bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of risk factors for obstetric outcomes after hysteroscopic adhesiolysis for Asherman syndrome: A retrospective cohort study
Authors: Zhang Yuxue , Zhu Xiaohong , Zhang Tengfei , Zhang Yanling , Zhang Mengsi , Lin Xiaona
Published: January 2021

Objective

To investigate the factors influencing placenta accreta in pregnant women who previously underwent hysteroscopic adhesiolysis (HA).

Methods

This retrospective study enrolled 265 women with intrauterine adhesions (IUAs) at the Sir Run Run Shaw Hospital from January 2014 to December 2018. We followed up their pregnancy outcomes and maternal complications.

Results

The menstrual pattern and gestational history before operation were significantly different between the live birth and pregnancy loss groups. The age, extent of cavity involved, type of adhesions, times of adhesiolysis performed, and time interval from surgery to pregnancy were not significantly different between these two groups. In the third trimester, 48 of 140 patients had 53 perinatal complications, including placenta accreta (27), gestational diabetes mellitus (10), pregnancy‐induced hypertension (6), postpartum hemorrhage (4), intrahepatic cholestasis of pregnancy (2), placenta previa (1), oligohydramnios (1), and intrauterine growth restriction (1). Logistic regression analysis showed that extent of cavity involved and times of adhesiolysis performed were associated with placenta accreta.

Conclusion

The extent of cavity involved and times of adhesive separation surgeries were risk factors for placenta accreta in patients. The menstrual model and gestational history may provide the main predictive factors for pregnancy loss.
The association between gestational impaired glucose tolerance and hyperglycemic markers: A prospective study
Authors: Gluck Ohad , Ganer Herman Hadas , Fainstein Nataly , Katz Neri , Bar Jacob , Kovo Michal
Published: January 2021

Objective

To investigate the association between gestational impaired glucose tolerance (GIGT), and laboratory and clinical hyperglycemic markers.

Methods

A prospective study in Holon between 2017 and 2019. Women with a singleton term delivery and one abnormal value in their last three oral glucose tolerance test measurements (OGTTs; GIGT group, n = 60) were compared with control women with normal glucose challenge test (GCT) and/or OGTT measurements (n = 60). Primary outcomes were elevated cord‐blood C‐peptide (>90th percentile), maternal hemoglobin A1c (HbA1c), abnormal HbA1c (>5.7%), and neonatal skinfold thickness. Secondary outcomes included large for gestational age (LGA).

Results

Women in the GIGT group were older (33.3 ± 5.3 vs 31.1 ± 4.8 years; P = 0.019), and had a higher rate of LGA (26.7% vs 6.7%; P = 0.005), macrosomia (13.3% vs 0%; P = 0.006), elevated C‐peptide (16.7% vs 1.7%, P = 0.008), and abnormal HbA1c (13.3% vs 0%, P = 0.006). Skinfold thickness was also significantly higher in the GIGT group. HbA1c (adjusted odds ratio [aOR], 10.48; 95% confidence interval [CI], 1.19–91.91; P = 0.033) and GIGT (aOR, 11.43; 95% CI, 1.78–73.39; P = 0.01) were independently associated with LGA.

Conclusion

Women with GIGT on OGTT demonstrated “hyperglycemic characteristics” relative to those with normal GCT and/or OGTT.
Age and Sex Differences in Load‐Induced Tibial Cortical Bone Surface Strain Maps
Authors: Carriero Alessandra , Javaheri Behzad , Bassir Kazeruni Neda , Pitsillides Andrew A , Shefelbine Sandra J
Published: January 2021

Bone adapts its architecture to the applied load; however, it is still unclear how bone mechano‐adaptation is coordinated and why potential for adaptation adjusts during the life course. Previous animal models have suggested strain as the mechanical stimulus for bone adaptation, but yet it is unknown how mouse cortical bone load‐related strains vary with age and sex. In this study, full‐field strain maps (at 1 N increments up to 12 N) on the bone surface were measured in young, adult, and old (aged 10, 22 weeks, and 20 months, respectively), male and female C57BL/6J mice with load applied using a noninvasive murine tibial model. Strain maps indicate a nonuniform strain field across the tibial surface, with axial compressive loads resulting in tension on the medial side of the tibia because of its curved shape. The load‐induced surface strain patterns and magnitudes show sexually dimorphic changes with aging. A comparison of the average and peak tensile strains indicates that the magnitude of strain at a given load generally increases during maturation, with tibias in female mice having higher strains than in males. The data further reveal that postmaturation aging is linked to sexually dimorphic changes in average and maximum strains. The strain maps reported here allow for loading male and female C57BL/6J mouse legs in vivo at the observed ages to create similar increases in bone surface average or peak strain to more accurately explore bone mechano‐adaptation differences with age and sex. © 2021 The Authors. JBMR Plus published by Wiley Periodicals LLC. on behalf of American Society for Bone and Mineral Research.
Skeletal Biology and Disease Modeling in Zebrafish
Authors: Dietrich Kristin , Fiedler Imke AK , Kurzyukova Anastasia , López-Delgado Alejandra C , McGowan Lucy M , Geurtzen Karina , Hammond Chrissy L , Busse Björn , Knopf Franziska
Published: January 2021

