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Effects of Mn content on recrystallization resistance of AA6082 aluminum alloys during post-deformation annealing

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Journal of Materials Science & Technology 2020年第17期52卷 189-197页

作者： Xiaoming Qian nick Parson X.-Grant Chen Department of Applied Science University of Quebec at ChicoutimiSaguenay G7H 2B1Canada Arvida Research and Development Centre Rio Tinto AluminumSaguenay G7S 4K8Canada

The microstructural evolutions under as-homogenized and as-deformed conditions and after the postdeformation annealing of AA6082 aluminum alloys with different Mn content(0.05 wt.%-1 wt.%)were studied by optical,scanning electron,and transmission electron *** results showed that the presence of a large amount ofα-Al(Mn,Fe)Si dispersoids induced by Mn addition significantly improved the recrystallization *** the base alloy free of Mn,static recrystallization occurred after 2 h of annealing,and grain growth commenced after 4 h of annealing,whereas in Mn-containing alloys,the recovered grain structure was well-retained after even 8 h of *** alloy with 0.5%Mn exhibited the best recrystallization resistance,and a further increase of the Mn levels to 1%resulted in a gradual reduction of the recrystallization resistance,the reason for which was that recrystallization occurred only in the dispersoid-free zones(DFZs)and the increased DFZ fraction with Mn content led to an increase in the recrystallization *** variation in the dispersoid number density and a coarsening of dispersoids during annealing have a limited influence on the static recrystallization in Mn-containing alloys.

关键词： AA6082 alloys Mn effects Recrystallization resistance Dispersoid precipitation Post-deformation annealing

An approximate nonlinear modified Mohr-Coulomb shear strength criterion with critical state for intact rocks

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Journal of Rock Mechanics and Geotechnical Engineering 2018年第4期10卷 645-652页

作者： Baotang Shen Jingyu Shi nick Barton State Key Laboratory of Mining Disaster Prevention and Control Shandong University of Science and TechnologyQingdaoChina CSIRO Energy QCAT1 Technology CourtPullenvaleQLD4069Australia nick Barton&Associates OsloNorway

In this paper, the Mohr-Coulomb shear strength criterion is modified by mobilising the cohesion and internal friction angle with normal stress, in order to capture the nonlinearity and critical state concept for intact rocks reported in the literature. The mathematical expression for the strength is the same as the classical form, but the terms of cohesion and internal friction angle depend on the normal stress now,leading to a nonlinear relationship between the strength and normal stress. It covers both the tension and compression regions with different expressions for cohesion and internal friction angle. The strengths from the two regions join continuously at the transition of zero normal stress. The part in the compression region approximately satisfies the conditions of critical state, where the maximum shear strength is reached. Due to the nonlinearity, the classical simple relationship between the parameters of cohesion, internal friction angle and uniaxial compressive strength from the linear Mohr-Coulomb criterion does not hold anymore. The equation for determining one of the three parameters in terms of the other two is supplied. This equation is nonlinear and thus a nonlinear equation solver is needed. For simplicity, the classical linear relationship is used as a local approximation. The approximate modified Mohr-Coulomb criterion has been implemented in a fracture mechanics based numerical code FRACOD,and an example case of deep tunnel failure is presented to demonstrate the difference between the original and modified Mohr-Coulomb criteria. It is shown that the nonlinear modified Mohr-Coulomb criterion predicts somewhat deeper and more intensive fracturing regions in the surrounding rock mass than the original linear Mohr-Coulomb criterion. A more comprehensive piecewise nonlinear shear strength criterion is also included in Appendix B for those readers who are interested. It covers the tensile, compressive, brittle-ductile behaviour transition and the

关键词： Shear strength Modified Mohr-Coulomb criterion Critical state Intact rock

Dynamic Actin Controls Polarity Induction de novo in Protoplasts

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Journal of Integrative Plant Biology 2013年第2期55卷 142-159页

作者： Beatrix Zaban Jan Maisch Peter nick Botanical Institute Molecular Cell Biology Karlsruhe Institute of Technology

Cell polarity and axes are central for plant morphogenesis. To study how polarity and axes are induced de novo, we investigated protoplasts of tobacco Nicotiana tabacum cv. BY-2 expressing fluorescently- tagged cytoskeletal markers. We standardized the system to such a degree that we were able to generate quantitative data on the temporal patterns of regeneration stages. The synthesis of a new cell wall marks the transition to the first stage of regeneration, and proceeds after a long preparatory phase within a few minutes. During this preparatory phase, the nucleus migrates actively, and cytoplasmic strands remodel vigorously. We probed this system for the effect of anti-cytoskeletal compounds, inducible bundling of actin, RGD-peptides, and temperature. Suppression of actin dynamics at an early stage leads to aberrant tripolar cells, whereas suppression of microtubule dynamics produces aberrant sausage- like cells with asymmetric cell walls. We integrated these data into a model, where the microtubular cytoskeleton conveys positional information between the nucleus and the membrane controlling the release or activation of components required for cell wall synthesis. Cell wall formation is followed by the induction of a new cell pole requiring dynamic actin filaments, and the new cell axis is manifested as elongation growth perpendicular to the orientation of the aligned cortical microtubules.

