Size-Dependent Phase Transition in Ultrathin Ga2O3 Nanowires.

Gallium oxide (Ga2O3) has attracted extensive attention as a potential candidate for low-dimensional metal-oxide-semiconductor field-effect transistors (MOSFETs) due to its wide bandgap, controllable doping, and low cost. The structural stability of nanoscale Ga2O3 is the key parameter for designing and constructing a MOSFET, which however remains unexplored. Using in situ transmission electron microscopy, we reveal the size-dependent phase transition of sub-2 nm Ga2O3 nanowires. Based on theoretical calculations, the transformation pathways from the initial monoclinic ß-phase to an intermediate cubic γ-phase and then back to the ß-phase have been mapped and identified as a sequence of Ga cation migrations. Our results provide fundamental insights into the Ga2O3 phase stability within the nanoscale, which is crucial for advancing the miniaturization, light weight, and integration of wide-bandgap semiconductor devices.

Probing the Atomistic Reaction Pathways in CuO/C Catalysts.

CuOx/C catalysts have been used in the selective catalytic reduction of NOx because of the exceptional low-temperature denitration (de-NOx) activity. A fundamental understanding of the reaction between CuO and C is critical for controlling the component of CuOx/C and thus optimizing the catalytic performance. In this study, a transmission electron microscope equipped with an in situ heating device was utilized to investigate the atomic-scale reaction between CuO and C. We report two reaction mechanisms relying on the volume ratio between C and CuO: (1) The reduction from CuO to Cu2O (when the ratio is < ∼31%); (2) the reduction of CuO into polycrystalline Cu (when the ratio is > ∼34%). The atomistic reduction pathway can be well interpreted by considering the diffusion of O vacancy through the first-principle calculations. The atomic-scale exploration of CuO/C offers ample prospects for the design of industrial de-NOx catalysts in the future.

Pseudo-Elasticity and Variable Electro-Conductivity Mediated by Size-Dependent Deformation Twinning in Molybdenum Nanocrystals.

Deformation twinning merits attention because of its intrinsic importance as a mode of energy dissipation in solids. Herein, through the atomistic electron microscopy observations, the size-dependent twinning mechanisms in refractory body-centered cubic molybdenum nanocrystals (NCs) under tensile loading are shown. Two distinct twinning mechanisms involving the nucleation of coherent and inclined twin boundaries (TBs) are uncovered in NCs with smaller (diameter < ≈5 nm) and larger (diameter > ≈5 nm) diameters, respectively. Interestingly, the ultrahigh pseudo-elastic strain of ≈41% in sub-5 nm-sized crystals is achieved through the reversible twinning mechanism. A typical TB cross-transition mechanism is found to accommodate the NC re-orientation during the pseudo-elastic deformation. More importantly, the effects of different types of TBs on the electrical conductivity based on the repeatable experimental measurements and first-principles calculations are quantified. These size-dependent mechanical and electrical properties may prove essential in advancing the design of next-generation flexible nanoelectronics.

Cation Defect Mediated Phase Transition in Potassium Tungsten Bronze.

Applying in situ transmission electron microscopy, the phase instability in potassium tungsten bronze (KxWO3, 0.18 < x < 0.57) induced by heating was investigated. The atomistic phase transition pathway of monoclinic K0.20WO3 → hexagonal KmWO3 (0.18 < m < 0.20) → cubic WO3 induced by cationic defects (K and W vacancies) was directly revealed. Unexpectedly, a K+-rich tetragonal KnWO3 (0.40 < n < 0.57) phase would nucleate as well, which may result from the blockage of K+ diffusion at the grain boundaries. Our results point out the critical role of the cationic defects in mediating the crystal structures in KxWO3, which provide reference to rational structural design for extensive high-temperature applications.

Surface- and Strain-Mediated Reversible Phase Transformation in Quantum-Confined ZnO Nanowires.

The phase stability of ZnO in a quantum-confinement size regime (sub-2-nm) remains fiercely debated. Applying in situ (scanning) transmission electron microscopy, we present the atomistic view of the phase transitions from the original wurtzite structure to an intermediate body-centered tetragonal and h-MgO structure under tensile strain in quantum-confined ZnO nanowires. Strikingly, such structural transitions are reversible after releasing the stress. Further theoretical calculations mirror the transition pathway and provide basic insight into the overall landscape regarding surface- and strain-dependent phase transition behavior. Our results provide the critical piece to solve the puzzle in phase stability of ZnO, which may prove essential for advancing a variety of nanotechnologies, e.g., quantum-dot light-emitting devices.