Zebrafish are teleosts (bony fish) that share with mammals a common ancestor belonging to the phylum Osteichthyes, from which their endoskeletal systems have been inherited. Indeed, teleosts and mammals have numerous genetically conserved features in terms of skeletal elements, ossification mechanisms, and bone matrix components in common. Yet differences related to bone morphology and function need to be considered when investigating zebrafish in skeletal research. In this review, we focus on zebrafish skeletal architecture with emphasis on the morphology of the vertebral column and associated anatomical structures. We provide an overview of the different ossification types and osseous cells in zebrafish and describe bone matrix composition at the microscopic tissue level with a focus on assessing mineralization. Processes of bone formation also strongly depend on loading in zebrafish, as we elaborate here. Furthermore, we illustrate the high regenerative capacity of zebrafish bones and present some of the technological advantages of using zebrafish as a model. We highlight zebrafish axial and fin skeleton patterning mechanisms, metabolic bone disease such as after immunosuppressive glucocorticoid treatment, as well as osteogenesis imperfecta (OI) and osteopetrosis research in zebrafish. We conclude with a view of why larval zebrafish xenografts are a powerful tool to study bone metastasis. © 2021 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).
Comparative evaluation of the toxicological effect of silver salt (AgNO3) and silver nanoparticles on Cyprinus carpio synthesized by chemicals and marine algae using scanning electron microscopy
Authors: Liaqat Fareeha , Hanif Uzma , Bahadur Saraj , Faheem Mehwish , Rasool Saba , Gulzar Sadia , Zaman Wajid , Urooj Zara , Shaheen Shabnum , Munir Mubashrah
Published: January 2021

The widespread use of silver nanoparticles (AgNPs) results in the unintentional release into the water body. Therefore, understanding of the potentially harmful impacts of AgNPs and Ag‐salt on aquatic animals is a need of time. This study was design to analyze the oxidative stress and histopathological damages in Cyprinus carpio. The synthesis of AgNPs from Halymenia porphyraeformis and by reduction of chemical was done. Nanoparticles were characterized with UV–Visible spectroscopy, SEM, XRD, and FTIR analysis. The comparative toxicological effect of chemically synthesized silver nanoparticles (Ch‐AgNPs), green silver nanoparticles (Gr‐AgNPs), and Ag‐salt on C. carpio was analyzed. For oxidative stress analysis, different tests Lipid peroxidation (LPO), catalase, glutathione reduction (GST), and glutathione S‐transferase (GST) were performed. The highest LPO 245.168 ± 0.034 was recorded in Ch‐AgNPs‐treated gills and the lowest 56.4532 ± 0.02 was found in Gr‐AgNPs‐treated liver. Maximum GSH 56.4065 ± 0.13 was observed in Gr‐AgNPs liver and minimum 40.781 ± 0.54 was recorded in Ag‐salt gills. The maximum quantity of catalase 68.0162 ± 0.09 was noted in the Ag‐salt‐treated liver and the minimum was calculated 17.3665 ± 0.01 in the liver of Ch‐AgNPs and highest values of GST 765.829 ± 0.11 were recorded in gills of Gr‐AgNPs and lowest 633.08 ± 0.26 in the liver of Ch‐AgNPs‐treated fish. In conclusion, maximum destruction was found in the gills and liver of the fish treated with chemical and green AgNPs followed by Ag‐salt as compared to control. The adverse effects of AgNPs and Ag‐salt were probably related to the oxidative stress in the fish that lead to histopathological damage of its vital organs.
Novel 1,2,3‐triazolo phosphonate derivatives as potential antibacterial agents
Authors: Telu Jhonsee Rani , Kuntala Naveen , Kankanala Kavitha , Banothu Venkanna , Pal Sarbani , Anireddy Jaya Shree
Published: January 2021

We describe the synthesis, characterization, and in vitro antibacterial evaluation of a library of novel compounds based on 1,2,3‐triazolo phosphonate framework along with the evaluation of DNA gyrase inhibitory potential of a promising molecule in silico. Preparation of these compounds was carried out via a multistep sequence comprising of the Abramov reaction followed by the Cu(I)‐catalyzed azide–alkyne cycloaddition (CuAAC) as the key steps. Various α‐hydroxyphosphonate derivatives containing either a secondary or tertiary alcohol at the α position were prepared. When screened for their antibacterial activities in vitro using a Gram‐positive (Staphylococcus aureus) and three Gram‐negative (Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa) strains, majority of these derivatives exhibited reasonable to good effects with the analogue 5k being active against all the strains. The SAR analysis indicated that the activity was influenced by the position of the α‐hydroxyphosphonate moiety as well as the substituent present on the benzene ring attached to the 1,2,3‐triazole ring. Moreover, the compound 5k showed strong interactions with the DNA active site when docked into the DNA gyrase in silico. Thus, the 1,2,3‐triazolo phosphonate derivative 5k appeared to be a novel and promising hit molecule that deserves further study as a potential antibacterial agent.
A rapid and cost‐effective multiplex ARMS‐PCR method for the simultaneous genotyping of the circulating SARS‐CoV‐2 phylogenetic clades
Authors: Islam Mohammad Tanvir , Alam ASM Rubayet Ul , Sakib Najmuj , Hasan Mohammad Shazid , Chakrovarty Tanay , Tawyabur Mohammad , Islam Ovinu Kibria , Al‐Emran Hassan M. , Jahid Mohammad Iqbal Kabir , Anwar Hossain Mohammad
Published: January 2021

