999 resultados para 13077-070
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了解三江源人工草地净生态系统CO_2交换(Net ecosystem CO_2 exchange, NEE)的季节变化规律和主要生物因子及环境因子对这些过程的影响将有助于认识青藏高原人工草地生态系统碳循环、生态价值、功能,以及对三江源区的生态安全的重要意义.该研究利用涡度相关技术,于2005年9月1日至2006年8月31日对位于青海腹地的垂穗披碱草(Elymus nutans)人工草地的NEE及生物和环境因子进行观测,阐明NEE及其组分的动态变化特征和影响因子.三江源区人工草地生态系统的日最大吸收量为2.38gC•m~(-2)•d~(-1),出现在7月30日.日间最大吸收率和最大排放率都出现在8月,分别为-6.82和2.95/μmol CO_2•m~(-2)•s~(-1).在生长季,白天的NEE主要受光合有效辐射(Photosynthetically active radiation, PAR)变化控制, 同时又与叶面积指数和群落多样性交互作用,共同调节光合速率和光合效率的强度.最大光合同化速率为2.46~10.39μmol CO_2•m~(-2)•s~(-1),表观初始光能利用率为0.013~0.070μmol CO_2•μmol~(-1)PAR.在碳交换日过程中,NEE并不完全随着PAR的增加而增大,当PAR超过某一值(>1200μmol•m~(-2)•s~(-1))时,NEE随PAR的增加而降低.受温度的影响,生长季的生态系统的呼吸商Q10(1.8)小于非生长季节的(2.6).生态系统呼吸主要受温度的控制,同时也受到叶面积指数的显著影响.生长季昼夜温差大并不利于生态系统的碳获取.三江源区人工草地生态系统是一个较强的碳汇,为-49.35gC•m~(-2)•a~(-1).
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于2000---2002年的鸟类繁殖期在中国科学院海北高寒草甸生态系统定位站,测定了27窝角百灵(Eremophtla alpestns)和43窝小云雀(Alauda gulgula)的巢址特征,观察了两者在繁殖期巢数的季节变化,并运用稳定性同位素技术测定了育雏食物,对两种百灵的巢址特征和食物重叠度进行了比较。结果表明两者的巢址特征存在着显著的不同:角百灵的巢开放度为92.16%,小云雀的为34.61%,前者的巢开放度显著大于后者(P<0.01);角百灵距巢100 em范围内遮蔽物的数量为0.070.26,小云雀的为2.571.19,前者显著少于后者(P<0.01);角百灵巢址植被的高度和盖度也显著小于小云雀的(P<0.01)。角百灵和小云雀均以小型昆虫育雏,育雏食物的资源重叠程度很高,为O.8957;而且两者的繁殖季节和繁殖强度也是相互重叠的。这两种百灵鸟类在巢址的选择上存在着一种代价和利益的权衡关系,巢址选择是捕食压和热条件共同作用的结果。二者共存的机制是巢址上的分化。
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Located in the Paleozoic uplift along the southern margin of Tu-Ha basin in eastern Xinjiang, the newly discovered Hongshan Cu-Au deposit occurs in the superimposed Mesozoic volcanic basin upon the north section of later Paleozoic Dananhu-Tousuquan accretionary arc. Kalatage Cu-Au orebelt is controlled by NWW-trend faults, and includes Hongshan and Meiling Cu-Au deposits. The host rocks of Hongshan ore district are mainly rhyolitic-dacitic ignimbrites, whereas Cu-Au mineralization is closely related to quartz porphyry, rhyolitic porphyry and granitic porphyry. Mineralization styles are dominantly veinlet-disseminated and veinlet, occasionally stockwork. The mineral association is chalcopyrite, pyrite, bornite, chalcocite and sphalerite. The hydrothermal alteration consists of silicfication, sericitization, alunitization, pyrophylitization, illitization, hydromuscovitization, and chloritization. Hongshan Cu-Au deposit, on the edge of the desert, is one of the driest areas in eastrn Tianshan. Moreover, the highest temperature has been up to 60℃, and the average rainfall receives only 34.1mm/y. The light rainfall and rapid evaporation in the vicinity of this deposit have allowed the formation of a great variety of water-soluble sulfates. Oxidization zone of this deposit lies on the upper part of primary sulfide orebodies appearing with a depth of 50-60m, which is dominant in sulfate minerals. 1. Based on the field observation, the volcanic and sub-volcanic rock composition, hydrothermal alteration, ore structure and mineralization characteristics, this paper proposed that the Hongshan Cu-Au deposit belongs to a transitional type from high-sulfide epithermal to porphyry Cu-Au deposit, which corresponds with the typical HS-epithermal deposit such as Zijinshan Au-Cu deposit in Fujian Province, SE-China. 