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Halloysite nanotubes were activated via co-calcination of halloysite and the precursors of lanthanum oxycarbonate (LO), generating reactive alumina nanoparticles and uniformly anchoring LO nanoparticles to halloysite surfaces. The resulting LO-alumina combination exhibits record-high phosphate adsorption capacity as well as excellence in adsorption selectivity and sewage phosphate removal.

A detailed geometric model for calculating the edge dislocation density through X-ray diffraction rocking curves is proposed in this study. Based on this model, we deduce a new formula to evaluate the edge dislocation density from the full-width at half-maximum values of skew symmetric rocking curves. The widely used formula proposed by Srikant et al. is an approximate result of this formula. The fitting results obtained by the two formulae coincide well from the measurement data of gallium nitride films grown on silicon substrate.

A novel, hierarchically porous diatomite/silicalite-1 composite with a high benzene removal efficiency was prepared via a facile coating process. Silicalite-1 nanoparticles (Sil-1nano) were synthesized in situ on the surface of the pre-modified diatomite support by using a mild, low-temperature reflux reaction method. The obtained composite possessed a hierarchically porous structure, involving micropores and stacking mesopores from the silicalite-1 nanoparticles, and it retained the macropores from the diatomite support. The specific surface area and micropore volume of the composite were 348.7 m2/g and 0.127 cm3/g, respectively, with a zeolite loading amount of up to 60.2%. The diatomite/silicalite-1 composite exhibited considerably higher static and dynamic benzene adsorption capacities (94.9 mg/g (Sil-1nano) and 246.0 mg/g (Sil-1nano) respectively) per unit mass of zeolite than did the synthesized Sil-1nano and commercial ZSM-5. Moreover, the introduced macroporosity of the diatomite reduced the mass transfer resistance of the nanoparticles because of their improved dispersity, and it provided more possible entryways for benzene molecules, leading to better penetration of benzene than for Sil-1nano or commercial ZSM-5. The composite showed steady reversibility after 4 adsorption cycles, further demonstrating the promise of such a novel synthesized adsorbent for the removal of volatile organic compounds in industrial applications.

Experimental investigations were conducted on a diesel engine to evaluate the effects of hydrogen addition on engine combustion, unregulated gaseous emissions and particulate emissions based on the Japanese 13-mode testing cycle. A diesel–hydrogen co-operated combustion strategy is proposed in which hydrogen is naturally aspirated into the diesel engine to substitute 10, 20 and 30% of the total fuel energy at 10 selected modes and diesel is used as the sole fuel for the other 3 modes. Gradual increase of peak in-cylinder pressure and heat release rate is observed at medium and high engine loads. Pre-ignition might occur at high engine load and speed. Cyclic variation of the indicated mean effective pressure and maximum pressure derivative increased with hydrogen addition. The brake specific emissions of acetaldehyde (CH3CHO), alkenes (C2H4, C3H6 and C4H6), arenes (C6H6, C7H8 and C8H10) and particulate mass can be evidently reduced. However, with H30 operation, the weighted total HC and formaldehyde (HCHO) increased by around 27% and 8%, respectively, while NOx increased by around 17%. The simultaneous decrease of particle size and number are believed to be associated with the inhibition effect of hydrogen on soot particle formation based on the HACA (H2 abstraction and C2H2 addition) mechanism.

Acidification of allophanic Andosols has significant effects on their physicochemical properties and productivity. Understanding of the acidification and related effects is limited by the structural changes of allophane – the major mineral composition of allophanic Andosols. In this work, we systematically investigated the structural stability of allophane and the mechanisms of structural changes under different acidic conditions (initial pH 4.0–2.0) by using chemical analysis, transmission electron microscopy, X-ray diffraction, Fourier-transform infrared spectroscopy, solid-state magic-angle-spinning nuclear magnetic resonance, and N2 physisorption analysis. The results indicated that the structure of allophane was readily altered in acidic conditions. Acid leaching in conditions with initial pH > 3.0 only dissolved some polymerized silicates from allophane, enlarging the defect pores. By contrast, the dissolution of the imogolite-like local structure was observed in strongly acidic conditions (initial pH

The influence of excessive H2 flow during barrier growth on optical and electrical properties of InGaN light-emitting diodes (LEDs) are investigated in this study. The room temperature photoluminescence of LEDs decays with excessive H2 treatment. Temperature-dependent photoluminescence (TDPL) reveals an increase of the density and a decrease of the activation energy of deep non-radiative recombination centers in the H2 treated LEDs. The external quantum efficiency (EQE) of the LEDs suffers from excessive H2 treatment. The leakage current on the reverse and forward sides of the LEDs are reduced significantly when treated with H2, which may be due to the suppressed Poole–Frenkel effect.

