Effects of age and dietary protein level on digestive enzyme activity and gene expression of Pelteobagrus fulvidraco larvae

The present research studied the effects of age and dietary protein level on pepsin, trypsin and amylase activity and their mRNA level in Petteobagrus fulvidraco larvae from 3 to 26 days after hatch (DAH). Three DAH larvae were fed three isoenergetic diets, containing 42.8% (CP 43), 47.3% (CP 47) and 52.8% (CP 53) crude protein. Live food (newly hatched Artemia, unenriched) was included as a control. The effects of age on enzyme activity and mRNA were as follows: pepsin and trypsin activity in all treatment groups showed a significant (P < 0.05) increase at the beginning and decrease later although the timing of decrease was not the same among treatment groups and between the digestive enzymes. Pepsin and trypsin mRNA level followed the pattern of their respective enzyme changes. Age significantly affected amylase activity (P < 0.05) while age had no effect on amylase mRNA during the experimental period. The four diets significantly (P < 0.05) affected activity and mRNA level of pepsin and trypsin. Diets did not affect amylase activity or mRNA level. These results suggest that the effects of age on pepsin and trypsin gene expressions are at the transcriptional level. Dietary protein level does affect pepsin and trypsin gene expression in the early life of P. fulvidraco. There were no transcriptional effects on amylase gene expression. (c) 2005 Elsevier B.V. All rights reserved.

Molecular identification and expression analysis of natural resistance associated macrophage protein (Nramp) cDNA from Japanese flounder (Paralichthys olivaceus)

Natural resistance associated macrophage protein (Nramp) controls partially innate resistance to intracellular parasites. Its function is to enhance the ability of macrophages to kill pathogens. However, little is known about the structure and function of Nramp in lower vertebrates such as teleosts. We have recently isolated a cDNA encoding Nramp from Japanese flounder (Paratichthys olivaceus). The full-length cDNA of the Nramp is 3066 bp in length, including 224 bp 5' terminal UTR, 1662 bp encoding region and 1180 bp 3' terminal UTR. The 1662-nt open reading frame was found to code for a protein with 554 amino acid residues. Comparison of amino acid sequence indicated that Japanese flounder Nramp consists of 12 transmembrane (TM) domains. A consensus transport motif (CTM) containing 20 residues was observed between transmembrane domains 8 and 9. The deduced amino acid sequence of Japanese flounder had 77.30%, 82.71%, 82.67%, 79.64%, 80.72%, 90.97%, 91.16%, 60.14%, 71.48%, 61.69%, 72.37% identity with that of rainbow trout Nramp alpha and beta, channel catfish Nramp, fathead minnow Nramp, common carp Nramp, striped sea bass Nramp, red sea bream Nramp, mouse Nramp 1 and 2, human Nramp 1 and 2, respectively. RT-PCR indicated that Nramp transcripts were highly abundant in spleen, head kidney, abundant in intestine, liver and gill, and less abundant in heart. The level of Nramp mRNA in embryos gradually increases during embryogenesis from 4 h (8 cell stage) to 80 h (hatched stage) after fertilization. (c) 2005 Elsevier Ltd. All rights reserved.

Annihilation of deep level defects in InP through high temperature annealing

Deep level transient spectroscopy (DLTS) and thermally stimulated current spectroscopy (TSC) have been used to investigate defects in semi-conducting and semi-insulating (SI) InP after high temperature annealing, respectively. The results indicate that the annealing in iron phosphide ambient has an obvious suppression effect of deep defects, when compared with the annealing in phosphorus ambient. A defect annihilation phenomenon has also been observed in Fe-doped SI-InP materials after annealing. Mechanism of defect formation and annihilation related to in-diffusion of iron and phosphorus is discussed. Nature of the thermally induced defects has been discussed based on the results. (c) 2007 Elsevier Ltd. All rights reserved.

Electronic structure of a hydrogenic acceptor impurity in semiconductor nano-structures

The electronic structure and binding energy of a hydrogenic acceptor impurity in 2, 1, and 0-dimensional semiconductor nano-structures (i.e. quantum well (QW), quantum well wire (QWW), and quantum dot (QD)) are studied in the framework of effective-mass envelope-function theory. The results show that (1) the energy levels monotonically decrease as the quantum confinement sizes increase; (2) the impurity energy levels decrease more slowly for QWWs and QDs as their sizes increase than for QWs; (3) the changes of the acceptor binding energies are very complex as the quantum confinement size increases; (4) the binding energies monotonically decrease as the acceptor moves away from the nano-structures' center; (5) as the symmetry decreases, the degeneracy is lifted, and the first binding energy level in the QD splits into two branches. Our calculated results are useful for the application of semiconductor nano-structures in electronic and photoelectric devices.

Scale study of direct synthesis of dimethyl ether from biomass synthesis gas

We investigated the synthesis of dimethyl ether (DME) from biomass synthesis gas using a kind of hybrid catalyst consisting of methanol and HZSM-5 zeolite in a fixed-bed reactor in a 100 ton/year pilot plant. The biomass synthesis gas was produced by oxygen-rich gasification of corn core in a two-stage fixed bed. The results showed that CO conversions reached 82.00% and 73.55%, the selectivities for DME were 73.95% and 69.73%, and the space-time yields were 124.28 kg m- 3 h- 1 and 203.80 kg m- 3 h- 1 when gas hourly space velocities were 650 h- 1 and 1200 h- 1, respectively. Deoxidation and tar removal from biomass synthesis gas was critical to the stable operation of the DME synthesis system. Using single-pass synthesis, the H2/CO ratio improved from 0.98-1.17 to 2.12-2.22. The yield of DME would be increased greatly if the exhaust was reused after removal of the CO2.