Tracing the globally circulating severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) phylogenetic clades by high‐throughput sequencing is costly, time‐consuming, and labor‐intensive. We here propose a rapid, simple, and cost‐effective amplification refractory mutation system (ARMS)‐based multiplex reverse‐transcription polymerase chain reaction (PCR) assay to identify six distinct phylogenetic clades: S, L, V, G, GH, and GR. Our multiplex PCR is designed in a mutually exclusive way to identify V–S and G–GH–GR clade variants separately. The pentaplex assay included all five variants and the quadruplex comprised of the triplex variants alongside either V or S clade mutations that created two separate subsets. The procedure was optimized with 0.2–0.6 µM primer concentration, 56–60°C annealing temperature, and 3–5 ng/µl complementary DNA to validate on 24 COVID‐19‐positive samples. Targeted Sanger sequencing further confirmed the presence of the clade‐featured mutations with another set of primers. This multiplex ARMS‐PCR assay is a fast, low‐cost alternative and convenient to discriminate the circulating phylogenetic clades of SARS‐CoV‐2.
Purified anthocyanins from Zea mays L. cob ameliorates chronic liver injury in mice via modulating of oxidative stress and apoptosis
Authors: Cui Hong‐Xin , Luo Yang , Mao Yue‐Yue , Yuan Ke , Jin Song‐Heng , Zhu Xiang‐Tao , Zhong Bing‐Wei
Published: January 2021

BACKGROUND

Purple corn (Zea mays L.) is one of the main economic crops in China and has been used in the treatment of cystitis, urinary infections and obesity. However, purple corncobs, the by‐product remaining after processing and having an intense purple‐black color, are normally disposed of as waste or used as animal feed. Therefore, to further expand the medicinal value of purple corncob, its content was analyzed and, after purification, the effect and mechanism of purified purple corncob anthocyanins (PPCCA) on CCl4‐induced chronic liver injury in mice were investigated.

RESULTS

It was observed that the total anthocyanin content (TAC) from PPCCA (317.51 ± 9.30 mg cyanidin 3‐O‐glucoside (C‐3‐G) g−1 dry weight) was significantly higher than that from the purified purple corn seed anthocyanin (266.73 ± 3.67 mg C‐3‐G g−1 dry weight), of which C‐3‐G accounted for 90.6% and 90.4% of the TAC, respectively. Furthermore, compared with the CCl4 group, PPCCA treatment significantly reduced liver index, serum total bilirubin, alanine transaminase, aspartate transaminase and liver malondialdehyde levels, but increased liver superoxide dismutase activity. The pathological changes were also improved, such as more regular arrangement of hepatocytes, less swelling, and fewer vacuoles and apoptotic cells. Additionally, mechanistic studies showed that PPCCA downregulated the expression of Caspase‐3, Bax and cytochrome P450 2E1 proteins in the liver and upregulated the expression of Bcl‐2.

CONCLUSION

These results demonstrated that PPCCA could ameliorate CCl4‐induced chronic liver injury by regulating oxidative stress and hepatocyte apoptosis pathways. © 2021 Society of Chemical Industry
Synovitis and Tenosynovitis on Ultrasound as Predictors of DMARD Tapering Failure in Patients with Long‐Standing Rheumatoid Arthritis in Clinical Remission or Low Disease Activity
Authors: Massignan Ângela , Mendonça da Silva Chakr Rafael , Pamplona Bueno de Andrade Nicole , Brenol Claiton Viegas
Published: January 2021

Objectives

This study aimed to investigate the predictive value of synovitis and tenosynovitis detected by grayscale (GS) and by power Doppler (PD) ultrasound (US) in relation to failure of tapering disease‐modifying antirheumatic drugs (DMARD) in rheumatoid arthritis (RA) patients.

Methods

Long‐standing RA patients who de‐escalated treatment were included in this prospective cohort study. All patients underwent 3 ultrasonographic and clinical assessments, at baseline and every 3 or 4 months, over a period of 6–8 months. US investigation of 32 joints was performed. Synovitis was assessed by GS and PD semiquantitative scoring (0–3) and a global score was calculated for each individual by summing single joint scores. The presence of tenosynovitis was recorded whenever detected during ultrasound assessment.

Results

Thirty‐three patients completed the follow‐up period (29 women; 4 men). Eight patients (25%) relapsed. Using the optimal cutoff values determined by receiver operating characteristic curve, patients with a PD synovitis ≥1 at baseline had significantly greater chances to relapse than those without PD activity. During follow‐up, GS tenosynovitis was detected in 6 patients (5 with PD) who failed and in 3 patients (1 with PD) who succeeded in tapering therapy. Having at least 1 joint with PD synovitis resulted in a relative risk of 3.14 and having GS tenosynovitis resulted in a relative risk of 11.4 (95% CI: 1.03–9.60 and 2.82–45.9, respectively) for relapse in the multivariate Poisson model.

