@article{MansurovDigelBiisenbaevetal.2012, author = {Mansurov, Z. and Digel, Ilya and Biisenbaev, M. and Savistkaya, I. and Kistaubaeva, A. and Akimbekov, N. and Zhubanova, A.}, title = {Bio-composite material on the basis of carbonized rice husk in biomedicine and environmental applications}, series = {Eurasian Chemico-Technological Journal}, volume = {14}, journal = {Eurasian Chemico-Technological Journal}, number = {2}, publisher = {Institute of Combustion Problems}, address = {Almaty}, issn = {2522-4867}, doi = {10.18321/ectj105}, pages = {115 -- 131}, year = {2012}, language = {en} } @article{Staat2012, author = {Staat, Manfred}, title = {Limit and shakedown analysis under uncertainty}, series = {Tap chi Khoa hoc \& ung dung - Dai hoc Ton Duc Thang}, volume = {19}, journal = {Tap chi Khoa hoc \& ung dung - Dai hoc Ton Duc Thang}, pages = {45 -- 47}, year = {2012}, language = {en} } @article{NomdedeuWillenSchiefferetal.2012, author = {Nomdedeu, Mar Monsonis and Willen, Christine and Schieffer, Andre and Arndt, Hartmut}, title = {Temperature-dependent ranges of coexistence in a model of a two-prey-one-predator microbial food web}, series = {Marine Biology}, volume = {159}, journal = {Marine Biology}, number = {11}, publisher = {Springer}, address = {Berlin}, issn = {1432-1793}, doi = {10.1007/s00227-012-1966-x}, pages = {2423 -- 2430}, year = {2012}, abstract = {The objective of our study was to analyze the effects of temperature on the population dynamics of a three-species food web consisting of two prey bacteria (Pedobacter sp. and Acinetobacter johnsonii) and a protozoan predator (Tetrahymena pyriformis) as model organisms. We assessed the effects of temperature on the growth rates of all three species with the objective of developing a model with four differential equations based on the experimental data. The following hypotheses were tested at a theoretical level: Firstly, temperature changes can affect the dynamic behavior of a system by temperature-dependent parameters and interactions and secondly, food web response to temperature cannot be derived from the single species temperature response. The main outcome of the study is that temperature changes affect the parameter range where coexistence is possible within all three species. This has significant consequences on our ideas regarding the evaluation of effects of global warming.}, language = {en} } @article{HasanKeilStaatetal.2012, author = {Hasan, Istabrak and Keil, Ludger and Staat, Manfred and Wahl, Gerhard and Bourauel, Christoph}, title = {Determination of the frictional coefficient of the implant-antler interface : experimental approach}, series = {Biomedical Engineering / Biomedizinische Technik}, volume = {57}, journal = {Biomedical Engineering / Biomedizinische Technik}, number = {5}, publisher = {De Gruyter}, address = {Berlin}, issn = {1862-278X}, pages = {359 -- 363}, year = {2012}, abstract = {The similar bone structure of reindeer antler to human bone permits studying the osseointegration of dental implants in the jawbone. As the friction is one of the major factors that have a significant influence on the initial stability of immediately loaded dental implants, it is essential to define the frictional coefficient of the implant-antler interface. In this study, the kinetic frictional forces at the implant-antler interface were measured experimentally using an optomechanical setup and a stepping motor controller under different axial loads and sliding velocities. The corresponding mean values of the static and kinetic frictional coefficients were within the range of 0.5-0.7 and 0.3-0.5, respectively. An increase in the frictional forces with increasing applied axial loads was registered. The measurements showed an evidence of a decrease in the magnitude of the frictional coefficient with increasing sliding velocity. The results of this study provide a considerable assessment to clarify the suitable frictional coefficient to be used in the finite element contact analysis of antler specimens.