合浦珠母贝两个种群染色体组型的分析     

黄荣莲  杜晓东  叶富良 《广东海洋大学学报》2001,21(1):1-5

以北部湾和大亚湾两个地域的野生合浦珠母贝种群为研究对象，采用成贝的鳃组织，经空气干燥法制片进行染色体组型分析。结果表明两地种群的核型公式都为2N=28=16m+6sm+4st+2t，NF=50，但在染色体排序方面表现出较明显的群体差异。并与以往研究报道相比较，分析了不同的实验结果及可能产生差异的原因。  相似文献   

Modelling evolution of stellar emission of galaxies for the nir surveys     

B. Rocca-Volmerange  A. Lançon 《Astrophysics and Space Science》1994,217(1-2):273-278

Recent observational results in the near-IR on distant galaxies and interacting galaxies are clues for modelling evolution of galaxy counts and for testing theories of galaxy formation. Spectrophotometric models, developed in the ultraviolet and visible, were tools essential for such interpretations. So we hereafter present their extension to the near-infrared and preliminary results on radiogalaxies, starbursts and faint counts. The two fundamental objectives are to confirm a merging scenario and to determine the age of the first stellar generation.  相似文献   

Evolution of Population II stars     

Filippina Caputo 《Astronomy and Astrophysics Review》1998,9(1-2):33-61

The current knowledge of the evolution of Population II stars, as observed in galactic halos and globular clusters, is outlined. The recent theoretical results provided by an improved physical understanding of the stars are reported, with a particular emphasis upon those stellar evolutionary phases which are the keystones of the interpretation of globular cluster stars. Within the up–to–date theoretical scenario, the luminosity of the turn–off stars and horizontal branch stars, which are of fundamental importance for distance and age determinations, turns out to be fainter and brighter, respectively, in comparison with previous theoretical computations. The predicted absolute magnitude of RR Lyrae stars is consistent with the bright values suggested from the long distance scale (Sandage 1993), but the slope of the relation between and metallicity ([Fe/H]) agrees with that suggested from the short distance scale (see, e.g., Carney et al. 1992, Clementini et al. 1995), at least with [Fe/H]-1.3. As to the globular cluster ages, the new computations provide younger ages ( 10 Gyr–13 Gyr), weakening the conflict with current cosmological estimates. The recent results derived from the fitting of HIPPARCOS parallaxes of field subdwarfs to the fiducial main sequence of globular clusters are consistent with the up–to–date theoretical models. However, the direct determinations of , which are based on the HIPPARCOS proper motions and trigonometric parallaxes of field RR Lyrae stars, give fainter absolute magnitudes than those obtained from the improved evolutionary models. This seems to suggest that the problem of the globular cluster distance and age is still open. Received 6 April 1998  相似文献   

温度对禾谷缢管蚜生长发育和繁殖的影响     

郭良珍  刘绍友 《广东海洋大学学报》1998,(1)

在人工气候室不同温度下研究了禾谷缢管蚜（RhopqlosiphumPadi（Linnaeus））的生长发育和繁殖。结果表明在10～30℃范围内．随着温度的升高,禾谷缢管蚜的发育速率加快,到一定温度之后又随温度升高而减慢;在25．4℃时,rm值最大为0．4196;在25℃时的种群出生率最高。当种群达稳定状态后,若蚜的比例在25℃时最小,占73．5％,而成蚜的比例最大,达26．4％;随着温度的升高,禾谷缢管蚜的产仔期变短,产仔量减少．但产仔峰值加大,峰值来临时间提前。同时还对极端温度对禾谷缢管蚜存活的影响进行了系统测定。  相似文献   

Measuring short-term population mobility among indigenous Australians: options and implications     

Taylor J 《The Australian geographer》1998,29(1):125-137

"Despite the fact that indigenous Australians are known to be frequently mobile over the short term, statistical information regarding this population movement is grossly deficient.... This paper examines various means by which short-term population movement can be quantified to yield aggregate indicators of demographic impact. First, census data are used to establish the rate and pattern of inter-regional, short-term displacement. This reveals regional urban centres as net recipients of temporary residents while most rural areas experience temporary absenteeism. Secondly, results from household surveys are reported stressing the importance of including visitors to households in the estimation of service populations. Thirdly, administrative data on occupancy in urban hostels are used to derive indicators of the duration of movement."  相似文献   

广东省耕地资源问题及其对策   总被引：7，自引：0，他引：7  

廖金凤 《热带地理》1998,18(2):113-117

通过大量的数字和事实,分析说明广东耕地资源存在的问题：耕地不断减少,人口迅速增加,人多地少的矛盾尖锐;耕地消耗过多,１９８０￣１９９５年平均每年减少２．８９×１０＾４ｈｍ＾２,耕地闲置浪费现象严重;耕地质量下降,水田有机质含量下降０．１６％,中低产耕地约占２／３;农田环境污染严重,受工业三废污染农田达１０．４７×１０＾４ｈｍ＾２;耕地后备资源紧缺。提出的主要对策是节流、保护、挖潜,强化耕地资源保护  相似文献   

Chemical abundances in the young galaxy at z=2.309 towards PHL 957     

Molaro  Centurión  & Vladilo 《Monthly notices of the Royal Astronomical Society》1998,293(1):L37-L41

