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The origin of uniaxial negative thermal expansion in layered perovskites

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npj computational Materials 2017年第1期3卷 89-96页

作者： chris Ablitt sarah craddock Mark s.senn Arash A.Mostofi nicholas c.Bristowe Department of Materials Imperial College LondonLondon SW72AZUK Department of chemistry University of OxfordSouth Parks RoadOxford OX13QRUK Department of chemistry University of WarwickGibbet HillCoventry CV47ALUK Department of Physics Imperial College LondonLondon SW72AZUK school of Physical sciences University of KentCanterbury CT27NHUK

Why is it that ABO3 perovskites generally do not exhibit negative thermal expansion(NTE)over a wide temperature range,whereas layered perovskites of the same chemical family often do?It is generally accepted that there are two key ingredients that determine the extent of NTE:the presence of soft phonon modes that drive contraction(have negative Grüneisen parameters);and anisotropic elastic compliance that predisposes the material to the deformations required for NTE along a specific *** difference in thermal expansion properties is surprising since both ABO3 and layered perovskites often possess these ingredients in equal measure in their high-symmetry *** first principles calculations and symmetry analysis,we show that in layered perovskites there is a significant enhancement of elastic anisotropy due to symmetry breaking that results from the combined effect of layering and condensed rotations of oxygen *** feature,unique to layered perovskites of certain symmetry,is what allows uniaxial NTE to persist over a large temperature *** fundamental insight means that symmetry and the elastic tensor can be used as descriptors in high-throughput screening and to direct materials design.

关键词： perovskite layered symmetry

Assessment of strain bursting in deep tunnelling by using the finite-discrete element method

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Journal of Rock Mechanics and Geotechnical Engineering 2019年第1期11卷 12-37页

作者： Ioannis Vazaios Mark s.Diederichs nicholas Vlachopoulos Department of ceological saences and ceological Engineering Queen's UniversityKingstonCanada

Rockbursting in deep tunnelling is a complex phenomenon posing significant challenges both at the design and construction stages of an underground excavation within hard rock masses and under high in situ stresses. While local experience, field monitoring, and informed data-rich analysis are some of the tools commonly used to manage the hazards and the associated risks, advanced numerical techniques based on discontinuum modelling have also shown potential in assisting in the assessment of rockbursting. In this study, the hybrid finite-discrete element method(FDEM) is employed to investigate the failure and fracturing processes, and the mechanisms of energy storage and rapid release resulting in bursting, as well as to assess its utility as part of the design process of underground *** the calibration of the numerical model to simulate a deep excavation in a hard, massive rock mass, discrete fracture network(DFN) geometries are integrated into the model in order to examine the impact of rock structure on rockbursting under high in situ stresses. The obtained analysis results not only highlight the importance of explicitly simulating pre-existing joints within the model, as they affect the mobilised failure mechanisms and the intensity of strain bursting phenomena, but also show how the employed joint network geometry, the field stress conditions, and their interaction influence the extent and depth of the excavation induced damage. Furthermore, a rigorous analysis of the mass and velocity of the ejected rock blocks and comparison of the obtained data with well-established semi-empirical approaches demonstrate the potential of the method to provide realistic estimates of the kinetic energy released during bursting for determining the energy support demand.

关键词： Rockburst Finite-discrete element method(FDEM) Deep tunnelling Hard rock excavations Brittle fracturing Discrete fracture network(DFN)

Machine learning for the discovery of molecular recognition based on single-walled carbon nanotube corona-phases

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npj computational Materials 2022年第1期8卷 1265-1277页

作者： Xun Gong nicholas Renegar Retsef Levi Michael s.strano Massachusetts Institute of Technology Department of Chemical EngineeringCambridgeMAUSA Massachusetts Institute of Technology Operations Research CenterCambridgeMAUSA Massachusetts Institute of Technology Sloan School of ManagementCambridgeMAUSA

Nanoparticle corona phase(cP)design offers a unique approach toward molecular recognition(MR)for sensing ***-walled carbon nanotube(sWcNT)cPs can additionally transduce MR through its band-gap photoluminescence(PL).While DNA oligonucleotides have been used as sWcNT cPs,no generalized scheme exists for MR prediction de novo due to their sequence-dependent three-dimensional *** work generated the largest DNA-sWcNT PL response library of 1408 elements and leveraged machine learning(ML)techniques to understand MR and DNA sequence dependence through local(LFs)and high-level features(HLFs).Out-of-sample analysis of our ML model showed significant correlations between model predictions and actual sensor responses for 6 out of 8 experimental *** HLF combinations were found to be uniquely correlated with different ***,models utilizing both LFs and HLFs show improvement over that with HLFs alone,demonstrating that DNA-sWcNT cP engineering is more complex than simply specifying molecular properties.

