bluuebunny/crossref_metadata_2025 huggingface dataset:
Trends in chemoradiation use in elderly patients with head and neck cancer: Changing treatment patterns with cetuximab
Authors: Baxi Shrujal S. , O'Neill Caitriona , Sherman Eric J. , Atoria Coral L. , Lee Nancy Y. , Pfister David G. , Elkin Elena B.
Published: December 2014

Background

Cetuximab was approved for use in chemoradiation therapy (CRT) for locally advanced head and neck squamous cell carcinoma (HNSCC) in 2006.

Methods

Among 3705 patients with locally advanced HNSCC identified in the linked Surveillance Epidemiology and End Results (SEER) Medicare database, we assessed treatment trends, including surgery, radiation therapy (RT), CRT, and specific agents used in CRT. We examined the influence of demographic and clinical characteristics on the likelihood of receiving CRT before and after 2006.

Results

Chemoradiation use increased from 29% of patients diagnosed in 2001 to 61% in 2009 (p < .0001). Compared to before 2006, neither age nor comorbidity score was associated with receipt of CRT after 2006. Platinum combinations were the most commonly used concurrent chemotherapies before 2006, but, since then, cetuximab has become the most commonly used agent.

Conclusion

The use of CRT has increased substantially and cetuximab may have increased CRT use, especially in older and sicker patients. © 2015 Wiley Periodicals, Inc. Head Neck 38: E165–E171, 2016
Frequency and phenotypic spectrum of germline mutations in POLE and seven other polymerase genes in 266 patients with colorectal adenomas and carcinomas
Authors: Spier Isabel , Holzapfel Stefanie , Altmüller Janine , Zhao Bixiao , Horpaopan Sukanya , Vogt Stefanie , Chen Sophia , Morak Monika , Raeder Susanne , Kayser Katrin , Stienen Dietlinde , Adam Ronja , Nürnberg Peter , Plotz Guido , Holinski‐Feder Elke , Lifton Richard P. , Thiele Holger , Hoffmann Per , Steinke Verena , Aretz Stefan
Published: December 2014

In a number of families with colorectal adenomatous polyposis or suspected Lynch syndrome/HNPCC, no germline alteration in the APC, MUTYH, or mismatch repair (MMR) genes are found. Missense mutations in the polymerase genes POLE and POLD1 have recently been identified as rare cause of multiple colorectal adenomas and carcinomas, a condition termed polymerase proofreading‐associated polyposis (PPAP). The aim of the present study was to evaluate the clinical relevance and phenotypic spectrum of polymerase germline mutations. Therefore, targeted sequencing of the polymerase genes POLD1, POLD2, POLD3, POLD4, POLE, POLE2, POLE3 and POLE4 was performed in 266 unrelated patients with polyposis or fulfilled Amsterdam criteria. The POLE mutation c.1270C>G;p.Leu424Val was detected in four unrelated patients. The mutation was present in 1.5% (4/266) of all patients, 4% (3/77) of all familial cases and 7% (2/30) of familial polyposis cases. The colorectal phenotype in 14 affected individuals ranged from typical adenomatous polyposis to a HNPCC phenotype, with high intrafamilial variability. Multiple colorectal carcinomas and duodenal adenomas were common, and one case of duodenal carcinoma was reported. Additionally, various extraintestinal lesions were evident. Nine further putative pathogenic variants were identified. The most promising was c.1306C>T;p.Pro436Ser in POLE. In conclusion, a PPAP was identified in a substantial number of polyposis and familial colorectal cancer patients. Screening for polymerase proofreading mutations should therefore be considered, particularly in unexplained familial cases. The present study broadens the phenotypic spectrum of PPAP to duodenal adenomas and carcinomas, and identified novel, potentially pathogenic variants in four polymerase genes.
All‐cause mortality increased by environmental cadmium exposure in the Japanese general population in cadmium non‐polluted areas
Authors: Suwazono Yasushi , Nogawa Kazuhiro , Morikawa Yuko , Nishijo Muneko , Kobayashi Etsuko , Kido Teruhiko , Nakagawa Hideaki , Nogawa Koji
Published: December 2014

The aim of the present study was to evaluate the effect of environmental cadmium (Cd) exposure indicated by urinary Cd on all‐cause mortality in the Japanese general population. A 19‐year cohort study was conducted in 1067 men and 1590 women aged 50 years or older who lived in three cadmium non‐polluted areas in Japan. The subjects were divided into four quartiles based on creatinine adjusted U‐Cd (µg g−1 cre). The hazard ratio (HR) and 95% confidence interval (CI) for continuous U‐Cd or the quartiles of U‐Cd were estimated for all‐cause mortality using a proportional hazards regression.The all‐cause mortality rates per 1000 person years were 31.2 and 15.1 in men and women, respectively. Continuous U‐Cd (+1 µg g−1 cre) was significantly related to the all‐cause mortality in men (HR 1.05, 95% CI: 1.02–1.09) and women (HR 1.04, 95% CI: 1.01–1.07). Furthermore in men, the third (1.96–3.22 µg g−1 cre) and fourth quartile (≥3.23 µg g−1 cre) of U‐Cd showed a significant, positive HR (third: HR 1.35, 95% CI: 1.03–1.77, fourth: HR 1.64, 95% CI: 1.26–2.14) for all‐cause mortality compared with the first quartile (<1.14 µg g−1 cre). In women, the fourth quartile of U‐Cd (≥4.66 µg g−1 cre) also showed a significant HR (1.49, 95% CI 1.11–2.00) for all‐cause mortality compared with the first quartile (<1.46 µg g−1 cre).In the present study, U‐Cd was significantly associated with increased mortality in the Japanese general population, indicating that environmental Cd exposure adversely affects the life prognosis in Cd non‐polluted areas in Japan. Copyright © 2014 John Wiley & Sons, Ltd.
Tl(I) and Tl(III) alter the expression of EGF‐dependent signals and cyclins required for pheochromocytoma (PC12) cell‐cycle resumption and progression
Authors: Pino María T. L. , Verstraeten Sandra V.
Published: December 2014