The interface, optical and electrical properties of InGaN light emitting diodes (LEDs) with different H2 flow treatment during the barrier growth are investigated in this study. With H2 treatment, the interface between the quantum well and barrier becomes rougher and the photoluminescence intensity decreases. The external quantum efficiency of the LEDs with 600 sccm (2.7%) H2 treatment has the best performance among the samples. Both the forward and reverse leakage currents of the samples are reduced significantly when treated with H2. Among the samples, a H2 flow with 600 sccm (2.7%) gives the best performance.

In this paper, a liquid regeneration method by vacuum membrane distillation (VMD) is proposed for the liquid desiccant air conditioning system (LDACs), and the experimental study on this method is carried out. VMD regeneration experiments were carried out with LiCl solution. The effects of temperature, concentration of feed solution, length, number of fiber membranes and vacuum pressure on the membrane flux, mass transfer coefficient, rejection rate and regeneration ability were studied. The results show that the error between experimental and calculation results is reduced from less than 15% to less than 5% by the optimized calculation model. The temperature of feed solution has a great influence on the regeneration performance of VMD, and the regeneration ability of VMD process increases approximately exponentially from about 0.1% to 0.8–1.2% with the increase of regeneration temperature. The VMD regeneration process of LiCl solution is the result of Poiseuille flow and Knudsen diffusion, and Poiseuille flow dominates. Under the same regeneration capacity, the regeneration temperature of 30 wt% LiCl solution is about 7 °C higher than that of 20 wt% LiCl solution, and this temperature difference also increases as the target regeneration amount increases. In order to improve the regeneration effect of high concentration solution, the regeneration temperature can be increased appropriately. The water flux of the membrane decreases with the increase of the length of the membrane. The membrane length of Type1 is 2.1 times longer than Type 2, but regeneration capacity of Type 1 is only 1–1.7 times higher than Type 2. Further, both the water flux and regeneration ability of the solution decrease first and then increase with the increasing number of membranes. Therefore, the reasonable selection of number of fiber membranes can significantly save materials and also improve the regeneration ability.

In this work, halloysite-CeOx (x = 1.5–2.0) nanocomposites were prepared using a redox-precipitation method, and the As(III) removal performance of the obtained materials was evaluated. These composites were formed by supporting CeO2 nanoparticles on the chemically modified halloysite substrate. The modification of halloysite using a facile NaOH treatment dramatically increased the inner-surface and inner hydroxyl groups. These increased groups significantly enhanced the dispersion of the coating of CeO2 nanoparticles due to electrostatic interactions. The specific surface area and pore volume of the optimized Hal0.01Ce composite was 91.1 m2/g and 0.16 cm3/g, respectively. This composite exhibited an excellent As(III) adsorption capacity (209.3 mg/g CeO2), which was much higher than the unmodified halloysite-CeOx composite (158.5 mg/g CeO2) and unsupported CeO2 nanoparticles (61.9 mg/g). The As(III) adsorption mechanisms on this composite involved the formation of surface complexes and oxidation of partial As(III) followed by As(V) adsorption. In addition, the Hal0.01Ce composite also possessed selective adsorption for As(III) in the presence of coexisting ions and maintained 91.4% of the As(III) removal efficiency after three regeneration cycles. These results demonstrate that this composite can be used as a potential candidate for As(III) removal from contaminated water.

Islet stellate cells (ISCs) activation is mainly associated with islet fibrosis, which contributes to the progression of type 2 diabetes. However, the molecular mechanism underlying this process is not fully understood.In order to investigate this process the current study examined ectopic fat accumulation in rats with high-fat diet (HFD) induced obesity. Levels of lipotoxicity-induced ISC activation and islet function were assessed via intraperitoneal glucose and insulin tolerance tests, and immunohistochemistry. The expression of lipid metabolism- and ISC activation-related markers was evaluated in cultured ISCs treated with palmitic acid (PA) using quantitative PCR and western blotting. We also overexpressed sterol regulatory element-binding protein (SREBP)-1c in ISCs by lentiviral transduction, and assessed the effects on insulin release in co-cultures with isolated rat islets.HFD increased body weight and ectopic fat accumulation in pancreatic islets. Lipotoxicity caused progressive glucose intolerance and insulin resistance, upregulated α-smooth muscle actin, and stimulated the secretion of extracellular matrix. Lipotoxicity reduced the expression of lipid metabolism-related molecules in ISCs treated with PA, especially SREBP-1c. Overexpression of SREBP-1c in ISCs improved islet viability and insulin secretion in co-cultures.These results indicate that lipotoxicity-induced ISC activation alters islet function via regulation of lipid metabolism, suggesting that therapeutic strategies targeting activated ISC may be an effective treatment for prevention of ISC activation-associated islet dysfunction.

A synergistic host-guest coupling is exploited to disorder nano-kaolinite unit layers to form Al2O3 nanoparticles, which act as activated adsorptive sites; meanwhile, the coupling enables La-based nanoparticles to anchor homogenously on the nano-kaolinite surfaces, fully utilizing their adsorption ability. The activated hybrid nanostructures exhibit an excellent phosphate adsorption capacity.

