B itte r an d Sw e e t /Um am i Ta s te Re c ep to rs w ith D iffe ren tly Evo lu tio n a ry Pa thw ays

通过生物信息学和系统发育学分析,研究了苦味受体和甜味/鲜味受体的进化途径。结果显示,苦味受体 和甜味/鲜味受体在进化上具有远相关,并且具有不同的进化途径,提示这可能是导致这些受体具有不同功能,传 导不同味觉的原因。

Bird and mammal conservation in Gaoligongshan Region and Jingdong County, Yunnan, China: patterns of species richness and nature reserves

Elevational and latitudinal patterns of species richness for birds and mammals were compared with human population density in relation to nature reserve designation in two areas of Yunnan Province, China. Results suggest that species richness is not the same for the two areas. In Gaoligongshan Region, species richness is inversely correlated with elevation and altitude, while reserve designation is positively correlated with elevation and latitude. In Jingdong County, reserve designations are positively correlated with elevation, but species richness shows no clear trends. In general, the present situation is strongly influenced by human activities. It appears that reserve designation is mismatched with species richness in Gaoligongshan Region, while there is a better fit between the two in Jingdong County. In both areas, however, it appeared that reserves were located primarily in order to reduce conflict with humans rather than to maximize conservation of biodiversity, probably because humans were responsible for forest-especially primary forest-destruction and degradation in the low-lying areas.

微生物降解邻苯二甲酸(O-PA)的动力学

<正> 苯二甲酸及其脂类在石油化工,特别是作为合成工业的增塑剂和韧化剂和在染料制造业中的重要性以及他们对江河湖海的广泛污染而越来越引起人们的关注。Kluwe研究了邻苯二甲酸脂的致癌影响。Kozumbo发现了这种脂类的致突变作用。Kaneshima发现,苯二甲酸浓度在500—1000ppm时毒性甚大;Wilson指出,苯二甲酸钠在500ppm以上时有很大毒性。所以,关于苯二甲酸在天然环境里归趋的研究便相继进行。Ribbons等用测压技术研究了土壤假单胞菌类对苯二甲酸的氧化代谢,证明4,5-二羟基苯二甲酸为其

~(239)Pa���鉴别及其特性

利用60 MeV/u18O离子束轰击天然铀靶,经多核子转移反应生成重丰中子核素239Pa���用放射化学方法从被照射的靶中分离出镤。借助于239Pa���它的子体239U的γ射线观测和分析,鉴别了239Pa,测得239Pa���半衰期为(106±30)min。长寿命同位素,如232Th和238U,可给出一个测定核合成持续时间的可能性,而中等寿命同位素,如235U,则可给出有关产生函数时间历史的信息。总地说来,通过232Th/238U2、35U/238U或244Pu/238U的比率,用公式NA(Δ)/NB(Δ)=(PA/PB)f(λA,λB,S0,λR,Δ)便可推导出宇宙年龄。由239Pa���衰变途径,可简单叙述239Pa���异常长的半衰期对于宇宙年龄估计的影响。

用二异丙酮溶剂萃取~(233)Pa(Ⅴ)

用233Pa���示踪剂,苯作稀释剂,研究了二异丙酮(Di-iso-propyl-ketone)对Pa���溶剂萃取行为。分析了萃取效率与震荡时间、不同种类的无机酸浓度和萃取剂浓度的关系及F-对Pa���剂萃取的影响。结果表明,二异丙酮是萃取Pa���一种优良的萃取剂;二异丙酮-盐酸体系适用于Pa���萃取研究。

甲基异丁基酮萃取Pa(Ⅴ)的研究

为了快速萃取分离Pa,并了解Pa���水溶液中的化学性质,以甲基异丁基酮(MIBK)为萃取剂,苯为稀释剂,以233Pa���示踪剂,研究了盐酸溶液中Pa(Ⅴ)的萃取行为,讨论了萃取时间、盐酸浓度、萃取剂浓度和HF对萃取Pa(Ⅴ)的影响。结果表明,萃取在10 s内达到平衡,甲基异丁基酮能够从大于8 mol/L的HCl溶液中定量萃取Pa,同时HCl介质中加入少量的HF会严重改变Pa���萃取行为。

在pA���撞中K~±,η和ф介子的阈下产生

简要评述了在pA���撞过程中K±,η和ф介子的阈下产生及其对应的物理含义。这些介子的阈下产生都可以在兰州CSR上实现,特别是通过pA���撞实现ф介子的阈下产生还没有看到实验数据的报道。