The effects of thallium [Tl(I) and Tl(III)] on the PC12 cell cycle were evaluated without (EGF−) or with (EGF+) media supplementation with epidermal growth factor (EGF). The following markers of cell‐cycle phases were analyzed: cyclin D1 (G1); E2F‐1, cyclin E and cytosolic p21 (G1→S transition); nuclear PCNA and cyclin A (S); and cyclin B1 (G2). The amount of cells in each phase and the activation of the signaling cascade triggered by EGF were also analyzed. Tl(I) and Tl(III) (5–100 μM) caused dissimilar effects on PC12 cell proliferation. In EGF− cells, Tl(I) increased the expression of G1→S transition markers and nuclear PCNA, without affecting cyclin A or cyclin B1. In addition to those, cyclin B1 was also increased in EGF+ cells. In EGF− cells, Tl(III) increased the expression of cyclin D1, all the G1→S and S phase markers and cyclin B1. In EGF+ cells, Tl(III) increased cyclin D1 expression and decreased all the markers of G1→S transition and the S phase. Even when these cations did not induce the activation of EGF receptor (EGFR) in EGF− cells, they promoted the phosphorylation of ERK1/2 and Akt. In the presence of EGF, the cations anticipated EGFR phosphorylation without affecting the kinetics of EGF‐dependent ERK1/2 and Akt phosphorylation. Altogether, results indicate that Tl(I) promoted cell proliferation in both EGF− and EGF+ cells. In contrast, Tl(III) promoted the proliferation of EGF− cells but delayed it in EGF+ cells, which may be related to the toxic effects of this cation in PC12 cells. Copyright © 2014 John Wiley & Sons, Ltd.
PTH Signaling During Exercise Contributes to Bone Adaptation
Authors: Gardinier Joseph D , Mohamed Fatma , Kohn David H
Published: December 2014

Improving the structural integrity of bone reduces fracture risk and development of osteoporosis later in life. Exercise can increase the mechanical properties of bone, and this increase is often attributed to the dynamic loading created during exercise. However, the increase in systemic parathyroid hormone (PTH) levels during exercise gives reason to hypothesize that PTH signaling also regulates bone adaptation in response to exercise. Therefore, the first aim of this study was to establish the impact PTH signaling has on bone adaptation during exercise by inhibiting PTH signaling with PTH(7-34); the second aim was to determine whether increasing PTH levels during exercise with PTH(1-34) can augment bone adaptation. Thirty minutes after a single bout of running on a treadmill, mice exhibited a twofold increase in systemic PTH levels. Under the same exercise regimen, the influence of PTH signaling on bone adaptation during exercise was then evaluated in mice after 21 consecutive days of exercise and treatment with PTH(7-34), PTH(1-34), or vehicle. Exercise alone caused a significant increase in trabecular bone volume with adaptation to a more platelike structure, which was inhibited with PTH(7-34) during exercise. Changes in structural-level and tissue-level mechanical properties during exercise occurred in the absence of significant changes to cortical bone geometry. Inhibition of PTH signaling during exercise attenuated the changes in structural-level mechanical properties, but not tissue-level properties. Enhanced PTH signaling during exercise with PTH(1-34) increased trabecular and cortical bone volume, but had little effect on the structural-level and tissue-level mechanical properties compared to exercise alone. Our study is the first to demonstrate that bone adaptation during exercise is not only a function of dynamic loading, but also PTH release, and that PTH signaling contributes differently at the structural and tissue levels. © 2015 American Society for Bone and Mineral Research.
Bone Volume Fraction and Fabric Anisotropy Are Better Determinants of Trabecular Bone Stiffness Than Other Morphological Variables
Authors: Maquer Ghislain , Musy Sarah N , Wandel Jasmin , Gross Thomas , Zysset Philippe K
Published: December 2014

