Search

Understanding the polymer solubility in ionic liquids (ILs) is important for polymer processing or polymeric material preparation. Previously, two-parameter H-bonding analysis has been proposed to clarify that polymer solubility in ILs is dominated by H-bonding interactions (Y. F. Yuan et al., Phys. Chem. Chem. Phys., 2021, 23, 21893–21900). In the present work, 1H-NMR spectra are adopted to characterize the H-bonding interactions between polymers and ILs, which provide a microscopic relation between polymer solubility and two-parameter H-bonding analysis. [ABSTRACT FROM AUTHOR]

Solar desalination is a promising strategy to utilize solar energy to purify saline water. However, the accumulation of salt on the solar evaporator surface severely reduces light absorption and evaporation performance. Herein, a simple and eco‐friendly method to fabricate a 3D gradient graphene spiral sponge (GGS sponge) is presented that enables high‐rate solar evaporation and zero liquid discharge (ZLD) desalination of high‐salinity brine. The spiral structure of the GGS sponge enhances energy recovery, while the gradient network structures facilitate radial brine transport and directional salt crystallization, which cooperate to endow the sponge with superior solar evaporation (6.5 kg m−2 h−1 for 20 wt.% brine), efficient salt collection (1.5 kg m−2 h−1 for 20 wt.% brine), ZLD desalination, and long‐term durability (continuous 144 h in 20 wt.% brine). Moreover, the GGS sponge shows an ultrahigh freshwater production rate of 3.1 kg m−2 h−1 during the outdoor desalination tests. A continuous desalination–irrigation system based on the GGS sponge for crop growth, which has the potential for self‐sustainable agriculture in remote areas is demonstrated. This work introduces a novel evaporator design and also provides insight into the structural principles for designing next‐generation solar desalination devices that are salt‐tolerant and highly efficient. [ABSTRACT FROM AUTHOR]

Global climate change has posed widespread challenges to the ecological process critical to the fitness of many wild organisms, such as reproductive phenology. Many bird species have advanced their reproductive phenology in response to the increases in spring temperatures. However, the mechanism of how climate influences the timing of breeding is still often unclear in many species. We explored the relationship between the timing of breeding and spring temperatures based on 14 years of data on hair‐crested drongos Dicrurus hottentottus in the wild. By applying a 'sliding window' approach, we aimed to identify the time window and weather variable that best explains the timing of breeding at both population and individual levels. We found that the more nights with a minimum temperature below 17°C, around three weeks earlier than the peak reproduction, delayed the breeding time. Low night temperatures may force females to allocate more energy to thermoregulation and therefore physiologically constrain egg‐laying. Although annual minimum and maximum temperatures have increased over the study period, the timing of breeding showed no trend as there was no change in the number of low‐temperature nights in the relevant period across years. The repeatability of the laying date for individual females (R = 0.211) and across the years (R = 0.270) were low indicating that drongos were flexible in adjusting their breeding phenology to environmental variation. These results suggest an effect of low night temperature on avian breeding phenology. This effect may apply commonly across bird species considering shared physiological constraints. [ABSTRACT FROM AUTHOR]

Superelastic, arbitrary‐shaped, and 3D assembled clay/graphene aerogels (CGAs) are fabricated using commercial foam as sacrificial skeleton. The CGAs possess superelasticity under compressive strain of 95% and compressive stress of 0.09–0.23 MPa. The use of clay as skeletal support significantly reduces the use of graphene by 50%. The hydrophobic CGAs show high solvent absorption capacity of 186–519 times its own weight. Moreover, both the compression and combustion methods can be adopted for reusing the CGAs. In particular, it is demonstrated a design of 3D assembled hydrophilic CGA equipped with salt collection system for continuous solar desalination. Due to energy recovery and brine transport management promoted by this design, the 3D assembled CGA system exhibits an extremely high evaporation rate of 4.11 kg m−2 h−1 and excellent salt‐resistant property without salt precipitation even in 20 wt% brine for continuous 36 h illumination (1 kW m−2), which is the best reported result from the solar desalination devices. More importantly, salts can be collected conveniently by squeezing and drying the solution out of the salt collection system. The work provides new insights into the design of 3D assembled CGAs and advances their applications in continuous solar desalination and efficient oil/organic solvent adsorption. [ABSTRACT FROM AUTHOR]