Monocytechemotactic protein-induced protein 1 (MCPIP1), a newly recognized mRNA endonuclease, can be induced by lipopolysaccharide (LPS) and ischemic attack, then exerts a negative feedback loop against neuroinflammatory injury, but the specific underlying signaling pathway of the induction is unclear. Toll-like receptors (TLRs) and receptor for advanced glycation end products (RAGE) signaling pathways are involved in LPS/ischemia-evoked inflammation. This study aims to explore which receptor signaling is mainly involved in the induction of MCPIP1 by LPS and ischemic attack. BV2 cells and mice were subjected to LPS stimulation or transient middle cerebral artery occlusion (MCAO) to examine the modulation of MCPIP1. Specific inhibitors for TLR4, TLR2 or RAGE were preadministered to explore the mechanisms of MCPIP1 expression. Results showed that MCPIP1 was significantly increased by LPS and ischemic stress both in vitro and in vivo in time and dose dependent manners. Inhibition of TLR4, rather than TLR2 or RAGE, downregulated the LPS/ischemia-induced expression of MCPIP1 and reduced the levels of TLR4, MyD88, phosphorylated-MAPK (p-P38), phosphorylated-IκBα (p-IκBα), as well as the translocation of NF-κB (p65). In conclusion, we firstly demonstrate that TLR4 signaling pathway, not TLR2 or RAGE, predominantly mediates the LPS/ischemia-induced expression of MCPIP1 in microglia.

Streptococcus suis is an important swine pathogen that can also cause severe diseases in humans. Herein, we describe the genome sequence of Streptococcus suis serotype 2 virulent strain SS2-1, which was isolated from a diseased dead pig amid the 1998 Streptococcus suis outbreak in Jiangsu Province in China.

This article presents a novel method to apply on reducing the period limitation in laser interference lithography (LIL) by preparing a kind of nanowire arrays with the period $${\uplambda }/(4\hbox {n}\times \hbox {sin}{\uptheta }$$ ) instead of $${\uplambda }/(2\hbox {n}\times \hbox {sin}{\uptheta }$$ ). Nanowire arrays with periods of 150 and 125 nm on Si (100) substrate were fabricated successfully with a 325 nm He–Cd continuous wave laser as a light source, based on the combined process of dry etching and wet etching. It is the slight over-etching in the dry etching process and keeping the fluorine carbon organic polymer layer intact during whole process of wet etching that guaranteed the nanowire generated from the platform between two adjacent etched facets. The width of the nanowire as narrow as 50 nm was fabricated by this method, which is much more interesting for the research on the small size effect. This method is proved to circumvent the period formula limitation of the traditional LIL and makes the preparation of nanostructures with much smaller size more feasible.

Human visual system (HVS) can perceive the difference between two retinal images to create a mental image with depth perception, which is the result of two binocular interactions, i.e., binocular fusion and suppression. According to perceptual attributes of binocular interactions, in this paper, a full-reference stereoscopic image quality assessment (SIQA) method is proposed based on the mechanisms of binocular fusion and suppression. There are two kinds of information in stereoscopic images: monocular information which is visible in only one view, and binocular information which is visible in two views. HVS adopts two ways to deal with the binocular information, one is binocular fusion which deals with the information with similar content and small disparity, the other is binocular suppression which deals with the information with dissimilar content or large disparity. Therefore, the proposed method firstly divides a distorted stereoscopic image into occluded, pseudo-binocular fusion and pseudo-binocular suppression regions. Then three methods are respectively adopted to assess the quality of the three regions and the three quality indices combine into one to represent the overall quality of the distorted stereoscopic image. Finally, the predictive performance of the proposed method is evaluated and compared with existing methods in terms of consistency, cross-image and cross-distortion, and robustness. Experimental results show that the proposed SIQA method outperforms other methods and can predict human visual perception of stereoscopic image more accurately.

Experiments were conducted to investigate the combustion and emission characteristics of a diesel engine with addition of hydrogen or methane for dual-fuel operation, and mixtures of hydrogen–methane for tri-fuel operation. The in-cylinder pressure and heat release rate change slightly at low to medium loads but increase dramatically at high load owing to the high combustion temperature and high quantity of pilot diesel fuel which contribute to better combustion of the gaseous fuels. The performance of the engine with tri-fuel operation at 30% load improves with the increase of hydrogen fraction in methane and is always higher than that with dual-fuel operations. Compared with ULSD–CH 4 operation, hydrogen addition in methane contributes to a reduction of CO/CO 2 /HC emissions without penalty on NO x emission. Dual-fuel and tri-fuel operations suppress particle emission to the similar extent. All the gaseous fuels reduce the geometry mean diameter and total number concentration of diesel particulate. Tri-fuel operation with 30% hydrogen addition in methane is observed to be the best fuel in reducing particulate and NO x emissions at 70 and 90% loads.

