[Exploration and contemplation of homogenized education of specialists in pulmonary and critical care medicine at member hospitals of a hospital consortium]

Talent construction is the cornerstone to the establishment of a high-quality, homogeneous healthcare system in a healthcare consortium. Pulmonary and critical care medicine (PCCM) as the first pilot specialty, the standardized training of PCCM specialists has started and achieved remarkable results. The consortium member hospitals' physician specialist education is an important complement to PCCM training. The establishment of the consortium provides a new form of the education of physicians in PCCM, with the advantages of high quality teaching, wide coverage of staff and throughout the career development process. This article summarized the current status of physician specialty education in the member hospitals of the consortium, and further proposes the goal of homogenized specialty education for physicians in the member hospitals. And it analyzed in depth the problems that existed in the practice of training for hospital consortium member hospitals specialists, such as non-uniform level of instruction, non-systematic content of training, limited sources of teaching cases, and lack of teaching materials and equipment. For the medical consortium member hospital physician specialty education of in-depth thinking, we put forward the corresponding countermeasures. The aim of this study is to explore the homogenization of the specialty education system of pulmonary and critical care medicine in the member hospitals, in order to comprehensively improve the medical level of respiratory specialists in the member hospitals of the medical consortium.

Recent progress of TMD nanomaterials: phase transitions and applications

Transition metal dichalcogenides (TMDs) show wide ranges of electronic properties ranging from semiconducting, semi-metallic to metallic due to their remarkable structural differences. To obtain 2D TMDs with specific properties, it is extremely important to develop particular strategies to obtain specific phase structures. Phase engineering is a traditional method to achieve transformation from one phase to another controllably. Control of such transformations enables the control of properties and access to a range of properties, otherwise inaccessible. Then extraordinary structural, electronic and optical properties lead to a broad range of potential applications. In this review, we introduce the various electronic properties of 2D TMDs and their polymorphs, and strategies and mechanisms for phase transitions, and phase transition kinetics. Moreover, the potential applications of 2D TMDs in energy storage and conversion, including electro/photocatalysts, batteries/supercapacitors and electronic devices, are also discussed. Finally, opportunities and challenges are highlighted. This review may further promote the development of TMD phase engineering and shed light on other two-dimensional materials of fundamental interest and with potential ranges of applications.

Adsorption of metal atoms on silicene: stability and quantum capacitance of silicene-based electrode materials

Metal-doping with the formation of a metal–vacancy complex results in an obvious increase of silicene's quantum capacitance.

First principles study on 2H–1T′ transition in MoS2 with copper

Adsorption of Cu can induce phase transition of MoS₂ from 2H to metallic 1T′.

Superconductivity in HfTe5 across weak to strong topological insulator transition induced via pressures

Recently, theoretical studies show that layered HfTe₅ is at the boundary of weak & strong topological insulator (TI) and might crossover to a Dirac semimetal state by changing lattice parameters. The topological properties of 3D stacked HfTe₅ are expected hence to be sensitive to pressures tuning. Here, we report pressure induced phase evolution in both electronic & crystal structures for HfTe₅ with a culmination of pressure induced superconductivity. Our experiments indicated that the temperature for anomaly resistance peak (Tp) due to Lifshitz transition decreases first before climbs up to a maximum with pressure while the Tp minimum corresponds to the transition from a weak TI to strong TI. The HfTe₅ crystal becomes superconductive above ~5.5 GPa where the Tp reaches maximum. The highest superconducting transition temperature (Tc) around 5 K was achieved at 20 GPa. Crystal structure studies indicate that HfTe₅ transforms from a Cmcm phase across a monoclinic C2/m phase then to a P-1 phase with increasing pressure. Based on transport, structure studies a comprehensive phase diagram of HfTe₅ is constructed as function of pressure. The work provides valuable experimental insights into the evolution on how to proceed from a weak TI precursor across a strong TI to superconductors.

Design of Hydrogen Storage Alloys/Nanoporous Metals Hybrid Electrodes for Nickel-Metal Hydride Batteries

Nickel metal hydride (Ni-MH) batteries have demonstrated key technology advantages for applications in new-energy vehicles, which play an important role in reducing greenhouse gas emissions and the world's dependence on fossil fuels. However, the poor high-rate dischargeability of the negative electrode materials-hydrogen storage alloys (HSAs) limits applications of Ni-MH batteries in high-power fields due to large polarization. Here we design a hybrid electrode by integrating HSAs with a current collector of three-dimensional bicontinuous nanoporous Ni. The electrode shows enhanced high-rate dischargeability with the capacity retention rate reaching 44.6% at a discharge current density of 3000 mA g(-1), which is 2.4 times that of bare HSAs (18.8%). Such a unique hybrid architecture not only enhances charge transfer between nanoporous Ni and HSAs, but also facilitates rapid diffusion of hydrogen atoms in HSAs. The developed HSAs/nanoporous metals hybrid structures exhibit great potential to be candidates as electrodes in high-performance Ni-MH batteries towards applications in new-energy vehicles.

