bluuebunny/crossref_metadata_2025 huggingface dataset:
A comparative study of DNA binding and cell cycle phase perturbation by the dinuclear complex of Cd(II) with the condensation product of 2‐acetylpyridine and malonic acid dihydrazide N′,N′2‐bis[(1E)‐1‐(2‐pyridyl)ethylidene]propanedihydrazide
Authors: Vujčić Miroslava , Lazić Milan , Milenković Milica , Sladić Dušan , Radulović Siniša , Filipović Nenad , Anđelković Katarina
Published: November 2010

Organometallic Cd(II) compounds have recently attracted attention for their anticancer activity. The interaction of the dinuclear complex of Cd(II) with the condensation product of 2‐acetylpyridine and malonic acid dihydrazide, N′,N′2‐bis[(1E)‐1‐(2‐pyridyl)ethylidene]propanedihydrazide (Cd(II)H2L), with calf thymus DNA (CT‐DNA) was monitored by blue shift in UV–vis spectra of the complex. The binding constant of Cd(II)H2L complex with CT‐DNA was determined (KB = 1.8 × 104 M−1) and was indicative of minor groove binding. Agarose gel electrophoretic changes in mobility of supercoiled and circular forms of pBR322 and pUC18 plasmids in the presence of the complex suggest that conformational changes in the plasmids occur upon binding of the Cd(II)H2L complex. The Cd(II)H2L complex induced perturbation of the cell cycle phase distribution and an increase in the percentage of cells in the sub‐G1 phase of human cervical cancer HeLa cell line and murine melanoma B16 cell line. Immunoblotting analysis showed the overexpression of Bcl‐2 protein with the Cd(II)H2L complex. © 2010 Wiley Periodicals, Inc. J Biochem Mol Toxicol 25:175–182 2011; View this article online at wileyonlinelibrary.com. DOI 10.1002/jbt.20374
Ultrastructural comparison of the ocelli ofSinopanorpa tinctaandBittacus planus(Mecoptera)
Authors: Wei Yao , Hua Baozhen
Published: November 2010

On the contrary to compound eyes, dorsal ocelli are poorly investigated for their ultrastructure in many insect groups, including Mecoptera. The ocellar ultrastructure of the scorpionflySinopanorpa tincta(Navás) in Panorpidae and the hangingflyBittacus planus(Cheng) in Bittacidae was examined using transmission electron microscope. Both species possess three ocelli on the vertex of their heads and each ocellus has a corneal lens, some pigment cells at the outer rim of the lens, and fused rhabdoms. Beneath the corneal lens lies a single layer of corneagenous cells, which is very thick with the nuclei located proximally inS. tinctaand quite thin inB. planus. A portion of rhabdom is composed of rhabdomeres from two adjacent retinula cells inS. tincta, but from four retinula cells inB. planus. Each rhabdomere comprises parallel microvilli projecting laterally from the apposed retinula cells. In addition, abundant electron‐lucent granules are present at the middle part around each retinula inB. planus. Only pigment granules exist around the retinula proximally at the nucleate level inS. tincta. Microsc. Res. Tech., 2010. © 2010 Wiley‐Liss, Inc.
Observation particle morphology of colloidal system by conventional SEM with an improved specimen preparation technique
Authors: Xu Jing , Hou Zhaosheng , Yuan Xiaojiao , Guo Hong
Published: November 2010

On the basis of our previous report that polymer emulsion with different viscosity can be investigated by conventional scanning electron microscopy (SEM), we have developed an improved specimen preparation technique for obtaining particle morphology and size of colloidal silver, collagen, glutin, and polymer microspheres. In this study, we expect to provide a means for charactering the three‐dimensional surface microstructure of colloidal particles. Dilution of the samples with appropriate volatile solvent like ethanol is effective for SEM specimen preparation. At a proper ratio between sample and ethanol, the colloidal particles are dispersed uniformly in ethanol and then deposited evenly on the substrate. Different drying methods are studied to search a proper drying condition, in which the small molecule solvent is removed without destroying the natural particle morphology. And the effects of ethanol in the specimen preparation process are described by analyzing the physicochemical properties of ethanol. The specimen preparation technique is simple and can be achieved in common laboratory for charactering the particle morphology of colloidal system. Microsc. Res. Tech., 2011. © 2010 Wiley‐Liss, Inc.
A unique skeletal microstructure of the deep‐sea micrabaciid scleractinian corals
Authors: Janiszewska Katarzyna , Stolarski Jarosław , Benzerara Karim , Meibom Anders , Mazur Maciej , Kitahara Marcelo V. , Cairns Stephen D.
Published: November 2010

