共查询到20条相似文献，搜索用时 15 毫秒
1.
Wong CS 《Science (New York, N.Y.)》1978,200(4338):197-200
The atmospheric input of carbon dioxide from burning wood, in particular from forest fires in boreal and temperate regions resulting from both natural and man-made causes and predominantly from forest fires in tropical regions caused by shifting cultivation, is estimated to be 5.7 x 10(15) grams of carbon per year as gross input and 1.5 x 10(15) grams of carbon per year as net input. This is a significant amount as compared to the fossil fuel carbon dioxide produced from the utilization of oil, gas, coal, and limestone, and bears on the hypothesis of the enhanced sedimentation of marine detritus as a removal mechanism of excess atmospheric carbon dioxide. 相似文献
2.
Berg CA 《Science (New York, N.Y.)》1978,199(4329):608-614
American industry in the 19th century switched from wood to coal as its primary energy resource. The history of this switch is reviewed, along with the history of preceding similar trends in Europe and later trends in the switch from coal to oil and gas. Important conceptual advances in the technology of such basic processes as glassmaking, cementmaking, and steelmaking emerged as the switch from wood to coal proceeded in the United States. These advances may have been more important than the relative prices of wood and coal in motivating the conversion of American industry to the use of coal. The historical role of process advances in determining the choice of energy resources suggests that the physics and chemistry of industrial processes may be as important an area of energy research as the various technologies of energy conversion. 相似文献
3.
Lung cancer and indoor air pollution in Xuan Wei, China 总被引：20，自引：0，他引：20
J L Mumford X Z He R S Chapman S R Cao D B Harris X M Li Y L Xian W Z Jiang C W Xu J C Chuang 《Science (New York, N.Y.)》1987,235(4785):217-220
In Xuan Wei County, Yunnan Province, lung cancer mortality is among China's highest and, especially in females, is more closely associated with indoor burning of "smoky" coal, as opposed to wood or "smokeless" coal, than with tobacco smoking. Indoor air samples were collected during the burning of all three fuels. In contrast to wood and smokeless coal emissions, smoky coal emission has high concentrations of submicron particles containing mutagenic organics, especially in aromatic and polar fractions. These studies suggested an etiologic link between domestic smoky coal burning and lung cancer in Xuan Wei. 相似文献
4.
[目的]探寻生物油中高附加值化合物,提高生物油的利用价值和综合竞争力。[方法]将麦秆在超临界甲醇中醇解液化所得生物油通过减压蒸馏得到轻质组分和重质组分,重质组分(重油)用不同极性及溶解性的溶剂萃取分离。[结果]生物油重质组分(重油)5个馏分中,正己烷馏分(Fz)主要含酚类化合物;苯馏分(FB)主要含酚和环戊烯醇酮;乙醚馏分(FYM)主要含吡喃糖苷和呋喃糖苷;而乙酸乙酯馏分(FY)和丙酮馏分(FBT)经GC/MS检测不到物质。[结论]麦秆超临界醇解液化得到的生物质重质油,含有大量的高附加值化合物。 相似文献
5.
Herman Y 《Science (New York, N.Y.)》1963,140(3573):1316-1317
Two deep-sea cores containing Cretaceous, Paleocene, and Pleistocene sediments from an oceanic rise approximately 500 miles southeast of Cape Town contained well-preserved fossil foraminiferal ooze made up of about 97 percent planktonic forms, including species of Guembelina and Hedbergella. High percentages of particles less than 53 micro in diameter in the Cretaceous and Paleocene sediments indicate a deep-water open-ocean depositional environment. These sediments are the oldest recovered so far from the Indian Ocean. 相似文献
6.
用脱脂小叶锦鸡儿种子粕，加入改性剂和增强剂，制成一种新型ＷＡＢ-８９０１木材胶粘剂。经测定，该胶粘剂的ｐＨ值１３、固体含量２７．２％、固化时间１５０ｓ、粘度１０２ｓ、胶合强度１．８ＭＰａ。用该胶粘剂压制的胶合板，其胶合强度和含水率分别为１．７６ＭＰａ和５．１９％。 相似文献
7.
[目的]对东北羊角芹籽挥发油化学成分进行研究。[方法]采用超临界CO2流体萃取东北羊角芹籽中的挥发油,然后用GC-MS进行成分分析,用峰面积归一化法定量,并与水蒸汽蒸馏法获得的精油成分进行比较。[结果]用从超临界萃取法萃取挥发油中,共鉴定出18种成分,主要成分为芹菜脑（59．5％）、十一烷（18．99％）和柠檬烯（5．23％）。水蒸汽蒸馏法提取芹莱籽,共鉴定出14种成分,主要成分为芹菜脑（21．63％）、十一烷（41．14％）和柠檬烯（13．04％）阻水芹烯（6．82％）。虽然2种方法得到的东北羊角芹籽主要成分的组成不相同,但两者所含芹菜脑都较多,表明东北羊角芹籽挥发油的代表化合物为芹菜脑。[结论]该研究为东北羊角芹籽活性成分的研究提供了理论依据。 相似文献
8.
