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Small-Scale Mineralogical Heterogeneity from Variations in Phase Assemblages in the Transition Zone and D" Layer Predicted by Convection Modelling

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Journal of Earth Science 2011年第2期22卷 160-168页

作者： Arie P van den berg David A Yuen Michael H G Jacobs Maarten V de Hoop Earth Sciences department Utrecht University department of Geology and Geophysics and Minnesota Supercomputing Institute University of MinnesotaMinneapolisMN 55415USA Institut für Metallurgie TU ClausthalClausthal-ZellerfeldGermany department of Mathematics and Center of Applied and Computational Mathematics Purdue UniversityWest LafayetteINUSA

Small-scale heterogeneity in the deep mantle is concentrated in the upper-mantle transition zone （TZ）, in the depth range 410-660 km and also at the bottom 250 km D＂ region. This encourages a more detailed investigation of the potential for seismic reflectivity imaging by modelling heterogeneous structures in mantle convection models including phase transitions of the TZ and D＂ regions. We applied finite elements with variable spacing near the boundary layers in 2-D cylindrical geometry that allow for sufficient spatial resolution. We investigated several models including an extended Boussinesq （EBA） model, focused on the D＂ region, and a compressible （ALA） model for the TZ region. The results for the D＂ region show typical lens-shaped structures of post-perovskite （PPV） embedded in the perovskite （PV） background mantle, where the thickness of the lenses, at 200-400 km, strongly depends on the Clapeyron slope of the PV-PPV transition. A second phase transition （double crossing） occurs in case the core temperature is higher than the intercept temperature Ti. Our phase-dependent rheology results in contrasting effective viscosity between PV and PPV. Our model results reveal a distinctly clear mechanical weakening of the PPV lenses with about an order of magnitude lower viscosity. The shear wave-speed distributions computed from our convection results are strongly correlated with the heterogeneous distribution of the mineral phase. Gradients in the seismic wave-speed that are the target of seismological reflectivity imaging are clearly revealed. The wave-speed results show a clear resolution of the top and bottom interfaces of the PPV lenses. Our ALA model for the TZ is based on a thermodynamical model for the magnesium end- member of an olivine-pyroxene mantle. The model predicts a much more complex distribution of mineral phases, compared to our D＂ results, in agreement with the greater number of mineral phases involved in the olivine-pyroxene phase diagram for the P

关键词： mantle convection phase transition post-perovskite mineralogical heterogeneity.

The influence of disturbance on driving carbon stocks and tree dynamics of riparian forests in Cerrado

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Journal of Plant Ecology 2018年第3期11卷 401-410页

作者： Matheus Henrique Nunes Marcela de Castro Nunes Santos Terra Izabela Regina Cardoso de Oliveira Eduardo van den berg department of Plant Sciences University of CambridgeDowning StreetCambridge CB23EAUK department of Forest Sciences Federal University of Lavras1001Doutor Sylvio Menicucci AvenueLavras 37200-000Brazil department of Exact Science Federal University of Lavras1001Doutor Sylvio Menicucci AvenueLavras 37200-000Brazil department of Biology Federal University of Lavras1001Doutor Sylvio Menicucci AvenueLavras 37200-000Brazil

Aims Riparian forests in the Brazilian Cerrado,also known as gallery forests,are very heterogeneous in structure,species composition and ecological features due to strong and abrupt variations of soil,hydrological and topographic ***,what are the variables driving forest carbon stock and productivity,mortality and recruitment in disturbed gallery forests?Methods We used 36 permanent plots data from a gallery forest in the Brazilian *** investigated how tree community dynam-ics vary in a gallery forest on two contrasting disturbance levels-logged and non-logged-across a topographic gradient intrinsically related to differences in moisture conditions,edge effects,as well as soil fertility and *** Findings Soil variables were reduced into principal components and we used structural equation modelling to disentangle covarying *** also included carbon stocks as a determinant variable of dynamics *** forest had 50%higher productivity than non-logged forest and streamside forest had aboveground carbon stocks 70%higher than the forest *** logging and natural disturbance drove variation in the carbon stocks which contributed to shaping productivity and recruitment *** from the river also drove mortality and carbon stock *** with high-carbon stocks favoured higher competition and lessened produc-tivity and recruitment *** soil fertility and texture are considered crucial components shaping forest dynamics,there was no clear influence of those variables on the present forest,probably because the strong effects of soil moisture,forest edge and distur-bance disrupted the correlation between soil and forest dynamics.

