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One-dimensional NiSe2 /CdS nanocomposites (NCs), with NiSe2 nanoparticles (NPs) integrated onto the surface of CdS nanowires (NWs) were designed and fabricated through a two-step in situ solvothermal method. Density functional theory (DFT) calculations showed that NiSe2 plays an important role in enhancing photocatalystic hydrogen (H2 ) production when coupled with CdS catalyst, which arises from 1) the contribution of Ni 3d and Se 4p orbitals to the electronic structures and 2) the charge redistribution at the interface region of the heterostructure results in efficient promotion of the charge transfer and separation of the photogenerated electron-hole pairs. Under visible-light illumination (λ≥400 nm), the NCs showed improved photocatalytic H2 -generation activity in the presence of lactic acid. The peak value of 7610.1 μmol h-1 g-1 for H2 production was achieved with an apparent quantum efficiency (AQE) of 41.68 % when the Ni/Cd ratio was set to 10 %, which was approximately 48 times higher than that of bare CdS NWs. Photoelectrochemical measurements also confirmed the pivotal role of NiSe2 in the improvement of the H2 -evolution performance of NiSe2 /CdS NCs, which is consistent with the DFT investigations.

The canonical Wnt/β-catenin signaling pathway plays a pivotal role and is essentially required for the osteoblast differentiation and bone formation. In this study, we found ubiquitin-specific peptidase 4 (USP4) to strongly inhibit the Wnt/β-catenin signaling by removing Lysine-63 linked poly-ubiquitin chain from Dishevelled (Dvl). Ectopic expression of USP4 promoted β-catenin poly-ubiquitination and thus inhibited Wnt-induced accumulation of cytosolic β-catenin and counteracted Wnt-induced transcriptional activity. Moreover, USP4 knockdown or USP4 knockout led to an increase in the active β-catenin levels and in activation of Wnt/β-catenin-induced transcription. Functional studies in C2C12 myoblasts and KS483 osteoprogenitor cells showed that ectopic expression of USP4 resulted in impaired activation of endogenous Wnt3a-induced genes and decreased osteoblast differentiation and mineralization, whereas USP4 depletion showed the opposite effect. These results identify USP4 as a novel regulator of Dvl in Wnt/β-catenin signal and show its involvement in Wnt3a-induced osteoblast differentiation. © 2016 American Society for Bone and Mineral Research.

To optimize the preparation process for ethylene vinyl acetate (EVA)/rectorite nanocomposites during the melt extrusion, the effect of rectorite on the rheological property of molten polymer has been explored in this paper. The dispersion of rectorite in EVA was probed by X-ray diffraction, and the rheological behaviors of EVA copolymer and EVA/rectorite nanocomposites during the extrusion process were investigated by means of HAAKE minilab. The positron results reveal that introducing the rectorite in EVA matrix increases the interfaces in composites. And the rheological results indicate that the viscosity of EVA and EVA/rectorite nanocomposites in the molten state was influenced by the processing temperature, processing time and shearing rate. For all the samples, the viscosity increases with increasing the shear rate, and decreases with increasing extrusion temperature. Moreover, compared with the pure EVA, the EVA/rectorite nanocomposite presents a lower viscosity at the same processing condition. Copyright © 2016 John Wiley & Sons, Ltd.

Polyaniline/TiO2−SiO2 composites were prepared by an in situ chemical oxidation polymerization approach in the presence of hybrid TiO2−SiO2 fillers. The obtained polyaniline/TiO2−SiO2 composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier transform infrared spectrometer (FTIR), X-ray diffraction (XRD), thermogravimetry (TG), and current−voltage (I−V) measurements. SEM picture shows a variation in morphology of polyaniline (PANI) from fiber shape to relatively regular particle shape with increasing TiO2−SiO2 contents in the composites. The floccule-like structures were observed by high resolution TEM, which may help improve the efficiency of conductive network. SEM, XRD, TG, and FTIR spectra all reveal that a relatively strong interaction exist between TiO2−SiO2 and PANI. The I−V characteristics in such composites indicate that the charge transport is mainly governed by the space charge effects, which occurs at the interface between the conducting PANI and TiO2−SiO2. Meanwhile, PANI/TiO2−SiO2 composites exhibit significant increase in conductivity than PANI/TiO2 or PANI/SiO2. The reasons about high conductivity of PANI/TiO2−SiO2 have also been discussed. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 130: 2288–2295, 2013