As our population ages, more individuals suffer from osteoporosis. This disease leads to impaired trabecular architecture and increased fracture risk. It is essential to understand how morphological and mechanical properties of the cancellous bone are related. Morphology-elasticity relationships based on bone volume fraction (BV/TV) and fabric anisotropy explain up to 98% of the variation in elastic properties. Yet, other morphological variables such as individual trabeculae segmentation (ITS) and trabecular bone score (TBS) could improve the stiffness predictions. A total of 743 micro–computed tomography (μCT) reconstructions of cubic trabecular bone samples extracted from femur, radius, vertebrae, and iliac crest were analyzed. Their morphology was assessed via 25 variables and their stiffness tensor (CFE) was computed from six independent load cases using micro finite element (μFE) analyses. Variance inflation factors were calculated to evaluate collinearity between morphological variables and decide upon their inclusion in morphology-elasticity relationships. The statistically admissible morphological variables were included in a multiple linear regression model of the dependent variable CFE. The contribution of each independent variable was evaluated (ANOVA). Our results show that BV/TV is the best determinant of CFE(r2adj = 0.889), especially in combination with fabric anisotropy (r2adj = 0.968). Including the other independent predictors hardly affected the amount of variance explained by the model (r2adj = 0.975). Across all anatomical sites, BV/TV explained 87% of the variance of the bone elastic properties. Fabric anisotropy further described 10% of the bone stiffness, but the improvement in variance explanation by adding other independent factors was marginal (<1%). These findings confirm that BV/TV and fabric anisotropy are the best determinants of trabecular bone stiffness and show, against common belief, that other morphological variables do not bring any further contribution. These overall conclusions remain to be confirmed for specific bone diseases and postelastic properties. © 2015 American Society for Bone and Mineral Research.
MicroRNA-140 Provides Robustness to the Regulation of Hypertrophic Chondrocyte Differentiation by the PTHrP-HDAC4 Pathway
Authors: Papaioannou Garyfallia , Mirzamohammadi Fatemeh , Lisse Thomas S , Nishimori Shigeki , Wein Marc N , Kobayashi Tatsuya
Published: December 2014

Growth plate chondrocytes go through multiple differentiation steps and eventually become hypertrophic chondrocytes. The parathyroid hormone (PTH)-related peptide (PTHrP) signaling pathway plays a central role in regulation of hypertrophic differentiation, at least in part, through enhancing activity of histone deacetylase 4 (HDAC4), a negative regulator of MEF2 transcription factors that drive hypertrophy. We have previously shown that loss of the chondrocyte-specific microRNA (miRNA), miR-140, alters chondrocyte differentiation including mild acceleration of hypertrophic differentiation. Here, we provide evidence that miR-140 interacts with the PTHrP-HDAC4 pathway to control chondrocyte differentiation. Heterozygosity of PTHrP or HDAC4 substantially impaired animal growth in miR-140 deficiency, whereas these mutations had no effect in the presence of miR-140. miR-140–deficient chondrocytes showed increased MEF2C expression with normal levels of total and phosphorylated HDAC4, indicating that the miR-140 pathway merges with the PTHrP-HDAC4 pathway at the level of MEF2C. miR-140 negatively regulated p38 mitogen-activated protein kinase (MAPK) signaling, and inhibition of p38 MAPK signaling reduced MEF2C expression. These results demonstrate that miR-140 ensures the robustness of the PTHrP/HDAC4 regulatory system by suppressing MEF2C-inducing stimuli. © 2014 American Society for Bone and Mineral Research © 2015 American Society for Bone and Mineral Research
Downregulation of Connexin 32 Attenuates Hypoxia/Reoxygenation Injury in Liver Cells
Authors: Wang Ren , Huang Fei , Chen Zhangyan , Li Shangrong
Published: December 2014

Gap junction intercellular communication is involved in ischemia–reperfusion (IR) injury of organs. Connexins are proteins that are critical to the function of gap junctions. To clarify the role of gap junctions in IR injury in liver cells, the function of gap junctions was modulated in an in vitro hypoxia/reoxygenation (H/R) model. BRL‐3A rat liver cells, endogenously expressing connexins Cx32 and Cx43, were used to model the process of hepatic IR injury. Suppression of gap junction activity was achieved genetically, using Cx32‐specific small interfering RNA (siRNA), or chemically, with pharmacological inhibitors, oleamide, and 18‐α‐GA. BRL‐3A cells subjected to H/R exhibited reduced cell survival and pathologies indicative of IR injury. Cx32‐specific siRNA, oleamide, and 18‐α‐GA, respectively, decreased gap junction permeability, as assessed by the parachute assay. Pretreatment with Cx32‐specific siRNA increased cell survival. Pretreatment with oleamide or 18‐α‐GA did not improve cell survival. Modulating gap junction by Cx32 gene silencing protected BRL‐3A liver cells from H/R.
M&A Deal‐Makers Are Dealing in 2014: A Commentary
Authors: Edwards James B.
Published: December 2014

A stampede of merger and acquisition (M&A) transactions took place during the first six months of 2014. Whether this means growth ahead or irrationality remains to be seen. What hasn't changed is that the true measure of M&A activities will always be measured by the resulting economic growth. The game of “musical chairs” serves best when it leads to increased productivity and new jobs. When it creates some degree of monopoly and restraint on the consumer, it's bad news for our economic well‐being.© 2015 Wiley Periodicals, Inc.
Categories That Should Be Removed From Mental Disorders Classifications: Perspectives and Rationales of Clinicians From Eight Countries
Authors: Robles Rebeca , Fresán Ana , Medina‐Mora María Elena , Sharan Pratap , Roberts Michael C. , de Jesus Mari Jair , Matsumoto Chihiro , Maruta Toshimasa , Gureje Oye , Ayuso‐Mateos José Luís , Xiao Zeping , Reed Geoffrey M.
Published: December 2014

Objective

To explore the rationales of mental health professionals (mainly psychiatrists and psychologists) from 8 countries for removing specific diagnostic categories from mental disorders classification systems.

