快生型大豆根瘤菌（Rhizobium fredii）3．7Kb增效片段的亚克

利用柯氏质粒ｐＬＡＦＲ１为载体构建了快生型大豆根瘤菌Ｂ５２菌株的基因文库，并通过植物结瘤试验筛选到一个３．７Ｋｂ增效片段，将其导入慢生型大豆根瘤菌２２１０，能提高其共生固氮效率。所得高效菌株ＨＮ３２在黑龙江、四川和广西大面积应用，平均增产１１．４％（５）。本文测定了３．７Ｋｂ片段的核苷酸序列，计算机分析发现含有两个开放阅读框架（ＯＲＦｓ）。ＯＲＦ１编码含１９０个氨基酸的多肽，与已报道基因和多肽的同源性很低，但其Ｎ端１９个氨基酸与发根农杆菌的乳糖转移酶高度同源。ＯＲＦ２编码含２３５个氨基酸的多肽，与碗豆根瘤菌的ｈｕｐＥ及苜蓿根瘤菌的糖基转移酶基因显示５４％的同源性。     

快生型大豆根瘤菌3.7Kb增效片段的亚克隆与序列分析

利用柯氏质粒ｐＬＡＦＲ１为载体构建了快生型大豆根瘤菌Ｂ５２菌株的基因文库，并通过植物结瘤试验筛选到一个３．７Ｋｂ增效片段，将其导入慢性型大豆根瘤菌２２１０，能提高其共后固氮效率。     

应用发光酶基因标记检测大豆遗传改造根瘤菌在田间应用中的占瘤率

通过含发光酶基因１ｕｘＡＢ的转座自杀质粒ｐＨＮＣ３，将发光酶基因整合到优良快生型大豆根瘤菌ＨＮ０１基因组中，得到具有发光活性的遗传改造菌株ＨＮＯ１ＬＣ０２，应用ＨＮ０１ＬＣ０２进行无菌盆栽和田间试验，结果表明，无菌盆栽条件下发光工程根瘤菌在黑农３９大豆根系上所形成的根瘤均具有发光活性。并能用Ｘ光片记录下来，利用发光工程根瘤菌所形成根瘤的发光活性，考察了发光工程根瘤菌在田间栽培条件下的检测方法和占瘤     

三叶草素基因在快生型大豆根瘤菌中的表达

研究了三叶草根瘤菌的三叶草素基因在快生型大豆根瘤菌中的表达情况，发现导入的三叶草素基因得到了表达，使快生型大豆根瘤菌获得了产生三叶草素的能力，产生的三叶草素对指示菌产生了抑制作用，并且发现导入的三叶草素基因对受体的共生能力没有影响。     

导入四碳二羧酸转移酶基因对费氏中华根瘤菌共生固氮效率的影响

将来自苜蓿中华根瘤菌(Sinorhizobium meliloti)的四碳二羧酸转移酶基因(dctABD)经pIJ2925克隆到广宿主、稳定性质粒pTR102上,获得诱导型表达的重组质粒pHN202.在此基础上再引入来自pDB30所含的发光酶基因(luxAB)作分子标记,以pTR102为基础构建成带有dctABD和luxAB的重组质粒pHN205.经三亲本接合转移,将重组质粒pHN205导入费氏中华根瘤菌(Sinorhizobium fredii)HNO1,GR3和YC4.与出发菌相比较的盆栽试验结果表明:HN01(pHN205)和GR3(pHN205)分别在宁镇一号和川早一号大豆上能显著提高植株地上部分干重(生物量)和总氮量, YC4(pHN205)在黑龙33大豆上能同时显著提高植株地上部分干重(生物量),总氮量和根瘤鲜重.本研究结果表明:导入dctABD基因对共生固氮效率的增效性与受体根瘤菌和大豆品种等因素有关.以luxAB为报告基因进行的转移接合子培养条件下分离单菌落和共生条件下形成根瘤的发光活性检测结果表明:pHN205可在供试费氏中华根瘤菌中稳定遗传.     

