检索结果-南通市图书馆

Deconvolving the pre-Himalayan Indian margin-Tales of crustal growth and destruction

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2019年第3期10卷 863-872页

作者： christopher J.Spencer Brendan Dyck Catherine m.mottram Nick m.W.Roberts Wei-Hua Yao Erin L.martin Earth Dynamics Research Group The Institute for Geoscience Research (TIGeR) Department of Applied Geology Curtin University NERC Isotope Geosciences Laboratory British Geological Survey Department of Earth Sciences Simon Fraser University University Drive Department of Environment Earth and Ecosystems The Open UniversityWalton Hall Milton Keynes MK7 6AA UK School of Earth and Environmental Sciences University of Portsmouth Schoolof Earth Sciences and Engineering SunYat-sen University

The metamorphic core of the Himalaya is composed of Indian cratonic rocks with two distinct crustal affinities that are defined by radiogenic isotopic geochemistry and detrital zircon age spectra. One is derived predominantly from the Paleoproterozoic and Archean rocks of the Indian cratonic interior and is either represented as metamorphosed sedimentary rocks of the Lesser Himalayan Sequence(LHS) or as slices of the distal cratonic margin. The other is the Greater Himalayan Sequence(GHS) whose provenance is less clear and has an enigmatic affinity. Here we present new detrital zircon Hf analyses from LHS and GHS samples spanning over 1000 km along the orogen that respectively show a striking similarity in age spectra and Hf isotope ratios. Within the GHS, the zircon age populations at 2800-2500 ma,1800 ma, 1000 ma and 500 ma can be ascribed to various Gondwanan source regions; however, a pervasive and dominant Tonianage population(～860-800 ma) with a variably enriched radiogenic Hf isotope signature(eHf = 10 to-20) has not been identified from Gondwana or peripheral accreted terranes. We suggest this detrital zircon age population was derived from a crustal province that was subsequently removed by tectonic erosion. Substantial geologic evidence exists from previous studies across the Himalaya supporting the Cambro-Ordovician Kurgiakh Orogeny. We propose the tectonic removal of Tonian lithosphere occurred prior to or during this Cambro-Ordovician episode of orogenesis in a similar scenario as is seen in the modern Andean and Indonesian orogenies, wherein tectonic processes have removed significant portions of the continental lithosphere in a relatively short amount of time. This model described herein of the pre-Himalayan northern margin of Greater India highlights the paucity of the geologic record associated with the growth of continental crust. Although the continental crust is the archive of Earth history, it is vital to recognize the ways in which preservation

关键词： Himalaya Gondwana Zircon Subduction erosion

macroscopic analysis of time dependent plasticity in Ti alloys

在线全文

学校读者我要写书评

暂无评论

Journal of materials Science & Technology 2022年第29期124卷 135-140页

作者： Yi Xiong Phani S.Karamched Chi-Toan Nguyen David m.Collins christopher m.magazzeni Edmund Tarleton Angus J.Wilkinson Department of materials University of OxfordParks RoadOxford OX13PHUnited Kingdom Department of materials and Processes Safran SASafran TechMany-les-Hameaux 78772France School of metallurgy and materials University of BirminghamEdgbastonBirmingham B152TTUnited Kingdom Department of Engineering Science University of OxfordParks RoadOxford OX13PJUnited Kingdom

Cold dwell fatigue is the critical technological issue in Ti alloys used in the cooler front sections of aerospace jet *** subjected to a sustained load(stress dwell),the lifetime of these Ti components can be drastically reduced by as much as an order of magnitude[1–4].Without a clear understanding of the effect,safety concerns are raised.

关键词： alloys fatigue lifetime

Time-resolved, defect-hosted, trace element mobility in deformedWitwatersrand pyrite

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2019年第1期10卷 55-63页

作者： Denis Fougerouse Steven m.Reddy christopher L.Kirkland David W.Saxey William D.Rickard Robert m.Hough School of Earth and Planetary Sciences The Institute for Geoscience Research (TIGeR) Curtin University Geoscience Atom Probe Advanced Resource Characterisation Facility John de Laeter Centre Curtin University CSIRO minerals Resources

