Search

Summary: The Fanconi anemia (FA) pathway is critically involved in the maintenance of hematopoietic stem cells and the suppression of carcinogenesis. A key FA protein, FANCD2, is monoubiquitinated and accumulates in chromatin in response to DNA interstrand crosslinks (ICLs), where it coordinates DNA repair through mechanisms that are still poorly understood. Here, we report that CtIP protein directly interacts with FANCD2. A region spanning amino acids 166 to 273 of CtIP and monoubiquitination of FANCD2 are both essential for the FANCD2-CtIP interaction and mitomycin C (MMC)-induced CtIP foci. Remarkably, both FANCD2 and CtIP are critical for MMC-induced RPA2 hyperphosphorylation, an event that accompanies end resection of double-strand breaks. Collectively, our results reveal a role of monoubiquitinated FANCD2 in end resection that depends on its binding to CtIP during ICL repair. [Copyright &y& Elsevier]

• This study offers a sustainable method for separating and recycling oil-water streams using recycled PET. • A PDMS-modified rPET fibrous membrane was successfully fabricated using electrospinning and dip-coating methods. • PDMS-functionalized rPET fibrous membranes showed high water intrusion pressure and excellent anti-water-fouling properties. • The resulting membrane exhibited high oil-water separation performance. In recent years, low-cost and effective technologies for oil-water separation have been highly desired due to an increase of oily wastewater and frequent oil spill accidents. This study demonstrates a cost-effective and sustainable preparation of flexible fibrous membranes with high oil-water separation performance using recycled polyethylene terephthalate (rPET). The rPET fibrous membrane was prepared via electrospinning; in the following step, the rPET membrane was dip-coated with polydimethylsiloxane (PDMS) to improve the water intrusion pressure and anti-water-fouling property of the rPET fibrous membrane. The effect of PDMS concentration on the membrane morphology, surface chemistry, thermal and mechanical properties, surface wettability and oil-water separation performance was evaluated. The membranes are superoleophilic with an oil contact angle of 0° and exhibit excellent anti-water-fouling properties. The PDMS-functionalized rPET membranes can effectively separate various oil-water mixtures driven by gravity, with a high flux (∼ 20,000 L m−2 h-1) and a high separation efficiency (> 98 %) for up to ten cycles and thus has potential industrial application. [ABSTRACT FROM AUTHOR]

Abstract: Biodegradable elastomeric network poly(ester-carbonate)s were prepared from multifunctional aliphatic carboxylic acids such as tricarballylic acid (Yt) or trimesic acid (Y) and polycarbonate diols (PCD) with molecular weights of 1000 and 2000g/mol. Prepolymers prepared by a melt polycondensation were cast from dimethylformamide solution and postpolymerized at 270°C for 40–80min to form a network. The resultant films were transparent, flexible and insoluble in organic solvents. WAXS exhibited the crystalline peaks due to polycarbonate segments for the network films from PCD2000, while those from PCD1000 were amorphous. The tensile properties were determined for these network films at the temperatures 22, 30, 40 and 50°C. These films showed elastomeric properties at all temperatures measured. The elongation at break was much higher for the films from PCD2000 (208–434%) than those from PCD1000 (40–120%), and decreased with increasing temperatures. The weight losses of the network films degraded in the buffer solution of Rhizopus delemar lipase at 37°C increased with time, suggesting that these network films are biodegradable. The degradation rate of the network films from Yt is faster than that from Y. The GPC curves showed that the lipase hydrolyzed both the ester linkages between Y or Yt and PCD as well as polycarbonate moiety in the network polymer. [Copyright &y& Elsevier]

Abstract: Thin and ultrathin films of copolymer of 83% mole fraction vinylidene fluoride and 17% mole fraction trifluoroethylene were prepared using a spin-coating technique. Atomic force microscopy results showed that spun films formed tiny grains on the surface. A micro-thermal analyzer showed that tiny grains had a ferroelectric Curie transition at 128.8 °C and melted at 140.7 °C. The crystallinity of the film was measured to be ca. 40% by an X-ray diffraction for the film with thickness above 170 nm. Crystallinity decreased quickly with decreasing thickness. The crystallinity was at most 5% for the film with thickness below 75 nm. We found the ferroelectric polarization reversal effect strongly depended on the film thickness. Clear polarization reversal due to a switching of ferroelectric dipoles was observed for the film with thickness above 90 nm and broad ferroelectric reversal was obtained for the film with thickness below 90 nm. For the films with thickness above 100 nm, the remnant polarizations were almost constant and the coercive fields were significantly decreased with decreasing film thickness. [Copyright &y& Elsevier]