Polylactide (PLA)/polyurethane (PU) composites were prepared by reactive blending method with in situ formation of PU particles via the reaction between polyester polyol (PPG) and toluene-2,4-diisocyanate (TDI). The interfacial compatibility and adhesion between the PLA and PU phases were greatly improved by the reaction of the terminal hydroxyl groups of PLA and NCO groups of TDI forming graft copolymer, as confirmed by FTIR spectroscopy. The elongation at break and notch impact strength of PLA/PU composites increased considerably with increasing PU content, and the tensile strength of PLA/PU composites decreased slightly compared with that of pure PLA. Upon addition of 12 wt % PU, the elongation at break and notch impact strength increased to 175.17% and 10.96 kJ/m2, respectively, about 27 times and 5.4 times greater than the corresponding values for the pure PLA. The tensile strength decreased only slightly to 48.65 MPa. The excellent interfacial adhesion, the dispersed PU elastomeric particles acting as stress concentration areas, and the triggering of large matrix shear yield as well as many fibrils by internal cavitation were the main mechanical toughening mechanisms. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44383.

Layered protonated titanate nanosheets (LPTNs) loaded with silver nanoparticles are prepared by a simple one-pot hydrothermal route in silver-ammonia solution. The as-synthesized Ag-loaded LPTNs possess large specific surface area. The Ag nanoparticles are highly dispersed on the surface of the LPTNs. They have negligible effects on the crystal structure, crystallinity, and surface area of the LPTNs but result in considerable enhancement of visible-light absorption and in a red-shift of the band gap for the LPTNs. The Ag-loaded LPTNs show enhanced photocatalytic activity for both liquid- and gas-phase reactions under visible-light irradiation. Moreover, the photocatalytic activity first increases gradually with increasing Ag loading content, and then decreases after maximizing at an optimal Ag content. At the Ag loading content of 2.87 mol% and 1.57 mol%, the Ag-loaded LPTNs exhibit the highest visible-light photocatalytic activity for degradation of rhodamine B in water and mineralization of benzene in air, respectively. An alternative possible mechanism for the enhancement of the visible-light photocatalytic activity is also proposed.

Polymer blended materials such as polyamide 6 (PA6)/polypropylene (PP) blends have received considerable attention in recent years. To improve the compatibility of PA6 and PP, compatibilizers like maleic anhydride-g-polypropylene (MPP) are often added. In addition, organically modified montmorillonite (MMT) is also used to improve the properties of various materials. In this work, the crystallization behavior of PP/PA6/MMT nanocomposites with MPP compatibilizer was investigated systematically. The annealing process effectively improved the crystallization of α-PP. The crystallization temperature (Tc) of PA6 was increased by ca 2–3 °C on introducing MPP or MMT alone to the PP/PA6 system, whereas Tc of PP underwent no obvious change. However, when MPP and MMT were added simultaneously, Tc of PP and PA6 increased by 6.6 and 4.2 °C, respectively, and a new crystallization peak corresponding to PP-g-PA6 copolymer phase was observed at 162.5 °C. The combined effect of MPP and MMT led to better compatibility of PP with PA6. Moreover, the results of a non-isothermal crystallization kinetics experiment revealed that the simultaneous introduction of MPP and MMT markedly shortened the crystallization time. Copyright © 2010 Society of Chemical Industry

Poly(ether-urethane) (PEU) was irradiated by neutron in different atmospheres. The hydrogen bonding interaction was analyzed by Fourier transform infrared (FTIR), and the microstructure of PEU had been investigated by positron annihilation lifetime spectroscopy (PALS). The gas products were detected by gas chromatography after irradiation. The results demonstrated that the irradiation led to more hydrogen bonded carbonyl in PEU, smaller relative free volume fraction, and narrower free volume distribution. It suggested that increasing hydrogen bonds would result in the collapse of free volume. The irradiation induced micro-phase merging together and the presence of oxygen would accelerate this tendency, which was revealed by PALS. All the results indicated that the chain relaxation led to more hydrogen bonds, and the hydrogen bonding interaction suppressed the free volume. © 2009 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 48: 381–388, 2010