2. The Hongshan copper-gold deposit was controlled by the tectonic, stratum, magma activity and volcanic apparatus, whereas Au mineralization is closely related to quartz porphyry, rhyolitic porphyry and fine grained pyritization in hydrothermal activity, and Cu mineralization is closely related to quartz porphyry and hydrothermal explosive breccia. 3. Oxidation zone of Hongshan Cu-Au deposit lies on the upper part of primary sulfide orebodies deposit. 23 sulfate minerals were identified in this work. The results of samples XRD and chemical analysis were furthermore confirmed through thermal, infrared spectrum and mössbauer spectrum analysis. Among those, nine minerals as Ferricopiapite, Cuprocopiapite, Rhomboclase, Parabutlerite, Krausite, Yavapaiite, Metasideronatrite Kroehnkite and Paracoquimbite were founded in China for the first time. And Paracoquimbite was secondly reported in the world (first case reported at 1938 in Chile). 4. EPMA analysis shows that Al impurity in crystal lattice is important to polytype formation of paracoquimbite and coquimbite besides stack fault. 5. Compared with Meiling Cu-Au deposit in the same Kalatage ore belt from the characteristics of δ34S of barite, lithofacies, hydrothermal alteration and homogeneous temperature, Hongshan Cu-Au deposit belongs to the same metallogenic system of HS-epithermal type as Meiling Cu-Au deposit. But Hongshan Cu-Au deposit has less extensive alteration and shallower denudation. 6. Sulfur isotope analyses show that δ34S values of pyrites vary in the range of +1.86‰~+5.69‰, with an average of 3.70‰, mostly in the range of +1.86‰~+3.20‰, and δ34Scp<δ34Spy. Therefore ore-forming fluid of porphyry comes from mantle and was contaminated by the earth’s crust. Sulfur isotope has reached balance in ore-forming process. 7. Sulfur isotope analyses show that δ34S values of sulfates vary in the range of +2.15‰~+6.73‰, with an average of +3.74‰, mostly equals as δ34S values of primary sulfides in Hongshan Cu-Au deposit. So supergene sulfates inherit sulfur of primary sulfide. δ34S values are mostly same in different sulfates. As well as pyrite and chalcopyrite, volcanic hot spring and associated native sulfur underground also provide water medium and sulfur during the formation process of sulfate. 8. According to the EPMA of sample chalcopyrite and pyrite in Hongshan Cu-Au, the value of Cu/Ni is 0.98-34.72, mostly close to the value of 5, which shows that Hongshan deposit is a typical volcanogenic magmaic hypothermal deposit. Au and Ag, Zn, Te and Bi are positive correlation, Cu and Hg, Se, Sb are positive correlation, indicates Au and Cu don’t locate in the factor of mineralization of same mineralization groups. The reasons of gold concentration in the oxidation zone are: 1). Change of redox potential (Eh) makes gold to deposit from the liquid of mineralization zone; 2). PH is one of the most factors of gold’s deposition; 3). Soluble complex and colloid of gold can be adsorbed easily. 