[High sustained virological response to optimized therapy for refractory chronic hepatitis C treatment-na(i)ve patients: a multicenter randomized study].

OBJECTIVE: To perform a prospective,multicenter,open,randomized study to determine a treatment regimen for treatment-naive patients with refractory chronic hepatitis C (RHC) using the predictive value (PV) of early virological response (EVR). METHODS: A total of 438 patients from 18 hospitals were recruited between December 2008 and December 2010 and administered peg-interferon/ribavirin treatment for 12 weeks. Patients who achieved complete EVR (cEVR) were assigned to group A for a 48-week course of treatment, while patients without cEVR were randomly allocated to either group B 1 for a 72-week course of treatment or to group B2 for a 96-week course of treatment. Serum hepatitis C virus RNA levels at baseline,treatment weeks 4, 12 and 24, end of treatment, and post-treatment week 24 were measured and used to evaluate the efficiency of therapy. RESULTS: The overall sustained virological response (SVR) rate was 85.1%. In all, 91.0% of patients achieved cEVR and were assigned to group A, which had an SVR rate of 90.8%. There was no statistically significant difference in the SVR rates of groups B1 and B2 (29.4% vs. 25.0%, P more than 0.05). The positive PV of rapid virological response (RVR), cEVR and delayed virological response (DVR) for SVR was 93.4%, 90.8% and 77.8% respectively, and the negative PV of RVR, EVR and DVR for SVR was 28.0%, 93.3% and 100% respectively. Overall, 66.9% of the patients experienced adverse events (AEs), but only 1.9% of patients experienced sevcre AEs. CONCLUSION: The majority of Chinese RHC treatmentna(i)ve patients (91.0%) can achieve cEVR and a high SVR rate with a low rate of severe AEs using the cEVR guided personal treatment regimen.

Strong interlayer coupling and unusual antisite defect-mediated p-type conductivity in GePx (x = 1, 2).

As an emerging candidate for anisotropic two-dimensional materials, the group IV-V family (e.g. GeP, GeP2) has appealing applications in photoelectronics. However, their intrinsic point defect properties, which largely determine the device performance and optimization, are still poorly explored. In our study, through density functional theory (DFT) calculations, antisite defects were affirmed to be dominant with the lowest formation energies in 2D GePx semiconductors because of the similar atomic size and electronegativity of elemental components, which is in contrast to previous calculations and experimental speculation. These antisite defects could introduce relatively shallow states within the bandgap in bulk cases. The transition energy levels and electronic structures of defects reveal that GeP and PGe antisites act as dominant acceptors and donors, respectively. Strong interlayer coupling between anions results in a significant upshift of the valence band maximum (VBM) and shallower acceptor behaviors of GePx. Together with the dominant GeP antisite defect, the large upshift of the VBM in GeP leads to a remarkable transition of conductivity from intrinsic in the monolayer to p-type in the bulk. Such a synergistic effect in GeP2 is rather weak due to the strong inherent intralayer coupling of anions. Our research provides deep insights into the strong anion coupling effects on the electronic structures and defect properties of GeP and GeP2, which sheds light on defect engineering and electronic applications of GePx based semiconductors.

Na+ Migration Mediated Phase Transitions Induced by Electric Field in the Framework Structured Tungsten Bronze.

Framework structured tungsten bronzes serve as promising candidates for electrode materials in sodium-ion batteries (SIBs). However, the tungsten bronze framework structure changes drastically as mediated by the sodium ion concentration at high temperatures. While the three-dimensional ion channels facilitate fast ion storage and transport capabilities, the structural instability induced by Na+ migration is a big concern regarding the battery performance and safety, which unfortunately remains elusive. Here, we show the real-time experimental evidence of the phase transitions in framework structured Na0.36WO3.14 (triclinic phase) by applying different external voltages. The Na+-rich (Na0.48WO3, tetragonal phase) or -deficient (NaxWO3, x < 0.36, hexagonal phase) phase nucleates under the positive or negative bias, respectively. Combined with the theoretical calculations, the atomistic phase transition mechanisms associated with the Na+ migration are directly uncovered. Our work sheds light on the phase instability in sodium tungsten bronzes and paves the way for designing advanced SIBs with high-stability.

Unexpected Two-Dimensional Polarons Induced by Oxygen Vacancies in Layered Structure MoO3-x.