Pressure evolution of the potential barriers of phase transition of MoS2, MoSe2 and MoTe2

Two-dimensional crystals with weak layer interactions, such as transitional metal dichalcogenides, have been a focus of research recently.

Adsorption and diffusion of Li with S on pristine and defected graphene

The formation of Li_nS and diffusion of Li-ions on defected graphene as an encapsulation layer for Li–S batteries.

Controlling phase transition for single-layer MTe2 (M = Mo and W): modulation of the potential barrier under strain

Using first-principles DFT calculations, the pathway and the energy barrier of phase transition between 2H and 1T′ have been investigated for MoTe₂ and WTe₂ monolayers.

Real-space observation of strong metal-support interaction: state-of-the-art and what's the next

The real-space resolving of the encapsulated overlayer in the well-known model and industry catalysts, ascribed to the advent of dedicated transmission electron microscopy, enables us to probe novel nano/micro architecture chemistry for better application, revisiting our understanding of this key issue in heterogeneous catalysis. In this review, we summarize the latest progress of real-space observation of SMSI in several well-known systems mainly covered from the metal catalysts (mostly Pt) supported by the TiO2 , CeO2 and Fe3 O4 . As a comparison with the model catalyst Pt/Fe3 O4 , the industrial catalyst Cu/ZnO is also listed, followed with the suggested ongoing directions in the field.

Transformation of electronic properties and structural phase transition from HfN to Hf3N4

We report investigation of the structural phase transition and electronic properties of Hf(1-x)N (0 ⩽ x ⩽ 0.25) using first principles calculations. The defective NaCl-type structure with Hf vacancies (V(Hf)) is found to be stable over a large phase region. Hf3N4 with the Zr3N4-type structure is only stable in relative small region and readily destabilized when the stoichiometric ratio of N to Hf deviates from 4/3. The electronic and optic properties of Hf(1-x)N are controlled by the concentration of V(Hf). The full depletion of excess free electrons from Hf atoms results in the structural phase transition of Hf3N4.

Cu₄ Cluster Doped Monolayer MoS₂ for CO Oxidation

The catalytic oxidation of CO molecule on a thermodynamically stable Cu₄ cluster doped MoS₂ monolayer is investigated by density functional theory (DFT) where the reaction proceeds in a new formation order of COOOCO* (O₂* + 2CO* → COOOCO*), OCO* (COOOCO* → CO₂ + OCO*), and CO₂ (OCO* → CO₂) desorption with the corresponding reaction barrier values of 0.220 eV, 0.370 eV and 0.119 eV, respectively. Therein, the rate-determining step is the second one. This low barrier indicates high activity of this system where CO oxidation could be realized at room temperature (even lower). As a result, the Cu₄ doped MoS₂ could be a candidate for CO oxidation with lower cost and higher activity without poisoning and corrosion problems.

How important is the {103} plane of stable Ge2 Sb2 Te5 for phase-change memory?

Closely correlating with {200} plane of cubic phase, {103} plane of hexagonal phase of Ge(2)Sb(2)Te(5) plays a crucial role in achieving fast phase change process as well as formation of modulation structures, dislocations and twins in Ge(2)Sb(2)Te(5). The behaviors of {103} plane of hexagonal phase render the phase-change memory process as a nanoscale shape memory.

Structural stability of single-layer MoS2 under large strain

Out-of-plane relaxation can introduce MoS(2) in flexible electronic/optoelectronic devices, while under larger strain it is possible to frustrate the structure of MoS(2). On the basis of first-principle calculations, the ideal tensile stress strain relations and failure mechanism of single-layer MoS(2) structure under large strain is investigated. The instability of phonon modes near the K point results in the decrease of tensile stress under large strain. The relative out-of-plane movement of Mo atoms is found to contribute to the mechanism of the soft phonon mode.

Toward structural/chemical cotailoring of phase-change Ge-Sb-Te in a transmission electron microscope

Ge2Sb2Te5, as the prototype material for phase-change memory, can be transformed from amorphous phase into nanoscale rocksalt-type GeTe provided with an electron irradiation assisted by heating to 520°C in a 1250 kV transmission electron microscope. This sheds a new light into structural and chemical cotailoring of materials through coupling of thermal and electrical fields.

Pressure evolution of the potential barriers for transformations of layered BN to dense structures

The energy barrier and stacking way from layered BN to dense phase under pressure.

