Genetic evidence for an East Asian origin of domestic dogs

The origin of the domestic dog from wolves has been established, but the number of founding events, as well as where and when these occurred, is not known. To address these questions, we examined the mitochondrial DNA (mtDNA) sequence variation among 654

中国株丙型肝炎病毒实验感染3种猕猴的初步结果

选用无各型肝炎病毒感染、体质良好的6只食蟹猴、3只恒河猴和3只熊猴,按人感染HCV的主要途径——输血,经静脉输注含HCV的中国献血员血浆,观察临床一般指标,血清ALT,抗HCV各种抗体和HCV-RNA,肝组织普通病理,超微病理。从肝组织中找病毒颗粒及免疫组化查HCV NS3抗原,观察14周,结果9例猕猴出现不同程度的肝炎症状,12例血清ALT升高,2例出现黄疸;5例抗HCVC22 IgG抗体阳性,4例抗HCV E2-24 IgG抗体阳性,10例抗HCV C33c IgG抗体阳性,2例抗HCVNS4-40 IgG抗体阳性,11例抗HCV NS5-A IgG抗体阳性,无1例抗HCVNS5-B IgG抗体阳性;9例HCV-RNA阳性。6例肝活检或肝小部切除作肝组织普通光镜镜检,5例肝细胞气球样变,点状坏死及少许纤维组织增生。另一例相应损害较重,呈碎片坏死,界板破坏,纤维组织增生明显,汇管区炎性细胞浸润,超微病理除普通炎症所具有的特征外,以滑面内质网大量增生扩张为其主要特征,3例从内质网里看到约30nm的类病毒颗粒。免疫组化显示3只动物肝组织内HCVNS3抗原阳性,以膜型为主少量周边型及散在胞浆内分布,因此我们认为已...

Growth window and possible mechanism of millimeter-thick single-walled carbon nanotube forests.

Our group recently reproduced the water-assisted growth method, so-called "SuperGrowth", of millimeter-thick single-walled carbon nanotube (SWNT) forests by using C2H4/H2/H2O/Ar reactant gas and Fe/Al2O3, catalyst. In this current work, a parametric study was carried out on both reaction and catalyst conditions. Results revealed that a thin Fe catalyst layer (about 0.5 nm) yielded rapid growth of SWNTs only when supported on Al2O3, and that Al2O3 support enhanced the activity of Fe, Co, and Ni catalysts. The growth window for the rapid SWNT growth was narrow, however. Optimum amount of added H2O increased the SWNT growth rate but further addition of H2O degraded both the SWNT growth rate and quality. Addition of H2 was also essential for rapid SWNT growth, but again, further addition decreased both the SWNT growth rate and quality. Because Al2O3 catalyzes hydrocarbon reforming, Al2O3 support possibly enhances the SWNT growth rate by supplying the carbon source to the catalyst nanoparticles. The origin of the narrow window for rapid SWNT growth is also discussed.

Hydrothermally-grown ZnO nanowire tips for scanning tunnelling microscopy.

The probe tip is pivotal in determining the resolution and nature of features observed in the Scanning Tunnelling Microscope (STM). We have augmented a conventional Pt/Ir metallic tip with a hydrothermally grown ZnO nanowire (NW). Atomic resolution imaging of graphite is attained. Current-voltage (IV) characteristics demonstrate an asymmetry stemming from the unintentional n-type doping of the ZnO NW, whereas the expected Schottky barrier at the ZnO-Pt/Ir interface is shown to have negligible effect. Moreover the photoconductivity of the system is investigated, paving the way towards a photodetector capable of atomic resolution.

Pulsewidth switchable, wavelength tuneable ultrafast fiber laser mode-locked by carbon nanotubes

Employing a nanotube-based saturable absorber, we demonstrate a continuously tunable (1533-1563nm) ultrafast fiber laser, with output pulsewidth switchable between picosecond (1.2 ps) and femtosecond (610 fs) regimes. © 2012 IEEE.

