2008年6月汕头一次特大暴雨天气成因分析

利用常规资料、ncep 2.5°×2.5°6 h再分析资料和卫星云图资料对2008年6月13日～14日汕头地区一次特大暴雨天气过程成因进行了综合分析。结果表明:高低层环流配置为暴雨提供了有利的大尺度环流条件;高低空急流的相互作用是此次暴雨产生的重要原因;中尺度对流云团是此次特大暴雨的直接影响系统;低空急流为暴雨的发生发展提供充沛的水汽和不稳定能量;高低空正负涡度柱和正负散度柱的耦合是产生暴雨的动力机制。     

Three-dimensional structure of an antigen-antibody complex at 2.8 A resolution

The 2.8 A resolution three-dimensional structure of a complex between an antigen (lysozyme) and the Fab fragment from a monoclonal antibody against lysozyme has been determined and refined by x-ray crystallographic techniques. No conformational changes can be observed in the tertiary structure of lysozyme compared with that determined in native crystalline forms. The quaternary structure of Fab is that of an extended conformation. The antibody combining site is a rather flat surface with protuberances and depressions formed by its amino acid side chains. The antigen-antibody interface is tightly packed, with 16 lysozyme and 17 antibody residues making close contacts. The antigen contacting residues belong to two stretches of the lysozyme polypeptide chain: residues 18 to 27 and 116 to 129. All the complementarity-determining regions and two residues outside hypervariable positions of the antibody make contact with the antigen. Most of these contacts (10 residues out of 17) are made by the heavy chain, and in particular by its third complementarity-determining region. Antigen variability and antibody specificity and affinity are discussed on the basis of the determined structure.     

UPLC-MS/MS法测定元胡中4种有机磷农药残留的不确定度评定

[目的]对采用超高效液相色谱-串联质谱法(UPLC-MS/MS)测定元胡中4种有机磷农药残留的不确定度进行评估。[方法]根据JJF 1135—2005《化学分析测量不确定度评定》和JJF 1059.1—2012《测量不确定度评定与表示》中的有关规定,采用UPLC-MS/MS法测定元胡中4种有机磷农药残留。建立测定元胡中4种有机磷残留量不确定度的数学模型,逐层对不确定度来源进行分析,计算各不确定度分量并合成出标准不确定度和扩展不确定度。[结果]当试样中马拉硫磷含量为0.048 57μg/kg时,其扩展不确定度为(0.048 57±0.011 55)μg/kg,包含因子k=2;当试样中氧化乐果含量为0.065 34μg/kg时,其扩展不确定度为(0.065 34±0.016 41)μg/kg,包含因子k=2;当试样中水胺硫磷含量为0.043 14μg/kg时,其扩展不确定度为(0.043 14±0.011 02)μg/kg,包含因子k=2;当试样中三唑磷含量为0.058 36μg/kg时,其扩展不确定度为(0.058 36±0.013 02)μg/kg,包含因子k=2。[结论]影响测定结果不确定度的主要来源为添加回收、标准溶液配制的准确性、测定重复性和方法的准确度,其他因素的影响相对较小。     

黑龙江省春季两次强降雪天气分析

利用NECP 1°×1°再分析资料,针对2006年3月10日和2011年3月13日黑龙江省2次强降雪天气,从环流形势、物理量和影响系统等方面进行了分析。结果表明,2次强降雪天气具有相似的特征,均是在高空槽配合地面蒙古气旋的有利环境条件发生的,低涡切变和辐合区的持续存在提供了动力条件,低空西南急流带来了充沛的水汽输送。物理量分布及冷槽、暖脊等的位置使得2次强降雪落区存在一些差异。     

Reexamination of the Three-Dimensional Structure of the Small Subunit of RuBisCo from Higher Plants

The structure of L(8)S(8) RuBisCo (where L is the large subunit and S is the small subunit) from spinach has been determined to a resolution of 2.8 ?ngstrom by using fourfold averaging of an isomorphous electron density map based on three heavy-atom derivatives. The structure of the S subunit is different from that previously reported for the tobacco S subunit in spite of 75 percent sequence identity. The elements of secondary structure, four antiparallel beta strands and two alpha helices, are the same, but the topology and direction of the polypeptide chain through these elements differ completely. One of these models is clearly wrong. The spinach model has hydrophobic residues in the core between the alpha helices and beta sheet as well as conserved residues in the subunit interactions. The deletion of residues 49 to 62 that is present in the Anabaena sequence removes a loop region in the spinach model. The positions of three mercury atoms in the heavy-atom derivatives agree with the assignment of side chains in the spinach structure.     

