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Density functional theory (DFT) calculations are executed to investigate the effect of a potassium (K) promoter on the activity of the water gas shift reaction (WGSR) over an Ag(111) surface. It is found that the WGSR proceeds mainly through the OH(O)-assisted carboxy pathway in which H2O dehydrogenation is the rate-controlling step on both Ag(111) and K/Ag(111) surfaces. Energetic span model analysis shows that K addition can enhance the activity of the WGSR by reducing the apparent activation energy of the whole reaction since it can promote H2O dissociation and stabilize the adsorption of the reactants (CO and H2O). Importantly, the K adatom can stabilize the binding of all oxygenates by direct K–O bonding and the stabilizing effect of K on OH adsorption of the transition state (TS) plays a leading role in promoting H2O dissociation. Moreover, the K–O distance and K coverage are two key factors affecting H2O activation, that is, the shorter the K–O distance (2–3 Å) the more the K coverage (25%) contributes to the stronger promotion effect. For various metals catalyzing the WGSR, K promotes H2O dissociation on inert metals like Ag, Au and Cu better than those on reactive metals (Pd and Ni) since the more inert metal surfaces would weaken the K and O binding and accordingly strengthen the interaction between them, resulting in a higher promotion effect. [ABSTRACT FROM AUTHOR]

The reduced graphene oxide-gold nanoparticle (rGO-Au NP) membranes are prepared by vacuum filtration method. The sizes of the Au NPs on the surface of the rGO are about 8-10 nm, and the lattice spacing of Au NPs is 0.0241 nm, which is relative to the cubic lattice of the gold crystal. The layer-by-layer stacking structure of rGO-Au NP membrane can be observed clearly by field emission scanning electron microscopy. The water flux of the rGO-Au NP membrane is as high as 204.1 L m−2 h−1 bar−1, and its retention for Rhodamine B (RhB) is as high as 99.79%. [ABSTRACT FROM AUTHOR]

Graphene has promising potential in several fields because of its unique and brilliant properties, and graphene-based composites are studied for nanofiltration because of their chemical stability and thermal resistance. Nanometals are used for compositing with graphene and its derivatives, such as Ag, Au, TiO2, and Cu. Graphene-based/nanometal membranes have remarkable performance in water treatment, antibacterial properties, and so on. In this review, we introduce the separation mechanism and fabrication method of graphene-based/nanometal composite membranes and then summarize the recent developments. Therefore, additional applications of graphene-based/nanometal composite membranes can be expected, and this paper reviews the current research trends. [ABSTRACT FROM AUTHOR]

It is imperative to regulate O–H bond cleavage on metal surfaces with a pre-adsorbed K2O promoter in heterogeneous catalysis. Density functional theory (DFT) calculations have been performed to explore the adsorption and dissociation of water on K2O-pre-adsorbed transition metal surfaces (Au, Ag, Cu, Ni, Pt, Rh, Ir, Pd, Ru, Co and Fe) as compared with those on clean and K-pre-adsorbed metal surfaces. The calculation results indicate that the presence of K2O species significantly promotes water dissociation and the promoting effect depends on the adsorption strength of K2O, namely, the more strongly K2O binds to the metal surface, the less promoting effect it has on the water O–H bond cleavage. Based on geometrical and electronic analysis, the stronger promoting effect of K2O than K on water dissociation on the given metal surfaces can be attributed to stronger attractive electrostatic interactions between OH and the dissociating H of H2O at the TSs as well as between O of H2O and K of K2O at the ISs on K2O-pre-adsorbed surfaces compared with those on K-pre-covered surfaces. Moreover, the additional hydrogen bond interaction between H and Oad of K2O at the ISs on Cu/Ag/Au and Fe/Co/Ni metals would be responsible for the much greater promoting effect of K2O than K on these metal surfaces, while there is a slightly greater promoting effect of K2O on the remaining metal surfaces. From the above analysis, we expect our studies can provide profound understanding of the nature of the promoting effect of K2O on O–H bond scission. [ABSTRACT FROM AUTHOR]

