The discovery of crown ethers

The discovery of the crown ethers stemmed from efforts to control the catalytic activity of vanadium and copper by complexation with multidentate ligands. The first crown ether, 2,3,11,12-dibenzo-1,4,7,10,13,16-hexaoxacyclo-octadeca-2,11-diene, was obtained in 0.4% yield during an attempt to prepare a phenolic ligand from catechol and bis(2-chloroethyl)ether. This compound, which complexed with the sodium cation, was the first compound known to display such activity and became known as dibenzo-18-crown-6, an 18-atom heterocycle containing 6 oxygen atoms. Some 60 related compounds were made involving heterocyclic rings containing 12 to 60 atoms including 4 and 10 oxygen atoms. There are optimum polyether ring sizes for the different alkali metal cations: 15 to 18 for sodium, 18 for potassium, and 18 to 21 for cesium. Complexes having polyether to cation ratios of 1:1, 3:2, and 2:1 were prepared. Solubilization of inorganic salts in aprotic solvents, especially by saturated crown ethers, was demonstrated.     

UV irradiation of polycyclic aromatic hydrocarbons in ices: production of alcohols, quinones, and ethers

Polycyclic aromatic hydrocarbons (PAHs) in water ice were exposed to ultraviolet (UV) radiation under astrophysical conditions, and the products were analyzed by infrared spectroscopy and mass spectrometry. Peripheral carbon atoms were oxidized, producing aromatic alcohols, ketones, and ethers, and reduced, producing partially hydrogenated aromatic hydrocarbons, molecules that account for the interstellar 3.4-micrometer emission feature. These classes of compounds are all present in carbonaceous meteorites. Hydrogen and deuterium atoms exchange readily between the PAHs and the ice, which may explain the deuterium enrichments found in certain meteoritic molecules. This work has important implications for extraterrestrial organics in biogenesis.     

Juvenile hormone: activity of aromatic terpenoid ethers

Several aromatic terpenoid ethers possess a high degree of morpho-genetic activity when assayed on the yellow mealworm Tenebrio molitor L. and the milkweed bug Oncopeltus fasciatus (Dallas). The most active compounds were the 3,4-methylenedioxy-phenyl ethers of 6,7-epoxygeraniol and the corresponding ethyl-branched homologs.     

Phenolic ethers in the organic polymer of the murchison meteorite

Seven phenolic acids and many nonphenolic organic acids, including large amounts of meta-hydroxy (3-hydroxy) benzoic acid and 3-hydroxy-1,5-benzene-dicarboxylic acid, were obtained from the organic polymer of the Murchison C2 chondrite upon oxidation with alkaline cupric oxide. The phenolic acids apparently were derived from phenolic ethers in the polymer, which in turn probably were formed from carbon monoxide and hydrogen by catalytic Fischer-Tropsch type reactions in the solar nebula. In contrast, terrestrial polymers such as lignin, humic acid, and coal yield mainly para-hydroxy (4-hydroxy) benzene derivatives by the same oxidation procedure.     

香豆素-3-甲酸芳酯的无溶剂快速合成

在无溶剂的条件下,香豆素-3-甲酰氯与等当量的各种酚钠在室温下研磨可快速地得到香豆素-3-甲酸芳酯(1a～1k)。该法与传统的溶液法相比具有无有机溶剂污染,反应速度快,产率高和后处理简单等诸多优点。     

劳动力选择性转移、人力资本与中国农业生产

该文依据人力资本在城乡部门收益率的不同将劳动力转移划分为3个阶段,并对不同阶段下人力资本对农业生产的作用机制进行了初步的探讨,结果表明:随着选择性转移的持续推进和现代农业技术对人力资本敏感程度的不断提高,劳动力选择性转移对农业生产的制约作用将进一步凸显。     

Selective modification of glutathione metabolism

Glutathione, a tripeptide thiol found in virtually all cells, functions in metabolism, transport, and cellular protection. It participates in the reduction of disulfides and other molecules, and conjugates with compounds of exogenous and endogenous origin. It protects cells against the destructive effects of reactive oxygen intermediates and free radicals. Modifications of glutathione metabolism may be achieved by administration of selective enzyme inhibitors, and also by giving compounds that increase glutathione synthesis. Such effects are useful in chemotherapy and radiation therapy and in protecting cells against the toxic effects of drugs, other foreign compounds, and oxygen.     