Conclusions

PD synovitis and GS tenosynovitis may be useful to identify RA patients in risk of relapse after DMARD tapering.
Grazing exclusion regulates bacterial community in highly degraded semiarid soils from the Brazilian Caatinga biome
Authors: de Araujo Pereira Arthur Prudêncio , Lima Lara Andrade Lucena , Bezerra Walderly Melgaço , Pereira Mirella Leite , Normando Leonardo Ribeiro Oliveira , Mendes Lucas William , de Oliveira Jose Gerardo Beserra , Araújo Ademir Sérgio Ferreira , Melo Vânia Maria Maciel
Published: January 2021

Grazing exclusion has been applied as a suitable strategy for soil conservation worldwide, mainly on semiarid soils. However, it is unclear how grazing exclusion reduces the negative effects of overgrazing on the microbial community in the Caatinga biome. In our study, we assessed the bacterial community under three different soil managements in a semiarid region of the Brazilian Caatinga biome, as follows: (a) Native Caatinga vegetation (natural); (b) grazing exclusion (exclusion); and (c) overgrazing (grazed). The bacterial community was assessed through the sequencing of the V4 region of the 16S rRNA gene and analyzed soil chemical and physical properties were correlated with the bacterial community structure. Our results demonstrate that exclusion increases the content of soil carbon and nitrogen, and bacterial diversity, while grazed showed a reduction of ~31 and ~43% in organic C, compared to exclusion and natural, respectively. However, the changes in bacterial diversity were more expressive in a specific site (No. 1), suggesting that exclusion strategy could be a context‐dependent and complex approach to protecting or improving Caatinga soils. Moreover, grazed areas might restrain the potential of bacterial diversity to sustain ecosystem functions since nonbeneficial elements increased in grazed treatments, which presented a negative correlation with the bacterial community. Our study provides novel evidence that high‐intensity disturbance by overgrazing could not only reduce soil fertility but it may also restrain bacterial composition, with implications on ecosystem functioning. The Caatinga soil microbiome may be unable to maintain ecosystem services such as plant and animals' development under overgrazing management.
A Toughening and Anti‐Counterfeiting Benzotriazole‐Based High‐Performance Polymer Film Driven by Appropriate Intermolecular Coordination Force
Authors: Cao Liang , Yang Li , Xu Yewei , Yin Qiang , Huang Ying , Chang Guanjun
Published: January 2021

It is of great significance to circumvent the inherent trade‐off between strength and extensibility for epoxy resins. Herein dynamic Cu‐benzotriazole cross‐links are incorporated, as the appropriate intermolecular coordination interaction, into high performance epoxy networks, and the resulting epoxy resins exhibits outstanding thermal stability and mechanical properties, their strength and extensibility are simultaneously improved. Additionally, local manipulation of coordination crosslinking confers the film with anti‐counterfeiting function.
A free intercostal artery perforator flap as a salvage operation for a planned lumbar artery perforator flap with aberrant anatomy in breast reconstruction: A case report
Authors: Sharp Olivia L. , Köhler Guido , Masud Dhalia , Haywood Richard M.
Published: January 2021

When autologous breast reconstruction is planned but abdominal tissue is not available, the lumbar artery perforator flap provides an alternative choice with minimal donor site morbidity. The lumbar and posterior intercostal arteries supply adjacent perforasomes on the posterolateral flank. The purpose of this report is to highlight the salvage of an autologous breast reconstruction free flap using a dorsal perforator of the posterior intercostal artery, when the planned lumbar artery perforators were not suitable. The patient was a 74‐year‐old with recurrent left‐sided breast cancer requiring immediate breast reconstruction. A lumbar perforator flap was planned as an oblique ellipse 19 × 10 cm. Intraoperatively, the two identified perforators traveled superiorly up to the 12th rib and therefore originated from the intercostal rather than lumbar arteries. The internal mammary artery and the vena comitants were used as recipient vessels, anastomosed to an interposition graft. Postoperatively, the patient was discharged home after 7 days without complication. Six months later, the patient was pleased with the reconstruction and had negligible donor site morbidity. The dorsal intercostal artery perforator flap therefore provides a salvage option when presumed lumbar artery perforators are dissected and found to be intercostal in origin.
Optimal time decay rates of solutions for the 2D generalized magneto‐micropolar equations
Authors: Ye Hailong , Mao Yiqiu , Jia Yan
Published: January 2021

This study is concerned with the optimal time rates of weak solutions for the 2D magneto‐micropolar equations with only micro‐rotational dissipation and magnetic diffusion. Due to some new observations, we obtain the optimal time decay rates of weak solutions
and
with p ∈ [2, ∞).
A 21.5 ~ 25 GHz 7‐bit phase shifter with passive vector‐sum topology
Authors: Wu Tianjun , Zhang Xiaoning , Xing Zhao , Zhao Chenxi , Yu Yiming , Liu Huihua
Published: January 2021

A 7‐bit passive phase shifter with low‐phase error is presented in 65 nm CMOS technology. The vector‐sum topology is implemented to enable passive phase shifter the ability of flexible phase calibration. Therefore, the passive phase shifter with high resolution and low‐phase error is achieved. In order to achieve high linearity, attenuator based on resistor is implemented to scale the I/Q signals, and a vector synthesizer based on balun is utilized to sum the quadrature vectors. Measurement results show that the phase shifter achieves 7‐bit resolution. The measured root mean square (RMS) phase error is <2.1°, and the RMS gain error is <1.2 dB over 21.5 ~ 25 GHz. The measured input‐referred P1dB is >10 dBm. The measured peak gain is about −14.3 dB, and the return loss is >8 dB. The chip has no DC power consumption and occupies an area of 880 × 500 um. The measurement results demonstrate the proposed phase shifter is very suitable for high linearity and high‐angular resolution phased arrays in K‐band.
Accurate and efficient algorithms with unconditional energy stability for the time fractional Cahn–Hilliard and Allen–Cahn equations
Authors: Liu Zhengguang , Li Xiaoli , Huang Jian
Published: January 2021