Based on Cd(NO3)2·4H2O and 4,4′-((5-carboxy-1,3-phenylene)bis(oxy))dibenzoic acid (H3cpbda), two isomeric coordination polymers, {[Cd1.5(cpbda)(bpa)(H2O)2]·1.5H2O}n (1), [Cd(H2cpbda)2(bpa)0.5(H2O)]n (2), were synthesized by using different solvent-systems. The complexes were characterized by single-crystal X-ray diffraction, IR spectroscopy, powder X-ray diffraction, and thermogravimetric analysis. Owing to the obvious structural difference between the two isomeric complexes, the further fluorescence sensing and dye selection and adsorption were investigated. The 3D tight stacking structure of 1 strengthened the fluorescence emission and the loose 2D layer structure of 2 generated the active selection and adsorption of the Malachite Green Oxalate (MGO) dye. [ABSTRACT FROM AUTHOR]

Abstract: Amorphous Mg–Ni–La hydrogen-storage alloys were prepared by melt-spinning. The phase structures of the ribbons before and after charge/discharge cycling were characterized by X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) analysis, respectively. The effects of different contents of La are discussed on the basis of discharge-capacity, the morphology, limiting current density and electrochemical impedance spectra of the Mg–Ni–La electrodes. The Mg65Ni27La8 alloy exhibits the best reaction kinetics performance, the lowest contact resistance and a maximum discharge capacity of 582 mAh g−1 at room temperature. The non-isothermal dehydrogenation process of Mg65Ni27La8 alloy was analyzed in detail by differential scanning calorimetry (DSC) and thermogravimetry (TG). The experimental results showed a maximum 4.0 wt.% of released hydrogen at a heating rate of 5 °C min−1. The non-isothermal dehydrogenation process of the alloy can be divided in two steps, corresponding to the dehydrogenation of amorphous phase (1.45 wt.% H) and Mg2NiH4 (2.55 wt.% H), respectively. It indicated that the amorphous structure was a key factor to achieve high discharge capacity and good cycling stability. [Copyright &y& Elsevier]

Three types of graphene oxide/silver nanoparticles (GO/AgNPs) composite membranes were prepared to investigate size-effect of AgNPs on nanofiltration ability. The size of AgNPs was 8, 20, and 33 nm, which was characterized by UV-visible spectroscopy and transmission electron microscopy. The morphology and structure of GO and GO/AgNPs composite membranes were characterized by atomic force microscopy, scanning electron microscopy, and X-ray diffraction. The filtration performance of membranes were evaluated on a dead-end filtration device. When the size of AgNPs is 20 nm, the GO/AgNPs composite membrane has the highest water flux (106.1 L m−2 h−1 bar−1) and rejection of Rhodamine B (RhB) (97.73%) among three types of composite membranes. The effect of feed concentration of dye solution and the flux of common solvent was also investigated. The mechanism was discussed, which demonstrated that both interlaying spacing and defect size influence the filtration ability of membrane, which is instructive to future study. [ABSTRACT FROM AUTHOR]

The shortage of water resources is a problem concerned by all countries in the world. In order to solve this problem of human survival, membrane separation technology promotes the development of water treatment field by virtue of its own advantages of high efficiency and low consumption. Membrane separation technology combined with nanomaterials has brought surprises to researchers. Graphene has unique structure and properties, making graphene and its derivatives have very good potential in water treatment and selective separation. Graphene‐based materials combined with traditional polymer materials have great potential in the field of membrane separation technology. In this article, we first introduce the preparation methods and transport mechanism of graphene‐based membranes, and then summarize the recent applications of graphene oxide/polymer composite membranes in water purification, gas separation, self‐cleaning, and oil–water separation. It is expected to become the next generation of functional composite membranes. © 2019 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2019, 136, 47761. [ABSTRACT FROM AUTHOR]

