction and even after prolonged heating at 110°C and remain occluded. DMF can be considered to exert a plasticized effect on PAN and is even capable of forming complexes by dipolar bonding. As a result of this interaction, the thermogram is quite different from the other samples studied in the present work, showing a single sharp exothermic peak. This is associated with nitrile group polymerization (cyclization) of PAN. It is deduced that the amount of heat evolved as well as the temperature interval over which it is released are influenced by the chemical processing of PAN, in particular when using DMF as solvent for both monomer and polymer. Pyrolysis of the different PAN samples revealed the release of occluded solvent molecules, mainly when using DMF, and compounds produced from the thermal degradation processes. Different types of cyclized compounds, such as pyridine derivatives and aromatic nitriles were identified. All these compounds could be derived from cyclized PAN structures which are not completely degraded by the thermal treatment of pyrolysis. Alkyldinitriles have also been tentatively identified associated with the final molecular breakdown of cyclized structures with six-member rings by pyrolysis. Valuable complementary information on the structure of the PAN samples (homopolymer) obtained using the different processing approaches involving several solvent media has been provided by pyrolysis. The present results will improve our understanding of the evolution of the structure and properties of carbon and activated carbon fibres which will enable us to establish processing strategies in order to obtain these materials under adequate and reproducible conditions.Peer reviewe

Wandering spleen on a 68Ga-DOTATOC-PET/CT scan

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Mobile Phone-Based Use of the Photoplethysmography Technique to Detect Atrial Fibrillation in Primary Care: Diagnostic Accuracy Study of the FibriCheck App

BACKGROUND: Mobile phone apps using photoplethysmography (PPG) technology through their built-in camera are becoming an attractive alternative for atrial fibrillation (AF) screening because of their low cost, convenience, and broad accessibility. However, some important questions concerning their diagnostic accuracy remain to be answered. OBJECTIVE: This study tested the diagnostic accuracy of the FibriCheck AF algorithm for the detection of AF on the basis of mobile phone PPG and single-lead electrocardiography (ECG) signals. METHODS: A convenience sample of patients aged 65 years and above, with or without a known history of AF, was recruited from 17 primary care facilities. Patients with an active pacemaker rhythm were excluded. A PPG signal was obtained with the rear camera of an iPhone 5S. Simultaneously, a single‑lead ECG was registered using a dermal patch with a wireless connection to the same mobile phone. PPG and single-lead ECG signals were analyzed using the FibriCheck AF algorithm. At the same time, a 12‑lead ECG was obtained and interpreted offline by independent cardiologists to determine the presence of AF. RESULTS: A total of 45.7% (102/223) subjects were having AF. PPG signal quality was sufficient for analysis in 93% and single‑lead ECG quality was sufficient in 94% of the participants. After removing insufficient quality measurements, the sensitivity and specificity were 96% (95% CI 89%-99%) and 97% (95% CI 91%-99%) for the PPG signal versus 95% (95% CI 88%-98%) and 97% (95% CI 91%-99%) for the single‑lead ECG, respectively. False-positive results were mainly because of premature ectopic beats. PPG and single‑lead ECG techniques yielded adequate signal quality in 196 subjects and a similar diagnosis in 98.0% (192/196) subjects. CONCLUSIONS: The FibriCheck AF algorithm can accurately detect AF on the basis of mobile phone PPG and single-lead ECG signals in a primary care convenience sample.status: publishe

Noninvasive monitoring of long-term lentiviral vector-mediated gene expression in rodent brain with bioluminescence imaging