关键词： Actin axis formation microtubules polarity induction tobacco BY-2 protoplasts.

Break of symmetry in regenerating tobacco protoplasts is independent of nuclear positioning

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Journal of Integrative Plant Biology 2016年第9期58卷 799-812页

作者： Linda Brochhausen Jan Maisch Peter nick Molecular Cell Biology Botanical Institute Karlsruhe Institute of Technology Katserstr. 2 D-76133 Karlsruhe Germany

Nuclear migration and positioning are crucial for the morphogenesis of plant cells. We addressed the potential role of nuclear positioning for polarity induction using an experimental system based on regenerating protoplasts, where the induction of a cell axis de novo can be followed by quantification of specific regeneration stages. Using overexpression of fluorescently tagged extranuclear （perinu- clear actin basket, kinesins with a calponin homology domain （KCH）） as well as intranuclear （histone H2B） factors of nuclear positioning and time-lapse series of the early stages of regeneration, we found that nuclear position is no prerequi- site for polarity formation. However, polarity formation and nuclear migration were both modulated in the transgenic lines, indicating that both phenomena depend on factors affecting cytoskeletal tensegrity and chromatin structure. We integrated these findings into a model where retrograde signals are required for polarity induction. These signals travel via the cytoskeleton from the nucleus toward targets at the plasma membrane.

关键词： Axis formation cytoskeleton nuclear migration polarity induction tobacco BY-2 protoplast

Emphysematous Cystitis: Report of Two Cases and Review of the Literature

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Health 2024年第4期16卷 309-318页

作者： Roland Bertile Banga-Mouss Nestor Ghislain Andzouana Mbamognoua Yanick Dimi Nyanga Armel Melvin Atipo Ondongo Steve Aristid Ondziel-Opara Raïssa Laure Mayanda Ohouanda nick Arnaud Monabeka Evariste Bouenizabila Anani Séverin Wences Odzébé Prosper Alain Bouya Urology Department University Hospital of Brazzaville Brazzaville Republic of the Congo Faculty of Health Sciences Marien Ngouabi University Brazzaville Republic of the Congo Department of Metabolic and Endocrine Diseases University Hospital of Brazzaville Brazzaville Republic of the Congo

Emphysematous cystitis is a rare complication of lower urinary tract infection whose prognosis is conditioned by the delay in treatment. The predisposition of diabetic patients to urinary infections caused by gas-producing bacteria is considered one of the most common factors in the occurrence of emphysematous cystitis. The currently recommended diagnostic test is CT scanning, which has definite value in assessing gas accumulation in the bladder wall and lumen. The authors report the observations of two patients aged 68 and 80 who were treated for emphysematous cystitis complicating diabetes mellitus. The evolution was favorable under treatment with antibiotic therapy, insulin therapy and bladder drainage.

关键词： Emphysematous Cystitis Computed Tomography Lower Urinary Tract Infection Diabetes Mellitus

Nonlinear shear behavior of rock joints using a linearized implementation of the Barton-Bandis model

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Journal of Rock Mechanics and Geotechnical Engineering 2017年第4期9卷 671-682页

作者： Simon Heru Prassetyo Marte Gutierrez nick Barton Department of Civil and Environmental Engineering Colorado School of Mines Golden CO 80401 USA nick Barton and Associates Oslo Norway