自然侵蚀量和容许土壤流失量与水土流失治理标准

在总结分析国内有关自然侵蚀量、容许土壤流失量研究成果的基础上,探讨自然侵蚀量与容许土壤流失量的关系,讨论制订水土流失治理标准的思路。认为水土流失治理标准的确定有3个参考值:1)标准值,即一定条件下的容许土壤流失量,是水土流失治理至少要达到的目标,且随着对不同土地利用类型的功能需求与可实施的最佳水土保持措施、以及所在水土流失类型区的侵蚀危害与治理约束条件的不同而不同;2)理想值,即正常自然侵蚀状态下的土壤流失量;3)极端值,即土壤流失量为0,不发生水土流失。水土流失治理应是先控制到现时生态环境与社会经济条件下的容许土壤流失量范围内,逐步达到自然正常侵蚀量或制止水土流失的发生;还应引入环境伦理、环境美学及景观设计等理念,最终实现土地的可持续利用、区域生态系统的健康稳定及人与自然的和谐友好发展。

黄土塬区10m深剖面土壤物理性质研究

土壤水分是影响黄土高原植被生长和生态环境建设的主要因素。已有对黄土高原土壤的持水性能、水分有效性能与移动性能、黄土高原环境的旱化与黄土中水分关系等方面的深入研究[1,2],也有小流域内土壤水分物理性状与地形和利用条件之间关系的具体分析[3,4]。但是这些工作所涉及的土壤剖面深度多为2 m或3 m,深层土壤水分物理参数研究还少有报道。而对于具有深厚土层的黄土塬区,高产农田与多年生林草地在土壤深层产生了不同程度的干燥化[5~7],土壤干燥化的深入探讨需要与剖面土壤物理性质相关联。为此,有必要对植物根系伸展范围以至更深层次的土壤质地、容重、水分特征曲线、饱和导水率、田间持水量以及萎蔫湿度等土壤物理性质进行测定,分析其垂直变化及不同层次的相关性,为土壤深层水分生态和运动规律研究提供基础参数。1材料与方法1·1研究区概况野外测定点位于陕甘交界处的中国科学院长武农业生态试验站的黄土塬面上。所在区域为典型的黄土高塬沟壑区,属暖温带半湿润大陆性季风气候,年平均气温9·1℃。降水年际变异大,多年平均降水量为584·1 mm,主要集中在7月至9月,约占全年降水量的55%以上。塬地主要土壤类型为黑垆土,母质为马兰黄土,非饱和层深厚...

功能化聚喳琳的合成与性质

为了合成功能化聚哇琳（如质子传导聚喳琳或旋光性聚唆琳）和研究聚哇琳结构与性能之间的关系，合成了含毗咯基单元或含联蔡基单元的聚喳琳和聚葱琳，并对其性质进行了研究，主要内容如下：（1）建立了二乙酰吡咯的合成方法；合成并表征了四种二苯酞基一二氨基单体和五种新型的含毗咯基或联蔡基的二乙酞基单体；并对部分合成方法进行了改进，简化了实验步骤，提高了产率。（2）合成、表征了8种含吡咯基单元的聚喳琳和聚葱琳，这些新的聚合物具有较高的玻璃化转变温度（242-339℃）和出色的热稳定性（514-554℃）。与聚葱琳系列相比，聚哇琳具有较高的热稳定性，在普通溶剂中较好的溶解性和较低的最大吸收波长（λamax）。含有2，5-亚吡咯基的固态聚葱琳表现出少见的高人arnax（565nln）和低的带隙能量（2.02eV）。所有的聚合物在溶液中具有很低的光量子效率（0.01％一10-5％）。它们的激发态寿命为0.28-1.29ns。通过比较聚合物异构体的性质，探讨了分子结构，尤其亚吡咯基结构对聚合物电子结构、热力学和光学性质的影响，提出了聚合物主链上毗咯氢和喳琳氮间的氢键模型并对聚合物异构体性质差异给予解释。（3）考察了聚喳琳的电化学性质，结果表明这些聚合物存在1-3个不可逆氧化电位和1-2个不可逆还原电位，这是聚哇琳文献中未曾报道的现象。（4）以氯化锉作稳定剂，DMAc作溶剂，得到稳定的PBM高浓度溶液；以此溶液浇铸成膜，其热力学性能优良；经磷酸乙醇溶液浸渍掺杂的PBM膜，在157℃质子导电率达到1.5x*10-3Scm-1。（5）合成、表征了含联蔡基团的旋光性聚喳琳，这些新的聚合物具有较高的玻璃化转变温度（201-305℃）、出色的热稳定性（420-497℃）和耐溶剂性能。创门的结晶度较低，在浓硫酸中的旋光活性远大于联蔡单体，其旋光值与聚合物手性单元的过量比例成线性关系，但旋光方向却与单体不同。

硅微电子工业的发展限制及对策

简要介绍了硅微电子工业的发展状态、限制及对策.为了保持硅微电子工业的继续发展,主要的对策是利用新的结构材料以及新的器件结构和器件原理.在此基础上,介绍了新形势下硅微电子器件及电路辐射加固的考虑.

具有场板结构的AlGaN／GaN HEMT的直流特性

研制成功具有场板结构的AlGaN／GaN HEMT器件，对源场板、栅场板器件的性能进行了分析．场板的引入减小了器件漏电和肖特基漏电，提高了肖特基反向击穿电压．源漏间距4μm的HEMT的击穿电压由常规器件的65V提高到100V以上，肖特基反向漏电由37μA减小到5．7μA，减小了一个量级．肖特基击穿电压由常规结构的78V提高到100V以上．另外，还初步讨论了高频特性．