9. The biotite and hornblende K-Ar isotopic ages from the wall rock-quartz diorite, biotite granite and monzonite granite are 231.99±3.45Ma, 237.97±2.36Ma and 296.53±6.69Ma respectively. The ore-bearing rhyolitic breccia lava contains breccia of the biotite granite which indicates the volcanism and related Cu-Au mineralization occurred later than the granite, possibly in Mesozoic. K-Ar ages of granitoids in Sanya, Baishiquan and Hongliugou area and Molybdenite Re-Os age of Baishan Mo deposit all are in Triassic. Besides late Paleozoic magmatism, igneous magmatic event of Mesozoic was widespread in eastern Tianshan. 10. The K-Ar age dating indicates that the K-Ar age of Voltaite occurred below surface 1m is 56.02±3.98Ma, K-Ar age of Ferricopiapite occurred below surface 1.5m is 8.62±1.12Ma, K-Ar age of Yavapaiite occurred below surface 14 m is 4.07±0.39Ma, and K-Ar age of Voltaite occurred below surface 10 m is 14.73±1.73Ma. So the age interval of oxidation zone of Hongshan copper-golden bed is between 60 -3.38Ma. Oxidization occurred at Caenozoic era (from 65Ma), which can be identified through comparing with different deposits oxidation zone in other countries. The coupling between global tectonic event and climatic change event which occur from Caenozoic era has some effect on epigeosphere system, which can act on the surface of bed oxidation zone similarly. It induces that the age mentioned above coincide with collision of India-Asia and multistage uplifting of Qinhai-Tibet Plateau happened subsequently. Bed oxidation zone is the effect and record of collision and uplifting of Tibet Plateau. The strong chemical weathering of surface accumulation to which was leaded by PETM event occurred Paleocene and Eocene is the reason of Voltaite sharply rises. On the contrary, Ferricopiapite formed due to the global cold weather. The predecessor did much research through biota, isotopes, susceptibility, but this paper try to use different sulfate mineral instead of climatic change. So the research of sulfate minerals not only indicates a great deal of oxidized zone feature, but also the intergrowth of sulfate minerals may be used to trace paleoenviroment and paleoclimate of oxidation zone. 11. Analysis of the information of alteration and mineralization features of four bore cores, induced activity polarization well logging and Eh-4 geophysical section, deep mineralization anomaly objects of Hongshan ore districts shows low resistance, middle and high polarization, measurements of Eh-4 consecutive conductance section show the existing of concealed porphyry ore body deeper than 450m, on the top of and around rock body there are low resistance body ranged from 100-300Ω•m, this area may be the ore-bearing part. In a word, Hongshan Cu-Au deposit deposit is a combine of upper HS-style epithermal Au deposit and deeper porphyry mineralization system. It has great potential to find large HS-style epithermal-porphyry Au-Cu deposits. This paper consists of seven chapters and twenty seven sections. The geological character of deposit is basic condition in this work. Constitute of oxidation zone, research of sulfate mineral, relation between oxidation and primary zone, K-Ar ages of potassic sulfate are key parts of thesis. Genesis of ore deposit is the further expansion of this research. Analysis of ore-controlling factors is the penetration above basic. Analysis of potential is application of exploration.