A method is suggested to improve the characteristics of light emitting diodes (LEDs) by using p-GaN structure with heavily Mg-doping grown at low temperature in full N-2 environment. The LED exhibits a 36.4% enhancement in light output power (LOP) at 222Acm(-2) due to the higher hole concentration as compared to the normal p-GaN layer. Meanwhile, the experimental results prove that the optimized LED structure shows reduced efficiency droop behavior, smaller peak wavelength blueshift and narrower electroluminescence (EL) spectrum broadening.

Streptococcus suis serotype 2 (SS2) is an important zoonotic pathogen that causes severe disease symptoms in pigs and humans. In the present study, we found one isogenic mutant lacking inosine 5-monophosphate dehydrogenase (IMPDH) ΔZY05719 was attenuated in pigs compared with the wild-type SS2 strain ZY05719. Comparative proteome analysis of the secreted proteins expression profiles between ZY05719 and ΔZY05719 allowed us to identify Triosephosphate isomerase (TPI) and glyceraldehyde phosphate dehydrogenase (GAPDH), which were down expressed in the absence of the IMPDH. Both of them are glycolytic enzymes participating in the glycolytic pathway. Compared with ZY05719, ΔZY05719 lost the ability of utilize mannose, which might relate to down expression of TPI and GAPDH. In addition, GAPDH is a well-known factor that involved in adhesion to host cells, and we demonstrated ability of adhesion to HEp-2 and PK15 by ΔZY05719 was significantly weakened, in contrast to ZY05719. The adhesion to host cells is the crucial step to cause infection for pathogen, and the reduction adhesion of ΔZY05719, to some extent illustrates the attenuated virulence of ΔZY05719.

In this paper, calcination and subsequent acid treatment were performed on halloysite to investigate their effects on dynamic benzene adsorption performance. Calcination at 800 °C had little effect on halloysite's tubular morphology, but it caused dehydroxylation and phase separation of amorphous SiO2 and Al2O3. The occurrence of dehydroxylation resulted in removal of hydroxyl groups, which reduced halloysite's hydrophilicity, leading to an improvement in the halloysite's affinity for hydrophobic benzene molecules. The dynamic benzene adsorption capacity increased from 68.1 mg/g in the original halloysite to 103.6 mg/g in the calcined halloysite. The acid treatment after pre-calcination preserved the halloysite's tubular morphology and introduced massive micropores as a result of the rapid dissolution of Al2O3 layers. The emergence of these massive micropores substantially improved the specific surface area and dynamic benzene adsorption capacity of the acid-treated calcined halloysite, which reached 472.3 m2/g and 204.2 mg/g, respectively. In addition, the recycling efficiency of the acid-treated calcined halloysite for benzene adsorption reached 92.5%, thus displaying good regeneration performance. These results demonstrate that calcination and subsequent acid treatment play important roles in promoting the halloysite's benzene adsorption performance, which makes the resulting halloysite a promising adsorbent for the treatment of volatile organic compounds.

Personal heating clothing systems (PHCS) incorporated with electrical heating elements have shown its great potential to help occupants attain thermal comfort in cold built environments. Presently there is a lack of a comprehensive study to optimize the PHCS's performance. In this work, a newly developed complete 3D model was used to systematically examine the factors affecting the PHCS's heating performance in various cold unheated built environments. Effects of ambient temperature, clothing insulation, heating power, heating mode and metabolic rate on the PHCS's performance were investigated by performing a numerical parametric study. Validation data have demonstrated that the 3D model could precisely predict human thermophysiological responses while wearing PHCS in the built environment. At 15.0 °C indoor temperature and metabolic rate of 1.6 met, wearing a PHCS with thermal insulation of 1.0 clo and heating power of 20 W could help occupants attain thermal comfort. It was also found that compared with continuous heating, intermittent heating at a high heating frequency could contribute to saving energy without compromise of body temperature reduction. Furthermore, metabolic rate has a significant impact on thermophysiological responses and the mean heaters' temperature. Hence, the selection and operation of a PHCS should be based on the nature of occupant activities. Occupants are advised to adjust the heating power to a lower level when performing more demanding activities because the need for auxiliary heating is not as high as that in the case when occupants are resting or performing seated office activities.

GaN-based light emitting diodes (LEDs) with nano truncated cone SiO2 passivation layer via laser interference lithography and inductively coupled plasma dry etching technology were fabricated. The sidewall profile of the nano truncated cones was optimized by adjusting the etching process to obtain high fill factor. The light output power and electroluminescence intensity of the LEDs with textured SiO2 surface show better results than the conventional LEDs without SiO2 layer. At an injection current of 20 mA, the enhancement of the light output power is about 64 %. Moreover, the reverse leakage current, under a reverse bias of −5 V, is obviously reduced in contrast to the conventional LEDs. The method of texturing the passivation layers is proved to be an alternative method to improve both the optical and electrical performances of GaN-based LEDs.

