元宝枫苗木的水力结构特征

在温室条件下,控制不同干旱梯度,用改良的冲洗法测定了4年生元宝枫苗木的水力结构参数．研究表明,随着小枝水势的降低,水力结构各参数随茎段功能木质部直径的变化可以用不同的方程来模拟;导水率的大小受茎段所在区域的影响,限速区的导水率明显低于非限速区,限速区的存在对苗木个体的生存竞争有利．导水率、比导率和叶比导率都和功能木质部直径和小枝水势呈明显的正相关．较粗茎段的叶比导率远高于多次分枝的未端细小分枝,有利于苗木在干旱时保存那些光合积累较大的器官．在落叶之前,相同直径枝条的胡伯尔值随小枝水势的变化很小,说明苗木水分胁迫主要源于木质部空穴和栓塞．     

Free-energy landscape of a chameleon sequence in explicit water and its inherent alpha/beta bifacial property

A sequence in yeast MATalpha2/MCM1/DNA complex that folds into alpha-helix or beta-hairpin depending on the surroundings has been known as "chameleon" sequence. We obtained the free-energy landscape of this sequence by using a generalized-ensemble method, multicanonical molecular dynamics simulation, to sample the conformational space. The system was expressed with an all-atom model in explicit water, and the initial conformation for the simulation was a random one. The free-energy landscape demonstrated that this sequence inherently has an ability to form either alpha or beta structure: The conformational distribution in the landscape consisted of two alpha-helical clusters with different packing patterns of hydrophobic residues, and four beta-hairpin clusters with different strand-strand interaction patterns. Narrow pathways connecting the clusters were found, and analysis on the pathways showed that a compact structure formed at the N-terminal root of the chameleon sequence controls the cluster-cluster transitions. The free-energy landscape indicates that a small conditional change induces alpha-beta transitions. Additional unfolding simulations done with replacing amino acids showed that the chameleon sequence has an advantage to form an alpha-helix. Current study may be useful to understand the mechanism of diseases resulting from abnormal chain folding, such as amyloid disease.     

黄河故道不同灌水方式刺槐人工林幼树水分利用效率和生长特性

干旱一直是限制黄河故道沙区树木生长的重要因素之一,而刺槐(Robinia pseudoacacia)以其较强的耐旱性、较高的成活率在造林时备受重视。适宜的灌水方式不但可以提高当地水资源的高效利用,而且可以促进刺槐迅速生长,改善当地环境生态。因此,在2011至2012年间,对黄河故道沙地进行刺槐人工林的建设与培育,开展滴灌(DI)、沟灌(FI)和软管喷灌(HSI)3种灌水方式对刺槐人工林幼树水分利用效率(WUE)和生长特性影响的研究。结果表明,在不同的水文年份,滴灌刺槐的净光合速率(Pn)、蒸腾速率(Tr)高于软管喷灌,软管喷灌高于沟灌。水分利用效率受年份影响较大,但均表现为前期下降,8月份前后降到最低值,随后缓慢回升。不同灌水方式叶绿素含量(CC)差异显著,滴灌条件下刺槐叶绿素含量最高,其次为软管喷灌,沟灌最低。不同树龄,不同灌水方式刺槐株高、地径和胸径差异显著。一年生林,滴灌刺槐的株高、地径和胸径分别比软管喷灌高出23.4、0.27 cm和0.14 cm;二年生林,滴灌刺槐的株高、地径和胸径分别比软管喷灌高53.7 cm、0.61 cm和0.54 cm。滴灌刺槐的株高、地径和胸径的年度生长量分别为软管喷灌的112.1%、107.1%和111.8%,同时分别为沟灌的121.8%、191.8%和343.6%。不同灌水方式刺槐幼树水分利用效率受年际间气象因素影响较大,滴灌可以显著地改善刺槐幼树的光合生理特性,促进其快速生长。     

Temperature dependence on the pesticide sampling rate of polar organic chemical integrative samplers (POCIS)

Laboratory experiments were performed to determine the sampling rates of pesticides for the polar organic chemical integrative samplers (POCIS) used in Japan. The concentrations of pesticides in aquatic environments were estimated from the accumulated amounts of pesticide on POCIS, and the effect of water temperature on the pesticide sampling rates was evaluated. The sampling rates of 48 pesticides at 18, 24, and 30 °C were obtained, and this study confirmed that increasing trend of sampling rates was resulted with increasing water temperature for many pesticides.     

A random fatigue of mechanize titanium abutment studied with Markoff chain and stochastic finite element formulation

To measure fatigue in dental implants and in its components, it is necessary to use a probabilistic analysis since the randomness in the output depends on a number of parameters (such as fatigue properties of titanium and applied loads, unknown beforehand as they depend on mastication habits). The purpose is to apply a probabilistic approximation in order to predict fatigue life, taking into account the randomness of variables. More accuracy on the results has been obtained by taking into account different load blocks with different amplitudes, as happens with bite forces during the day and allowing us to know how effects have different type of bruxism on the piece analysed.     