Method

As part of a larger study, 505 participants indicated which of 60 major disorders should be omitted from mental disorders classification systems and provided rationales. Rationale statements were analyzed using inductive content analysis.

Results

The majority of clinicians (60.4%) indicated that 1 or more disorders should be removed. The most common rationales were (a) problematic boundaries between normal and psychopathological conditions (45.9% of total removal recommendations), (b) problematic boundaries among mental disorders (25.4%), and (c) problematic boundaries between mental and physical disorders (24.0%). The categories most frequently recommended for deletion were gender identity disorder, sexual dysfunction, and paraphilias, usually because clinicians viewed these categories as being based on stigmatization of a way of being and behaving. A range of neurocognitive disorders were described as better conceptualized as nonpsychiatric medical conditions. Results were analyzed by country and country income level. Although gender identity disorder was the category most frequently recommended for removal overall, clinicians from Spain, India, and Mexico were most likely to do so and clinicians from Nigeria and Japan least likely, probably because of social and systemic factors that vary by country. Systematic differences in removal rationales by country income level may be related to the development, structure, and functioning of health systems.

Conclusion

Implications for development and dissemination of the classification of mental and behavioral disorders in WHO's ICD‐11 are discussed.
Parental Relationships and Behavioral Approach System Dysregulation in Young Adults With Bipolar Disorder
Authors: Muralidharan Anjana , Kotwicki Raymond J. , Cowperthwait Colleen , Craighead W. Edward
Published: December 2014

Objectives

Expressed emotion (EE), or the presence of criticism/hostility/emotional overinvolvement in a family relationship, predicts poorer outcomes in bipolar disorder; however, the mechanism of this is unclear. The present study investigated whether, in a sample of young adults (aged 18–40 years) with bipolar disorder, parental criticism was associated with Behavioral Approach System (BAS) dysregulation, including emotional reactivity to negative feedback and cognitive schemas of self‐criticism/perfectionism.

Method

Twenty‐two young adults with bipolar I disorder and 22 matched control participants completed an interview, questionnaires, and a computer‐based task with false negative feedback; emotional reactivity to this feedback was assessed.

Results

Compared to control participants, clinical participants exhibited higher levels (p = 0.001) of self‐criticism, and a trend towards a greater decrease in positive affect after negative feedback (p = 0.053), even when controlling for mood symptoms. Among clinical participants, perceived criticism from paternal caregivers was associated with self‐criticism and perfectionism, and low perceived paternal care was associated with decrease in positive affect.

Conclusion

Strain in parental relationships may be associated with BAS dysregulation for individuals with bipolar disorder.
Methanol feeding strategy design enhances recombinant human growth hormone production by Pichia pastoris
Authors: Güneş Hande , Boy Erdem , Ata Özge , Zerze Gül H , Çalık Pınar , Özdamar Tunçer H
Published: December 2014

BACKGROUND

The effects of designed methanol and co‐substrate feeding strategies on fed‐batch recombinant human growth hormone (rhGH) production by Pichia pastoris hGH‐Mut+ were investigated.

RESULTS

The highest cell concentration was obtained as 157 g L−1 with the exponential feeding strategy where methanol was fed at a pre‐calculated feeding rate based on pre‐determined µ0 = 0.03 h−1, and mannitol concentration was kept constant at 50 g L−1 for t=0–6 h. The highest rhGH concentration was obtained as 1.3 g L−1 at t=54 h with the methanol‐stat feeding strategy, where no co‐substrate was used and the methanol concentration was kept at 5 g L−1 in the medium during the production phase. Thereafter, in another methanol‐stat feeding strategy with pulse‐fed sorbitol, the highest rhGH concentration was obtained as 1.2 g L−1 at t=42 h.

CONCLUSION

The methanol‐stat fed‐batch method keeping methanol concentration constant at 5 g L−1 in the production medium increased rhGH production at least 2‐fold compared with that of the exponential feeding strategies. In the designed methanol‐stat feeding strategies, use of sorbitol as co‐substrate decreased methanol demand of the cells 2‐fold, increased the overall product yield on the substrate 1.6‐fold, shortened the cultivation time by 12 h and increased the productivity. Thus, methanol‐stat feeding with co‐substrate sorbitol was found to be a favorable fed‐batch strategy for rhGH production by Pichia pastoris under alcohol oxidase I promoter. © 2014 Society of Chemical Industry
The Structures of Uncommon Cationic N‐alkenyl Purine and Pyrimidine Bases
Authors: Kociok‐Köhn Gabriele , Molloy Kieran C. , Price Gareth J. , Smith Douglas R. G.
Published: December 2014

The structures of 1,3 bis‐(allyl)cytosinium bromide (1), 7,9 bis‐(allyl)adeninium bromide hydrate (2) and 3‐(butenyl)adeninium bromide (3) have been determined. 1 is dimeric via N―H…Br hydrogen bonds, which further associate into ribbons via weaker C―H…Br interactions. 2 is also dimeric, now from N―H…N hydrogen bonds, which build up further through a complex array of hydrogen bonds involving both the anion and water of crystallization (O―H…N, O―H…Br, C―H…Br). 3 does not dimerise but forms polymeric sheets via a series of N―H…N, C―H…N and C―H…Br hydrogen bonds.
Perhydroxylcucurbit[6]uril as a highly selective gas chromatographic stationary phase for analytes of wide‐ranging polarity
Authors: Sun Tao , Qi Meiling , Fu Ruonong
Published: December 2014