}, language = {en} } @article{PoghossianWeilBaeckeretal.2012, author = {Poghossian, Arshak and Weil, M. H. and B{\"a}cker, Matthias and Mayer, D. and Sch{\"o}ning, Michael Josef}, title = {Field-effect Devices Functionalised with Gold-Nanoparticle/Macromolecule Hybrids: New Opportunities for a Label-Free Biosensing}, series = {Procedia Engineering}, journal = {Procedia Engineering}, number = {47}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1877-7058}, doi = {10.1016/j.proeng.2012.09.136}, pages = {273 -- 276}, year = {2012}, abstract = {Field-effect capacitive electrolyte-insulator-semiconductor (EIS) sensors functionalised with citrate-capped gold nanoparticles (AuNP) have been used for the electrostatic detection of macromolecules by their intrinsic molecular charge. The EIS sensor detects the charge changes in the AuNP/macromolecule hybrids induced by the adsorption or binding events. A feasibility of the proposed detection scheme has been exemplary demonstrated by realising EIS sensors for the detection of poly-D-lysine molecules.}, language = {en} } @article{MiyamotoIchimuraWagneretal.2012, author = {Miyamoto, K. and Ichimura, H. and Wagner, Torsten and Yoshinobu, T. and Sch{\"o}ning, Michael Josef}, title = {Chemical Imaging of ion Diffusion in a Microfluidic Channel}, series = {Procedia Engineering}, journal = {Procedia Engineering}, number = {47}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1877-7058}, doi = {10.1016/j.proeng.2012.09.289}, pages = {886 -- 889}, year = {2012}, abstract = {The chemical imaging sensor is a chemical sensor which is capable of visualizing the spatial distribution of chemical species in sample solution. In this study, a novel measurement system based on the chemical imaging sensor was developed to observe the inside of a Y-shaped microfluidic channel while injecting two sample solutions from two branches. From the collected chemical images, it was clearly observed that the injected solutions formed laminar flows in the microfluidic channel. In addition, ion diffusion across the laminar flows was observed. This label-free method can acquire quantitative data of ion distribution and diffusion in microfluidic devices, which can be used to determine the diffusion coefficients, and therefore, the molecular weights of chemical species in the sample solution.}, language = {en} } @article{WagnerShigiaharaMiyamotoetal.2012, author = {Wagner, Torsten and Shigiahara, N. and Miyamoto, K. and Suzurikawa, J. and Finger, F. and Sch{\"o}ning, Michael Josef and Yoshinobu, T.}, title = {Light-addressable Potentiometric Sensors and Light-addressable Electrodes as a Combined Sensor-and-manipulator Microsystem with High Flexibility}, series = {Procedia Engineering}, journal = {Procedia Engineering}, number = {47}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1877-7058}, doi = {10.1016/j.proeng.2012.09.290}, pages = {890 -- 893}, year = {2012}, abstract = {This work describes the novel combination of the light-addressable electrode (LAE) and the light-addressable potentiometric sensor (LAPS) into a microsystem set-up. Both the LAE as well as the LAPS shares the principle of addressing the active spot by means of a light beam. This enables both systems to manipulate resp. to detect an analyte with a high spatial resolution. Hence, combining both principles into a single set-up enables the active stimulation e.g., by means of electrolysis and a simultaneous observation e.g., the response of an entrapped biological cell by detection of extracellular pH changes. The work will describe the principles of both technologies and the necessary steps to integrate them into a single set-up. Furthermore, examples of application and operation of such systems will be presented.