bluuebunny/crossref_metadata_2025 huggingface dataset:
Procyanidin‐B2 enriched fraction of cinnamon acts as a proteasome inhibitor and anti‐proliferative agent in human prostate cancer cells
Authors: Gopalakrishnan Srividya , Ediga Harshavardhana H. , Reddy S. Sreenivasa , Reddy G. Bhanuprakash , Ismail Ayesha
Published: March 2018

Altered activity of the proteolytic machine—the 26S proteasome is observed in many disease conditions. Hence, either inhibition or activation of the 26S proteasome is thought to be a novel therapy for treatment of certain diseases such as cancer and neurodegenerative disorders. In this study, we tested the potential of cinnamon and one of its active ingredients, procyanidin‐B2 (PCB2), in inhibiting the catalytic activities of the proteasome and suppressing prostate cancer cell growth. Proteasome activities were measured using fluorogenic substrates specific for the different enzymatic activities of the 26S proteasome by flourometry. Cell viability was assessed using the 3‐[4, 5‐dimethylthiazol‐2‐yl]‐2.5‐diphenyl‐tetrazolium bromide assay, while apoptosis was examined by Hoechst and propidium iodide staining and caspase‐3 activity. Both, the cinnamon extract and its PCB2‐enriched F2 fraction inhibited the catalytic activities of the purified proteasome and the proteasome in cancer cells but not in normal cells. Furthermore, cinnamon and its active component decreased cell proliferation of human prostate cancer cells but not normal lung cells, decreased expression of anti‐apoptotic and angiogenic markers in prostate cancer cell lysates. These results demonstrate that cinnamon extract and its PCB2‐enriched fraction act as proteasome inhibitors and have prospects as anti‐cancer agents. © 2018 IUBMB Life, 70(5):445–457, 2018
Literary Analysis Using Minecraft: An Asian American Youth Crafts Her Literacy Identity
Authors: Marlatt Rick
Published: March 2018

This article describes a recent teacher researcher's investigation of digitized literature study at a Midwestern U.S. high school during the 2015–2016 school year that explored the use of digital literacies to support student‐centered literary analysis. Digital literacy practices position literature students to connect with texts in authentic ways. In their reading of The Outsiders by S.E. Hinton, students used the video game Minecraft to re‐create scenes, respond to literary elements, and analyze deeper meanings. The analyses of one particular student resulted in powerful explorations of identity. Using qualitative research tools, the author analyzed her case through observations, interviews, and student‐created artifacts to understand how this popular technology could facilitate literary analysis at the secondary level.
A kink that makes you sick: The effect of sick pay on absence
Authors: Böckerman Petri , Kanninen Ohto , Suoniemi Ilpo
Published: March 2018

We exploit a regression kink design to estimate the elasticity of the duration of sickness absence with respect to replacement rate. Elasticity is a central parameter in defining the optimal social insurance scheme compensating for lost earnings due to sickness. We use comprehensive administrative data and a kink in the policy rule near the median earnings. We find a statistically significant estimate of the elasticity of the order of one.
Polydopamine/cysteine surface modified hemocompatible poly(vinylidene fluoride) hollow fiber membranes for hemodialysis
Authors: An Zihan , Dai Fengying , Wei Chenjie , Zhao Yiping , Chen Li
Published: March 2018

Membrane surface design is significant for the development and application of synthetic polymer hemodialysis membranes. In this study, the influence of zwitterionic cysteine on poly(vinylidene fluoride) (PVDF) hollow fiber membrane was investigated. The polydopamine layer was formed through dopamine self‐polymerization on PVDF membrane surface, and then cysteine was covalent grafted onto the layer to improve the anti‐biofouling property and hemocompatibility. The elementary composition of membrane surfaces was characterized by X‐ray photoelectron spectroscopy. The influence of polydopamine and cysteine on modified membrane surface morphologies was studied by field emission scanning electron microscopy. The modified PVDF membranes were confirmed to have excellent hydrophilicity, stable mechanical properties and good hemocompatibility (dynamic and static anti‐protein adsorption, hemolysis ratio, plasma coagulation). And these properties were increased with the incorporation of polydopamine and cysteine. The optimized modified membranes exhibited high pure water flux (∼ 195.5 L/m2h at 0.1 MPa) and selectivity (clearance ratio of urea and lysozyme was 75.1 and 55.4%, and rejection rate of bovine serum albumin was 98.8%). This work provides a surface modification method of PVDF hollow fiber membranes and suggests a potential application of PVDF membranes in hemodialysis field. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 2869–2877, 2018.
“Clowns to the left of me, jokers to the right”: Politics and psychotherapy, 2018
Authors: Farber Barry A.
Published: March 2018