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沉积物柱芯分别采自滇西地区的洱海和黔中地区的红枫(及百花)湖,散落核素^7Be和^137Cs在沉积物中的蓄积特征对比分析表明,^7Be在洱海及红枫湖沉积物中的累计值分别为(237±73)Bq/m^2和(783±44)Bq/m^2;按校正到沉降年代的数值,1986年以前^137Cs的累计值分别为(519±26)Bq/m^2及(3704±56)Bq/m^2。由模式计算获知,(1)^7Be和^137Cs在红枫湖沉积物中的蓄积以侵蚀影响为主;在洱海的蓄积受直接散落控制。(2)在洱海和红枫湖地区^7Be大气散落累计值分别为(0.07±0.02)Bq/cm^2及(0.08±0.01)Bq/cm^2;1986年以前^137Cs大气散落累计值分别为(0.11±0.01)Bq/cm^2及(0.37±0.01)Bq/cm^2,显示出滇西与黔中地区之间^137Cs散落的地区差异。这一现象可能反映出青藏高原对滇西地区存在着全球性大气扩散污染物散落的屏蔽效应。
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基于冷原子荧光测定方法对红枫湖沉积物及孔隙水中总汞、甲基汞浓度的时空分布特征及控制因素进行了分析.红枫湖沉积物总汞含量为(0.392±0.070)μg/g,高于世界其它背景区汞浓度,也高于处于同一流域的乌江渡水库和东风水库,表明红枫湖受到了一定程度的汞污染.2个采样点总汞无明显的季节变化,但其剖面分布都有在上层富集的趋势.沉积物甲基汞浓度在春季最高,其余季节则没有明显差异,甲基汞峰值出现在表层0-8 cm以内,与红枫湖沉积物中硫酸盐还原菌活动区域一致.沉积物甲基汞浓度的季节变化和剖面最大峰值分布,主要受氧化还原带的季节性迁移所控制.红枫湖孔隙水中总汞的浓度及在固/液之间的分配系数主要和随季节变化的温度或氧化还原条件有关,与沉积物固相中总汞浓度和分布相关性不大,而孔隙水中甲基汞浓度则和沉积物甲基汞浓度存在着极显著的相关性(r=0.70,p〈0.001).沉积物和孔隙水甲基汞浓度除受到固/液分配系数影响外,主要还受到甲基汞产生过程控制.
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上世纪八十年代,科学家们发现在北美和北欧一些远离汞污染源的湖泊中,某些鱼汞含量远远超过了世界卫生组织建议的食用水产品汞含量标准,这一现象引起了人们对水环境系统中汞的生物地球化学循环的极大关注。因此本论文对贵州红枫湖和加拿大安大略省3个小湖中汞的形态与分布特征进行了详细的研究,并对红枫湖整个汞的生物地球化学循环做了较为完整深入的探讨。本论文主要包括以下4方面的研究内容:(1)沉积物甲基汞分析方法的建立;(2)红枫湖水体、沉积物、鱼体中各种汞形态的含量、分布特征以及水体富营养化对其影响的研究;(3)红枫湖汞形态转化、输入输出通量及其质量平衡的估算;(4)红枫湖的对比研究点—加拿大安大略省的Mary、St. George和Philips湖中不同形态汞分布特征的初步研究。通过本论文的研究,得出以下主要结论: 1. 建立了硝酸和硫酸铜溶液浸提,CH2Cl2萃取并结合水相乙基化和GC-CVAFS测定沉积物及土壤中甲基汞的方法。该方法平均回收率为 97.8%,相对标准偏差≤10.2%,方法检出限为0.6pg/g,具有所需试剂少、不用连续萃取、简捷易行、回收率高以及精密度好等特点。 2. 2004年红枫湖湖水总汞浓度在2.5-14 ng/L之间,平均值为6.9 ng/L;溶解态汞浓度范围在1.2-8.0 ng/L之间,平均为3.9 ng/L。不管是红枫湖水体汞浓度的空间分布,还是季节变化都严重受到人为污染源的干扰。湖水汞在颗粒态和溶解态之间的分配,主要受内源有机质以及氧化还原条件的影响。2004年春季后五由于水华现象大量繁殖的藻类,吸附了大量的汞,从而改变了汞在水库中的分配和迁移。这些藻类的生长对水体中溶解气态汞浓度分布也有显著的影响。湖水中活性汞分布特征主要受Hg2+的光致还原过程、Hg2+的甲基化过程以及人为源的输入等过程控制。 3. 红枫湖夏季下层滞水带中,甲基汞含量显著升高,特别是在后五缺氧层,最高值达0.92ng/L。夏季总甲基汞和溶解态甲基汞在水体剖面上的分布表明:在富营养化较严重的后五,水体中升高的甲基汞主要来自水体中汞的甲基化过程;而在富营养化特征不明显的大坝,水体中升高的甲基汞主要来自沉积物甲基汞的释放。