}, language = {en} } @article{IkenKirsanovLeginetal.2012, author = {Iken, Heiko and Kirsanov, D. and Legin, A. and Sch{\"o}ning, Michael Josef}, title = {Novel Thin-Film Polymeric Materials for the Detection of Heavy Metals}, series = {Procedia Engineering}, journal = {Procedia Engineering}, number = {47}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1877-7058}, doi = {10.1016/j.proeng.2012.09.148}, pages = {322 -- 325}, year = {2012}, abstract = {A variety of transition metals, e.g., copper, zinc, cadmium, lead, etc. are widely used in industry as components for wires, coatings, alloys, batteries, paints and so on. The inevitable presence of transition metals in industrial processes implies the ambition of developing a proper analytical technique for their adequate monitoring. Most of these elements, especially lead and cadmium, are acutely toxic for biological organisms. Quantitative determination of these metals at low activity levels in different environmental and industrial samples is therefore a vital task. A promising approach to achieve an at-side or on-line monitoring on a miniaturized and cost efficient way is the combination of a common potentiometric sensor array with heavy metal-sensitive thin-film materials, like chalcogenide glasses and polymeric materials, respectively.}, language = {en} } @article{HuckPoghossianWagneretal.2012, author = {Huck, Christina and Poghossian, Arshak and Wagner, Patrick and Sch{\"o}ning, Michael Josef}, title = {Combined amperometric/field-effect sensor for the detection of dissolved hydrogen}, series = {Sensors and actuators B: Chemical}, volume = {187}, journal = {Sensors and actuators B: Chemical}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0925-4005}, doi = {10.1016/j.snb.2012.10.050}, pages = {168 -- 173}, year = {2012}, abstract = {Real-time and reliable monitoring of the biogas process is crucial for a stable and efficient operation of biogas production in order to avoid digester breakdowns. The concentration of dissolved hydrogen (H₂) represents one of the key parameters for biogas process control. In this work, a one-chip integrated combined amperometric/field-effect sensor for monitoring the dissolved H₂ concentration has been developed for biogas applications. The combination of two different transducer principles might allow a more accurate and reliable measurement of dissolved H₂ as an early warning indicator of digester failures. The feasibility of the approach has been demonstrated by simultaneous amperometric/field-effect measurements of dissolved H₂ concentrations in electrolyte solutions. Both, the amperometric and the field-effect transducer show a linear response behaviour in the H₂ concentration range from 0.1 to 3\% (v/v) with a slope of 198.4 ± 13.7 nA/\% (v/v) and 14.9 ± 0.5 mV/\% (v/v), respectively.}, language = {en} } @article{MuribTranCeunincketal.2012, author = {Murib, Mohammed S. and Tran, Anh Quang and Ceuninck, Ward de and Sch{\"o}ning, Michael Josef and Nesladek, Milos and Serpeng{\"u}zel, Ali and Wagner, Patrick}, title = {Analysis of an optical biosensor based on elastic light scattering from diamond-, glass-, and sapphire microspheres}, series = {Physica Status Solidi A}, volume = {209}, journal = {Physica Status Solidi A}, number = {9}, publisher = {Wiley-VCH}, address = {Weinheim}, issn = {1862-6319}, doi = {10.1002/pssa.201100795}, pages = {1804 -- 1810}, year = {2012}, abstract = {Deoxyribonucleic acid (DNA) and protein recognition are now standard tools in biology. In addition, the special optical properties of microsphere resonators expressed by the high quality factor (Q-factor) of whispering gallery modes (WGMs) or morphology dependent resonances (MDRs) have attracted the attention of the biophotonic community. Microsphere-based biosensors are considered as powerful candidates to achieve label-free recognition of single molecules due to the high sensitivity of their WGMs. When the microsphere surface is modified with biomolecules, the effective refractive index and the effective size of the microsphere change resulting in a resonant wavelength shift. The transverse electric (TE) and the transverse magnetic (TM) elastic light scattering intensity of electromagnetic waves at 600 and 1400 nm are numerically calculated for DNA and unspecific binding of proteins to the microsphere surface. The effect of changing the optical properties was studied for diamond (refractive index 2.34), glass (refractive index 1.50), and sapphire (refractive index 1.75) microspheres with a 50 µm radius. The mode spacing, the linewidth of WGMs, and the shift of resonant wavelength due to the change in radius and refractive index, were analyzed by numerical simulations. Preliminary results of unspecific binding of biomolecules are presented. The calculated shift in WGMs can be used for biomolecules detection.