大豆根瘤菌8－1－4A色氨酸营养缺陷突变型的筛选及其原养型回复突变株共生效率的研究

采用转座子Ｔｎ５诱变快生型大豆根瘤菌（Ｒｈｉｚｏｂｉｕｍｆｒｅｄｉｉ）８－１－４Ａ筛选到１０个色氨酸营养缺陷型突变株，植物结瘤试验表明这些菌均失去了结瘤能力。经自发突变，从培养平板和振瘤中分离出２３个色氨酸原养回复突变株，盆栽试验结果表明有２２株的结瘤能力得到恢复，其中有５株的共生效率与出发菌相比有显著提高。对部分回复突变株进行了质粒检测和以标记Ｔｎ５为探针的ＳｏｕｔｈｅｒｎＤＮＡ杂交分析。     

大豆Kunitz型胰蛋白酶抑制剂基因的克隆及其转基因烟草抗虫性初探

从未成熟的大豆叶中提取总ＲＮＡ，利用ＲＴ－ＰＣＲ方法扩增出大豆Ｋｕｎｉｔｚ型胰蛋白酶抑制剂基因单一目的片段，克隆到ｐＢｌｕｅｓｃｒｉｐｔ ＫＳ（＋）ＳｍａＩ位点上。序列分析表明，该基因与报导的序列高度同源：其核苷酸序列及推论的编码氨基酸序列的同源率分别为９９．５％和９８．２％。由此，构建了大豆Ｋｕｎｉｔｚ型胰蛋白酶抑制剂基因的植物高效表达载体ｐＢｉｎＳＫＴＩ。并采用农杆菌介导的叶盘法转化了烟草，获     

导入四碳二羧酸转移酶基因对费氏中华根瘤菌共和固氮效率的影响

将来自苜蓿中华根瘤菌（Ｓｉｎｏｒｈｉｚｏｂｉｕｍ ｍｅｌｉｌｏｔｉ）的四碳二羧酸转移酶基因（ｄｃｔＡＢＤ）经ｐＩＪ２９２５克隆到广宿主、稳定性质粒ｐＴＲ１０２上,获得诱导型表达的重组质粒ｐＨＮ２０２。在此基础上再引入来自ｐＤＢ３０所含的发光酶基因（ｌｕｘＡＢ）作分子标记,以ｐＴＲ１０２为基础建成带有ｄｃｔＡＢＤ和ｌｕｘＡＢ的重组质粒ｐＨＮ２０５。＃? ｄｇ ｕｓ ｓｇ ｒｕｖ ｗｇｋ ｌｆｔｑ,ｕ     

弱碱存在下多苯基取代联苯双酚/二氟二苯酮聚合反应机理的研究

以最新研制的多苯基取代联苯双酚和二氟二苯酮为单体,在 Ｎａ２ Ｃ Ｏ３／ Ｋ Ｆ（或 Ｎａ２ Ｃ Ｏ３／ Ｋ２ Ｃ Ｏ３）存在下,合成了多苯基取代联苯型聚醚酮。考察了不同 Ｋ／ Ｎａ 比值条件下聚合物粘度与时间的关系。结果表明,聚合反应速度随 Ｋ／ Ｎａ 比值增加而加快。基于以上研究结果,提出了 Ｎａ２ Ｃ Ｏ３ ／ Ｋ Ｆ（或 Ｎａ２ Ｃ Ｏ３ ／ Ｋ２ Ｃ Ｏ３ ）存在下多苯基取代联苯双酚与二氟二苯酮的聚合反应机理。     

八肋游仆虫一种富含谷氨酸的蛋白GARP的表达与纯化

为研究游仆虫中含有三核苷酸重复序列的GARP基因编码的GARP蛋白在细胞中的功能,利用定点突变技术,将GARP基因中的TGA突变为通用半胱氨酸密码子TGT.突变后的GARP基因构建于原核表达载体pRSETc中,得到重组质粒pRSETc-GARP,将pRSETc-GARP质粒转化至大肠杆菌BL21(DE3)中,经IPTG诱导,带有纯化标签的重组蛋白His6-GARP获得可溶表达,表达产物与抗His抗体在约26 kDa处有很强的交叉反应.His6-GARP蛋白在不同pH条件下通过两次阴离子交换层析和一次凝胶层析三步纯化达到电泳纯.     