Unveiling the effects of oxygen vacancies on the structural stability of layered α-MoO3 is critical for optimizing its physical and chemical properties. Herein, we present experimental evidence regarding the phase stability of α-MoO3 with ∼2% oxygen vacancy concentrations. Interestingly, we report a previously ignored oxygen-deficient orthorhombic MoO3-x phase in space group Cmcm. Further density functional theory calculations reveal a detailed phase transition mechanism from α-MoO3 to MoO3-x. More importantly, we demonstrate that two-dimensional (2D) large polarons must exist to stabilize the MoO3-x crystal structure. 2D large polarons are suspected to exist in numerous quasi-2D systems but have never been found in layered α-MoO3 or other molybdenum oxides. Our work contributes to a basic understanding of the polaronic behavior in MoO3-x and may broaden the application realm of molybdenum oxides.

Cell-modified plasmonic interface for the signal-amplified detection of Cucurbitacin E.

Cucurbitacin E (CuE) plays an important role in anticancer, antichemical carcinogenesis, and body immunity, etc., and the detection of its concentration is meaningful to pharmacological studies and clinical applications. However, the small molecular weight of CuE makes direct detection difficult through a surface plasmon resonance (SPR) sensor. In this work, we propose a cells-amplified signal strategy at the plasmonic interface, realizing the detection of CuE with ultra-low concentration. The seeded HeLa cells are modified onto the surface of the SPR sensor, and a small amount of CuE can lead to the remarkable morphology change of cells and the release of cell-related substances onto the plamonic interface, thus significantly amplifying the signal. Experimental results show that by using an unmodified SPR sensor with the bulk refractive index sensitivity of 2367.3 nm/RIU (RIU: refractive index unit), there no effective signal can be detected during the CuE concentration range of 0-100 nM; whereas, employing the proposed strategy, the signal for CuE detection can be significantly enhanced, resulting in a high detection sensitivity of 0.6196 nm/nM, corresponding to a limit of detection of 45.2 pM (25.2 pg/mL). The proposed cells-based signal amplifying strategy shows great potential applications in drug screening or bio-sensing to small molecules with low concentration.

Room-temperature oxygen vacancy migration induced reversible phase transformation during the anelastic deformation in CuO.

From the mechanical perspectives, the influence of point defects is generally considered at high temperature, especially when the creep deformation dominates. Here, we show the stress-induced reversible oxygen vacancy migration in CuO nanowires at room temperature, causing the unanticipated anelastic deformation. The anelastic strain is associated with the nucleation of oxygen-deficient CuOx phase, which gradually transforms back to CuO after stress releasing, leading to the gradual recovery of the nanowire shape. Detailed analysis reveals an oxygen deficient metastable CuOx phase that has been overlooked in the literatures. Both theoretical and experimental investigations faithfully predict the oxygen vacancy diffusion pathways in CuO. Our finding facilitates a better understanding of the complicated mechanical behaviors in materials, which could also be relevant across multiple scientific disciplines, such as high-temperature superconductivity and solid-state chemistry in Cu-O compounds, etc.

Atomistic Observation of Desodiation-Induced Phase Transition in Sodium Tungsten Bronze.

The phase instability in layered-structure Na0.5WO3.25 induced by the extraction of Na ions was investigated by applying transmission electron microscopy. Real-time atomic-scale observation reveals the phase transition pathway: Na0.5WO3.25 (triclinic) → NaxWO3 (cubic) → WO3 (monoclinic) with specific orientation relationships. The dynamic evolution of Na0.5WO3.25/NaxWO3 phase boundaries shows that Na0.5WO3.25 will cleave along the (100)T and (010)T and recrystallize as (101)C and (010)C of NaxWO3, respectively. The phase transition pathway can be well-explained according to the structural characteristics in the three phases. By better understanding of the phase instability induced by the extraction of Na ions in possible layered-structure cathode materials, this work provides a reference for the design of sophisticated strategies toward high-performance Na-ion batteries.

Effects of peptidoglycan on the development of steatohepatitis.

