镜界

这是一片与世无争的乐土，不沾世俗，不惹尘埃。银潭，并非一汪潭水，而是深藏在贵州山坳中的一个侗族村寨，富有诗意。一条清澈的小溪穿寨而过，在阳光的照耀下，涓涓的溪流反射出一片银光，银潭之名由此而来。

Ketamine and midazolam sedation for pediatric gastrointestinal endoscopy in the Arab world

AIM:To evaluate the safety and effectiveness of intravenous ketamine-midazolam sedation during pediatric endoscopy in the Arab world.METHODS:A retrospective cohort study of all pediatric endoscopic procedures performed between 2002-2008 at the shared endoscopy suite of King Abdullah University Hospital,Jordan University of Science & Technology,Jordan was conducted.All children were > 1 year old and weighed > 10 kg with American Society of Anesthesiologists class 1 or 2.Analysis was performed in terms of sedation-related complications(desaturation,respiratory distress,apnea,bradycar-dia,cardiac arrest,emergence reactions),adequacy of sedation,need for sedation reversal,or failure to complete the procedure.RESULTS:A total of 301 patients(including 160 males) with a mean age of 9.26 years(range,1-18 years) were included.All were premedicated with atropine;and 79.4%(239/301) had effective and uneventful sedation.And 248(82.4%) of the 301 patients received a mean dose of 0.16 mg/kg(range,0.07-0.39) midazolam and 1.06 mg/kg(range,0.31-2.67) ketamine,respectively within the recommended dosage guidelines.Recommended maximum midazolam dose was exceeded in 17.6% patients [34 female(F):19 male(M),P = 0.003] and ketamine in 2.7%(3 M:5 F).Maximum midazolam dose was more likely to be exceeded than ketamine(P < 0.001).Desaturation occurred in 37(12.3%) patients,and was reversible by supplemental oxygen in all except 4 who continue to have desaturation despite supplemental oxygen.Four(1.3%) patients had respiratory distress and 6(2%) were difficult to sedate and required a 3rd sedative;12(4%) required reversal and 7(2.3%) failed to complete the procedure.None developed apnea,bradycardia,arrest,or emergence reactions.CONCLUSION:Ketamine-midazolam sedation appears safe and effective for diagnostic pediatric gastrointestinal endoscopy in the Arab world for children aged > 1 year and weighing > 10 kg without co-morbidities.

Improving performance of recycled aggregate concrete with superfine pozzolanic powders

Phosphorous slag （PHS）, ground granulated blast-furnace slag （GGBS） and fly ash （FA） were used as replacements of Portland cement to modify the microstruc^xe of recycled aggregate concrete （RAC）. A new manufacturing method named ＂W3T4＂ was proposed to improve the performances of interracial transition zone （ITZ） between recycled aggregate and mortar. The mechanical properties and the durability of RAC were tested, which show that this new manufacturing method improves the properties of RAC, and the GGBS with finest size makes a great contribution to the performance of RAC due to its better filling effect and much earlier pozzolanic reaction. Combined with GGBS, the effects of PHS on the retardation of setting time can be alleviated and the synergistic effect helps to make a more compact RAC. For the RAC with 25% of the recycled aggregate （RA） replacement and 10% PHS ＋ 10% GGBS additives, the compressive strength increases by 25.4%, but the permeability decreases by 64.3% with respect to the reference concrete made with nature aggregates. The micro-mechanisms of these improvements were investigated by the scanning electron microscope （SEM）. The SEM images show that the new manufacturing method, adding superfine pozzolanic powders and super-plasticizer benefits, makes a much denser ITZ in RAC.

Time for the world to move beyond the percutaneous endoscopic gastrostomy

Percutaneous endoscopic gastrostomy (PEG) is a proven feeding tube,just as the nasogastric tube is proven to be able to deliver enteral nutrition.For long-term use,both patient and caregiver want neither.What is desired is the LOOPPEG? 3G tube,more secure than the PEG,and less risky to change than the nasogastric tube.Future clinical research should focus on this high-comfort low-risk tube.