Objective: To investigate the expression of serum transforming growth factor β2(TGF-β2) and galectin-2 (Galectin-2) in patients with atrial fibrillation and its clinical significance. Methods: A total of 150 inpatients in the Department of Cardiology of the First Affiliated Hospital of Bengbu Medical College from January 2019 to June 2019 were selected, including 84 patients in the paroxysmal atrial fibrillation group, 66 patients in the persistent atrial fibrillation group, and 120 patients with sinus rhythm excluding atrial fibrillation who were hospitalized during the same period were selected as the control group. Blood routine, biochemical routine and cardiac ultrasonic morphological examination were improved after admission. In addition, the serum levels of TGF-β2 and Galectin-2 in each group were detected by Elisa and Western Blot, and the differences and clinical significance of TGF-β2 and Galectin-2 in different groups were statistically analyzed. The correlation between TGF-β2, Galectin-2 and left atrial end-diastolic diameter (LAD) was further determined by Pearson correlation analysis. By means of binary logistics regression analysis, the factors affecting atrial fibrillation were obtained. Results: Compared with the control group, age and LAD in atrial fibrillation group were significantly increased (P<0.05). The serum concentrations of TGF-β2 and galectin-2 in persistent af group were significantly increased compared with those in paroxysmal af group and control group (P<0.05), while those in control group were significantly decreased compared with paroxysmal AF group (P<0.05). Pearson correlation analysis showed that TGF-β2 and Galectin-2 concentrations were significantly positively correlated with LAD size in the experimental group (P<0.05). Binary logistic regression analysis showed that TGF-β2, galectin-2 and LAD were risk factors for atrial fibrillation (P<0.05). Conclusion: TGF-β2 and Galectin-2 are closely related to the occurrence and development of atrial fibrillation. Both TGF-β2 and Galectin-2 were positively correlated with LAD. The three have a synergistic effect on the occurrence and progression of atrial inflammatory fibrosis in patients with ATRIAL fibrillation, jointly promoting mechanical and electrical remodeling of atrial, and can be used as risk factors to evaluate the occurrence and progression of atrial fibrillation. [ABSTRACT FROM AUTHOR]

In this paper, AlN films grown by magnetron sputtering method have been proposed as the gate insulator layer of AlGaN/GaN high electron mobility transistors (HEMTs) to decrease gate leakage current and suppress the interface trap. The effect of the temperature of substrate on the quality of AlN films have been investigated. By inserting the thin AlN film (35 nm) as a gate insulator layer, the on-state resistance of AlGaN/GaN HEMTs decrease from 11.1 Ω mm to 10.3 Ω mm @ V g = 0 V, the current collapse decreases from 16.6% to 3.2%, the gate leakage can be reduced from 1.2 Ă— 10âˆ'1A mmâˆ'1 to 4.4 Ă— 10âˆ'6A mmâˆ'1 @ V g = 2 V by five orders of magnitude, and the fast interface states disappear and the normal trap density decreases from 0.96â€"1.3 Ă— 1013 cmâˆ'2eVâˆ'1 to 1.3â€"3.4 Ă— 1012 cmâˆ'2 eVâˆ'1, proving that magnetron-sputtered AlN is an effective way to improve the performance of GaN HEMTs. [ABSTRACT FROM AUTHOR]

Xylitol is a salutary sugar substitute that has been widely used in the food, pharmaceutical, and chemical industries. Co‐fermentation of xylose and glucose by metabolically engineered cell factories is a promising alternative to chemical hydrogenation of xylose for commercial production of xylitol. Here, we engineered a mutant of SecY protein‐translocation channel (SecY [ΔP]) in xylitol‐producing Escherichia coli JM109 (DE3) as a passageway for xylose uptake. It was found that SecY (ΔP) channel could rapidly transport xylose without being interfered by XylB‐catalyzed synthesis of xylitol‐phosphate, which is impossible for native XylFGH and XylE transporters. More importantly, with the coaction of SecY (ΔP) channel and carbon catabolite repression (CCR), the flux of xylose to the pentose phosphate (PP) pathway and the xylitol synthesis pathway in E. coli could be automatically controlled in response to glucose, thereby ensuring that the mutant cells were able to fully utilize sugars with high xylitol yields. The E. coli cell factory developed in this study has been proven to be applicable to a broad range of xylose‐glucose mixtures, which is conducive to simplifying the mixed‐sugar fermentation process for efficient and economical production of xylitol. [ABSTRACT FROM AUTHOR]