Elevating evidences suggested roles of peptidoglycan (PGN) for the insulin resistance, metabolic inflammation and liver disorders. But, whether PGN affects the occurrence of steatohepatitis remains unclear. Here, we reported that subcutaneous infusion of purified PGN for 4 weeks significantly increased hepatic levels of triglyceride, inflammation and fibrosis in mice fed normal chow. These alterations were associated with raise in circulating triglyceride, cholesterol, insulin content and inflammatory cytokines. PGN significantly increased triglyceride contents as well as lipogenesis related genes in primary hepatocytes or LO2 cells, either in basal or oleic acid treated conditions. Administration of PGN stimulated the expression of NOD2, as well as phosphorylation of p65 and IκBα, leading to subsequent nuclear translocation of p65. Over-expression of NOD2 significantly enhanced the phosphorylation of p65, levels of nuclear PPARγ and SREBP1, followed by increase in triglyceride contents in LO2 cells treated with or without oleic acid. Further, over-expression of NOD2 significantly augmented the up-regulation of PPARγ induced by rosiglitazone. Inhibition of NFκB blocked the effect of NOD2 on the upregulation of PPARγ. Our study demonstrates that PGN stimulates hepatic lipogenesis by NOD2-NFκB-PPARγ signaling. PGN from intestinal microbiota is thus sufficient to induce the progression of steatohepatitis.

Atomistic and dynamic structural characterizations in low-dimensional materials: recent applications of in situ transmission electron microscopy.

In situ transmission electron microscopy has achieved remarkable advances for atomic-scale dynamic analysis in low-dimensional materials and become an indispensable tool in view of linking a material's microstructure to its properties and performance. Here, accompanied with some cutting-edge researches worldwide, we briefly review our recent progress in dynamic atomistic characterization of low-dimensional materials under external mechanical stress, thermal excitations and electrical field. The electron beam irradiation effects in metals and metal oxides are also discussed. We conclude by discussing the likely future developments in this area.

Polymerizable-group capped ZnS nanoparticle for high refractive index inorganic-organic hydrogel contact lens.

Refractive index (RI) is an important parameter for contact lens biomaterials. In this paper, a novel polymerizable-group capped ZnS nanoparticle (NP) was synthesized by chemical link between hydroxyl group on the surface of ZnS (ME-capped) and isocyanate group of polymerizable molecule of 2-isocyanatoethyl methacrylate. Then the ZnS NP copolymerized with monomer of 2-hydroxyethyl methacrylate (HEMA) and N,N-dimethylacrylamide (DMA) to prepare high refractive index hydrogel contact lens with high content of inorganic ZnS NP. Increasing polymerizable-group capped ZnS content in the hydrogels improved its RI value and mechanical properties, however decreased slightly its transmittance, equilibrium (ESR) and lysozyme deposition on the hydrogel surface. The ZnS-containing hydrogels possessed good cytocompatibility and in vivo biocompatibility in rabbit eyes, demonstrating a potential application as high RI ocular refractive correction biomaterial.

Iodine-responsive poly (HEMA-PVP) hydrogel for self-regulating burst-free extended release.

Swollen hydrogels with extended iodine release kinetics is highly desirable for burn and scald treatment. In this paper semi-interpenetrating poly (HEMA-PVP) hydrogels were prepared by radical polymerization followed by thermo-treatment to crosslink its PVP component. Incorporation of PVP component endows the hydrogels responsive to loaded iodine undergoing a reversible shrunken/swollen volume transition. This resulted in a self-regulating iodine release model, in which shrunken hydrogel at high iodine loading decreased drug diffusion thereby reducing burst release, and then gradually swollen hydrogel as drug release ensures rapid release of dissociated drug from strong affinity sites on hydrogel backbone, achieving a burst-free extended release. The hydrogels demonstrated 11.5-fold higher iodine loading than pure pHEMA hydrogel and showed a highest 40% volume shrink. Initial burst release of iodine was efficiently decreased from 12,894 µg/day of pure pHEMA hydrogel to 2570 µg/day of pHEMA/PVP hydrogel with 37% PVP content. Iodine-loaded hydrogels showed zero-order release at three time periods of 0-15 h, 15 h-3.5 days and 3.5-23.5 days corresponding to release rate of 2570, 776 and 493 µg/day. The work gained a new insight into swollen hydrogel drug delivery system with burst-free extended drug release kinetics.

Efficacy and safety of nucleoside analogs on blocking father-to-infant vertical transmission of hepatitis B virus.