The porcine boca-like virus (Pbo-likeV) was recently discovered in Swedish pigs with post-weaning multisystemic wasting syndrome (PMWS). In this study, a loop-mediated isothermal amplification (LAMP) assay was developed for rapid, specific and sensitive detection of Pbo-likeV. A set of four primers specific for six regions of Pbo-likeV VP1/2 genes was designed with the online software. The reaction temperature and time were optimized to 65 °C and 60 min, respectively. LAMP products were detected by agarose gel electrophoresis or by visual inspection of a color change due to addition of fluorescent dye. The developed method was highly specific for detection of Pbo-likeV, and no cross-reaction was observed with other swine viruses, such as porcine reproductive and respiratory syndrome virus (PRRSV), porcine circovirus type 2 (PCV2), porcine parvovirus (PPV) and classic swine fever virus (CSFV) found commonly in China. The lower detection limit of the LAMP assay was approximately 10 copies per reaction, and it was 100 times more sensitive than that of conventional PCR. Furthermore, the efficiency of LAMP for detection Pbo-likeV in clinical samples was comparable to PCR and sequencing. These results showed that the LAMP assay is a simple, rapid, sensitive and specific technique for detection of Pbo-likeV, and the procedure of LAMP does not rely on any special equipment. It has capacity for the detection of Pbo-likeV both in the laboratory and on farms.

In this paper, the authors use the integral identities of triangular linear elements to prove a uniform optimal-order error estimate for the triangular element solution of two-dimensional time-dependent advection-diffusion equations. Also the authors introduce an interpolation postprocessing operator to get the superconvergence estimate under the ? weighted energy norm. The estimates above depend only on the initial and right data but not on the scaling parameter ?.

AlxGa1−xN/GaN high-electron-mobility transistor (HEMT) structures with Al composition ranging from x = 0.13 to 0.36 are grown on sapphire substrates by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). The effects of Al content on crystal quality, surface morphology, optical and electrical characteristics of the AlGaN/GaN heterostructures have been analyzed. Although high Al-content (36%) heterostructure exhibits a distinguished photoluminescence peak related to recombination between the two-dimensional electron gas and photoexcited holes (2DEG-h), its crystal quality and rough surface morphology are poor. 2DEG mobility increases with the Al content up to 26% and then it apparently decreases for high Al-content (36%) AlGaN/GaN heterostructure. The increase of sheet carrier density with the increase of Al content has been observed. A high mobility at room temperature of 2105 cm2/V s with a sheet carrier density of ns = 1.10 × 1013 cm−2, for a 26% Al-content AlGaN/GaN heterostructure has been obtained, which is approaching state-of-the-art for HEMT grown on SiC. Sheet resistance as low as 274 Ω/□ has also been achieved.

Streptococcus suis type 2 is a swine pathogen responsible for diverse diseases. Although many virulent factors have been identified and studied, relatively little is known about the pathogenic mechanisms of type 2. The aim of the study was to identify and understand the characterization of Inosine 5-monophosphate dehydrogenase (IMPDH). A 957-bp gene, impdh, was identified in the virulent S. suis serotype 2 (SS2), and analysis of the predicted IMPDH sequence revealed IMP dehydrogenase/GMP reductase domain. The gene encoding for the IMPDH of S. suis was cloned and sequenced. The DNA sequence contained an open reading frame encoding for a 318 amino acid polypeptide exhibiting 23% sequence identity with the IMPDH from Streptococcus pyogenes (YP281355) and Streptococcus pneumoniae (ZP00404150). Using the pET32 expression plasmid, the impdh gene was inducibly overexpressed in Escherichia coli to produce IMPDH with a hexahistidyl N-terminus to permit its purification. The (His)6 IMPDH protein was found to possess functional IMPDH enzymatic activity after the purification. The impdh-knockout SS2 mutant (△IMPDH) constructed in this study was slower in growth and one pH unit higher than SS2-H after 6 h of culturing, and found to be attenuated in mouse models of infection for 2.5 times and not be capable of causing death in porcine models of infection in contrast with the parent SS2-H.

The 256×1 linear array of multiple quantum wells infrared photodetector (QWIP) is designed and fabricated for the peak response wavelength at λ P = 14.6 μm. The response spectral width is bigger than 2.2 μm. The two-dimensional (2D) diffractive coupling grating has been formed on the top QWIP photosensitive pixel for coupling the infrared radiation to the infrared detective layers. The performance of the device at V B = 3 V and T = 45 K has the responsibility 4.28×10−2 (A/W), the blackbody detectivity D b* = 5.14×109 (cm·Hz1/2/W), and the peak detectivity D λ * = 4.24× 1010 (cm·Hz1/2/W). The sensor pixels are connected with CMOS read out circuit (ROC) hybridization by indium bumps. When integral time is 100 μs, the linear array has the effective pixel of QWIP FPA N ef of 99.2%, the average responsibility $$ \overline R $$ (V/W) of 3.48×106 (V/W), the average peak detectivity D λ * of 8.29×109 (cm·Hz1/2/W), and the non-uniformity UR of 5.83%. This device is ready for the thermal image application.

