Computer assisted testing of spoken English: A study to evaluate the SFLEP college English oral test in China

Since its opening up to the outside world in the 1980s and the introduction of economic reforms that have involved engagement with the global economy and wider community, the Chinese government has become determined to promote the teaching and learning of English as a foreign language among its citizens. In particular, it has mandated the study of English for all college and university students and has made the passing of the College English Test (CET) at Band 4 level a requirement for obtaining a degree. With some ten million candidates annually (and rising) CET Band 4 has become the world’s largest language test administered nationwide (Jin and Yang, 2006). In a deliberate attempt to harness the backwash effect of examinations on teaching and learning, the Ministry of Education has insisted that all college and university students (generally when in their second year of study) must sit the CET Band 4 written papers that test reading, writing and listening skills in English. Aimed largely, but not exclusively, at those students majoring in English, there is also a higher level, Band 6, CET available

Transfer-Free Development of Graphene-on-Silicon Heterojunction Solar Cells

Two-dimensional nanomaterials (2DNs) due to their broadband absorption (graphene) and high absorption coefficient (MoS2 or WS2) are attractive for optoelectronics including solar cells. Recent advances in 2DNs-based photovoltaics is based on interfacing 2DNs with conventional bulk 3D semiconductors to build a new class of 2D/3D heterojunction solar cells. Currently, such 2D/3D heterojunction solar cell devices are fabricated via mechanical/chemical transfer of 2D layers onto 3D bulk semiconductors, which poses challenges for large-scale integrations. In this project, transfer-free, large-area graphene/n-silicon (G/n-Si) heterojunction solar cells are developed via chemical vapor deposition (CVD). The directly-grown graphene films are characterized via combined spectroscopic (Raman and XPS) and microscopic (FESEM) techniques. Several CVD process optimizations have been made to understand the growth kinetics of graphene on n-Si surfaces. A power conversion efficiency of 1.3% is achieved for G/n-Si heterojunction solar cells with silver nanoparticles as plasmonics centers. Factors such as: structural quality, quantum opto-plasmonics affecting the performances of these new generation photovoltaics will be discussed

Additional file 1: of The impact of body mass index on short-term surgical outcomes after laparoscopic hepatectomy, a retrospective study

Available data. (XLSX 107 kb

Disturbance observer-based autonomous landing control of unmanned helicopters on moving shipboard

In this paper, the autonomous landing control issue on moving shipboard is investigated for unmanned helicopters subject to disturbances. The issue is studied by stabilizing the error system of the helicopter and the shipboard. The landing process is divided into two phases, i.e., homing phase, where a hierarchical double-loop control scheme is developed such that the helicopter is forced to hover synchronously at a certain altitude over the shipboard, and landing phase, where a composite landing control scheme is proposed such that the helicopter lands vertically on the shipboard in synchronization with its attitudes. The velocity and acceleration information of the shipboard as well as lump disturbances is estimated through joint state and disturbance observers. The estimates are then incorporated into the baseline feedback controller, formulating composite active anti-disturbance landing control schemes. A continuous terminal sliding mode control method is proposed for the feedback controller design, which not only effectively mitigates the chattering of the control action, but also simplifies the design process of the controller. Numerical simulations demonstrate the effectiveness and superiorities of the proposed control schemes

Finite-time path following control for small-scale fixed-wing UAVs under wind disturbances

By integrating the finite time control technique and finite-time disturbance observers together, the finite-time three-dimensional path following control problem for small-scale fixed-wing UAVs subject to external wind disturbances is investigated in this paper. The external wind disturbances are estimated through finite-time disturbance observers and the estimates are then incorporated into the finite-time feedback controller such that a composite control scheme is proposed. Under the proposed control scheme, the closed-loop system possesses not only faster convergence rate but also stronger disturbance rejection ability and better robustness, which is the main contribution of the paper. The effectiveness and superiorities of the proposed composite control scheme are demonstrated by numerical simulations. </p

Palladium-Catalyzed C‑2 Selective Olefination of Thiazoles

A highly efficient protocol for C2 selective alkenylation of electron-deficient thiazoles is developed. High C2 position selectivity for alkenylation products is achieved at a neutral environment, and a possible pathway of oxidative alkenylation is discussed. This methodology provides a simple way to construct a 2-alkenyl-thiazole moiety