Comparing with the classic phase filed models, the fractional models such as time fractional Allen–Cahn and Cahn–Hilliard equations are equipped with Caputo fractional derivative and can describe more practical phenomena for modeling phase transitions. In this paper, we construct two accurate and efficient linear algorithms for the time fractional Cahn–Hilliard and Allen–Cahn equations with general nonlinear bulk potential. The main contribution is that we have proved the unconditional energy stability for the time fractional Cahn–Hilliard and Allen–Cahn models and their semi‐discrete schemes carefully and rigorously. Several numerical simulations in 2D and 3D are demonstrated to verify the accuracy and efficiency of our proposed schemes.
Redefining the Treatment Endpoints in Oncology
Authors: Kaul Pallvi , Garg Pankaj Kumar
Published: January 2021

The jargon and survival data used by oncologists to communicate with patients may not be fully understood by a patient, resulting in a hasty decision without a proper understanding of its implications. This letter to the editor calls for more patient-friendly language to improve communication.
Learning‐Based Model Predictive Control for Multi‐Agent Systems using Gaussian Processes
Authors: Eschmann Hannes , Eberhard Peter
Published: January 2021

Model Predictive Control (MPC), also referred to as Moving Horizon Control (MHC), experienced a massive growth of interest over the last decades due to increasing computing power and the ability to naturally incorporate state and input constraints. As a model‐based controller, the performance of Model Predictive Control heavily relies upon the quality of the model used. One can leverage measurement data to improve upon a nominal model, e.g., based on first principles, using Gaussian Processes, or other regression techniques. We instead opt for the introduction of (nonlinear) rate constraints to force the system to stay within regions of the state space where a simple, possibly linear, model describes the underlying dynamics well, while still robustly accounting for small model mismatches introduced with the simple model. These rate constraints can again be learned using any parametric or non‐parametric regression method, making the approach very flexible. As an exemplary system, we choose an omnidirectional mobile robot moving in an environment with changing friction coefficients, putting state‐dependent limits on the maximal rate of change of its speed.
Free‐edge delamination in composite laminates under tensile loading: An analytical closed‐form approach
Authors: Frey Christopher , Dölling Sebastian , Becker Wilfried
Published: January 2021

In the present study, interlaminar crack initiation in symmetric angle‐ply laminates under tensile loading is investigated using the coupled stress and energy criterion, whereby the required stress and energy quantities are determined by means of a new analytical closed‐form model. The identification of unknown interface fracture toughnesses is addressed by a parameter fit within physical reasonable limits. The resulting effective failure loads are compared to experimental data and show the high potential of the coupled criterion on the one hand and of the proposed analytical model on the other hand.
Application of a reduced basis method for an efficient treatment of structural mechanics problems
Authors: Bremm Sophia , Rosendahl Philipp L. , Becker Wilfried
Published: January 2021

For numerous problems in structural mechanics, a repeated solution of partial differential equations (PDEs), varying certain input parameters, is necessary. Solving the PDE for a large number of different input parameter sets using a full‐dimensional finite element method, requires repeated solving of large systems of equations and, thus, leads to a high computational effort. The aim of model order reduction techniques is to reduce the computational complexity in such calculations. In order to achieve this, the idea of the reduced basis method [1–3] is to replace the high‐dimensional model with a lower dimensional model, which is realized by forming a basis of solutions of the full problem for selected parameter sets. Key to determining suitable parameter sets is an appropriate error estimator.
Numerical treatment of the spike formation stage in marginally separated flows
Authors: Kuzdas Dominik , Braun Stefan
Published: January 2021

The method of matched asymptotic expansions is used to describe the so‐called ’by‐pass' transition in marginally separated boundary layer flows. Such flows may typically be observed e.g. on the suction side of a slender airfoil if the angle of attack is raised above a critical value. As a consequence, transition to turbulent flow is triggered by the repeated bursting of a laminar separation bubble. For asymptotically large Reynolds numbers the bursting of a laminar separation bubble can be described by various consecutive stages. The present work addresses the numerical solution of the triple deck stage succeeding a finite‐time blow‐up of the marginal separation stage. Although the corresponding evolution equations of the triple deck stage have been studied extensively by Elliott and Smith, a reliable numerical solution has not yet been presented. Special emphasis is placed on the formulation of the matching condition to the terminal structure of the preceding marginal separation stage.
Study of stochastic aspects in the modeling of the strain‐induced crystallization in unfilled polymers
Authors: Aygün Serhat , Klinge Sandra
Published: January 2021

