9,610 research outputs found

    Production of polyploids from cultured shoot tips of Eucalyptus globulus Labill by treatment with colchicine

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    Polyploids from cultured shoot tips of Eucalyptus globulus were produced by treatment with colchicine. Results showed that the combination of 0.5% colchicine and treating multiple shoot clumps for 4 days was the most appropriate conditions for E. globulus polyploidy induction and the effect of the use of multiple shoot clumps for colchicine polyploidy-induced was better than single buds. By comparing the polyploidy plants with normal diploid ones in morphology, leaves of polyploid plants were thicker, larger, and darker green. The chromosome number of polyploidy plants that had been identified in morphology was 2n = 4x = 44, while that of diploids was 2n = 2x = 22

    阿爾泰哈巴河群的沉積時代及其構造背景

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    Habahe Group mainly consists of elastic sediments, which widely distribute in the Chinese Altai and can provide important constraints on the tectonic evolution of the Central Asian Orogenic Belt (CAOB). However, there are different opinions about its deposition time and tectonic background. Previous studies suggested that the Habahe Group formed in Sinian to Mid-Ordovician or Mid- to Late Ordovician in a passive continental margin. On the other hand, recent geological investigations reveal a long lasting subduction-related setting in the Chinese Altai at least since Cambrian. The current geochronological study for detrital zircons from the Habahe Group reveals that the detrital zircons of individual samples, irrespective of their lithological and metamorphic differences, all show similar age patterns, with the early Paleozoic ( 206Pb/ 238U age = 463 ± 542Ma) grains predominating. The youngest detrital zircons from different samples display similar ages (ca. 470Ma), which may reflect the maximum deposition time of the Habahe Group. Dating of growth rim of detrital zircons from migmatite yielded a Mid-Devonian age (384 ± 6Ma), which was coeval with intrusion of Early to Mid-Devonian granitic plutons in the area and clearly indicates the minimum deposition time of the Hababe Group. Therefore, the deposition time of the Habahe Group can be constrained to be Mid-Ordovician to Early Devonian. Zircon U Pb dating results indicate that the detrital zircons of the Habahe Group are dominated by early Paleozoic grains, with small proportion formed in Precambrian. The early Paleozoic detrital zircons are mostly magmatic in origin, and their less rounded shapes indicate a limited transportation. The age and morphological characteristics of the detrital zircons are consistent with those of detrital zircons in active tectonic settings and indicate that the Chinese Altai was under an active continental margin environment during the Early Paleozoic. 北疆阿爾泰造山帶的哈巴河群變質碎屑巖分布廣泛,其沉積時代和構造環境對于認識中亞造山帶的演化歷史有重要意義。早期研究認為哈巴河群沉積于震旦紀—中奧陶世時期,形成于被動大陸邊緣構造環境。而最近有學者根據中亞造山帶的地質演化背景提出,阿爾泰形成于活動陸緣構造環境。對哈巴河群中碎屑鋯石的年代學研究表明,不同巖性或變質程度不同的樣品碎屑鋯石主要類群具有相似的年齡分布特征,其206Pb/238U 年齡主要介于463~542Ma 之間。在這些樣品中, 最年輕的碎屑鋯石年齡均集中于470Ma 左右,代表了碎屑沉積的時代下限。而哈巴河群混合巖樣品中碎屑鋯石增生邊形成于中泥盆世晚期(384±6Ma),與侵入該群的早古生代花崗巖的年齡十分接近,大致反映了哈巴河群碎屑巖沉積時代的上限,因此哈巴河群的沉積時代應在早泥盆世—中奧陶世之間。鋯石的形態和內部結構特征顯示哈巴河群的年輕碎屑鋯石類群(463~542Ma)主要為巖漿鋯石,其磨圓度較差,而且在比例上遠高于前寒武紀碎屑鋯石。上述特點與活動大陸邊緣碎屑鋯石類群分布特征完全一致,反映阿爾泰在中奧陶世至早泥盆世可能處于活動大陸邊緣構造環境。postprin

    Impaired flush response to niacin skin patch among schizophrenia patients and their nonpsychotic relatives: The effect of genetic loading

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    We previously reported familial aggregation in flush response to niacin skin patch among schizophrenia patients and their nonpsychotic relatives. However, little is known about whether this abnormal skin response is associated with genetic loading for schizophrenia. This study compared the niacin flush response in subjects from families with only one member affected with schizophrenia (simplex families) with those from families having a sib-pair with schizophrenia (multiplex families). Subjects were patients with schizophrenia and their nonpsychotic first-degree relatives from simplex families (176 probands, 260 parents, and 80 siblings) and multiplex families (311 probands, 180 parents, and 52 siblings) as well as 94 healthy controls. Niacin patches of 3 concentrations (0.001M, 0.01M, and 0.1M) were applied to forearm skin, and the flush response was rated at 5, 10, and 15 minutes, respectively, with a 4-point scale. More attenuated flush response to topical niacin was shown in schizophrenia probands and their relatives from multiplex families than in their counterparts from simplex families, and the differentiation was better revealed using 0.1M concentration of niacin than 0.01M or 0.001M. For the highest concentration of 0.1M and the longest time lag of 15 minutes, a subgroup of probands (23%), parents (27%), and siblings (19%) still exhibited nonflush response. Flush response to niacin skin patch is more impaired in schizophrenia patients and their relatives from families with higher genetic loading for schizophrenia, and this finding has implications for future genetic dissection of schizophrenia. © 2008 The Authors.published_or_final_versio