The Pb isotopic composition of rocks is widely used to constrain the sources and mobility of melts and hydrothermal fluids in the Earth's crust. In many cases, the Pb isotopic composition appears to represent mixing of multiple Pb reservoirs. However, the nature, scale and mechanisms responsible for isotopic mixing are not well known. Additionally, the trace element composition of sulphide minerals are routinely used in ore deposit research, mineral exploration and environmental studies, though little is known about element mobility in sulphides during metamorphism and deformation. To investigate the mechanisms of trace element mobility in a deformed Witwatersrand pyrite(FeS_2), we have combined electron backscatter diffraction(EBSD) and atom probe microscopy(APm). The results indicate that the pyrite microstructural features record widely different Pb isotopic compositions, covering the entire range of previously published sulphide Pb compositions from the Witwatersrand basin. We show that entangled dislocations record enhanced Pb, Sb, Ni, Tl and Cu composition likely due to entrapment and short-circuit diffusion in dislocation cores. These dislocations preserve the Pb isotopic composition of the pyrite at the time of growth(~3 Ga) and show that dislocation intersections, likely to be common in deforming minerals, limit trace element mobility. In contrast, Pb, As, Ni, Co, Sb and Bi decorate a highangle grain boundary which formed soon after crystallisation by sub-grain rotation *** isotopic composition within this boundary indicates the addition of externally-derived Pb and trace elements during greenschist metamorphism at ~2 Ga. Our results show that discrete Pb reservoirs are nanometric in scale, and illustrate that grain boundaries may remain open systems for trace element mobility over 1 billion years after their formation.

关键词： Atom probe microscopy Nanoscale Nanogeochronology microstructure Isotope geochemistry Common Pb

A machine learning approach to tungsten prospectivity modelling using knowledge-driven feature extraction and model confidenc

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2020年第6期11卷 2067-2081页

作者： christopher m.Yeomans Robin K.Shail Stephen Grebby Vesa Nykanen maarit middleton Paul A.J.Lusty Camborne School of mines College of EngineeringMathematics and Physical SciencesUniversity of ExeterPenryn CampusPenrynCornwallTR109FEUK British Geological Survey Environmental Science CentreKeyworthNottinghamshireNG125GGUK University of Nottingham Nottingham Geospatial InstituteInnovation ParkNottinghamNG72TUUK Geological Survey of Finland P.O.Box 77FI-96101RovaniemiFinland

Novel mineral prospectivity modelling presented here applies knowledge-driven feature extraction to a datadriven machine learning approach for tungsten *** method emphasises the importance of appropriate model evaluation and develops a new Confidence metric to generate spatially refined and robust exploration *** data-driven Random ForestTm algorithm is employed to model tungsten mineralisation in SW England using a range of geological,geochemical and geophysical evidence layers which include a depth to granite evidence *** models are presented,one using standardised input variables and a second that implements fuzzy set theory as part of an augmented feature extraction *** use of fuzzy data transformations mean feature extraction can incorporate some user-knowledge about the mineralisation into the *** typically subjective approach is guided using the Receiver Operating Characteristics(ROC)curve tool where transformed data are compared to known training *** modelling is conducted using 34 known true positive samples with 10 sets of randomly generated true negative samples to test the random effect on the *** two models have similar accuracy but show different spatial distributions when identifying highly prospective *** analysis shows that the fuzzy-transformed model is a better discriminator and highlights three areas of high prospectivity that were not previously *** Confidence metric,derived from model variance,is employed to further evaluate the *** new metric is useful for refining exploration targets and highlighting the most robust areas for follow-up *** fuzzy-transformed model is shown to contain larger areas of high model confidence compared to the model using standardised ***,legacy mining data,from drilling reports and mine descriptions,is used to further validate the fuzzy-transformed model and gauge the depth of potential *** of m

关键词： machine learning mineral prospectivity modelling mineral exploration Random ForestTm Tungsten SW England

Continuous synthesis of iron oxide （Fe3O4） nanoparticles via thermal decomposition

在线全文

学校读者我要写书评

暂无评论

Particuology 2016年第3期14卷 47-53页

作者： William Glasgow Ben Fellows Bin Qi Taghi Darroudi christopher Kitchens Longfei Ye Thomas m. Crawford O. Thompson mefford Department of material Science and Engineering Center for Optical Materials Science and Engineering Technologies Clemson University 91 Technology Drive Anderson SC29625 USA Electron microscopy Laboratory Department of Materials Science and Engineering Clemson University Clemson SC29625 USA Department of Chemical and Biomolecular Engineering Clemson University Clemson SC 29634 USA Department of Physics and Astronomy and Smart State Center for Experimental Nanoscale Physics University of South Carolina 712 Main Street Columbia SC29208 USA