Phase stability, hardness and bond characteristics of ruthenium borides from first-principles

The structural stability, elastic modulus, hardness and electronic structure of RuB_2−x (0 ≤ x ≤ 2) borides are systematically investigated using a first-principles approach.

First-principle calculations on the structural stability and electronic properties of superhard BxCy compounds

With first-principle calculations, we studied the structural stability and electronic properties of the BxCy compounds based on three kinds of phases including diamond-like, C20-like and B15-like phases. The C20-like structure B8C12 is found to be a new stable structure with relatively low formation energy in middle boron concentration and is expected to be synthesized experimentally. Combined with a microscopic model, the Vickers hardness of the different configurations of BxCy compounds is analyzed with the change of boron concentration. It is found that the hardness of the B-C system has a decreasing trend with the increase of boron concentration. In addition, all the structures have metallic properties, except B12C3 and B14C. With the analysis of Mulliken bond population and charge distribution, the bonds with high electron density and short bond length have an important contribution to the hardness in the B-C system, while the effect of metallicity to hardness can be ignored.

Adsorption of single Li and the formation of small Li clusters on graphene for the anode of lithium-ion batteries

We analyzed the adsorption of Li on graphene in the context of anodes for lithium-ion batteries (LIBs) using first-principles methods including van der Waals interactions. We found that although Li can reside on the surface of defect-free graphene under favorable conditions, the binding is much weaker than to graphite and the concentration on a graphene surface is not higher than in graphite. At low concentration, Li ions spread out on graphene because of Coulomb repulsion. With increased Li content, we found that small Li clusters can be formed on graphene. Although this result suggests that graphene nanosheets can conceivably have a higher ultimate Li capacity than graphite, it should be noted that such nanoclusters can potentially nucleate Li dendrites, leading to failure. The implications for nanostructured carbon anodes in batteries are discussed.

Interaction between graphene and the surface of SiO2

The interaction between graphene and a SiO(2) surface has been analyzed with first-principles DFT calculations by constructing the different configurations based on α-quartz and cristobalite structures. The fact that single-layer graphene can stay stably on a SiO(2) surface is explained based on a general consideration of the configuration structures of the SiO(2) surface. It is found that the oxygen defect in a SiO(2) surface can shift the Fermi level of graphene down which opens up the mechanism of the hole-doping effect of graphene adsorbed on a SiO(2) surface observed in a lot of experiments.

Adsorption and diffusion of Li on pristine and defective graphene

With first-principles DFT calculations, the interaction between Li and carbon in graphene-based nanostructures is investigated as Li is adsorbed on graphene. It is found that the Li/C ratio of less than 1/6 for the single-layer graphene is favorable energetically, which can explain what has been observed in Raman spectrum reported recently. In addition, it is also found that the pristine graphene cannot enhance the diffusion energetics of Li ion. However, the presence of vacancy defects can increase the ratio of Li/C largely. With double-vacancy and higher-order defects, Li ion can diffuse freely in the direction perpendicular to the graphene sheets and hence boost the diffusion energetics to some extent.

Raman spectroscopic determination of the length, strength, compressibility, Debye temperature, elasticity, and force constant of the C-C bond in graphene

From the perspective of bond relaxation and bond vibration, we have formulated the Raman phonon relaxation of graphene, under the stimuli of the number-of-layers, the uni-axial strain, the pressure, and the temperature, in terms of the response of the length and strength of the representative bond of the entire specimen to the applied stimuli. Theoretical unification of the measurements clarifies that: (i) the opposite trends of the Raman shifts, which are due to the number-of-layers reduction, of the G-peak shift and arises from the vibration of a pair of atoms, while the D- and the 2D-peak shifts involve the z-neighbor of a specific atom; (ii) the tensile strain-induced phonon softening and phonon-band splitting arise from the asymmetric response of the C(3v) bond geometry to the C(2v) uni-axial bond elongation; (iii) the thermal softening of the phonons originates from bond expansion and weakening; and (iv) the pressure stiffening of the phonons results from bond compression and work hardening. Reproduction of the measurements has led to quantitative information about the referential frequencies from which the Raman frequencies shift as well as the length, energy, force constant, Debye temperature, compressibility and elastic modulus of the C-C bond in graphene, which is of instrumental importance in the understanding of the unusual behavior of graphene.

Electron scattering and electrical conductance in polycrystalline metallic films and wires: impact of grain boundary scattering related to melting point

For electrical conductance in polycrystalline metallic films and wires, the reflection coefficient of electrons at grain boundaries is explored and found to be proportional to the square root of the melting points of metals. As validated by available experimental results, this exploration enables classical models to take an essential role in theoretically predicting the electrical conductance of low-dimensional metals. One thus sees that the mechanism dominating the suppression of electrical conductance is transformed from the surface scattering into the grain boundary scattering as the ratio of film thickness (or wire diameter) to grain size rises. Furthermore, the impact of grain boundary scattering becomes less important for metals with lower melting points.

