一个关于极小子群与超可解性的注记

为了得出一个超可解群的充分条件,利用有限群的π-拟正规子群和半覆盖远离子群的概念。群G的子群H称为G的π-拟正规子群,如果它与G的每一个Sylow子群可交换,群G的子群H称为G的半覆盖远离子群,如果H覆盖或者远离G的某个正规列的每一个正规因子。并将所得的结果推广到一些已知的结论。     

关于有限群超可解性的一种新判定方法

利用子群的弱s-置换性质研究超可解子群的积的问题,并给出群的超可解性的一些判别方法。设群G可以表示为2个子群A和B的积,A在G中拟正规且B为超可解,如果A的Sylow子群的所有极大子群在G中弱s-置换,则G为超可解群。从而得到1个群为超可解群的这样的一种新判别法。     

有限群p-超可解性的一个判别准则

为了得出群的p-超可解性的一些判别准则,引入有限群的z-置换嵌入子群的概念.设z是群G的Sylow子群的完全集,群G的一个子群H称为在G内z-置换嵌入,如果H的每个Sylow子群也是G的某个z-置换子群的Sylow子群,一些已知的结论也得到推广.     

有限群p-超可解性的一个判别准则

为了得出群的p-超可解性的一些判别准则,引入有限群的z-置换嵌入子群的概念。设z是群G的Sylow子群的完全集,群G的一个子群H称为在G内z-置换嵌入,如果H的每个Sylow子群也是G的某个z-置换子群的Sylow子群,一些已知的结论也得到推广。     

指数既不是π-数又不是π′-数的极大子群的交

设G是任意群，群G的Frattini子群Frat（G）定义为G的所有极大子群的交。研究了另一种特征子群π′πFrat（G），即所有指数有限且其指数既不是丌．数又不是π′π-数的极大子群的交，并且得到了与Fratfini子群类似的性质。     

指数既不是π-数又不是π''-数的极大子群的交

设G是任意群,群G的Frattini子群Frat(G)定义为G的所有极大子群的交.研究了另一种特征子群π'πFrat(G),即所有指数有限且其指数既不是π-数又不是π'-数的极大子群的交,并且得到了与Frattini子群类似的性质.     

群的根性的一个问题

假设（R）是群的根性,N是群G的正规子群,记N^-/N＝RR（G/N）.主要利用群的根性的性质来解决哪种根性具有特征性质N1N2^-＝N1^-N2^-这个问题.     

无限群p拟Frattini子群

群G中所有极大子群之交称之为G的Frattini子群。给出一种新的广义的Frattini子群——p拟Fratti—ni子群的定义,并研究基本性质,例如p拟既约性质、p拟可消性质和p拟补充性质等。同时对正规子群,同态像和直积的p拟Frattini子群也进行了研究。     

一类周期FC-群中的两种广义Frattini性质

设π是一个非空的素数集合。对任意群G,定义πFrattini子群为所有指数为π-数的极大子群的交,简记为πFrat（G）。得到如下结果：在任意局部π-可分的周期FC-群G中,设H为G的正规子群,如果H/πFrat（G）为局部π-幂零（局部π-超可解）,那么H为局部π-幂零（局部π-超可解）的。     

两种由群的元素性质所确定的群的根性

讨论群的元素性质与群的根性之间的关系．考虑群的元素性质汐满足条件（1）：如果x是p-的p-元素,且N G,那么xN是G／N的p-元素;满足条件（4）：设N G,如果x∈N是G的p-元素,那么x也是N的p-元素,则群类P1={G}G的每个同态像没有非平凡的p-元素}是p1-根群类．如果p满足条件（1）和条件（2）,x∈N是N的p-元素,且N G,那么x也是G的p-元素,则群类P2={G｜G的每个非平凡的同态像有一个非平凡的次正规p-子群}是p-根群类．如果性质p-满足条件（1）,（2）和（4）,那么P,P2均为根群类且P=P2．     

遗传根群类和半单群类

针对Li X.M分别给出的根群类和半单群类的若干特征性质,提出了根群类和半单群类之间应具有的联系。通过群的一类特殊的正规子群:本质正规子群将根群类和半单群类联系起来,并利用群的根性的一般理论,得到了两个结果:根群类P是遗传的当且仅当其对应的半单群类L是本质扩张闭的;当根群类P是遗传根群类时,根群类P和其对应的半单群类L所决定的群类M是根群类。     

AGE GROUPS OF ANTARCTIC KRILL,EUPHAUSIA SUPERBA DANA,IN THE PRYDZ BAY REGION

ＩＮＴＲＯＤＵＣＴＩＯＮＡｎｔａｒｃｔｉｃｋｒｉｌｌ(ＥｕｐｈａｕｓｉａｓｕｐｅｒｂａＤａｎａ)ｉｓａｋｅｙｏｒｇａｎｉｓｍｏｆｔｈｅＡｎｔａｒｃｔｉｃｍａｒｉｎｅｅｃｏｓｙｓｔｅｍａｎｄａｐｏｔｅｎｔｉａｌｆｉｓｈｅｒｙｒｅｓｏｕｒｃｅ.Ｉｔｈａｓｂｅｅｎｔｈｅｓｕｂｊｅｃｔｏｆｍｕｃｈｒｅｓｅａｒｃｈ.Ｄｅｓｐｉｔｅｔｈｅｌｏｎｇｈｉｓｔｏｒｙｏｆｒｅｓｅａｒｃｈｄａｔｉｎｇｂａｃｋｔｏｔｈｅ1930’ｓ,ｔｈｅｒｅａｒｅｓｔｉｌｌｑｕｅｓｔｉｏｎｓａｂｏｕｔｉｔｓｐｏｐｕｌａｔｉｏｎｓｔｒｕｃｔｕ…     

