Search

The purpose of this study was to investigate the phenomenon of burnout in the Singaporean coaching population. Semi-structured interviews were conducted with four Singaporean coaches with h...

Background and purpose Fatal familial insomnia (FFI) is an autosomal dominant disease due to the D178N mutation of PRNP gene coupling with homozygous methionine (Met) at codon 129. It is generally considered that D178N mutation cases with 129 M/M homozygotes present as FFI, and 129 V/V as genetic CJD. However, the frequency of 129 Met alleles in Chinese population is much higher than that in Caucasians. This study aims to investigate the clinical features and genetic characteristics of Chinese D178N mutants in this genetic context. Methods We reviewed the clinical and genetic features of seven D178N patients. The clinical data, genetic data, electroencephalogram (EEG), brain magnetic resonance imaging (MRI), polysomnography (PSG), CSF 14-3-3 protein examinations of the seven patients were analyzed. Results The genotypes at codon 129 were all M/M. Four of the seven cases reported positive family history. Four patients were more likely the CJD phenotype and three were FFI phenotype according to the core clinical features. No major differences were found on the EEG, CSF 14-3-3 protein, and PSG presentations between this study and western studies. Novel neuroimaging findings were two patients had typical neuroimaging abnormalities of CJD and frontotemporal dementia, respectively. Conclusions Unlike the western populations, the diverse phenotypical presentations of D178N mutants were not simply determined by the 129 genotypes in Chinese. The underlying modifying factors for phenotypical variations warrant further investigations. For those with atypical clinical and imaging features, genetic testing was important for final diagnosis.

About 30,000 astronomical photographic plates were digitised between 2012–2017 with a special digitising machine that has high precision in both astrometry and photometry. All the images from the plates, together with plate information and measured coordinates of all the objects on the plates, have been stored in the Chinese Virtual Observatory.

The use of GaMnAs as the emitter of an internal-photoemission (IPE) photodetector is studied. As a result of significantly high concentration of holes, GaMnAs-based IPE detector resembles a Schottky-barrier detector, which has the higher absorption and thus enhanced spectral response by comparing with the previously reported $p$ -type GaAs/AlGaAs detectors. A GaMnAs/AlGaAs detector is expected to fully cover the 3–5- $\mu \text{m}$ range of detection. The theoretical value of the responsibility is 0.0133 A/W at 3.5 $\mu \text{m}$ .

Two kinds of charge trapping memory device with Au/Zr0.5Hf0.5O2(ZHO)/SiO2/p-Si and Au/Ba0.6Sr0.4TiO3(BST)/Zr0.5Hf0.5O2/SiO2/p-Si structure were fabricated and investigated. The double BST/ZHO films exhibit a larger memory window of 7.36 V under ±14 V sweeping voltages in its C–V curve and the device has good charge retention properties with only small charge loss of ∼ 5 % after more than 10 4 s . The good characteristics are attributed to the inter-diffusion between BST and ZHO where more deep defect sites were created after RTA treatment, which provides high potential barriers for the trapped charges to tunnel back to the silicon substrate. Furthermore, the nanocrystal in the BST layer increases the tunneling barrier of tunneling current into the gate and effectively restrains the leakage of storage charge from blocking layer, which improves the charge retention characteristic.

A 43° rotated Y-cut LiNbO3 (LN) single-crystal thin film coated with a bottom electrode and a Mo/Ti Bragg reflector is successfully transferred onto the 4-in. LN wafer substrate by means of crystal-ion-slicing (CIS) technique and benzocyclobutene bonding method. The multilayer film is crack-free, and the Mo/Ti reflector shows good acoustic reflection efficiency. A thin film bulk acoustic wave resonator based on the Mo/Ti Bragg reflector and the LN thin film (LN-BAW) is prepared, and the properties are further analyzed. The results indicate that the LN-BAW provides a large Kt2 of ∼16.63% and the Q-factor and figure-of-merit of the LN-BAW reach 183 and 30.4, respectively.