Effect of a novel three-step aging on strength, stress corrosion cracking and microstructure of AA7085

The influence of a novel three-step aging on strength, stress corrosion cracking(SCC) and microstructure of AA7085 was investigated by tensile testing and slow strain rate testing combined with transmission electron microscopy(TEM). The results indicate that with the increase of second-step aging time of two-step aging, the mechanical properties increase first and then decrease, while the SCC resistance increases. Compared with two-step aging, three-step aging treatment improves SCC resistance and the strength increases by about 5%. The effects of novel three-step aging on strength and SCC resistance are explained by the role of matrix precipitates and grain boundary precipitates, respectively.

Novel high magnification zoom laser beam expander

A novel high magnification zoom laser beam expander is proposed originally. The zoom part and fixed part of the beam expander both adopt spherical lens and the compensation part comprising a spherical surface and an aspherical surface. The structure parameters were given by using geometry optics.The zoom characteristic and image quality were also analyzed.The results show that the magnification of the beam expander can be adjusted continuously from 3 to 20. Compared with other congener spherical zoom system,the beam expander has the advantages of high magnification,compact structure,high beam quality and high transmission efficiency.The novel expander can be used in many fields effectively.

Consensus control for multi-agents in a non-rectangular bounded space: algorithmand experiments

Aiming for the coordinated motion and cooperative control of multi-agents in a non-rectangular bounded space, a velocity consensus algorithm for the agents with double- integrator dynamics is presented. The traditional consensus algorithm for bounded space is only applicable to rectangular bouncing boundaries, not suitable for non-rectangular space. In order to extend the previous consensus algorithm to the non- rectangular space, the concept of mirrored velocity is introduced, which can convert the discontinuous real velocity to continuous mirrored velocity, and expand a bounded space into an infinite space. Using the consensus algorithm, it is found that the mirrored velocities of multi-agents asymptotically converge to the same values. Because each mirrored velocity points to a unique velocity in real space, it can be concluded that the real velocities of multi-agents also asymptotically converge. Finally, the effectiveness of the proposed consensus algorithm is examined by theoretical proof and numerical simulations. Moreover, an experiment is performed with the algorithm in a real multi-robot system successfully.

Mechanical properties of 3D carbon/carbon composites by nanoindentation technique

Nanoindentation tests were conducted to investigate the near-surface mechanical properties of the individual components(fiber and matrix) for three-dimensional reinforced carbon/carbon composites(3D C/C).Optical microscope and polarizing light microscope were used to characterize the microstructure of 3D C/C.The microscopy results show that large number of pores and cracks exist at both bundle/matrix interface and pitch carbon matrix.These defects have important effect on the mechanical behavior of 3D C/C.The in situ properties for components of 3D C/C were acquired by nanoindentation technique.Relative to the matrix sample,the fiber samples have more larger values for modulus,stiffness and hardness.However,there is no significant difference of modulus and stiffness among fiber samples with different directions.

Effects of whisker surface treatment on microstructure and properties of Al_(18)B_4O_(33w)/6061Al composites

6061Al matrix composites reinforced by ZnO-coated Al18B4O33 whiskers were fabricated by a semi-solid mechanical stirring technique.The effects of ZnO coating on interfacial reaction between whiskers and matrix and the tensile properties of the composites were investigated.Tensile tests on composites were performed at room temperature,and microstructures were observed by scanning electron microscopy(SEM).The results show that the surface treatment of whiskers could reduce interfacial reaction effectively,improve the wettability between whiskers and matrix and enhance the tensile properties of the composites obviously.In addition,semi-solid stirring parameters were also under preliminary study.The stirring parameters were determined by the distribution of whiskers in the composites.The composites with homogeneously distributed whiskers were fabricated by semi-solid stirring at 610 ℃ for 30 min.

Intelligent Tracking Telescope Using Embedded Microcontrollers

This paper presents the design and implementation of the embedded microcontrollers within a telescope control system. The design objectives of the overall system are to automatically find light emitting objects at night within a user specified area, to track a light emitting object for a user specified time given the initial position of the object, and to allow the user access to these functions through a graphical user interface. The embedded system is used to provide a communication link between the graphical user interface and system hardware, to provide angle data processing for a dual axis accelerometer, to provide data processing for an electronic compass, and to provide pulse outputs for the step and direction inputs of three stepper motor drives. This paper will describe the design, implementation, and results of each of these objectives.

