Polyacrylonitrile (PAN)/crown ether composite nanofibers for the selective adsorption of cations

In this study, we prepared electrospun polyacrylonitrile (PAN) nanofibers functionalized with dibenzo-18-crown-6 (DB18C6) crown ether and showed the potential of these fibers for the selective recovery of K+ from other both mono- and divalent ions in aqueous solutions. Nanofibers were characterized by SEM, FTIR and TGA. SEM results showed that the crown ether addition resulted in thicker nanofibers and higher mean fiber diameters, in a range of 138 to 270 nm. Batch adsorption experiments were conducted in order to evaluate the potential of the crown ether modified nanofibers as an adsorbent for ion removal. The maximum adsorption capacity of the crown ether modified nanofibers for K+ was 0.37 mmol g−1 and the nanofibers followed the selectivity sequence of K+ > Ba2+ > Na+ ∼ Li+ for single ion experiments. Adsorption of Ba2+ ions onto crown ether-modified nanofiber was examined by XPS and the results confirmed the adsorption of the ion. Mixed ion adsorption experiments revealed competitive adsorption between K+ and Ba2+ ions for the available binding sites. This effect was not observed for the other monovalent ions present in the solution and exceptionally high selectivities for K+ over Li+ and Na+ were obtained. Also the crown ether modified nanofibers exhibited good regeneration properties and a good reusability over multiple consecutive adsorption–desorption cycles. Electrospinning is thus shown to be a very versatile tool to prepare crown ether functional polymer adsorbents for the selective recovery of ions

Mixed mode delamination in carbon nanotube/nanofiber interlayered composites

Laminated composites mostly suffer from layer separation and/or delamination, which may affect the stiffness, strength and lifetime of structures. In this study, we aim to produce micron-scale thin carbon nanotubes (CNTs) reinforced adhesive nanofibrous interleaves and to explore their effectiveness when incorporated into structural composites. Neat polyvinyl butyral (PVB) and solutions containing low fractions of CNTs from 0.5 to 2 wt.% were electrospun directly onto carbon fiber prepregs. These interlayered laminates were cured above the glass transition temperature (Tg) of PVB to achieve strong interlaminar binding and also to resist crack re-initiation. The effect of CNTs presence and their mass fractions both on total Mixed-Mode I + II fracture toughness (GC) and crack length was investigated under Mixed-Mode I + II loading. Almost 2-fold increase in GC was reported in interlayered composites compared to non-interlayered laminates, associated to toughening effect of adhesive PVB/CNTs nanofibrous interlayers. Furthermore, the post-fracture analysis revealed the aid of CNTs interleaves in retarding delamination and afterward stabilization of crack propagation

Electrically conductive high–performance thermoplastic filaments for fused filament fabrication

Conductive polyetherimide (PEI)-based filaments can fill the gap between the design and manufacturing of functional and structural components through additive manufacturing. This study systematically describes the fabrication of carbon nanotube (CNTs)-reinforced PEI filaments, complemented by a custom-built extrusion process facilitating low weight fraction of nanomaterials. Neat PEI and CNTs/PEI filaments at different CNTs fractions ranging from 0.1 to 7 wt. % were fabricated. Supported by morphology analysis, the rheological percolation was found to be higher (0.25 wt. % CNTs/PEI) than electrical percolation (0.1 wt. % CNTs/PEI) since the system reached an electrical percolation within the formation of a continuous conductive path at lower CNTs loadings. With the 7 wt. % CNTs loading, the highest electrical conductivity of CNTs/PEI filaments was reported as 2.57 × 10−1 S/cm. A 55% enhancement in tensile modulus was achieved when 5 wt. % CNTs were introduced, but in a trade-off in elongation at break ca. 65%

Habitat Preferences of Butterflies (Papilionoidea) in the Karpaz Peninsula, Cyprus

Volume: 36Start Page: 57End Page: 6

Polyacrylonitrile (PAN)/crown ether composite nanofibers for the selective adsorption of cations

