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Guangxi, a province in southwestern China, has the second highest reported number of HIV/AIDS cases in China. This study aimed to develop an accurate and effective model to describe the tendency of HIV and to predict its incidence in Guangxi. HIV incidence data of Guangxi from 2005 to 2016 were obtained from the database of the Chinese Center for Disease Control and Prevention. Long short-term memory (LSTM) neural network models, autoregressive integrated moving average (ARIMA) models, generalised regression neural network (GRNN) models and exponential smoothing (ES) were used to fit the incidence data. Data from 2015 and 2016 were used to validate the most suitable models. The model performances were evaluated by evaluating metrics, including mean square error (MSE), root mean square error, mean absolute error and mean absolute percentage error. The LSTM model had the lowest MSE when the N value (time step) was 12. The most appropriate ARIMA models for incidence in 2015 and 2016 were ARIMA (1, 1, 2) (0, 1, 2)12 and ARIMA (2, 1, 0) (1, 1, 2)12, respectively. The accuracy of GRNN and ES models in forecasting HIV incidence in Guangxi was relatively poor. Four performance metrics of the LSTM model were all lower than the ARIMA, GRNN and ES models. The LSTM model was more effective than other time-series models and is important for the monitoring and control of local HIV epidemics.
The properties of the acoustic modes are sensitive to magnetic activity. The unprecedented long-term Kepler photometry, thus, allows stellar magnetic cycles to be studied through asteroseismology. We search for signatures of magnetic cycles in the seismic data of Kepler solar-type stars. We find evidence for periodic variations in the acoustic properties of about half of the 87 analysed stars. In these proceedings, we highlight the results obtained for two such stars, namely KIC 8006161 and KIC 5184732.
Ten leading varieties of winter wheat released during 1950–2009 in North China were tested in a free-air temperature increase (FATI) facility. The FATI facility mimicked the local air temperature pattern well, with an increase of 1·1 °C in the daily mean temperature. For all the tested varieties, warming caused a significant reduction in the total length of wheat growth period by 5 days and especially in the pre-anthesis period, where it was reduced by 9 days. However, warming increased wheat biomass production and grain yield by 8·4 and 11·4%, respectively, on an average of all the tested varieties. There was no significant difference in the warming-led reduction in the entire growth period among the tested varieties. Interestingly, the warming-led increments in biomass production and grain yield increased along with the variety release year. Significantly higher warming-led increases in post-anthesis biomass production and 1000-grain weight were found in the new varieties compared to the old ones. Meanwhile, a significant improvement in plant productivity was noted due to wheat breeding during the past six decades, while no significant difference in the length of entire growth period was found among the varieties released in different eras. The results demonstrate that historical wheat breeding might have enhanced winter wheat productivity and adaptability through exploiting the positive effects rather than mitigating the negative impacts of warming on wheat growth in North China.
To identify important risk factors for recurrent methicillin-resistant Staphylococcus aureus (MRSA) to assist clinicians in identifying high-risk patients for continued surveillance and follow-up.
In this retrospective cohort study, we examined patients with MRSA bacteremia at 122 Veterans Affairs medical facilities from January 1, 2003, through December 31, 2010. Recurrent MRSA bacteremia was identified by a positive blood culture result from 2 to 180 days after index hospitalization discharge. Subset analyses were performed to evaluate risk factors for early-onset (2–60 days after discharge) and late-onset (61–180 days after discharge) recurrence. Risk factors were evaluated using Cox proportional hazards regression.
Of 18,425 patients, 1,159 (6.3%) had recurrent MRSA bacteremia. The median time to recurrence was 63 days. Longer duration of index bacteremia, increased severity of illness, receipt of only vancomycin, community-acquired infection, and several comorbidities were risk factors for recurrence. Congestive heart failure, hypertension, and rheumatoid arthritis/collagen disease were risk factors for early-onset but not late-onset recurrence. Geographic region and cardiac arrhythmias were risk factors for late-onset but not early-onset recurrence.
