Polytypism and Unexpected Strong Interlayer Coupling of two-Dimensional Layered ReS2

The anisotropic two-dimensional (2D) van der Waals (vdW) layered materials, with both scientific interest and potential application, have one more dimension to tune the properties than the isotropic 2D materials. The interlayer vdW coupling determines the properties of 2D multi-layer materials by varying stacking orders. As an important representative anisotropic 2D materials, multilayer rhenium disulfide (ReS2) was expected to be random stacking and lack of interlayer coupling. Here, we demonstrate two stable stacking orders (aa and a-b) of N layer (NL, N>1) ReS2 from ultralow-frequency and high-frequency Raman spectroscopy, photoluminescence spectroscopy and first-principles density functional theory calculation. Two interlayer shear modes are observed in aa-stacked NL-ReS2 while only one interlayer shear mode appears in a-b-stacked NL-ReS2, suggesting anisotropic-like and isotropic-like stacking orders in aa- and a-b-stacked NL-ReS2, respectively. The frequency of the interlayer shear and breathing modes reveals unexpected strong interlayer coupling in aa- and a-b-NL-ReS2, the force constants of which are 55-90% to those of multilayer MoS2. The observation of strong interlayer coupling and polytypism in multi-layer ReS2 stimulate future studies on the structure, electronic and optical properties of other 2D anisotropic materials

Single-layer behavior and slow carrier density dynamic of twisted graphene bilayer

We report scanning tunneling microscopy (STM) and spectroscopy (STS) of twisted graphene bilayer on SiC substrate. For twist angle ~ 4.5o the Dirac point ED is located about 0.40 eV below the Fermi level EF due to the electron doping at the graphene/SiC interface. We observed an unexpected result that the local Dirac point around a nanoscaled defect shifts towards the Fermi energy during the STS measurements (with a time scale about 100 seconds). This behavior was attributed to the decoupling between the twisted graphene and the substrate during the measurements, which lowers the carrier density of graphene simultaneously

Phonon and Raman scattering of two-dimensional transition metal dichalcogenides from monolayer, multilayer to bulk material

Two-dimensional (2D) transition metal dichalcogenide (TMD) nanosheets exhibit remarkable electronic and optical properties. The 2D features, sizable bandgaps, and recent advances in the synthesis, characterization, and device fabrication of the representative MoS$_2$, WS$_2$, WSe$_2$, and MoSe$_2$ TMDs make TMDs very attractive in nanoelectronics and optoelectronics. Similar to graphite and graphene, the atoms within each layer in 2D TMDs are joined together by covalent bonds, while van der Waals interactions keep the layers together. This makes the physical and chemical properties of 2D TMDs layer dependent. In this review, we discuss the basic lattice vibrations of monolayer, multilayer, and bulk TMDs, including high-frequency optical phonons, interlayer shear and layer breathing phonons, the Raman selection rule, layer-number evolution of phonons, multiple phonon replica, and phonons at the edge of the Brillouin zone. The extensive capabilities of Raman spectroscopy in investigating the properties of TMDs are discussed, such as interlayer coupling, spin--orbit splitting, and external perturbations. The interlayer vibrational modes are used in rapid and substrate-free characterization of the layer number of multilayer TMDs and in probing interface coupling in TMD heterostructures. The success of Raman spectroscopy in investigating TMD nanosheets paves the way for experiments on other 2D crystals and related van der Waals heterostructures.Comment: 30 pages, 23 figure

Application of fibrin glue with bandage contact lens in pterygium surgery

AIM: To explore the efficacy of fibrin glue with bandage contact lens for pain relief after pterygium surgery performed with limbal autograft transplantation.<p>METHODS: A prospective clinical trial was carried out in 52 patients(72 eyes)operated for primary nasal pterygium. All patients were randomly divided into the fibrin glue with bandage contact lens group(experimental group, 28 cases, 38 eyes)and suture group(control group, 24 cases, 34 eyes). Autologous limbal graft taken from the superotemporal limbus was used to cover the sclera after pterygium excision under local anesthesia with 20g/L lidocaine. In experimental group, the transplant was attached to the sclera with fibrin tissue adhesive and in control group with 10-0 Virgin silk sutures. Experimental group weared bandage contact lens after surgery while the control group did not. The degree of pain after surgery was evaluated at 1, 2, 3, 5 and 7d after surgery. Follow-up was 6mo, matching degree of graft and complication such as infection, relapse, implant healing badness and subconjunctival cyst were mainly observed and recorded.<p>RESULTS: The pain index scores of the experimental group were significantly less than those of control group(all <i>P</i>=0.000). In observation period, all conjunctival autografts in both groups were successfully attached and were intact without falling off, dissolution or recurrence and there were no complications such as infection, relapse, implant healing badness and subconjunctival cyst.<p>CONCLUSION: Fibrin glue with bandage contact lens could significantly release pain response afterpterygium excision surgery

