Four cases of severe acute respiratory syndrome (SARS) that occurred from December 16, 2003, to January 8, 2004, in the city of Guangzhou, Guangdong Province, China, were investigated. Clinical ...specimens collected from these patients were tested by provincial and national laboratories in China as well as members of the World Health Organization SARS Reference and Verification Laboratory Network in a collaborative effort to identify and confirm SARS-associated coronavirus (SARS-CoV) infection. Although SARS-CoV was not isolated from any patient, specimens from three patients were positive for viral RNA by reverse transcription-polymerase chain reaction assay, and all patients had detectable rises in SARS-CoV-specific antibodies. This study shows the effectiveness of a collaborative, multilaboratory response to diagnose SARS.
Neural stem cells (NSCs) are currently considered powerful candidates for cell therapy in neurodegenerative disorders such as Parkinson's disease. However, it is not known when and how NSCs begin to ...differentiate functionally. Recent reports suggest that classical neurotransmitters such as acetylcholine (Ach) are involved in the proliferation and differentiation of neural progenitor cells, suggesting that neurotransmitters play an important regulatory role in development of the central nervous system (CNS). We have shown by calcium imaging and immunochemistry that proliferation and differentiation are enhanced by M2 muscarinic Ach receptors (mAchR) expressed on the NSC surface and on their neural progeny. Moreover, atropine, an mAchR antagonist, blocks the enhancement and inhibits the subsequent differentiation of NSCs. Further understanding of this neural-nutrition role of Ach might elucidate fetal brain development, the brain's response to injury, and learning and memory.
A novel process was used to fabricate Ce-TZP/CePO4 composite ceramics, namely, infiltrating CePO4 liquid precursor into a Ce-TZP porous ceramic. A sintered Ce-TZP ceramic preform with 35 vol% open ...pore volume was developed by adding 30 vol% graphite. Ce-TZP/CePO4 composites containing different CePO4 contents were obtained by infiltration and pyrolysis cycles. The machinability and mechanical properties of these materials were investigated. It was shown that the composites can be cut and drilled using conventional tungsten carbide metal-working tools. Machinabilities were compared by measuring the normal grinding force. Ce-TZP/CePO4 composites containing 2.3 to 7.5 vol% CePO4 have good machinability and outstanding mechanical properties. The relation between microstructure and mechanical properties of the materials is discussed. 6 refs.
A systematic theoretical and experimental study on a 35-GHz 45-kV third-harmonic gyrotron with a permanent magnet system is presented in this paper. A complex cavity with gradual transition and a ...diode magnetron injection gun (MIG) are employed in the gyrotron. A self-consistent field nonlinear theoretical investigation and numerical simulation for electron beam interaction with RF fields are given. The diode MIG is simulated numerically utilizing our code in detail. The permanent magnet system provided the maximum axial magnetic field of about 4.5 kG in the cavity region of the gyrotron. The Ka band third-harmonic complex cavity gyrotron with a permanent magnet system has been designed, constructed, and tested. A pulse output power of 147.3 kW was obtained at a beam voltage of 45 kV with beam current of 32.2 A, corresponding to an efficiency of 10.2%.
As an important parameter for critical load calculation and soil acidification simulation, weathering rates of soils in China were studied using different methods of calculation. The approaches used ...were the mass balance approach, the soil mineralogical classification, the total analysis correlation, the PROFILE model, the MAGIC model and a simulated leaching experiment. Since chemical weathering of secondary minerals usually plays a much more important role in neutralizing the long-term acidification of soils in China than that of parent material, soil mineralogy rather than parent rock/material type, which is regarded as the most suitable factor representing weathering rates in Europe, should be adopted as the basis for soil classification. The weathering rate assigned to each soil should also be corrected when the effect of temperature is considered. Due to the variation in experimental conditions, the weathering rates of soils from laboratory experiment may be difficult to compare with field determined rates, and should be adjusted by pH and percolation rate. The comparison of various methods in this study shows that the weathering rates of soils estimated by the PROFILE model coincide well with those from other independent methods such as the dynamic modeling by MAGIC and the modified leaching experiment. The weathering rates were very low (usually lower than 1.0 kEq·ha
−1·year
−1) for Allites (including Latosol, Lateritic Red Earth, Red Earth, Yellow Earth and Yellow-Brown Earth) in south China and Silalsols (consisting of Dark Brown Forest Soil, Black Soil and Podzolic Soil) in northeast China, and very high for Alpine Soils, Desert Soils and Pedocals in west China. The content of weatherable minerals in soil is the most important factor in determining the spatial distribution of weathering rate in China, while the difference in temperature may be the reason why the weathering rate of soil in northeast China was lower than that in southeast China.
