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CONVEXITY AND BERNSTEIN POLYNOMIALS ON k-SIMPLOIDS

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Acta Mathematicae Applicatae Sinica 1990年第1期6卷 50-66页

作者： wolfgang dahmen CHARLES A.MICCHELLI Institut fur Mathematik Ⅲ Freie Universitat Berlin Arnimallee 2-61000 Berlin(West)33GermanyIBM T.J.Watson Research CenterP.O.Box 218Yorktown HeightsN.Y.10598U.S.A.

This paper is concerned with Bernstein polynomials on k-simploids by which we mean a crossproduct of k lower dimensional simplices. Specifically, we show that if the Bernstein polynomials ofa given function f on a k-simploid form a decreasing sequence then f+l, where l is any correspondingtensor product of affine functions. achieves its maximum on the boundary of the k-simploid. Thisextends recent results in [1] for bivariate Bernstein polynomials on triangles. Unlike the approachused in [1] our approach is based on semigroup techniques and the maximum principle for secondorder elliptic operators. Furthermore, we derive analogous results for cube spline surfaces.

关键词： Bernstein 多项式凸性

Multilevel Preconditioners for the Interior Penalty Discontinuous Galerkin Method II-Quantitative Studies

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Communications in Computational Physics 2009年第2期5卷 296-325页

作者： Kolja Brix Martin Campos Pinto wolfgang dahmen Ralf Massjung Institut fur Geometrie und Praktische Mathematik RWTH Aachen52056 AachenGermany Universite Louis Pasteur Institut de Recherche Mathematique AvanceeCNRS UMR 750167084 StrasbourgFrance

This paper is concerned with preconditioners for interior penalty discontinuous Galerkin discretizations of second-order elliptic boundary value *** extend earlier related results in[7]in the following *** concrete realizations of splitting the nonconforming trial spaces into a conforming and(remaining)nonconforming part are identified and shown to give rise to uniformly bounded condition *** asymptotic results are complemented by numerical tests that shed some light on their respective quantitative behavior.

关键词： Interior penalty method energy-stable splittings admissible averaging operators frames multilevel Schwarz preconditioners discontinuous Galerkin methods

Universality of slip avalanches in a ductile Fe-based bulk metallic glass

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Journal of Iron and Steel Research International 2017年第4期24卷 366-371页

作者： Jiao-jiao Li Jun-wei Qiao Karin A.dahmen Wei-ming Yang Bao-long Shen Ming-wei Chen Laboratory of Applied Physics and Mechanics of Advanced Materials College of Materials Science and EngineeringTaiyuan University of TechnologyTaiyuan 030024ShanxiChina Key Laboratory of Interface Science and Engineering in Advanced Materials Ministry of EducationTaiyuan University of TechnologyTaiyuan 030024ShanxiChina Department of Physics University of Illinois at Urbana-ChampaignIllinois 61801USA State Key Laboratory for Geomechanics and Deep Underground Engineering School of Mechanics and Civil EngineeringChina University of Mining and TechnologyXuzhou 221116JiangsuChina School of Materials Science and Engineering Southeast UniversityNanjing 211189JiangsuChina Advanced Institute for Materials Research Tohoku UniversitySendal 980-8577Japan

Intermittent serrated flows of a novel ductile Fe60Ni20P13C7 bulk metallic glass（BMG）at variant strain rates were investigated by statistics *** and clutter distribution of slip-avalanche magnitudes are displayed during stable plastic flows at strain rates of 2×10-4 s-1 and 5×10-5 s-1,respectively,which means that serration behavior depends on the strain ***,the remarkable agreement between measured slip-avalanche magnitudes and the scaling behavior,i.e.a universal complementary cumulative distribution function（CCDF）predicted by mean-field theory（MFT）model,indicates that the plasticity of the present Fe-based BMGs can be tuned by imposed strain rates：Smax^6）ε-λ.This tuned plasticity is elucidated with expended free-volume ***,the scaling behavior of serrated flows for other strain rates can be predicted as well.

关键词： Bulk metallic glass Slip avalanche Plasticity Mean-field theory model Strain rate

Induction of chronic cholestasis without liver cirrhosis-Creation of an animal model

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World Journal of Gastroenterology 2017年第23期23卷 4191-4199页

作者： Felix Dondorf RenéFahrner Michael Ardelt Eleonora Patsenker Felix Stickel Uta dahmen Utz Settmacher Falk Rauchfuβ Department of General Visceral and Vascular SurgeryJena University Hospital Division of Gastroenterology and Hepatology University Hospital Zürich