关键词： walled carbon utilizing

Predicting phosphorus sorption isotherm parameters in soil using data of routine laboratory tests

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Pedosphere 2021年第5期31卷 694-704页

作者： Kathleen s.DUNNE nicholas M.HOLDEN Karen DALY Teagasc Johnstown CastleEnvironmental Research CentreCo.Wexford Y35TC97(Ireland) UcD school of Biosystems and Food Engineering University College DublinBelfieldDublin 4 D04VIW8(Ireland)

Knowledge of phosphorus(P)sorption dynamics across different soil types could direct agronomic and environmental management of *** objective of this study was to predict P isotherm parameters for a national soil population using data of routine laboratory *** and Freundlich sorption parameters were calculated from two different ranges(0-25 and 0-50 mg P L^(-1))using an archive of representative agricultural soil types from *** linear regression(MLR)identified labile forms of aluminium(Al)and iron(Fe),organic matter(OM),cation exchange capacity(cEc),and clay as significant *** and Freundlich sorption capacities,Freundlich affinity constant,and Langmuir buffer capacity were predicted reliably,with R^(2) of independent validation>*** isotherm parameters were predicted from P sorbed at a single concentration of 50 mg P L^(-1)(s_(50)).An MLR prediction of P sorption maximum in the 0-50 mg P L-1 range was achieved,to an accurate standard,using s_(50),OM,and Mehlich-3 Fe(R^(2) of independent calibration and validation being 0.91 and 0.95,respectively).Using Giles’four shapes of isotherms(c,L,H,and s),L non-strict-and c-shaped isotherm curves accounted for 64% and 27% of the soils,*** clustering identified a separation of isotherm curves influenced by two ranges of Mehlich-3 *** with a low range of Mehlich-3 Al(2.5-698 mg kg^(-1))had no incidence of rapid sorption(c shape).single point indices,Al,or available soil data make the regression approach a feasible way of predicting Langmuir parameters that could be included with standard agronomic soil P testing.

关键词： available phosphorus binding fertilizer soil test sorption maximum

conjunctions and/or Disjunctions： Radical Empiricism in the History of Philosophy

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Frontiers of Philosophy in china 2014年第1期9卷 130-148页

作者： nicholas s. Brasovan Department of Philosophy and Religion University of Central Arkansas AR 72035 USA

William James challenged the traditions of British Empiricism （Hume） on one hand and German Idealism （Kant and Hegel） on the other. James＇＂Radical Empiricism＂ is a via media （＂middle road＂） between these divergent positions. His central points of contention are the ontological status of relationships and the correct analysis of experience. British Empiricism leaves us with a world of separate, particular facts, based on atomic sense impressions. Idealists, on the other hand, claim that all worldly phenomena are conjoined by one rational principle. According to James＇ account, neither side recognizes that both conjunctive and disjunctive relations are integral to experience. Furthermore, James＇ critique proved to influence A. N. Whitehead＇s philosophy of experience and orientation toward Hume and Kant. This essay situates James＇ philosophy in this polemical and historical context.

关键词： William James Radical Empiricism American philosophy Kant,Whitehead Hume Hegel

Modelling of Propagating shear Waves in Biotissue Employing an Internal Variable Approach to Dissipation

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communications in computational Physics 2008年第3期3卷 603-640页

作者： H.T.Banks nicholas s.Luke center for Research in scientific computation North Carolina State UniversityRaleighNC 27695-8205USA.

The ability to reliably detect coronary artery disease based on the acousticnoises produced by a stenosis can provide a simple, non-invasive technique for *** research exploits the shear wave fields in body tissue to detect andanalyze coronary stenoses. The methods and ideas outlined in earlier efforts [6] includinga mathematical model utilizing an internal strain variable approximation tothe quasi-linear viscoelastic constitutive equation proposed by Fung in [19] is extendedhere. As an initial investigation, a homogeneous two-dimensional viscoelastic geometryis considered. Being uniform in θ, this geometry behaves as a one dimensionalmodel, and the results generated from it are compared to the one dimensional resultsfrom [6]. To allow for different assumptions on the elastic response, several variationsof the model are considered. A statistical significance test is employed to determine ifthe more complex models are significant improvements. After calibrating the modelwith a comparison to previous findings, more complicated geometries are *** involving a heterogeneous geometrywith a uniformring running throughthe original medium, a θ-dependent model which considers a rigid partial occlusionformed along the inner radius of the geometry, and a model which combines the ringand occlusion are presented.