Micrabaciids are solitary, exclusively azooxanthellate deep‐sea corals belonging to one of the deepest‐living (up to 5,000 m) scleractinian representatives. All modern micrabaciid taxa (genera: Letepsammia, Rhombopsammia, Stephanophyllia, Leptopenus) have a porous and often very fragile skeleton consisting of two main microstructural components known also from other scleractinians: rapid accretion deposits and thickening deposits. However, at the microstructural level, the skeletal organization of the micrabaciids is distinctly different from that of other scleractinians. Rapid accretion deposits consist of alternations of superimposed “microcrystalline” (micrometer‐sized aggregates of nodular nanodomains) and fibrous zones. In contrast to all shallow‐water and sympatric deep‐water corals so far described, the thickening deposits of micrabaciids are composed of irregular meshwork of short (1–2 μm) and extremely thin (ca. 100–300 nm) fibers organized into small, chip‐like bundles (ca. 1–2 μm thick). Longer axes of fiber bundles are usually subparallel to the skeletal surfaces and oriented variably in this plane. The unique microstructural organization of the micrabaciid skeleton is consistent with their monophyletic status based on macromorphological and molecular data, and points to a diversity of organic matrix‐mediated biomineralization strategies in Scleractinia. J. Morphol.,2011. © 2010 Wiley‐Liss, Inc.
Area, length and mineralization content of new bone at bone–tendon junction predict its repair quality
Authors: Lu Hongbin , Hu Jiangzhong , Qin Ling , Chan Kai Ming , Li Gang , Li Kanghua
Published: November 2010

We investigated the hypothesis that if the area, length, and mineralization of newly formed bone could be used to predict the healing quality of patella–patellar tendon (PPT) junction after partial patellectomy. Twenty‐four rabbits underwent partial patellectomy and their PPT complexes of the operated limbs were harvested at weeks 6, 12, and 18 postoperatively. The area, length, and mineralization of newly formed bone at PPT junction healing interface was evaluated radiographically and peripheral quantitative computational tomographically. The healing quality of PPT complexes in terms of its tensile property was determined by biomechanical testing. The results showed that the area, length, and mineral content of newly formed bone, and its tensile strength increased significantly with follow‐up time. The area of newly formed bone was strongly correlated with the failure load, ultimate strength and energy at failure (r = 0.75, 0.76, and 0.70, respectively, p < 0.01 for all). The length of newly formed bone was also found to be correlated with failure load, ultimate strength and energy at failure (r = 0.61, 0.54, 0.67, respectively, p < 0.01 for all). In addition, the bone mineral content of newly formed bone but not its bone mineral density was moderately correlated with failure load, ultimate strength and energy at failure (r = 0.44, 0.51, 0.42, respectively, p < 0.05 for all). In conclusion, the area, length, and mineralization of newly formed bone at the PPT junction after partial patellectomy may serve as useful noninvasive indices in assessing the quality of the bone–tendon junction repair. © 2010 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 29:672–677, 2011
Room temperature ionic liquid‐mediated molecularly imprinted polymer monolith for the selective recognition of quinolones in pork samples
Authors: Sun Xiangli , He Jia , Cai Guorui , Lin Anqing , Zheng Wenjie , Liu Xuan , Chen Langxing , He Xiwen , Zhang Yukui
Published: November 2010

A novel molecularly imprinted polymer monolith was prepared by the room temperature ionic liquid‐mediated in situ molecular imprinting technique, using norfloxacin (NOR) as the template, methacrylic acid as the functional monomer, ethylene glycol dimethacrylate as the cross‐linker. The optimal synthesis conditions and recognition properties of NOR‐imprinted monolithic column were investigated. The results indicated that the imprinted monoliths exhibited good ability of selective recognition against the template and its structural analog. Using the fabricated material as solid‐phase extraction sorbent, a sample pre‐treatment procedure of molecularly imprinted solid‐phase extraction coupling with HPLC was developed for determination of trace quinolone residues in animal tissues samples. The recoveries ranging from 78.16 to 93.50% for eight quinolones antibiotics such as marbofloxacin, NOR, ciprofloxacin, danofloxacin, difloxacin, oxolinic acid, flumequine and enrofloxacin were obtained.
Determination of amoxapine and nortriptyline in blood plasma and serum by salt‐assisted liquid–liquid microextraction and high‐performance liquid chromatography
Authors: Gupta Manju , Jain Archana , Verma Krishna K.
Published: November 2010

A new, selective and sensitive method has been developed for the determination of tricyclic antidepressant drugs, amoxapine and nortriptyline, in human blood plasma and serum, involving their reaction with allyl isothiocyanate and extraction of thiourea derivatives with water‐miscible organic solvent acetonitrile. The phase separation was effected by addition of ammonium sulphate, a process called salt‐assisted liquid–liquid microextraction. The extract was analyzed by HPLC with UV detection at 254 nm. The method has been optimized for derivatization reaction time and temperature, solvent for extraction, and salt for solvent phase separation. Under the optimal conditions, a linear calibration graph was obtained between the amount of drug and the peak area of thiourea derivatives in the range of 0.002–20 mg/L drugs. The correlation coefficient and limit of detection values for amoxapine and nortriptyline in serum/plasma samples were in the range of 0.9953–0.9999 and 0.46–0.58 μg/L, respectively. The recovery in spiking experiments ranged, respectively, 75–88% (RSD 3.4–7.2%) and 79–97% (RSD 3.7–7.9%) for the two drugs.
A weak cation‐exchange monolith as stationary phase for the separation of peptide diastereomers by CEC
Authors: Ludewig Ronny , Nietzsche Sandor , Scriba Gerhard K. E.
Published: November 2010