The election and postelection policies of Donald Trump have seeped into the psychotherapy sessions of many clients, in ways that are somewhat unique but also somewhat reminiscent of the ways that other dramatic social–political events, including 9/11 and the social divisions that were characteristic of the 1960s, were brought into the treatment room. The nine articles within this issue—seven papers from practicing psychotherapists, one from an executive coach, and one empirical paper—suggest strongly that the political events surrounding the election of 2016 have become a significant part of psychotherapeutic discourse for many clients, that many therapists have been willing participants in such discussions, and that a focus on political issues (broadly speaking) can have important clinical benefits, facilitating the therapeutic alliance and leading to greater understanding of long‐standing client problems and interpersonal functioning. Taken together, these papers lead to the conclusion that, at a minimum, clinicians need to be sensitive to the very real possibility that their clients are acutely aware of and affected by the political events surrounding the 2016 presidential election and may welcome open discussion of these events and their consequences.
November 8, 2016: The day I became a White clinician
Authors: Bodnar Susan
Published: March 2018

When Donald Trump became president of the United States, I discovered that my clients who identified as Black saw me as a White clinician. With that came a host of nefarious attributions. To preserve therapeutic efficacy, and the genuine relationships with people about whom I cared, I had to distinguish myself from the president; thus, I learned not only how it feels to be seen through the bias of skin color but what I needed to do to identify as a person rather than a White person. “Welcome to my world,” said one African American client.
MicroRNA expression data analysis to identify key miRNAs associated with Alzheimer's disease
Authors: Chen Jing , Qi Yan , Liu Cui‐Fang , Lu Jing‐Min , Shi Jing , Shi Yan
Published: March 2018

Background

MicroRNAs (miRNAs) have become increasingly prevalent as a result of the association of their deregulation with neurodegenerative disorders, especially Alzheimer's disease (AD). However, the association between miRNAs and AD remains unclear.

Methods

In the present study, Nine representative miRNA datasets were selected for the identification of the critical miRNAs by analyzing the overlapping relationships among them. TargetScan software (http://www.targetscan.org) was used to predict the target genes of these miRNAs. In addition, the Database for Annotation Visualization and Integrated Discovery (DAVID; http://david.abcc.ncifcrf.gov) and TfactS (http://www.tfacts.org) datasets were used for combined analysis of functional enrichment and transcription factor (TF) analysis.

Results

Thirteen key miRNAs were identified, of which four were significantly up‐regulated (hsa‐miR‐101,hsa‐miR‐155, has‐miR‐34a, has‐miR‐9) and eight were found to be significantly down‐regulated (hsa‐let‐7d‐5p, hsa‐let‐7 g‐5p, hsa‐miR‐15b, has‐miR‐191‐5p, hsa‐miR‐125b, has‐miR‐26b‐5p, hsa‐miR‐29b, hsa‐miR‐342‐3p). The functional enrichment analysis indicated that up‐regulated signature miRNA targets were associated with transcription from the RNA polymerase II promoter process and the chemical synaptic transmission process. Down‐regulated signature miRNA targets were mostly enriched with respect to positive regulation of transcription from the RNA polymerase II promoter process, p53 signaling, and microRNAs in cancer pathways. TF analysis showed that 87 TFs were influenced by the up‐regulated miRNAs, and 134 TFs were influenced by the down‐regulated miRNAs. In total, 70 (45.5%) TFs were affected by both up‐regulated and down‐regulated miRNAs.

Conclusions

In summary, 13 key miRNAs were found to have a vital function in the pathological progress of AD, as well as the target genes and TFs of these miRNAs. The potential functions of these miRNAs as diagnostic and therapeutic targets of the AD are revealed by the present study.
Influence of laser‐induced heating on MnO nanoparticles
Authors: Hadžić B. , Vasić B. , Matović B. , Kuryliszyn‐Kudelska I. , Dobrowolski W. , Romčević M. , Romčević N.
Published: March 2018

The phase changes of MnO nanoparticles under laser‐induced heating have been studied. Previous confirmation of the existence of MnO phase was based on the X‐ray diffraction measurements. Here, we report the experimental spectra of nonresonant Raman scattering in the range between 100 and 1,600 cm−1, for a sample irradiated with 8 different laser powers. The laser‐induced heating has produced change in existing phases in sample, destruction of MnO phase, and creation of MnO2, Mn3O4, and MnOOH phases along with formation of Mn2+ on the sample surface. These phase changes have been confirmed by X‐ray diffraction and atomic force microscopy measurements.
Meta‐analysis and publication bias: How well does the FAT‐PET‐PEESE procedure work?
Authors: Alinaghi Nazila , Reed W. Robert
Published: March 2018

This paper studies the performance of the FAT‐PET‐PEESE (FPP) procedure, a commonly employed approach for addressing publication bias in the economics and business meta‐analysis literature. The FPP procedure is generally used for 3 purposes: (1) to test whether a sample of estimates suffers from publication bias, (2) to test whether the estimates indicate that the effect of interest is statistically different from zero, and (3) to obtain an estimate of the mean true effect. Our findings indicate that the FPP procedure performs well in the basic but unrealistic environment of fixed effects, where all estimates are assumed to derive from a single population value and sampling error is the only reason for why studies produce different estimates. However, when we study its performance in more realistic data environments, where there is heterogeneity in the population effects across and within studies, the FPP procedure becomes unreliable for the first 2 purposes and is less efficient than other estimators when estimating overall mean effect. Further, hypothesis tests about the mean true effect are frequently unreliable. We corroborate our findings by recreating the simulation framework of Stanley and Doucouliagos (2017) and repeat our tests using their framework.
Identification of vanilloid compounds in grains of paradise and their effects on sympathetic nerve activity
Authors: Hattori Hiroyuki , Yamauchi Kosei , Onwona‐Agyeman Siaw , Mitsunaga Tohru
Published: March 2018

BACKGROUND

Grains of paradise (GP) is the seed of Aframomum melegueta, which is widely distributed throughout West Africa and has been used as a spice and a folk remedy for a long time. Anti‐obesity effect of GP intake was demonstrated in a previous report. Aim of the present study was to isolate some compounds in GP and clarify the anti‐obesity mechanism.