Spin-trapping electron spin resonance (ESR) and gel permeation chromatography (GPC) were applied to analyze the thermal degradation mechanisms of poly(vinyl alcohol) (PVA). The lifetime of the short-lived radical intermediate produced by thermal degradation at up to 200 °C was extended via the spin-trapping method for the purpose of investigating its molecular structure. Under the addition of the spin-trapping reagents dimethyl-1-pyrroline- N -oxide (DMPO) or 3,5-dibromo-4-nitrosobenzenesulfonate (DBNBS), into the PVA, the production of some radical intermediates, including hydroxyl (•OH) and some main chain radicals (–CH=CH–•CH– and •CH(OH)–CH 2 –), was confirmed via simulation analysis of the observed ESR spectra. The GPC measurement revealed that the cross-linking reaction occurred more often at temperatures above 100 °C and that the main chain scission also occurs significantly at around 200 °C. The elimination of •OH is therefore a key reaction in PVA degradation, and •CH(OH)–CH 2 – is produced by the β-scission from the main chain radical –CH 2 –•C(OH)–CH 2 –. This last radical was not observed in the present study; however, it should be produced through a hydrogen abstraction by •OH. Image 1 • The thermal degradation mechanisms of PVA was investigated using spin-trapping method of ESR and GPC. • Three intermediate radicals, •OH, –CH=CH–•CH–CH 2 –, and •CH(OH)–CH 2 –, were detected above 100 ℃ by the spin-trapping. • The amounts of the spin adduct derived from these radials increased above 160 ℃ dramatically. • •OH is a key factor in the thermal degradation of PVA. • The cross-linking dominantly occurs above 100 °C and the main chain scission also proceeds significantly at around 200 °C. [ABSTRACT FROM AUTHOR]

Abstract An electron spin resonance (ESR) spectroscopy as well as a photoelectron yield spectroscopy (PYS) is used to study the photocarrier behavior (generation and transport) for photorefractivity in poly(N -vinyl carbazole) (PVCz) and poly[bis(2,4,6-trimethylphenyl)amine] (PTAA) based photorefractive (PR) polymer composites. ESR spectra directly catch the radical species in PR composites on the laser illumination under applied electric field; the cation radicals and anion radicals induced under light illumination upon applying an electric field were evaluated. PYS was used to evaluate the energy levels and the width of the electron density of states (DOS) of the carrier transport manifolds. The narrower DOS width of the PTAA-based PR composite was significantly related to the faster response time and broader DOS width for the PVCz-based PR composite to the slower response time. Based on all these results, the comprehensive energy diagrams, including perspectives on the energy level and its distribution, the generated charge carriers with spins, and occupied trap density, are proposed. Graphical abstract Image 10130 Highlights • Photorefractive dynamics are studied using ESR and PYS with common PR measurements. • Number of polymer cations, 2.4–3.1 × 1016 cm−3, was evaluated from ESR signal. • Mobility is 1.07 × 10−6 and 1.15 × 10−8 cm2 V−1 s−1 for respective PTAA and PVCz PR polymers. • Faster response is due to narrower DOS width with higher mobility for PTAA PR polymer. • Slower response is due to broader DOS width with lower mobility for PVCz PR polymer. [ABSTRACT FROM AUTHOR]

• The initiation reactions on thermo-oxidative degradation of Polyamide 66 under air was investigated using spin-trapping electron spin resonance (ST-ESR). • GPC analysis shows a large degradation by main chain scission when heated up to 240°C. • ST-ESR analysis has newly revealed the presence of two more radical intermediates, −•CH−NH− and •(C=O)NH−, under air, in addition to the two radical intermediates, •CH 2 − and −CH 2 −•CH−CH 2 −, already found under vacuum in the previous report. • The generating temperature of −•CH−NH− coincides with the onset temperature of the large chemiluminescence (CL) by oxidation reaction. • The initial radical of thermo-oxidative degradation of PA66 is determined as −•CH−NH− radical generated by selective oxygen attack on the NH-adjacent methylene group. • The ST-ESR analysis reveals more small levels of reaction than other analytical methods. We succeeded in detecting the radical intermediates produced during the thermo-oxidative degradation of polyamide 66 (PA66) in air between 80°C to 240°C, the temperature range for practical applications, using spin-trapping electron spin resonance (ST-ESR) even in the presence of oxygen, which interferes with ESR measurements. As a result, ST-ESR analysis has newly revealed the presence of two more radical intermediates, −•CH−NH− and •(C=O)NH−, under air in addition to the two radical intermediates, •CH 2 − and −CH 2 −•CH−CH 2 −, already found in the previous report, which was examined under oxygen-free conditions. The formation of those four radicals can be explained by hydrogen abstraction and β-scission in the autoxidation mechanism. The onset temperature of the rapid oxidation reaction observed in chemiluminescence (CL) measurement coincides with the one for generating the −•CH−NH− radical, indicating that the initial radical of thermo-oxidative degradation of PA66 is −•CH−NH− radical generated by selective oxygen attack on the NH-adjacent methylene group. This finding strongly supports previous reports that concluded hydrogen abstraction from the NH-adjacent methylene group is the main reaction under air. [Display omitted] [ABSTRACT FROM AUTHOR]

