3,006 research outputs found

    The equatorial Pacific High-Productivity Belt: Elements for a Synthesis of Deep Sea Drilling Project Leg 85 Resultspaleoceanography

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    Leg 85 of the Deep Sea Drilling Project operated in the eastern central Pacific in the region of the equatorial highproductivity belt. We recovered uppermost Eocene to Quaternary reference sections amenable to fine-scale stratigraphic and paleoceanographic research, using primarily the hydraulic piston corer. Four sites (572 to 575) were drilled along an east-west (about 114 to 133°W) and north-south (about 0.5 to 6°N) transect across the equatorial belt. At Site 572 an apparently complete lower middle Miocene to Quaternary sequence was recovered: the sediment sections are dominantly siliceous-calcareous oozes and chalks, and sediment accumulation rates were high (30 to 60 m/ m.y.). Sediments at Sites 573 to 575 are similar and dominated by siliceous and calcareous oozes and chalks. Sediment accumulation rates at Site 573 were generally between 10 and 35 m/m.y. The upper Eocene to Quaternary sequence is punctuated by seven hiatuses. At Site 574 a nearly complete upper Eocene to Quaternary sequence was retrieved, including a continuous Eocene to Oligocene transition. At Site 575 a lower Miocene to Quaternary section was cored. The lower to middle Miocene section is characterized by high, constant carbonate contents and sediment accumulation rates of about 20 m/m.y.; the top of the recovered section contains two hiatuses and has accumulated at rates of less than 10 m/m.y. Except for thin, basal metalliferous layers, compositional changes in Leg 85 sediments result from shifts in the relative abundances of the biogenic siliceous or calcareous components. Leg 85 sites subsided and migrated at about 0.3 cm/yr., from about 3000 m in the eastern Pacific, south of the equator, to deeper (4000 to 4600 m), more western locations at or north of the equator. The sedimentary sequences recorded regional changes in productivity (biogenic sedimentation), dissolution, and erosion associated with the equatorial belt, as well as global paleoceanographic events. The most striking regional trend is an east-west decreasing gradient in deposition of biogenic silica, prevailing from middle Miocene to Recent, which mirrors present-day surface-water productivity. A less pronounced middle Miocene to Recent latitudinal trend in deposition appears to be the result of enhanced carbonate solution to the north. The effects of deposition in the equatorial high-productivity belt have not changed since the early Miocene. Below the middle/upper Miocene boundary, the sediments have a relatively constant high carbonate content, whereas above, carbonate percentages are highly variable. The changeover level is generally marked by a hiatus and significant changes in physical, chemical, and magnetic properties of the sediments. Results of Leg 85 contributed to advances in the four elements needed for an eventual paleoceanographic synthesis: (1) a high-resolution, multidisciplinary, and integrated datum-plane scheme and time scale, with an overall resolution of 0.13 to 0.38 m.y., was established; (2) a system of correctable acoustic reflectors was delineated over vast distances, and these reflectors were calibrated against age and physical and chemical properties at Sites 574; (3) a fine-scale geochemical (stable isotope and CaCO3) and micropaleontological climatic reconstruction was developed (discontinuously) from Oligocene to Pleistocene; and (4) broadly correctable hiatuses (NH, PH), defined by previous work, were recognized at Sites 573 to 575. The interval from 8 to 9 Ma serves to outline how integration of the foregoing elements could lead to a future synthesis. In the central basin of the equatorial Pacific, the interval from 8 to 9 Ma is marked by a hiatus (NH5) in siliceous clays. A correlative hiatus occurs in carbonate oozes of the equatorial region and in the northeastern Pacific rim, and may be correlated with the Purple equatorial Pacific reflector. The interval is characterized globally by a regression, by strong carbonate dissolution, and by isotopic and micropaleontological evidence of marked cooling. Further study of these paleoceanographic phenomena in a variety of depositional environments will lead to an understanding of their relationships and functioning

    In Peer Matters, Teachers Matter: Peer Group Influences on Students\u27 Engagement Depend on Teacher Involvement

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    This study focused on the joint effects of teachers and peer groups as predictors of change in students’ engagement during the first year of middle school, when the importance of peer relationships normatively increases and the quality of teacher–student relationships typically declines. To explore cumulative and contextualized joint effects, the study utilized 3 sources of information about an entire cohort of 366 sixth graders in a small town: Peer groups were identified using sociocognitive mapping; students reported on teacher involvement; and teachers reported on each student’s engagement. Consistent with models of cumulative effects, peer group engagement and teacher involvement each uniquely predicted changes in students’ engagement. Consistent with contextualized models suggesting differential susceptibility, peer group engagement was a more pronounced predictor of changes in engagement for students who experienced relatively low involvement from teachers. These peer effects were positive or negative depending on the engagement versus disaffection of each student’s peer group. Person-centered analyses also revealed cumulative and contextualized effects. Most engaged were students who experienced support from both social partners; steepest engagement declines were found when students affiliated with disaffected peers and experienced teachers as relatively uninvolved. High teacher involvement partially protected students from the motivational costs of affiliating with disaffected peers, and belonging to engaged peer groups partially buffered students’ engagement from the effects of low teacher involvement. These findings suggest that, although peer groups and teachers are each important individually, a complete understanding of their contributions to students’ engagement requires the examination of their joint effects. (PsycINFO Database Record (c) 2017 APA, all rights reserved