In this study, we prepared electrospun polyacrylonitrile (PAN) nanofibers functionalized with dibenzo-18-crown-6 (DB18C6) crown ether and showed the potential of these fibers for the selective recovery of K+ from other both mono- and divalent ions in aqueous solutions. Nanofibers were characterized by SEM, FTIR and TGA. SEM results showed that the crown ether addition resulted in thicker nanofibers and higher mean fiber diameters, in a range of 138 to 270 nm. Batch adsorption experiments were conducted in order to evaluate the potential of the crown ether modified nanofibers as an adsorbent for ion removal. The maximum adsorption capacity of the crown ether modified nanofibers for K+ was 0.37 mmol g−1 and the nanofibers followed the selectivity sequence of K+ > Ba2+ > Na+ ∼ Li+ for single ion experiments. Adsorption of Ba2+ ions onto crown ether-modified nanofiber was examined by XPS and the results confirmed the adsorption of the ion. Mixed ion adsorption experiments revealed competitive adsorption between K+ and Ba2+ ions for the available binding sites. This effect was not observed for the other monovalent ions present in the solution and exceptionally high selectivities for K+ over Li+ and Na+ were obtained. Also the crown ether modified nanofibers exhibited good regeneration properties and a good reusability over multiple consecutive adsorption–desorption cycles. Electrospinning is thus shown to be a very versatile tool to prepare crown ether functional polymer adsorbents for the selective recovery of ions

Myocardial Work: Methodology and Clinical Applications

A precise and accurate assessment of left ventricular (LV) contractility is of utmost importance in terms of prognosis in most cardiac pathologies. Given the limitations of ejection fraction (EF) and global longitudinal strain (GLS) due to their load dependency, a novel imaging tool called myocardial work (MW) has emerged as a promising method for LV performance evaluation. MW is a novel, less load-dependent method based on computation of myocardial strain-arterial blood pressure curves. This method provides a more detailed assessment of segmental and global LV function incorporating the patient's LV pressure and is derived by brachial artery pressure utilizing an empiric reference curve adjusted to the duration of the isovolumic and ejection phases as determined by echocardiography. The clinical implications of this unique method have been expanding in the last few years, which attest to the robust additive role of MW in routine practice

Validation and cross-cultural adaptation of the Turkish version of the revised Leeds Disability Questionnaire in patients with ankylosing spondylitis

Background/aim: The revised Leeds Disability Questionnaire (RLDQ) is a unique assessment tool for patients with ankylosing spondylitis (AS); its comprehensive structure includes posture and neck flexibility parameters. The aim of the study was to determine the psychometric properties of the Turkish RLDQ in patients with AS. Materials and methods: A total of 100 AS patients were enrolled in the study. In the first evaluation, patients filled out the Dougados Functional Index (DFI) and Bath Ankylosing Spondylitis Functional Index (BASFI), Stanford Health Assessment Questionnaire (HAQ) in addition to RLDQ. Then, patients were refilled the revised RLDQ in the second assessment. Results: The mean age of the patients (40 women, 60 men) was 48.3 +/- 12.6 years. The test-retest reliability and internal consistency of the RLDQ total score were excellent. ICC score and Cronbach's alpha score were calculated as 0.853 and 0.905, respectively. The SEM and MDC values calculated for the RLDQ total score were 2.74 and 7.60, respectively. RLDQ had degrees of correlation with DFI, HAQ, and BASFI of 0.814, 0.742, and 0.852, respectively. Construct validity was excellent (r > 0.50, p < 0.01). Conclusion: The Turkish version of the RLDQ was found to be valid and reliable in patients with AS. It should be emphasized that the RLDQ is a distinctive and valuable tool that focuses separately on neck, posture, or other mobility parameters in the clinical assessment of AS

A 19-Year-Old Pregnant Woman With Pulmonary Hypertension With Progressive Dyspnea

CASE PRESENTATION: A 19-year-old pregnant woman at week 32 of gestation was referred to our clinic with progressive shortness of breath for the further evaluation and treatment of high-risk pregnancy. Her complaints had been existing since her childhood. Two years prior to her admission, she had been diagnosed with heart failure with preserved ejection fraction due to cardiomyopathy and associated pulmonary hypertension. The patient had no family history of any cardiac disease. She had never smoked or drunk alcohol. Her clinical condition had deteriorated progressively with the pregnancy