Age groups of antarctic krill,Euphausia superba dana, in the Prydz Bay region

Age groups of Antarctic krill (Euphausia superba Dana) in the Prydz Bay region were studied by distribution mixture analysis based on length/frequency data collected by R/VJidi during the 1989/1990 and 1990/1991 austral summer. Five age groups were determined, i.e. 1⁺, 2⁺, 3⁺, 4⁺, and 5⁺, or six age groups in all, if the 0⁺ larvae were included. The mean body length of 1⁺ to 5⁺ age groups was 25.70 mm, 40.47 mm, 45.52 mm, 50.52 mm and 54.52 mm respectively. Supposing the difference in body length between successive age groups is a reflection of the early growth, the maximum growth rate occurred during the period from 1⁺ juveniles to 2⁺ subadults (14.77 mm/a). From 2⁺ subadults to 3⁺ adults the growth rate dropped steeply (5.05 mm/a) because at this stage, increase of body length was substituted, to a great extent, by the growth of sexual products. From 3⁺ onwards the growth rate was maintained at a relatively low level and decreased slowly with age. The relative abundance of age groups 1⁺ and 2⁺, in our sample must be much lower than that in the real population owing to both the large mesh size we used and the distribution difference between juveniles and adults. If we left aside 1⁺ and 2⁺ age groups and just looked at the relative abundance of adults, we found that age group 3⁺ dominated the adult population and that the relative abundance decreased sharply with increasing age. If this situation is normal, one can expect an extremely high mortality rate in adults, 82.6% from 3⁺ to 4⁺ and 94.0% from 4⁺ to 5⁺. This is reasonably expectable for the Prydz Bay region. Contribution No. 3702 from the Institute of Oceanology, Chinese Academy of Sciences. The research is an achievement of “NINE FIVE” Key Project of CAS (KZ951-A1-205) and National Key Project (98-927-01).     

Biomass allocation patterns of alpine grassland species and functional groups along a precipitation gradient on the Northern Tibetan Plateau

Variations in the fractions of biomass allocated to functional components are widely considered as plant responses to resource availability for grassland plants. Observations indicated shoots isometrically relates to roots at the community level but allometrically at the species level in Tibetan alpine grasslands. These differences may result from the specific complementarity of functional groups between functional components, such as leaf, root, stem and reproductive organ. To test the component complementary responses to regional moisture variation, we conducted a multi-site transect survey to measure plant individual size and component biomass fractions of common species belonging to the functional groups： forbs, grasses, legumes and sedges on the Northern Tibetan Plateau in peak growing season in 2010. Along the mean annual precipitation （MAP） gradient, we sampled 7o species, in which 2o are in alpine meadows, 20 in alpine steppes, 15 in alpine desert-steppes and 15 in alpine deserts, respectively. Our results showed that the size of alpine plants is small with individual biomass mostly lower than 1.0 g. Plants keep relative conservative component individual responses moisture functional fractions across alpine grasslands at the level. However, the complementary between functional components to variations specifically differ among groups. These results indicate that functional group diversity may be an effective tool for scaling biomass allocation patterns from individual up to community level. Therefore, it is necessary andvaluable to perform intensive and systematic studies on identification and differentiation the influences of compositional changes in functional groups on ecosystem primary services and processes.     

Indigenous Knowledge on Soil Classification of Ethnic Groups in Luang Prabang Province of the Lao PDR

Introduction Traditional agriculture based on indigenous knowledge (IK) has been practiced in many areas for centuries. Such practices are often the basis of very sustainable technologies, which are potentially suitable for developmental programs. Polthanee (2001) reported that such farmer practices have been repeatedly found to be valid, rational and usually suited to the local environmental conditions. Moreover, with increased under- standing of agro-ecosystems, professionals in agricultura…     

Herbage Production and Species Richness in Sub-alpine Grasslands of Different Soil Parent Material in Northern Greece

Several abiotic and biotic factors were investigated as possible predictors of local species richness in two sub-alpine grasslands of Jenna and Belles Mountains in Northern Greece.For species richness modelling a hierarchical modelling framework based on generalized additive models was adopted.The two sub-alpine grasslands differed in aspect,altitude and soil parent material（volcanic origin,mostly trachyte,and andesite（TA） for Jenna and metamorphic rocks,mostly gneiss（G） for Belles）.12 fenced squared plots,16 m2 each,were used per grassland,where soil properties,herbage production,species presence and cover of grasses,legumes and forbs were estimated.Mean herbage production was significantly affected by slope and altitude,soil K content and floristic composition as expressed by an ordination axis.Soil p H,floristic composition and average herbage production were significant predictors of forbs and total species richness.For the former,soil N content and for the latter the occurrence of Agrostis capillaris,were also included as significant terms in the predictive model.Thepredictors for grasses species richness were N content,having a positive effect,and average herbage production.In all cases higher species richness was predicted for intermediate values of average herbage production.Differential responses were found between forbs and grasses.The predictors of their species richness were different while for the case of the common predictor（N） the responses of the two groups were also different（grasses species numbers increase and forbs species numbers decreased with increasing N）.Maximum species richness of grasses was observed at relatively low production levels while forbs species richness maximized at relatively high production levels.