关键词： Viscoelasticity partial differential equations shear waves biotissue.

characterization of spatial relationships between three remotely sensed indirect indicators of biodiversity and climate:a 21years’data series review across the canadian boreal forest

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International Journal of Digital Earth 2016年第7期9卷 676-696页

作者： Liliana Perez Trisalyn Nelson nicholas c.coops Fabio Fontana c.Ronnie Drever Laboratory of Environmental Geosimulation(LEDGE) Department of GeographyUniversity of MontrealMontrealQCCanada spatial Pattern Analysis&Research(sPAR)Lab Department of GeographyUniversity of VictoriaVictoriaBCCanada Department of Forest Resources Management University of British ColumbiaVancouverBCCanada The Nature conservancy OttawaONCanada

climate drives ecosystem processes and impacts *** patterns over large areas,such as canada’s boreal,can be monitored using indirect indicators derived from remotely sensed *** this paper,we characterized the historical space–time relationships between climate and a suite of indirect indicators of biodiversity,known as the Dynamic Habitat Index(DHI)to identify where climate variability is co-occurring with changes in biodiversity *** represented biodiversity using three indirect indicators generated from 1987 to 2007 National Oceanic and Atmospheric Administration Advanced Very High Resolution Radiometer *** quantifying and clustering temporal variability in climate data,we defined eight homogeneous climate variability zones,where we then analyzed the *** identified unique areas of change in climate,such as the Hudson Plains,that explain significant variations in *** variability in temperatures and growing season index had a strong influence on observed vegetation productivity and seasonality changes throughout canada’s *** in precipitation,for most of the area,was not associated with DHI *** methodology presented here enables assessment of spatial–temporal relationships between biodiversity and climate variability and characterizes distinctive zones of variation that may be used for prioritization and planning to ensure long-term biodiversity conservation in canada.

关键词： climate change biodiversity boreal forest spatial–temporal analysis fPAR DHI

Mapping tree canopies in urban environments using airborne laser scanning (ALs):a Vancouver case study

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Forest Ecosystems 2018年第4期5卷 429-437页

作者： Giona Matasci nicholas c.coops David A.R.Williams Nick Page Department of Forest Resource Management Unlversity of British Columbia2424Main MallVancouverBC V6T IZ4Canada Vancouver Board of Parks and Recreation 2099Beach AvenueVancouverBC V6G IZ4Canada

Background: The distribution of forest vegetation within urban environments is critically important as it influences urban environmental conditions and the energy exchange through the absorption of solar radiation and modulation of evapotranspiration. It also plays an important role filtering urban water systems and reducing storm water ***: We investigate the capacity of ALs data to individually detect, map and characterize large(taller than15 m) trees within the city of Vancouver. Large trees are critical for the function and character of Vancouver’s urban forest. We used an object-based approach for individual tree detection and segmentation to determine tree locations(position of the stem), to delineate the shape of the crowns and to categorize the latter either as coniferous or ***: Results indicate a detection rate of 76.6% for trees > 15 m with a positioning error of 2.11 m(stem location). Extracted tree heights possessed a RMsE of 2.60 m and a bias of-1.87 m, whereas crown diameter was derived with a RMsE of 3.85 m and a bias of-2.06 m. Missed trees are principally a result of undetected treetops occurring in dense, overlapping canopies with more accurate detection and delineation of trees in open ***: By identifying key structural trees across Vancouver’s urban forests, we can better understand their role in providing ecosystem goods and services for city residents.

关键词： Urban forest Large trees Light detection and ranging Airborne laser scanning

Disease spectrum and use of cholecystolithotomy in gallstone ileus

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Hepatobiliary & Pancreatic Diseases International 2012年第5期11卷 553-557页

作者： nicholas E Williams Justin s Gundara sophia Roser Jaswinder s samra Upper Gastrointestinal surgical Unit Royal North Shore HospitalUniversity of SydneySt.LeonardsSydneyNSW 2065Australia

BAcKGROUND: Gallstone ileus is a heterogeneous and highly morbid condition that suffers from a lack of consensus regarding the timing and approach to management of the biliary tree and associated fistula. METHODs: We report three cases that demonstrate the spectrum of gallstone ileus with classical examples of both Barnard’s and Bouveret’s syndromes. clinical presentation diagnostic imaging, surgical technique and outcome are discussed. REsULTs: One patient with Barnard’s syndrome presented with recurrent gallstone ileus. To minimize the risks of complex, definitive biliary surgery and avoid further recurrent episodes, a cholecystolithotomy was performed with effect Two cases of Bouveret’s syndrome were successfully managed with enterolithotomy/cholecystectomy and multivisceral resection respectively, thus highlighting the diverse nature of this disease and management options. cONcLUsIONs: Following enterolithotomy, potentially morbid definitive one-stage surgery in typically compromised, elderly patients needs to be weighed against the risk of recurrence and ongoing biliary pathology. We suggest the use of open cholecystolithotomy for the removal of residual gallstones when the patient is not suitable for definitive biliary surgery.

关键词： cholecystectomy biliary tract disease gallstone ileus biliary tract surgery