Experiments on rock joint behaviors have shown that joint surface roughness is mobilized under shearing,inducing dilation and resulting in nonlinear joint shear strength and shear stress *** displacement *** Barton-Bandis(B-B) joint model provides the most realistic prediction for the nonlinear shear behavior of rock *** B-B model accounts for asperity roughness and strength through the joint roughness coefficient(JRC) and joint wall compressive strength(JCS) ***,many computer codes for rock engineering analysis still use the constant shear strength parameters from the linear Mohr-Coulomb(M-C) model,which is only appropriate for smooth and non-dilatant *** limitation prevents fractured rock models from capturing the nonlinearity of joint shear *** bridge the B-B and the M C models,this paper aims to provide a linearized implementation of the B-B model using a tangential technique to obtain the equivalent M-C parameters that can satisfy the nonlinear shear behavior of rock *** equivalent parameters,namely the equivalent peak cohesion,friction angle,and dilation angle,are then converted into their mobilized forms to account for the mobilization and degradation of JRC under *** conversion is done by expressing JRC in the equivalent peak parameters as functions of joint shear displacement using proposed hyperbolic and logarithmic functions at the pre-and post-peak regions of shear displacement,***,the pre-and post-peak joint shear stiffnesses are derived so that a complete shear stress-shear displacement relationship can be *** of the linearized implementation of the B-B model show that the shear stress-shear displacement curves,the dilation behavior,and the shear strength envelopes of rock joints are consistent with available experimental and numerical results.

关键词： Rock joints Joint shear behavior Friction and dilation Barton-Bandis(B-B) model Equivalent Mohr-Coulomb(M-C) parameters

Analysis of blasting damage in adjacent mining excavations

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Journal of Rock Mechanics and Geotechnical Engineering 2015年第3期7卷 282-290页

作者： nick Yugo Woo Shin Yukon Zinc Corporation

Following a small-scale wedge failure at Yukon Zinc＇s Wolverine Mine in Yukon, Canada, a vibration monitoring program was added to the existing rockbolt pull testing regime. The failure in the 1150 drift occurred after numerous successive blasts in an adjacent tunnel had loosened friction bolts passing through an unmapped fault. Analysis of blasting vibration revealed that support integrity is not compromised unless there is a geological structure to act as a failure plane. The peak particle velocity（PPV） rarely exceeded 250 mm/s with a frequency larger than 50 Hz. As expected, blasting more competent rock resulted in higher PPVs. In such cases, reducing the round length from 3.5 m to 2.0 m was an effective means of limiting potential rock mass and support damage.

关键词： Blasting damage Vibration monitoring Adjacent tunnel development Dynamic loading of friction bolts Jinduicheng Molybdenum Wolver

Management of complicated acute appendicitis in children:Still an existing controversy

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World Journal of Gastrointestinal Surgery 2020年第4期12卷 129-137页

作者： nick Zavras George Vaos Department of Paediatric Surgery “ATTIKON”University General HospitalNational and Kapodistrian University of AthensSchool of MedicineAthens 12462Greece

Complicated acute appendicitis(CAA)is a serious condition and carries significant morbidity in children.A strict diagnosis is challenging,as there are many lesions that mimic *** management of CAA is still *** are two options for treatment:Immediate operative management and nonoperative management with antibiotics and/or drainage of any abscess or *** method of treatment has advantages and *** management may be difficult due to the presence of inflamed tissues and may lead to detrimental *** many cases,non-operative management with or without drainage and interval appendectomy is *** reasons for this approach include new medications and policies for the use of antibiotic ***,advances in radiological interventions may overcome difficulties such as diagnosing and managing the complications of CAA without any ***,questions have been raised about the risk of recurrence,prolonged use of antibiotics,lengthened hospital stay and delay in returning to daily ***,the need for interval appendectomy is currently under debate because of the low risk of *** to the paucity of high-quality studies,more randomized controlled trials to determine the precise management strategy are *** review aims to study the current data on operative vs non-operative management for CAA in children and to extract any useful information from the literature.

关键词： Complicated acute appendicitis Operative treatment Non-operative treatment Antibiotics Children

Using Twitter Bios to Measure Changes in Self-Identity:Are Americans Defining Themselves More Politically Over Time?

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Journal of Social Computing 2021年第1期2卷 1-13页

作者： nick Rogers Jason J.Jones Department of Sociology Stony Brook UniversityStony BrookNY 11794USA

Are Americans weaving their political views more tightly into the fabric of their self-identity over time?If so,then we might expect partisan disagreements to continue becoming more emotional,tribal,and *** recent scholarship has speculated that this politicization of Americans’identity is occurring,but there has been little compelling attempt to quantify the phenomenon,largely because the concept of identity is notoriously difficult to *** introduce here a methodology,Longitudinal Online Profile Sampling(LOPS),which affords quantifiable insights into the way individuals amend their identity over *** this method,we analyze millions of“bios”on the microblogging site Twitter over a 4-year span,and conclude that the average American user is increasingly integrating politics into their social *** on the site are adding political words to their bios at a higher rate than any other category of words we measured,and are now more likely to describe themselves by their political affiliation than their religious *** data suggest that this is due to both cohort and individual-level effects.

关键词： identity social identity theory social media ideology political polarization Twitter