A CEC weak cation‐exchange monolith has been prepared by in situ polymerization of acrylamide, methylenebisacrylamide and 4‐acrylamidobutyric acid in a decanol–dimethylsulfoxide mixture as porogen. The columns were evaluated by SEM and characterized with regard to the separation of diastereomers and α/β‐isomers of aspartyl peptides. Column preparation was reproducible as evidenced by comparison of the analyte retention times of several columns prepared simultaneously. Analyte separation was achieved using mobile phases consisting of acidic phosphate buffer and ACN. Under these conditions the peptides migrated due to their electrophoretic mobility but the EOF also contributed as driving force as a function of the pH of the mobile phase due to increasing dissociation of the carboxyl groups of the polymer. Raising the pH of the mobile phase also resulted in deprotonation of the peptides reducing analyte mobility. Due to these mechanisms each pair of diastereomeric peptides displayed the highest resolution at a different pH of the buffer component of the mobile phase. Comparing the weak‐cation exchange monolith to an RP monolith and a strong cation‐exchange monolith different elution order of some peptide diastereomers was observed, clearly illustrating that interactions with the stationary phase contribute to the CEC separations.
Gene expression in the oropharynx of children exposed to secondhand smoke
Authors: Ostrower Samuel T. , Fischer Tova C. , Smith Richard V. , Belbin Thomas J. , Bent John P. , Parikh Sanjay R.
Published: November 2010

Objectives/Hypothesis:

To compare gene expression in oropharyngeal mucosa of children with (ex+) and without (ex−) secondhand smoke exposure.

Study Design:

Prospective case‐control.

Methods:

Forty‐one age‐ and gender‐matched children (2–6 years old) undergoing tonsillectomy for sleep disordered breathing at a tertiary care children's hospital were assessed for secondhand smoke exposure. Parental response to a validated questionnaire relating to secondhand smoke exposure governed inclusion. Sixteen samples were selected for microarray analysis (7 ex+, 9 ex−). Following tonsillectomy, ex vivo brushing of the mucosa isolated total RNA. Genome‐wide expression profiles were generated by comparing sample RNA to a reference of all samples, assessing 27,323 cDNA clones. Microarray clones were ranked according to their ability to distinguish between the two groups using a Student t test.

Results:

A total of 318 cDNA clones distinguished the two groups (P < .01); 180 genes were overexpressed and 138 underexpressed in ex+ samples relative to the ex− group. Independent analysis of these two groups sorted genes into disease processes and molecular functional groups, including cancer (34 genes in the overexpressed group, 29 underexpressed, P < .05), cell cycle (14 and 10), and cell growth and proliferation (7 and 11). Two of the upregulated genes, LCN2 and IQGAP1, have been previously linked to inflammation in smokers and response/repair to cellular injury in bronchial epithelium.

Conclusions:

Findings in this pilot study support the hypothesis that secondhand smoke exposure seems to induce gene expression changes in the oropharyngeal mucosa of exposed children, which may have significant implications for current and future disease processes. Laryngoscope, 2010
Cochlear implantation in patients with autoimmune inner ear disease including cogan syndrome: A comparison with age‐ and sex‐matched controls
Authors: Wang Jenny R. , Yuen Heng W. , Shipp David B. , Stewart Suzanne , Lin Vincent Y. W. , Chen Joseph M. , Nedzelski Julian M.
Published: November 2010

Objectives/Hypothesis:

Evaluate the characteristics and outcomes of patients with autoimmune inner ear disease (AIED) who have undergone cochlear implantation (CI) and compare post‐CI performance in AIED to matched controls.

Study Design:

Retrospective case control study.

Methods:

Study cohort was comprised of 25 adult implantees (AIED [n = 18], Cogan syndrome [n = 7]). The AIED group was defined by rapidly progressive bilateral sensorineural hearing loss leading to unusable hearing within weeks to months. Patients with Cogan syndrome, the archetypal inner ear autoimmune disease, were also examined and used for within‐cohort comparison. Clinical and operative records were reviewed. Post‐CI performance was assessed using open‐set sentence tests. Age‐ and sex‐matched individuals deafened by other postlingual causes were used as controls.

Results:

Of 25 patients, 24 had uneventful, full electrode insertions. One AIED patient had partial insertion due to cochlear ossification and did not achieve open‐set speech perception post‐CI. Mean open‐set sentence scores for study patients with uneventful insertions were 92.8%, 97.3%, and 96.4% at 6 months, 1 year, and ≥2 years, respectively. Compared to matched controls, patients deafened by autoimmune causes had significantly higher post‐CI performance at all postoperative test intervals (P < .05). There was no significant difference in postimplantation performance between Cogan syndrome and AIED patients.

Conclusions:

To our knowledge this was the largest study of cochlear implantation in AIED and Cogan syndrome patients. In our experience, both groups generally attained high levels of post‐CI speech perception and performed above average. Cochlear ossification affecting implantation in Cogan syndrome patients was not observed in our series, contrary to some reports. Laryngoscope, 2010
Risk factors for postoperative hemorrhage following tonsillectomy
Authors: Tomkinson Alun , Harrison Wendy , Owens David , Harris Susan , McClure Victoria , Temple Mark
Published: November 2010

Objectives/Hypothesis:

To identify the main risk factors associated with postoperative hemorrhage following tonsillectomy.