In this work, graphene oxide (GO)/ethylene glycol (EG) membranes were designed by a vacuum filtration method for molecular separation and water purification. The composite membranes were characterized by scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), atomic force microscopy (AFM) and X-ray photoelectron spectroscopy (XPS). The interlayer spacing of GO membranes (0.825 nm) and GO/EG membranes (0.634 nm) are measured by X-ray diffraction (XRD). Using the vacuum filtration method, the membrane thickness can be controlled by selecting the volume of the solution from which the membrane is prepared, to achieve high water permeance and high rejection of Rhodamine B (RhB). The membrane performance was evaluated on a dead-end filtration device. The water permeance and rejection of RhB of the membranes are 103.35 L m−2 h−1 bar−1 and 94.56% (GO), 58.17 L m−2 h−1 bar−1 and 97.13% (GO/EG), respectively. The permeability of GO/EG membrane is about 40 × 10−6 L m-1 h−1 bar−1. Compared with the GO membrane, the GO/EG membrane has better separation performance because of its proper interlayer spacing. In this study, the highest rejection of RhB (99.92%) is achieved. The GO/EG membranes have potential applications in the fields of molecular separation and water purification. [ABSTRACT FROM AUTHOR]

Diabetic conditions worsen the prognosis of stroke. The molecular mechanism underlying the impairment of post-stroke recovery is not very clear. Here, we establish a rat model resembling human cerebral infarction with or without diabetes to determine how diabetes impairs cognitive recovery. Our data show that diabetes inhibits hippocampal BDNF expression and impairs the survival and differentiation of the newborn neural cells in rats with ischemia. Consequently, the rats of diabetic ischemia have a significantly lower score in spatial learning and memory in the Morris water maze test than the non-diabetic ischemia model rats. On the other hand, treatment with BDNF effectively improves hippocampal neurogenesis and the spatial learning and memory in rat with diabetic ischemia. All together, our data suggest that diabetes impaired spatial learning and memory and hippocampal neurogenesis in rats with ischemia by inhibition of the BDNF expression in the hippocampus. [ABSTRACT FROM AUTHOR]

Density functional theory (DFT) calculations are executed to investigate the effect of a potassium (K) promoter on the activity of the water gas shift reaction (WGSR) over an Ag(111) surface. It is found that the WGSR proceeds mainly through the OH(O)-assisted carboxy pathway in which H 2 O dehydrogenation is the rate-controlling step on both Ag(111) and K/Ag(111) surfaces. Energetic span model analysis shows that K addition can enhance the activity of the WGSR by reducing the apparent activation energy of the whole reaction since it can promote H 2 O dissociation and stabilize the adsorption of the reactants (CO and H 2 O). Importantly, the K adatom can stabilize the binding of all oxygenates by direct K-O bonding and the stabilizing effect of K on OH adsorption of the transition state (TS) plays a leading role in promoting H 2 O dissociation. Moreover, the K-O distance and K coverage are two key factors affecting H 2 O activation, that is, the shorter the K-O distance (2-3 Å) the more the K coverage (25%) contributes to the stronger promotion effect. For various metals catalyzing the WGSR, K promotes H 2 O dissociation on inert metals like Ag, Au and Cu better than those on reactive metals (Pd and Ni) since the more inert metal surfaces would weaken the K and O binding and accordingly strengthen the interaction between them, resulting in a higher promotion effect.

Background: Gastrointestinal dysfunction is one of the complications after stroke. If it is not treated in time, it will affect the rehabilitation process after stroke and reduce the quality of life of patients. In this study, we conducted a systematic review and meta-analysis of the reports on the treatment of gastrointestinal dysfunction after stroke with traditional Chinese medicine (TCM) in recent years to provide evidence for clinical diagnosis and treatment., Methods: The clinical randomized controlled trials (RCTs) published in Chinese Biomedical Literature Database (CBM), China National Knowledge Infrastructure (CNKI), Medline, and Web of Science databases from January 2010 to August 2021 were searched. After screening the qualified literatures, literature quality evaluation was performed. The software Stata 16.0 was used to analyze and compare the outcome indicators of TCM and conventional western medicine treatment, and the utility of TCM in the treatment of gastrointestinal disorders after stroke was comprehensively evaluated., Results: A total of 16 studies were finally selected including a total of 1,589. Meta-analysis showed that TCM treatment of gastrointestinal disorders after stroke was more effective than conventional western medicine treatment [odds ratio (OR) =3.94; 95% confidence interval (CI): 2.63 to 5.89; P=0.000]. It was also shown that TCM can reduce the recovery time of bowel sounds and is superior to conventional western medicine [standard mean difference (SMD) =-1.92; 95% CI: -2.51 to -1.34; P=0.000]; reduce defecation and flatulence recovery time (SMD =-2.51; 95% CI: -3.41 to -1.61; P=0.000); increase gastrin level (SMD =0.80; 95% CI: 0.35 to 1.25; P=0.001); increase motilin level (SMD =2.27; 95% CI: 1.55 to 3.00; P=0.000); increase serum albumin level (SMD =0.72; 95% CI: 0.54 to 0.90; P=0.000); increase transferrin levels (SMD =1.11; 95% CI: 0.86 to 1.36; P=0.000); and it can increase serum prealbumin levels (SMD =1.50; 95% CI: 0.78 to 2.22; P=0.000)., Discussion: The use of TCM in the treatment of gastrointestinal dysfunction after stroke can effectively reduce symptoms, shorten the recovery time of bowel sounds, the first defecation and flatulence time, promote gastric motility and gastrointestinal hormone secretion, and improve the nutritional status of patients.