This work describes the separation performance of a perhydroxylcucurbit[6]uril stationary phase for capillary gas chromatography. The perhydroxylcucurbit[6]uril stationary phase exhibits higher resolving capabilities for critical analytes with better peak shapes than cucurbit[6]uril and conventional stationary phases. The advantageous separation feature of the perhydroxylcucurbit[6]uril stationary phase may originate from its unique structure and favorably balanced interactions with the analytes. Also, the perhydroxylcucurbit[6]uril column shows good separation repeatability with relative standard deviations in the range of 0.01–0.13% for intraday, 0.37–0.82% for interday, and 1.0–4.7% for column‐to‐column repeatability.
The Effect of Landscape Conservation Measures in Changing Landscape Patterns: A Case Study in Mediterranean Mountains
Authors: Lasanta Teodoro , Nadal‐Romero Estela , Errea Paz , Arnáez José
Published: December 2014

Mediterranean mountain landscapes have high ecological and cultural values. However, since 1950, a large number of these landscapes have been subject to degradation as a consequence of land abandonment. Some regional administrations have enacted measures that favour the regeneration of pasturelands through scrubland clearing. The aim of this study was to evaluate the consequences of clearing and the regeneration of pasturelands on landscape structure and the recovery of extensive livestock in La Rioja. The results indicate that between 1986 and 2011 an area of 29,659 ha was cleared in the mountains of La Rioja, although 62·6% of this was cleared in the period 2000–2011. In 1956, the landscape was dominated by cultivated fields, but by 2001, much of the agricultural area had been abandoned and replaced by scrubland, natural woods and reforested areas. Furthermore, the landscape was more fragmented in 1956 than in 2001. The landscape structure varied following clearing, with a doubling in the number of patches and an increase in heterogeneity. The consequences of clearing have included an increase in the area of pastureland and the number of large animals. In addition, the number of farms has decreased, but their mean size has increased. Clearing is an appropriate way for spatial reorganization in marginal mountain areas. It does not require excessive investment but favours the reintegration of abandoned fields and an increase in pasturelands. The results of this study contribute to the debate about reclaiming mountain landscapes affected by human activities and subject to intense degradation processes. Copyright © 2015 John Wiley & Sons, Ltd.
Amine‐Functionalized Porous Polymer Network for Highly Selective Absorption of CO2 Over N2
Authors: Lee Doyun , Zhang Chengyi , Gao Haifeng
Published: December 2014

Porous polymeric sorbents showing selective CO2 absorption over N2 are prepared by conventional radical copolymerization of divinylbenzene and 4‐vinylbenzyl chloride under solvothermal conditions, followed by surface modification of the pores with polyamines. The amine‐functionalized porous materials that interact with CO2 via chemisorption exhibit exceptionally high CO2/N2 select­ivity of up to 373 times, determined by ideal adsorbed solution theory (IAST).

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A note on conjugate distributions for copulas
Authors: Fernández Mariela , González‐López Verónica A. , Rifo Laura R.
Published: December 2014

A family of conjugated distributions for a given type of copulas is defined in this paper. Those copulas can be written as a mixture of d‐dimensional parameter exponential functions. The generalized Farlie–Gumbel–Morgenstern copula is an example of this representation. This family is used to illustrate the estimation technique with real data. Also, the applicability of Bayesian predictive approach is shown in an education policy issue by defining goals for the number of students per class that leads to improve their performance at school. Copyright © 2014 John Wiley & Sons, Ltd.
Numerical analysis of the geotechnical behaviour of energy piles
Authors: Di Donna AIice , Laloui Lyesse
Published: December 2014

Energy geostructures are rapidly gaining acceptance around the world; they represent a renewable and clean source of energy that can be used for the heating and cooling of buildings and for de‐icing of infrastructures. This technology couples the structural role of geostructures with the energy supply, using the principle of shallow geothermal energy. The geothermal energy exploitation represents an additional thermal loading, seasonally cyclic, which is imposed on the soil and the structure itself. Because the primary role of the piles is the stability of the superstructure, this aspect needs to be ensured even in the presence of the additional thermal load. The goal of this paper is to numerically investigate the behaviour of energy pile foundations during heating–cooling cycles. For this purpose, the finite element method is used to simulate both a single and a group of energy piles. The piles are subjected to a constant mechanical load and a seasonally cyclic thermal load over several years, imposed in terms of injected–extracted thermal power. The soil and the pile–soil interface behaviours are reproduced using a thermoelastic‐thermoplastic constitutive model. The thermal‐induced stresses inside the piles and the additional displacements of the foundations are discussed. The group model is used to investigate the interactions between the piles during thermo‐mechanical loading. The presented results are specific to the studied cases but lead to the conclusion that both the thermal‐induced displacements and stresses, despite being acceptable under normal working conditions, deserve to be taken into account in the geotechnical design of energy piles. Copyright © 2014 John Wiley & Sons, Ltd.
Tire footprint analysis depending on the elastokinematics of a multi‐link suspension system using multi‐body dynamics simulation
Authors: Kohl Sergej , Sextro Walter , Zuber Armin
Published: December 2014