Study Design:

Prospective multicenter observational study.

Methods:

The Surgical Instrument Surveillance Programme (SISP) was established in 2003 to monitor tonsil and adenoid surgery and the associated complications in all hospitals in Wales. Data were examined between April 1, 2003, and June 30, 2008, by using binary logistic regression, for risk factors that may contribute to primary (R1) or secondary (R2) postoperative hemorrhage of a severity sufficient to require a return to the operating theater.

Results:

A total of 17,480 procedures were included. Patients aged ≥12 years were 1.5 (1.0–2.1; P < .05) and 3 times (2.2–4.9; P < .0001) more likely to experience R1 and R2 complications, respectively. There were 2.5 times as many females as males aged ≥12 years who underwent tonsillectomy, but males were almost twice as likely to experience R1 (1.4–2.8), P < .0001, or R2 (1.2–2.5), P < .001, postoperative hemorrhage. There was a 1.9‐fold increased likelihood of R1 (1.1–3.3), P < .05, with the most junior surgeon, and no relationship with R2. All techniques that used heat had a significantly greater adjusted odds of R2 as compared with cold dissection, with odds ranging from 2.7 (1.5–4.7), P < .001, for dissection plus bipolar diathermy and ties, to 13.0 (5.8–29.1), P < .0001, with coblation when used with other techniques. No additional risk was associated with specified single‐use instruments.

Conclusions:

Patient age and sex and operative technique were the most significant factors affecting the risk and timing of serious postoperative hemorrhage, with no additional risk associated with the use of specified single‐use instruments. Laryngoscope, 2010
Improving apparent diffusion coefficient estimates and elucidating tumor heterogeneity using Bayesian adaptive smoothing
Authors: Walker‐Samuel Simon , Orton Matthew , Boult Jessica K. R. , Robinson Simon P.
Published: November 2010

The spatial distribution of apparent diffusion coefficient (ADC) estimates in tumors is typically heterogeneous, although this observed variability is composed of both true regional differences and random measurement uncertainty. In this study, an adaptive Bayesian adaptive smoothing (BAS) model for estimating ADC values is developed and applied to data acquired in two murine tumor models in vivo. BAS models have previously been shown to reduce parameter uncertainty through the use of a Markov random field. Here, diffusion data acquired with four averages was used as an empirical gold standard for evaluating the BAS model. ADC estimates using BAS displayed a significantly closer accordance with the gold standard data and, following analysis of uncertainty estimates, appeared to even outperform the gold standard. These observations were also reflected in simulations. These results have strong implications for clinical studies, as it suggests that the BAS postprocessing technique can be used to improve ADC estimates without the need to compromise on spatial resolution or signal‐to‐noise or for the adaptation of acquisition hardware. A novel measure of tumor ADC heterogeneity was also defined, which identified differences between tumors derived from different cell lines, which were reflected in histological variations within the tissue microenvironment. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.
Regional and global pancreatic T*2 MRI for iron overload assessment in a large cohort of healthy subjects: Normal values and correlation with age and gender
Authors: Restaino Gennaro , Meloni Antonella , Positano Vincenzo , Missere Massimiliano , Rossi Giuseppe , Calandriello Lucio , Keilberg Petra , Mattioni Oreste , Maggio Aurelio , Lombardi Massimo , Sallustio Giuseppina , Pepe Alessia
Published: November 2010

Multiecho gradient‐echo T*2 magnetic resonance imaging is a well‐established technique for iron overload assessment but there are few reports concerning the pancreas. The aim of this work was to assess the feasibility and reproducibility of the magnetic resonance imaging for measuring pancreatic regional and global T*2 values, to establish the lower limit of normal in a large cohort of healthy subjects and to correlate the measured values with age and gender. One hundred and twenty healthy subjects (61 males, 51 ± 17 years) underwent magnetic resonance imaging (1.5T) using a multiecho gradient‐echo T*2 sequence. T*2 measurements were performed in pancreatic head, body, and tail. The global value was calculated as the mean. Measurement of pancreatic T*2 values was feasible in all subjects. For the T*2 global value the coefficient of variation for intraoperator and interoperator reproducibility were 7.7% and 13%, respectively. The global T*2 values ranged from 24 to 52 ms with the lower limit of normal of 26 ms. There were no significant differences among the regional pancreatic T*2 values. No significant correlation was found between T*2 and patient age or gender. In conclusion, pancreatic T*2 measurements appear to be feasible, reproducible, nontime‐consuming and reliable. Gender‐ and age‐related differences concerning pancreatic T*2 were not found. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.
Accelerated multidimensional radiofrequency pulse design for parallel transmission using concurrent computation on multiple graphics processing units
Authors: Deng Weiran , Yang Cungeng , Stenger V. Andrew
Published: November 2010