    Targeted disruption of py235ebp-1: Invasion of erythrocytes by Plasmodium yoelii using an alternative Py235 erythrocyte binding protein

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    Plasmodium yoelii YM asexual blood stage parasites express multiple members of the py235 gene family, part of the super-family of genes including those coding for Plasmodium vivax reticulocyte binding proteins and Plasmodium falciparum RH proteins. We previously identified a Py235 erythrocyte binding protein (Py235EBP-1, encoded by the PY01365 gene) that is recognized by protective mAb 25.77. Proteins recognized by a second protective mAb 25.37 have been identified by mass spectrometry and are encoded by two genes, PY01185 and PY05995/PY03534. We deleted the PY01365 gene and examined the phenotype. The expression of the members of the py235 family in both the WT and gene deletion parasites was measured by quantitative RT-PCR and RNA-Seq. py235ebp-1 expression was undetectable in the knockout parasite, but transcription of other members of the family was essentially unaffected. The knockout parasites continued to react with mAb 25.77; and the 25.77-binding proteins in these parasites were the PY01185 and PY05995/PY03534 products. The PY01185 product was also identified as erythrocyte binding. There was no clear change in erythrocyte invasion profile suggesting that the PY01185 gene product (designated PY235EBP-2) is able to fulfill the role of EBP-1 by serving as an invasion ligand although the molecular details of its interaction with erythrocytes have not been examined. The PY01365, PY01185, and PY05995/PY03534 genes are part of a distinct subset of the py235 family. In P. falciparum, the RH protein genes are under epigenetic control and expression correlates with binding to distinct erythrocyte receptors and specific invasion pathways, whereas in P. yoelii YM all the genes are expressed and deletion of one does not result in upregulation of another. We propose that simultaneous expression of multiple Py235 ligands enables invasion of a wide range of host erythrocytes even in the presence of antibodies to one or more of the proteins and that this functional redundancy at the protein level gives the parasite phenotypic plasticity in the absence of differences in gene expression

    "Traces of our ancient religion". Meaning-making and Shamanism at Sami Offering Places at the Isogaisa Festival, Northern Norway

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    In 2010, the first shaman festival to be held in the Nordic countries opened its doors to the public in the county of Lavangen, Northern Norway (Fig. 1). The festival is named Isogaisa and presented as an indigenous festival highlighting the spiritual traditions of indigenous people. At this annual festival, shamans from all over the world gather to perform ceremonies and exchange knowledge

    Initial Reports of the Deep Sea Drilling Project, vol. 85

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    Covering Leg 85 of the cruises of the Drilling Vessel Glomar Challenger Los Angeles, California, to Honolulu, Hawaii March-April 1982. Includes six chapters: 1. INTRODUCTION: BACKGROUND AND EXPLANATORY NOTES, DEEP SEA DRILLING PROJECT LEG 85, CENTRAL EQUATORIAL PACIFIC 2. SITE 571 3. SITE 572 4. SITE 573 5. SITE 574 6. SITE 57

    Combinatorial control of temporal gene expression in the Drosophila wing by enhancers and core promoters

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    Abstract Background The transformation of a developing epithelium into an adult structure is a complex process, which often involves coordinated changes in cell proliferation, metabolism, adhesion, and shape. To identify genetic mechanisms that control epithelial differentiation, we analyzed the temporal patterns of gene expression during metamorphosis of the Drosophila wing. Results We found that a striking number of genes, approximately 50% of the Drosophila transcriptome, exhibited changes in expression during a time course of wing development. While cis-acting enhancer sequences clearly correlated with these changes, a stronger correlation was discovered between core-promoter types and the dynamic patterns of gene expression within this differentiating tissue. In support of the hypothesis that core-promoter type influences the dynamics of expression, expression levels of several TATA-box binding protein associated factors (TAFs) and other core promoter-associated components changed during this developmental time course, and a testes-specific TAF (tTAF) played a critical role in timing cellular differentiation within the wing. Conclusions Our results suggest that the combinatorial control of gene expression via cis-acting enhancer sequences and core-promoter types, determine the complex changes in gene expression that drive morphogenesis and terminal differentiation of the Drosophila wing epithelium.http://deepblue.lib.umich.edu/bitstream/2027.42/112935/1/12864_2012_Article_4965.pd
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