Paleobotany     

Hickey LJ 《Science (New York, N.Y.)》1981,212(4498):1021-1022

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Fission-track dating of haughton astrobleme and included biota, devon island, Canada     

Omar G  Johnson KR  Hickey LJ  Robertson PB  Dawson MR  Barnosky CW 《Science (New York, N.Y.)》1987,237(4822):1603-1605

Haughton Astrobleme is a major extraterrestrial impact structure located on Devon Island in the Canadian Arctic Archipelago, Northwest Territories. Apatite grains separated from shocked Precambrian gneiss contained in a polymict breccia from the center of the astrobleme yielded a fission-track date of 22.4 million +/- 1.4 million years before the present or early Miocene (Aquitanian). This provides a date for the impact event and an upper limit on the age of crater-filling lake sediments and a flora and vertebrate fauna occurring in them. A geologically precise date for these fossils provides an important biostratigraphic reference point for interpreting the biotic evolution of the Arctic.  相似文献   

A neuroendocrine marker in tissues of the immune system   总被引：5，自引：0，他引：5  

R H Angeletti  W F Hickey 《Science (New York, N.Y.)》1985,230(4721):89-90

Antibodies to chromogranin, a secretory protein marker for the diffuse neuroendocrine system, were used to analyze rat lymphoreticular tissues by means of immunochemistry and immunohistochemistry. Chromogranin-positive cells were present in spleen, lymph node, thymus, and fetal liver. When these organs were gently dispersed and separated on a Ficoll gradient, the chromogranin-immunoreactive cells became enriched in the dense red-cell pellets. The unexpected distribution of these neuroendocrine cells in all immunologically relevant structures suggests that they may link the nervous and immunological systems.  相似文献   

Thermally Switchable Periodicities and Diffraction from Mesoscopically Ordered Materials     

JM Weissman  HB Sunkara  AS Tse  SA Asher 《Science (New York, N.Y.)》1996,274(5289):959-960

Two switchable, mesoscopically periodic materials were created by combining crystalline colloidal array (CCA) self-assembly with the temperature-induced volume phase transition of poly(N-isopropylacrylamide) (PNIPAM). Body-centered-cubic CCAs of hydrated, swollen PNIPAM particles Bragg-diffract infrared, visible, and ultraviolet light weakly, whereas arrays of compact shrunken particles diffract efficiently. A tunable diffracting array was also created by embedding a CCA of polystyrene spheres within a PNIPAM hydrogel that swells and contracts with temperature; thus the array lattice constant varies with temperature, and the diffracted wavelength was thermally tunable across the entire visible spectrum. These materials may find applications in many areas of optics and materials science.  相似文献   

Correlation of the antinociceptive action and plasma concentration of fentanyl following intravenous administration in cats     

SA Robertson  WL Davies  PM Taylor  MJ Dixon 《Veterinary anaesthesia and analgesia》2002,29(2):94-94

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Assessing the utility of stakeholder analysis to Protected Areas management: The case of Corbett National Park, India   总被引：1，自引：0，他引：1  

Archi Rastogi  Ruchi Badola  Syed Ainul Hussain  Gordon M. Hickey 《Biological conservation》2010,143(12):2956-2964

This study tests the potential utility of Stakeholder Analysis to Protected Area management. Using Corbett National Park (CNP), India, as a case study, Stakeholder Analysis (SA) was used to identify important stakeholder groups and assess their relationships, relative power and importance. This exercise was undertaken to assist the managers of CNP with future strategy formulation and implementation. The results demonstrate SA to be a simple, yet effective, method that can help PA managers understand the social dimensions of their undertaking, without waiting for long-term policy changes. The results reveal possible stakeholder alliances, and those that may need strengthening to guarantee the welfare of CNP. Divergent opinions on the same issue were also discovered. This underlines that addressing low levels of knowledge and misplaced information may be of strategic importance in reducing conflict against a PA. This research also helps theorize previously unexplored relationships among stakeholders in India, using the framework of Stakeholder Theory. Repeating the exercise on a regular basis could help PA managers monitor stakeholder interactions and political positions over time.  相似文献   

碱性盐胁迫对燕麦矿质离子吸收与分配的影响   总被引：2，自引：0，他引：2  

萨如拉  刘景辉  刘伟  白健慧 《麦类作物学报》2014,34(2):261-266

为探讨燕麦耐碱性与矿质离子的关系,通过盆栽试验,将碱性盐Na2CO3、NaHCO3按摩尔比1∶1混合设置不同浓度(0、50和100mmol·L-1)胁迫处理,分析燕麦耐碱性品种vao-9和碱敏感性品种白燕5号根、茎、叶对Na+、K+、Ca2+、Mg2+、Fe2+、Cu2+、Zn2+的吸收及分配规律。结果表明,碱性盐胁迫下2个品种根、茎、叶中Na+含量增加,K+、Cu2+含量下降;Ca2+、Mg2+含量在根中增加,在茎、叶中下降,Fe2+、Zn2+含量在不同胁迫程度下和不同器官中变化不同。与白燕5号相比,vao-9吸收的Na+总量较低,K+、Ca2+、Cu2+总量较高,Mg2+、Fe2+、Zn2+总量变化不大。在胁迫浓度达到100mmol·L-1时,vao-9茎中截留Na+,叶片中较K+、Ca2+、Mg2+、Fe2+、Cu2+和Zn2+分配较多,而白燕5号叶片中积累Na+较多,茎中积累K+较多,根中积累Ca2+、Mg2+、Fe2+、Cu2+、Zn2+较多,从而使碱性盐胁迫下vao-9较白燕5号叶片中保持的Na+/K+、Na+/Ca2+和Na+/Mg2+低。可见,在高浓度碱性盐胁迫下vao-9茎中区域化Na+,选择吸收K+、Ca2+、Cu2+,并在叶片中分配较多的矿质离子来保持燕麦体内离子平衡,以适应盐碱胁迫。  相似文献   

豆米轮作对春玉米土壤固氮细菌群落结构及多样性的影响     

提俊阳  张玉芹  杨恒山  张瑞富  邰继承  萨如拉  韩镁琪 《中国农学通报》2023,39(2):44-50

为探明大豆-玉米轮作对土壤固氮细菌的影响，以玉米连作为对照(MMM)，以nif-H基因为指示，采用高通量测序技术，分析大豆-玉米2年轮作周期(MSM)和大豆-玉米-玉米3年轮作周期(SMM)下土壤固氮细菌群落结构及多样性。结果表明：大豆-玉米轮作下0～20、20～40 cm土层土壤有机质、全氮、碱解氮、铵态氮和硝态氮均显著增加。固氮细菌的Chao1指数和ACE指数在0～20、20～40 cm土层均为轮作高于对照，轮作下MSM显著高于SMM;Shannon指数和Simpson指数在0～20 cm土层轮作显著高于MMM;20～40 cm土层MSM显著高于MMM。在门水平上，MSM和SMM的0～20、20～40 cm土层变形菌门的相对丰度均高于MMM。在属水平上，2个轮作类型0～20 cm土层的慢生根瘤菌属、弗兰克氏菌属和纤毛菌属相对丰度显著较高；20～40 cm土层慢生根瘤菌属、伪食酸菌属、地杆菌属和固氮弧菌属相对丰度显著较高；MSM 0～20、20～40 cm土层慢生根瘤菌属、甲基孢囊菌属和固氮弧菌属较SMM均提高。方差分析表明，固氮细菌丰度指数（Chao1和ACE指数）与有机质、碱解氮...  相似文献