    Medial Prefrontal Cortex: Adding Value to Imagined Scenarios

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    The medial prefrontal cortex (mPFC) is consistently implicated in the network supporting autobiographical memory. Whereas more posterior regions in this network have been related to specific processes, such as the generation of visuospatial imagery or the association of items and contexts, the functional contribution of the mPFC remains unclear. However, the involvement of mPFC in estimation of value during decision-making suggests that it might play a similar role in memory. We investigated whether mPFC activity reflects the subjective value of elements in imagined scenarios. Participants in an MRI scanner imagined scenarios comprising a spatial context, a physiological state of need (e.g., thirst), and two items that could be congruent (e.g., drink) or incongruent (e.g., food) with the state of need. Memory for the scenarios was tested outside the scanner. Our manipulation of subjective value by imagined need was verified by increased subjective ratings of value for congruent items and improved subsequent memory for them. Consistent with our hypothesis, fMRI signal in mPFC reflected the modulation of an item's subjective value by the imagined physiological state, suggesting the mPFC selectively tracked subjective value within our imagination paradigm. Further analyses showed uncorrected effects in non-mPFC regions, including increased activity in the insula when imagining states of need, the caudate nucleus when imagining congruent items, and the anterior hippocampus/amygdala when imagining subsequently remembered items. We therefore provide evidence that the mPFC plays a role in constructing the subjective value of the components of imagined scenarios and thus potentially in reconstructing the value of components of autobiographical recollection

    PubMed related articles: a probabilistic topic-based model for content similarity

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    <p>Abstract</p> <p>Background</p> <p>We present a probabilistic topic-based model for content similarity called <it>pmra </it>that underlies the related article search feature in PubMed. Whether or not a document is about a particular topic is computed from term frequencies, modeled as Poisson distributions. Unlike previous probabilistic retrieval models, we do not attempt to estimate relevance–but rather our focus is "relatedness", the probability that a user would want to examine a particular document given known interest in another. We also describe a novel technique for estimating parameters that does not require human relevance judgments; instead, the process is based on the existence of MeSH <sup>® </sup>in MEDLINE <sup>®</sup>.</p> <p>Results</p> <p>The <it>pmra </it>retrieval model was compared against <it>bm25</it>, a competitive probabilistic model that shares theoretical similarities. Experiments using the test collection from the TREC 2005 genomics track shows a small but statistically significant improvement of <it>pmra </it>over <it>bm25 </it>in terms of precision.</p> <p>Conclusion</p> <p>Our experiments suggest that the <it>pmra </it>model provides an effective ranking algorithm for related article search.</p

    Unique Carboniferous-Permian tectonic-metallogenic framework of Northern Xinjiang (NW China): Constraints for the tectonics of the southern Paleoasian Domain

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    The late Paleozoic tectonic-metallogenic framework of North Xinjiang of the southern Paleoasian Domain was characterized by a serious of Carboniferous-Permian events, including: (1) late Carboniferous-Permian Chinese Altay island arc and its metamorphism, granulite in the Chinese Altay, radiolarian chert and high-pressure/ultra-high-pressure metamorphism; (2) late Carboniferous-early Permian adakites, Alaskan-type mafic-ultramafic complexes, and calc-alkaline magmatism, together with porphyry copper deposits, which occurred in the North Xinjiang; and (3) late Carboniferous ophiolite and island arc volcanic rocks located in the Tian Shan. Combined with the facts that there was no typical foreland basin, no typical collisional-type granitoid, and there were large amount of strike-slip faulting, it is suggested that in the Carboniferous-early Permian North Xinjiang was characterized by the coexistence of compression-extension-strike-slip structures with active magmatism and metallogeny. These phenomena all indicate that there were active margins during the late Carboniferous-early Permian, leading to the notion that the complicated accretionary orogeny along the southern Paleoasian Domain may have lasted to the latest Carboniferous-Permian.新疆北部晚古生代独特的构造一成矿作用以发育大量石炭纪一二叠纪构造一成矿事件为特征, 其中包括: (l) 发育于晚石炭世一二叠世的阿尔泰岛弧及其变质事件、阿尔泰麻粒岩与基性杂岩、西南天山放射虫硅质岩和高压一超高压一低压麻拉岩相变质事件; (2 )北疆发育的石炭纪(一二叠世)埃达克岩一高镁安山岩一富N d 玄武质岩组合、阿拉斯加型基性一超基性杂岩和大量的与俯冲相关的钙碱性岩浆活动与斑岩型铜矿床成矿作用; (3) 天山晚石炭世晚期蛇绿岩与岛弧火山岩等。结合北疆地区相关的前陆盆地发育不明显、碰撞型花岗岩欠发育与大量发育平行造山带大型走滑构造等现象, 可以认为新疆北部在石炭纪一二叠纪挤压一伸展一走滑并存, 岩浆活动与成矿作用活跃。这些新进展表明新疆北部在晚石炭世一二叠纪可能仍存在活动陆缘, 因此, 古亚洲洋构造域南部复杂增生造山作用最后延至晚石炭世晚期一二叠纪。published_or_final_versio

    PageRank without hyperlinks: Reranking with PubMed related article networks for biomedical text retrieval

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    Graph analysis algorithms such as PageRank and HITS have been successful in Web environments because they are able to extract important inter-document relationships from manually-created hyperlinks. We consider the application of these algorithms to related document networks comprised of automatically-generated content-similarity links. Specifically, this work tackles the problem of document retrieval in the biomedical domain, in the context of the PubMed search engine. A series of reranking experiments demonstrate that incorporating evidence extracted from link structure yields significant improvements in terms of standard ranked retrieval metrics. These results extend the applicability of link analysis algorithms to different environments
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