Risk factors for recurrent MRSA bacteremia included comorbidities, severity of illness, duration of bacteremia, and receipt of only vancomycin. Awareness of risk factors may be important at patient discharge for implementation of quality improvement initiatives including surveillance, follow-up, and education for high-risk patients.
To evaluate the accuracy of real-time polymerase chain reaction (PCR) for Clostridium difficile–associated disease (CDAD) detection, after hospital CDAD rates significantly increased following real-time PCR initiation for CDAD diagnosis.
Hospital-wide surveillance study following examination of CDAD incidence density rates by interrupted time series design.
Large university-based hospital.
Hospitalized adult patients.
CDAD rates were compared before and after real-time PCR implementation in a university hospital and in the absence of physician and infection control practice changes. After real-time PCR introduction, all hospitalized adult patients were screened for C. difficile by testing a fecal specimen by real-time PCR, toxin enzyme-linked immunosorbent assay, and toxigenic culture.
CDAD hospital rates significantly increased after changing from cell culture cytotoxicity assay to a real-time PCR assay. One hundred ninety-nine hospitalized subjects were enrolled, and 101 fecal specimens were collected. C. difficile was detected in 18 subjects (18%), including 5 subjects (28%) with either definite or probable CDAD and 13 patients (72%) with asymptomatic C. difficile colonization.
The majority of healthcare-associated diarrhea is not attributable to CDAD, and the prevalence of asymptomatic C. difficile colonization exceeds CDAD rates in healthcare facilities. PCR detection of asymptomatic C. difficile colonization among patients with non-CDAD diarrhea may be contributing to rising CDAD rates and a significant number of CDAD false positives. PCR may be useful for CDAD screening, but further study is needed to guide interpretation of PCR detection of C. difficile and the value of confirmatory tests. A gold standard CDAD diagnostic assay is needed.
High-redshift quasars are unique probes of the evolution of supermassive black holes and the intergalactic medium at the end of the epoch of reionization. We present the optical spectra of eight new z ~ 6 quasars selected from the Panoramic Survey Telescope & Rapid Response System 1 (Pan-STARRS1). Details of the selection strategy can be found in Bañados et al. (2014). With this work we increase the number of known quasars at z < 5.7 by more than 10%. The quasars discovered here span a large range of luminosities (19.6 ≤ zP1 ≤ 21.2) and are remarkably heterogeneous in their spectral features: half of them show bright emission lines whereas the other half show weak or no Lyα emission line. We find a larger fraction of weak–line emission quasars than in lower redshift studies, although still based on low number statistics, this may imply that the quasar population could be more diverse than previously thought.
In this work, we study CdTe thin films used in CdTe/CdS solar cells with a substrate configuration, which allows for better control in forming the junction, and the possibility for using flexible non-transparent substrates. We studied the properties of CdTe films grown at 450° and 550°C, with and without a CuxTe layer, and before and after CdCl2 treatment. We analyzed the structural and electro-optical properties using electron backscatter diffraction (EBSD), cathodoluminescence (CL) and X-ray diffraction (XRD), and investigated how the film structure, stress, and defect structure changes with the different growth conditions.
The solid oxide membrane (SOM) electrolysis process has been successfully tested on a laboratory scale to produce silicon directly from silica in a cost-effective and eco-friendly way. A one-end-closed yttria-stabilized zirconia (YSZ) tube was employed to separate a molten salt containing dissolved silica from a liquid metal anode placed inside the YSZ tube. When an applied electric potential between a liquid tin cathode in the molten salt and the anode exceeds the dissociation potential of silica, oxygen ions are transported out of the molten salt through the YSZ membrane and oxidized at the anode while the silicon cations in the flux are reduced to silicon on the surface of the liquid tin cathode. A potentiodynamic scan (PDS) was performed to determine the dissociation potential of silica in the molten salt system. Electrolysis was performed at 1.05 V for 8 hours. The presence of high-purity silicon crystals on the surface of liquid tin cathode was confirmed by scanning electron microscopy (SEM) and electron dispersive X-ray spectroscopy (EDS).