The present contribution deals with the mechanical modeling of the crystallization of unfilled polymers under consideration of stochastic aspects of the process. The framework applied is thermodynamically consistent. The model involves the diameter of crystalline regions and the distance between these regions as internal variables. The necessary evolution equations are based on the assumptions for the effective free energy and the dissipation potential of a control volume. A distribution function is introduced to express the expectation value of relevant quantities. Furthermore, the numerical implementation of probability integrals is shown. The proposed concepts are of general nature and can be taken as a basis for the modeling of similar stochastic processes involving the evolution of the internal microstructure.
An RVE‐based investigation of thermoplastic vulcanizates exemplified by EPDM/PP
Authors: Sun Wanrong , Juhre Daniel
Published: January 2021

In this contribution, the material behaviour of thermoplastic vulcanizate is investigated using the example of ethylene‐propylene‐diene monomer rubber (EPDM) and polypropylene (PP). For modelling of viscoelastic effects, the generalized Maxwell element is applied, whereby the isochoric stresses of parallel Maxwell elements are determined via evolution equations. In order to take the morphological composition of TPV into account, a representative volume element (RVE) consisting of PP as matrix and EPDM as included material is considered. In a following numerical example, a cyclic shear test is presented, where the resulting force and stress distribution is evaluated. Thus, the results show the macroscopic material behaviour under the consideration of microstructure.
Implicit Analysis of Reissner–Mindlin shells with the Trace FEM
Authors: Schöllhammer Daniel , Fries Thomas-Peter
Published: January 2021

The linear Reissner–Mindlin shell is discretized with the Trace FEM. The geometry of the shell is implicitly defined by means of (multiple) level‐set functions. The implementational aspects of the Trace FEM, i.e., integration, stabilization and essential boundary conditions, are considered in detail resulting in a higher‐order accurate Trace FEM.
An Efficient Adjoint Sensitivity Analysis of Flexible Multibody Systems for a Level‐set‐based Topology Optimization
Authors: Azari Nejat Ali , Held Alexander , Seifried Robert
Published: January 2021

For large‐scale topology optimization of flexible multibody systems, only little results exist. This is due to the complexity of the modeling of the flexible bodies and the big effort to provide exact gradients. The considered flexible multibody systems can undergo both large nonlinear motions as well as small elastic deformations. Here, the flexible components are modeled by the floating frame of reference approach. For gradient calculation, the fully coupled adjoint sensitivity analysis is used, which is a semi‐analytical approach based on variational calculus. The computational effort strongly corresponds to the number of design variables. In this work, a design space reduction using radial basis functions is performed and the gradient of flexible components is constructed based on its exact value on a subset of selected design elements. In order to show the substantial gain in computation time, the exact and approximated gradient of a flexible crank in a slider‐crank mechanism are computed and applied for a level‐set‐based topology optimization.
Parametric FEM for computational homogenization of heterogeneous materials with random voids
Authors: Pivovarov Dmytro , Mergheim Julia , Willner Kai , Steinmann Paul
Published: January 2021

Computational homogenization is a powerful tool which allows to obtain homogenized properties of materials on the macroscale from the simulation of the underlying microstructure. The response of the microstructure is, however, strongly affected by variations in the microstructure geometry. The effect of geometry variations is even stronger in cases when the material exhibits plastic deformations. In this work we study a model of a steel alloy with arbitrary distributed elliptic voids. We model one single unit cell of the material containing one single void. The geometry of the void is not precisely known and is modeled as a variable orientation of an ellipse. Large deformations applied to the unit cell necessitate a finite elasto‐plastic material model. Since the geometry variation is parameterized, we can utilize the method recently developed for stochastic problems but also applicable to all types of parametric problems — the isoparametric stochastic local FEM (SL‐FEM). It is an ideal tool for problems with only a few parameters but strongly nonlinear dependency of the displacement fields on parameters. Simulations demonstrate a strong effect of parameter variation on the plastic strains and, thus, substantiate the use of the parametric computational homogenization approach.
Dynamics of a magnetic pendulum in the presence of an oscillating conducting plate
Authors: Boeck Thomas , Sanjari Seyed Loghman , Becker Tatiana
Published: January 2021

A pendulum with an attached permanent magnet moving near a conductor is a typical experiment for the demonstration of electromagnetic braking. When the conductor itself moves, it can transfer energy to the pendulum. We study a simple but exact analytical model where the conductor is a horizontally unbounded flat plate. For this geometry, eddy currents and induced Lorentz force due to the motion of a magnetic dipole are known analytically in the quasistatic limit. A vertical oscillation of such a horizontal plate located beneath the magnet is considered. In this setup, the vertical position of the pendulum is an equilibrium point when the magnetic moment of the magnet is perpendicular to its plane of motion. Depending on the strength of the magnetic dipole moment, the frequency and amplitude of the plate as well as the distance between plate and magnet, the plate oscillation can destabilize the equilibrium. The stability limits for weak electromagnetic coupling are computed analytically using the harmonic balancing method. For stronger coupling, the stability limits are obtained numerically using Floquet analysis. Chaotic motions with finite amplitudes are also found.
Study of Exploiting Coarse‐Grained Parallelism in Block‐Oriented Numerical Linear Algebra Routines
Authors: Kroiz Gerson C. , Bardakoff Alexandre , Blattner Timothy , Keyrouz Walid
Published: January 2021