Iron oxide nanoparticles have become of great interest in the medical field for their potential uses in areas such as biomagnetic imaging and hypothermia cancer treatment. Traditionally, particles for these applications are produced through batch-based methodologies. Herein, we demonstrate an alternative continuous flow production method for the synthesis of Fe304 iron oxide nanoparticles. Advantages of continuous flow over the batch method include consistent formation of uniformly spherical particles, thorough mixing of reactants, and capacity for high-volume particle production. In this study, a continu- ous flow reaction mechanism was proposed in which stoichiometric control of reactants had the potential to control final particle size. The project was conducted under the supposition that the iron oleatelligand ratio in the precursor was the greatest size control factor, with a higher ratio resulting in smaller parti- cles. The resulting particles produced by this continuous method were characterized by high-resolution transmission electron microscopy, X-ray diffraction, and magnetometry.

关键词： Continuous flow Iron oxide magnetiteSynthesis

Research in spinal surgery: Evaluation and practice of evidence-based medicine

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Orthopedics 2014年第2期5卷 89-93页

作者： m.rk E Oppenlander christopher m maulucci George m Ghobrial James S Harrop Department of Neurological Surgery Thomas Jefferson University Hospital Philadelphia PA19107 United States Division of Neurological Surgery Barrow Neurological Institute St. Joseph Hospital and Medical CenterPhoenix AZ 85003 United States

Evidence-based medicine(EBm) is a common concept among medical practitioners, yet unique challenges arise when EBm is applied to spinal surgery. Due to the relative rarity of certain spinal disorders, and a lack of management equipoise, randomized controlled trials may be difficult to execute. Despite this, responsibility rests with spinal surgeons to design high quality studies in order to justify certain treatment modalities. The authors therefore review the tenets of implementing evidencebased research, through the lens of spinal disorders. The process of EBm begins with asking the correct *** appropriate study is then designed based on the research question. Understanding study designs allows the spinal surgeon to assess the level of evidence *** outcome measurements allow clinicians to communicate the success of treatment strategies, and will increase the quality of a given study design. Importantly,one must recognize that the randomized controlled trial is not always the optimal study design for a given research question. Rather, prospective observational cohort studies may be more appropriate in certain circumstances, and would provide superior generalizability. Despite the challenges involved with EBm, it is the future of medicine. These issues surrounding EBm are important for spinal surgeons, as well as health policy makers and editorial boards, to have familiarity.

关键词： Evidence-based medicine Spinal surgery Trial design Research methodology

Employment and Patient Satisfaction after Liver Transplantation

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

Journal of Clinical and Translational Hepatology 2020年第3期8卷 299-303页

作者： christopher Cao Dina Halegoua-Demarzio Shady Guirguis Crystal Chen Jonathan m.Fenkel Steven Herrine Department of Gastroenterology and Hepatology Thomas Jefferson University HospitalsPhiladelphiaPAUSA

Background and Aims:This study serves to revisit the effects of liver transplantation(LT)on employment in an era of improving survival outcomes post-transplant,and to identify areas of improvement in the transplant process to better optimize post-LT employment and patient ***:Prospectively,patients who had undergone LT at a single tertiary LT center were surveyed in person and by *** outcomes included employment rate pre-and post-LT,annual salary,weekly hours worked,barriers to re-employment,and patient ***:Responses were collected and analyzed from 121 patients who underwent ***-LT,68(56.1%)reported full-time employment,13(10.7%)part-time employment,and 40(33.1%)***-LT,26(21.4%)reported continued full-time employment,18(14.9%)part-time employment,and 77(63.6%)*** weekly work hours decreased post-LT(16.1 h/week vs.39.9 h/week).mean annual salaries decreased post-LT(17 earning salary≥$40,000 vs.56 earning salary≥$40,000).These outcomes differed from patient pre-LT expectations,with 81.0%of previously employed patients believing they would return to employment,resulting in decreased patient *** working physically demanding jobs pre-LT were less likely to return to *** cited for lack of return to full employment included early fatigue and difficulty regaining physical ***:Re-employment rates remain low post-LT,which is particularly true for patients working physically active *** is a significant barrier to re-employment and increased physical rehabilitation post-LT may prove to be *** should be given realistic expectations about return to employment prior to their LT.