An automotive suspension system represents one of the most complex and important systems in a passenger vehicle, which has to ensure a robust and optimized contact between the wheels and the road at any time. For improving a suspension system it is important to take an investigative look at the interaction between suspension, tire and road dynamics. Thus a part of a study into aspects of suspension modeling on multi‐body simulations of rear multi‐link suspension system dynamics with focus on the tire footprint area is presented in this work. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Time Optimal Path Planning for Industrial Robots: A Dynamic Programming Approach Considering Torque Derivative and Jerk Constraints
Authors: Oberherber Matthias , Gattringer Hubert , Springer Klemens
Published: December 2014

This paper presents a dynamic programming approach for calculating time optimal trajectories for industrial robots, subject to various physical constraints. In addition to path velocity, motor torque, joint velocity and acceleration constraints, the present contribution also shows how to deal with torque derivative and joint jerk limitations. First a Cartesian path for the endeffector is defined by splines using Bernstein polynomials as basis functions and is parameterized via a scalar path parameter. In order to compute the belonging quantities in configuration space, inverse kinematics is solved numerically. Using this and in combination with the dynamical model, joint torques as well as their derivatives can be constrained. For that purpose the equations of motion are calculated with the help of the Projection Equation. As a consequence of the used optimization problem formulation, the dynamical model as well as the restrictions have to be transformed to path parameter space. Due to the additional consideration of jerk and torque derivative constraints, the phase plane is expanded to a phase space. The parameterized restrictions lead to feasible regions in this space, in which the optimal solution is sought. Result of the optimization is the time behavior of the path parameter and subsequently the feed forward torques for the optimal motion on the spatial path defined by previously mentioned splines. Simulation results as well as experimental results for a three axes industrial robot are presented. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energy‐optimized bipedal running of a simple humanoid robot
Authors: Römer Ulrich , Fidlin Alexander
Published: December 2014

A method to optimize energy efficiency for bipedal running robots is presented. A running model of a simple bipedal robot consisting of five rigid bodies connected by actuated revolute joints is introduced. The actuators' torques are generated by a trajectory tracking controller to produce periodic running gaits. The controller's reference trajectories are parameterized by Bézier polynomials. A numerical optimization is used to employ reference trajectories with optimal energy efficiency for average velocities in the range of 1.5 to 5.5 m/s. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Computational modeling of cardiac tissue with strongly coupled electromechanics and orthotropic viscoelastic effects
Authors: Cansiz Baris , Dal Hüsnü , Kaliske Michael
Published: December 2014

Modeling of complex mechanisms leading to the functioning of the heart has been an active field of research since decades. Difficulties associated with in vivo experiments motivate the utilization of computational models in order to gain a better appreciation of heart electromechanics. Although rate dependent behaviour of the orthotropic passive heart tissue has been comprehensively studied in the literature [1], effects of this phenomenon on fully coupled cardiac electromechanics are unrevealed yet. Therefore, this contribution is concerned with the investigation of viscous effects on the electromechanical response of the myocardium. To this end, we adopt the fully implicit finite element framework which strongly couples the mechanical and electrophysiological problem of the myocardium in a mono‐ and bi‐domain setting [2,3], respectively. Viscous effects, however, are consistently embedded into this framework by making use of the orthotropic viscoelastic material model for the passive myocardium, which considers different relaxation mechanisms for the different orientation directions [5]. The performance of the proposed model is assessed by comparing finite element simulations of spiral waves in heart tissue for elastic and viscoelastic formulations. We further investigate the influence of viscosity on the defibrillation phenomenon by means of the finite element formulation of bidomain electrophysiology. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On dynamic finite element analysis of viscoplastic thin‐walled structures with non‐local damage: A phase‐field approach
Authors: Nguyen A.D. , Trinh B.T. , Stoffel M. , Markert B.
Published: December 2014

[EN] In this work, a nonlocal damage model is proposed for dynamic analysis of viscoplastic shell structures using the phase‐field approach. A phase‐field variable on the mid surface is introduced to characterize the nonlocal damage as well as the transition between undamaged and damaged phase. The total free energy in [1] is modified as a sum of Helmholtz free‐energy and Ginzburg‐Landau one. The latter is defined as a function of the phase‐field variable and its corresponding gradient. This enhancement gives rise to an introduction of gradient parameters in terms of a substructure‐related intrinsic length‐scale. The evolution of the phase‐field based damage variable can be found from the minimum principle of the dissipation potential [3]. The performance of the proposed model is demonstrated through numerical results of a plate with a circular hole. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase field modeling of complex crack patterns in multi‐physics problems
Authors: Schänzel Lisa‐Marie , Ulmer Heike , Miehe Christian
Published: December 2014