}, language = {en} } @article{BassamHeschelerTemizArtmannetal.2012, author = {Bassam, Rasha and Hescheler, J{\"u}rgen and Temiz Artmann, Ayseg{\"u}l and Artmann, Gerhard and Digel, Ilya}, title = {Effects of spermine NONOate and ATP on the thermal stability of hemoglobin}, series = {BMC Biophysics}, volume = {5}, journal = {BMC Biophysics}, publisher = {BioMed Central}, address = {London}, issn = {2046-1682}, doi = {10.1186/2046-1682-5-16}, pages = {Art. 16}, year = {2012}, abstract = {Background Minor changes in protein structure induced by small organic and inorganic molecules can result in significant metabolic effects. The effects can be even more profound if the molecular players are chemically active and present in the cell in considerable amounts. The aim of our study was to investigate effects of a nitric oxide donor (spermine NONOate), ATP and sodium/potassium environment on the dynamics of thermal unfolding of human hemoglobin (Hb). The effect of these molecules was examined by means of circular dichroism spectrometry (CD) in the temperature range between 25°C and 70°C. The alpha-helical content of buffered hemoglobin samples (0.1 mg/ml) was estimated via ellipticity change measurements at a heating rate of 1°C/min. Results Major results were: 1) spermine NONOate persistently decreased the hemoglobin unfolding temperature T u irrespectively of the Na + /K + environment, 2) ATP instead increased the unfolding temperature by 3°C in both sodium-based and potassium-based buffers and 3) mutual effects of ATP and NO were strongly influenced by particular buffer ionic compositions. Moreover, the presence of potassium facilitated a partial unfolding of alpha-helical structures even at room temperature. Conclusion The obtained data might shed more light on molecular mechanisms and biophysics involved in the regulation of protein activity by small solutes in the cell.}, language = {en} } @article{GutheilBergGrotendorst2012, author = {Gutheil, Inge and Berg, Tommy and Grotendorst, Johannes}, title = {Performance Analysis of Parallel Eigensolvers of two Libraries on BlueGene/P}, series = {Journal of Mathematics and Systems Science}, volume = {2}, journal = {Journal of Mathematics and Systems Science}, number = {4}, publisher = {David Publishing}, address = {Libertyville}, issn = {2159-5291}, doi = {10.17265/2159-5291/2012.04.003}, pages = {231 -- 236}, year = {2012}, abstract = {Many applications in computational science and engineering require the computation of eigenvalues and vectors of dense symmetric or Hermitian matrices. For example, in DFT (density functional theory) calculations on modern supercomputers 10\% to 30\% of the eigenvalues and eigenvectors of huge dense matrices have to be calculated. Therefore, performance and parallel scaling of the used eigensolvers is of upmost interest. In this article different routines of the linear algebra packages ScaLAPACK and Elemental for parallel solution of the symmetric eigenvalue problem are compared concerning their performance on the BlueGene/P supercomputer. Parameters for performance optimization are adjusted for the different data distribution methods used in the two libraries. It is found that for all test cases the new library Elemental which uses a two-dimensional element by element distribution of the matrices to the processors shows better performance than the old ScaLAPACK library which uses a block-cyclic distribution.}, language = {en} } @article{Grotendorst2012, author = {Grotendorst, Johannes}, title = {IAS Winter School: Hierarchical Methods for Dynamics in Complex Molecular Systems}, series = {Innovatives Supercomputing in Deutschland : inSiDE. 10 (2012), H. 1}, journal = {Innovatives Supercomputing in Deutschland : inSiDE. 