Microorganisms from the late precambrian of the grand canyon, Arizona

An assemblage of cellularly well-preserved, filamentous and spheroidal plant microfossils has been detected in a cherty pisolite bed of the late Precambrian Chuar Group from the eastern Grand Canyon of the Colorado River. This newly discovered microflora, probably among the youngest Precambrian biological communities now known, appears to be of both evolutionary and biostratigraphic significance.     

Alga-like fossils from the early precambrian of South Africa

Micropaleontological studies of carbonaceouis chert from the Fig Tree Series of South Africa (> 3.1 x 10(9) years old) revealed the presence of spheroidal microfossils, here designated Archaeosphaeroides barbertonensis, interpreted as probably representing the remnants of unicellular alga-like organisms. The presumed photosynthetic nature of these primitive microorganisms seems corroborated by organic geochemical and carbon isotopic studies of the Fig Tree organic matter, and is consistent with the geologically and mineralogically indicated Early Precambrian environment. These alga-like spheroids, together with a bacterium-like organism previously described from the Fig Tree chert, are the oldest fossil orgisms now known.     

Archean microfossils showing cell division from the swaziland system of South Africa

A newly discovered population of organic walled microstructures from the Swaziland System, South Africa, is considered to be biological on the following grounds: (i) the structures are carbonaceous and occasionally have internal organic contents; (ii) the population has a narrow unimodal size frequency distribution (average diameter, 2.5 micrometers; range, 1 to 4 micrometers); (iii) the structures are not strictly spherical, but are commonly flattened and folded like younger microfossils; (iv) the sedimentary context is consistent with biogenic origins; and (v) various stages of binary division are clearly preserved.     

Alga-like forms in onverwacht series, South Africa: oldest recognized lifelike forms on Earth

Spheroidal and cupshaped, carbonaceous alga-like bodies, as well as filamentous structures and amorphous carbonaceous matter occur in sedimentary rocks of the Onverwacht Series (Swaziland System) in South Africa. The Onverwacht sediments are older than 3.2 eons, and they are probably the oldest, littlealtered sedimentary rocks on Earth. The basal Onverwacht sediments lie approximately 10,000 meters stratigraphically below the Fig Tree sedimentary rocks, from which similar organic microstructures have been interpreted as alga-like microfossils. The Onverwacht spheroids and filaments are best preserved in black, carbonrich cherts and siliceous argillites interlayered with thick sequences of lavas. These lifelike forms and the associated carbonaceous substances are probably biological in origin. If so, the origins of unicellular life on Earth are buried in older rocks now obliterated by igneous and metamorphic events.     

Aragonite Crystals within Codiacean Algae: Distinctive Morphology and Sedimentary Implications

Morphologic studies of single crystals of aragonite within Codiacean algae reveal characteristic crystal forms produced by two distinctly different modes of calcification. Diagnostic serrated crystals (1 micrometer in length) of aragonite originating within the extracellular sheaths of capitular filaments are incorporated into modern lime sediments and may serve as effective tracers for particles of algal origin. Intracellular calcification within Penicillus dumetosus, previously unueported, is represented by doubly terminated aragonite crystals ranging in size from 48 to 160 micrometers.     

Early proterozoic microfossils and penecontemporaneous quartz cementation in the sokoman iron formation, Canada

Early Proterozoic microfossils from the Sokoman Iron Formation, northeastern Canada, are indistinguishable from those of the Gunflint Formation in both morphology and inferred community structure. The contemporaneity of the Sokoman assemblage with the Bitter Springs-like cyanobacteria of the Belcher Supergroup indicates that differences between the two major types of early Proterozoic microbiotas are primarily ecological and not temporal (evolutionary) in nature. In arenaceous iron formations, microfossils are restricted to peloids and are absent from pore-filling silica interpreted as cement. Cemented arenaceous intraclasts indicate that some of the silica was penecontemporaneous, and the abundance of minus-cement porosity in arenaceous iron formations demonstrates that early (pre-compaction) cementation was common.     

Self-assembly of subnanometer-diameter single-wall MoS2 nanotubes

We report on the synthesis, structure, and self-assembly of single-wall subnanometer-diameter molybdenum disulfide tubes. The nanotubes are up to hundreds of micrometers long and display diverse self-assembly properties on different length scales, ranging from twisted bundles to regularly shaped "furry" forms. The bundles, which contain interstitial iodine, can be readily disassembled into individual molybdenum disulfide nanotubes. The synthesis was performed using a novel type of catalyzed transport reaction including C(60) as a growth promoter.     