Given the important role of the default mode network (DMN) in cognitive function and the well-known neurocognitive deficit in schizophrenia, it is intriguing to examine systematically the relationship between neurocognitive dysfunction and aberrant intrinsic activities, and also functional connectivity, of the DMN in patients with schizophrenia.
First-episode, treatment-naive patients with schizophrenia (FES) (n = 115) and healthy controls (n = 113) underwent resting-state functional magnetic resonance imaging (fMRI) scans and neurocognitive tests. Intrinsic neural activities evaluated by using the fragment amplitude of low-frequency fluctuations (fALFF) and the resting-state functional connectivity assessed by seed-based correlational analysis were compared between patients and controls. Aberrant intrinsic activities and DMN connectivity in patients were then correlated to neurocognitive performance and clinical symptoms.
Compared to controls, patients with FES showed decreased fALFF in the bilateral medial prefrontal cortex (MPFC) and the orbitofrontal cortex (OFC), and increased fALFF in the bilateral putamen. Increased functional connectivity with the DMN was observed in the left insula and bilateral dorsolateral PFC (DLPFC) in patients with FES. In patients, aberrant fALFF in the bilateral OFC were correlated with cognitive processing speed; fALFF in the left OFC and right putamen were correlated with the clinical factors excited/activation and disorganization; and increased DMN functional connectivity in the left insula was correlated with the clinical factors positive, excited/activation, disorganization and neurocognitive deficit in the domain of sustained attention.
These associations between neurocognitive dysfunction and aberrant intrinsic activities, and also functional connectivity, of the DMN in patients with schizophrenia may provide important insights into the neural mechanism of the disease.
This study aimed to investigate the relationship between hepatitis B virus (HBV) covalently closed circular DNA (cccDNA) in the ovary and vertical transmission of HBV. HBV DNA and HBV cccDNA were assayed in the ovaries of 33 pregnant women who were positive for HBV DNA. The HBVM (HBV markers, including HBsAg, HBsAb, HBeAg, HBeAb, HBcAb) level and the HBV DNA content in peripheral blood of infants were measured. The overall positive rate of HBV DNA and HBV cccDNA in samples was 51·52% (17/33). The intrauterine infection rate of the infants was 12·12% (4/33). When HBV DNA and HBV cccDNA were both positive, the intrauterine infection rate of infants was significantly higher than when they were both negative (P<0·05). Levels of HBV cccDNA and the rate of positive samples were significantly higher in mothers with infants with intrauterine infection than in those without (P<0·01 and P<0·05, respectively). HBV can infect the human ovary and may transmit to the filial generation via the ovum.
Bulk Mg-Cu-Y-Al alloys, prepared by casting into a wedge-shaped copper mold, have been studied in the as-prepared, the supercooled liquid, and the crystalline states. In the as-prepared state x-ray diffraction of sub-millimeter sized regions were performed using a focused x-ray beam. The phase composition of the cross section as well as of the surface of the wedge-shaped specimen was investigated as a function of position. The cooling history of the alloy was experimentally determined and compared to results of a control-volume finite-difference modelling study. The experimentally determined and the calculated cooling rates were correlated with the observed amorphous/crystalline structure. The transition from an amorphous to a crystalline state was followed by x-ray diffraction studies as a function of time at specific temperatures in the region between the glass transition and the crystallization temperature. Based on these results a temperature-time-phase diagram was constructed. The dependence of external pressure on the crystallisation temperature was investigated by in situ high-temperature and high- pressure x-ray powder diffraction by using synchrotron radiation. The investigations form the basis for a selection of the optimum temperature in the supercooled liquid region for performing deformation/shaping of the Mg-based alloys.
X-ray topography(XRT) and EBIC have been used to study the generation of misfit dislocations in strained layer structures. Two structures studied were GaAs1−yPy(y=0.15) film and SLS consisting of InxGa1−xAs(x=0.08) and GaAs1−y Py(y=0.16) layers. XRT and EBIC techniques gave consistent results for the behavior of dislocations. The value of the critical thickness for generation of misfit dislocations in the former was found to be few times larger than that in the latter. EBIC image showed that a SLS lattice matched to the substrate is effective in reducing defects originating from the substrate.