A review on slip models for gas microflows

Accurate modeling of gas microflow is crucial for the microfluidic devices in MEMS. Gas microflows through these devices are often in the slip and transition flow regimes, characterized by the Knudsen number of the order of 10-2∼100. An increasing number of researchers now dedicate great attention to the developments in the modeling of non-equilibrium boundary conditions in the gas microflows, concentrating on the slip model. In this review, we present various slip models obtained from different theoretical, computational and experimental studies for gas microflows. Correct descriptions of the Knudsen layer effect are of critical importance in modeling and designing of gas microflow systems and in predicting their performances. Theoretical descriptions of the gas-surface interaction and gas-surface molecular interaction models are introduced to describe the boundary conditions. Various methods and techniques for determination of the slip coefficients are reviewed. The review presents the considerable success in the implementation of various slip boundary conditions to extend the Navier-Stokes (N-S) equations into the slip and transition flow regimes. Comparisons of different values and formulations of the first- and second-order slip coefficients and models reveal the discrepancies arising from different definitions in the first-order slip coefficient and various approaches to determine the second-order slip coefficient. In addition, no consensus has been reached on the correct and generalized form of higher-order slip expression. The influences of specific effects, such as effective mean free path of the gas molecules and viscosity, surface roughness, gas composition and tangential momentum accommodation coefficient, on the hybrid slip models for gas microflows are analyzed and discussed. It shows that although the various hybrid slip models are proposed from different viewpoints, they can contribute to N-S equations for capturing the high Knudsen number effects in the slip and transition flow regimes. Future studies are also discussed for improving the understanding of gas microflows and enabling us to exactly predict and actively control gas slip. © Springer-Verlag 2012.

Enhancement of microfluidic efficiency with nanocrystalline diamond interlayer in the ZnO-based surface acoustic wave device

Ultra-smooth nanocrystalline diamond (UNCD) films with high-acoustic wave velocity were introduced into ZnO-based surface acoustic wave (SAW) devices to enhance their microfluidic efficiency by reducing the acoustic energy dissipation into the silicon substrate and improving the acoustic properties of the SAW devices. Microfluidic efficiency of the ZnO-based SAW devices with and without UNCD inter layers was investigated and compared. Results showed that the pumping velocities increase with the input power and those of the ZnO/UNCD/Si devices are much larger than those of the ZnO/Si devices at the same power. The jetting efficiency of the droplet was improved by introducing the UNCD interlayer into the ZnO/Si SAW device. Improvement in the microfluidic efficiency is mainly attributed to the diamond layer, which restrains the acoustic wave to propagate in the top layer rather than dissipating into the substrate. © 2013 Springer-Verlag Berlin Heidelberg.

Assessment effects of cage culture on nitrogen and phosphorus dynamics in relation to fallowing in a shallow lake in China

Nitrogen and phosphorus dynamics in relation to fallowing in a fish cage farm was investigated in a shallow lake in China. Four sampling sites were set: beneath the cages, at the cage sides, and 50 and 100 m east of the cage farm. Total nitrogen (TN) and total phosphorus (TP) in lake water and sediment were analyzed during a 2-year rearing cycle. The cage culture had a fish yield of 16.3-39.2 tonnes in the study period. Based on the mass balance equation, 1533-3084 kg TN and 339-697 kg TP were contributed to the lake environment. Nitrogen and phosphorous concentrations showed greater increase in the first culture period than in the second rearing cycle. No obvious changes were found at the sampling sites 50 and 100 m east of the cages during the study periods. Main impacts were found close to the cages (beneath the cages and at the cage side); the sampling points at the cage side showed relatively high TN and TP sedimentation. After 3 months of fallowing, water TN and TP decreased significantly but the sediment TN and TP contents remained high. Therefore, recovery seems to happen during fallowing but attention should be paid to whether the culture continues to operate in the future.

Photosynthetic physiology and growth as a function of colony size in the cyanobacterium Nostoc sphaeroides

Algal size can affect the rate of metabolism and of growth. Different sized colonies of Nostoc sphaeroides were used with the aim of determining the effects of colony size on photosynthetic physiology and growth. Small colonies showed higher maximum photosynthetic rates per unit chlorophyll, higher light saturation point, and higher photosynthetic efficiency (a) than large colonies. Furthermore, small colonies had a higher affinity for DIC and higher DIC-saturated photosynthetic rates. In addition, small colonies showed higher photosynthetic rates from 5-45degreesC than large colonies. There was a greater decrease in Fv/Fm after exposure to high irradiance and less recovery in darkness for large colonies than for small colonies. Relative growth rate decreased with increasing colony size. Small colonies had less chl a and mass per unit surface area. The results indicate that small colonies can harvest light and acquire DIC more efficiently and have higher maximum photosynthetic rates and growth rates than large colonies.