10 (2012), H. 1}, publisher = {-}, pages = {104}, year = {2012}, language = {en} } @article{AtlasBrealeyDharetal.2012, author = {Atlas, Glen and Brealey, David and Dhar, Sunil and Dikta, Gerhard and Singer, Meryvn}, title = {Additional hemodynamic measurements with an esophageal Doppler monitor: a preliminary report of compliance, force, kinetic energy, and afterload in the clinical setting}, series = {Journal of clinical monitoring and computing}, journal = {Journal of clinical monitoring and computing}, number = {26}, publisher = {Springer Nature}, address = {London}, isbn = {1573-2614}, doi = {10.1007/s10877-012-9386-5}, pages = {473 -- 482}, year = {2012}, abstract = {The esophageal Doppler monitor (EDM) is a minimally-invasive hemodynamic device which evaluates both cardiac output (CO), and fluid status, by estimating stroke volume (SV) and calculating heart rate (HR). The measurement of these parameters is based upon a continuous and accurate approximation of distal thoracic aortic blood flow. Furthermore, the peak velocity (PV) and mean acceleration (MA), of aortic blood flow at this anatomic location, are also determined by the EDM. The purpose of this preliminary report is to examine additional clinical hemodynamic calculations of: compliance (C), kinetic energy (KE), force (F), and afterload (TSVRi). These data were derived using both velocity-based measurements, provided by the EDM, as well as other contemporaneous physiologic parameters. Data were obtained from anesthetized patients undergoing surgery or who were in a critical care unit. A graphical inspection of these measurements is presented and discussed with respect to each patient's clinical situation. When normalized to each of their initial values, F and KE both consistently demonstrated more discriminative power than either PV or MA. The EDM offers additional applications for hemodynamic monitoring. Further research regarding the accuracy, utility, and limitations of these parameters is therefore indicated.}, language = {en} } @article{SchusserPoghossianBaeckeretal.2012, author = {Schusser, Sebastian and Poghossian, Arshak and B{\"a}cker, Matthias and Leinhos, Marcel and Wagner, Patrick and Sch{\"o}ning, Michael Josef}, title = {Characterization of biodegradable polymers with capacitive field-effect sensors}, series = {Sensors and actuators B: Chemical}, volume = {187}, journal = {Sensors and actuators B: Chemical}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0925-4005}, doi = {10.1016/j.snb.2012.07.099}, pages = {2 -- 7}, year = {2012}, abstract = {In vitro studies of the degradation kinetic of biopolymers are essential for the design and optimization of implantable biomedical devices. In the presented work, a field-effect capacitive sensor has been applied for the real-time and in situ monitoring of degradation processes of biopolymers for the first time. The polymer-covered field-effect sensor is, in principle, capable to detect any changes in bulk, surface and interface properties of the polymer induced by degradation processes. The feasibility of this approach has been experimentally proven by using the commercially available biomedical polymer poly(D,L-lactic acid) (PDLLA) as a model system. PDLLA films of different thicknesses were deposited on the Ta₂O₅-gate surface of the field-effect structure from a polymer solution by means of spin-coating method. The polymer-modified field-effect sensors have been characterized by means of capacitance-voltage and impedance-spectroscopy method. The degradation of the PDLLA was accelerated by changing the degradation medium from neutral (pH 7.2) to alkaline (pH 9) condition, resulting in drastic changes in the capacitance and impedance spectra of the polymer-modified field-effect sensor.}, language = {en} } @article{KirchnerOberlaenderFriedrichetal.2012, author = {Kirchner, Patrick and Oberl{\"a}nder, Jan and Friedrich, Peter and Berger, J{\"o}rg and Rysstad, Gunnar and Sch{\"o}ning, Michael Josef and Keusgen, Michael}, title = {Realisation of a calorimetric gas sensor on polyimide foil for applications in aseptic food industry}, series = {Sensors and Actuators B: Chemical}, volume = {170}, journal = {Sensors and Actuators B: Chemical}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0925-4005}, doi = {10.1016/j.snb.2011.01.032}, pages = {60 -- 66}, year = {2012}, abstract = {A calorimetric gas sensor is presented for the monitoring of vapour-phase H2O2 at elevated temperature during sterilisation processes