Searches for electron antineutrino, muon neutrino, and muon antineutrino disappearance driven by sterile neutrino mixing have been carried out by the Daya Bay and MINOS+ collaborations. This Letter ...presents the combined results of these searches, along with exclusion results from the Bugey-3 reactor experiment, framed in a minimally extended four-neutrino scenario. Significantly improved constraints on the \(\theta_{\mu e}\) mixing angle are derived that constitute the most stringent limits to date over five orders of magnitude in the sterile mass-squared splitting \(\Delta m^2_{41}\), excluding the 90% C.L. sterile-neutrino parameter space allowed by the LSND and MiniBooNE observations at 90% CL\(_s\) for \(\Delta m^2_{41}<5\,\)eV\(^2\).Furthermore, the LSND and MiniBooNE 99% C.L. allowed regions are excluded at 99% CL\(_s\) for \(\Delta m^2_{41}\) \(<\) 1.2 eV\(^2\).
The design and process capability of board-level assembly of ceramic ball grid array (CBGA) packages with respect to their reliabilities were investigated. Two types of FEM models were built for ...elastic and elastic–plastic–creep analyses, respectively. The effect of PCB material, PCB thickness, and the thickness of ceramic substrate on solder joint deformation was discussed. It was shown that the variation in assembly process would cause the highest stress in the joints change by 10% from the mean value. The failure location and fatigue life under the temperature cycling condition were also studied. It was concluded that the prediction was close to the first failure in the test and would be seen as a conservative estimation.
A common and fatal problem of the low-toxicity gelcasting is the low flexural strength of green bodies. The objective of this study was to solve the problem by introducing water-soluble ...polyvinylpyrrolidone (PVP) polymer to the monomer system. The low-toxicity monomer and ceramic powder were selected as methacrylamide (MAM) and alumina, respectively. Flexural strength of green bodies was improved nearly by 30%, with no significant change in the property of sintered bodies when the addition amount of PVP is 2.8
wt.%. Influence of PVP content on rheological properties of alumina suspensions, their gelation time, and the microstructure of green and sintered bodies were investigated.
This paper presents the development of a mini-electrochemical detector for microchip electrophoresis. The small size (3.6 x 5.0 cm2, W x L) of the detector is compatible with the dimension of the ...microchip. The use of universal serial bus (USB) ports facilitates installation and use of the detector, miniaturizes the detector, and makes it ideal for lab-on-a-chip applications. A fixed 10 M ohm feedback resistance was chosen to convert current of the working electrode to voltage with second gain of 1, 2, 4, 8, 16, 32, 64 and 128 for small signal detection instead of adopting selectable feedback resistance. Special attention has been paid to the power support circuitry and printed circuit board (PCB) design in order to obtain good performance in such a miniature size. The working electrode potential could be varied over a range of +/-2.5 V with a resolution of 0.01 mV. The detection current ranges from -0.3 x 10(-7) A to 2.5 x 10(-7) A and the noise is lower than 1 pA. The analytical performance of the new system was demonstrated by the detection of epinephrine using an integrated PDMS/glass microchip with detection limit of 2.1 microM (S/N = 3).
We report a fundamentally new growth mechanism for single crystalline nanobelts, namely, the growth and coalescence of nanobranches. The growth process of the nanobelts includes four typical steps ...such as nucleation and growth of the stem, nucleation and growth of the nanobranches at the expense of the stem, widening and geometrical coalescence of the nanobranches, and finally having nanobelts with perfect structure. The unique widening growth process of the nanobranches is apparently driven by the lattice distortion within the surface area of the stem. The continuous geometrical coalescence between the neighbored branches leads to the formation of the beltlike structures.
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