RESULTS

Ten vanilloid compounds were isolated. Among them, 1‐(4′‐hydroxy‐3′‐methoxyphenyl)‐decan‐3‐ol and 1‐(4′‐hydroxy‐3′‐methoxyphenyl)‐3‐octen‐5‐one were determined as novel compounds and 6‐gingerol, 6‐paradol and 6‐shogaol were identified as the major constituents in GP extract. Moreover, the extract and 6‐gingerol, which is one of the principal components of GP extract, were orally administered to rats to investigate the effect on sympathetic nerve activity (SNA) in brown adipose tissue (BAT). The injection of GP extract and 6‐gingerol decreased BAT‐SNA, whereas capsaicin, which is a major component of chili pepper, activates the sympathetic nervous system.

CONCLUSION

This study suggested that GP extract and 6‐gingerol were largely unrelated to the anti‐obesity effect by the activation of interscapular BAT‐SNA and had a different anti‐obesity mechanism to capsaicin. © 2018 Society of Chemical Industry
Differential Effects of Estrogen and Progestin on Apolipoprotein B100 and B48 Kinetics in Postmenopausal Women
Authors: Lamon‐Fava Stefania , Diffenderfer Margaret R. , Barrett P. Hugh R. , Wan Wing Yee , Postfai Borbala , Nartsupha Chorthip , Dolnikowski Gregory G. , Schaefer Ernst J.
Published: March 2018

The distinct effects of the estrogen and progestin components of hormonal therapy on the metabolism of apolipoprotein (apo) B‐containing lipoproteins have not been studied. We enrolled eight healthy postmenopausal women in a placebo‐controlled, randomized, double‐blind crossover study. Each subject received placebo, conjugated equine estrogen (CEE, 0.625 mg/day) and CEE plus medroxyprogesterone acetate (MPA, 2.5 mg/day) for 8 weeks in a randomized order, with a 4‐week washout between phases. Main outcomes were the fractional catabolic rate (FCR) and production rate (PR) of apo B100 in triglyceride‐rich lipoproteins (TRL), intermediate‐density lipoproteins (IDL) and low ‐density lipoprotein (LDL) and of apo B48 in TRL.

Compared to placebo, CEE increased TRL apo B100 PR (p = 0.04). CEE also increased LDL apo B100 FCR (p = 0.02), but this effect was offset by a significant increase in LDL apo B100 PR (p = 0.04). Adding MPA to CEE negated the CEE effects resulting in no significant changes in TRL apo B100 PR and LDL apo B100 FCR and PR relative to placebo. Relative to placebo, during CEE there was a trend toward a reduction in plasma apo B48 concentrations and PR (p = 0.07 and p = 0.12, respectively). Compared with CEE, CEE + MPA significantly increased TRL apo B48 FCR (p = 0.02) as well as apo B48 PR (p = 0.01), resulting in no significant changes in apo B48 concentration.

Estrogen and progestin have independent and opposing effects on the metabolism of the atherogenic apo B100‐ and apo B48‐containing lipoproteins.
Thermally Sensitive N‐Type Thermoelectric Aniline Oligomer‐Block‐Polyethylene Glycol‐Block‐Aniline Oligomer ABA Triblock Copolymers
Authors: Cheng Xiang‐Le , Zhang Yun‐Fei , Wu Yan‐Guang , Fu Ping , Lin Zhi‐Dong , Du Fei‐Peng , Cheng Chun
Published: March 2018

High‐performance n‐type thermoelectric polymers are vital in the development of polymer thermoelectric generators (PTEGs). However, the progress is very slow due to their low stability and low thermoelectric properties. Here, aniline oligomer‐block‐polyethylene glycol‐block‐aniline oligomer (ANI)n‐b‐PEO‐b‐(ANI)n) (n = 4, 8, 16) are prepared and studied. The results indicate that the (ANI)n‐b‐PEO‐b‐(ANI)n show unique temperature sensitivity and switch from p‐type to n‐type when the temperature is above 300 K. Differential scanning calorimetry curves show that the Tg of the (ANI)n‐b‐PEO‐b‐(ANI)n is lower than 300 K, indicating that PEO segments of the (ANI)n‐b‐PEO‐b‐(ANI)n easily move above 300 K and have high flexibility. Temperature‐dependent Raman spectra confirm that there are strong interactions between PEO segments and aniline oligomers during the raising temperature, and PEO chains might provide plenty of negative charge at high temperature, which can convert the (ANI)n‐b‐PEO‐b‐(ANI)n into n‐type thermoelectric materials. To adjust the number of aniline unit, (ANI)8‐b‐PEO‐b‐(ANI)8 shows excellent n‐type characteristics with Seebeck coefficient as large as −1171 µV K−1 at 381 K. The strong interaction between PEO and aniline oligomers plays a dominant role in the n‐type thermoelectric performance of the triblock copolymers, which have potential application in the field of PTEGs and temperature sensors.
Using a kidney pump to perfuse a free filet flap for reconstruction after hemipelvectomy: A case report
Authors: Hinchcliff Katharine M. , Crockett Jessica , Thorpe Steven W. , Bayne Christopher O.
Published: March 2018