Gene transfer into the central nervous system is an emerging therapeutic strategy for a range of neurological diseases, including neurodegeneration. This approach would benefit from imaging technologies that could determine the extent, magnitude, and duration of transgene expression. We have used bioluminescence imaging (BLI) to image lentiviral vector-mediated gene transfer into the mouse brain. We constructed human immunodeficiency virus type 1 lentiviral vectors that encode firefly luciferase and transduce cells in culture. After stereotactic injection of these vectors into the brain, we were able to detect luciferase expression in living mice and rats. We characterized the signal in mouse brain in terms of localization, kinetics, resolution, and reproducibility and demonstrated that it correlates with the level of firefly luciferase expression. Although the signal decreased gradually to about 20% of the initial value in the first month, the signal remained constant thereafter for more than 10 months. We demonstrated that the light signal can be used as a reporter by using a bicistronic vector. This is the first study to document noninvasive monitoring of long-term transgene expression in the adult mouse brain and provides the basis for applying BLI in the study of brain disease and gene therapeutic strategies.status: publishe

A p-[18F]fluoroethoxyphenyl bicyclic nucleoside analogue as a potential positron emission tomography imaging agent for varicella-zoster virus thymidine kinase gene expression

We recently reported a new positron emission tomography (PET) reporter gene, namely, varicella-zoster virus thymidine kinase (VZV-tk) in combination, with carbon-11 or fluorine-18 labeled m-alkoxyphenyl bicyclic nucleoside analogues (BCNAs) as PET reporter probes. We now report the synthesis and evaluation of p-alkoxyphenyl-BCNA tracers ([ (11)C]- 4 and [ (18)F]- 5), which are found to be superior to the m-alkoxyphenyl-BCNA tracers. In particular, the fluorine-18 labeled tracer ([ (18)F]- 5, IC 50 of 5 is 4.2 muM) shows a higher accumulation in VZV-tk expressing cells than the previously reported m-methoxyphenyl BCNA. [ (11)C]- 4 and [ (18)F]- 5 were synthesized by heating the phenol precursor 3 with (11)CH 3I and (18)FCH 2CH 2Br, respectively, as alkylating agents. In vitro evaluation of [ (11)C]- 4 and [ (18)F]- 5 in 293T cells showed about 14- and 54-fold higher uptake, respectively, into VZV-tk gene-transduced cells compared to control cells. LC-MS analysis confirmed the formation of monophosphate derivative of 5 upon catalysis by VZV TK. In vivo studies of this new reporter gene/probe system are in progress.status: publishe

Barriers and opportunities for return-to-work of cancer survivors: Time for action-rapid review and expert consultation

Background: The spread of early detection and the improvement of cancer treatment have led to an increased prevalence of cancer survivors, including in the working age population. Return-to-work (RTW) of cancer survivors has become a key issue for national cancer control plans. This study aims (1) to identify the factors that have an impact on RTW of cancer survivors and to draw a risk profile supporting health professionals in the screening of those at risk for barriers of RTW and (2) to sharpen these results with input from health, social security and academic Belgian experts and to provide evidence-based recommendations that facilitate RTW of cancer survivors. Methods: A rapid review was conducted, based on the methodology elaborated by The Knowledge to Action Research Programme and researchers from the University of York, including a quality assessment of retained studies. Next, the Delphi method was used to organize a consultation with experts in order to discuss, validate and complement the results. Results: Forty-three out of 1860 studies were included. We identified nine risk factors grouped into four categories: socio-demographic, disease and treatment-related, work-related, and personal and subjective factors. Experts suggested dividing them into two even groups: factors which are modifiable and those which are not. The awareness of health professionals regarding the identified factors, a better assessment of work capacities, clarity on the rights and obligations of employers and workers alike, and the setup of a positive discrimination employment policy for cancer survivors were acknowledged as factors facilitating RTW of cancer survivors. Conclusions: The awareness of health professionals regarding barriers of RTW may improve the early identification of cancer survivors at risk for prolonged time to RTW and may allow early supportive intervention. Social and employment policies should be better tailored to support both employers and cancer survivors in the RTW process, providing incentives to positively discriminate cancer survivors on prolonged sick leave.SCOPUS: ar.jinfo:eu-repo/semantics/publishe