To analyze time intervals of inflammation and regeneration in a cholestatic rat liver *** 36 Lewis rats, divided into six groups of 6 animals (postoperative observation periods: 1, 2, 3, 4, 6, 8 wk), the main bile duct was ligated with two ligatures and observed for the periods mentioned above. For laboratory evaluation, cholestasis parameters (bilirubin, γ-GT), liver cell parameters (ASAT, ALAT) and liver synthesis parameters (quick, albumin) were determined. For histological analysis, HE, EvG, ASDCL and HMGB-1 stainings were performed. Furthermore, we used the mRNA of IL-33, GADD45a and p-21 for analyzing cellular stress and regeneration in cholestatic *** chemical laboratory and histological evaluation, a distinction between acute and chronic cholestatic liver injury with identification of inflammation and regeneration could be demonstrated by an increase in cholestasis (bilirubin: 1-wk group, 156.83 ± 34.12 μmol/L, P = 0.004) and liver cell parameters (ASAT: 2-wk group, 2.1 ± 2.19 μmol/L.s, P = 0.03; ALAT: 2-wk group, 1.03 ± 0.38 μmol/L.s, P = 0.03) after bile duct ligation (BDL). Histological evaluation showed an increase of bile ducts per portal field (3-wk group, 48 ± 6.13, P = 0.004) during the first four weeks after bile duct ligation. In addition to inflammation, which is an expression of acute cholestasis, there was an increase of necrotic areas in the histological sections (2-wk group, 1.38% ± 2.28% per slide, P = 0.002). Furthermore, the inflammation could be verified by ASDCL (4-wk group, 22 ± 5.93 positive cells per portal field, P = 0.041) and HMGB-1 [2-wk group, 13 ± 8.18 positive cells per field of view (FoV), P = 0.065] staining. Therefore, in summary of the laboratory evaluation and histological studies, acute cholestasis could be found during the first four weeks after bile duct ligation. Subsequently, the described parameters declined so that chronic cholestasis could be assumed. For quantification of secondary biliary ci

关键词： Rats Cholestasis Chronic cholestasis Rat liver model

Plasticity performance of Al_(0.5)CoCrCuFeNi high-entropy alloys under nanoindentation

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Journal of Iron and Steel Research International 2017年第4期24卷 390-396页

作者： Li-ping Yu Shu-ying Chen Jing-li Ren Yang Ren Fu-qian Yang Karin A.dahmen Peter K.Liaw School of Mathematics and Statistics Zhengzhou University Department of Materials Science and Engineering The University of Tennessee State Key Laboratory of Nonlinear Mechanics Institute of MechanicsCAS X-ray Science Division Argonne National Laboratory Department of Chemical and Materials Engineering University of Kentucky Department of Physics University of Illinois at Urbana-Champaign

The statistical and dynamic behaviors of the displacement-load curves of a high-entropy alloy,Al_（0.5）CoCrCuFeNi,were analyzed for the nanoindentation performed at two *** behavior of serrations at room temperature and chaotic flows at 200°C were *** results are attributed to the interaction among a large number of slip *** the nanoindentation at room temperature,recurrent partial events between slip bands introduce a hierarchy of length scales,leading to a critical *** the nanoindentation at 200°C,there is no spatial interference between two slip bands,which is corresponding to the evolution of separated trajectory of chaotic behavior.

关键词： High-entropy alloys Nanoindentation Critical behavior Chaotic behavior

Clinical efficacy of the Ankle Spacer for the treatment of multiple secondary osteochondral lesions of the talus

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World Journal of Orthopedics 2022年第2期13卷 178-192页

作者： Jari dahmen J Nienke Altink Gwendolyn Vuurberg Coen A Wijdicks Sjoerd AS Stufkens Gino MMJ Kerkhoffs Department of Orthopedic Surgery Amsterdam UMCLocation AMCAmsterdam 1105AZNetherlands Department of Orthopedic Research ArthrexNaplesFL 34108United States

BACKGROUND The Ankle Spacer was developed as a joint-sparing alternative to invasive endstage ***,there are no clinical studies on the Ankle *** To describe the operative technique and the clinical efficacy of the Ankle Spacer for the treatment of multiple,cystic osteochondral lesions of the talus in patients with failed prior operative *** This is a prospective study during which patients were assessed preoperatively,at 2-and 6 wk,and at 3,6,12 and 24 mo *** with multiple,cystic or large(≥15 mm)osteochondral lesions of the talus after failed prior surgery were *** primary outcome measure was the numeric rating scale(NRS)for pain during walking at 2 years *** outcome measures included the NRS in rest and during stair climbing,the American Orthopaedic Foot and Ankle Society Hindfoot Score,the Foot and Ankle Outcome Score,the Short-Form 36 physical and mental component scale,and the Range of Motion(ROM).Radiographic evaluations were conducted to evaluate prosthetic loosening and *** rates and complications were also *** Two patients underwent an Ankle Spacer implantation on the *** NRS during walking improved from 6 and 7 preoperatively to 2 and 2 points postoperatively at 2 years,in patient 1 and 2,*** other patient-reported outcome measures also improved *** were no re-operations nor *** imaging showed no loosening of the implant and no change of implant *** The Ankle Spacer showed clinically relevant pain reduction during walking,improvement in clinical outcomes as assessed with PROMs,and no complications or *** treatment option may evolve as a joint-sparing alternative to invasive end-stage surgeries.

关键词： Hemi-arthroplasty Ankle Spacer Talar surface implant Osteochondral lesions of the talus Endstage

Towards Automated Robot-Based Nanohandling

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Towards Automated Robot-Based Nanohandling

Does granulocyte-colony stimulating factor administration induce damage or repair response in schistosomiasis?