in aseptic food industry. The sensor was built up on a flexible polyimide foil (thickness: 25 μm) that has been chosen due to its thermal stability and low thermal conductivity. The sensor set-up consists of two temperature-sensitive platinum thin-film resistances passivated by a layer of SU-8 photo resist and catalytically activated by manganese(IV) oxide. Instead of an active heating structure, the calorimetric sensor utilises the elevated temperature of the evaporated H2O2 aerosol. In an experimental test rig, the sensor has shown a sensitivity of 4.78 °C/(\%, v/v) in a H2O2 concentration range of 0\%, v/v to 8\%, v/v. Furthermore, the sensor possesses the same, unchanged sensor signal even at varied medium temperatures between 210 °C and 270 °C of the gas stream. At flow rates of the gas stream from 8 m3/h to 12 m3/h, the sensor has shown only a slightly reduced sensitivity at a low flow rate of 8 m3/h. The sensor characterisation demonstrates the suitability of the calorimetric gas sensor for monitoring the efficiency of industrial sterilisation processes.}, language = {en} } @article{MiyamotoKanekoMatsuoetal.2012, author = {Miyamoto, Ko-ichiro and Kaneko, Kazumi and Matsuo, Akira and Wagner, Torsten and Kanoh, Shin{\´i}chiro and Sch{\"o}ning, Michael Josef and Yoshinobu, Tatsuo}, title = {Miniaturized chemical imaging sensor system using an OLED display panel}, series = {Sensors and Actuators B: Chemical}, volume = {170}, journal = {Sensors and Actuators B: Chemical}, publisher = {Elsevier}, address = {Amsterdam}, issn = {0925-4005}, doi = {10.1016/j.snb.2011.02.029}, pages = {82 -- 87}, year = {2012}, abstract = {The chemical imaging sensor is a semiconductor-based chemical sensor that can visualize the two-dimensional distribution of specific ions or molecules in the solution. In this study, we developed a miniaturized chemical imaging sensor system with an OLED display panel as a light source that scans the sensor plate. In the proposed configuration, the display panel is placed directly below the sensor plate and illuminates the back surface. The measured area defined by illumination can be arbitrarily customized to fit the size and the shape of the sample to be measured. The waveform of the generated photocurrent, the current-voltage characteristics and the pH sensitivity were investigated and pH imaging with this miniaturized system was demonstrated.}, language = {en} } @article{KotliarLanzlHanssenetal.2012, author = {Kotliar, Konstantin and Lanzl, Ines M. and Hanssen, Henner and Eberhardt, Karla and Vilser, Walthard and Halle, Martin and Heemann, Uwe and Schmidt-Trucks{\"a}ss, Arno and Baumann, Marcus}, title = {Does increased blood pressure rather than aging influence retinal pulse wave velocity?}, series = {Investigative Ophthalmology \& Visual Science, IOVS}, volume = {53}, journal = {Investigative Ophthalmology \& Visual Science, IOVS}, number = {4}, publisher = {ARVO}, address = {Rockville, Md.}, issn = {0146-0404}, doi = {10.1167/iovs.11-8815}, pages = {2119 -- 2126}, year = {2012}, abstract = {Purpose: It was demonstrated previously that retinal pulse wave velocity (rPWV) as a measure of retinal arterial stiffness is increased in aged anamnestically healthy volunteers compared with young healthy subjects. Using novel methodology of rPWV assessment this finding was confirmed and investigated whether it might relate to the increased blood pressure usually accompanying the aging process, rather than to the aging itself. Methods: A total of 12 young 25.5-year-old (24.0-28.8) [median(1st quartile-3rd quartile)] and 12 senior 68.5-year-old (63.8-71.8) anamnestically healthy volunteers; and 12 senior 63.0-year-old (60.8-65.0) validated healthy volunteers and 12 young 33.0-year-old (29.5-35.0) hypertensive patients were examined. Time-dependent alterations of vessel diameter were assessed by the Dynamic Vessel Analyzer in a retinal artery of each subject. The data were filtered and processed using mathematical signal analysis and rPWVs were calculated. Results: rPWV amounted to 1200 (990-1470) RU (relative units)/s in the hypertensive group and to 1040 (700-2230) RU/s in anamnestically healthy