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Modelling of the elastoplastic behaviour of the bio-cemented soils using an extended Modified Cam Clay model

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Journal of Rock Mechanics and Geotechnical Engineering 2024年第6期16卷 2184-2197页

作者： Xuerui wang christian b.Silbermann Thomas Nagel Udo Nackenhorst Institute of Mechanics and Computational Mechanics Leibniz UniversitätHannoverAppelstr.9aHannover30167Germany Gesellschaft für Anlagen-und Reaktorsicherheit(GRS)gGmbH Theodor-Heuss-Straße 4Braunschweig38122Germany Geotechnical Institute Technische Universität BergakademieFreibergGustav-Zeuner-Str.1Freiberg09599Germany

An elastoplastic constitutive model based on the Modified Cam Clay(MCC)model is developed to describe the mechanical behaviour of soils cemented via microbially induced calcite precipitation(MICP).It considers the increase of the elastic stiffness,the change of the yield surface due to MICP cementation and the degradation of calcium carbonate bonds during ***,to capture the typical contraction-dilation transition in MICP soils,the original volumetric hardening rule in the MCC model is modified to a combined deviatoric and volumetric hardening *** model could reproduce a series of drained triaxial tests on MICP-treated soils with different calcium carbonate ***,we carry out a parametric study and observe numerical instability in some *** combination with an analytical analysis,our numerical modelling has identified the benefits and limitations of using MCCbased models in the simulation of MICP-cemented soils,leading to suggestions for further model development.

关键词： Microbially induced calcite precipitation(MICP) Elastoplasticity Modified cam clay(MCC) OpenGeoSys MFront Contraction-dilation transition

Are hyoliths Palaeozoic lophophorates?

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National Science Review 2020年第2期7卷 453-469页

作者： Fan Liu christian b Skovsted Timothy P Topper Zhifei Zhang Degan Shu State Key Laboratory of Continental Dynamics Shaanxi Key Laboratory of Early Life and Environments Department of Geology Northwest University Department of Palaeobiology Swedish Museum of Natural History

The phylogenetic position of hyoliths has long been unsettled, with recent discoveries of a tentaculate feeding apparatus(‘lophophore’) and fleshy apical extensions from the shell(‘pedicle’) suggesting a lophophorate affinity. Here, we describe the first soft parts associated with the feeding apparatus of an orthothecid hyolith, Triplicatella opimus from the Chengjiang biota of South China. The tuft-like arrangement of the tentacles of T. opimus differs from that of hyolithids, suggesting they collected food directly from the substrate. A reassessment of the feeding organ in hyolithids indicates that it does not represent a lophophore and our analysis of the apical structures associated with some orthothecids show that these represent crushed portions of the shell and are not comparable to the brachiopod pedicle. The new information suggests that hyoliths are more likely to be basal members of the lophotrochozoans rather than lophophorates closely linked with the Phylum brachiopoda.

关键词： orthothecid the Chengjiang Lagerst¨atte Cambrian soft parts lophophore

Volume and surface effects on two-photonic and three-photonic processes in dry co-doped upconversion nanocrystals

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Nano Research 2022年第3期15卷 2362-2373页

作者： bettina Grauel christian würth christian Homann Lisa Krukewitt Elina Andresen Janina Roik Sebastian Recknagel Markus Haase Ute Resch-Genger Federal Institute for Materials Research and Testing(bAM) Division 1.2 BiophotonicsRichard-Willstaetter-Str.1112489 BerlinGermany Federal Institute for Materials Research and Testing(bAM) Division 1.6 Inorganic Reference MaterialsRichard-Willstaetter-Str.1112489 BerlinGermany Institute of Chemistry of New Materials Department Biology/ChemistryUniversity OsnabrueckBarbarastr.749076 OsnabrueckGermany Department of Anesthesiology and Intensive Care Medicine University Medical Center RostockSchillingallee 3518057 RostockGermany