Diamond from the dabie shan metamorphic rocks and its implication for tectonic setting

Diamond occurs in ultrahigh pressure metamorphic rocks from Dabie Shan, Anhui Province, eastern China. Diamond-bearing rocks include eclogite, gamet-pyroxenite, and jadeitite. Diamond occurs in a mineral assemblage with coesite and jadeite. The diamonds and diamondiferous rocks of Dabie Shan are interpreted to be the products of ultrahigh pressure metamorphism in the undérthrust basement of the Yangtze continental plate during the early Mesozoic, at greater than 4.0 gigapascals and 900 degrees C. This interpretation is based on the distribution of rock units, the stability field of diamond, and isotopic data indicating a crustal origin for the rocks. Most diamonds occur as euhedral inclusions in garnets and are 10 to 60 micrometers across, although some are up to 700 micrometers across.     

Pioneer 10 infrared radiometer experiment: preliminary results

Thermal maps of Jupiter at 20 and 40 micrometers show structure closely related to the visual appearance of the planet. Peak brightness temperatures of 126 degrees and 145 degrees K have been measured on the South Equatorial Belt, for the 20- and 40-micrometer channels, respectively. Corresponding values for the South Tropical Zone are 120 degrees and 138 degrees K. No asymmetries between the illuminated sunlit and nonilluminated parts of the disk were found. A preliminary discussion of the data, in terms of simple radiative equilibrium models, is presented. The net thermal energy of the planet as a whole is twice the solar energy input.     

Conodont pearls?

Conodonts are zoologically enigmatic, toothlike phosphatic microfossils occurring in marine sedimentary rocks ranging in age from Cambrian to Triassic. Dimpled spheres of less than 1 millimeter in diameter are sporadic associates of conodonts and have identical chemical composition and microstructure. Mineralogy, morphology, and occurrence of these spheres suggest that they are pearls secreted by the conodont-bearing animal.     

Self-assembled silica-carbonate structures and detection of ancient microfossils

We have synthesized inorganic micron-sized filaments, whose microstucture consists of silica-coated nanometer-sized carbonate crystals, arranged with strong orientational order. They exhibit noncrystallographic, curved, helical morphologies, reminiscent of biological forms. The filaments are similar to supposed cyanobacterial microfossils from the Precambrian Warrawoona chert formation in Western Australia, reputed to be the oldest terrestrial microfossils. Simple organic hydrocarbons, whose sources may also be abiotic and indeed inorganic, readily condense onto these filaments and subsequently polymerize under gentle heating to yield kerogenous products. Our results demonstrate that abiotic and morphologically complex microstructures that are identical to currently accepted biogenic materials can be synthesized inorganically.     

Crystallization of NADP-specific isocitrate dehydrogenase

The first crystalline preparation of isocitrate dehydrogenase specific for nicotinamide adenine dinucleotide phosphate has been obtained with enzyme isolated from Escherichia coli. Scanning electron microscopy was employed to elucidate the structure of the crystals, which were found to exist as regular octahedrons ranging in size from 5 to 90 micrometers.     

Starch fossils and the domestication and dispersal of chili peppers (Capsicum spp. L.) in the Americas

Chili peppers (Capsicum spp.) are widely cultivated food plants that arose in the Americas and are now incorporated into cuisines worldwide. Here, we report a genus-specific starch morphotype that provides a means to identify chili peppers from archaeological contexts and trace both their domestication and dispersal. These starch microfossils have been found at seven sites dating from 6000 years before present to European contact and ranging from the Bahamas to southern Peru. The starch grain assemblages demonstrate that maize and chilies occurred together as an ancient and widespread Neotropical plant food complex that predates pottery in some regions.     

Black magnetic spherule fallout in the eastern gulf of Mexico

Large numbers of black metallic spherules ranging in diameter from a few micrometers to over 800 micrometers are raining into the eastern Gulf of Mexico and adjacent areas of western Florida. The composition of the flux, its association with glass spherules and coky particles, and its magnitude point to industrial pollution, probably coal- and coke-burning facilities around the perimeter of the gulf, as the source. Since metallic particles represent only a small fraction of most fly ash, such an influx of large numbers of black magnetic spherules must be symptomatic of a much higher rate of sedimentation of fly ash. The internal microstructures and the general appearance of spherules derived from industrial processes are similar to those of particles derived from cosmic sources. Because of the high potential for contamination in micrometeorite studies, a complete compositional verification of each "cosmic" particle may be necessary.     

