暹罗鱼腥藻空间飞行突变株的光合特性分析

对经空间飞行搭载而获得的通罗鱼腥藻突变株的分析发现，与对照相比，它在生长率和光合效率方面明显较高．进一步分析其光合色素的组成，叶绿素荧光及PSII／PSI比值，发现突变株的PC／Chl比值明显低于对照藻株，而叶绿素荧光高于对照，PSII／PSI比值是对照藻株的1.7倍，在其它光合色素的比例上也有差异．分析这些结果表明，突变株与对照株在光合特征上有差异可能是突变株在色素系统的改变引起光能捕捉和光能利用上更为高效的原因．

淤泥湖退化水生植被恢复及其在湖泊资源天然生态库中作用的研究

对淤泥湖水生植被的天然恢复过程、群落组成、结构、功能与动态等进行了定位研究（１９９２～１９９５）．该湖水生植物共有２０科２９属４１种．４种生活型的植物种类在该湖均有分布，以沉水草本（１５种）和挺水草本（１３种）为多．８个分布区类型中世界广布成分１６种和东亚成分１０种．群落结构包括层次结构和层片结构．该彻共有８个群落类型；群落现存量３２０８．８ｇ·ｍ－２，全湖植被资源贮量为１６３６５．２ｔ．

吸鱼粘体虫在异育银鲫心脏中的孢子发生

吸鱼粘体虫主要寄生在异育银鲫的心肌纤维间。随着营养体的长大,营养体内的两型生殖细胞相聚,小生殖细胞包围大生殖细胞,形成泛孢子母细胞。大生殖细胞进行连续的核分裂,成为产孢体。核分裂达12核时,产孢体内分化为10个细胞:4个成极囊细胞,4个成壳片细胞和2个双核的孢子质细胞。这些细胞均分为两组,从而形成双生孢子型的泛孢子母细胞。

白暨豚上呼吸道的解剖和组织学的研究

白鱀豚上呼吸道具有前庭囊、鼻额囊及前颌囊三对气囊,没有副囊和连接囊。三对囊均右大于左,其中又以前庭囊最为显著。喉由甲状软骨、环状软骨、会厌软骨及一对杓状软骨组成,从喉腔壁的组织学观察发现有室皱襞(假声带)的存在。

Making the deployment of pico-PV more sustainable along the value chain

Pico-PV is an excellent technology for bringing electric light to rural areas in the developing world and replacing kerosene lanterns and candles. However, as pico-PV is a comparatively new technology, relatively little is known about appropriate methods for sustainable product development and deployment. For this reason current dissemination methods are often ineffective and unsustainable. This research aims to help project developers deploy pico-PV technologies successfully and in a sustainable manner. To achieve this, a conceptual framework of key sustainability criteria along the value chain was developed and tested. The analysis revealed that the most important criteria for the sustainable deployment of pico-PV systems are: (a) easy and safe operation of the product; (b) that a system for product return is established; (c) the retailer understands the target market and (d) the end-user is aware of the product's existence and its benefits. This research reveals that criteria (b) and (c) are of greatest concern. In light of these findings, the authors propose to focus on the following five factors; namely: (a) raising awareness for certification and creating market reassurance; (b) introducing support mechanisms to facilitate local repair; (c) using existing supply channels and establishing in-country (dis)assembly; (d) introducing financial support mechanisms at product supply stages and; (e) undertaking marketing campaigns. © 2013 Elsevier Ltd. All rights reserved.

800V lateral IGBT in bulk Si for low power compact SMPS applications

An 800V rated lateral IGBT for high frequency, low-cost off-line applications has been developed. The LIGBT features a new method of adjusting the bipolar gain, based on a floating N+ stripe in front of the P+ anode/drain region. The floating N+ layer enhances the carrier recombination at the anode/drain side of the drift region resulting in a very significant decrease in the turn-off speed and substantially lower overall losses. Switching speeds as low as 140ns at 25oC and 300ns at 125oC have been achieved with corresponding equivalent Rdson at 125oC below 90mω.cm2. A fully operational AC-DC converter using a controller with an integrated LIGBT+depletion mode MOSFET chip has been designed and qualified in plastic SOP8 packages and used in 5W, 65kHz SMPS applications. The device is fabricated in 0.6μm bulk silicon CMOS technology without any additional masking steps. © 2013 IEEE.

