一种有发展前途的光电发射体——场辅助转移电子光电阴极

本文介绍一种很有发展前途的负电子亲和势光电发射体——场辅助转移电子光电阴极,其长波阈可达2.1微米。它是一种多层结构,表面具有Cs-O激活的银膜,工作时施加以反向偏置电压的异质结光电发射体。     

溶剂萃取过程动力学研究--Ⅳ.单液滴法研究HEH(EHP)萃取Co2(Ⅱ)的速率与机理

采用单液滴法考察了水相酸度、钴(Ⅱ)在水相和有机相的浓度、萃取剂浓度以及温度和介质等因素对萃取速率的影响。结果表明,萃取反应机理是两步界面连续反应。文中对介质的影响也作了讨论。     

用苯乙烯共聚的方法改性含硫光学树脂的研究

自１９７２年美国ＦＤＡ制定有关配戴镜片的安全性规定以来，镜片的安全性正日益受到重视［１］．聚合物光学材料由于具有质轻、耐破损、价格便宜、易加工成型等优点［１～３］，近年来被广泛用于制作各种眼镜镜片和光学仪器的透镜［４］．对这类材料的要求除具有优良的机...     

农业部饲料质量检测昆明中心建成

由农业部、国家认监委组成的审查认可和计量认证专家评审组对农业部饲料质量监督检测（昆明）中心进行了审查认可和国家计量认证，中心一次性通过审查认可和计量认证。至此，该中心已成为全国第10家农业部饲料质量监督检测中心。昆明中心具备了按相关标准对饲料用鱼粉等115个产品、饲料中盐酸克仑特罗等115个参数进行检验的能力，可承担饲料常规、微量元素、黄曲霉毒素、细菌、霉菌总数等指标的检测。     

瑞士开发出新型细菌检测芯片

瑞士科研人员不久前发明一种微型芯片，可以在数小时内检测出对抗生素产生抗体的细菌。这一技术为开发针对疑难病症的新疗法带来希望。     

现行木制家具有害物质限量标准存在漏洞

不久前，北京市建筑装饰协会室内环境保护委员会指出，家具污染难以解决的关键问题，根本在于国家现行的《木家具中有害物质释放限量》标准存在漏洞，     

用SPME/GC-MS方法检验涉火案件中痕量汽油残留物成分

在纵火、爆炸、凶杀等刑事案件中,经常会遇到痕量汽油残留组分的检验与认定。汽油主要由C12以前的烷烃、烯烃、环烷烃和芳香烃化合物组成。由于涉火案件现场中燃烧介质及其中所含汽油的燃烧时间和燃烧程度都不尽相同,那么残留在介质中的汽油组分多少及轻重组分相对含量会产生较     

兖州煤环己酮抽提物的组成,结构及性质研究

前沥青烯及沥青烯是环己酮抽出物的主要级分，它们与原煤有相近的元素组成，并且分子量较大，因此抽出物的组成与结构较好地反映出原煤的组成与结构，本文通过红外光谱，核磁共振的研究讨论了抽出物中有沥青烯及沥青烯级分的结构特点，并由核磁共振氢谱数据计算抽出物的平均分子结构参数，前沥青烯及沥青烯级分的芳香度分别为０．７２和０．６３。     

华泽兰的七个新的倍半萜

Seven new sesquiterpenoids, namely eupatochinilides Ⅰ-Ⅶ （1-7）, together with eight known compounds, euponin （8）, mollisorin A （9）, niveusin B （10）, 8β-（4＇-acetoxy-tiglyloxy）-3β-hydroxy-6Hβ,7Hα-germacra-1（10）E,4E,11（13）-trien-6,12-olide （11）, eupalinifide B （12）, 8β-（4＇-hydroxytigloyloxy）-5-desoxy-8-desacyleuparotin （13）, 3-deacetyeupalinin A （14）, and 15-hydroxyleptocarpin （15）, were isolated from the ethanolic extract of the whole plant of Eupatorium chinense L. Their structures and stereochemistry were established by spectroscopic methods and GIAO based ^13C NMR chemical shift calculations.     

THE EFFECTS OF IRRADIATION ON THE THERMAL PROPERTIES OF SEMI-CRYSTALLINE POLYAMIDES

Irradiation crosslinking of semi-crystalline polyamides was performed by high energy electronswith various dosages. It is known that the melting behavior of the polymers after irradiation is acomplex phenomenon. In company with the wide angle X-ray diffraction and DSC data of irradiatedand unirradiated polyamides it is possible to develop the local order and perfection of the crystallinitiesslightly which resulted from introduction of intermolecular crosslinking in amorphous region, incl-uding in amorphous-crystalline interface and crystalline defect regions due to irradiation. It canbe explained that slight increase of melting temperature (T_m) and heat of fusion (△H_f) with increasingdosage for both of higher crystallinity nylon 4 and nylon 6. For irradiated lower crystallinity nylons,in contrast, the T_m and △H_f decrease obviously with increasing dosage. In this case, radiation cross-linking "freeze in" the pre-existing morphology, and then the prevention for reorganization duringheating is a dominant effect. The T_m from the second melting for all of the samples were depressed,corresponding with Flory theory. Therefore the crosslinks imposed on the molecules restrainedthe molecular mobility, and that not only depresses the crystallinity but also increases the imperfec-tion of crystallites when the radiated polymer melted and then recrystallized. These are also reflectedin the depression of heat and entropy of fusion as well as the appearance of double melting peakson the DSC thermograms.