Long ischemia times adversely affect free flap survival, and large muscle flaps are particularly vulnerable. Hypothermic machine perfusion (HMP) is a well‐established method of organ preservation, and recent literature has detailed the use of HMP to extend free flap ischemia times, predominantly in the laboratory setting. One limitation in the study and adoption of free flap HMP has been the availability of standardized perfusion machinery, as thus far institutions have built their own devices. We present a case of a 75‐year‐old woman with dedifferentiated chondrosarcoma of her right proximal femur. She underwent a “spare parts” surgery using a filet flap from her lower leg. Due to an obligate long ischemia time between flap harvest and revascularization, a kidney transplant perfusion pump was used to flush and cool the flap. After completion of the disarticulation, free tissue transfer proceeded successfully. The patient had an uncomplicated post‐operative course until developing a local recurrence at three months post‐resection. We believe that the perfusion technology already created for solid organ transplant will have expanding indications in the future of free tissue transfer and limb replantation.
The Oral Bioavailability of Trans‐Resveratrol from a Grapevine‐Shoot Extract in Healthy Humans is Significantly Increased by Micellar Solubilization
Authors: Calvo‐Castro Laura A. , Schiborr Christina , David Franziska , Ehrt Heidi , Voggel Jenny , Sus Nadine , Behnam Dariush , Bosy‐Westphal Anja , Frank Jan
Published: March 2018

Scope

Grapevine‐shoot extract Vineatrol30 contains abundant resveratrol monomers and oligomers with health‐promoting potential. However, the oral bioavailability of these compounds in humans is low (˂1–2%). The aim of this study was to improve the oral bioavailability of resveratrol from vineatrol by micellar solubilization.

Methods and results

Twelve healthy volunteers (six women, six men) randomly ingested a single dose of 500 mg vineatrol (30 mg trans‐resveratrol, 75 mg trans‐ε‐viniferin) as native powder or liquid micelles. Plasma and urine were collected at baseline and over 24 h after intake. Resveratrol and viniferin were analyzed by HPLC. The area under the plasma concentration–time curve (AUC) and mean maximum plasma trans‐resveratrol concentrations were 5.0‐fold and 10.6‐fold higher, respectively, after micellar supplementation relative to the native powder. However, no detectable amounts of trans‐ε‐viniferin were found in either plasma or urine. The transepithelial permeability of trans‐resveratrol and trans‐ε‐viniferin across differentiated Caco‐2 monolayers was consistent to the absorbed fractions in vivo.

Conclusion

The oral bioavailability of trans‐resveratrol from the grapevine‐shoot extract Vineatrol30 was significantly increased using a liquid micellar formulation, without any treatment‐related adverse effects, making it a suitable system for improved supplementation of trans‐resveratrol.
A pencil beam algorithm for magnetic resonance image‐guided proton therapy
Authors: Padilla‐Cabal Fatima , Georg Dietmar , Fuchs Hermann
Published: March 2018

Purpose

The feasibility of magnetic resonance image (MRI)‐based proton therapy is based, among several other factors, on the implementation of appropriate extensions on current dose calculation methods. This work aims to develop a pencil beam algorithm (PBA) for dose calculation of proton beams within magnetic field regions of up to 3 T.

Methods

Monte Carlo (MC) simulations using the GATE 7.1/GEANT4.9.4p02 toolkit were performed to generate calibration and benchmarking data for the PBA. Dose distributions from proton beams in the clinical required energy range 60–250 MeV impinging on a 400 × 400 × 400 mm3 water phantom and transverse magnetic fields ranging from 0 to 3 T were considered. Energy depositions in homogeneous and heterogeneous phantoms filled with water, adipose, bone, and air were evaluated for proton energies of 80, 150, and 240 MeV, combining a trajectory calculation method and look‐up tables (LUT). A novel parametrization model, using independent tailed Gauss fitting functions, was employed to describe the nonsymmetric shape of lateral beam profiles. Integrated depth‐dose curves (IDD), lateral dose profiles, and two‐dimensional dose distributions calculated with the PBA were compared with results from MC simulations to assess the performance of the algorithm. A gamma index criterion of 2%/2 mm was used for analysis.

Results

A close to perfect agreement was observed for PB‐based dose calculations in water in magnetic fields of 0.5, 1.5, and 3 T. IDD functions showed differences between the PBA and MC of less than 0.1% before the Bragg peak, and deviations of 2–8% in the distal energy falloff region. Gamma index pass rates higher than 99% and mean values lower than 0.1 were encountered for all analyzed configurations. For homogeneous phantoms, only the full bone configuration offered deviations in the Bragg peak position of up to 1.7% and overestimations of the lateral beam spot width for high‐energy protons and magnetic field intensities. An excellent agreement between PBA and MC dose calculation was also achieved using slab‐like and lateral heterogeneous phantoms, with gamma index passing rates above 98% and mean values between 0.1 and 0.2. As expected, agreement reduced for high‐energy protons and high‐intensity magnetic fields, although results remained good enough to be considered for future implementation in clinical practice.