It is imperative to regulate O-H bond cleavage on metal surfaces with a pre-adsorbed K2O promoter in heterogeneous catalysis. Density functional theory (DFT) calculations have been performed to explore the adsorption and dissociation of water on K2O-pre-adsorbed transition metal surfaces (Au, Ag, Cu, Ni, Pt, Rh, Ir, Pd, Ru, Co and Fe) as compared with those on clean and K-pre-adsorbed metal surfaces. The calculation results indicate that the presence of K2O species significantly promotes water dissociation and the promoting effect depends on the adsorption strength of K2O, namely, the more strongly K2O binds to the metal surface, the less promoting effect it has on the water O-H bond cleavage. Based on geometrical and electronic analysis, the stronger promoting effect of K2O than K on water dissociation on the given metal surfaces can be attributed to stronger attractive electrostatic interactions between OH and the dissociating H of H2O at the TSs as well as between O of H2O and K of K2O at the ISs on K2O-pre-adsorbed surfaces compared with those on K-pre-covered surfaces. Moreover, the additional hydrogen bond interaction between H and Oad of K2O at the ISs on Cu/Ag/Au and Fe/Co/Ni metals would be responsible for the much greater promoting effect of K2O than K on these metal surfaces, while there is a slightly greater promoting effect of K2O on the remaining metal surfaces. From the above analysis, we expect our studies can provide profound understanding of the nature of the promoting effect of K2O on O-H bond scission.

Chitinase ChiEn1 did not hydrolyze insoluble chitin but showed hydrolysis and transglycosylation activities toward chitin-oligosaccharides. Interestingly, the addition of ChiEn1 increased the amount of reducing sugars released from chitin powder by endochitinase ChiIII by 105.0%, and among the released reducing sugars the amount of (GlcNAc) 2 was increased by 149.5%, whereas the amount of GlcNAc was decreased by 10.3%. The percentage of GlcNAc in the products of chitin powder with the combined ChiIII and ChiEn1 was close to that in the products of chitin-oligosaccharides with ChiEn1, rather than that with ChiIII. These results indicate that chitin polymers are first degraded into chitin oligosaccharides by ChiIII and the latter are further degraded to monomers and dimers by ChiEn1, and the synergistic action of ChiEn1 and ChiIII is involved in the efficient degradation of chitin in cell walls during pileus autolysis. The structure modeling explores the molecular base of ChiEn1 action.

MnO2 with urchin-like nano/micro hierarchical architecture was synthesized through an easy hydrothermal method at low temperature and used to prepare MnO2/graphene hybrid composite as electrode materials through an easy and efficient solution-based method. The MnO2 particles in the composite with 66.7% mass ratio could achieve specific capacitance as high as 451.5 F g(-1) at a scan rate of 10 mV s(-1) and exhibit good cycle stability with 93.8% capacitance retention over 2000 cycles. These properties result from the unique urchin-like nano/micro hierarchical structure of MnO2 as well as the function of graphene in enhancing the conductivity and utilization of MnO2.