We have developed streaming implementations of two numerical linear algebra operations that further exploit the block decomposition strategies commonly used in these operations to obtain performance. The implementations formulate algorithms as data flow graphs and use coarse‐grained parallelism to (1) emit a block in the result matrix as soon as it becomes available and (2) compute on multiple blocks in parallel. This streaming design benefits data flow graphs consisting of multiple linear algebra operations as it removes synchronization points between successive operations: a result block from an operation can be used immediately in an algorithm's successor operations without waiting for the full result from the first operation. Early comparisons with OpenBLAS functions on CPUs show comparable performance for computing with large dense matrices and an earliest arrival time of a result block that is up to 50x smaller than the time needed for a full result. More thorough studies can show the impact of such implementations on the performance of systems by chaining multiple linear algebra operations.
A multi‐scale fatigue‐damage model for fiber‐reinforced polymers
Authors: Magino Nicola , Köbler Jonathan , Andrä Heiko , Schneider Matti , Welschinger Fabian
Published: January 2021

Experimental studies of Chebbi et al. [1] on fatigue loading of fiber‐reinforced polymers have shown that there is a phase of stable stiffness decrease prior to growing fatigue cracks. Modeling this stiffness degradation is an essential step in understanding fatigue effects of these materials.

The constitutive behavior of short‐fiber reinforced polymers depends on numerous factors, such as fiber‐volume content, the aspect ratio of the fibers, the fiber‐orientation tensor and the loading direction. Accounting for these influence factors on a purely experimental basis is very time and resource demanding.

As a remedy, we follow a multi‐scale approach for simulating the fatigue‐damage evolution in short‐fiber reinforced polymers. Using a simple damage model for the polymer matrix, the model inherently accounts for the influence of the fiber micro‐structure through homogenization. We show that the stiffness degradation predicted by this model is of anisotropic nature and depends strongly on loading direction and fiber‐orientation tensor.

Due to its specific structure, the model permits a straightforward model‐order‐reduction strategy and can be efficiently employed for component‐scale simulations, see Köbler et al. [3].
Buckling analysis of elastically clamped laminated plates using third‐order shear deformation theory
Authors: Schreiber Philip , Mittelstedt Christian , Beerhorst Matthias
Published: January 2021

This paper considers the buckling of transverse shear‐deformable orthotropic laminated plates under uniaxial compression, which is modeled with the third‐order shear deformation theory (TSDT). The consideration of transverse shear deformation is relevant for plates with small transverse shear stiffness or small length to thickness ratio. The supporting effect of the surrounding structure is represented by laterally attached rotational restraints. The present analysis approach uses a simple energy‐based formulation in the form of a Rayleigh‐quotient for which specific shape functions for the out‐of‐plane buckling deformations as well as for the rotational degrees of freedom are employed. A comparison of the results with the Lévy‐type solution shows that the analysis approach works with satisfying accuracy, thus making it suitable for engineering analysis of plates with arbitrary thickness especially when computational time and effort are essential factors.
Revisiting Mindlin's theory with regard to a gradient extended phase‐field model for fracture
Authors: Makvandi Resam , Abali Bilen Emek , Eisenträger Sascha , Juhre Daniel
Published: January 2021

The application of generalized continuum mechanics is rapidly increasing in different fields of science and engineering. In the literature, there are several theories extending the classical first‐order continuum mechanics formulation to include size‐effects [1]. One approach is the strain gradient theory with the intrinsic features of regularizing singular stress fields occurring, e.g., near crack tips. It is crucial to realize that using this theory, the strain energy density is still localized around the crack tip, but does not exhibit any signs of a singularity. Therefore, these models seem to be appropriate choices for studying cracks in mechanical problems. Over the past several years, the phase‐field method has gathered considerable popularity in the computational mechanics community, in particular in the field of fracture mechanics [2]. Recently, the authors have shown that integrating the strain gradient theory into the phase‐field fracture framework is likely to improve the quality of the final results due to the inherent non‐singular nature of this theory [3]. In the present work, we will focus on a general formulation of the first strain gradient theory. To this end, the homogenization approach introduced in Ref. [4] is employed. It is based on a series of systematic finite element simulations using different loading cases to determine the equivalent material coefficients on the macro‐scale (i.e., for a strain gradient elastic material) by taking the underlying micro‐structure into account.
Towards a physiologically accurate ECG from numerical simulations: comparative analyses in a simplified tissue model
Authors: Ogiermann Dennis , Perotti Luigi E. , Balzani Daniel
Published: January 2021

Numerical simulations of the human heart can guide medical doctors and researchers only if properly validated. This work presents a computational framework to validate mathematical models of cardiac electrophysiology at the tissue level. Specifically, we focus on the transmural wedge experiment as proposed by Antzelevitch in 1996. This experimental setup is easily reproduced and allows to probe key modeling assumptions and components before organ level simulations are performed. Our results highlight the need to further investigate the conductivity tensor, which, by modifying wave propagation, will affect the ECG morphology at the organ level.
Damage and failure mechanisms of ductile metals in biaxial experiments with non‐proportional loading paths
Authors: Zistl Moritz , Gerke Steffen , Brünig Michael
Published: January 2021