关键词： riparian vegetation topography soil properties disturbance gallery forest structural equation modelling

decision support model for effects estimation and proportionality assessment for targeting in cyber operations

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defence Technology（防务技术） 2021年第2期17卷 352-374页

作者： C.Maathuis W.Pieters J.van den berg delft University of Technology Jaffalaan 52628 BXDelftNetherlands TNO Military Operations Oude Waaldorperweg 632597 AKDen HaagNetherlands Netherlands defense Academy De la Reyweg 1204818 BBBredaNetherlands Open University of the Netherlands Valkenburgerweg 1776419 ATHeerlenNetherlands

Cyber operations are relatively a new phenomenon of the last two *** that period,they have increased in number,complexity,and agility,while their design and development have been processes well kept under *** a consequence,limited data(sets)regarding these incidents are *** various academic and practitioner public communities addressed some of the key points and dilemmas that surround cyber operations(such as attack,target identification and selection,and collateral damage),still methodologies and models are needed in order to plan,execute,and assess them in a responsibly and legally compliant *** on these facts,it is the aim of this article to propose a model that i))estimates and classifies the effects of cyber operations,and ii)assesses proportionality in order to support targeting decisions in cyber *** order to do that,a multi-layered fuzzy model was designed and implemented by analysing real and virtual realistic cyber operations combined with interviews and focus groups with technical e military *** proposed model was evaluated on two cyber operations use cases in a focus group with four technical e military *** the design and the results of the evaluation are revealed in this article.

关键词： Cyber operations Cyber warfare Cyber weapons Artificial intelligence Fuzzy logic Targeting

Combining two-photon lithography with laser ablation of sacrificial layers:A route to isolated 3D magnetic nanostructures

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Nano Research 2023年第1期16卷 1441-1447页

作者： Arjen van den berg Mylène Caruel Matthew Hunt Sam Ladak School of Physics and Astronomy Cardiff UniversityCardiffCF243AAUK Institut National des Sciences Appliquées(INSA)of Toulouse 35 Avenue de Rangueil31400 ToulouseFrance

Three-dimensional(3D)nanostructured functional materials are important systems allowing new means for intricate control of electromagnetic properties.A key problem is realising a 3D printing methodology on the nanoscale that can yield a range of functional *** this article,it is shown that two-photon lithography,when combined with laser ablation of sacrificial layers,can be used to realise such a vision and produce 3D functional nanomaterials of complex ***-of-principle is first shown by fabricating planar magnetic nanowires raised above the substrate that exhibit controlled domain wall injection and ***,3D artificial spin-ice(3DASI)structures are fabricated,whose complex switching can be probed using optical *** show that by careful analysis of the magneto-optical Kerr effect signal and by comparison with micromagnetic simulations,depth dependent switching information can be obtained from the 3DASI *** work paves the way for new materials,which exploit additional physics provided by non-trivial 3D geometries.