一次由河套倒槽影响产生的华北大雪天气分析

利用实况资料和NCEP FNL 1°×1°资料,对2012年12月13日华北大雪天气进行了分析。结果表明,此次降雪过程发生在高空环流较平直的形势下,西风带低槽东移,引导地面冷空气从西北路侵入地面暖倒槽中,与暖湿气流交汇而产生降雪的;深厚的湿层和强烈的水汽辐合为此次大到暴雪提供了充分的水汽条件,暴雪中心位于低层2个水汽通量轴线交汇的南侧;高空副热带西风急流的动量下传是低空偏南急流形成的重要原因,低空西南急流和东南急流的耦合加强,不仅为此次大雪提供了水汽和热量输送,还加强了抬升运动;高层辐散、低层辐合的垂直配置以及暴雪区上空深厚而强烈的上升运动,是强降雪出现的动力条件。     

The global magnetic field of Mercury from MESSENGER orbital observations

Magnetometer data acquired by the MESSENGER spacecraft in orbit about Mercury permit the separation of internal and external magnetic field contributions. The global planetary field is represented as a southward-directed, spin-aligned, offset dipole centered on the spin axis. Positions where the cylindrical radial magnetic field component vanishes were used to map the magnetic equator and reveal an offset of 484 ± 11 kilometers northward of the geographic equator. The magnetic axis is tilted by less than 3° from the rotation axis. A magnetopause and tail-current model was defined by using 332 magnetopause crossing locations. Residuals of the net external and offset-dipole fields from observations north of 30°N yield a best-fit planetary moment of 195 ± 10 nanotesla-R(M)(3), where R(M) is Mercury's mean radius.     

从大体积的PAGE凝胶中纯化长链寡核苷酸的新方法

通过比较从大体积的PAGE凝胶中回收寡核苷酸的不同方法,提出回收未银染的长链寡核苷酸的最佳方案:用12 cm×1.5 cm的PAGE凝胶柱分离DNA,然后将凝胶切成长约0.5 cm的胶条,通过PCR反应挑选含有寡核苷酸的胶条。用2 mL的寡核苷酸洗脱缓冲液回收寡核苷酸,反复提取3次。用装填30 mg硅胶的C18 Sep-Pak反相层析柱进行纯化,最后经过离心冻干后即得到纯化的寡核苷酸,该方法的回收率可达(28.7±2.0)%。     

气相色谱-质谱联用快速检测杨梅中噻嗪酮残留

为杨梅质量安全检测和农药合理使用提供参考,建立气相色谱-质谱联用快速检测杨梅中噻嗪酮残留量的方法,通过试验对提取剂和净化剂进行选择。样品经乙酸乙酯提取,50 mg N-丙基乙二胺(PSA)和10mg多壁碳纳米管(MWCNTs)净化,外标法定量,气相色谱-质谱联用进行检测。结果表明:杨梅中噻嗪酮在加标水平为0.05~2mg/kg时,方法的平均添加回收率为88.74%~94.87%,相对标准偏差为1.84%~6.50%。方法检出限(LOD)为0.01mg/kg,定量限(LOQ)为0.02mg/kg。该方法简便,快捷,满足农药残留分析要求,可用于大量杨梅样品中噻嗪酮残留的快速检测。     

The predicted structure of immunoglobulin D1.3 and its comparison with the crystal structure

Predictions of the structures of the antigen-binding domains of an antibody, recorded before its experimental structure determination and tested subsequently, were based on comparative analysis of known antibody structures or on conformational energy calculations. The framework, the relative positions of the hypervariable regions, and the folds of four of the hypervariable loops were predicted correctly. This portion includes all residues in contact with the antigen, in this case hen egg white lysozyme, implying that the main chain conformation of the antibody combining site does not change upon ligation. The conformations of three residues in each of the other two hypervariable loops are different in the predicted models and the experimental structure.     