Thermoluminescence response of K2YF5:Tb3+ crystals to photon radiation fields

This investigation has been performed to test the feasibility of using K2YF5:Tb3+ crystals as thermoluminescence dosemeters (TLD). K2YF5 single crystals doped with 0.2, 10.0 and 50.0 at.% of trivalent optically active Tb3+ ions as well as K2TbF5 and undoped K2YF5 crystals have been synthesized under hydrothermal conditions. Polished crystal platelets with thickness of about 1 mm have been irradiated with X and gamma rays in order to study thermoluminescent (TL) sensitivity as well as dose and energy response in terms of the Tb3+ concentration in K2YF5. Within this concentration series, K2YF5 crystals doped with 10.0 at.% Tb3+ have been found to have maximum TL response due to a broad asymmetric TL glow peak at 269 degrees C with good linearity of dose response and reproducibility of dose measurements. After deconvolution, the main dosimetric peak has been revealed to be composed of two individual peaks, both with linear TL response behaviour, centered at 210 and 269 degrees C. As it has been proved, the linear TL signal coefficient for K2Y0.9Tb0.1F5 is almost 10 times greater than that for commercial TLD-100 (LiF:Mg,Ti), irradiated with a 137Cs gamma radiation source at the same conditions. The reported results indicate that K2YF5 crystals doped with Tb3+ have potential as promising materials for radiation dosemeters.     

基于铯光泵磁力仪的地磁噪声补偿技术

针对高灵敏度磁传感器的计量与标定,开展了基于铯光泵磁力仪的地磁噪声补偿研究.在原子谱灯铯光泵磁力仪基础上,用激光替换原子谱灯作为铯光泵磁力仪的光源,设计激光光泵磁力仪,应用于地磁噪声补偿系统,再通过实验对基于以上两型光泵磁力仪地磁噪声补偿系统的磁场补偿能力并进行了分析,实验研究结果表明,基于以上两型铯光泵磁力仪的地磁噪...     

Generation-recombination noise in pseudomorphic Modulation-doped Al/sub 0.2/Ga/sub 0.8/As/In/sub 0.1/Ga/sub 0.9/As/GaAs micro-Hall devices

The noise spectrum in micro-Hall devices based on pseudomorphic Al/sub 0.2/Ga/sub 0.8/As/In/sub 0.1/Ga/sub 0.9/As/GaAs modulation-doped heterostructures was measured between 4 Hz and 65 kHz, allowing components due to thermal, 1/f, and generation-recombination to be characterized. Applying deep level noise spectroscopy (DLNS) in the temperature range of 77-300 K to analyze the generation-recombination part of the spectrum, two electron traps contributing to noise density were identified. An emission activation energy of 474 meV was measured for the dominant trap, corresponding to the well-known DX center originating from the AlGaAs barrier. The other deep level, with an emission activation energy of 242 meV, is probably related to defects in the InGaAs layer. The structures under investigation resulted in high-performance micro-Hall devices: a supply-current-related sensitivity up to 725 V/spl middot/A/sup -1//spl middot/T/sup -1/ at 77 K independent of bias current, a signal-to-noise sensitivity of 155 dB/spl middot/T/sup -1/ and a detection limit of 340 pT/spl middot/mm/spl middot/Hz/sup -1/2/ at 77 K were measured.     

Construction and tests of a heart scanner based on superconducting sensors cooled by small stirling cryocoolers

At the University of Twente, a heart scanner has been designed and constructed that uses superconducting devices (superconducting quantum interference devices (SQUIDs)) to measure the magnetic field of the heart. A key feature is the elimination of liquid cryogens by incorporating cryocoolers. In the design, two coolers are operated in counter-phase to reduce the mechanical interference. In addition to the application of ferromagnetic shields around the compressors, the magnetic cooler interference is reduced by placing the SQUID magnetometers coplanar with respect to the coolers. In this way, the cooler noise was reduced to a level below the intrinsic sensor noise: 0.16 pT/√Hz. A temperature of 60 K was realised with a cool-down time of about 2 h. The corresponding heat load to the coolers is roughly 0.9 W. Magnetocardiograms were recorded inside a magnetically shielded room.     

Improvement in oxidation resistance of the intermetallic compound titanium aluminide by heat treatment under a low partial pressure oxygen atmosphere

The improvement in oxidation resistance of an intermetallic compound TiAl was investigated by means of a new type of surface treatment: heat treatment under a low partial pressure oxygen atmosphere. The specimens treated by this method showed superior oxidation resistance compared with a nickel-base superalloy Inconel 713C during cyclic heating to a temperature of 1173 K in static air. The best conditions for the heat treatment under a low partial pressure oxygen atmosphere were found to be: pressure, 6.7 X 10-³ Pa; temperature, 1273 K; time, 7.2 ks (2 h) or more. It was presumed that the excellent oxidation resistance resulting from this method is due to preferential formation of a thin, strong Al₂0₃ surface layer.     