Selective bond dissociation and rearrangement with optimally tailored, strong-field laser pulses

We used strong-field laser pulses that were tailored with closed-loop optimal control to govern specified chemical dissociation and reactivity channels in a series of organic molecules. Selective cleavage and rearrangement of chemical bonds having dissociation energies up to approximately 100 kilocalories per mole (about 4 electron volts) are reported for polyatomic molecules, including (CH3)2CO (acetone), CH3COCF3 (trifluoroacetone), and C6H5COCH3 (acetophenone). Control over the formation of CH(3)CO from (CH3)2CO, CF3 (or CH3) from CH3COCF3, and C6H5CH3 (toluene) from C6H5COCH3 was observed with high selectivity. Strong-field control appears to have generic applicability for manipulating molecular reactivity because the tailored intense laser fields (about 10(13) watts per square centimeter) can dynamically Stark shift many excited states into resonance, and consequently, the method is not confined by resonant spectral restrictions found in the perturbative (weak-field) regime.     

无溶剂4,4''-联吡啶高选择性亲核取代反应

通过固相熔融的方法,使4,4′-联吡啶与磺酸酯或苄溴进行反应.结果表明,将反应固体混合物加热到融化,在30 min内完成反应.通过控制反应物的投料比,可以高选择性的产生单取代或双取代4,4′-联吡啶衍生物.当4,4′-联吡啶与磺酸酯或苄溴摩尔比为1.0∶2.1时,生成双取代产物,收率近100%;当摩尔比为10∶1.0时,生成单取代产物,收率达90%.     

抗溃疡病杨树的无性选育

用美洲黑杨作亲本进行有性杂交,以抗溃疡病(Dothiorella gregaria)为选育的主要目标,兼顾生长特性、抗旱、抗寒等性状,筛选出3个优良的杨树无性系—Ⅰ—69杨×美洲黑杨的57号杨和65号杨;Ⅰ—69杨×青杨的1145号杨。     

Selective release of enzymes from bacteria

A group of hydrolytic enzymes, including phosphatases and nucleases, is selectively released from E. coli and certain other Gram-negative bacteria by a process designated as osmotic shock. This procedure involves exposure of the cells to ethylenediaminetetraacetate (EDTA) in 0.5 molar sucrose followed by a sudden osmotic transition to cold, dilute MgCl(2). Osmotic shock also results in an alteration of the permeability barrier of the bacterial cell and a depletion of the pool of acid-soluble nucleotides, but there is no loss of viability. On being restored to growth medium, the shocked cells recover after a lag period. Formation of spheroplasts by treatment with EDTA and lysozyme leads to selective release of the same group of enzymes. We believe that the selectively released enzymes are confined in a region between the bacterial cell wall and the cytoplasmic membrane. Histochemical studies indicate such a localization. Further, the enzyme activities are measurable with intact cells, even when the substrate is a nucleotide, to which whole cells are impermeable. Another piece of evidence concerns a mutant E. coli with a defective cell wall. In contrast to normal bacteria, this organism loses one of these enzymes into the medium in the course of growth. After osmotic shock, the bacteria show reduced uptake of sulfate,betagalactosides, galactose, and certain amino acids. Furthermore, the shock treatment causes the release of nondialyzable factors able to bind sulfate, galactose, and the same amino acids. A possible interpretation of these observations is the following: the binding proteins occupy sites near the bacterial surface, and they may be components of active transport systems responsible for the concentrative uptake of these nutrients.     