Multidimensional radiofrequency (RF) pulses are of current interest because of their promise for improving high‐field imaging and for optimizing parallel transmission methods. One major drawback is that the computation time of numerically designed multidimensional RF pulses increases rapidly with their resolution and number of transmitters. This is critical because the construction of multidimensional RF pulses often needs to be in real time. The use of graphics processing units for computations is a recent approach for accelerating image reconstruction applications. We propose the use of graphics processing units for the design of multidimensional RF pulses including the utilization of parallel transmitters. Using a desktop computer with four NVIDIA Tesla C1060 computing processors, we found acceleration factors on the order of 20 for standard eight‐transmitter two‐dimensional spiral RF pulses with a 64 × 64 excitation resolution and a 10‐μsec dwell time. We also show that even greater acceleration factors can be achieved for more complex RF pulses. Magn Reson Med, 2011. © 2010 Wiley‐Liss, Inc.
Quantitative diffusion imaging of adipose tissue in the human lower leg at 1.5 T
Authors: Steidle G. , Eibofner F. , Schick F.
Published: November 2010

Diffusion‐weighted spin‐echo echo‐planar imaging was developed and applied for assessment of diffusion coefficients of adipose tissue in human lower leg on a 1.5‐T whole‐body MR scanner. Because of the higher molecular weight of triglycerides, apparent diffusion coefficients (ADCs) of adipose tissue are approximately two orders of magnitude smaller compared with water, leading to the necessity of using high b‐values up to 50,000 sec/mm2 and an echo time of 240 msec for sufficient diffusion‐related signal attenuation. ADC maps of adipose tissue in the human lower leg were derived for diffusion encoding along orthogonal spatial directions in six healthy volunteers. Mean diffusion coefficients in the tibial bone marrow amounted to (1.81 ± 0.10) × 10−5 mm2/sec (left–right), (1.96 ± 0.10) × 10−5 mm2/sec (anterior–posterior), and (1.96 ± 0.20) × 10−5 mm2/sec (head–feet), respectively. Pixel‐wise calculated ADC values of subcutaneous adipose tissue showed a distinctly higher variation with the smallest ADC values similar to those measured for tibial bone marrow. Some subcutaneous adipose tissue regions showed increased signal attenuation at higher b‐values resulting in ADC coefficients up to 4.2 × 10−5 mm2/sec. It must be noted that diffusion measurements with extremely high b‐values in vivo are extremely sensitive to incoherent motion effects in tissue. Nonetheless, it could be shown that in vivo diffusion imaging of adipose tissue in human lower leg is possible at 1.5 T in acceptable measurement time of a few minutes. Potential future applications of fat diffusion imaging are seen in temperature measurements in adipose tissue, detection of free fatty acids in white or brown adipose tissue in case of high lipolysis, differentiation of macro‐ and microvesicular steatosis, or assessment of the mobility of intramyocellular lipids. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Prostate cancer metabolite quantification relative to water in 1H‐MRSI in vivo at 3 Tesla
Authors: McLean Mary A. , Barrett Tristan , Gnanapragasam Vincent J. , Priest Andrew N. , Joubert Ilse , Lomas David J. , Neal David E. , Griffiths John R. , Sala Evis
Published: November 2010

1H magnetic resonance spectroscopic imaging was performed on 16 men with suspected prostate cancer using an 8‐channel external receive coil at 3 T. Choline and citrate (Cit) signals were measured in prostate lesions and normal‐appearing peripheral zone as identified on T2‐weighted images. Metabolites were quantified relative to unsuppressed water from a separately acquired magnetic resonance spectroscopic imaging dataset using LCModel. Validation experiments were also performed in a phantom containing physiological concentrations of choline, Cit, and creatine. In vitro, fair agreement between measured and true concentrations was observed, with the greatest discrepancy being a 35% underestimation of Cit. In vivo, one dataset was rejected for failure to meet the quality criterion of linewidth <15 Hz, and in 6 of 15 subjects, insufficient normal‐appearing peripheral zone tissue was identified for study. Lesions were found to have higher choline and choline/Cit, and lower Cit, than normal‐appearing peripheral zone. The smaller skew of data obtained using water normalization in comparison with metabolite ratios suggests potential usefulness in longitudinal tumor monitoring and in studies of treatment effects. Magn Reson Med, 2010. © 2010 Wiley‐Liss, Inc.
Can we accurately measure the onset latency to the first dorsal interosseous?
Authors: Takahashi Nobushige , Robinson Lawrence R.
Published: November 2010

We present two cases with and without a latency difference of the compound muscle action potential (CMAP) from the abductor digiti minimi (ADM) and the first dorsal interosseous (FDI). In each case, onset latencies of FDI CMAPs using the contralateral small finger as E2 were shorter than those of belly–tendon CMAPs from the ADM and FDI. We conclude that onset of the belly–tendon FDI CMAP does not necessarily indicate initial activation of the FDI. Muscle Nerve, 2011
Geometrically nonlinear models in crystal plasticity and the limit of rigid elasticity
Authors: Conti Sergio , Dolzmann Georg , Kreisbeck Carolin
Published: November 2010

It is shown that a standard model in crystal plasticity for which only rigid body motions have finite elastic energy can be approximated in the sense of Γ‐convergence by models with more general elastic potentials. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Damage Localization of Carbon‐Fibre‐Reinforced Plastic Plates
Authors: Ungethuem Andy , Lammering Rolf
Published: November 2010