关键词： three-dimensional(3D)nanomagnetism 3D lithography 3D artificial spin ice sacrificial layers magneto-optical Kerr effect

Post-Mortem MRI and Histopathology in Neurologic Disease:A Translational Approach

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Neuroscience Bulletin 2019年第2期35卷 229-243页

作者： Laura E.Jonkman Boyd Kenkhuis Jeroen J.G.Geurts Wilma D.J.van de berg department of Anatomy and Neurosciences Amsterdam Neuroscience Amsterdam UMC Vrije Universiteit Amsterdam department of Human Genetics Leiden University Medical Center department of Radiology Leiden University Medical Center

In this review, combined post-mortem brain magnetic resonance imaging(MRI) and histology studies are highlighted, illustrating the relevance of translational approaches to de?ne novel MRI signatures of neuropathological lesions in neuroin?ammatory and neurodegenerative disorders. Initial studies combining post-mortem MRI and histology have validated various MRI sequences,assessing their sensitivity and speci?city as diagnostic biomarkers in neurologic disease. More recent studies have focused on de?ning new radiological(bio)markers and implementing them in the clinical(research) setting. By combining neurological and neuroanatomical expertise with radiological development and pathological validation,a cycle emerges that allows for the discovery of novel MRI biomarkers to be implemented in vivo. Examples of this cycle are presented for multiple sclerosis, Alzheimer's disease, Parkinson's disease, and traumatic brain *** applications have been shown to be successful, while others require further validation. In conclusion, there is much to explore with post-mortem MRI and histology studies, which can eventually be of high relevance for clinical practice.

关键词： MRI Histology Biomarkers Multiple sclerosis Alzheimer’s disease Parkinson’s disease

Extending the dynamic temperature range of Boltzmann thermometers

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Light(Science & Applications) 2022年第12期11卷 3069-3079页

作者： Thomas Pieter van Swieten Jesse Merlijin Steenhoff Auke Vlasblom Ravi de berg Sam Pieter Mattern Freddy Teunis Rabouw Markus Suta Andries Meijerink debye Institute for Nanomaterials Science Utrecht UniversityPrincetonplein 13584 CC UtrechtThe Netherlands Inorganic Photoactive Materials Heinrich Heine University DüsseldorfUniversitätsstraBe 140225 DüsseldorfGermany

Lanthanide-doped(nano)crystals are an important class of materials in luminescence *** working mechanism of these thermometers is diverse but most often relies on variation of the ratio of emission intensities from two thermally coupled excited states with *** low temperatures,nonradiative coupling between the states can be slow compared to radiative decay,but,at higher temperatures,the two states reach thermal equilibrium due to faster nonradiative *** thermal equilibrium,the intensity ratio follows Boltzmann statistics,which gives a convenient model to calibrate the ***,we investigate multiple strategies to shift the onset of thermal equilibrium to lower temperatures,which enables Boltzmann thermometry in a wider dynamic *** use Eu^(3+)-doped microcrystals as a model system and find that the nonradiative coupling rates increase for host lattices with higher vibrational energies and shorter lanthanide-ligand distances,which reduces the onset temperature of thermal equilibrium by more than 400 *** additionally reveal that thermometers with excited states coupled by electricdipole transitions have lower onset temperatures than those with magnetic-dipole-coupled states due to selection *** insights provide essential guidelines for the optimization of Boltzmann thermometers to operate in an extended temperature range.

关键词： equilibrium excited dynamic

SEPRAN: A Versatile Finite-Element Package for a Wide Variety of Problems in Geosciences

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Journal of Earth Science 2015年第1期26卷 89-95页

作者： Arie van den berg Guus Segal David A.Yuen department of Theoretical Geophysics Institute of Earth SciencesUtrecht University3508 TC UtrechtThe Netherlands Faculty of Electrical Engineering Mathematics and Computer ScienceTU DelftThe Netherlands department of Earth Sciences and Minnesota Supercomputing Institute University of MinnesotaMinneapolis MN 55455USA School of Environmental Studies China University of Geosciences

Numerical modelling of geological processes, such as mantle convection, flow in porous media, and geothermal heat transfer, has become quite common with the increase in computing and the availability of usable software. Today modelling these dynamical processes entails the solving of the governing equations involving the mass, momentum, energy and chemical transport. These equations represent partial differential equations and must be solved on powerful enough computers because they require sufficient spatial and temporal resolution to be useful. We describe here the salient and outstanding features of the SEPRAN software package, developed in the Netherlands, as a case study for a robust and user-friendly soft- ware, which the geological community can utilize in handling many thermal-mechanical-chemical problems found in geology, which will include geothermal situations, where many types of partial differential equations must be solved at the same time with thermodynamical input parameters.