秸秆腐熟剂品种筛选试验

对4种腐熟剂品种进行了对比及模式试验。结果表明,4种腐熟剂品种处理比对照(无秸秆还田)增产291.2~371.9kg/hm2,增产率为4.0%~5.1%;比秸秆还田但无腐熟剂的处理增产75.1~155.8kg/hm2,增产率1.0%~2.1%;因此,夏玉米秸秆粉碎还田施用腐熟剂效果良好,4种腐熟剂品种的施用对小麦有增产效果,但各品种之间差异不大,以湖北太阳雨腐熟剂效果较好。     

十溴联苯醚对太平洋鳕精子超微结构的影响

通过扫描电镜和透射电镜观察,研究了不同浓度的十溴联苯醚对太平洋鳕Gadus macrocephalus精子超微结构的影响。结果表明:与对照组相比,浓度为0.5、5、50、500 ng/L的十溴联苯醚对太平洋鳕精子的超微结构无显著影响,而浓度为5000 ng/L的十溴联苯醚对太平洋鳕精子的超微结构影响显著。扫描电镜下观察,在浓度为5000 ng/L十溴联苯醚中暴露2 h和4 h时,太平洋鳕精子的形态与对照组相比无显著变化,8 h时精子细胞核表面出现白色结晶状变化,12 h时精子细胞核破裂。透射电镜下观察,在浓度为5000 ng/L十溴联苯醚中暴露2 h时,太平洋鳕精子的形态与对照组相比无显著变化,4 h时精子出现质膜膨胀,线粒体移位,8 h时出现质膜破裂,线粒体内嵴断裂,甚至溶解,基质变浅,呈空泡样改变,12 h时鞭毛大量脱落堆积,部分微管结构解体甚至消失,线粒体内嵴结构基本消失。研究表明,十溴联苯醚主要作用于精子细胞的质膜、线粒体和鞭毛上,其毒性主要表现为质膜破裂,线粒体空泡样改变,鞭毛大量脱落,轴丝微管结构解体等。     

三明市白花泡桐优树选育的研究

根据对三明市白花泡桐18株优树无性系测定,初步选出了T_（002）、T_（005）和T_（009）三个优良无性系。它们生长快、干形好、抗性强。T_(002)和CK材积有极显著差异,T_（015）和T_（009）与CK有显著差异。无性系树高、胸径、材积遗传力分别为0.288、0.6118和0.611,胸径和材积具中度遗传力,平均材积遗传增益22.17％。可作为优良无性系推广。     

佛手组织培养和Km敏感性试验

以佛手的叶片、茎段为材料,建立了其组织培养系统.研究表明,B5比MS更适合作为诱导佛手愈伤组织的基础培养基,诱导愈伤组织效率较高的培养基配方为B5+2.0 mg·L-1 2,4-D+0.2 mg·L-1ZT和B5+1.5 mg·L-1 2,4-D+1.0 mg·L-1 NAA+0.4 mg·L-1 6-BA.在叶片对卡那霉素敏感性的试验中发现,叶片外植体预培养2 d后进行筛选的效果较好,卡那霉素的适宜筛选浓度为25 rng·L-1.     

粉拟青霉的一种选择培养基

３００ｍｇ／Ｌ硫酸铬铵铜、４ｍｇ／Ｌ代森锌、１８００ｍｇ／Ｌ硫酸铜、１０００ｍｇ／ＬＫＭｎＯ４、１００ｍｇ／Ｌ结晶紫、５０００ｍｇ／Ｌ氯霉素、ｐＨ自然组成的化学抑制剂配方能够有效地抑制土壤杂菌的生长而高频地获得粉拟青霉,获得率可达４０％左右．Ｙ＝２．１７Ｘ＋２的线性表明平皿的粉拟青霉孢子回收数（Ｘ）可较为客观地反映林地土壤该菌的种群数量（Ｙ）．     

森林择伐对林分的影响

以汪清林业局30a来实施择伐作业调查资料为依据，分析了森林择伐对林分的影响。结果表明：择伐可以促进森林更新和生长，缩短择伐周期，调整了林分结构，改善林木组成；并且按照采伐量不大于生长量的原则确定择伐始伐立木直径。     

4-甲氧基-2,2,6,6-四甲基哌啶-1-氧化物及其溴化物的氧化性能研究

本文合成并研究了4-MeO-TEMPO 及其溴化物对醇的氧化性能,结果表明,4-MeO-TEMPO 对NaClO 的氧化性能有较大的促进,是一个较好的 NaClO 氧化反应的助氧化剂;其溴化物本身是一个较好的限制性氧化剂。