红枫湖水体中各种汞形态的分布特征表明,富营养化对汞的迁移转化影响显著,尤其是汞的甲基化过程。水体富营养化为汞的甲基化提供了有利条件,给水生生态环境及人体健康带来了潜在的威胁。 4. 红枫湖沉积物总汞浓度为0.392 ± 0.070 μg/g,高于世界其它背景区汞浓度,也高于处于同一流域的乌江渡水库和东风水库,表明红枫湖受到了一定程度的汞污染。两个采样点总汞无明显的季节变化,但其剖面分布都有在上层富集的趋势。沉积物甲基汞浓度的季节变化和剖面最大峰值分布,主要受氧化还原带的季节性迁移所控制。沉积物甲基汞浓度在春季最高,其余季节则没有明显差异,甲基汞峰值出现在表层0~8cm以内,与红枫湖沉积物中硫酸盐还原菌活动区域一致。 5. 红枫湖总汞在孔隙水中的浓度及在固/液之间的分配系数主要和温度有关,与沉积物中总汞相关性不大,而孔隙水中甲基汞浓度则和沉积物甲基汞浓度存在着极显著的相关性(r=0.70, p<0.001)。沉积物和孔隙水甲基汞浓度除受到固/液分配系数影响外,主要还受到甲基汞产生过程控制。 6. 由于本次研究所采集的鱼类多为红枫湖人工饲养鱼,生长速度快,食物链短,故总汞含量(32ng/g)和甲基汞含量(12ng/g)都远远低于国家食用标准。汞含量在不同鱼种中的分布趋势为:肉食性鱼类>杂食性鱼类>草食性鱼类,这表明鱼体中汞含量主要和鱼的摄食习惯有关。 7. 红枫湖总汞质量平衡模型的估算结果表明,红枫湖水体中汞的总源为30066 g.a-1,总汇为31010g.a-1。水体中总汞最大的源来自于河流输入(82%),而最大的汇是水体颗粒态汞的沉降(78%)。甲基汞质量平衡模型的估算结果表明河流输出是水体甲基汞一个重要的汇,占总汇的45%, 比河流输入占总源的比例高30%,表明水库是下游水体甲基汞的源。 8. 红枫湖汞在水-沉积物界面的迁移通量表明,沉积物是水体中汞和甲基汞一个巨大的汇,而沉积物对上覆水体总汞和甲基汞的贡献却很有限。红枫湖汞在水-气界面的迁移通量表明,大气汞沉降特别是干沉降是红枫湖水体总汞一个重要的污染源,其对红枫湖汞的贡献远大于水体向大气释放的汞,大气沉降每年向红枫湖净贡献汞量为3364 g.a-1。 9. 在对比研究的湖泊中,水体中甲基汞的剖面分布表明,斜温层颗粒态甲基汞的沉降、沉积物甲基汞的释放以及水体汞的甲基化过程都是下层水体高甲基汞的重要来源。在这些湖泊中近代汞的沉积通量为22.1 μg m-2 a-1,远低于红枫湖中汞的沉积通量(714 μg m-2 a-1)。与红枫湖以及一些典型的沉积物甲基汞的垂直剖面分布相比,这些小湖中甲基汞的产生不仅发生在沉积物表层,在较深的沉积物中可能也有汞的甲基化过程,而且这个过程和有机质的含量密切相关。
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Social networks have increasingly become a showcase where the media can be promoted. Like many other media, radio stations have made use of social networks to promote themselves in a better way and, sometimes, to keep more feedback with their listeners. But not all programs make the same use and not all of them have managed to reach in the same way his followers. This article discusses the consolidation in the social networks of the major radio sports programs in Spain. Through a comparative analysis between 2010 and 2015, throughout the text, the authors have tried to observe the evolution of the programs and, at the same time, to establish comparisons between the followers that these programs have on social networks and the number of listeners as EGM.
