运用nrDNA ITS 数据研究角叉菜属(Chondrus)在红藻门中的系统进化地位

测定了角叉菜属(Chondrus)5个代表种的核糖体DNA内转录间隔区(ITS)及5.8SrDNA基因序列。结果表明,角叉菜属ITS区(含ITS1、5.8SrDNA和ITS2)序列长度范围为704—714bp,G+C含量为44.6%—45.7%,变异位点69个,信息位点16个;其中,ITS1和ITS2的长度范围分别为147—149bp和398—404bp。5.8SrDNA长度为158bp,没有变异和信息位点。由MEGA3构建的系统进化树(ME和MP)显示:在进化尺度上,真红藻纲的松节藻科(Rhodomelaceae)与红毛菜纲(Bangiophyceae)亲缘关系较近。在真红藻纲内,杉藻目(Gigartinales)的进化地位相对较高,其次是海膜科(Halymeniaceae)、石花菜科(Gelidiaceae)、红叶藻科(Delesseriaceae)和粉枝藻科(Liagoraceae)等,而松节藻科进化地位相对较低。在杉藻目内,杉藻科(Gigartinaceae)和胶黏藻科(Dumontiaceae)进化关系密切,而形态学特征相似的角叉菜和马泽藻(Mazzaella)亲缘关系非常近。     

Climatic changes in central and eastern Canada inferred from deep borehole temperature data

We analyzed data from 23 boreholes at 19 sites in central and eastern Canada, for the purpose of estimating ground surface temperature (GST) histories. These boreholes were logged down to at least 550 m depth with thermistor probes. Thermal conductivity measurements had been previously made at small depth intervals for the entire depth ranges of most of the boreholes. The temperature profiles of these boreholes do not indicate water disturbance. We estimated terrain effects for each borehole using a time dependent solid-angle method. The thermal perturbations caused by lakes or deforestation near the borehole sites are insignificant in most cases. However, four of the holes were found to be severely influenced by terrain effects. GSTs estimated from the borehole data less influenced by the terraineffects form two groups. The first group, which are generally from data of better quality, show a cold period near the end of the last century before the recent warming trend; the second show it 80–100 years earlier. We consider the former typical of the climate of the Boreal climatic region of Canada. The difference between the two groups may reflect the spacial variability of the climate. Four GST estimates do not belong to either type, and the reasons are discussed.     

Climate change,economic growth and energy policy: A recommended U.S. strategy for the coming decades an editorial

Alan D. Hecht Director of the National Climate Program Office, an Office created by Congress in 1978 to coordinate a U.S. program of climate research and services. The office is located in the National Oceanic and Atmospheric Administration within the Department of Commerce; Bo R. Döös Member of the Swedish Academy of Sciences, is a visiting UCAR scientist (University Corporation for Atmospheric Research) in the NCPO. Views expressed in this editorial are of the authors and do not reflect any official views of UCAR or NOAA, DOC, or other federal agencies within the NCP.     

A PULSED PLASMA JET ACOUSTIC SOURCE FOR PROFILING THE OCEAN FLOOR1

A plasma gun source has been successfully used to obtain sub-bottom profiles. The profiles show better penetration than with a 3-5 kHz source and more resolution than with an air gun. The plasma gun source is compact, self-contained, and requires no complex auxiliary equipment. The device was deployed from large research vessels and a small boat. The plasma gun produces sufficient acoustic energy and with its characteristically short pulse length and broad bandwidth it is an attractive sub-bottom profiler, especially in shallow fresh or salt water.     

Pressure-temperature conditions in the Wadi Kid metamorphic complex: Implications for the pan-african event in SE Sinai

Geothermobarometry using continuous equilibria in pelitic rocks of the central and northeastern Wadi Kid areas, Sinai, yields pressure estimates of 320 MPa (3.2 kbar) and temperature estimates of 565° C and >620° C for staurolite-andalusite zone assemblages and anatectic rocks, respectively. This corresponds to geothermal gradients of 47° C/km and 50° C/km. TheseP-T conditions are shown to be compatible with burial under a volcanic cover. The principal heat source for high-grade metamorphism and anatexis is thought to be rising magmatic diapirs. Uplift was relatively slow and the final stages of heating and early stages of cooling probably occurred isobarically. The data imply a high heat flow regime for the Pan-African event in Sinai.     

Coarse-grained chondrule rims in type 3 chondrites

Relatively coarse-grained rims occur around all types of chondrules in type 3 carbonaceous and ordinary chondrites. Those in H-L-LL3 chondrites are composed primarily of olivine and low-Ca pyroxene; those in CV3 chondrites contain much less low-Ca pyroxene. Average grain sizes range from ～4 μm in H-L-LL3 chondrites to ～10 μm in CV3 chondrites. Such rims surround ～50%, ～10% and ≤ 1% of chondrules in CV3, H-L-LL3 and CO3 chondrites, respectively, but are rare (≤1%) around CV3 Ca,Al-rich inclusions. Rim thicknesses average ～150 μm in H-L-LL3 chondrites and ～400 μm in CV3 chondrites.The rims in H-L-LL3 chondrites are composed of material very similar to that which comprises darkzoned chondrules and recrysiallized matrix. Dark-zoned chondrules and coarse-grained rims probably formed in the solar nebula from clumps of opaque matrix material heated to sub-solidus to sub-liquidus temperatures during chondrule formation. Mechanisms capable of completely melting some material while only sintering other material require steep thermal gradients; suitable processes are lightning, reconnecting magnetic field lines and, possibly, aerodynamic drag heating.CV chondrites may have formed in a region where the chondrule formation mechanism was less efficient, probably at greater solar distances than the ordinary chondrites. The lesser efficiency of heating could be responsible for the greater abundance of coarse-grained rims around CV chondrules. Alternatively, CV chondrules may have suffered fewer particle collisions prior to agglomeration.