Construction and characterization of a Lipotes vexillifer genomic DNA BAC library

We constructed a genomic DNA library for Lipotes vexillifer (L. vexillifer), the Baiji or Yangtze River dolphin, one of the most endangered mammals in the world. The library consists of 149,000 BAC clones, with an average insert size of 83 kb, representing approximately 3.4 haploid genome equivalents. PCR amplification of four known L. vexillifer genes yielded two to four positive clones each. To demonstrate the utility of this library, we isolated and sequenced the L. vexillifer alpha lactalbumin gene, which is a gene specific to mammals and one which has been widely used as molecular tool in phylogenetic analysis. We also end-sequenced 20 randomly selected clones, resulting in the identification of at least five new L. vexilliter genes, five SSR loci, and one SINE locus. These results suggest that this library is a valuable resource for candidate gene cloning, physical mapping, and genome sequencing of this important and threatened species.

Methylmercury, total mercury and total selenium in four common freshwater fish species from Ya-Er Lake, China

Snakehead fish (Ophiocephalus argus cantor), silver carp (Hypophthalmichthys molitrtix), crucian carp (Carassius carassius), and common carp (Cyprinus carpio) are four common freshwater fish species in China. In this study, the level of methylmercury (MeHg), total mercury (T-Hg), and total selenium (T-Se) in muscle samples of these four fish species from Ya-Er Lake, China, were analyzed using atomic fluorescence spectrometry coupled with high-performance liquid chromatography, and inductively coupled plasma mass spectrometry. The concentrations of MeHg in all the fish species were significantly correlated with those of T-Hg. Higher T-Hg and MeHg concentrations had accumulated in the snakehead fish, which is a strongly predatory fish, than in the other three species. The concentration ratios of MeHg and T-Hg in the muscles of these four fish species were almost equal. Conversely, there was negative correlation between the concentrations of T-Hg and T-Se, which implies that there is a competition between these two elements with respect to bioaccumulation. It is noteworthy that of all the muscle samples tested, the level of T-Hg exceeded the maximum allowable limit in fish [0.4 mg kg(-1) (w/w) recommended by the World Health Organization] in 38.46% of those of the silver carp, 18.18% of those of the crucian carp, and 100% of those of snakehead fish. These results show that the consumption of contaminated fish is a potential threat to human health and that necessary preventive measures to safeguard public health should be emphasized.

Running and walking with compliant legs

It has long been the dream to build robots which could walk and run with ease. To date, the stance phase of walking robots has been characterized by the use of either straight, rigid legs, as is the case of passive walkers, or by the use of articulated, kinematically-driven legs. In contrast, the design of most hopping or running robots is based on compliant legs which exhibit quite natural behavior during locomotion. © 2006 Springer.

Root zone microbial populations, urease activities, and purification efficiency for a constructed wetland

In order to investigate the effects of microorganisms and their urease activities in macrophytic root zones on pollutant removal, four small-scale plots (SSPs) of vertical/reverse-vertical flow wetlands were set up to determine: a) the relationship between the abundance of microorganisms in the root zones and water purification efficiency; and b) the relationship between urease activities in the root zones and pollutant removal in a constructed wetland system. Total numbers of the microbial population (bacteria, fungi, and actinomyces) along with urease activities in the macrophytic root zones were determined. In addition, the relationships between microbial populations and urease activities as well as the wastewater purification efficiencies of total phosphorus (TP), total Kjeldahl nitrogen (TKN), biochemical oxygen demand in 5 days (BOD5), and chemical oxygen demand (COD) were also analyzed. The results showed that there was a highly significant positive correlation (r = 0.9772, P < 0.01) between the number of bacteria in the root zones and BOD5 removal efficiency and a significant negative correlation (r = -0.9092, P < 0.05) between the number of fungi and the removal efficiency of TKN. Meanwhile, there was a significant positive correlation (r = 0.8830, P < 0.05) between urease activities in the root zones and the removal efficiency of TKN. Thus, during wastewater treatment in a constructed wetland system, microorganism and urease activities in the root zones were very important factors.