Despite considerable advances in synthesizing high-quality core/shell upconversion(UC)nanocrystals(NC;UCNC)and UCNC photophysics,the application of near-infrared(NIR)-excitable lanthanide-doped UCNC in the life and material sciences is still hampered by the relatively low upconversion luminescence(UCL)of UCNC of small size or thin protecting *** obtain deeper insights into energy transfer and surface quenching processes involving Yb^(3+) and Er^(3+) ions,we examined energy loss processes in differently sized solid core NaYF_(4) nanocrystals doped with either Yb^(3+)(YbNC;20%Yb^(3+))or Er^(3+)(ErNC;2%Er^(3+))and co-doped with Yb^(3+) and Er^(3+)(YbErNC;20%Yb^(3+) and 2%Er^(3+))without a surface protection shell and coated with a thin and a thick NaYF_(4) shell in comparison to single and co-doped bulk *** studies at 375 nm excitation demonstrate back-energy transfer(bET)from the ^(4)G_(11/2) state of Er^(3+) to the ^(2)F_(5/2) state of Yb^(3+),through which the red Er^(3+) ^(4)F_(9/2) state is efficiently *** power density(P)-dependent steady state and time-resolved photoluminescence measurements at different excitation and emission wavelengths enable to separate surface-related and volume-related effects for two-photonic and three-photonic processes involved in UCL and indicate a different influence of surface passivation on the green and red Er3+*** intensity and lifetime of the latter respond particularly to an increase in volume of the active UCNC *** provide a three-dimensional random walk model to describe these effects that can be used in the future to predict the UCL behavior of UCNC.

关键词： upconversion luminescence core/shell nanoparticles dopant concentration lifetime volume effect surface quenching

Particle-size-dependent upconversion luminescence of NaYF4:Yb,Er nanoparticles in organic solvents and water at different excitation power densities

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Nano Research 2018年第12期11卷 6360-6374页

作者： Marco Kraft christian würth Verena Muhr Thomas Hirsch Ute Resch-Genger Federal Institute for Matefiab Research and Testing (bAM) Division1.2BiophotonicsRichard-Willstaetter-Str.1112489BerlinGermany Institute of Analytical Chemistry Chemo-and BiosensorsUniversity of Regensburg93040RegensburgGermany

A systematic study of the luminescence properties of monodisperse β-NaYF4: 20% Yb3+, 2% Er3+ upconversion nanoparticles (UCNPs) with sizes ranging from 12–43 nm is presented utilizing steady-state and time-resolved fluorometry. Special emphasis was dedicated to the absolute quantification of size- and environment-induced quenching of upconversion luminescence (UCL) by high-energy O–H and C–H vibrations from solvent and ligand molecules at different excitation power densities (P). In this context, the still-debated population pathways of the 4F9/2 energy level of Er3+ were examined. Our results highlight the potential of particle size and P value for color tuning based on the pronounced near-infrared emission of 12 nm UCNPs, which outweighs the red Er3+ emission under “strongly quenched” conditions and accounts for over 50% of total UCL in water. because current rate equation models do not include such emissions, the suitability of these models for accurately simulating all (de)population pathways of small UCNPs must be critically assessed. Furthermore, we postulate population pathways for the 4F9/2 energy level of Er3+, which correlate with the size-, environment-, and P-dependent quenching states of the higher Er3+ energy levels.

关键词： upconversion nanoparticle quenching diameter water cyclohexane

Avoiding experimental bias by systematic antibody validation

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Neural Regeneration Research 2016年第7期11卷 1079-1080页

作者： Sara b.Jager christian bjerggaard Vaegter Department of biomedicine & DANDRITE-Danish Research Institute of Translational Neuroscience Aarhus University

Antibodies are valued reagents in most modern laboratories and indispensable for many *** can be utilized in a wide range of experimental setups designed to elucidate various scientific *** our laboratory,antibodies a... 详细信息

关键词： indispensable questions furthermore utilized elucidate localization validation laboratories necessity giving

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Elective thoracotomy for pedicle screw removal to prevent severe aortic bleeding

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world Journal of Clinical Cases 2014年第4期2卷 100-103页

作者： Sebastian Decker Mohamed Omar christian Krettek christian w Müller Trauma Department Hannover Medical School30625 Hannover Germany

we present a case of a 33-year-old female who sustained multiple injuries of her spine, including spinous process fractures of C5 to C7 and a lamina fracture of C6 and C7. Her thoracic spine showed transverse process fractures of T4 to T10, a compression fracture and lamina fracture of T3, spinous process and transverse process fractures of T4 and T5, a rotation injury of T6, as well as a compression fracture of L1. Thirteen months after posterior thoracic spinal instrumentation, a pedicle screw was suspected to be in contact with the aorta, which was proved by computed tomography angiograms. Consequently, implant removal was planned with direct exposure of the aorta in order to allow for immediate repair if needed. So far, studies that compare different techniques to remove pedicle screws that are suspected to penetrate the aorta are missing. However, different techniques have been described in case reports, mainly minimally invasive endovascular techniques vs open techniques such as thoracotomy.