Low-temperature step-graded high indium content InAlAs (In% = 0.75) metamorphic buffer layers with reverse step layer grown on GaAs substrate by molecular beam epitaxy are investigated in this paper. The composition and the strain relaxation of the top InAlAs layer are determined by high-resolution triple-axis X-ray diffraction measurements, which show that the top InAlAs layer is nearly fully relaxed and the growth parameters for these samples have little influence on the strain relaxation ratio. Surface morphology is observed by reflection high-energy electron diffraction pattern and atomic force microscopy. The surface morphology is found to depend strongly on both the growth temperature and the As flux. Compared with other samples, the sample growth under the optimized conditions has the smallest value of root mean square surface roughness. Furthermore, the omega - 2 theta and omega scans of the triple-axis X-ray diffraction and transmission electron microscopy result also show the sample grown under the optimized conditions has good crystalline quality. (C) 2008 Elsevier B.V. All rights reserved.

Serials InAsxSb1-x samples grown on GaAs (0 0 1) substrates by solid source molecular beam epitaxy (MBE) have been investigated. The high-resolution X-ray diffraction (HRXRD) and atomic force microscope (AFM) results reveal that the quality and the surface morphology of InAsxSb1-x strongly depend on the III/V ratio, growth temperature and the thickness of nucleation layer. When growth temperature is 400 degrees C, In:As:Sb is about 1:0.4:2, and the thickness of the nucleation layer is 30 nm, the sample has the smallest FWHM (797 aresec), much better than the recent results [S. Nakamura, P. Jayavel, T. Kyama, Y. Hayakawa, J. Crystal Growth 300 (2007) 497; F. Gao, N. Chen, L. Liu, X.W. Zhang, J. Wu, Z. Yin, J. Crystal Growth 304 (2007) 472]. These results demonstrate that much better samples can be obtained by MBE. AFM surface particle analysis results show that surface morphology strongly associates with the surface particle size. Small particle size makes surface smooth and large particle size makes surface rough. Through optimizing the growth conditions, our samples have better crystal quality and smoother surface morphology. The sample which has the best crystal quality shows that the carrier mobility and density is 1.3 x 10(4) cm(2)/V s and 1.3 x 10(17) cm(3) at room temperature. (C) 2007 Elsevier B.V. All rights reserved.

In this paper, we shall use local estimates to give the superconvergence of high-order Galerkin finite element method for the elliptic equation of second order with constant coefficients by using the symmetric technique and integral identity. We get improved superconvergence on the inner locally symmetric mesh with respect to a point x0 for rectangular and triangular meshes.

The effects of GaN cap layer thickness and doping type on photoluminescence (PL) are investigated for InGaN/GaN quantum wells (QWs), which are deposited on a C-plane sapphire substrate by metal organic chemical vapor deposition (MOCVD). As for the results, the QWs capped with an unintentional doped (un-doped) GaN layer show a linear PL blue shift behavior with decreased cap layer thickness, while for the QWs capped with a heavy n- or p-doped GaN layer none of the similar behaviors are observed until the cap layer is less than 25 nm. These phenomena are well explained by introducing the effects of upward surface band bending. Surface polarization discontinuity and surface states are considered as the origins of the surface band bending. Furthermore, the actual surface band bending value of the un-doped GaN is also extracted as Eb = 1.54 ±0.08 eV from the linear PL blue shift behavior.

Photoluminescence (PL) is a nondestructive and powerful method to investigate carrier recombination and transport characteristics in semiconductor materials. In this study, the temperature dependences of photoluminescence of GaAs-AlxGa1-xAs multi-quantum wells samples with and without p-n junction were measured under both resonant and non-resonant excitation modes. An obvious increase of photoluminescence(PL) intensity as the rising of temperature in low temperature range (T xGa1-xAs quantum wells sample with p-n junction under non-resonant excitation. The origin of the anomalous increase of integrated PL intensity proved to be associated with the enhancement of carrier drifting because of the increase of carrier mobility in the temperature range from 15 K to 100 K. For non-resonant excitation, carriers supplied from the barriers will influence the temperature dependence of integrated PL intensity of quantum wells, which makes the traditional methods to acquire photoluminescence characters from the temperature dependence of integrated PL intensity unavailable. For resonant excitation, carriers are generated only in the wells and the temperature dependence of integrated PL intensity is very suitable to analysis the photoluminescence characters of quantum wells.