2009中国控制与决策会议

作者： Fatikow S. Wortmann T. Mikczinski M. dahmen C. Stolle C. Division Microrobotics and Control Engineering（AMiR） University of OldenburgGermany

ISBN: (纸本)9781424427239

＜正＞One of the key challenges of microsystem- and nanotechnologies is the automation of robot-based nanomanipulation. However,there is limited sensor feedback due to lack of appropriate *** feedback is required for repeatable actuator movements from macro- down to the *** complicates the design of reliable automation *** this paper,the development of an automated robot-based toolbox for cell injection and handling is presented. This toolbox includes several sensor methods,bridging several orders of magnitude as feedback for automation. A non-linear support vector machine（SVM） is applied for classification of the viability of cells as feedback for quality control.A visual servoing algorithm for position tracking of the injection needle as well as an injection force sensor have been *** automation results and the control system are explained.

关键词： Nanohandling cell classification visual servoing force-sensing distributed control architecture

来源： cnki会议评论

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World Journal of Hepatology 2010年第12期2卷 434-441页

作者： Lobna Y Ghanem Uta dahmen Olaf Dirsch Mona MF Nosseir Soheir S Mahmoud Wafaa AF Mansour Department of Electron Microscope Theodor Bilharz Research Institute Department of General Visceral and Transplantation SurgeryUniversity Hospital Essen Division of Pathology German Heart Institute Department of Pathology Theodor Bilharz Research Institute Department of Parasitology Theodor Bilharz Research Institute Department of Immunology Theodor Bilharz Research Institute

AIM:To introduce Granulocyte-colony stimulating factor (G-CSF) as a new therapeutic modality for schistosomiasis through stem cell mobilization,immunomodulation or fibrosis remodeling. METHODS:In this study,a 5 d course of human recombinant G-CSF (100 μg/kg sc) was applied to Schis-tosoma mansoni-infected mice at different stages of disease (5 d before infection as well as 3,5 and 7 wk post-infection). The animals were sacrificed at 10 d as well as 4,6 and 8 wk post infection. Mice were examined for:(1) Total leukocyte count which is an accepted surrogate marker for the stem cell mobilization into the circulation; (2) Egg count in intestine and liver tissue to assess the parasitic load; and (3) Histopathological changes in Hx/E and Masson trichrome stained sections as well as collagen content in Sirius redstained liver sections to determine the severity of liver fibrosis. RESULTS:Mice developed leukocytosis. The egg load and the number of granulomas were not affected by the G-CSF treatment but there was an obvious change in the composition of granulomas towards an increased cellularity. Moreover,fibrosis was significantly decreased in treated groups compared to untreated animals (collagen content either preinfection or at 3 and 5 wk post infection:5.8 ± 0.5,4.7 ± 0.5,4.0 ± 0.7 vs 8.2 ± 0.9; P ≤ 0.01). CONCLUSION:Although G-CSF did not cause direct elimination of the parasite,it enhanced granulomatous reaction and reduced the fibrosis. Further investigation of the underlying mechanisms of these two actions is warranted.

关键词： Schistosomiasis Granulocyte-colony stimulating factor Periovular granuloma Fibrosis Immunomodulation Stem cell mobilization

Fatigue behavior of high-entropy alloys： A review

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Science China(Technological Sciences) 2018年第2期61卷 168-178页

作者： CHEN PeiYong LEE Chanho WANG Shao-Yu SEIFI Mohsen LEWANDOWSKI John J dahmen Karin A JIA HaoLing XIE Xie CHEN BiLin YEH Jien-Wei TSAI Che-Wei YUAN Tao LIAW Peter K Department of Materials Science and Engineering The University of TennesseeKnoxville 37996，USA Department of Materials Science and Engineering Case Western UniversityCleveland 44106USA Department of Physics University of IllinoisUrbana 61801USA Department of Materials Science and Engineering 'National' Tsing Hua UniversityHsinchu 30013，Taiwan，China Department of Industry and System Engineering Ohio UniversityAthens 45701，USA

Fatigue failures cost approximately 4% of the United States' gross domestic product(GDP). The design of highly fatigue-resistant materials is always in demand. Different from conventional strategies of alloy design, high-entropy alloys(HEAs) are defined as materials with five or more principal elements, which could be solid solutions. This locally-disordered structure is expected to lead to unique fatigue-resistant properties. In this review, the studies of the fatigue behavior of HEAs during the last five years are summarized. The four-point-bending high-cycle fatigue coupled with statistical modelling, and the fatigue-crack-growth behavior of HEAs, are reviewed. The effects of sample defects and nanotwins-deformation mechanisms on four-point-bending high-cycle fatigue of HEAs are discussed in detail. The influence of stress ratio and temperature on fatigue-crack-growth characteristics of HEAs is also discussed. HEAs could exhibit comparable or greater fatigue properties, relative to conventional materials. Finally,the possible future work regarding the fatigue behavior of HEAs is suggested.

关键词： high-entropy alloys fatigue behaviour statistical modelling fatigue crack growth