Structural, mechanical, thermodynamic, and electronic properties of thorium hydrides from first-principles

We perform first-principles calculations of the structural, electronic, mechanical, and thermodynamic properties of thorium hydrides (ThH2 and Th4H15) based on the density functional theory with generalized gradient approximation. The equilibrium geometries, the total and partial densities of states, charge density, elastic constants, elastic moduli, Poisson's ratio, and phonon dispersion curves for these materials are systematically investigated and analyzed in comparison with experiments and previous calculations. These results show that our calculated equilibrium structural parameters are well consistent with experiments. The Th-H bonds in all thorium hydrides exhibit weak covalent character, but the ionic properties for ThH2 and Th4H15 are different due to their different hydrogen concentration. It is found that while in ThH2 about 1.5 electrons transfer from each Th atom to H, in Th4H15 the charge transfer from each Th atom is around 2.1 electrons. Our calculated phonon spectrum for the stable body-centered tetragonal phase of ThH2 accords well with experiments. In addition we show that ThH2 in the fluorite phase is mechanically and dynamically unstable.

Spin precession and electron spin polarization wave in [001]-grown quantum wells

We theoretically study the spatial behaviors of spin precessions modulated by an effective magnetic field in a two-dimensional electron system with spin-orbit interaction. Through analysis of interaction between the spin and the effective magnetic field, we find some laws of spin precession in the system, by which we explain some previous phenomena of spin precession, and predict a controllable electron spin polarization wave in [001]-grown quantum wells. The shape of the wave, like water wave, mostly are ellipse-like or circle-like, and the wavelength is anisotropic in the quantum wells with two unequal coupling strengths of the Rashba and Dresselhaus interactions, and is isotropic in the quantum wells with only one spin orbit interaction.

Growth and characterization of InN on sapphire substrate by RF-MBE

Indium nitride (InN) films were grown on sapphire substrates by radio-frequency plasma-excited molecular beam epitaxy (RF-MBE). Atomic force microscopy (AFM), reflection high-energy electron diffraction (RHEED), double-crystal X-ray diffraction (DCXRD) and photoluminescence (PL) spectroscopy were used to characterize the InN films. The results show that the InN films have good crystallinity, with full-width at half-maximum (FWHM) of InN (0 0 0 2) DCXRD peak being 14 arcmin. At room temperature, a strong PL peak at 0.79eV was observed. At 1.9eV or so, no peak was observed. In addition, it is found that the InN films grown with low-temperature (LT) InN buffer layer are of better quality than those without LT-InN buffer layer. (c) 2004 Elsevier B.V. All rights reserved.

Pressure behavior of Te isoelectronic centers in S-rich ZnS1-xTex alloy

The photoluminescence from ZnS1-xTex alloy with 0 < x < 0.3 was investigated under hydrostatic pressure up to 7 GPa. Two peaks were observed in the alloys with x < 0.01, which are related to excitons bound to isolated Te isoelectronic impurities (Te-1 centers) and Te pairs (Te-2 centers), respectively. Only the Te-2 related emissions were observed in the alloys with 0.01 < x < 0.03. The emissions in the alloys with 0.03 < x < 0.3 are attributed to the excitons bound to the Te-n (n greater than or equal to 3) cluster centers. The pressure coefficient of the Te-1 related peak is 89(4) meV/GPa, about 40% larger than that of the band gap of ZnS. On the other hand, the pressure coefficient of the Te-2 related emissions is only 52(4) meV/GPa, about 15% smaller than that of the ZnS band gap. A simple Koster-Slater model has been used to explain the different pressure behavior of the Te-1 and Te-2 centers. The pressure coefficient of the Te-3 centers is 62(2) meV/GPa. Then the pressure coefficients of the Te-n centers decrease rapidly with further increasing Te composition.

Effect of buffer layer growth conditions on the secondary hexagonal phase content in cubic GaN films on GaAs(001) substrates

In this letter, we investigated the effect of the buffer layer growth conditions on the secondary hexagonal phase content in cubic GaN films on GaAs(0 0 1) substrate. The reflection high-energy electron diffraction (RHEED) pattern of the low-temperature GaN buffer layers shows that both the deposition temperature and time are important in obtaining a smooth surface. Four-circle X-ray double-crystal diffraction (XRDCD) reciprocal space mapping was used to study the hexagonal phase inclusions in the cubic GaN (c-GaN) films grown on the buffer layers. The calculation of the volume contents of the hexagonal phase shows that higher temperature and longer time deposition of the buffer layer is not preferable for growing pure c-GaN film. Under optimized condition, 47 meV FWHM of near band gap emission of the c-GaN film was achieved. (C) 2000 Elsevier Science B.V. All rights reserved.