Organically modified montmorillonite (org-MMT) and high-density polyethylene (HDPE) grafted with silane groups (HDPE-g-silane) were melt compounded to give HDPE-g-silane-blend-org-MMT nanocomposites. X-ray diffractometry was performed to investigate the intercalation effect. Transmission electron microscopy was applied to observe the dispersion of org-MMT layers in HDPE matrices. The results indicate that an intercalated structure can be easily obtained in HDPE-g-silane-blend-org-MMT nanocomposites. Furthermore, positron annihilation lifetime spectroscopy was used to characterize the microstructure of the composites. It is found that the ortho-positron (o-Ps) intensity for HDPE-g-silane is decreased by approximately 10% with a narrower lifetime distribution than that for HDPE. With increasing org-MMT concentration, the o-Ps intensity I3 increases for HDPE-g-silane-blend-org-MMT nanocomposites; however, for HDPE-blend-org-MMT composites I3 decreases. It is found that HDPE composites with good dispersion can be obtained following appropriate modification of the HDPE. And silane grafting has an effect on the free volume of the HDPE nanocomposites. Copyright © 2007 Society of Chemical Industry

Two types of composites, high-density polyethylene (HDPE)/Bentonite (BT) and high-density polyethylene grafted with acrylic acid (HDPE-g-AA)/(BT), are prepared by melt compounding. The microstructure of the composite has been studied by the means of positron annihilation lifetime spectroscopy (PALS). It has been found that the mean free volume size is nearly the same in composites and HDPE matrices with different BT concentration. While the ortho-positronium (o-Ps) intensity decreased for HDPE-g-AA and its lifetime distribution is narrower than that for pure HDPE. With the increasing of BT content, the o-Ps intensity increases for HDPE-g-AA/BT composites and the o-Ps intensity decreases for HDPE/BT composites. It is found that the carboxyl group of Acrylic acid plays a significant chemical inhibition on positronium formation. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

The epoxy-rectorite nanocomposites were prepared at different curing temperature ranged from 70 °C to 200 °C and the effects of curing temperature on microstructure of material have been studied by positron annihilation lifetime spectroscopy (PALS), and X-ray diffraction (XRD). The XRD patterns show that the intercalated structure existed in the samples cured at 70 °C and 90 °C, and the clay platelets were completely exfoliated while the curing temperature is higher than 110 °C. At low rectorite content the Ps is mainly formed and annihilated in the free volume of the epoxy matrix and the average size of the free volume is essentially unchanged with the curing temperature. With the increasing curing temperature from 70 °C to 110 °C, the dramatic increase in the intensity I2 of second lifetime component indicates the formation of interfacial layers between rectorite and epoxy matrix. The distributions of o-Ps lifetime and the free volume size have the narrowest distribution for the samples cured at temperature 110 °C and 140 °C, which imply the most homogeneous structure existed in the nanocomposites. (© 2007 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

The rheological behavior, thermal properties, and molecular mobility of a series of maleic anhydride (MA) grafted high-density polyethylenes were characterized and evaluated. The rheological behavior was studied with a Haake minilaboratory. The viscosity of the samples in their melt state decreased with an increase in the graft yield, and this could be attributed to the higher molecular mobility for samples with a higher degree of grafting. The thermal properties were investigated with dynamic mechanical analysis and differential scanning calorimetry. Positron annihilation lifetime measurements were used to study the effect of the degree of grafting on the chemical environment and the atomic-scale free-volume properties. It was found that the grafted MA group played a significant chemical inhibition role in positronium formation when the graft yield was low. The results also indicated that the higher the degree of grafting was, the broader the free-volume distribution was. The relationship between the microstructure and rheological behavior is discussed. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008