Light-emitting diodes (LEDs) in the wavelength region of 535–570 nm are still inefficient, which is known as the “green gap” problem. Light in this range causes maximum luminous sensation in the human eye and is therefore advantageous for many potential uses. Here, we demonstrate a high-brightness InGaN LED with a normal voltage in the “green gap” range based on hybrid multi-quantum wells (MQWs). A yellow-green LED device is successfully fabricated and has a dominant wavelength, light output power, luminous efficiency and forward voltage of 560 nm, 2.14 mW, 19.58 lm/W and 3.39 V, respectively. To investigate the light emitting mechanism, a comparative analysis of the hybrid MQW LED and a conventional LED is conducted. The results show a 2.4-fold enhancement of the 540-nm light output power at a 20-mA injection current by the new structure due to the stronger localization effect and such enhancement becomes larger at longer wavelengths. Our experimental data suggest that the hybrid MQW structure can effectively push the efficient InGaN LED emission toward longer wavelengths, connecting to the lower limit of the AlGaInP LEDs’ spectral range, thus enabling completion of the LED product line covering the entire visible spectrum with sufficient luminous efficacy.

A promising technique of lateral epitaxial overgrowth, namely CantiBridge epitaxy, is developed and demonstrated in order to reduce the threading dislocation density in GaN films. Using metalorganic chemical vapor deposition, the GaN films are grown on patterned sapphire fabricated by wet chemical etching, instead of traditional dry etching. The image of atomic force microscopy shows that the threading dislocations in CantiBridge-epitaxy GaN are reduced sharply, which makes a promising to realize the high-performance GaN-based optoelectronic devices.

Based on the electron interference resulting from the electrons reflected at the interfaces of superlattices, the transmission coefficient of electrons passing over barriers of superlattices is discussed. For electrons occupying states above barriers, if these electrons have transmission coefficient of T≥0.5 passing over the barriers of superlattice, the states above the barriers are defined as the conduction states, and if T

From the view of electron waving, taking account of the electron wave reflections at the interface between the well and the potential barrier layer we discuss the electronic states above the barriers in a GaAs/AlGaAs superlattice. We present a new method on calculating the breadth of the subband and the calculated breadth of GaAs/AlGaAs superlattice is in good agreement with experimental results.

The wavelength of the responsive peak for GaAs/Al0.3Ga0.7As multi-quantum well (MQW) infrared detectors was measured to be λ = 6.29 μ m at 77 K. Based on the theory of electron interference, the results calculated for the MQW structure indicate that there may be a series of separated conduction states above the barriers, on which the electrons can propagate along the direction perpendicular to well/barrier interfaces. For the quantum well parameters given in this article, the wavelength of light absorbed is calculated to be 6.29 μm when optical excitations occur for which electrons transit from Fermi level in quantum wells to the first conduction state E 1 above the barriers. The theoretical value for the responsive peak wavelength is in very good agreement with the measurement result. This shows that the wavelength of the responsive peak resulted from electron interferences for the MQW infrared detectors.

The new developed maskless lateral-epitaxial-overgrowth technique, in which the striped substrates are patterned by wet chemical etching, is systematically investigated using scanning electron microscopy, X-ray diffraction, and atomic force microscopy (AFM). Wing tilt is measured for the GaN films on patterned substrates with a range of "fill factor" (ratio of groove width to stripe period) and for the GaN in different growth time. It is found that changes in these parameters have a significant effect on the extent and distribution of wing tilt in the laterally overgrown regions relative to the GaN directly on the sapphire substrate. Increasing the thickness of GaN films is benefit to reduce wing tilt. The tilt is avoided in the GaN films with 4.5 mu m thickness and fill factor for 0.46. The full-width at half-maximum of X-ray rocking curves of the asymmetric diffraction peaks and the image of AFM both show that the threading dislocations in the developed lateral epitaxial overgrowth of GaN films are reduced sharply. The GaN template could be used as an excellent substrate to fabricate high-performance optoelectronic devices. (c) 2006 Elsevier B.V. All rights reserved.

Lattice-matched InGaP epilayers on GaAs (001) and InGaP/GaAs heterojunction bipolar transistors (HBTs) were successfully grown by solid-source molecular beam epitaxy (SSMBE) with a GaP decomposition source. A 3 μm thick InGaP epilayer shows that low temperature photoluminescence (PL) peak energy is as large as 1.998 eV, full width at half maximum (FWHM) is 5.26 meV, which is the smallest ever reported, and X-ray diffraction (XRD) rocking curve linewidth is as narrow as that of GaAs substrate. The electron mobilities at room temperature of nominally undoped InGaP layers obtained by Hall measurements are comparable to similar InGaP epilayer grown by solid-source molecular beam epitaxy (SSMBE) with other sources or other growth techniques. The large area InGaP/GaAs HBTs show very good Dc characteristics.