村镇生活垃圾重金属含量及其土地利用中的环境风险分析

对全国12个省份72个典型村镇产生的生活垃圾进行采样调查,系统分析了我国村镇生活垃圾的重金属含量及其土地利用的环境风险。结果表明:我国典型村镇生活垃圾中重金属Hg、Pb、Cd、Cr、Cu和Zn的含量分别为(0.74±0.48)、(21.80±17.61)、(3.36±11.01)、(108.63±84.01)、(36.83±10.91)、(80.09±42.24)mg·kg~(-1);依据《城镇垃圾农用控制标准》,Hg、Pb、Cd、Cr的超标率分别是1.74%、3.44%、14.29%、2.09%。村镇生活垃圾土地利用的重金属环境风险评估表明:重金属单因子污染指数大小顺序为CdHgCrCuZnPb,其中Cd和Hg分别为重度和轻度污染;重金属内梅罗综合污染指数为4.08(重度污染),Cd和Hg的贡献最大;重金属潜在生态风险程度依次为CdHgCuPbCrZn,综合潜在生态风险等级为强生态危害。     

HPLC-DAD法测定馒头中胭脂红·诱惑红的含量测定的不确定度评定

[目的]采用HPLC-DAD法测定馒头中合成色素胭脂红、诱惑红的含量,分析评定胭脂红、诱惑红的不确定度.[方法]通过HPLC-DAD法测定馒头中胭脂红、诱惑红的含量方法建立数学模型,对各个不确定度因素进行评估、计算,由此计算合成不确定度,最终给出测量结果在95％置信区间下的扩展不确定度.[结果]试验测定的胭脂红含量测定结果为（4.13±0.32） mg/kg;诱惑红含量测定结果为（6.19±0.40） mg/kg.[结论]研究可为食品中色素检测分析应该采取的针对性措施提供参考依据.     

模糊PID控制无人自转旋翼机飞行姿态仿真

农业植保无人机中自转旋翼机(简称旋翼机)具有机体结构简单、滑跑距离短、飞行高度低和空中失去动力时安全性高等优点,在农业数据采集、农情监测和农业施药等领域广泛应用。文章研究模糊PID控制器控制旋翼机姿态,运用MATLAB作旋翼机飞行姿态仿真。仿真结果显示,该系统在系统阶跃响应下模糊PID控制器相较经典PID收敛时间减少0.04 s,而给定目标角情况下,滚转角和俯仰角误差±0.01°与±0.05°上下。因此,模糊PID控制器可增强PID自适应性与鲁棒性,降低飞行时姿态控制不稳定性,姿态控制效果良好,提高飞行稳定性。     

北京城市森林冠层结构对夏季林内舒适度的影响

于2013-2016年7-8月,利用小气象站观测北京城市森林小气候特征,研究了城市森林冠层结构对人体舒适度的影响。结果表明:①叶面积指数（I_LA）（r=-0.314,P=0.002）,平均叶倾角（A_MT）（r=0.472,P < 0.001）,冠层厚度（H_CT）（r=0.458,P < 0.001）,冠下高（H_CB）（r=0.692,P < 0.001）和冠高比（R_CT）（r=0.254,P=0.014）与林下舒适度（S）显著或极显著相关,其中平均叶倾角、冠层厚度、冠下高与林下舒适度相关性较高;叶面积指数（r=-0.356,P=0.001）,冠高比（r=0.433,P < 0.001）和冠层通透度（P_C）（r=0.738,P < 0.001）与舒适变化强度（d_S）极显著相关,其中冠高比和冠层通透度与舒适变化强度的相关性较高。②利于提高舒适度的平均叶倾角、冠层厚度和冠下高的取值区间分别为27.48°±1.67°,（7.40±0.09）m和（2.67±0.06）m;使林内舒适度优于林外的冠高比和冠层通透度取值区间分别为0.72±0.003和6.51%±0.884%。③平均叶倾角和冠下高的协同作用对林下舒适度的解释程度为51.1%;冠高比和冠层通透度的协同作用对舒适变化强度的解释程度为55.5%。林内舒适度受多个结构指标共同影响,单一指标无法准确预测林内舒适度,如何构建与林内舒适度拟合优度较高的综合结构指数还有待进一步研究。     