Exposure to Mutagenic Disinfection Byproducts Leads to Increase of Antibiotic Resistance in <i>Pseudomonas aeruginosa</i>

Bacterial antibiotic resistance (BAR) in drinking water has become a global issue because of its risks on the public health. Usually, the antibiotic concentrations in drinking water are too low to select antibiotic resistant strains effectively, suggesting that factors other than antibiotics would contribute to the emergence of BAR. In the current study, the impacts of mutagenic disinfection byproducts (DBPs) on BAR were explored, using four typical DBPs: dibromoacetic acid, dichloroacetonitrile, potassium bromate, and 3-chloro-4-(dichloromethyl)-5-hydroxy-2­(5H)-furanone (MX). After exposure to DBPs, resistances to 10 individual antibiotics and multiple antibiotics were both raised by various levels, norfloxacin and polymycin B resistances were enhanced even greater than 10-fold compared with control. MX increased the resistance most observably in the selected DBPs, which was consistent with its mutagenic activity. The resistant mutants showed hereditary stability during 5-day culturing. The increase of BAR was caused by the mutagenic activities of DBPs, since mutation frequency declined by adding ROS scavenger. Mutagenesis was further confirmed by sequencing of the related genes. Our study indicated that mutagenic activities of the selected DBPs could induce antibiotic resistance, even multidrug resistance, which may partially explain the lack of agreement between BAR and antibiotic levels in drinking water

Visualization1.mp4

This visualization shows the formation and growth of multiple octahedral microcrystals during the photochemical etching of n-type GaAs. Here, we placed a camera in the conjugate plane of the digital projector photochemical etching setup to observe the surface of the sample while the etching is in progress. Images were captured at 26 frames per second and averaged for 1 second. The video is being re-played at 30x speed. For the etching, we used 4:1:80 H2SO4: H2O2: H2O and the light that was projected was a 600 micron large white circle. The etching was done for 20 minutes. The circle appears to shrink in size with time because as the etching proceeds, the edges of the circle do not remain flat and thus light does not get reflected vertically. The microcrystals are the blackish blobs that grow in size, eventually forming into diamond-like shapes

TOX stimulated MF cell proliferation and invasion through AKT phosphorylation.

<p>(A) Western blot assays showed that LY294002 can inhibited AKT phosphorylation. The expression of p-AKT was normalized to GAPDH. (B) Western blot assays showed that overexpression of TOX stimulated AKT phosphorylation. The expression of p-AKT was normalized to GAPDH. (C) The proliferative role of TOX overexpression was largely blocked by LY294002, an AKT inhibitor, in MyLa cells were transfected with TOX vector, control or not transfected or TOX vector and LY294002. (D) The invasive role of TOX overexpression was largely blocked by LY294002, an AKT inhibitor, in MyLa cells were transfected with TOX vector, control or not transfected or TOX vector and LY294002. ** p<0.01, *p<0.05, and ***p<0.001.</p

UV Disinfection Induces a Vbnc State in <i>Escherichia coli</i> and <i>Pseudomonas aeruginosa</i>

The occurrence of a viable but nonculturable (VBNC) state in bacteria may dramatically underestimate the health risks associated with drinking water. Therefore, the potential for UV treatment to induce a VBNC state in <i>Escherichia coli</i> and <i>Pseudomonas aeruginosa</i> was investigated. UV disinfection effectively reduced the culturability of <i>E. coli</i> and <i>P. aeruginosa</i>, with the destruction of nucleic acids demonstrated using <i>gad</i>A long gene fragment qPCR amplification. Following UV radiation, copy numbers for the high transcriptional levels of the 16S rRNA gene varied insignificantly in both strains, confirming results from plate counting assays indicating that VBNC states were induced in both strains. Furthermore, the virulence genes <i>gadA</i> and <i>oprL</i> remained highly expressed, suggesting that the VBNC bacteria still displayed pathogenicity. Propidium monoazide qPCR indicated that cell membranes remained intact even at a UV dose of 300 mJ/cm². The RT-qPCR results after UV and chlorine treatments in <i>E. coli</i> were significantly different (8.41 and 5.59 log units, respectively), further confirming the induction of VBNC bacteria induced by UV radiation. Finally, resuscitation was achieved, with <i>E. coli</i> showing greater resuscitation ability than <i>P. aeruginosa</i>. These results systematically revealed the potential health risks of UV disinfection and strongly suggest a combined disinfection strategy