Due to increasing application of light weight structures such as carbon‐fibre‐reinforced plastics well‐known procedures for the examination of components are not always applicable because of inadequate efforts or costs. Therefore, the development of a complementary system is suggested which allows for detecting damages of the structure. A new wave migration model enables to determine the damage location for non‐isotropic plates. The method is based on the propagation of waves reflected at the damage. Piezo‐electric sensors capture the strain caused by the propagating wave. The evaluation and processing of the signals of at least four sensors allow for the calculation of the damage location from the runtime of the signals. In the case of non‐isotropic material the shape of the wave front has to be known for the structure under investigation. These shapes can be obtained for example experimentally due to measurement and monitoring of the wave propagation by a laservibrometer or analytically by calculating this shapes using classical laminate and plate theory. Experiments show that the model indicates the damage location reliably. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Buckling of Carbon Nanotubes: a Molecular Static Approach
Authors: Schwarzbart Michael , Steindl Alois , Troger Hans
Published: November 2010

Axially loaded cylindrical continuous shells collapse either globally like a rod (Euler buckling), or locally (local shell wall buckling), depending on the ratio of the length of the shell over the diameter [1]. There are many published investigations, which show that this behaviour is also true for Carbon Nanotubes CNTs [2]. In this work a systematic analysis of the problem is given in the framework of molecular statics. This approach has the advantage of taking care of the discrete structure of CNTs. The covalent bonds of the hexagonal carbon network are modelled as nonlinear springs, and the compressive load is applied quasistatically, excluding follower forces. The software package LAMMPS [3] offers the AIREBO potential [4] and is suitable for describing CNTs. To identify the stability boundary in the parameter plane, LAMMPS is extended to compute the definiteness of the Hessian. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
On Discretization Effects within Particle Representations of Massive Forming Processes
Authors: Fischer Katrin , Ostermeyer Georg‐Peter
Published: November 2010

Particle methods can be used for the simulation of large deformations under large deformation rates which are e.g. characteristic for massive forming processes. Particles' dynamics have to be carefully chosen in order to describe heat and heat flows in a correct thermodynamic way. In the following, mesoscopic particle systems are used, which solve this problem by using internal variables and in addition so‐called hidden mechanical degrees of freedom ( [1], [2]).

Another problem of particle methods is the influence of a symmetric discretization of the continuum on the shear planes and yielding. An appropriate interpretation of the simulation results requires a differentiation into physical phenomena and those resulting from the discretization. These circumstances and possible correctives are shown using some examples. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Controller Design for a Test Bench for Seat Belt Systems
Authors: Huber Steffen , Eberhard Peter , Seifried Robert
Published: November 2010

In the product development of vehicle seat belt systems there is a strong need for the possibility of an isolated component testing that is comparable to real world car crashes. A test bench concept that is able to fulfill this requirement is presented. This test bench mainly consists of a highly dynamic actuator system for which a control scheme is presented. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Decentralized Control of an Industrial Robot with Elastic Gears
Authors: Riepl Roland , Gattringer Hubert , Bremer Hartmut
Published: November 2010

Today's robots, especially for industrial applications, regularly appear on the market in new shapes, various sizes and challenging configurations. In a certain number of interesting cases, the need for a satisfying joint control will arise, even if the system dynamics is not completely known. Furthermore, despite the fact that most robots' dynamics may be modeled very precisely, the use of complex model based control methods is often not applicable because of considerably high time delays to the distributed drives. Consequently, this contribution describes an independent joint control approach based on the method of nonlinearity estimation and compensation. In contrary to centralized control structures, industrial servo drives, powering synchronous motors, control independently their elastic joints with high sampling frequencies. Focusing not only on simulations, but also on laboratory experiments, detailed results for an industrial robot with six degrees of freedom with elastic gears are presented. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling and Parameter Identification of a Formula Student Car
Authors: Schiehlen Werner , Tobias Christoph , Wewel Marc
Published: November 2010

A modelling approach is described using the modules vehicle body, front axle and rear axle. All these modules are virtually assembled by CAD software and Simpack, a commercial multibody dynamics tool. The geometrical data are found from the CAD model while the mechanical data for the entire vehicle are evaluated by parameter identification based on mechanical principles. In detail, the static measurement and error analysis of the center of mass is explained as well as the dynamic tests to identify the moments of inertia of the car. Further, spring and damper characteristics are identified. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Handling kinematic loops of mobile machinery in real‐time applications
Authors: Schubert Christian , Beitelschmidt Michael , Kunze Günter
Published: November 2010

This paper compares different mathematical approaches for handling kinematic loops in real‐time applications by looking at the linkage arrangement of a wheel loader. All constraints must be satisfied on position level and no special integration algorithm is assumed. Classical DAE formulations and an ODE formulation based on coordinate partitioning are considered and compared together with four different explicit and linear‐implicit solvers suitable for real‐time applications. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Explicit and Implicit Solver Coupling: Stability Analysis Based on an Eight‐Parameter Test Model
Authors: Busch Martin , Schweizer Bernhard
Published: November 2010