The aim of the present study was to observe the efficacy and safety of nucleoside analogs in inhibiting father-to-infant vertical transmission of hepatitis B virus (HBV). Nucleoside analogs compete with HBV DNA polymerase substrate to inhibit DNA polymerase, thus preventing the replication of HBV DNA. A case group and control group were recruited for the study. Between March 2006 and March 2012 at the Liver Disease Center of Qinhuangdao Third Hospital, a total of 201 couples were recruited for the case group. In each case, the father tested positive the following HBV markers: Hepatitis B surface antigen (HBsAg), hepatitis B e antigen (HBeAg), antibodies against the hepatitis B core antigen (anti-HBc) and HBV DNA. In total, 189 male patients presented with abnormal liver function (94.0%; 189/201). Prior to pregnancy, all the males in the case group were required to test negative for HBV DNA and exhibit normal liver function, while the females were required to test positive for antibodies against HBsAg (anti-HBs). In total, 188 couples comprised the control group. The couples were recruited between March 2006 and March 2012 in the Prenatal Clinic of Qinhuangdao Women's and Children's Hospital. The fathers tested positive for HBsAg, HBeAg, anti-HBc and HBV DNA. With regard to the females, HBsAg tests were all negative and anti-HBs tests were positive. In the case group, there were no HBsAg-positive or HBV DNA-positive newborns, while anti-HBs tests were all positive; thus, the father-to-infant HBV vertical transmission was successfully inhibited. In the control group, 147/188 newborns tested positive for anti-HBs at birth, accounting for 78.2%. In addition, 28 newborns were positive for HBV DNA (14.9%), and 19 newborns tested positive for HBsAg (10.1%). Statistically significant differences were observed between the two groups with regard to these parameters. However, no statistically significant differences in gestational age, birth weight, birth height, 1- and 8-min Apgar scores, presence of jaundice, other internal and surgical diseases, delivery mode and other birth information were observed when comparing the case group with the control group. Furthermore, there were no fetal malformations or stillbirths in the two groups. In the HBV DNA-positive fathers prior to pregnancy, antiretroviral therapy resulted in a reduced virus load. Therefore, blocking father-to-infant HBV vertical transmission maximally was important. The use of antiviral nucleoside analogs prior to pregnancy was shown to be safe. When the benefits outweighed the risks, the fathers who wanted to have a child continued to use antiviral therapy. However, the sample size of the present study was small, and an increased number of cases and longer follow-up times are required. In addition, the use of nucleoside analogs requires further in-depth assessment from the point of view of prenatal and postnatal care.

[Mutation analysis of the HBV reverse transcriptase in nucleos(t)ide-treated patients with chronic HBV infection].

OBJECTIVE: To characterize genotypic resistance within HBV RT region in chronic hepatitis B (CHB) patients with nucleos(t)ide analogue (NA) treatment. METHODS: Serum samples of 229 CHB patients with NA treatment were obtained. Full-length HBV RT sequences were amplified, sequenced and analyzed, on the following NA resistant (NAr) mutations belonging to different NAr pathways. RESULTS: Among 229 HBV isolates, 14.41% (33/229) and 85.59% (196/229) were genotype B and C, respectively; and the patients with HBV genotype C may be more susceptible to develope resistant mutations than patients with HBV genotype B(chi2 = 2.95, P < 0.05). NAr mutations were detected in 63 CHB patients. Mutations were not found at rtI169, rtT184, rtA194 or rtS202. RtM204 mutations were detected at the highest frequency among 63 mutants (40/63, 63.49%) and found to display 11 combination mutation patterns, in which rtM204I were associated with rtL80I/V and rtL180M, and rtM204V were associated with rtL1l80M, respectively. Conclusions There are complicated mutation patterns in the HBV RT region for chronic hepatitis B (CHB) patients with nucleos(t)ide analogue (NA) treatment. RtM204V/I mutation was the highest.

[A exploration and study of the relationships of hand-foot-mouth disease (HFMD) and the climate].

OBJECTIVE: To explore and study the relationships between the popularity of HFMD and the climate in Qinhuangdao city. METHODS: HFMD cases were collected on a ten-day basis in 2009 in Qinhuangdao city. At the same time, the data about Qinhuangdao's ten-day average temperature and average humidity were provided by the Qinhuangdao Meteorological bureau. Then the collected data were analysed using the great data analysis function in the EXCELE software. RESULTS: The results showed that the disease of HFMD had a positive relationship with seasons. The cases of HFMD began to rise at the last ten days of March and rised dramatically at the middle ten days of April; In July, the cases of HFMD arrived at peak and then decline gradually. The cases of HFMD in October were quite similar to the cases of HFMD in March. Then in November, the cases of HFMD declined rapidly. All these evidences suggested that the peak seasons of HFMD were Spring and Summer. CONCLUSION: The situations of HFMD had a significant positive relationship with the conditions of climate, such as high temperature and high humidity.