关键词： Liver Transplant Liver transplant Employment Patient satisfaction

Presentation and outcomes of chronic rhinosinusitis following liver and kidney transplant

维普期刊数据库评论

在线全文

维普期刊数据库

学校读者我要写书评

暂无评论

World Journal of Otorhinolaryngology-Head and Neck Surgery 2021年第9期7卷 139-145页

作者： Aviv Spillinger christopher m.Low Byron m.Smith Janalee K.Stokken Erin K.O'Brien Garret Choby Deportment of Otoloryngolosy-Head and Neck Surgery Mayo ClinicRochesterMN55905USA Biomedical Statistics and Informatics Mayo ClinicRochesterMN55905USA

non-invasive chronic rhinosinusitis(CRS)following liver or kidney transplant and determine factors associated with disease-related complications,selection of endoscopic sinus surgery(ESS),and disease resolution in this *** design:Retrospective chart ***:An academic tertiary care center(mayo Clinic,Rochester,minnesota).Subjects and methods:Liver and kidney transplant recipients evaluated by mayo Clinic otolaryngologists for CRS between 1998 and 2018 were *** and multivariate logistic regression analyses were used to determine patient factors and treatment modalities associated with developing complications,selection of ESS,and disease ***:Fifty-seven patients met inclusion *** patients developed intraorbital or intracranial complications of their *** modeling demonstrated that the presence of polyps(P=0.036)was associated with undergoing ESS within one year of presentation.A higher Lund-mackay(Lm)computed tomography score(P=0.023)and older age(P=0.018)were significantly associated with decreased disease *** other factors were significantly associated with the use of endoscopic sinus surgery within one year of otolaryngology presentation or resolution of CRS in this ***:The risk of developing CRS-related intraorbital or intracranial complications in this immunecompromised patient cohort may be lower than originally *** liver-and kidney-recipients stable on immunosuppressive medication for many years,prognostic factors for CRS may mirror those for immunocompetent patients.

关键词： Rhinosinusitis Chronic rhinosinusitis Non-invasive rhinosinusitis Kidney transplant Liver transplant Immunocompromised Immunosuppressed

同方期刊数据库

A machine learning approach for regional geochemical data:Platinum-group element geochemistry vs geodynamic settings of the North Atlantic Igneous Province

在线全文

学校读者我要写书评

暂无评论

Geoscience Frontiers 2021年第3期12卷 42-59页

作者： Jordan J.Lindsay Hannah S.R.Hughes christopher m.Yeomans Jens C.Ø.Andersen Iain mcDonald Camborne School of mines University of ExeterPenryn CampusPenrynCornwall TR109FEUnited Kingdom School of Earth and Ocean Sciences Main CollegeCardiff UniversityPark PlaceCardiff CF103ATUnited Kingdom

Whilst traditional approaches to geochemistry provide valuable insights into magmatic processes such as melting and element fractionation,by considering entire regional data sets on an objective basis using machine learning algorithms(mLAs),we can highlight new facets within the broader data structure and significantly enhance previous geochemical *** platinum-group element(PGE)budget of lavas in the North Atlantic Igneous Province(NAIP)has been shown to vary systematically according to age,geographic location and geodynamic *** the large multi-element geochemical data set available for the region,mLAs were employed to explore the magmatic controls on these shifting *** key advantage of using machine learning in analysis is its ability to cluster samples across multi-dimensional(i.e.,multi-element)*** NAIP data set is manipulated using Principal Component Analysis(PCA)and t-Distributed Stochastic Neighbour Embedding(t-SNE)techniques to increase separability in the data alongside clustering using the k-means *** new multi-element classification is compared to the original geographic classification to assess the performance of both *** workflow provides a means for creating an objective high-dimensional investigation on a geochemical data set and particularly enhances the identification of metallogenic anomalies across the *** techniques used highlight three distinct multi-element end-members which successfully capture the variability of the majority of elements included as input *** end-members are seen to fluctuate in prominence throughout the NAIP,which we propose reflects the changing geodynamic environment and melting ***,the variability of Pt and Pd are not reflected in mLA-based clustering trends,suggesting that they vary independently through controls not readily demonstrated by the NAIP major or trace element data structure(i.e.,other proxies for magmatic differe

关键词： Platinum-group elements machine learning Plume Geochemistry metallogenesis mantle