Research on a Model of Extracting Persons\u27 Information Based on Statistic Method and Conceptual Knowledge

PACLIC 21 / Seoul National University, Seoul, Korea / November 1-3, 200

Cellulose Acetate Reverse Osmosis Membranes for Desalination: A Short Review

Freshwater scarcity is a critical challenge that human society has to face in the 21st century. Desalination of seawater by reverse osmosis (RO) membranes was regarded as the most promising technology to overcome the challenge given that plenty of potential fresh water resources in oceans. However, the requirements for high desalination efficiency in terms of permeation flux and rejection rate become the bottle-neck which needs to be broken down by developing novel RO membranes with new structure and composition. Cellulose acetate RO membranes exhibited long durability, chlorine resistance, and outstanding desalination efficiency that are worthy of being recalled to address the current shortcomings brought by polyamide RO membranes. In terms of performance enhancement, it is also important to use new ideas and to develop new strategies to modify cellulose acetate RO membranes in response to those complex challenges. Therefore, we focused on the state of the art cellulose acetate RO membranes and discussed the strategies on membrane structural manipulation adjusted by either phase separation or additives, which offered anti-fouling, anti-bacterial, anti-chlorine, durability, and thermo-mechanical properties to the modified membranes associated with the desalination performance, i.e., permeation flux and rejection rate. The relationship between membrane structure and desalination efficiency was investigated and established to guide the development of cellulose acetate RO membranes for desalination. 

Bloqueio contínuo do nervo femoral guiado por ultrassom e estimulador de nervo para analgesia após artroplastia total de joelho: estudo multicêntrico, randomizado e controlado

ResumoJustificativa e objetivosAnalgesia pós‐operatória é fundamental para o exercício funcional precoce logo após a artroplastia total de joelho. O objetivo foi investigar a eficácia clínica do bloqueio contínuo do nervo femoral guiado por ultrassom e estimulador de nervo em analgesia após artroplastia total do joelho.MétodosReceberam analgesia pós‐operatória, de outubro de 2012 a janeiro de 2013, 46 pacientes, estado físico ASA I‐III, submetidos à artroplastia total de joelho. Em 22 pacientes, o bloqueio femoral contínuo foi guiado por ultrassom e estimulador de nervo para analgesia (grupo BFC); em 24 pacientes, analgesia foi administrada por via epidural (grupo ACP). Os efeitos analgésicos, efeitos colaterais, a recuperação articular e as complicações foram comparados entre os dois grupos.ResultadosÀs seis e 12 horas após a cirurgia, os escores de dor no joelho (escore EVA) durante os testes funcionais após exercício ativo e passivo foram significativamente menores no grupo BFC do que no grupo ACP. A quantidade usada de parecoxib nos pacientes do grupo BFC foi significativamente menor em comparação com o grupo ACP. Quarenta e oito horas após a cirurgia, o grau de força muscular no grupo BFC foi significativamente maior e o tempo de atividade ambulatória foi menor do que no grupo ACP. A incidência de náusea e vômito em pacientes do grupo BFC foi significativamente menor em comparação com o grupo ACP.ConclusãoO bloqueio femoral contínuo guiado por ultrassom e estimulador do nervo proporcionou melhor analgesia às seis e 12 horas, demonstrada por EVA‐R e EVA‐P. A quantidade de parecoxib também foi menor, a incidência de náusea e vômito diminuiu, a influência sobre a força muscular é comprometida e os pacientes podem fazer atividade ambulatorial sob essa condição.AbstractBackground and objectivesPostoperative analgesia is crucial for early functional excise after total knee arthroplasty. To investigate the clinical efficacy of ultrasound and nerve stimulator guided continuous femoral nerve block analgesia after total knee arthroplasty.Methods46 patients with ASA grade I–III who underwent total knee arthroplasty received postoperative analgesia from October 2012 to January 2013. In 22 patients, ultrasound and nerve stimulator guided continuous femoral nerve block were performed for analgesia (CFNB group); in 24 patients, epidural analgesia was done (PCEA group). The analgesic effects, side effects, articular recovery and complications were compared between two groups.ResultsAt 6h and 12h after surgery, the knee pain score (VAS score) during functional tests after active exercise and after passive excise in CFNB were significantly reduced when compared with PCEA group. The amount of parecoxib used in CFNB patients was significantly reduced when compared with PCEA group. At 48h after surgery, the muscle strength grade in CFNB group was significantly higher, and the time to ambulatory activity was shorter than those in PCEA group. The incidence of nausea and vomiting in CFNB patients was significantly reduced when compared with PCEA group.ConclusionUltrasound and nerve stimulator guided continuous femoral nerve block provide better analgesia at 6h and 12h, demonstrated by RVAS and PVAS. The amount of parecoxib also reduces, the incidence of nausea and vomiting decreased, the influence on muscle strength is compromised and patients can perform ambulatory activity under this condition