seniors. These differed significantly from rPWVs in young healthy group (410 [280-500] RU/s) and in validated healthy seniors (400 [320-510] RU/s). rPWV associated with age and mean arterial pressure (MAP) in the pooled cohort excluded validated healthy seniors. In a regression model these associations remain when alternately adjusted for MAP and age. When including validated healthy seniors in the pooled cohort only association with MAP remains. Conclusions: Both aging (with not excluded cardiovascular risk factors) and mild hypertension are associated with elevated rPWV. rPWV increases to a similar extent both in young mildly hypertensive subjects and in aged anamnestically healthy persons. Healthy aging is not associated with increased rPWV.}, language = {en} } @article{NovacekTranKlingeetal.2012, author = {Novacek, V. and Tran, Thanh Ngoc and Klinge, U. and Tolba, R. H. and Staat, Manfred and Bronson, D. G. and Miesse, A. M. and Whiffen, J. and Turquier, F.}, title = {Finite element modelling of stapled colorectal end-to-end anastomosis : Advantages of variable height stapler design}, series = {Journal of Biomechanics}, volume = {45}, journal = {Journal of Biomechanics}, number = {115}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-2380}, doi = {10.1016/j.jbiomech.2012.07.021}, pages = {2693 -- 2697}, year = {2012}, abstract = {The impact of surgical staplers on tissues has been studied mostly in an empirical manner. In this paper, finite element method was used to clarify the mechanics of tissue stapling and associated phenomena. Various stapling modalities and several designs of circular staplers were investigated to evaluate the impact of the device on tissues and mechanical performance of the end-to-end colorectal anastomosis. Numerical simulations demonstrated that a single row of staples is not adequate to resist leakage due to non-linear buckling and opening of the tissue layers between two adjacent staples. Compared to the single staple row configuration, significant increase in stress experienced by the tissue at the inner staple rows was observed in two and three rows designs. On the other hand, adding second and/or third staple row had no effect on strain in the tissue inside the staples. Variable height design with higher staples in outer rows significantly reduced the stresses and strains in outer rows when compared to the same configuration with flat cartridge.}, language = {en} } @article{NguyenDuongTranetal.2012, author = {Nguyen, Nhu Huynh and Duong, Minh Tuan and Tran, Thanh Ngoc and Pham, Phu Tinh and Grottke, O. and Tolba, R. and Staat, Manfred}, title = {Influence of a freeze-thaw cycle on the stress-stretch curves of tissues of porcine abdominal organs}, series = {Journal of Biomechanics}, volume = {45}, journal = {Journal of Biomechanics}, number = {14}, publisher = {Elsevier}, address = {Amsterdam}, issn = {1873-2380}, doi = {10.1016/j.jbiomech.2012.07.008}, pages = {2382 -- 2386}, year = {2012}, abstract = {The paper investigates both fresh porcine spleen and liver and the possible decomposition of these organs under a freeze-thaw cycle. The effect of tissue preservation condition is an important factor which should be taken into account for protracted biomechanical tests. In this work, tension tests were conducted for a large number of tissue specimens from twenty pigs divided into two groups of 10. Concretely, the first group was tested in fresh state; the other one was tested after a freeze-thaw cycle which simulates the conservation conditions before biomechanical experiments. A modified Fung model for isotropic behavior was adopted for the curve fitting of each kind of tissues. Experimental results show strong effects of the realistic freeze-thaw cycle on the capsule of elastin-rich spleen but negligible effects on the liver which virtually contains no elastin. This different behavior could be explained by the autolysis of elastin by elastolytic enzymes during the warmer period after thawing. Realistic biomechanical properties of elastin-rich organs can only be expected if really fresh tissue is tested. The observations are supported by tests of intestines.}, language = {en} }