Recently developed continuum phase field models for brittle fracture show excellent modeling capability in situations with complex crack topologies including branching in the small and large strain applications. This work presents a generalization towards fully coupled multi‐physics problems at large strains. A modular concept is outlined for the linking of the diffusive crack modeling with complex multi field material response, where the focus is put on the model problem of finite thermo‐elasticity. This concerns a generalization of crack driving forces from the energetic definitions towards stress‐based criteria, the constitutive modeling of degradation of non‐mechanical fluxes on generated crack faces. Particular assumptions are made on the generation of convective heat exchanges approximating surface load integrals of the sharp crack approach by distinct volume integrals. The coupling effect is also shown in generation of cracks due to thermally induced stress states. We finally demonstrate the performance of the phase field formulation of fracture at large strains by means of representative numerical examples. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Numerical aspects of failure modeling of amorphous thermoplastics
Authors: Schneider Konrad , Seelig Thomas
Published: December 2014

The present work investigates a reliable method of integrating the evolution equations of constitutive models for amorphous thermoplastics that typically utilize a power‐law or exponential‐type flow rule. When it comes to sudden changes in the external stress (e.g. element deletion technique in explicit finite element analysis) these functional dependencies need a special treatment to assure a numerically stable integration of the evolution equations. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Finite Element Simulation of Frost Wedging in Ice Shelves
Authors: Plate Carolin , Müller Ralf , Humbert Angelika , Gross Dietmar
Published: December 2014

Break‐up events in ice shelves have been studied extensively during the last years. One popular assumption links disintegration events to surface melting of the ice shelf in conjunction with growing melt‐water ponds, leading to hydro‐fracture. As this explanation only holds during warm seasons [1], the possibility of frost wedging as forcing mechanism for autumn and winter break‐up events is considered. Frost wedging can only occur if a closed ice lid seals the water inside the crack. Hence, the present study of frost wedging in a single crack uses ice lid thicknesses to evaluate the additional pressure on the crack faces. The investigation of the resulting stress intensity factor as a measure of crack criticality follows consequently. The results show that freezing water inside a crack can result in unstable crack growth of an initially stable water filled crack. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Phase Field Approximation of Dynamic Brittle Fracture
Authors: Schlüter Alexander , Kuhn Charlotte , Müller Ralf
Published: December 2014

The numerical assessment of fracture has gained importance in fields like the safety analysis of technical structures or the hydraulic fracturing process. The modelling technique discussed in this work is the phase field method which introduces an additional scalar field. The smooth phase field distinguishes broken from undamaged material and thus describes cracks in a continuum. The model consists of two coupled partial differential equations ‐ the equation of motion including the constitutive behaviour of the material and a phase field evolution equation. The crack growth follows implicitly from the solution of this system of PDEs. The numerical solution with finite elements can be accelerated with an algorithm that performs computationally extensive tasks on a graphic processing unit (GPU). A numerical example illustrates the capability of the model to reproduce realistic features of dynamic brittle fracture. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Hypersingularities in three‐dimensional crack configurations in composite laminates
Authors: Hell Sascha , Becker Wilfried
Published: December 2014

Three‐dimensional crack configurations in composite laminates are studied by means of the Scaled Boundary Finite Element Method (SBFEM) particularly regarding stress singularities and their associated deformation modes. The SBFEM is an efficient semi‐analytical method that permits solving linear elastic mechanical problems. Only the boundary needs to be discretized while the problem is considered analytically in the direction of the dimensionless radial coordinate pointing from the scaling center to the boundary . An important advantage is that it requires no additional effort for the characterization of existing stress singularities. The situation of two meeting inter‐fiber cracks is investigated in detail, considering different materials and fiber / crack orientations. It is shown that in three‐dimensional crack configurations in composite laminates so‐called hypersingularities can occur, i.e. stress singularities which are even stronger than the classical crack singularity. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and Numerical Investigations of Al/Mg Compounds
Authors: Kirbach Carola , Stockmann Martin , Ihlemann Jörn
Published: December 2014

Al/Mg compounds produced by hydrostatic extrusion exhibit unique characteristics regarding high strength and low weight, which are required by safety part applications in lightweight constructions. Between the two materials an interface in form of a brittle intermetallic phase consisting of Al2Mg3 and Al12Mg17 arises during the production process. However, a certain plastic deformability of the semi‐finished product is essential for further forming processes. Even under multi‐axle load during a radial upsetting process, the interface maintains a full material joint although a fragmentation and a new secondary interface between the fragments can be observed. Due to the evaluations of light microscopy images and Eulerian Hencky strain values at the interface, which are obtained with the help of the Digital Image Correlation, a relation between the strain and the boundary layer's appearance seems reasonable. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Reduction of non‐linear drill string models using proper orthogonal decomposition
Authors: Kueck Armin , Recke Bastian , Ostermeyer Georg‐Peter
Published: December 2014

Oil service companies use highly complex drill string models to optimize drilling assemblies and to perform post‐drilling analysis. These drill string models are usually non‐linear, FEM based and able to describe arbitrary curved well bore geometries. One of the most critical parts is the description of the contact at the well bore wall. Due to the model's complexity, simulations in time domain are extremely expensive and can take days to weeks. Less results in the same time reduce the quality of optimization and parameter studies. Thus, one goal of research is to accelerate time domain simulations while maintaining an appropriate level of accuracy. One way to reduce simulation time is to lower the order of the system. There are a lot of common well‐developed order‐reduction‐techniques for linear‐systems, e.g., modal reduction. However, these methods cannot handle unilateral‐constraints as used for the wall contact description. Hence, a reduction technique for non‐linear systems is needed. A promising reduction method of this kind is the proper orthogonal decomposition (POD, also called Karhunen‐Loève Transformation). This technique determines the principal structure of motions based on time signal measurements. The system is then reduced by transforming it to a lower dimensional space build on these main structures. In this paper the POD will be applied to a basic drill string model. It is a 2D‐FEM beam‐element drill string system with linear penalty‐springs. Parameter studies of the contact stiffness and the degree of reduction will show the performance and possible gain of this reduction method. Finally advantages and inconveniences of this method for drill string dynamics will be discussed. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Static and dynamic behavior of a selected cable‐stayed footbridge with respect to change of the cable tension
Authors: Pakos Wojciech , Wójcicki Zbigniew
Published: December 2014