Conclusions

The proposed pencil beam algorithm for protons can accurately account for dose distortion effects induced by external magnetic fields. The application of an analytical model for dose estimation and corrections reduces the calculation times considerably, making the presented PBA a suitable candidate for integration in a treatment planning system.
Small‐Bowel Feeding Tube Placement at Bedside: Electronic Medical Device Placement and X‐Ray Agreement
Authors: Carter Michaelann , Roberts Susan , Carson Jo Ann
Published: March 2018

Background

The use of an electromagnetic placement device (EMPD) can allow trained clinicians to safely perform small‐bowel feeding tube (SBFT) placement at the bedside. Before initiation of enteral nutrition, most facilities require a radiology confirmation of tube placement. Requirement of X‐ray confirmation delays the start of nutrition and leads to increased costs and utilization of resources. The purpose of this study was to determine the rate of agreement between clinician interpretation of SBFT placement using the EMPD images and X‐ray confirmation on tip of SBFT placement.

Materials and Methods

This single‐center, retrospective, observational study used data completed by registered dietitians or registered nurses after SBFT placement and compared it with radiology reports in the electronic health record. All tube placements were performed using the EMPD and were determined to be in 1 of 4 locations: stomach, duodenum, at the ligament of Trietz, or not specified within the small bowel.

Results

A total of 280 tube placements were analyzed. When differentiating between stomach and small bowel, the rate of agreement using a κ statistic was substantial agreement (κ = 0.67) and when determining tip‐of‐tube location within the small bowel excluding not specified locations, there was almost perfect agreement with a κ = 0.93 and n = 84.

Conclusion

These findings suggest that EMPD images provide substantial agreement with X‐ray confirmation and almost perfect agreement when the tip of the tube is within the small bowel. This indicates that the EMPD could be used without X‐ray confirmation.
Clinical Simulation Learning for Small‐Bowel Feeding Tube Insertion
Authors: Rollins Christina , Bailey Emily , Gregoire Jacqueline , Milner Tim
Published: March 2018

Clinical simulation training provides a realistic environment for students and healthcare professionals to strengthen and broaden skills and abilities. This type of learning experience creates a controlled environment in which learners may attain new skills or further develop skills that positively impact patient outcomes. Although few studies exist regarding the use of clinical simulation training and nutrition support practitioners, preliminary data following a small‐bowel feeding tube (SBFT) insertion workshop for intensive care unit registered nurses and registered dietitian nutritionists showed potential use in this realm. The purpose of this paper is to provide a basic overview of clinical simulation learning, review literature related to clinical simulation in healthcare, and discuss the recent implementation of a SBFT insertion workshop incorporating clinical simulation learning.
Predicting the Influence of an Added Liquid in a Particle Damper using Coupled SPH and Discrete Element Method
Authors: Gnanasambandham Chandramouli , Eberhard Peter
Published: March 2018

Particle dampers are a promising alternative compared to conventional dampers due to their very flexible ability to dissipate energy in a wide frequency range even in rough environments. Simultaneously they cover additional functions like load bearing and noise reduction. For the understanding of particle dampers it is important to take into account the relevant physical phenomena which are interacting. The particles are modeled using the Discrete Element Method (DEM). Mesh‐free methods such as the DEM pose to be appropriate in modeling large displacements of particle fillings in the damper and the dynamic contacts between adjacent particles resulting from high dynamics. In this work, a numerical experiment, where a particle damper is attached to a vertical leaf‐spring, is set up to investigate the influence of typical parameters such as particle fill‐ratios, particle size, and enclosure geometry on the damping performance of the particle damper. Moreover, the effect of an added liquid is also investigated. The Smoothed Particle Hydrodynamics (SPH) method is used in order to model the motion of the fluid. By using a coupled SPH‐DEM approach, it is shown that complex interactions between particle‐fillings, liquid, and enclosure geometry can be sufficiently well modeled. Thereby, it is possible to predict the influence of an added liquid on the vibration attenuation properties of the particle damper. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear Multiple Body Models for Brake Squeal
Authors: Koch Sebastian , Gräbner Nils , Gödecker Holger , von Wagner Utz
Published: March 2018

Brake squeal is a self‐excited vibration with initially inclining amplitude reaching a limit cycle due to nonlinearities. For a proper simulation of this behavior, it is necessary to know the origin and the influence of the brake system's nonlinearities. It is generally known, that nonlinearities are inherent to the joints [1, 2], complex friction laws [3] and the friction material of the system [4–6]. In this work, the influence of friction material and shim nonlinearities on the existence of a limit cycle is investigated. Stiffness and damping characteristics are determined using the chair's owned DCTR [4] test rig. It is shown, how nonlinear characteristics, which are necessary for simulation, are obtained from the performed measurements. They are incorporated in a multiple body model composed of brake disk, pads, shims, carrier and calliper from which the nonlinear equations of motion are derived. For the investigation on the bifurcation behavior, the equations of motion are transformed into normal form. It is then possible to describe the bifurcation behavior with respect to parameter influences. Ultimately, with this information it is possible to show the influence of the investigated nonlinearities on brake squeal. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Using Fuzzy Arithmetic in Optimization Problems with Uncertain Constraints
Authors: Mäck Markus , Hose Dominik , Hanss Michael
Published: March 2018