蛋白质磷酸化对肌动球蛋白解离及其乙酰化水平的影响

[目的]研究肌球蛋白重链和肌动蛋白磷酸化对其乙酰化水平、肌动球蛋白解离及ATP酶活性的影响,为通过调控磷酸化水平改善肉品嫩度提供理论依据.[方法]以羊背最长肌为材料制备肌肉匀浆液,采用碱性磷酸酶抑制剂(抑制去磷酸化)和蛋白激酶抑制剂(抑制磷酸化)调控其磷酸化水平,在4℃分别孵育0、0.5、4、12、24、48和72 h...     

SPE-HPLC法同时测定大白菜中吡虫啉等5种农药残留方法研究

构建了利用固相萃取-高效液相色谱(SPE-HPLC)同时测定大白菜中吡虫啉、多菌灵、除虫脲、灭幼脲、辛硫磷5种农药残留量的方法。固相萃取采用乙腈萃取,氨基柱净化;高效液相色谱采用C18色谱柱进行分离,最佳色谱条件为:柱温40℃,进样量20μL,检测波长270 nm,选择水与甲醇+乙腈混合液(3+1)作梯度洗脱,流速为1.0 mL/min。结果表明:该方法在0.02~1.0μg/mL浓度范围内有良好的线性关系,5种农药的回收率在88.5%～98.8%之间,相对标准偏差在1.84%～4.62%之间,适用于大部分蔬菜中吡虫啉等5种农药残留量的检测。     

一次青藏高原短时强降水的数值模拟及成因分析

利用NCEP／NCAR提供的水平分辨率为1°×1°的格点资料和WRF模式对2011年8月发生在青藏高原的一次短时强降水进行了数值模拟,并利用模式输出的高分辨率资料对此次降水进行诊断分析。结果表明,WRF模式能够较好地模拟此次高原强降水,较成功地再现了造成降水的系统;降水发生前,35°N附近低层大气有一条东西走向的强气流辐合带生成并东移扩张,这条辐合带在17日16：00开始影响降水中心,使得降水中心低层出现短时的强辐合运动。加上充沛的水汽供应．导致短时强降水的爆发。     

高光谱遥感数据在农作物重金属胁迫调查中的应用

利用高光谱遥感数据对四川崇州地区研究作物进行光谱角匹配识别,结合光化学植被指数,有效划分了可评价区域。随后对采样点处遥感光谱信息进行了提取,运用线性回归及多元回归方法,建立了光学信息与土壤各重金属含量间的经验模型,并结合潜在生态危害指数法进行胁迫等级的划分,取得了良好的调查效果。     

Tertiary structure is a principal determinant to protein deamidation

The protein deamidation process involves the conversion of the amide side-chain moieties of asparagine and glutamine residues to carboxyl groups. This conversion is an unusual form of protein modification in that it requires catalysis by an intramolecular reaction where both the substrate (asparagine and glutamine side chains) and "catalytic site" (the peptide nitrogen of the succeeding residue) are constituents of several consecutive residues along the polypeptide chain. The stereochemical factors governing this process were studied with a data base derived from the neutron crystallographic structure of trypsin from which amide groups and oxygen can be unambiguously differentiated because of their different neutron scattering properties. The neutron structure allowed for the direct determination of those residues that were deamidated; 3 of 13 asparagine residues were found to be modified. These modified residues were clearly distinguished by a distinct local conformation and hydrogen-bonding structure in contrast to those observed for the other asparagine residues. No correlation was found between preference to deamidate and the chemical character of residues flanking the site, as had been proposed from previous peptide studies.