An insect cell line discrimination method by RAPD-PCR

Summary RAPD-PCR with a tenmar single primer for discrimination of insect cell lines was devised. The base sequence of the primers used were TTCGAGCCAG, CCGCATCTAC, GAACGGACTC, and TGAGTGGGTG (GC contents were 60%). Genome DNA was extracted by modified Landry et al. (1993) method. The reaction mixture consisted of 10 μl buffer, 8 μl dNTP mixture (2.5 mM each), 4 μl primer (50 μM), Taq DNA polymerase (2.5 units), 1 μl template DNA; and the reaction was run at 94° C for 2 min (denaturation), followed by 31 cycles of 94° C for 1 min, 42° C for 1 min (annealing), and 72° C for 2 min (extension) and terminated with 72° C for 7 min. By developing the reaction products with agarose gel electrophoresis, it became evident that DNA fragments were amplified with all the primers used. Among four primers, the second primer was selected as a suitable primer for distinguishing cell lines. With this method, cell lines derived from different species were clearly distinguished.     

Sensitive method for determination of DON in cocoa by means of HPLC-techniques

The mycotoxin deoxynivalenol (DON) is one of a group of mycotoxins known as type B trichothecenes and is particularly formed by the mould speciesFusarium graminearum andFusarium culmorum. The frequency of the occurrence of DON in certain raw materials and the concentrations found make it one of the world’s most significant mycotoxin contaminants. Positive findings of the toxin especially have been established in cereal-based foods, as well as in oilseeds. The main objective of this study was to set up a current situation assessment of the possible occurrence of deoxynivalenol in cocoa and cocoa products. As there was no analytical method for determining DON in cocoa and cocoa products, a special method was developed. The applicability and consistency of the method was confirmed by performing recovery assays on various cocoa products. A special post-column derivatisation procedure was developed to increase selectivity and raise sensitivity by a factor of 80. The method was used to test 230 samples for possible DON content, ranging from cocoa beans to cocoa bean shells, nibs, cocoa liquor and cocoa powders through to finished cocoa-based products. The results suggest that DON may occasionally occur in cocoa beans in very low concentrations. Presented at the 29^th Mykotoxin-Workshop, Fellbach, Germany, May 14–16, 2007     

荧光定量PCR技术评价亚甲蓝光化学法病毒灭活效果的研究

本研究探讨利用荧光定量PCR技术评价Sindbis病毒经亚甲蓝光化学处理后灭活效果的可行性。研究采用不同光照强度对Sindbis病毒进行亚甲蓝光化学灭活处理,并用SYBR Green I荧光定量PCR对Sindbis病毒的cDNA进行扩增,同时以细胞病变法做平行对照以测定病毒残余滴度。结果显示在亚甲蓝光化学处理过程中,随着光照强度的增强,病毒残余滴度由6.50 LgTCID50/mL逐渐降低至检测限以下,同时病毒核酸的拷贝数显著下降(P<0.05),并与病毒感染性的降低呈线性相关(R2>0.98)。以上结果表明,亚甲蓝光化学灭活法对Sindbis病毒核酸有破坏作用,病毒核酸损伤程度随光照强度的增强而增加,且与病毒感染性的降低存在相关性,提示荧光定量PCR技术评价亚甲蓝光化学法的病毒灭活效果具有可行性。     

Activation of protease by sol-gel entrapment into organically modified hybrid silicates

To prepare an immobilized protease with a high activity for transesterification of vinyl n-butyrate with 3-methyl-1-butanol (isoamyl alcohol) in organic media, a protease was entrapped into organic–inorganic hybrid silica gel on Celite 545 by the sol-gel method. When propyltrimethoxysilane was used as the organic silane precursor mixed with tetramethoxysilane at a molar ratio of 16:1, the hybrid gel-entrapped protease on Celite 545 had 8 times the activity of the protease deposited on Celite 545 from 35 to 85°C.     

Clerodane and labdane diterpenoids from Nuxia sphaerocephala

Seven diterpenoids including four clerodane and three labdane derivatives, (13S)-ent-7beta-hydroxy-3-cleroden-15-oic acid (1), ent-7beta-hydroxy-2-oxo-3-cleroden-15-oic acid (2), ent-2,7-dioxo-3-clero-den-15-oic acid (3), ent-18-(E)-caffeoyloxy-7beta-hydroxy-3-cleroden-15-oic acid (4) (13S)-ent-18-(E)-coumaroyloxy-8(17)-labden-15-oic acid (5), ent-18-(E)-caffeoyloxy-8(17)-labden-15-oic acid (6), ent-15-(E)-caffeoyloxy-8(17)-labden-18-oic acid (7), have been isolated from an ethyl acetate extract of the leaves of Nuxia sphaerocephala, together with 17 known compounds. 3-Oxolup-20(29)-en-30-al (3-oxolupenal) (8) and 3beta-hydroxylup-20(29)-en-30-al (3beta-hydroxy-lupenal) (9) showed the best inhibitory activity against Plasmodium falciparum with the IC(50) values between 1.55 and 4.67 microg/ml in vitro, respectively. The structure and the relative stereochemistry of the compounds were established on the basis of their spectroscopic properties. The absolute configuration at C-13 of 1 and 5 was determined by the PGME amide procedure.