43°Y-cut lithium niobate (LiNbO3, LN) single-crystalline thin films, which are integrated with two types of Bragg reflectors of W/SiO2 and Mo/SiO2, respectively, are fabricated by means of the crystal-ion-slicing technique. Crack-free LN thin films are obtained when the Mo/SiO2 reflector is adopted, while crumples take place when the LN thin film is combined with W/SiO2. Moreover, solidly-mounted-type thin film bulk acoustic wave resonators (LN-SMRs) based on the single-crystalline LN film and Bragg reflector layers of Mo/SiO2 are prepared and characterized. The results indicate that the LN thin film combined with the Mo/SiO2 reflector has good thin film quality, and keff2 of the LN-SMR reaches 20%.

As the magnetic storage density approaches 1 TB/in2, a grand challenge is looming as how to read/write such a huge amount of data within a reasonable time. In this study, we demonstrate femtosecond demagnetization in 10-nm epitaxially grown Fe thin films by applying low-energy femtosecond laser pulses. We used time-resolved pump-probe Magneto Kerr Effect spectroscopy to record ultrafast laser induced demagnetization and its recovery. The demagnetization time was found to be 70 fs from the time-resolved hysteresis loops. The time scale is much shorter than the phonon thermalization time. Our results show that the demagnetization can be completed before electron-phonon equilibration is achieved, and therefore indicate the feasibility of ultrafast optical control of demagnetization responses for next generation femtosecond-switching magnetic storage devices.

Natural ventilation was provided by tall vertical shafts such as solar chimney while designing some green buildings. For buildings with a tall vertical shaft located in very cold countries, measured pressure difference due to stack effect was up to 300 Pa. Air motion induced by stack effect would give adequate ventilation flow rate. However, stack effect would also give adverse effect if not utilized properly in this green design. Smoke would spread faster to other parts of the building in an accidental fire. Therefore, estimations of stack pressure by simple hydrostatic equation used to be criticized in performance-based design. Further studies are required and will be justified by scale model experiments in this article. Stack effect in a vertical shaft was studied experimentally by a model shaft of size 0.05 × 0.05 m2 and height 2.0 m. Air temperature inside the model was kept at constant values above outdoor by wounding hot electric wires. Vertical air temperature profiles inside and outside of the model at different heights were measured. Measured air pressure difference profiles between indoor and outdoor were then compared with those estimated from the air temperature difference. Results were then applied to justify stack pressure estimations by the hydrostatic models. From this study, hydrostatic equations are confirmed to be acceptable for studying stack pressure in tall vertical shafts.

Free-carrier effects in a p-type semiconductor including the intra-valence-band and inter-valence-band optical transitions are primarily responsible for its optical characteristics in infrared. Attention has been paid to the inter-valence-band transitions for the development of internal photoemission (IPE) mid-wave infrared (MWIR) photodetectors. The hole transition from the heavy-hole (HH) band to the spin-orbit split-off (SO) band has demonstrated potential applications for 3–5 μm detection without the need of cooling. However, the forbidden SO-HH transition at the Γ point (corresponding to a transition energy Δ0, which is the split-off gap between the HH and SO bands) creates a sharp drop around 3.6 μm in the spectral response of p-type GaAs/AlGaAs detectors. Here, we report a study on the optical characteristics of p-type GaAs-based semiconductors, including compressively strained InGaAs and GaAsSb, and a dilute magnetic semiconductor, GaMnAs. A model-independent fitting algorithm was used to derive the dielectric function from experimental reflection and transmission spectra. Results show that distinct absorption dip at Δ0 is observable in p-type InGaAs and GaAsSb, while GaMnAs displays enhanced absorption without degradation around Δ0. This implies the promise of using GaMnAs to develop MWIR IPE detectors. Discussions on the optical characteristics correlating with the valence-band structure and free-hole effects are presented. Published version

The aim of this study was to investigate the association between MMP3 rs3025058 and MMP9 rs3918242 polymorphisms and the development of ischemic stroke in a Chinese population. Between May 2013 and January 2015, 335 patients with ischemic stroke and 335 health control subjects were enrolled in this study. The MMP3 rs3025058 and MMP9 rs3918242 polymorphisms were analyzed using polymerase chain reaction coupled with restriction fragment length polymorphism. By multivariate logistic regression analysis, the CC genotype of MMP9 rs3918242 was shown to be associated with a significantly increased risk of ischemic stroke when compared with the TT genotype [OR (95%CI) = 5.47 (2.64-12.38)]. The TC+CC genotype of MMP9 rs3918242 was furthermore found to be associated with an elevated risk of ischemic stroke in higher BMI individuals [OR (95%CI) = 1.81 (1.03-3.22)]. The findings of this study suggest that the MMP9 rs3918242 polymorphism is associated with an elevated risk of ischemic stroke and that this gene polymorphism interacts with BMI in the risk of ischemic stroke.

