冰点调节剂对西兰花冰点的控制研究

本文研究不同冰点调节剂对西兰花冰点的影响。实验选取葡萄糖、维生素C、氯化钙和山梨醇四种冰点调节剂,利用单因素比较实验法,系统研究了冰点调节剂种类及其使用条件对西兰花冰点的影响。结果表明,氯化钙是较好的冰点调节剂;3％氯化钙浸泡30rain对西兰花的冰点调节效果较好,使西兰花冰点从-0．8℃降到．1℃。     

食品安全相关人群食品安全知识、态度和行为横断面调查

目的 了解食品安全相关人群的知识、态度和行为(KAP)现状并探讨其影响因素,为实施改善食品安全状况的具体措施提供参考.方法 本调查采用多阶段分层随机抽样的方法对我国15个省/直辖市/自治区抽取食品从业人员、食品专业技术人员以及食品监管人员,共计18802名.采用网络调查法对三类人群进行食品安全KAP问卷调查,并采用SP...     

乙硫氮作捕收剂时无机调整剂加药顺序对典型硫化矿物浮选的影响

研究了乙硫氮作捕收剂时无机调整剂硫酸锌、亚硫酸钠、硫化钠和硫酸铜不同加药顺序对典型硫化矿物黄铜矿、方铅矿、闪锌矿和黄铁矿浮选行为的影响.结果 表明,调整剂与捕收剂的加药顺序对硫化矿物浮选的影响不同.与调整剂先加时相比,乙硫氮先加,硫酸锌对黄铜矿和方铅矿浮选的抑制作用减弱;硫酸锌、低用量硫酸铜、亚硫酸钠或硫化钠对闪锌矿浮...     

北黑电网振荡问题的研究

针对黑龙江省北县电网实际振荡事故，应用特征值法进行计算分析，在得到与实际情况相吻合的仿真计算基础之上，对系统内各种调节器及其参数与系统主特征值之间的关系进行了广泛深入的研究，从而提出了通过修改西沟水电厂机组调速系统参数bt、Td和Tn来增加系统阻尼，解决目前北黑电网存在的振荡问题，最后通过计算给出了各参数最佳定值范围。     

某钼精矿降铜浮选试验研究

通过对粗选抑铜、再磨后精选抑铜两流程方案的试验研究,确定了再磨后精选抑铜的工艺流程及符合环保要求的无氰抑制剂的药剂制度,并在钼精矿品位和回收率基本不降低的情况下,钼精矿含铜达到0.3%以下.     

UPLC-MS/MS法同时测定豆芽中氟喹诺类药物和生长调节剂

目的? 采用GCB、Z-sep+等净化材料改进的QuEChERS-超高效液相色谱-串联质谱法(ultra performance liquid chromatography-tandem mass spectrometry, UPLC-MS/MS)建立一种能够快速、稳定地同时测定豆芽中多种喹诺酮类以及生长调节剂药物残留的分析方法。 方法 样品粉碎,经甲酸乙腈提取,净化包材料净化后,通过保留时间匹配以及母离子、主要碎片离子的精确质量数进行定性分析、基质标准溶液外标定量的方法进行分析。结果 在优化条件下, 9种参数的保留时间在4.9~8.8 min。质量浓度范围在0.010~0.200μg/mL时, 9种参数的线性关系良好, 其相关系数为0.9149～0.9999之间, 检出限(LOD)达到5.0μg/kg,定量限(LOQ)达到10μg/kg。结论 试验方法操作简单、准确, 可快速定性定量分析豆芽中9种氟喹诺类药物和生长调节剂的残留,对实现豆芽种植过程管控、日常监管、质量保障具有重要意义。     