Polymer solubility in ionic liquids (ILs) cannot be predicted by the solubility parameter approach based on the "like dissolves like" principle. According to the Kamlet–Abraham–Taft (KAT) multi-parameter polarity scale, ILs can be categorized on the basis of hydrogen-bond acidity or basicity ones. The experimental observations, that acidic ILs easily dissolve basic polymers and basic ILs dissolve acidic polymers, reflect the complementary nature of hydrogen-bonding interactions. A quantitative hydrogen-bonding analysis is proposed for predicting the solubility by taking the product of ΔαΔβ as an indicator of the competition between cross-association and self-association hydrogen bonding (H-bonding), where Δα is the difference of acidity parameters between the polymer and IL, and Δβ is the difference of basicity. This solubility criterion has been validated by the solubility data of 19 polymers (11 acidic and 8 basic) in 11 ILs (7 acidic and 4 basic). These principles based on KAT parameters can be applied to other systems dominated by hydrogen bonding. [ABSTRACT FROM AUTHOR]

Solar‐driven vapor generation is one of the most promising techniques for seawater desalination, which has attracted broad attention. However, a significant challenge remains for achieving a low‐cost and easy‐to‐manufacture solar‐driven steam generation device with higher evaporation efficiency, excellent mechanical performance, and good durability. Herein, a simple and cost‐effective method is developed to prepare graphene/cellulose nanocrystals (CNCs) lamella network (GCLN) with melamine foam (MF) as the skeleton. Due to the excellent light absorption properties of graphene and excellent hydrophilic properties of CNCs, GCLN exhibits an evaporation rate of 1.66 kg m−2 h−1 and an evaporation efficiency of 97.5% under 1 kW m−2 of solar radiation. In addition, GCLN can maintain its structural stability and evaporation performance during a series of harsh condition and durability tests. Due to the excellent processability of MF, the 3D‐shaped GCLN can be easily designed for an enhanced evaporation rate of 1.59 kg m−2 h−1, which is better than the theoretical limit of the evaporation rate. The novel design presented in this work offers a new avenue to develop solar steam generation devices for low‐cost and large‐scale seawater desalination under natural sunlight conditions, which is especially attractive for the urgent fresh water supply in remote areas. [ABSTRACT FROM AUTHOR]

Test methods including OM, SEM, TEM, DSC, SAXS, WAXS, and IR were used to characterise supra-molecular structure in three batches of polyethylene (PE), which had weight-average relative molar masses M ¯ w ${\overline{M}}_{\text{w}}$ of approximately 0.6 × 106, 5 × 106, and 9 × 106. They were applied to compression mouldings made by the polymer manufacturer. Electron microscopy showed that powders formed in the polymerization reactor consisted of irregularly shaped grains between 50 and 250 μm in diameter. Higher magnification revealed that each grain was an aggregate, composed of particles between 0.4 and 0.8 μm in diameter, which were connected by long, thin fibrils. In compression mouldings, lamellar thicknesses ranged from 7 to 23 nm. Crystallinity varied between 70 and 75 % in reactor powder, but was lower in compression mouldings. Melting peak temperatures ranged from 138 to 145 °C, depending on processing history. DMTA showed that the glass transition temperature θg was −120 °C for all three grades of polyethylene. IR spectroscopy found negligibly small levels of oxidation and thermal degradation in mouldings. Optical microscopy revealed the presence of visible fusion defects at grain boundaries. It is concluded that relatively weak defects can be characterized using optical microscopy, but there is a need for improved methods that can detect less obvious fusion defects. [ABSTRACT FROM AUTHOR]

Three grades of polyethylene, with weight-average relative molar masses, M ‾ W ${\bar{M}}_{\text{W}}$ , of approximately 0.6 × 106, 5 × 106, and 9 × 106, were supplied as compression mouldings by a leading manufacturer of ultra-high molecular weight polyethylene (UHMWPE). They were code-named PE06, PE5, and PE9, respectively. Specimens cut from these mouldings were subjected to a wide range of mechanical tests at 23 °C. In tensile tests, deformation was initially elastic and dominated by crystallinity, which was highest in PE06. Beyond the yield point, entanglement density became the dominant factor, and at 40 % strain, the rising stress–strain curves for PE5 and PE9 crossed the falling PE06 curve. Fracture occurred at strains above 150 %. Differences in stress–strain behaviour between PE5 and PE9 were relatively small. A similar pattern of behaviour was observed in wear tests; wear resistance showed a marked increase when M ‾ W ${\bar{M}}_{\text{W}}$ was raised from 0.6 × 106 to 5 × 106, but there was no further increase when it was raised to 9 × 106. It is concluded that the unexpected similarity in behaviour between PE5 and PE9 was due to incomplete consolidation during moulding, which led to deficiencies in entanglement at grain boundaries; they were clearly visible on the surfaces of both tensile and wear specimens. Fatigue crack growth in 10 mm thick specimens was so severely affected by inadequate consolidation that it forms the basis for a separate report – Part 4 in this series. [ABSTRACT FROM AUTHOR]