Several studies have examined the association between excision repair cross-complementation group 1 (ERCC1) C8092A and ERCC2 Lys751Gln polymorphisms and glioma risk, but the results have been inconclusive. We conducted a meta-analysis of 12 studies to determine the association between ERCC1 rs3212986 and ERCC2 rs13181 genes and glioma susceptibility. We searched for relevant studies in both Chinese and English in PubMed, Web of Science, Cochrane Library, and EMBASE through January 1, 2014, and identified 3939 cases and 5407 controls. The results showed that individuals carrying the ERCC1 rs3212986 AA genotype had higher risk of glioma compared with the CC genotype, with a pooled odds ratio = 1.29, 95% confidence interval = 1.07-1.55. Subgroup analysis showed that the ERCC1 rs3212986 AA genotype was significantly associated with an increased risk of glioma in the Chinese population (odds ratio = 1.37, 95% confidence interval = 1.07-1.55), but no association in Caucasian Chinese. No significant association was observed between ERCC2 rs13181 polymorphisms and glioma risk. The results of our meta-analysis strongly suggested that the ERCC1 rs3212986 polymorphism was associated with a higher susceptibility to glioma, particularly in the Chinese population. Studies including a larger sample size and more specified information regarding pathological types of glioma are needed to confirm our results.

In this article the dynamic behavior of clamped-clamped micromachined mechanical resonators working at a frequency of 150kHz was characterized by electrostatic excitation and detection via both capacitive coupling and optical methods. The experimental results by optical measurement show that this system behaved very much like a simple harmonic oscillator at low actuation levels while significant nonlinearity was observed at higher actuation levels. The nonlinearity identified as “spring softening” type occurred when the product of the dc bias voltage and the ac driving voltage exceeded 0.04V2. Dependence of resonance frequency on dc bias voltage was investigated and the experimental results are in agreement with theoretical predictions. This work also demonstrated that optical detection is much less susceptible to parasitic interference than motion detection via capacitive coupling. Therefore, optical techniques will yield better characterization of the mechanical properties of the resonators.

Tantalum pentoxide (Ta"2O"5) deposited by pulsed DC magnetron sputtering technique as the gate dielectric for 4H-SiC based metal-insulator-semiconductor (MIS) structure has been investigated. A rectifying current-voltage characteristic was observed, with the injection of current occurred when a positive DC bias was applied to the gate electrode with respect to the n type 4H-SiC substrate. This undesirable behavior is attributed to the relatively small band gap of Ta"2O"5 of around 4.3eV, resulting in a small band offset between the 4H-SiC and Ta"2O"5. To overcome this problem, a thin thermal silicon oxide layer was introduced between Ta"2O"5 and 4H-SiC. This has substantially reduced the leakage current through the MIS structure. Further improvement was obtained by annealing the Ta"2O"5 at 900^oC in oxygen. The annealing has also reduced the effective charge in the dielectric film, as deduced from high frequency C-V measurements of the Ta"2O"5/SiO"2/4H-SiC capacitors.

In this study, Zr0.5Hf0.5O2 films were fabricated on Si substrate and were annealed at different temperatures by rapid thermal annealing (RTA) process. The charge trapping memory devices based on Zr0.5Hf0.5O2/SiO2/Si simple structure were investigated in detail. The memory device annealing at 690 °C shows the best property with a memory window of 5.6 V under ±12 V sweeping voltages in its capacitance-voltage curve and a better retention property. The high resolved transmission electron microscopy shows the generated SiO2 working as tunneling layer after RTA process, whose thickness increases with the rise of temperature. Combined with the TEM results, the photoluminescence spectrum and in situ angle resolved photoemission spectroscopy results further verify that oxygen vacancies and inter-diffusion layer also play a crucial role in charge trapping performance. This work provides direct insights for the charge trapping mechanisms based on high-k Zr0.5Hf0.5O2 films devices.