A general procedure for the treatment of uncertain, fuzzy‐valued constraints in optimization problems is derived by considering the connection between fuzzy set theory and possibility theory, inspired by the results for chance‐constrained programming in a fuzzy environment [1]. The proposed algorithm is exemplarily applied to synthesizing a controller for an uncertain system. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Uncertainty in Friction Measurements
Authors: Ostermeyer G.‐P. , Mueller M. , Srisupattarawanit T. , Voelpel A.
Published: March 2018

In the fields of mechanical engineering, friction is ubiquitous. It is a fundamental cause of energy loss and wear. Another concern is the occurrence of comfort‐relevant friction induced vibrations. Prominent examples of this are NVH phenomena such as brake squeal, which is being investigated at great expense by the German automotive industry and academia, to determine its causes and potential influencing factors. For this purpose, numerous specialized measurements are performed, and models of varying complexity are used. All of these measurements and models have the common trait that the coefficient of friction (COF), defined as the ratio of the tangential force and normal force, has a decisive influence on the systems' stability. To parameterize the friction coefficient in macroscopic models, measurements must be performed. In this case, often an average value over time and over various loading procedures is used. As the measurements reveal, the coefficient of friction is in reality not constant, but is subject to a high degree of dynamics on various time scales, caused by complex processes in the boundary layer. A treatment of the coefficient of friction as a steady‐state parameter, or even as a constant, is thus a major reduction. The large variability of the coefficient of friction causes a corresponding variance in the stability limits of the models considered. This phenomenon is observed in the real world, where squealing seems to have a non‐deterministic behavior. This suggests uncertainties in the modeling of the friction coefficient. Due to the various types of uncertainty (variability, incompleteness and inaccuracy), the entire problem is a matter of polymorphic uncertainty. This paper focuses on the modeling of the friction coefficient, taking into account the various causes of uncertainty. Selections of raw data obtained at the authors institute throughout many years of research on friction phenomena in brake systems will be evaluated and classified with respect to its uncertainty properties. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational formulation with error estimates for uncertainty quantification via collocation, regression, and sprectral projection
Authors: Rang Joachim , Matthies Hermann G.
Published: March 2018

Many real world problems need simplifications in such a way that computing is reduced for answering specific questions, for example, to quantify uncertainties. Therefore so‐called metamodels or surrogate models are developed which are based on interpolation or approximation methods. In this paper we transform the usual approximation or interpolation problem into a variational form such as it is known from the Finite Element method (FEM). With this variational framework it is possible to derive error estimators, which can be used later on for adaptivity. To compute the coefficients of the metamodel one needs some quadrature rules, which should be related to the given data. A numerical example shows the advantages of our proposed methods. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A mechanism‐based homogenization strategy for the determination of flow stress and strain hardening
Authors: Schulz Katrin , Sudmanns Markus
Published: March 2018

The high demand for physically‐based continuum models of plasticity has induced renewed efforts to formulate continuum theories of dislocation kinematics and dynamics. Considering a dislocation density based model incorporating a set of evolution equations for arbitrary curved dislocation lines, the kinetic formulation of a velocity law of dislocation motion including dislocation interaction between different slip systems is investigated. Two short‐range interaction terms accounting for forest interactions are comparatively discussed and differences are pointed out. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Turbulent and transitional sidewall jets in magnetohydrodynamic channels with a homogeneous magnetic field
Authors: Krasnov Dmitry , Boeck Thomas , Bühler Leo
Published: March 2018

Liquid metal flows in the presence of a uniform magnetic field experience electromagnetic induction. The eddy currents and associated Lorentz force density modify the flow and give rise to thin electromagnetic boundary layers on the walls of the channel or duct. Hartmann layers develop on the walls perpendicular to the magnetic field whereas side layers develop on the parallel walls. The structure of the laminar flow depends on the conductivity of the walls. The side layers play a critical role in the transition to turbulence and are also strongly affected by the anisotropic character of the Lorentz force. We focus on duct flows with conducting Hartmann walls that give rise side‐layers jets and report numerical studies of the transitional and turbulent regimes. We also examine one‐point statistics and describe specific transitional patterns. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Moreau‐type integrators based on the time finite element discretization of the virtual action
Authors: Capobianco Giuseppe , Eugster Simon R. , Leine Remco I.
Published: March 2018