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Reduced arterial compliance precedes changes in blood pressure, which may be mediated through alterations in vessel wall matrix composition. We investigated the effect of the collagen type I-1 gene (COL1A1) +2046G>T polymorphism on arterial compliance in healthy individuals. We recruited 489 subjects (251 men and 238 women; mean age, 22.6±1.6 years). COL1A1 genotypes were determined using polymerase chain reaction and digestion by restriction enzyme Bal1. Arterial pulse wave velocities were measured in 3 segments, aortoiliac (PWVA), aortoradial (PWVB), and aorto-dorsalis-pedis (PWVF), as an index of compliance using a noninvasive optical method. Data were available for 455 subjects. The sample was in Hardy-Weinberg equilibrium with genotype distributions and allele frequencies that were not significantly different from those reported previously. The T allele frequency was 0.22 (95% confidence interval, 0.19 to 0.24). Two hundred eighty-three (62.2%) subjects were genotype GG, 148 (35.5%) subjects were genotype GT, and 24 (5.3%) subjects were genotype TT. A comparison of GG homozygotes with GT and TT individuals demonstrated a statistically significant association with arterial compliance: PWVF 4.92±0.03 versus 5.06±0.05 m/s (ANOVA, P=0.009), PWVB 4.20±0.03 versus 4.32±0.04 m/s (ANOVA, P=0.036), and PWVA 3.07±0.03 versus 3.15±0.03 m/s (ANOVA, P=0.045). The effects of genotype were independent of age, gender, smoking, mean arterial pressure, body mass index, family history of hypertension, and activity scores. We report an association between the COL1A1 gene polymorphism and arterial compliance. Alterations in arterial collagen type 1A deposition may play a role in the regulation of arterial compliance
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Summary
Decolonisation may reduce the risk of meticillin-resistant Staphylococcus aureus (MRSA) infection in individual carriers and prevent transmission to other patients. The aims of this prospective cohort study were to determine the long-term efficacy of a standardised decolonisation regimen and to identify factors associated with failure. Patients colonised with MRSA underwent decolonisation, which was considered to be successful if there was no growth in three consecutive sets of site-specific screening swabs obtained weekly post treatment. If patients were successfully decolonised, follow-up cultures were performed 6 and 12 months later. Of 137 patients enrolled, 79 (58%) were successfully decolonised. Of these 79, 53 (67%) and 44 (56%) remained decolonised at 6 and 12 months respectively. Therefore only 44/137 (32%) patients who completed decolonisation were MRSA negative 12 months later. Outcome was not associated with a particular strain of MRSA. Successful decolonisation was less likely in patients colonised with a mupirocin-resistant isolate (adjusted odds ratio: 0.08; 95% confidence interval: 0.02–0.30), in patients with throat colonisation (0.22; 0.07–0.68) and in patients aged >80 years (0.30; 0.10–0.93) compared with those aged 60–80 years. These findings suggest that although initially successful in some cases, the protocol used did not result in long-term clearance of MRSA carriage for most patients.
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Background: The purpose of this study is to describe the nature of cases undergoing temporal artery biopsy (TAB) for suspected giant cell arteritis (GCA). Methods: A retrospective review of case notes was undertaken for all patients on whom ophthalmologists had performed TAB in 2 teaching hospitals between 1995 and 2001. Presenting symptoms, referring specialty, TAB result, treatment, and discharge diagnosis were recorded. Results: Ophthalmologists performed TAB on 110 patients for suspected GCA. A variety of specialties referred patients to ophthalmology for TAB; presenting symptoms varied with referral source. Of the 110 TABs, 21 (19%) were reported as positive for GCA, 84 (76%) were negative, and 5 (4.5%) were reported as inadequate. The symptoms most commonly associated with a positive TAB were visual disturbance (15/21) and headache (15/21).The odds ratios for having a positive TAB result rather than a negative result were 1.0 for the presence of headache, 4.1 for visual disturbance, and 6.7 for jaw claudication. Interpretation: Physicians were faced with a different population of GCA suspects than ophthalmologists. While physicians should be alert to the significance of visual symptoms or jaw claudication, ophthalmologists should be ready to facilitate prompt TABs when appropriate. TAB should be performed promptly and an adequate length of artery taken for biopsy. An argument can be made that TAB is not needed in cases of suspected GCA. However, a positive result provides firm justification for the use of steroids. We feel that TAB has a useful role and we make reference to methods to maximize its usefulness.