大蒜精油化学成分研究 总被引：5，自引：0，他引：5
采用超临界CO2萃取技术提取大蒜精油，用GC—MS技术进行化学成分研究，并与溶剂萃取法和水蒸汽蒸馏法所提精油进行对比。超临界萃取后分离得到了具有较高相对含量大蒜素的大蒜精油，明显高于溶剂萃取法和水蒸汽蒸馏法所得。证明超临界CO2萃取技术萃取大蒜精油是一种较理想的方法。 相似文献
9.
为了研究目前低碳背景下如何更好地促进我国农村居民生活能源优化升级,在全国7省农村家庭抽样调查问卷所得数据的基础上,利用线性支出模型对农村居民生活能源消费的结构现状进行分析.研究表明,农村居民生活能源消费已经步入商品化时期但非商品能源的消费并未停止;煤炭、电力以及液化气等商品能源的消费随收入的增加而增加,而非商品能源（薪柴）沦为劣等品其消费随收入的增加而减少;电力以及煤炭的家庭人均消费支出较多;薪柴、煤炭、电力以及液化气的消费需求都随着自身价格的上升而减少,但对价格的变化都不太敏感,煤炭、电力以及液化气等商品能源间存在着互补关系,薪柴与其他种类的能源之间存在着明显的替代关系. 相似文献
10.
樟树5个品系精油组分含量和木材性质的比较研究 总被引：9，自引：0，他引：9
测定了樟树5个品系精油组分含量及木材纤维、导管分子形态特征和木材基本密度等材性性状的变异，结果表明，樟树5个品系间精油含量及精油中主要成份含量差异显著。品系间木材纤维形态（纤维长度、宽度、直径、壁腔比、腔径比、长度比、壁厚）、导管形态特征和木材基本密度等多数性状差异不显著，品系间热水浸提物含量差异显著。浸提前木材基本密度与浸提后木材基本密度间存在着显著的正相关。5个品系中仅芳樟型类木材基本密度与胸径成显著的负相关；根中精油含量与胸径呈显著的正相关。 相似文献
11.
Hiyagon H 《Science (New York, N.Y.)》1994,263(5151):1257-1259
It was recently proposed that subduction of interplanetary dust particles (IDPs) contained in deep sea sediments could have introduced substantial solar helium and neon to the Earth's mantle. However, it is not certain if IDPs would retain solar noble gases during subduction. A diffusion experiment that examined He and Ne in IDPs in a magnetic separate from Pacific Ocean sediments showed that He and Ne would be lost from IDPs within 3 years at 500 degrees C, and possibly within 10(5) years at 200 degrees C, which suggests that they would be lost from subducting slabs at shallow depths. 相似文献
12.
Pruett RL 《Science (New York, N.Y.)》1981,211(4477):11-16
Rapid increases in the price of imported crude oil have accelerated a shift in the raw material base for chemical feedstocks from natural gas to crude oil to coal. Widespread use of ethylene as a feedstock has depended on the availability at attractive prices of natural gas and petroleum. As the resource base shifts from natural gas and petroleum to coal, ethylene is being replaced by synthesis gas (a mixture of hydrogen and carbon monoxide of varying composition), which can be manufactured directly from any of these carbonaceous sources. This trend is expected to accelerate in the 1980's. Organics likely to be produced from synthesis gas include ethanol, ethylene glycol, and vinyl acetate. 相似文献
13.
Analyses of the stable isotopes of the organic carbon and microscopic examination of the sediment particles suggest that up to 90 percent of the organic matter in Ross Sea sediments is derived from the igneous and ancient metamorphic and sedimentary rocks that are being glacially eroded on the Antarctic continent and transported seaward. 相似文献
14.
15.
Anaerobic sedimentary conditions have traditionally been linked to the generation of the source rocks for petroleum formation. However, the influence of sedimentary redox conditions on the composition of freshly deposited organic matter (OM) is not clear. We assessed the effect of in situ exposure time to oxic conditions on the composition of OM accumulating in different coastal and deep-sea sediments using solid-state 13C nuclear magnetic resonance (NMR). 13C NMR spectra were resolved into mixtures of model components to distinguish between alkyl carbon present in protein and nonprotein structures. There is an inverse relation between the length of exposure to oxic conditions and the relative abundance of nonprotein alkyl (alkylNP) carbon, whose concentration is two orders of magnitude higher in coastal sediments with short exposure times than in deep-sea sediments with long exposure times. All alkylNP-rich samples contain a physically separate polymethylene component similar in composition to algaenans and kerogens in type I oil shales. The duration of exposure to oxic conditions appears to directly influence the quality and oil generation potential of OM in marine shales. 相似文献
16.