In this paper, we derive and compare three integrators for nonsmooth mechanical systems by discretizing the principle of virtual action with finite elements in time. The weak as well as the strong variational form of the principle are discretized using a piecewise linear shape function and different quadrature rules. After introducing a suitable constitutive law for the contact forces arising in the discretized system, this approach leads to the well established time‐stepping scheme of Moreau [1], the variational Moreau‐type scheme derived in [3] and another related scheme, which we call the symmetric Moreau‐type scheme. It is shown using a benchmark system that the symmetric and the variatonal Moreau‐type schemes, in contrast to Moreau's scheme, show an excellent longterm energy behavior. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Dynamical Analysis of a Tip Balancing Cube
Authors: Gattringer Hubert , Reiter Alexander , Stöger Christoph , Jörgl Matthias , Müller Andreas
Published: March 2018

This paper discusses some dynamical aspects of a self‐balancing Inertia Wheel Cube (IWC). The acceleration and deceleration of actuated flywheels is used to stabilize the IWC when balancing on one of its corners, which is an unstable equilibrium position. The orientation as well as the rotational velocity of the device are measured by an inertial measurement unit (IMU). The equations of motions are derived with the Projection Equation. Using the rotational velocity of the IWC as part of the generalized velocities leads to well‐structured and interpretable dynamical equations. These equations are the basis for simulation, parameter identification, control synthesis, and stability analysis. The stability of the unstable equilibrium is investigated by means of the linearized motion equations. It can be shown that there are always uncontrollable states by invoking the conservation of momentum. Simulations as well as experimental results are presented. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A novel approach to Lie group structured configuration spaces of rigid bodies
Authors: Hante Stefan , Arnold Martin
Published: March 2018

In rigid body mechanics, a body's configuration consisting of orientation and position have to be described, as well as angular velocity and velocity. There are several different ways to do this, leading to different configuration spaces. Popular choices include SO(3) × ℝ3, SE(3) or unit dual quaternions. All these configuration spaces possess a Lie group structure. We present the novel approach 𝕊 ⋉ ℝ3, which is a configuration space similar to SE(3), but describes the orientation in terms of unit quaternions instead of rotation matrices. Furthermore we show its relation to and advantages over other configuration spaces. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A homogenisation method for the multiscale modelling of transversely isotropic skeletal muscle tissue
Authors: Bleiler Christian , Ponte Castañeda Pedro , Röhrle Oliver
Published: March 2018

Skeletal muscle tissue shows a wide variation in its mechanical response for different persons or different muscle types of one single person. These distinct mechanical properties are due to variations in the microstructure of the material. For skeletal muscles, especially the arrangement and the stiffness of collagen fibres in the connective tissue define the macroscopic passive stiffness, while the sarcomeres (contractile units) enable an active contractility of the muscles. Phenomenological models lack the ability to take into account such microstructural variations in a natural way and need to be fitted to experimental data, which is, however, not available for every desired muscle type. Thus, this work presents a homogenisation‐based multiscale model for skeletal muscle tissue which enables to include microstructural properties in a continuum‐mechanical framework. The underlying homogenisation is done by means of the tangent‐second‐order (TSO) method, which is appropriately extended in order to account for the transversely isotropic behaviour of the muscle material. Moreover, an angular‐integration model is embedded for a comprehensive description of the connective tissue. Concluding, the presented model allows to directly include microstructural‐based material properties on the continuum‐mechanical macroscale and yet avoids the expensiveness of computational homogenisation methods, like FE2, by using well‐founded analytical homogenisation techniques. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Emergence of aortic aneurysms due to failure of adhesive bonds between proteoglycans
Authors: Hillgärtner Markus , Linka Kevin , Itskov Mikhail
Published: March 2018

Aortic aneurysms are a common disease among older patients. Aneurysm ruptures cause more than 150 000 deaths annually [2]. One of the main risk factors which lead to the abnormal enlargements of vessels (>150% of original size) is arterial hypertension.

This contribution presents a modeling approach, where the cyclic loading of the artery caused by the blood pressure leads to fatigue inside the arterial wall. The arterial wall is considered as a composite material, where a matrix (ground substance) is reinforced by collagen fibers consisting of fibrils connected by proteoglycan (PG) bridges. These PG bridges support interfibrillar sliding leading to lower fibril stretch [6]. Molecular adhesive bonds rupture under any pulling force if the force is held sufficiently long enough [1]. This rupturing over time leads to a decrease in the density of PG bridges, higher stretches in the fibrils, more damage inside the fibrils and finally to fatigue of the soft tissue which causes the abnormal enlargement.

Finally the model is compared against experimental data of uniaxial tension tests and used in a FEM simulation to study the emergence of aortic aneurysms under arterial hypertension. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Three‐dimensional finite element modeling of dental restorative procedures using various digitization methods
Authors: Joedecke Paul , Guentsch Arndt , Naumenko Konstantin , Weber Christian‐Toralf
Published: March 2018

The objective of the presented paper is to compare the usage of different digitization methods to generate finite element models of dental structures and restorations. Four different virtual models were generated by using intraoral‐, CBCT‐, CT‐ and micro‐CT datasets. Subsequently there were compared due to their field of view (FOV), accuracy and radiation exposure for the patients. Depending on the specific application all four virtual models showed a qualitative and quantitative correlation associated with in‐vitro and in‐vivo studies. Further the influence of artifacts and application limits were classified with weight functions for the use in a database. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling the contraction properties of smooth muscle cells in bladder tissue
Authors: Seydewitz Robert , Morales‐Orcajo Enrique , Böl Markus
Published: March 2018