As the existing traffic information system based on the fixed traffic information center needs high cost for construct, and the other traffic information system based on inter vehicle communication pays more attention to safe driving information but pays less attention to traffic congestion information, especially for the traffic congestion information in the road network. This paper studies and puts forward a pattern for automatic traffic information service which realizes the function of automatic collection and dynamic transmission of traffic information in the road network on the basis of VANET, and with no need for fixed traffic information center. According to this pattern, we build the models for automatic collecting, integrating and processing, transmitting of traffic information, and automatic generating and dynamic updating of traffic information which covers the whole road network. Finally, in this paper, we also carry out traffic simulation for these models, analyze and evaluate rationality of these models and transmission effect.

Numerical simulations of a clean room were conducted by software FDS5.3 using large-eddy simulation (LES). A computational fluid dynamics (CFD) model was first verified by comparing computational results with results of reduced scale clean room fire tests. The temperature near the ceiling round the fire location with three sizes acetone liquid fire were then studied for a typical full-scale clean room. Results show that the temperature near the ceiling is varied mainly due to the heat release rate (HRR). When the fire area is 0.5 m (meter) × 0.5 m, the excess temperature, near the ceiling in a horizontal distance 4.5 m from the fire centre, is below 50 K (kelvin) during the whole process; when the fire area is 2.0 m × 0.5 m, the temperatures above the ambient (300K), near the ceiling in a horizontal distance respectively 0.5 m and 2.5 m from the fire centre, get 50 K almost at the same time. However, under air ventilation, the temperature next to ceiling decreases fast with distance from the fire, so the radius of the smoke spread along the ceiling becomes small.

Smoke movement during fire in a large teaching building without sprinkler was simulated by large eddy simulation (LES) model. Several fire scenarios were considered to show the smoke movement in vertical and horizontal direction. It is found that the lower storey the fire location is, the more dangerous the people inside are for a multi-storey building. Also we can find when the smoke spreads along the corridor and encounters an atrium, it will accumulate largely in the atrium. In addition, the reasonable application of fire shutter was discussed. Simulated results show that simultaneous releasing the fire shutters of the fire storey and above can efficiently control smoke to spread horizontally.

MnxGa films with high perpendicular anisotropy, coercivity and energy product have great application potential in ultrahigh-density perpendicular recording, permanent magnets, spin-transfer-torque memory and oscillators, magneto-resistance sensors and ferromagnetic metal/semiconductor heterostructure devices. Here we present a comprehensive diagram of effective magnetism-tailoring of perpendicularly magnetized MnxGa films grown on III-V semiconductor GaAs by using molecular-beam epitaxy for the first time, by systematically investigating the wide-range composition and detailed post-growth annealing effects. We show that the (001)-orientated MnxGa films with L10 or D022 ordering could be crystallized on GaAs in a very wide composition range from x=0.76 to 2.6. L10-ordered MnxGa films show robust magnetization, high remanent ratio, giant perpendicular anisotropy, high intrinsic and extrinsic coercivity, and large energy product, which make this kind of material favorable for perpendicular magnetic recording, high-performance spintronic devices and permanent magnet applications. In contrast, D022-ordered films exhibit lower perpendicular anisotropy and weaker magnetism. Post-growth annealing MnxGa films studies reveal high thermal-stability up to 450 oC, and effective tailoring of magnetic properties can be realized by prolonging annealing at 450 oC. These results would be helpful for understanding this kind of material and designing new spintronic devices for specific practical applications.

A two-color time-resolved Kerr rotation spectroscopy system was built, with a femtosecond Ti:sapphire laser and a photonic crystal fiber, to study coherent spin transfer processes in an InGaAs/GaAs quantum well sample. The femtosecond Ti:sapphire laser plays two roles: besides providing a pump beam with a tunable wavelength, it also excites the photonic crystal fiber to generate supercontinuum light ranging from 500 nm to 1600 nm, from which a probe beam with a desirable wavelength is selected with a suitable interference filter. With such a system, we studied spin transfer processes between two semiconductors of different gaps in an InGaAs/GaAs quantum well sample. We found that electron spins generated in the GaAs barrier were transferred coherently into the InGaAs quantum well. A model based on rate equations and Bloch-Torrey equations is used to describe the coherent spin transfer processes quantitatively. With this model, we obtain an effective electron spin accumulation time of 21 ps in the InGaAs quantum well.