When the strength of the electric field applied along the growth axis of a multi-quantum well is F approximate to 3 x 10(3) V cm(-1), we observe a series of peaks in the photocurrent (PC) spectrum. These peaks can be explained by the split of conduction states (minibands), which is due to interference of electrons above the barriers in the conduction band. More specifically, the peaks correspond to electron transitions from the ground state in a well to the conduction states above wells, including vertical transitions to the states above the well and the oblique transitions to the states above its neighbouring wells. The positions of the PC peaks in our experiments agree well with theoretical calculations.

Electrons are reflected at the interface between the well and the potential barrier layer when they transport along the direction perpendicular to the interface in a multi-quantum well (MQW) structure. From the view of electron waving, it can be predicted that the electron wave reflections at the interface between the well and the potential barrier layer make the continuous electron states above potential barriers separated into a series of conduction states and local states. The electrons occupying the conduction states can transport along the direction perpendicular to the interface in a MQW structure, while those who occupy the local states cannot because they are confined in the quantum well layer. The calculated energy levels of the conduction states above barriers agree well with the measured ones in our experiment.

We demonstrate the fabrication of high-quality GaAs/AlGaAs multiple quantum wells (MQWs) at very low temperature by solid-state source molecular beam epitaxy. The key to our method is to maintain a critical arsenic pressure or As/Ga beam equivalent pressure ratio to ensure a sharp heterointerface and a low defect density. A sharp heavy-hole excitonic photoluminescence (PL) signal was observed from the MQWs with a well width of 7.5 nm and a barrier width of 4 nm grown at 360°C. The PL linewidth of the QW heavy-hole exciton is 3 meV measured at 77 K. This emission linewidth is far narrower than that in a sample with the same structure grown at the standard growth temperature. The resistivity of the as-grown sample is about 5×106 Ωcm and increases to 5×107 Ωcm after postgrowth annealing at 700°C. The low growth temperature and high optical quality as well as the high resistivity make this kind of material suitable for use in ultrafast optical and monolithic integrated optoelectronic devices.

The indium segregation in InGaN well layer is confirmed by a nondestructive combined method of experiment and numerical simulation, which is beyond the traditional method. The pre-deposited indium atoms before InGaN well layer growth are first carried out to prevent indium atoms exchange between the subsurface layer and the surface layer, which results from the indium segregation. The uniform spatial distribution of indium content is achieved in each InGaN well layer, as long as indium pre-deposition is sufficient. According to the consistency of the experiment and numerical simulation, the indium content increases from 16% along the growth direction and saturates at 19% in the upper interface, which cannot be determined precisely by the traditional method.

Electroacupuncture has traditionally been used to treat pain, but its effect on pain following brachial plexus injury is still unknown. In this study, rat models of an avulsion injury to the left brachial plexus root (associated with upper-limb chronic neuropathic pain) were given electroacupuncture stimulation at bilateral Quchi (LI11), Hegu (LI04), Zusanli (ST36) and Yanglingquan (GB34). After electroacupuncture therapy, chronic neuropathic pain in the rats' upper limbs was significantly attenuated. Immunofluorescence staining showed that the expression of β-endorphins in the arcuate nucleus was significantly increased after therapy. Thus, experimental findings indicate that electroacupuncture can attenuate neuropathic pain after brachial plexus injury through upregulating β-endorphin expression.

The pursuit of high internal quantum efficiency (IQE) for green emission spectral regime is referred as “green gap” challenge. Now researchers place their hope on the InGaN-based materials to develop high-brightness green light-emitting diodes. However, IQE drops fast when emission wavelength of InGaN LED increases by changing growth temperature or well thickness. In this paper, a new wavelength-adjusting method is proposed and the optical properties of LED are investigated. By additional process of indium pre-deposition before InGaN well layer growth, the indium distribution along growth direction becomes more uniform, which leads to the increase of average indium content in InGaN well layer and results in a redshift of peak-wavelength. We also find that the IQE of LED with indium pre-deposition increases with the wavelength redshift. Such dependence is opposite to the IQE-wavelength behavior in conventional InGaN LEDs. The relations among the IQE, wavelength and the indium pre-deposition process are discussed.

Streptococcus suis serotype 2 (SS2) is an important swine and human pathogen responsible for septicemia and meningitis. The bacterial homologues of eukaryotic-type serine/threonine kinases (ESTKs) have been reported to play critical roles in various cellular processes. To investigate the role of STK in SS2, an isogenic stk mutant strain (Δstk) and a complemented strain (CΔstk) were constructed. The Δstk showed a significant decrease in adherence to HEp-2 cells, compared with the wild-type strain, and a reduced survival ratio in whole blood. In addition, the Δstk exhibited a notable reduced tolerance of environmental stresses including high temperature, acidic pH, oxidative stress, and high osmolarity. More importantly, the Δstk was attenuated in both the CD1 mouse and piglet models of infection. The results of quantitative reverse transcription-PCR (qRT-PCR) analysis indicated that the expressions of a few genes involving in adherence, stress response and virulence were clearly decreased in the Δstk mutant strain. Our data suggest that SsSTK is required for virulence and stress response in SS2.