Ethylene-(vinyl acetate) copolymer (EVA)/rectorite nanocomposites were prepared by direct melt extrusion of EVA and organo-rectorite. The microstructures and thermal properties of EVA nanocomposites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), solid-state nuclear magnetic spectroscopy, positron annihilation spectroscopy, thermal gravimetric analysis (TGA) and dynamic mechanical analysis techniques. XRD pattern and SEM images show that the intercalated structure is formed and rectorite is finely dispersed in EVA matrix. When organoclay content of the hybrid increases to 7.5 wt%, or pristine rectorite was used instead of organoclay, the crystallization behavior of EVA nanocomposite changes greatly and the ratio of the monoclinic to orthorhombic crystal increases significantly. The relative fractional free volume of the nanocomposite decreases with the increasing organo-rectorite content, and the values of damping factor (tan delta) for all nanocomposites are lower than that of pure EVA. These facts illuminate that intercalated structure restricts the segment motion and mobilization of polymer chain. TGA results of EVA nanocomposites in air indicate that deacylation of EVA is accelerated because of the catalytic effect and the thermal degradation of the main chain is delayed owing to the barrier effect of silicate layers. (C) 2005 Society of Chemical Industry.

The study is focused on the processing behavior of poly(ethylene-co vinyl acetate) (EVA) in high temperature, such as 200°C. The specimens are characterized using HAAKE minilab, dynamic mechanical analysis (DMA), and positron annihilation lifetime spectroscopy (PALS) to understand the rheological behavior and microstructure of EVA. It was concluded that in high processing temperature, the viscosity declined first and then increased. The PALS results showed that the free volume of EVA became large at the beginning, and became small afterwards. The glass transition temperature measured with DMA got lower at first and then nearly unchanged with increasing handling time. The results can be explained that the degradation of EVA prevailed, and then degradation was not dominant. A good correlation has been found between the processing time and temperature of the transition point in the viscosity curve. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 2022–2026, 2006

Solid-state nuclear magnetic resonance spectroscopy and relaxation measurements, together with DSC, have been used to elucidate the structures and molecular dynamics in poly(ethylene-co-vinyl acetate) (EVA). It has been found that besides immobile orthorhombic and monoclinic crystalline phases, the third mobile crystalline phase (possibly the phase) of a considerable amount (36% of total crystalline phases) appears in the EVA samples, which forms during room-temperature aging as a result of the secondary crystallization and melts at temperature somewhat higher than room temperature. Such a mobile crystalline phase has not only the well-defined chemical shift of its own, but also has different molecular mobility from the orthorhombic phase. The mobile crystalline phase is characterized by the rapid relaxation of the longitudinal magnetization, which is caused by conventional spin-lattice relaxation, while the slow relaxation of the longitudinal magnetization occurring in the orthorhombic phase is originated from the chain diffusion. In addition, the amorphous phase also contains two components: an interfacial amorphous phase and a melt-like amorphous phase. (c) 2006 Wiley Periodicals, Inc.

Seven kinds of poly(methyl methacrylate) (PMMA) films doped with [60]fullerene or its inclusion complex of p-tert-butylcalix[8]arene were prepared and characterized by FTIR, UV-vis, TG, and DSC. It was found that the thermal stability of PMMA is much improved by doping with the inclusion complex in comparison with [60]fullerene itself, that is, the inclusion complex retards the thermal depolymerization of PMMA very effectively. The influence of incorporating active carbon powder or calix[8]arene on the thermal stability of PMMA was also investigated. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 1549–1552, 2002

This paper investigates the effect of aluminum hydroxide (ATH) content on the free volume and surface recovery property of polydimethylsiloxane (PDMS)–based silicone rubber containing low-molecular-weight siloxanes. With increasing ratio of ATH up to 43.1 wt %, the concentration of cyclic siloxanes (Dn = [(CH3)2SiO]n, n = 4–12) in the PDMS matrix increases remarkably, indicative of a spacing effect of ATH particles on the crosslinking of PDMS chains. When more ATH is added, the concentration of D4–D12 began to decrease. PDMS network variation is verified by free volume size corresponding to τ3 in positron annihilation lifetime spectroscopy. The o-Ps intensity decreases linearly with ATH content. Data obtained from X-ray photoelectron spectroscopy suggest the surface recovery property is weakened by ATH. This process is dominated by the amount of free volume holes in the sample. © 2017 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2018, 135, 45803.