Sorption and Diffusion Behavior of Carbon Dioxide into Poly（l-lactic acid） Films at Elevated Pressures

Equilibrium sorption amount, desorption diffusion coefficients and sorption diffusion coefficients of CO2 in poly（l-lactic acid） （PLLA） films at elevated pressures were determined by the gravimetric method, in which the Fick＇s diffusion model was applied to analyze both the desorption and sorption processes. The equilibrium sorption amount of CO2 in PLLA increased with lowering temperature and elevating pressure at the temperature range from 40 to 60 ℃ and pressure from 10^4 to 2x10^4 kPa. Desorption diffusion coefficients were greatly influenced by the equilibrium sorption amount, and they were in the same order of magnitude as the sorption diffusion coefficients. The scan electron microscope （SEM） photos demonstrated that there was no foaming phenomenon of the PLLA film during desorption and sorption processes. The XRD spectra implied that the crystalline degree of PLLA film decreased after CO2 processing. It was concluded that PLLA polymer could be well swollen and plasticized by supercritical CO2.

Chemical Solution Deposition of YBa2Cu3O7 Films on YSZ （100） Substrates

We report the epitaxial growth of YBCO （YBa2Cu3O7） films on YSZ （Yttria-stabilized Zirconia） （100） substrates by chemical solution deposition. The precursor solution was prepared by dissolving stoichiometric amounts of acetates of Y（OOCCH3）3·4H2O, Ba（OOCCH3）2 and Cu（OOCCH3）·2H2O in an aqueous solution of oxalic acid （H2C2O4） and following the sol-gel route. This solution was directly dripped onto YSZ （100） substrates with the help of a Fisher pipette. To form the YBCO film, the sample was crystallized by annealing at 860 ℃ for 12 h in an oxidizing atmosphere. The characterization was performed by XRD （X-ray diffraction） analysis which revealed high intensity （001） reflections and denoted that most of the grains were c-axis oriented. Randomly oriented grains and other phases such as Y2BaCuO5 and CuO were also detected. The superconducting YBCO phase is demonstrated from the susceptibility versus temperature measurements which indicate a superconducting critical temperature ≈ 90 K. In addition, a surface morphology analysis was performed by optical microscopy and atomic force microscopy which revealed an average roughness of 0.2197 μm.

Laser beam induced current microscopy and photocurrent mapping for junction characterization of infrared photodetectors

For non-destructive optical characterization, laser beam induced current(LBIC) microscopy has been developed into as a quantitative tool to examine individual photodiodes within a large pixel array. Two-dimensional LBIC microscopy, also generally called photocurrent mapping(PC mapping), can provide spatially resolved information about local electrical properties and p-n junction formation in photovoltaic infrared(including visible light) photodetectors from which it is possible to extract material and device parameters such as junction area, junction depth, diffusion length, leakage current position and minority carrier diffusion length etc. This paper presents a comprehensive review of research background, operating principle, fundamental issues, and applications of LBIC or PC mapping.

Interface of transition metal oxides at the atomic scale

Remarkable phenomena arise at well-defined heterostructures, composed of transition metal oxides, which is absent in the bulk counterpart, providing us a paradigm for exploring the various electron correlation effects. The functional properties of such heterostructures have attracted much attention in the microelectronic and renewable energy fields. Exotic and unexpected states of matter could arise from the reconstruction and coupling among lattice, charge, orbital and spin at the interfaces. Aberration-corrected scanning transmission electron microscopy （STEM） is a powerful tool to visualize the lattice structure and electronic structure at the atomic scale. In the present study some novel phenomena of oxide heterostructures at the atomic scale are summarized and pointed out from the perspective of electron microscopy.