The effects of dyeing carriers on the color strength ( K / S values) of poly( l -lactic acid) (PLLA) fibers were investigated, using the photochromic dye 1′,3′,3′-trimethyl-6-nitro-spiro(2 H -1-benzopyran-2,2′-indole) (6-nitro BIPS). Both an organic solution (based on tetrachloroethylene) and an aqueous dispersion of the dye were applied to the PLLA fibers, and the resulting change in color of the PLLA samples irradiated by ultraviolet (UV) light was evaluated by spectrocolorimetry. In the case of aqueous dispersion processing, the uptake of 6-nitro BIPS on the PLLA fibers was expected to be increased when using o -phenylphenol as a carrier. The value was four times higher than that obtained using the organic solution. The energy diagrams associated with the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of the 6-niro BIPS for the two dyeing processes were determined using photoelectron yield spectroscopy. [ABSTRACT FROM AUTHOR]

[Display omitted] • A facile and scalable preparation method of flexible polyimide fibrous thermal insulator was demonstrated. • The polymer concentration and solvent composition were optimized in order to fabricate fine fiber. • The cross-linked fibers exhibit better solvent stability compared to non-crosslink fibers. • The PI fibrous insulator shows low thermal conductivity and excellent flexibility at high temperature. Flexible fibrous thermal insulators with low thermal conductivity are highly demanded to improve energy efficiency in many application fields, especially in the aerospace industry. In the present study, the cross-linked porous polyimide (PI) fibrous insulator was prepared using centrifugal spinning, a scalable and facile technique for fibers production. The influence of PI concentration and solvent composition was evaluated to find the optimum parameters for defect-free fiber fabrication. In the following step, the PI fibers were cross-linked to gain better solvent stability. The morphology, chemical properties, surface wettability, thermal resistance, and thermal conductivity of the obtained fibers were evaluated. The cross-linked fibers exhibit a low thermal conductivity of 0.029 W/mK with thermal stability up to 515 °C, hydrophobicity with a contact angle of 137.7°, and are flexible at high temperature. The successful fabrication of the PI fibers opens a new approach for the scalable fabrication of flexible fibrous insulators for aerospace applications. [ABSTRACT FROM AUTHOR]

An X-ray dosimeter is a device that detects and quantifies X-ray radiation. There is demand for a useful dosimeter with high sensitivity that works independently, has a low cost, and can be mass produced. In this study, a 10,12-pentacosadiynoic acid (PCDA)-based composite fibrous color dosimeter (CFCD) is developed for X-ray visualization and quantification on the order of a few grays (Gy). This CFCD is successfully prepared from PCDA and polylactic acid (PLA) using the centrifugal spinning (CS) method. The CFCD undergoes a color transition from white to deep blue with X-ray exposure in the range from 2.2 to 40 Gy. This color change is attributed to the polymerization process of PCDA. The prepared CFCD is a useful device for the detection and quantification of X-rays, exhibiting a maximum sensitivity of 2.2 Gy due to PCDA. • The composite fiber color dosimeters (CFCD) have a color change from white to blue under X-ray, which recognize by eyes. • The centrifugal spinning method has high productivity. • The sensitivity of CFCD in ranges from 2.2 to 40 Gy. • This CFCD is expected to be able to replace traditional dosimeters in several emergency cases. [ABSTRACT FROM AUTHOR]

In this study, Response Surface Methodology based on four-factor Box-Behnken design was applied to suggest the optimal conditions for glycolysis of polyethylene terephthalate (PET) and to analyze the individual and interaction effects of the factors on the process. Four independent factors of interest, namely reaction time (3–5 h), reaction temperature (192–200 °C), mass ratio of ethylene glycol (EG) to PET (2.5–7.5), and mass ratio of sodium bicarbonate (NaHCO 3) to PET (0.6–1.0%), were under consideration for their catalyst effect on the process. A regression model as a mathematical function of the four factors was obtained to predict the yield of bis(2-hydroxyethyl) terephthalate (BHET) yield and its reliability was evaluated by analysis of variance. A remarkably high yield of 75.7% was obtained with 1.3% error from the predicted value at the optimal operating conditions for temperature, time, EG:PET mass ratio, and NaHCO 3 :PET mass ratio of 192 °C, 3.02 h, 6.09 and 0.82%, respectively. The experimental results and analysis of response surfaces revealed that an inappropriately large amount of catalyst might restrict monomer conversion under excess EG conditions. Moreover, PET glycolysis process could be carried out under lower temperature and shorter time due to the profound effect of excess EG at a suitable concentration level of NaHCO 3. This suggested future in-depth analysis with wider parameter space to optimize PET glycolysis under conditions of large amount of EG and to gain insight into the interaction effect between EG amount and catalyst concentration. • An optimal amount of EG could facilitate monomer conversion at a sufficient concentration level of NaHCO 3 catalyst. • Under excess EG conditions, an inappropriately large amount of NaHCO 3 might restrict monomer conversion. • Appreciable BHET yield was obtained at low reaction temperature and short reaction time at the cost of excess EG. • Prolonged glycolysis at lower reaction temperature might reduce BHET yield if large amount of EG had been provided. [ABSTRACT FROM AUTHOR]