Fatigue tests were carried out on compression mouldings supplied by a leading polymer manufacturer. They were made from three batches of ultra-high molecular weight polyethylene (UHMWPE) with weight-average relative molar masses, M ¯ W ${\overline{M}}_{\mathrm{W}}$ , of about 0.6 × 106, 5 × 106 and 9 × 106. In 10 mm thick compact tension specimens, crack propagation was so erratic that it was impossible to follow standard procedure, where crack-tip stress intensity amplitude, ΔK, is raised incrementally, and the resulting crack propagation rate, da/dN, increases, following the Paris equation, where a is crack length and N is number of cycles. Instead, most of the tests were conducted at fixed high values of ΔK. Typically, da/dN then started at a high level, but decreased irregularly during the test. Micrographs of fracture surfaces showed that crack propagation was sporadic in these specimens. In one test, at ΔK = 2.3 MPa m0.5, there were crack-arrest marks at intervals Δa of about 2 μm, while the number of cycles between individual growth steps increased from 1 to more than 1000 and the fracture surface showed increasing evidence of plastic deformation. It is concluded that sporadic crack propagation was caused by energy-dissipating crazing, which was initiated close to the crack tip under plane strain conditions in mouldings that were not fully consolidated. By contrast, fatigue crack propagation in 4 mm thick specimens followed the Paris equation approximately. The results from all four reports on this project are reviewed, and the possibility of using fatigue testing as a quality assurance procedure for melt-processed UHMWPE is discussed. [ABSTRACT FROM AUTHOR]

The aim of this project was to study the efficacy of current methods of quality control and quality assurance for ultra-high molecular weight polyethylene (UHMWPE) products, and find improvements where possible. Intrinsic viscosity (IV) tests were performed on three grades of polyethylene with weight average relative molar masses M ̅ $̅{M}$ w of about 6 × 105, 5.0 × 106 and 9.0 × 106. Results from three laboratories showed substantial scatter, probably because different methods were used to make and test solutions. Tensile tests were carried out to 600 % extension at 150 °C under both constant applied load and constant Hencky strain rate, on compression mouldings made by a leading manufacturer of ultra-high molecular weight polyethylene. They gave low values of M ̅ $̅{M}$ w, suggesting incomplete entanglement at 'grain boundaries' between powder particles. Results from conventional melt-rheology tests are presented, and their relevance to quality control and assurance is discussed. Attempts to calculate molecular weights from these data met with limited success because of extended relaxation times. Suggestions are made for improving international standards for IV testing of UHMWPE, by investigating the various factors that can cause significant errors, and by introducing methods for checking the homogeneity (and hence validity) of the solutions tested. Part 2 addresses characterization of crystallinity and structure. Part 3 covers mechanical properties, and Part 4 focuses on the sporadic crack propagation behaviour exhibited by all three grades of UHMWPE in fatigue tests on 10 mm thick compact tension specimens. [ABSTRACT FROM AUTHOR]

To improve the photocatalytic activity of TiO2 film, Ti substrates are irradiated by He ions with different incident ion energy, temperature, and fluence. Anatase TiO2 films are then coated on the plasma-irradiated substrates via chemical vapor deposition followed by calcination. Photocurrent tests and photocatalytic oxidation (PCO) of formaldehyde are used to assess photocatalytic performance. The optimal plasma-irradiated samples showed a four times higher photocurrent and a three fold increase in the rate constant of the PCO reaction compared to the TiO2 coated, untreated control sample. It is found that the enhanced photocatalytic activity and photocurrent are related to the changes of Ti crystal structure and surface morphology through plasma irradiation. [ABSTRACT FROM AUTHOR]