Paleontology and Chronology of Two Evolutionary Transitions by Hybridization in the Bahamian Land Snail Cerion

The late Quaternary fossil record of the Bahamian land snail Cerion on Great Inagua documents two transitions apparently resulting from hybridization. In the first, a localized modern population represents the hybrid descendants of a 13,000-year-old fossil form from the same area, introgressed with the modern form now characteristic of the adjacent regions. In the second case, a chronocline spanning 15,000 to 20,000 years and expressing the transition of an extinct fossil form to the modern form found on the south coast was documented by morphometry of fossils dated by amino acid racemization and radiocarbon. Hybrid intermediates persisted for many thousands of years.     

Volatiles from the 1994 Eruptions of Rabaul: Understanding Large Caldera Systems

The 1994 eruption of Rabaul, in Papua New Guinea, involved a small plinian eruption at Vulcan and a vulcanian eruption on the opposite side of the caldera at Tavurvur. Vulcan's ash leachates indicate seawater interaction that is consistent with earlier observations of low sulfur dioxide emissions and the presence of ice crystals in the initial plinian eruption cloud. In contrast, Tavurvur ash leachates indicate no seawater interaction, and later sulfur dioxide emissions remained high despite low-level eruptive activity. Silicic melt inclusions indicate that the andesitic melt contained about 2 weight percent water and negligible carbon dioxide. Mafic melt inclusions in Tavurvur ash have water and carbon dioxide contents that vary systematically over the course of the eruption. The mafic melt inclusions suggest that a mafic dike intruded from below the silicic chamber and provide further evidence that mafic intrusions drive caldera unrest.     

不同淹水程度对长江滩地枫杨组织比量的影响及变异

研究结果表明：在径向上,阉水1个月和2个月的两组间,除导管比量变化趋势基本相反外,纤维比量、轴向薄壁组织比量和木射线比量变化趋势相近似。在轴向上,两组间纤维比量和木射线比量随树高的增加变化趋势相反,导管比量和轴向薄壁组织比量随树高的增加变化趋势相似。第一组和第二组的纤维比量分别为65．89％、62．7％;木射线比量分别为12．22％、15．07％。经T－检验,在0．05水平上,纤维比量和木射线比量在两组间差异显著,而导管比量和轴向薄壁组织比量差异不显著。     

地上部生长性状指标在小麦耐铝性筛选中的应用

在大容积溶液培养和小盆钵土培试验中采用地上部生长性状和根系生长性状指标对小麦基因型进行了耐铝性筛选.结果表明,供试的24个基因型的耐铝性存在极显著的差异.无论是相同或不同的筛选方法,地上部耐性指数如相对株高和相对地上部干重与根系耐性指数如相对根长和相对根系干重均呈极显著的正相关.根系耐性指数的SD、CV及分布范围较大,区分不同基因型耐铝性差异的灵敏度较高.地上部耐性指数的SD、CV及分布范围较小,反映基因型间耐铝性差异的灵敏度相对较低,但地上部也可作为可靠的耐铝性筛选指标.地上部生长性状指标尤其是株高不仅测定快速、容易,而且可以无损伤地测定而不影响后续研究的进行,可用于大规模的种质筛选或育种项目中.所采用的2种筛选方法能克服传统筛选方法如小体积溶液培养、土培和田间试验的繁琐、费时和筛选效率低的缺点,具有快速简便,一次可筛选较多样本,且条件易于控制等优点,因而大大地提高了筛选的可靠性和筛选效率.     

潜香物质地支普内酯及其葡萄糖甙的研究进展

概述了能产生重要烟草致香物质猕猴桃内脂的潜香物－－地支普内酯和地支普内脂－β－Ｄ－吡喃葡萄糖甙的分离纯化和结构鉴定，文中论述了两个潜香物质的结构特征，研究的它们的降解和热解反应。结果表明，这两个潜香物是卷烟行业和食品行业重要的添加剂，对提高烟气质和掩盖刺激作用显著，从而支持潜香理论学说。     

家禽日粮中电解质平衡的研究进展

阐述家禽电解质平衡与酸碱平衡的关系、 DEB计算方法、电解质平衡对生产性能、蛋壳质量、营养物质利用率、肉鸡腿病、肉鸡猝死症和腹水症的影响     

镁对肉鸡生长发育及组织中矿物元素含量的影响

在玉米淀粉——大豆分离蛋白型纯合基础饲粮中,加入不同水平的镁(MgSO_4·7H_2O),喂饲56日龄(满8周龄)肉鸡(星布罗 D 系母雏鸡),研究了镁对肉鸡生长发育及组织中矿物元素含量的影响。结果表明,饲粮镁水平对肉鸡体重、采食量、饲粮利用效率都无显著影响(P>0.05),添加镁使血液和胫骨镁含量显著提高(P<0.05),使胫骨钙和磷含量显著降低(P<0.05)。     

植物耐荫性研究的意义与现状

阐述了植物耐荫性研究的意义及国内外研究现状，以促进植物耐荫性和耐荫植物资源开发利用的研究。     

Radar detection of the nucleus and coma of comet hyakutake

Radar observations of comet Hyakutake (C/1996 B2) made at the Goldstone Deep Space Communications Complex in California have detected echoes from the nucleus and from large grains in the inner coma. The nucleus of this bright comet was estimated to be only 2 to 3 kilometers in diameter. Models of the coma echo indicate backscatter from porous, centimeter-size grains ejected anisotropically at velocities of tens of meters per second. The radar observations suggest that a comet's activity may be a poor indicator of its size and provide evidence that large grains constitute an important component of the mass loss from a typical active comet.     

林分密度管理图编制的研究

云南松、华山松是西南地区的主要用材树种。为了研究林木密度与林木生长之间的关系，更好地经营管理好云南松林和华山松林，在引进国内外编图的理论和方法的基础上，我们编制了滇中地区、南盘江林区的云南松和广元林区的华南山松人工林林分密度管理图。按典型选样法所设置的样地，基本能代表该地区云南松和华山松的生长情况，其中，滇中地区云南松林内设置样地493块，南盘江林区云南松林内设置样地305块，广元林区华山松林内设置样地252块。本文不仅在数据惧和整理方法上做了说明，而且以数表的形式了说明了数学模型的选择以及最大密度线、等树高线、等直径线、等疏密度线和自然稀疏线的绘制方法。成图后进行了理论和适用精度检验，其理论精度均在91％以上，适用精度均在85％，证明本设计适用于该林区。该图可用于抚育间伐、资源清查、生长量预测及造林设计等。