We present high-resolution Utrecht Echelle Spectrograph spectra of the quasar PHL 957, obtained in order to study the foreground damped Lyα (DLA) galaxy at z =2.309. Measurements of absorption lines lead to accurate abundance determinations of Fe, S and N which complement measurements of Zn, Cr and Ni already available for this system. We find [Fe/H]=−2.0±0.1, [S/H]=−1.54±0.06 and [N/H]=−2.76±0.07. The ratio [Fe/Zn]=−0.44 provides evidence that ≈74 per cent of iron and ≈28 per cent of zinc are locked into dust grains with a dust-to-gas ratio of ≈3 per cent of the Galactic one. The total iron content in both gas and dust in the DLA system is [Fe/H]=−1.4. This confirms a rather low metallicity in the galaxy, which is in the early stages of its chemical evolution. The detection of S ii allows us to measure the S ii /Zn ii ratio, which is a unique diagnostic tool for tracing back its chemical history, since it is not affected by the presence of dust. Surprisingly, the resulting relative abundance is [S/Zn]=0.0±0.1, at variance with the overabundance found in the Galactic halo stars with similar metallicity. We emphasize that the [S/Zn] ratio is solar in all the three DLA absorbers with extant data. Upper limits are also found for Mn, Mg, O and P and, once the dust depletion is accounted for, we obtain [Mg/Fe]_c<+0.2, [O/Fe]_c<+0.4, [Mn/Fe]_c<+0.0 and [P/Fe]_c<−0.7. The [α/Fe] values do not support Galactic halo-like abundances, implying that the chemical evolution of this young galaxy is not reproducing the evolution of our own Galaxy.  相似文献   

RR Lyrae variables in the globular cluster M3 (NGC 5272) — I. BVI CCD photometry     

E. Carretta  C. Cacciari  F. R. Ferraro  F. Fusi Pecci  & G. Tessicini 《Monthly notices of the Royal Astronomical Society》1998,298(4):1005-1020

New BVI CCD photometry is presented for 60 RR Lyrae variables in the globular cluster M3. Light curves have been constructed and ephemerides have been (re)-derived for all of them. Four stars (i.e. V29, V136, V155 and V209), although recognized as variables, had no previous period determinations. Also, the period derived for V129 is significantly different from the one published by Sawyer-Hogg. Light curve parameters, i.e. mean magnitudes, amplitudes and rise times, have been derived.   The discussion of these results in the framework of the stellar evolution and pulsation theories will be presented in a forthcoming paper.  相似文献   

三疣梭子蟹(portunus trituberculatus)不同地理种群内自繁和种群间杂交子一代生长性状的比较   总被引：5，自引：1，他引：4       下载免费PDF全文

高保全  刘萍  李健  戴芳钰  罗云  戴艳菊 《海洋与湖沼》2008,39(3):291-296

采用不同地理种群体内自繁和种群间杂交的方法,进行了自繁和杂交子一代生长性状的比较研究.结果表明,80日龄时的杂交子一代在各项指标都表现出一定的杂种优势(0.24%-13.50%),LS在这5个性状中都高于zL.100日龄时杂交子一代表现出的杂种优势有所下降,杂种优势率在-0.88%-4.13%之间,甲长表现出杂种劣势.120日龄时杂交子一代的杂种优势范围为-1.91%-4.37%,甲长、甲宽表现出杂种劣势.可见不同杂交组合、不同性状、不同时间表现出的杂种优势有显著差异.AN0vA分析表明:80日龄、100日龄、120日龄时,5个生长性状在群体之间存在极显著差异.实验结果表明:三疣梭子蟹4个杂交子一代在生长性状上存在一定程度的杂种优势,可见种内群体间杂交是培育三疣梭子蟹优良新品系的重要方法之一.  相似文献   

中华鳖(Pelodiscus sinensis)5个不同地理种群细胞色素b基因序列变异及种群遗传结构分析   总被引：6，自引：2，他引：4       下载免费PDF全文

张永正  张海琪  何中央  徐晓林  李智强  杜建明 《海洋与湖沼》2008,39(3):234-239

利用线粒体细胞色素b基因序列对中华鳖5个不同地理种群(太湖群体、日本群体、江西群体、台湾群体和乌鳖群体)的种群遗传结构进行分析.以特异引物进行PCR扩增,获得了408bp的基因片断序列.序列分析结果表明,在31个中华鳖个体中,共检测到17个变异位点,获得8种单倍型.日本群体的2种单倍型在其他4个群体中都未检测到,为该群体所特有,日本种群与其他4个群体的遗传距离最远.除日本群体缺乏主体单倍型外,其他4个群体共同拥有主体单倍型Hap.1,江西群体、台湾群体和乌鳖群体的单倍型类型都和其他群体共同享有,没有其特异的单倍型.MP法和NJ法构建的系统发生树显示日本群体的两种单倍型以很高的置信度聚成一支,这与其地理分布存在一定的相关性,其序列上的差异,可以成为种群鉴别的分子标记;另外4个群体的6种单倍型聚合成一大支,但同一个地理区域的群体并未聚成一类,未按照地理位置形成明显的地理格局.  相似文献