Coupling different solvers via co‐simulation is frequently applied in the field of multi‐physical simulation. The numerical stability and accuracy of the coupled problem strongly depends on the coupling technique used for the co‐simulation. In the current work, different co‐simulation approaches are analytically investigated based on a linear eight‐parameter test model. The test model is formulated in state‐space form containing input and output variables so that the results may directly be applied to practical coupling interfaces. For the test model, recurrence formulas are derived for explicit and implicit coupling techniques of Jacobian and Gauss‐Seidel type. The numerical stability of the co‐simulation approach is examined by an eigenvalue analysis of the corresponding recurrence equation. Three‐dimensional stability plots can be analyzed for different coupling methods and for arbitrary order of the extrapolation/interpolation polynomial. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Integrability and nonintegrability in terms of transcendental functions in dynamics of a rigid body
Authors: Shamolin Maxim V.
Published: November 2010

The results of the presented work are due to the study of the applied problem of the rigid body motion in a resisting medium. More earlier the complete lists of transcendental first integrals expressed through a finite combination of elementary functions were obtained. This circumstance allowed the author to perform a complete analysis of all phase trajectories and highlight those properties of them which exhibit the roughness and preserve for systems of a more general form. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optimal control of an overhead crane within an energy‐momentum conserving method
Authors: Siebert Ralf , Betsch Peter
Published: November 2010

The present work deals with inverse multibody dynamics problems, more precisely with optimal control problems governed by differential‐algebraic equations. In our case, the control effort, which is necessary for moving a body from one position to another, will be minimized.

Beside the commonly used generalized coordinates formulation of the equations of motion, the application of redundant coordinates will permit the derivation of conserving integrators. In addition to existing structure preserving integrators [2], the equations of motion, which serve as constraints within the optimal control scheme, may also be discretized with an energy‐momentum conserving integrator. Schemes with this property typically exhibit superior numerical stability properties.

Two different possibilities exist, when applying an energy‐momentum method. The system may be reduced by applying the discrete nullspace method, which yields the elimination of the algebraic constraints [3]. This leads to a formulation with a higher degree of nonlinearity, which complicates the calculation of the gradients, that are necessary for the applied optimal control method. Alternatively, the index 3‐DAEs may be used directly. Previously, this has been done in [1] within an energy preserving direct transcription method. In that case, the simple structure of the discrete equations of motion facilitates the calculation of the gradients, which may be used for calculating the discrete necessary conditions of optimality. These equations can be solved by Newton's method.

We test the different formulations with the help of an underactuated overhead crane as numerical example. This example is taken from [4], where it was used in the context of trajectory tracking. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Sensitivity Analysis of Plaque Components within Arterial Wall Simulations
Authors: Brinkhues Sarah , Tielke Anna‐Katharina , Schröder Jörg
Published: November 2010

In this contribution we focus on a sensitivity analysis of arterial wall simulations with respect to atherosclerotic plaque components. For the simulations we use patient specific arterial wall geometries gained from medical imaging techniques. The technique used here is the Intravascular Ultra Sound Virtual Histology (IVUS‐VH). The resulting discretization is used for the simulation of a diseased artery with plaque components. The material parameters for the arterial layers are based on uniaxial tension tests, whereas the plaque parameters are chosen in a physiologically suitable range. One final goal is to study the sensitivity of the resulting deformation and stress distribution in the arterial wall with respect to the variation of the material parameters of the plaque. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling the interaction between athlete and sports surfaces
Authors: Körner Claudia , Seemann Wolfgang
Published: November 2010

Sports surfaces are often seen as one possible factor for sports injuries as the vertical ground reaction force (VGRF) depends not only on the athlete's movement but also on the mechanical properties of the ground. Therefore, the athlete‐surface‐interaction has to be analysed in order to minimize the loading on the athlete. The aim of this work is to understand the behaviour during landing and the associated impact forces during ground contact. Thus a simplified mechanical model is presented. Results for feasible surface material parameters are identified. A first assumption of the effect of the VGRF is presented. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Porous Media Model for the Description of Adaptive Bone Remodelling
Authors: Krause Robert , Markert Bernd , Ehlers Wolfgang
Published: November 2010

Bones are strong and lightweight structures, which mainly consist of extracellular bone matrix. The bone remodelling is a process of resorption followed by replacement of the bone matrix with small changes in shape, which allow the bones to adapt according to the local loading situation.

In the context of the Theory of Porous Media (TPM), a consistent model of bone tissue is introduced, which is able to describe the local accretion and reduction of the extracellular bone matrix. To this end, the bone is treated as an aggregate of two immiscible constituents. In this biphasic macroscopic model, the aggregate consists of the extracellular bone matrix and cells summarised to a solid phase and an interstitial fluid phase comprising nutrients, metabolites and bone precursors. The addition and removal of bone matrix is described by a mass exchange between the constituents, which depends upon the local strain of the material. Additionally, the growth energy is introduced as a non‐mechanical quantity, which measures the average amount of chemical energy available for cell metabolism [1, 2], and thus, controls the growth process. The presented numerical example illustrates the fundamental effects of bone remodelling under varying boundary conditions. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A bioactive interface approach for the simulation of mechanically stimulated osseointegration of hip joint endoprostheses
Authors: Lutz André , Nackenhorst Udo
Published: November 2010