Improvement of Rice Agronomic Traits by Editing Type-B Response Regulators

Type-B response regulator proteins in rice contain a conserved receiver domain, followed by a GARP DNA binding domain and a longer C-terminus. Some type-B response regulators such as RR21, RR22 and RR23 are involved in the development of rice leaf, root, flower and trichome. In this study, to evaluate the application potential of type-B response regulators in rice genetic improvement, thirteen type-B response regulator genes in rice were respectively knocked out by using CRISPR/Cas9 genome editing technology. Two guide RNAs (gRNAs) were simultaneously expressed on a knockout vector to mutate one gene. T₀ transformed plants were used to screen the plants with deletion of large DNA fragments through PCR with specific primers. The mutants of CRISPR/Cas9 gene editing were detected by Cas9 specific primer in the T₁ generation, and homozygous mutants without Cas9 were screened, whose target regions were confirmed by sequencing. Mutant materials of 12 OsRRs were obtained, except for RR24. Preliminary phenotypic observation revealed variations of various important traits in different mutant materials, including plant height, tiller number, tillering angle, heading date, panicle length and yield. The osrr30 mutant in the T₂ generation was then further examined. As a result, the heading date of the osrr30 mutant was delayed by about 18 d, while the yield was increased by about 30%, and the chalkiness was significantly reduced compared with those of the wild-type under field high temperature stress. These results indicated that osrr30 has great application value in rice breeding. Our findings suggest that it is feasible to perform genetic improvement of rice by editing the type-B response regulators.     

锂辉石选矿技术现状及展望

锂是新世纪的能源金属,而锂辉石是锂的重要来源之一。介绍了锂辉石矿的选矿技术进展,详细阐述了锂辉石的选矿工艺、浮选捕收剂和浮选调整剂的研究现状及发展趋势,并展望了锂辉石选矿技术以后的发展方向。     

Covalent Fragment Screening Identifies Rgl2 RalGEF Cysteine for Targeted Covalent Inhibition of Ral GTPase Activation

Ral GTPases belong to the RAS superfamily, and they are directly activated by K-RAS. The RalGEF pathway is one of the three major K-RAS signaling pathways. Ral GTPases do not possess a cysteine nucleophile to develop a covalent inhibitor following the strategy that led to a K-RAS G12C therapeutic agent. However, several cysteine amino acids exist on the surface of guanine exchange factors that activate Ral GTPases, such as Rgl2. Here, we screen a library of cysteine electrophile fragments to determine if covalent bond formation at one of the Rgl2 surface cysteines could inhibit Ral GTPase activation. We found several chloroacetamide and acrylamide fragments that inhibited Ral GTPase exchange by Rgl2. Site-directed mutagenesis showed that covalent bond formation at Cys-284, but not other cysteines, leads to inhibition of Ral activation by Rgl2. Follow-up time- and concentration-dependent studies of derivatives identified by substructure search of commercial libraries further confirmed Cys-284 as the reaction site and identified the indoline fragments as the most promising series for further development. Cys-284 is located outside of the Ral ⋅ Rgl2 interface on a loop that has several residues that come in direct contact with Ral GTPases. Our allosteric covalent fragment inhibitors provide a starting point for the development of small-molecule covalent inhibitors to probe Ral GTPases in animal models.     

超高效液相色谱–串联质谱法筛查芽苗类蔬菜中90种植物生长调节剂和抗生素

对色谱质谱条件、净化方式、提取溶剂、除水剂、净化剂组成和配比等样品前处理条件进行了优化，建立了超高效液相色谱–串联质谱法（ultra performance liquid chromatography-tandem mass spectrometry，UPLC-MS/MS）检测芽苗类蔬菜中11种植物生长调节剂和79种抗生素药物的高通量筛查方法。芽苗类蔬菜样品经1%甲酸乙腈-EDTA-Mcllvaine 缓冲溶液提取、QuEChERS净化，采用ACQUITY UPLC HSS T3色谱柱分离、梯度洗脱，采用电喷雾正负离子模式同时采集的多反应监测模式，基质曲线外标法定量。结果表明，90种化合物的定量限在0.1~15.4 μg/kg范围内，平均回收率范围为36.4%~137.3%，相对标准偏差范围均小于18.6%，实现了芽苗类蔬菜中90种高风险物质的同时、快速、高通量筛查和检测，有利于更充分地了解芽苗类蔬菜的质量安全 问题。