天津地区表层土壤中菲系列化合物的分布特征和污染源分析 总被引：5，自引：1，他引：4
通过野外采样法,分析了天津地区表层土壤中菲系列化合物中能反映污染物来源的地球化学参数(菲/蒽、甲基菲指数及甲基菲/菲)的空间分布特征,初步讨论了不同环境功能区多环芳烃污染物的来源。结果表明,天津市区、近郊区和汉沽、塘沽的污染物主要是汽车尾气、工业和生活燃煤等不完全燃烧产物的近源沉降;蓟县北部、宝坻西南部、武清西北部的污染物主要为北京地区的大气输入,此外由于当地工业和民用燃料以燃煤和木材燃烧为主,所以当地的煤烟型污染也有一定的贡献;三大排污河污灌区及其附近土壤中的主要污染物为工业油类;大港区的主要污染物是随风迁移来的煤燃烧的产物,而大港油田在开发储运过程中的原油泄露造成的污染贡献并不显著。静海县土壤中的主要污染物为远距离迁移而来的化石燃料的燃烧产物。 相似文献
17.
提取方法对葡萄柚精油性质与组成的影响 总被引：1，自引：0，他引：1
葡萄柚精油是柑橘精油的重要类别,具有清新、浓郁的特征果香,是一种广受欢迎的天然香精。为了研究提取方法对葡萄柚精油表观特征、物理性质及化学组成的影响,文章分别以蒸馏法和冷榨法制备葡萄柚精油,采用气质联用(GC-MS)分析其化学组成。结果表明蒸馏法的精油得率远高于冷榨法,但冷榨法所得精油的色泽和气味更接近天然葡萄柚,折光率和相对密度也更高;蒸馏法所得精油含有39种可检测化合物,其中含氧化合物18种,相对含量为14.11%,而冷榨法所得精油含37种可检测化合物,16种为氧化物,相对含量达17.18%,尤其是芳樟醇、葵醛、柠檬醛等特征香气成分的含量明显高于前者,表明冷榨法比蒸馏法更适宜制备高品质葡萄柚精油。 相似文献
18.
[目的] 探讨不同的提取方法对川芎挥发油化学成分的影响。［方法] 运用超临界流体萃取法、水蒸气蒸馏法和中性乙醇提取法3种方法提取川芎油,用GC-MS计算联用技术对其所含化学成分及其相对含量进行分离鉴定。[结果] 超临界流体萃取法、水蒸气蒸馏法和中性乙醇提取法3种方法所提挥发油有16个成分相同,各占其相对含量的79.87%、89.42%和71.32%,其中分别有10、8和5个成分是各自特有的,各占其相对含量的2.51%、3.03%和6.90%。这3种工艺均能提取挥发油主要成分内酯类化合物,其中以超临界流体CO2萃取样品所含组分最多,整个操作过程耗时短、效率高。［结论] 该研究为开发川芎药用资源和选择加工工艺提供了依据。 相似文献
19.
[目的]为了探究千层金叶片挥发性物质的种类,[方法]本文采用顶空固相微萃取(HS-SPME)-气质联用(GC-MS)技术分析、鉴定了千层金叶片的挥发性成分,研究结果和采用水蒸气蒸馏法(HD)提取的千层金叶片精油进行比较。[结果]研究结果表明,千层金叶片采用HS-SPME提取,总共检测出76种挥发性物质,占总峰面积的97.28%;采用HD提取的千层金叶片精油,总共检测出37种挥发性物质,占总峰面积的99.67%;HS-SPME提取的千层金叶片的挥发物质主要包括醚类、烃类、酯类、醇类、酚类、醛类等,其中醚类所占的相对含量最大,主要成分为甲基丁香酚,相对含量达到72.42%以上;HD法提取的千层金叶片精油中,最主要成分甲基丁香酚的相对含量达到91.48%。[结论]千层金叶片精油中含有这么高含量的甲基丁香酚,在植物保护上具有极大的潜在利用价值。 相似文献
20.
该文通过对刨花干燥过程中影响因素的研究,以期为刨花干燥工艺的优化设计和过程控制提供理论依据.研究表明,随着气流温度的升高,刨花平均干燥速率增大,单位能耗也相应增加;随着气流速度的提高,刨花平均干燥速率增大,单位能耗逐渐降低;随着刨花初含水率的升高,刨花平均干燥速率加大,单位能耗增加;随着装载量的增大,刨花平均干燥速率大幅减小,单位能耗基本不变,总能耗急剧增加;转筒的运动影响了刨花的干燥,其自转可提高平均干燥速率.实际生产中应根据产量和生产成本,选择合适的干燥条件进行生产. 相似文献