High quality YBCO films have been grown on GaAs-based substrates via depositing MgO epitaxial buffer layers prior to YBCO growth. The critical temperature of the best YBCO film, Tc(0) was 87K and Jc>6.7×104 A/cm2 at 77K. The MgO buffer layers are usually  oriented along the normal of GaAs (100) substrates with full-width-half-maximum (FWHM) of rocking curve varying from 1–3 degree. We found that the uniformity and quality of MgO buffer layers are very sensitive to the pre-deposition preparation of GaAs-based substrates. Nonuniform MgO buffer layers are often obtained on those substrates prepared by wet chemical processing. Reproducible, controlled formation of the MgO buffer layer was achieved using an antimony passivation scheme, after molecular beam epitaxial (MBE) growth of the desired structure of the substrate.
Low temperature deposition of dielectric thin films is more and more used in very largescale integrated (VLSI) circuits. For this purpose, distributed electron cyclotron resonance (DECR) plasma appears to be a promising tool. The most interesting feature of this recent plasma is the high ion density (≈1011 cm−3) associated with low electronic temperature (2–3eV) and low energy species (20–30 eV). The purpose of this study is to discuss the effects of the reactant gas mixture composition (O2sol;SiH4) and the rf substrate bias power on the physical, chemical and electrical properties of DECR SiO2 films deposited at floating temperature (<100°C). Under optimum deposition conditions, the films show excellent characteristics, comparable to those obtained with thermal oxides grown at 850–1050°C.
Schottky diodes were fabricated by evaporating metal thin layers on p-Si1-xGex by cryogenic processing. The cryogenic processing, with substrate temperature cooled to as low as 77K (LT), has been successfully used to enhance metal/III-V semiconductor Schottky barrier height. The electrical characteristics of the diodes were investigated by current-voltage (IV) and current-temperature (I-T) measurements. In order to study the effect of silicide formation on diode characteristics, furnace annealing was performed in nitrogen atmosphere at 450°C and 550°C, respectively. Two kinds of samples with gemanium composition x of 0.17 and 0.20 were used. The electrical characteristics showed the barrier height фB decreased with the increase of the gemanium composition. The annealing temperatures up till to 550°C did not affect the I-V characteristics at room temperature, however, the conduction mechanism showed obvious difference comparing to the as-deposited diodes by I-V-T analysis. For Pd as Schottky metal, very similar results were obtained for the LT as-deposited diodes and the ordinary room temperature (RT) deposited diodes after 550° annealing, they both showed thermionic emission dominated conduction mechanism.
Electrical properties of Al/p-Sil-xGex Schottky contacts were investigated. The Sil-xGexstrained layers were grown by using Rapid Thermal Process/Very Low Pressure-Chemical Vapor Deposition. It was found that Schottky barrier height decreased with increasing Ge fraction. The decrement is in accordance with the decrement of the bandgap of the strained Sil-xGex. The Fermi level at the interface is pinned at about 0. 43eV below the conduction band. The influence of strain relaxation for SiGe alloy layers and the Si cap layers on the properties of Schottky contacts were also investigated.
The simulation and experiment results of delta-doped AlGaN/GaN heterostructure field-effect transistors (HFETs) with the incorporation of highly-resistive AlN epilayer are reported. The high quality AlN epilayer is used as the dislocation filter for the HFET structure growth, and the high resistivity of AlN also removes the parasitic conduction related with the GaN bulk buffer. Delta doping can reduce gate leakage, further more, our simulation and growth results demonstrate that delta-doping in the barrier is more effective than uniform doping scheme to increase the sheet electron density. The influence of spacer layer thickness on the electron mobility and sheet electron density is also presented. The DC characterization of the fabricated devices shows our structure has a very high performance with a maximum current ∼ 1 A/mm.