关键词： SEPRAN finite element package geodynamic and planetary modelling geothermal groundwater flow.

What can natural edges of gallery forests teach us about woody community performance in sharp ecotones?

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Journal of Plant Ecology 2017年第6期10卷 937-948页

作者： Gabriela Aparecida de Oliveira Coelho Marcela de Castro Nunes Santos Terra Hisaias de Souza Almeida Eduardo van den berg departamento de Ciências Florestais Universidade Federal de LavrasC.Postal 3037LavrasMG 37200-000Brazil Instituto de Recursos Naturais Universidade Federal de ItajubáC.Postal 50ItajubáMG 37500-903Brazil departamento de Biologia Universidade Federal de LavrasC.Postal 3037LavrasMG 37200-000Brazil

Aims The diversity and structure of forest edges are a central issue in ***,most studies have focused on anthropogenic for-est edges,being natural ones least *** studied the com-munities of shrubs and trees in natural edges of gallery forests with the main goal of learning what are the main factors that shape the structure and diversity of these natural sharp *** We evaluated 10 gallery forest sites,allocating in each of them three 15×20 m *** plots were laid out in relatively rectilinear stretches of forest edges,respecting a minimal distance of 10 m between each *** they are permanent plots and meant to study eventual fluctuations in the forest-grasslands limits,we allocated the plots with their longest side parallel to the forest edge and covering perpendicularly 5 m of the grassland and 10 m of *** the plots we identified,mapped and measured all shrub and tree individuals with diameter at breast height(DBH)≥1 *** Findings Although many differences exist among the communities in terms of density and basal area,all of them were highly dense and had relatively low basal *** addition,both the number of individu-als and the basal area increased rapidly towards the forest *** results also revealed that the edge communities are composed mainly by small individuals that demand a great amount of *** the vertical stratification and the proportion of the functional groups are similar among the sites yet change quickly in the first 10 m of the forest ***,the floristic similarities were low among the communities mainly due to the species turnover within each ***,although the overall structure is constant in the studied edges,the low floristic similarity among them possibly indicates that the species within the same functional groups are sub-stituting each other across the *** older and seemingly stable,our results showed the gallery forest edges are quite simila

关键词： beta diversity edge effects ecotone forest-grassland transition functional groups.

Modeling shoreline sand waves on the coasts of Namibia and Angola

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International Journal of Sediment Research 2013年第3期28卷 338-348页

作者： Francesca RIBAS Albert FALQUES Niels van deN berg Miquel CABALLERIA department of Applied Physics Universitat Politecnica de CatalunyaSpain

The southwestern（SW） coast of Africa（Namibia and Angola） features long sandy beaches and a wave climate dominated by energetic swells from the Southsouthwest（SSW）,therefore approaching the coast with a very high *** images reveal that along that coast there are many shoreline sand waves with wavelengths ranging from 2 to 8 km.A more detailed study,including a Fourier analysis of the shoreline position,yields the wavelengths（among this range） with the highest spectral density ***,it becomes apparent that at least some of the sand waves are dynamically active rather than being controlled by the geological setting.A morphodynamic model is used to test the hypothesis that these sand waves could emerge as free morphodynamic instabilities of the coastline due to the obliquity in wave *** is found that the period of the incident water waves,T;,is crucial to establish the tendency to stability or instability,instability increasing for decreasing period,whilst there is some discrepancy in the observed *** results for T;= 7-8 s clearly show the tendency for the coast to develop free sand waves at about 4 km wavelength within a few years,which migrate to the north at rates of 0.2-0.6 km yr;.For larger T;or steeper profiles,the coast is stable but sand waves originated by other mechanisms can propagate downdrift with little decay.

关键词： Shoreline evolution Shoreline sand waves High angle wave instability Longshore sediment transport