Expanded repeats of r(CGG) in the 5’-untranslated region of the fragile X mental retardation protein mRNA cause fragile X and fragile X-associated tremor/ataxia syndromes. Expanded repeats fold into an RNA hairpin with repeating 5’-CGG/3’-GGC motifs. Herein, we report a structure of a model RNA duplex with three copies of the 5’-CGG/3’-GGC motif (PDB ID: 3JS2), refined to 1.36 . All three GG internal loops have N1-carbonyl, N7-amino pairs and are closed by standard Watson–Crick CG pairs. The results expand the available structures of triplet repeating transcripts and provide information to help understand how these RNAs bind small-molecule and protein ligands. Although RNA is an important target for small molecules, most functionally important RNAs have not been exploited in targeting endeavors. This is thought to be due generally to the lack of a fundamental understanding of RNA motifs that specifically bind small molecules and the small molecules that specifically bind RNA motifs. One important class of RNAs that can be exploited as a drug target by small molecules is that of triplet-repeating transcripts. A variety of diseases, including fragile X syndrome (FXS, r(CGG)), Friedreich’s ataxia (r(CGG)), the spinocerebellar ataxias (r(CAG) or r(CUG)), and myotonic dystrophy (r(CUG)) are caused by triplet-repeating RNAs. These expanded repeating transcripts fold into higher-order hairpin structures with regularly repeating 1 1 nucleotide internal loops separated by two GC base pairs, as determined by chemical probing of RNA structure (Figure 1A). Two different general mechanisms for how triplet-repeating transcripts cause disease have been established. In the first mechanism, which has been best established for Huntington’s disease, a repeating transcript of r(CAG) is present in an mRNA coding region. When that transcript is translated, polyQ proteins are synthesized and cause toxicity. In a second mechanism, which has been best established for myotonic dystrophy type 1 (DM1), the expanded repeat is present in a non-coding region in an mRNA, such as a 3’-untranslated region (UTR). The transcribed repeat sequesters RNA-binding proteins such as muscleblind-like protein 1 (MBNL1), and this controls premRNA splicing. Sequestration of MBNL1 by expanded r(CUG) repeats causes both translational defects of the mRNA with the expanded repeat and pre-mRNA splicing defects. Recent studies have shown that the pathology of fragile Xassociated tremor/ataxia syndrome (FXTAS) can be due to the latter disease mechanism and FXS is due to a well-established translational-defect mechanism. FXTAS is caused when 55– 200 r(CGG) repeats are present in the 5’-UTR of the fragile X mental retardation 1 mRNA (FMR1). A Drosophila model of FXTAS was developed by heterologous expression of 90 r(CGG) repeats that were not translated. The repeats alone caused a neurodegenerative phenotype associated with FXTAS. In patient-derived FXTAS cell lines, r(CGG) repeats form inclusion complexes that contain, for example, the Src-associated, 68 kDa (Sam68) protein in mitosis, heterogeneous nuclear ribonucleoprotein G (hnRNP-G) protein, and MBNL1. These studies also showed that r(CGG) repeats first bind a protein, which has yet to be determined, that first recruits Sam68, which further recruits hnRNP-G and MBNL1 to the r(CGG) repeats. Furthermore, pre-mRNA splicing of Sam68-controlled transcripts is affected in FXTAS-patient-derived cell lines. These mechanistic studies suggest a therapeutic strategy towards developing a treatment for FXTAS in which a small-molecule ligand binds expanded r(CGG) repeats and inhibits protein binding, thereby freeing the protein to perform its normal physiological roles. Such strategies have already been implemented for DM1. For example, oligonucleotides and a small molecule, pentamidine, target expanded r(CUG) repeats and correct DM1-associated splicing defects in mouse models. General strategies for targeting triplet-repeating transcripts with small molecules have been developed and are centered on a modular-assembly strategy. In order to develop an atomic understanding of the structure of r(CGG) repeats, we have refined diffraction data on a Figure 1. The secondary structure, refined structure, and crystal packing of the RNA construct. A) The secondary structure of the oligonucleotide r(CGG) repeat duplex model that allowed crystal growth. B) The global structure of the RNA including the electron density map at 1.0s. C) Side and D) top views of the crystal packing that was observed in the unit cell within 5 .