The paper presents the theoretical analysis of the possibilities of using the authors' own method of actively reducing resonant vibration in cable‐stayed footbridges. The method of actively reducing vibration was earlier tested on a laboratory model of a steel footbridge, [1]. The method relies on changing the static tension in chosen cables. The term “active” refers to the fact that the tension changes would only be introduced when resonant vibration of the structure occurred. A change in the cable tensions should cause a change of the natural frequencies for which resonant vibration amplification appeared earlier. Eigenproblem sensitivity analysis, formulated for the structure according to the second order theory, is the basis for choosing the cables in which the tension should change. Apart from analyzing the effectiveness of the active method for reducing resonant vibration, the influence of cable tension change on other values was also studied. These values included the changes in vibration amplitudes, as well as changes of cross‐section forces, tensions, and static bend of the structure elements that are most sensitive to tension change. It was also established whether the tension changes in chosen cables, which were large enough to cause a practically significant reduction of resonant vibration, cause exceeding the levels of Serviceability Limit State (SLS) and Ultimate Limit State (ULS) for the structure as a whole or for some of its elements. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Second‐order time‐integration in inelastic dynamical systems
Authors: Grafenhorst Matthias , Hartmann Stefan , Rang Joachim
Published: December 2014

In structural dynamics the initial boundary value problem has to be solved in the space and time domain. The spatial discretization is done using finite elements. For the temporal discretization two classes of Runge‐Kutta methods and the generalized‐α method are compared. The representatives for the Runge‐Kutta methods are diagonally implicit Runge‐Kutta schemes (DIRK) and diagonally implicit Runge‐Kutta‐Nyström schemes (DIRKN). (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Contact of ropes and orthotropic rough surfaces
Authors: Konyukhov Alexander
Published: December 2014

Contact between arbitrary curved ropes and arbitrary curved rough orthotropic surfaces has been revised from the geometrical point of view. Variational equations for the equilibrium of ropes on orthotropic rough surfaces are derived, first, using the consistent variational inclusion of frictional contact constraints via Karush‐Kuhn‐Tucker conditions expressed in Darboux basis. Then, the systems of differential equations are derived for both statics and dynamics of ropes on a rough surface depending on the sticking‐sliding condition for orthotropic Coulomb's friction. Three criteria are found to be fulfilled during the static equilibrium of a rope on a rough surface: “no separation”, condition for dragging coefficient of friction and inequality for tangential forces at the end of the rope. The limit tangential loads still preserve the famous “Euler view” T = T0eωs for the curves and surfaces of constant curvature. It is shown that the curve of the maximum tension of a rough orthotropic surface is geodesic. Equations of motion are derived in the case if the sliding criteria is fulfilled and there is “no separation”. Various cases possessing analytical solutions of the derived system, including Euler case and a spiral rope on a cylinder are shown as examples of application of the derived theory. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Two Dimensional Model for the Dynamical Contact of Elastic Rough Surfaces
Authors: Neuhaus Jan , Sextro Walter
Published: December 2014

To model the contact behavior including dynamical effects, a two dimensional mechanical model of elastic rough contact is developed. This model can simulate the contact behaviour between two rough surfaces depending on normal pressure, sliding speed and roughness profiles. The contact between two rough surfaces is reduced to a rough rigid and a rough elastic layer. The elastic layer is modeled by point masses connected by spring‐damper elements. The total system is described by coupled ODEs. The number of ODEs and thus the degree of freedom of the model depends on the varying contact conditions. The contact conditions are monitored during the simulation and the simulation interrupts, in case the contact conditions change. The equations of motion are then adapted with respect to the contact constraints. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experiments, modelling and simulation of adhesive curing processes in bonded three dimensional curved piezo metal composite structures
Authors: Rudolph Martin , Landgraf Ralf , Scherzer Robert , Ihlemann Jörn
Published: December 2014

This contribution deals with the modelling and simulation of curing phenomena in adhesively bonded piezo metal composites which consists of a piezoelectric module enclosed by an adhesive layer which in turn is surrounded by two metal sheets. A short survey on the neccessary experimental investigations to characterise the adhesive's material behaviour is given and important aspects on the corresponding phenomenological modelling approach are presented. Both steps take into account the curing reaction, changes of volume, like chemical shrinkage, and inelastic mechanical behaviour which is temperature and curing dependent. Finally, the simulation strategy for the modelling within a finite element environment is depicted. By this, residual stresses, secondary deformations and loads on the piezo modules can be predicted, which is exemplified by a comparative study verifying a novel manufacturing strategy. (© 2014 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)