关键词： Spine Pedicle screw Aorta bleeding Implant removal Hemorrhage

Schrodinger and Klein-Gordon theories of black holes from the quantization of the Oppenheimer and Snyder gravitational collapse

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Communications in Theoretical Physics 2023年第9期75卷 122-135页

作者： christian Corda SUNY Polytechnic Institute 13502 UticaNew YorkUSAIstituto Livi59100 PratoTuscanyItaly and International Institute for Applicable Mathematics and Information SciencesB M Birla Science CentreAdarshnagarHyderabad 500063India

The Schrodinger equation of the Schwarzschild black hole(bH) has been recently derived by the author and collaborators. The bH is composed of a particle, the 'electron', interacting with a central field, the 'nucleus'. Via de broglie's hypothesis, one interprets the 'electron' in terms of bH horizon's modes. Quantum gravity effects modify the bH semi-classical structure at the Schwarzschild scale rather than at the Planck scale. The analogy between this bH Schrodinger equation and the Schrodinger equation of the s states of the hydrogen atom permits us to solve the same equation. The quantum gravitational quantities analogous of the fine structure constant and of the Rydberg constant are not constants, but the dynamical quantities have well-defined discrete spectra. The spectrum of the 'gravitational fine structure constant' is the set of non-zero natural numbers. Therefore, bHs are well-defined quantum gravitational systems obeying Schrodinger's theory: the 'gravitational hydrogen atoms'. by identifying the potential energy in the bH Schrodinger equation as being the gravitational energy of a spherically symmetric shell, a different nature of the quantum bH seems to surface. bHs are self-interacting, highly excited,spherically symmetric, massive quantum shells generated by matter condensing on the apparent horizon, concretely realizing the membrane paradigm. The quantum bH described as a'gravitational hydrogen atom' is a fictitious mathematical representation of the real, quantum bH, a quantum massive shell having a radius equal to the oscillating gravitational *** consequences emerge from this result:(i) bHs have neither horizons nor singularities;(ii) there is neither information loss in bH evaporation, nor bH complementarity, nor firewall paradox. These results are consistent with previous ones by Hawking, Vaz, Mitra and ***, the special relativistic corrections to the bH Schrodinger equation give the bH Klein–Gordon equation and the cor

关键词： quantum black holes information paradox quantum shells quantum levels Schrodinger and Klein-Gordon theories

Methylprednisolone for acute spinal cord injury: an increasingly philosophical debate

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Neural Regeneration Research 2016年第6期11卷 882-885页

作者： christian A.bowers bornali Kundu Gregory w.J.Hawryluk Department of Neurosurgery Clinical Neurosciences Center University of Utah

Following publication of NASCIS Ⅱ, methylprednisolone sodium succinate（MPSS） was hailed as a breakthrough for patients with acute spinal cord injury（SCI）. MPSS use for SCI has since become very controversial and it is our opinion that additional evidence is unlikely to break the stalemate amongst clinicians. Patient opinion has the potential to break this stalemate and we review our recent findings which reported that spinal cord injured patients informed of the risks and benefits of MPSS reported a preference for MPSS administration. we discuss the implications of the current MPSS debate on translational research and seek to address some misconceptions which have evolved. As science has failed to resolve the MPSS debate we argue that the debate is an increasingly philosophical one. we question whether SCI might be viewed as a serious condition like cancer where serious side effects of therapeutics are tolerated even when benefits may be small. we also draw attention to the similarity between the side effects of MPSS and isotretinoin which is prescribed for the cosmetic disorder acne vulgaris. Ultimately we question how patient autonomy should be weighed in the context of current SCI guidelines and MPSS＇s status as a historical standard of care.

关键词： debate autonomy opinion argue break informed administration translational historical preference

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相变中的界面(英文)

金属学报 1997年第2期33卷 150-156页

作者： J.w.christian DepartmentofMaterials OxfordUniversityParksRoadOxfordOX13PHUK

讨论了各类相变中的界面分类．重构型相变没有共格界面，相变产物形状也无系统性变化．位移型相变有完全共格或部份共格的界面，有可见的相变产物形状变化．完全共格界面出现在无成分变化的马氏体型相变以及有成分变化的扩散位移型相变... 详细信息

讨论了各类相变中的界面分类．重构型相变没有共格界面，相变产物形状也无系统性变化．位移型相变有完全共格或部份共格的界面，有可见的相变产物形状变化．完全共格界面出现在无成分变化的马氏体型相变以及有成分变化的扩散位移型相变中．这二种类型界面的迁移依靠台阶（马氏体相变中称之谓相变位错）的运动完成．部分共格界面也可能出现在马氏体型或较为少见的扩散型相变中．

关键词：界面马氏体相变贝氏体

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