Optical visualization of MoS_2 grain boundaries by gold deposition

The grain boundaries（GBs） in continuous films or domains of MoS2 are vital to its optical and electrical properties. Almost all previous approaches for GBs visualization are based on microscopy and spectroscopy and only effective for domains with less than several micrometers in size. Here we report a simple method for the visualization of large GBs in MoS2 surface by optical microscope. Gold was deposited on the MoS2 grown by chemical vapor deposition,and then the GBs could be observed by optical microscope.Upon gold deposition on MoS2, the entire GBs of large-area MoS2 were clearly visualized using this method. To verify the result, the GBs were also characterized via scanning electron microscopy, transmission electron microscopy and atomic force microscopy. It showed the small particles of gold were clustered together on GBs, which had a larger binding energy than the inner regions. The method is universal and allows for the nondestructive identification of the GBs in any two dimensional materials with large area.

Progress of electrode/electrolyte interfacial investigation of Li-ion batteries via in situ scanning probe microscopy

The electrode/electrolyte interface plays a cri- tical role in the performance of a Li-ion battery. In view of the dynamic and complex nature of the interface, in situ research approaches can provide valuable information of interfacial phenomena during battery operation. In situ scanning probe microscopy （SPM） is a powerful technique used for the interfacial investigation of the Li-ion batteries. The versatile SPM techniques and their various operation modes have been utilized to measure the morphology and other properties of the electrode interface at high resolu- tion. Herein, we discuss the related SPM techniques to study the topography, mechanics and electrochemistry re- search of electrodes. Recent progresses of in situ SPM research on the electrode/electrolyte interface are summa- rized. Finally, the outlook of the technique is discussed.

In-situ TEM study of the dynamic behavior of the graphene-metal interface evolution under Joule heating

The dynamic behavior of the interface between few layer graphene(FLG) and tungsten metal tips under Joule heating has been studied by in-situ transmission electron microscopy(TEM) method. High-resolution and real-time observations show the tungsten tip ‘swallow' carbon atoms of the FLG and ‘spit' graphite shells at its surface. The tip was carbonized to tungsten carbide(WC, W_2 C and WC_x) after this process. A carbon diffusion mechanism has been proposed based on the diffusion of carbon atoms through the tungsten tip and separation from the surface of the tip. After Joule heating, the initial FLG-metal mechanical contact was transformed to FLG-WCx-W contact, which results in significant improvement on electrical conductivity at the interface.

Segmental dynamics near the chain end of polystyrene in its ultrathin films:a study by single-molecule fluorescence de-focus microscopy

Rotational motion of fluorophores chemically attached to polystyrene chain-ends in ultra-thin films on solid substrates was studied by single-molecule fluorescence de-focus microscopy.The collective feature of the rotational motion was found and evidenced by the sharp change of the population of fluorophores undergoing rotational motion within a very narrow temperature range(named as the changing temperature,T c).The T c value was found to depend on film thickness and interfacial chemistry and the variation of the T c value is also dependent on the molecular weight of the polymer.The results demonstrate that the spatial confinement effect enhances the segmental mobility near the polymer chain-ends while the interfacial attraction restricts the segmental motion inside the thin film.

Photoactivity of titanium dioxide/carbon felt composites prepared with the assistance of supercritical carbon dioxide: Effects of calcination temperature and supercritical conditions

TiO2-coated carbon felt(TCF)composite catalysts have been prepared via a supercritical treatment of titanium tetraisopropoxide(TTIP)as the precursor.The physical properties of the catalysts were characterized by means of thermogravimetric and differential thermal analysis(TG–DTA),X-ray diffraction(XRD),fluorescence spectroscopy,scanning electron microscopy (SEM),and BET surface areas techniques.The photocatalytic activities of the materials were evaluated using the degradation of Congo red(CR)as a probe reaction.All the composites showed much higher photocatalytic activity than commercial P25 due to significant synergistic effects.Reused TCF retained high photocatalytic activity for degradation of CR.The photocatalytic efficiency in CR degradation was found to be strongly dependent on the TiO2-coating ratio and calcination temperature.A possible mechanism for the enhanced reactivity involves shuttling of electrons from TiO2 particles to the carbon felt(CF)as a result of an optimal arrangement in TCF that stabilizes charge separation and reduces charge recombination.In addition to the significant synergistic effects,the abundant spaces between adjacent carbon fibers allow UV light to penetrate into the felt-like photocatalyst to a considerable depth,so that a three-dimensional environment is available for the photocatalytic reaction.