不同形态梗丝对卷烟在制品及成品质量的影响

[目的]从改变梗丝形态方面研究对卷烟在制品及成品质量的影响。[方法]通过将不同形态（丝状与片状）的梗丝分别掺入某四类卷烟叶丝中,对烟丝物理指标、成品卷烟物理指标及烟气成分进行分析并采用对比评价和三点检验的方法进行感官质量评价。[结果]研究表明,丝状梗丝的结构更趋向于均匀,掺配丝状梗丝后烟丝弹性及整丝率有所降低,填充值无明显差异;掺配相同比例不同形态梗丝的卷烟硬度和焦油均值存在显著性差异,随着丝状梗丝掺配比例的增加,各检测位点的烟支密度波动有降低的趋势,卷烟的吸阻、硬度及焦油均值差异性显著;掺配相同比例的丝状梗丝对卷烟感官质量有一定的提升,适当提高丝状梗丝的掺配比例对卷烟的感官质量影响较小。[结论]研究可为卷烟成本控制提供一定的参考依据。     

Spatial Organization and Time Dependence of Jupiter's Tropospheric Temperatures, 1980-1993

The spatial organization and time dependence of Jupiter's temperatures near 250-millibar pressure were measured through a jovian year by imaging thermal emission at 18 micrometers. The temperature field is influenced by seasonal radiative forcing, and its banded organization is closely correlated with the visible cloud field. Evidence was found for a quasi-periodic oscillation of temperatures in the Equatorial Zone, a correlation between tropospheric and stratospheric waves in the North Equatorial Belt, and slowly moving thermal features in the North and South Equatorial Belts. There appears to be no common relation between temporal changes of temperature and changes in the visual albedo of the various axisymmetric bands.     

Bacteria as Mediators of Copper Sulfide Enrichment During Weathering

Supergene chalcocite enrichment during weathering is an economically vital natural process that may lead to severalfold increases in the copper content of sulfide deposits. A scanning electron microscope study of chalcocite (Cu2S) from major enriched copper deposits in northern Chile revealed myriad bacterioform bodies in original growth positions near replacement interfaces with remnant hypogene sulfide grains. These minute (0.03 to 0.2 micrometers) chalcocite bodies are interpreted as fossilized and metallized nannobacteria that promoted the fixation of mobilized copper ions. Bacterial activity may thus be a fundamental factor in supergene enrichment of copper deposits.     

Direct Observation of Microscopic Inhomogeneities with Energy-Dispersive Diffraction of Synchrotron-Produced X-rays

Evidence of structural inhomogeneities in two high-transition-temperature superconductors, YBa(2)Cu(3)O(7-delta) and Nd2-xCexCuO4-y, is presented. When samples were illuminated by highly collimated x-rays produced on a synchrotron wiggler, small changes in the lattice were detected over a spatial scale of 10 micrometers. These changes are interpreted as evidence of variations in the oxygen content in one case and in the cerium content in the other; both affect the superconducting properties. The existence of such structural inhomogeneities brings into question whether exotic experimental results obtained from superconducting materials with high transition temperatures actually reflect intrinsic properties.     

鸡新城疫病毒强毒株的分离与鉴定

从河北、天津、北京等省市发病鸡群中分离到8株有血凝性的分离物,其血凝作用可被新城疫阳性血清所抑制,而不能被AIV(H9亚型)、EDS76阳性血清所抑制,表明8株分离物均为新城疫病毒。利用鸡胚终点稀释法对这8株NDV进行了克隆。对8株NDV的毒力指数(MDT、ICPI、IVPI)测定结果显示:MDT在42 9～49 5h之间,ICPI在1 95～2 00之间,IVPI在2 68～2 89之间。表明8株NDV均为新城疫病毒强毒株,其毒力与标准强毒株F48E8相近。各分离毒株经2%磷钨酸负染后,电镜下观察,可见丝状、圆形或不规则形态的病毒粒子,表面有纤突样结构。各毒株的大小不尽相同,粒子直径或长轴在100～500nm之间。     

Transvaal Stromatolite: First Evidence for the Diversification of Cells about 2.2 x 109 Years Ago

The well-preserved fossil remnants of filamentous blue-green algae have been found in petrographic thin sections of a dolomitic limestone stromatolite in the Transvaal Sequence of South Africa. Some of these filaments contain enlarged cells which are interpreted as akinetes. A new species and genus, Petraphera vivescenticula, is proposed for this microfossil, which is morphologically similar to the living cyanophyte genus Raphidiopsis. This would constitute the first known occurrence of cell diversification in the Precambrian with an age of about 2.2 x 10(9) years.