Degradation of Superconducting Properties in MgB2 by Formation of the MgB4 Phase

Superconducting MgB₂ polycrystalline samples have been fabricated under two different conditions in order to determine the effect of MgB₄ phase. A series of samples was placed in an α-alumina container closed with a cup and fired under high purity argon gas. The other series of samples was placed in an α-alumina boot without any lid and fired under similar conditions. For the first series of samples, we have found pure MgB₂ phase formation and a narrow transition width at 0.4 K. For the second series of samples, significant amount of MgB₄ phase were formed and the T _zero was decreased to 27 K. For both the group of samples magnetization hysteresis loops obtained at various temperature range and applied field up to 2 T. The best J _cmag for the first series of samples was 1.9 × 10⁵ A/cm² at 10 K and 0 T, and for the second series of samples was 0.7 × 10⁴ A/cm² at 10 K and 0 T.     

B4C与NH4Cl生成BN反应的研究

研究了Ｂ４Ｃ,ＮＨ４Ｃl和Ｌi3N在不同条件下的反应,分析了Ｌi3Ｎ及Ｈ２,Ｎ２,ＮＨ３等气体在上述反应中的作用,结果表明,在Ｎ２气氛及１２２３Ｋ温度下,Ｂ４Ｃ与Ｌi3N反应生成hBN,B4C与ＮＨ４Ｃl反应只生成少量hBN,而Ｂ４Ｃ,ＮＨ４Ｃl,Li3N共同反应有大量hBN生成,说明在高温高压下合成cBN的常催化剂Li3N,在常压高温下Ｂ４Ｃ与ＮＨ４Ｃl生成hBN的反应中也起催化作用。     

真空铝热还原LiAlO2制取金属锂的研究

真空金属热还原法是一种具有工业应用前景的炼锂方法。本文对常压下以工业碳酸锂、氧化铝和氧化钙为原料合成LiAlO2以及真空条件下铝热还原LiAlO2提取金属Li进行了实验研究。研究了不同煅烧条件对LiAlO2合成的影响以及不同还原条件对铝热还原制取金属锂过程的影响。结果表明:在制团压力50MPa、煅烧温度1073 K和煅烧时间120 min的条件下,碳酸锂的分解率为98.21%,煅烧产物为LiAlO2和CaO。在还原温度1423 K,时间180min,铝粉过量20%,物料粒度-75μm和制团压力为45MPa的条件下金属锂的还原率为95.50%,铝粉利用率为79.17%。还原渣主要成分为CaO.Al2O3和12CaO.7Al2O3,可用于溶出氧化铝。     

纳米BaTiO3的制备及其负载Ni基催化剂的应用研究

采用溶胶-凝胶法制备了纳米BaTiO₃,用纳米BaTiO₃粉体作载体通过浸渍法制备出Ni/BaTiO₃催化剂,并将其用于CO₂重整CH₄制合成气反应,纳米BaTiO₃粉体粒径为25～60nm,颗粒外貌近似球形,其最佳制备条件为:水解用水量10mL,混合溶液pH=4～5,凝胶化温度343K,973K下煅烧处理,在反应温度为1073K,空速12000mL/(h·g·cat)下,Ni/BaTiO₃催化剂可使重整反应的CH₄和CO₂转化率分别达到94.4％和93.3％。     

Crystallization Behaviour and Mechanical Properties of Zr65Cu18Ni9Al8 Bulk Metallic Glass

Designing and synthesis of cost effective bulk metallic glasses (BMGs) has been of considerable interest during the last decade so that they can be made commercially viable. Among these, Zr-based BMGs have been reported extensively due to their attractive properties. An alloy having composition Zr65Cu18Ni9Al8 was designed and synthesized using 2-3 N pure materials by Cu mould casting. The alloy was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and high temperature differential scanning calorimetry (DSC). Thermal parameters like supercooled liquid region ΔTX, reduced glass transition temperature Trg, γand σ parameters were evaluated. Mechanical properties like microhardness, nanohardness, elastic modulus and fracture strength were measured. The alloy showed wide supercooled liquid region of 129±1 K with improved thermal stability. The alloy has considerable fracture strength along with fair amount of ductility.