The major function of the urinary bladder is the storage and release of urine. Undergoing large deformations while keeping the chemically aggressive urine and maintaining a relatively constant pressure during filling, the bladder shows remarkable mechanical properties. Those properties are based on the highly complex structure of the bladder wall. However, irregularities within the bladder wall may have negative implications on the correct functioning. In order to improve the understanding of different physiological processes taking place within the bladder wall during bladder filling and contraction, a computation tool is presented based on a continuum mechanics approach. In that sense the model is applied to complex boundary value problems. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Large time increment approach for fatigue damage computations
Authors: Alameddin Shadi , Bhattacharyya Mainak , Fau Amelie , Nackenhorst Udo , Néron David , Ladevèze Pierre
Published: March 2018

This contribution focuses on the use of a new method to reduce the computational demands of fatigue damage computations using continuum damage mechanics. The LArge Time INcrement (LATIN) method incorporates a model order reduction approach namely the proper generalised decomposition (PGD). LATIN has been extended to tackle damage problems. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Variational framework for phase field modeling of ductile fracture in porous solids at finite strains
Authors: Teichtmeister Stephan , Kienle Daniel , Aldakheel Fadi , Miehe Christian
Published: March 2018

This work outlines a rigorous variational‐based framework for the phase field modeling of fracture in isotropic and anisotropic porous solids undergoing small elastic but large plastic deformations. It extends the recent work [1] to a formulation of porous plasticity with particulate microstructures characterized by spherical pores or by ellipsoidal voids, which additionally undergo a change in size and orientation. A gradient plasticity model for isotropic and anisotropic porous plasticity is developed, and linked to a failure criterion in terms of the local elastic‐plastic work density that drives the fracture phase field [2]. It is shown that this approach is able to model phenomena of ductile failure such as cup‐cone failure surfaces. The proposed model is governed by a rate‐type minimization principle, which describes the coupled multifield evolution problem of plasticity‐damage. Another aspect is the regularization towards a micromorphic gradient plasticity‐damage setting which enhances the robustness of the finite element formulation. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time‐harmonic analysis of cracks in functionally graded piezoelectric materials
Authors: Wünsche Michael , Sladek Jan , Sladek Vladimir , Zhang Chuanzeng
Published: March 2018

Modern piezoelectric structures offer certain performance advantages over conventional ones due to their capability of converting electrical energy into mechanical energy and vice versa. In recent years composites with a continuously change of the material properties are getting increasing attention in advanced engineering applications. An important advantage over conventional laminates is that interfaces and stress discontinuities are avoided. Piezoelectric composites are very brittle and have a low fracture toughness. The analysis of functionally graded materials (FGMs) is mathematically complex and analytical solutions are possible only for very simple geometry and loading conditions. Therefore, efficient numerical methods are needed to solve more general problems. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Nonlinear analysis of solids in boundary representation – a NURBS based Galerkin method
Authors: Chasapi Margarita , Klinkel Sven , Simeon Bernd
Published: March 2018

The contribution presents a new numerical method to solve nonlinear problems of solids in boundary representation. A formulation for material nonlinearities is derived. The proposed method introduces an approach where the geometrical description of the boundary is sufficient to define the complete solid. While the interior of the domain is described by a radial scaling parameter, the scaling of the boundary with respect to the specified scaling center leads to the complete solid. This idea fits perfectly to the boundary representation modeling technique commonly employed in CAD. The approach exploits the tensor‐product structure of the solid to parameterize the physical domain, i.e., two‐dimensional surfaces are represented by NURBS objects, which parameterize the boundary surfaces. Following the isogeometric paradigm, the NURBS functions that describe the boundary of the geometry form also the basis for the approximation of the displacement at the boundary. The displacement response in the circumferential and radial scaling direction is approximated by one‐dimensional NURBS. The present formulation accounts for material nonlinearity with elasto‐plastic behavior, where small strain theory is assumed. Similar to the Scaled Boundary Finite Element Method (SB‐FEM), the structure is parameterized by a radial scaling parameter that emanates from a scaling center and a parameter in circumferential direction along the boundary. The Galerkin projection of the weak form yields a system of equilibrium equations whose solution gives rise to the displacement response. Due to the nonlinear relation between the stress and the strain, the linear equilibrium equation is not applicable anymore. Applying the weak form in the circumferential and radial direction leads to a nonlinear equation with respect to the unknown displacement response, which is solved with a linearization and the Newton‐Raphson scheme. The applicability of the proposed formulation is shown by means of numerical examples. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Dual Craig‐Bampton State‐Space Approach for Model Reduction of Damped Systems
Authors: Gruber Fabian M. , Rixen Daniel J.
Published: March 2018

The dual Craig‐Bampton method for the reduction of undamped systems is modified for the case of general viscous damping. The final reduction is based on the use of complex free interface normal modes, (residual) flexibility modes and state‐space rigid body modes. For the coupling of the substructures in state‐space representation, a dual coupling procedure based on the interface forces between adjacent substructures is used that is novel compared to other methods that commonly apply primal coupling procedures. (© 2017 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)