The paper deals with an experimental series and corresponding numerical simulations of the biaxial X0‐specimen to study the loading path dependence of ductile damage and fracture under non‐proportional loading. Experimentally the specimen surfaces have been monitored by digital image correlation (DIC). The experimental–numerical technique applied to the non‐proportional biaxial experiments provides new insights of the stress and load‐history dependent damage and fracture processes.
Adaptive Orientation of Exponential Finite Elements for a Phase Field Fracture Model
Authors: Olesch Darius , Kuhn Charlotte , Schlüter Alexander , Müller Ralf
Published: January 2021

One technique to describe the failure of mechanical structures is a phase field model for fracture. Phase field models for fracture consider an independent scalar field variable in addition to the mechanical displacement [1]. The phase field ansatz approximates crack surfaces as a continuous transition zone in which the phase field variable varies from a value that indicates intact material to another value that represents cracks. For a good approximation of cracks, these transition zones are required to be narrow, which leads to steep gradients in the fracture field. As a consequence, the required mesh density in a finite element simulation and thus the computational effort increases. In order to circumvent this efficiency problem, exponential shape functions were introduced in the discretization of the phase field variable, see [2]. Compared to the bilinear shape functions these special shape functions allow for a better approximation of the steep transition with less elements. Unfortunately, the exponential shape functions are not symmetric, which requires a certain orientation of elements relative to the crack surfaces. This adaptation is not uniquely determined and needs to be set up in the correct way in order to improve the approximation of smooth cracks. The issue is solved in this work by reorientating the exponential shape functions according to the nodal value of phase field gradient in a particular element. To be precise, this work discusses an adaptive algorithm that implements such a reorientation for 2d and 3d situations.
The Influence of ground inclination on the energy efficiency of a bipedal walking robot
Authors: Luo Yinnan , Römer Ulrich J. , Fidlin Alexander
Published: January 2021

One of the major tasks in developing bipedal walking robots is to improve energy efficiency of their locomotion. In this paper a method for extending this research by considering ground inclinations is introduced. The investigated robot is driven by electric motors in its revolute joints. Robot's gaits for different walking speeds are generated via numerical optimization, minimizing energy consumption during locomotion. Energy efficiency can be increased for differently inclined grounds where the robot utilizes its natural dynamics and gravity.
Probabilistic damage simulation for strengthening design of concrete structures
Authors: Molod Mohammad Amin , Barthold Franz-Joseph , Spyridis Panagiotis
Published: January 2021

Shape memory alloy (SMA) is a smart material that can be applied as an internal and external reinforcement of reinforced concrete flexural elements in order to increase ductility and strength of the members. Column‐beam joint is a critical section of a concrete structure which under seismic and unexpected heavy loads may lead to failure of entire of the structure. Therefore, this numerical investigation aims to increase strength and mitigate risk of failure of the joint by employment of SMA plate. To do so, an experimentally investigated joint under 1000 load combinations has been simulated in Ansys APDL. Each load combo contained two axial loads and one bending moment; load values have been randomly selected through a procedure in MATLAB. Some nodes in plastic hinge region of the joint were chosen as control points. Generated load values were applied in the simulation, and stress of the control nodes was recorded. This process continued for all 1000 combos. Then, obtained results were imported into MATLAB for a probabilistic analysis. Probability of 0.95 quantile of stress of each node was calculated in order to design the required plate thickness at each node. Some numerical examples were applied on the designed plate. Results demonstrated that the designed SMA plate gets the risk of failure from the joint away and increase strength of the joint.
Local Refinement in Isogeometric Analysis of Complex Tire Models
Authors: Israfilova Alina , Garcia Mario A. , Kaliske Michael
Published: January 2021

The capability of Non‐Uniform Rational B‐Splines (NURBS) to exactly represent conic sections exactly makes Isogeometric Analysis (IGA) an attractive alternative to classical Finite Element Method (FEM) for tire simulation. Application of NURBS as basis functions for geometry representation simplifies the generation of the computational mesh that can be directly obtained from the software for graphical design. NURBS‐based approximations of the field variables lead to higher convergence rates and allow higher continuity across the element boundaries. Moreover, the tensor structure of these functions permits the usage of additional advanced refinement techniques.

The contribution at hand focuses on the application of hierarchically nested basis functions in tire analysis. The developed framework is based on the introduction of the global multilevel Bézier extraction operator [1]. This approach allows local refinement in the existing isoparametric FEM code without violating its architecture. Within the introduced framework, material models developed for standard FEM can be retained.

Special attention is paid to the modelling of rebar elements within the framework of IGA and local refinement in particular. The from standard FEM adopted unconventional method avoids the drawbacks of smeared formulations common in tire numerical analysis and does not require an explicit definition of the reinforcing bars [2]. An additional check of the volumetric content of rebar in the material allows the compatibility of the employed concept with locally improved meshes.

Numerical simulations for rolling tires using IGA are presented. The complex multilevel composite structure of tire‐models is obtained by means of CAD‐software. All simulations are performed under the consideration of steady‐state rolling within the Arbitrary Lagrangian‐Eulerian (ALE) description including finite deformations. A benchmark study of IGA and FEM for tire analysis closes this presentation.
Plasticity, Viscosity, Regelation – Remarks on the bitter Forbes–Tyndall Controversy
Authors: Gross Dietmar
Published: January 2021

The paper highlights a few aspects of the so‐called Great Glacier Controversy which started from questions regarding the viscosity of ice, which touched priority issues and which affected the just emerging thermodynamics and leading scientists.