In this contribution, an approach on the mechanically stimulated osseointegration of hip joint endoprostheses considering load cases of daily movements is presented. The mechanical behavior of the bone‐implant interface is modeled with a material model adopted from computational plasticity. Under consideration of a detailed analysis of the interface conditions, limiting factors for the osseointegration process are identified and the bone ingrowth prediction is performed. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mechanical Modeling of Particle‐Droplet Interaction Motivated by the Study of Self‐Cleaning Mechanisms
Authors: Osman Muhammad , Sauer Roger A.
Published: November 2010

Motivated by the study of self‐cleaning surfaces, the interaction between a spherical solid particle and a water droplet is studied on the microsale level, in terms of the balance forces and the surface properties. To define the forces acting on the solid‐liquid interface, the meniscus depression is computed from the Young‐Laplace equation, using a non‐linear finite element formulation. The equilibrium force is derived in terms of the contact angle, particle size, and the penetration. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Influence of Medial and Adventitial Layer on Arterial Adaptation
Authors: Schmid Holger , Poshtan Emad A. , vanHaag Jens , Grytsan Andrey , Itskov Mikhail
Published: November 2010

Material properties in general and layer‐specific stiffness in particular are critical factors to predict the initiation and growth of aneurysms. Previous experimental studies show vastly differing material stiffness and metabolic activity in the media and the adventitia. In this paper a phenomenological model using FEM is applied in order to predict the adaptive response of the arterial wall in different mechanical and metabolic cases. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Improving the inverse kinematics reconstruction of human movement from motion capture data
Authors: Simonidis Christian , Seemann Wolfgang
Published: November 2010

Marker based motion capture methods are well known techniques for the acquisition of human motion. For the kinematic and dynamic analysis the recorded data is usually used to drive a rigid body model of the human body. Skin artifacts, which are caused by skin deformation and displacement of markers with respect to the underlying bone, are regarded as the most critical source of error in the inverse kinematics reconstruction of human movement. State‐of‐the‐art algorithms use optimization and multibody models with joint constraints in order to overcome these effects. This work presents an optimization based inverse kinematics approach, which is able to adapt the model kinematics subject‐specifically and to compute the time trajectories of kinematic variables from marker data including velocity and acceleration. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Biomechanical modelling of cellular articular cartilage replacement tissues
Authors: Stoffel Marcus , Yi Jeong Hun , Weichert Dieter , Gavenis Karsten , Müller‐Rath Ralf
Published: November 2010

The aim of the present study is to investigate the strength and damping properties of cellular articular cartilage replacement material. For this purpose, a viscoelastic‐diffusion model for the acellular water‐saturated condensed collagen gel type I is proposed and validated experimentally. Moreover, a remodelling law for the cell seeded collagen gel is introduced. For an experimental study of the interaction between fibre growth and mechanical stimulation, bioreactors are developed and histological investigations are carried out. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Experimental and numerical investigations in skeletal muscle modelling
Authors: Sturmat Maike , Kober Cornelia , Böl Markus
Published: November 2010

In the present paper, a method to compare displacement results of a muscle contraction simulation with results of optical experiments is proposed. A human skeletal muscle has been reconstructed to a volume element out of real two‐dimensional MRI data. The surrounding tissue has also been taken into account in order to describe the interaction with other components in a realistic way. These regions of the interface have been supported by several spring stiffness. The numerical model has been fitted by this stiffness on one significant node. The results shown satisfied agreement with the optical experiments. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A Microscopic model for a cell‐seeded material
Authors: Yi Jeong Hun , Stoffel Marcus , Weichert Dieter , Gavenis Karsten , Müller‐Rath Ralf
Published: November 2010

The aim of the present paper is to account for the growth of fiber which is observed in a cell‐seeded material stimulated in a bioreactor. For this purpose, the change of mass is considered in the balance laws, and the deformation energy is assumed to be a function of varying mass and the Helmholtz free‐energy. Fiber growth at the microscopic level causes a macroscopic change of the material's mechanical properties. The study is a first approach towards a micromechanical model accounting for remodelling in cartilage replacement materials. In so doing, constitutive equations for renewable soft tissues are proposed. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Analysis of damage and fracture mechanisms on the micro‐scale
Authors: Albrecht Daniel , Brünig Michael
Published: November 2010

The paper deals with generalized damage and failure criteria taking into account different mechanisms on the micro‐scale. Some micro‐mechanical numerical results are discussed and compared with the macroscopic analysis based on the continuum damage model. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Effects of the material gradation on the SIFs of a crack in a 2‐D FGM plate under thermal shock
Authors: Ekhlakov Alexander , Khay Oksana , Zhang Chuanzeng
Published: November 2010

Crack analysis of linear coupled thermoelasticity in two‐dimensional, isotropic, non‐homogeneous and linear elastic functionally graded materials subjected to thermal shock is performed by using a boundary‐domain element method. The material parameters are assumed to be continuous functions of the spatial coordinates. Fundamental solutions of linear coupled thermoelasticity for the corresponding isotropic, homogeneous and linear elastic solids in Laplace‐transformed domain are applied in the boundary‐domain integral formulation. A collocation method is implemented for the numerical solution. Numerical examples for an exponential gradation of the material parameters are presented and discussed. The influences of the material gradation on the stress intensity factors are investigated. (© 2010 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)