The effects of electronic field on the atomic structure of the graphene/α-SiO(2) interface

The atomic structure of the graphene/α-SiO(2)(0001) interface under electric field F with different intensities is studied using the density functional theory method. Simulation results indicate that the atomic structure of the graphene/α-SiO(2)(0001) interface has only a slight change under the condition of F≤0.02 au. However, the distance between substrate and graphene d(0) changes evidently. Moreover, as F reaches 0.03 au, the formation of a C-O covalent bond on the interface is present, which would destroy the excellent electronic properties of graphene. Thus, there exists a maximum for F in application of the graphene.

Synthesis and field electron emission properties of hybrid carbon nanotubes and nanoparticles

Hybrid ZnO-carbon nanotubes as well as nanodiamond-carbon nanotubes were synthesized via a straightforward process of plasma enhanced chemical vapor deposition. For the former, ZnO nanoparticles were instantly coated on the tube surface in the final growing process of carbon nanotubes, while for the latter diamond nanoparticles were grown using pretreatment of a silicon substrate with Ni(NO(3))(2)·6H(2)O/Mg(NO(3))(2)·6H(2)O alcohol solution prior to deposition and a high H(2)/CH(4) gas flow ratio in the deposition process. The morphology and microstructure of the obtained hybrid materials were characterized by transmission electron microscopy. Both hybrid ZnO-carbon nanotubes and nanodiamond-carbon nanotubes exhibited excellent field emission properties.

Field emission properties of N-doped capped single-walled carbon nanotubes: A first-principles density-functional study

The geometrical structures and field emission properties of pristine and N-doped capped (5,5) single-walled carbon nanotubes have been investigated using first-principles density-functional theory. The structures of N-doped carbon nanotubes are stable under field emission conditions. The calculated work function of N-doped carbon nanotube decreases drastically when compared with pristine carbon nanotube, which means the enhancement of field emission properties. The ionization potentials of N-doped carbon nanotubes are also reduced significantly. The authors analyze the field emission mechanism in terms of energy gap between the lowest unoccupied molecular orbital and the highest occupied molecular orbital, Mulliken charge population, and local density of states. Due to the doping of nitrogen atom, the local density of states at the Fermi level increases dramatically and donor states can be observed above the Fermi level. The authors' results suggest that the field emission properties of carbon nanotubes can be enhanced by the doping of nitrogen atom, which are consistent with the experimental results.

Comparison of the survival of human biopsied embryos after cryopreservation with four different methods using non-transferable embryos

BACKGROUND

The standard embryo cryopreservation method is still less than optimal for biopsied embryos. The aim of this study was to compare the survival of biopsied embryos cryopreserved with four different methods using non-transferable embryos.

METHODS

Abnormal embryos from one or three pronuclei and spare embryos of grade 3 and 4 were used for this study. Non-biopsied embryos were cryopreserved using the standard method as control. Biopsied embryos were cryopreserved using four methods as follows: standard method, modified freezing method, modified thawing method and vitrification. Blastomere survival and blastulation of frozen-thawed embryos were compared between the different methods.

RESULTS

The proportion of embryos with > or = 50% blastomere survival and total blastomere survival rate of biopsied embryos were significantly higher with vitrification than the other three methods. Both the modified freezing and modified thawing methods had significantly higher embryo survival and total blastomere survival rates than standard methods. However, there was no significant difference in blastulation of surviving embryos in all the five groups.

CONCLUSIONS

Non-transferable embryos derived from clinical IVF/ICSI are useful for evaluation of the optimal freezing procedures for biopsied embryos. Vitrification increases the survival rate of human biopsied embryos above standard and modified cryopreservation methods.

Dynamic Isomer Shift in Charge-Ordering Manganite Y0.5Ca0.5MnO3: Mössbauer Spectroscopy Study

We report the Mössbauer spectroscopy study on Fe-doped charge-ordering manganite Y(0.5)Ca(0.5)MnO(3). The dynamic isomer shift is observed for charge-ordering manganite, and its origin may be due to strong Jahn-Teller distortions in Y(0.5)Ca(0.5)MnO(3), causing electron-phonon coupling. The evolution of Mössbauer spectroscopy as a function of temperature shows two different phases with significantly different quadrupole splitting values below the charge-ordering transition temperature. This confirms that there exist two different Mn sites (i.e., Mn(3+) and Mn(4+) ions), which can be identified by the microscopic method of Mössbauer spectroscopy.