bluuebunny/crossref_metadata_2025 huggingface dataset:
Dimensionality reduction of medical image descriptors for multimodal image registration
Authors: Degen Johanna , Modersitzki Jan , Heinrich Mattias P.
Published: September 2015

Defining similarity forms a challenging and relevant research topic in multimodal image registration. The frequently used mutual information disregards contextual information, which is shared across modalities. A recent popular approach, called modality independent neigh-bourhood descriptor, is based on local self-similarities of image patches and is therefore able to capture spatial information. This image descriptor generates vectorial representations, i.e. it is multidimensional, which results in a disadvantage in terms of computation time. In this work, we present a problem-adapted solution for dimensionality reduction, by using principal component analysis and Horn’s parallel analysis. Furthermore, the influence of dimensionality reduction in global rigid image registration is investigated. It is shown that the registration results obtained from the reduced descriptor have the same high quality in comparison to those found for the original descriptor.
Towards contactless optical coherence elastography with acoustic tissue excitation
Authors: Düwel Dino , Otte Christoph , Schulz Kevin , Saathoff Thore , Schlaefer Alexander
Published: September 2015

Elastography presents an interesting approach to complement image data with mechanical tissue properties. Typically, the tissue is excited by direct contact to a probe. We study contactless elastography based on optical coherence tomography (OCT) and dynamic acoustic tissue excitation with airborne sound. We illustrate the principle and an implementation using sound waves of 135 Hz to excite the tissue. The displacement is measured and results of several tests indicate the feasibility to obtain a qualitative measure of the mechanical tissue properties. The approach is interesting for optical palpation, e.g., to enhance navigation and tissue characterization in minimally invasive and robot-assisted surgery.
Development and implementation of algorithms for automatic and robust measurement of the 2D:4D digit ratio using image data
Authors: Koch Robert , Haßlmeyer Erik , Tantinger Daniel , Rulsch Martin , Weigand Christian , Struck Matthias
Published: September 2015

Early in the 20th century it could be observed that the finger lengths of second (2D) and fourth digit (4D) represents a sexually dimorphic feature, whereby in general the second digit is longer than the fourth digit for men and vice versa for women. In the early 1980s first studies could show a correlation between the 2D:4D ratio and the concentration of androgens one is exposed to during a short window within the prenatal development phase. Therefore, the 2D:4D digit ratio can serve as an additional marker for certain physiological and psychological traits like fertility, assertiveness, aggressiveness and alcohol addiction. Manual measurements are the established method to retrieve the finger lengths e.g. by using a ruler on printed scans of hands. For higher reliability these extremely time-consuming procedures have to be done multiple times. In this contribution two automated procedures are proposed to reduce the time for measurements whilst maintaining the accuracy. A deviation of maximal 2% from the manual measurement could be achieved for more than 75% of the 22 participants.
Video tracking of swimming rodents on a reflective water surface
Authors: Christ Olaf , Hofmann Ulrich G.
Published: September 2015

Animal models are an essential testbed for new devices on their path from the bench to the patient. Potential impairments by brain stimulation are often investigated in water mazes to study spatial memory and learning. Video camera based tracking systems exist to quantify rodent behaviour, but reflections of ambient lighting on the water surface and artefacts due to the waves caused by the swimming animal cause errors. This often requires tweaking of algorithms and parameters, or even potentially modifying the lab setup. In the following, we provide a simple solution to alleviate these problem using a combination of region based tracking and independent multimodal background subtraction (IMBS) without hav ing to tweak a plethora of parameters.
Artifacts in field free line magnetic particle imaging in the presence of inhomogeneous and nonlinear magnetic fields
Authors: Medimagh Hanne , Weissert Patrick , Bringout Gael , Bente Klaas , Weber Matthias , Gräfe Ksenija , Cordes Aileen , Buzug Thorsten M.
Published: September 2015

Introduction: Magnetic Particle Imaging (MPI) is an emerging medical imaging modality that detects super-paramagnetic particles exploiting their nonlinear magnetization response. Spatial encoding can be realized using a Field Free Line (FFL), which is generated, rotated and translated through the Field of View (FOV) using a combination of magnetic gradient fields and homogeneous excitation fields. When scaling up systems and/or enlarging the FOV in comparison to the scanner bore, ensuring homogeneity and linearity of the magnetic fields becomes challenging. The present contribution describes the first comprehensive, systematic study on the influence of magnetic field imperfections in FFL MPI. Methods: In a simulation study, 14 different FFL scanner setups have been examined. Starting from an ideal scanner using perfect magnetic fields, defined imperfections have been introduced in a range of configurations (nonlinear gradient fields, inhomogeneous excitation fields, or inhomogeneous receive fields, or a combination thereof). In the first part of the study, the voltage induced in the receive channels parallel and perpendicular to the FFL translation have been studied for discrete FFL angles. In the second part, an imaging process has been simulated comparing different image reconstruction approaches. Results: The induced voltage signals demonstrate illustratively the effect of the magnetic field imperfections. In images reconstructed using a Radon-based approach, the magnetic field imperfections lead to pronounced artifacts, especially if a deconvolution using the point spread function is performed. In images reconstructed using a system function based approach, variations in local image quality become visible. Conclusion: For Radon-based image reconstruction in FFL MPI in the presence of inhomogeneous and nonlinear magnetic fields, artifact correction methods will have to be developed. In this regard, a first approach has recently been presented by another group. Further research is required to elucidate the influence of magnetic field imperfections in MPI using a system function based approach.
Intravascular optical coherence tomography (OCT) as an additional tool for the assessment of stent structures
Authors: Hoffmann Thomas , Boese Axel , Glaßer Sylvia , Skalej Martin , Beuing Oliver
Published: September 2015

Evaluation of the vascular stent position, shape and correct expansion has a high relevance in therapy and diagnosis. Hence, the wall apposition in vessel areas with differing diameters and the appearance of torsions or structural defects of the implant body caused by catheter based device dropping are of special interest. Neurovascular implants like braided flow diverter and laser cut stents consist of metal struts and wires with diameters of about 40 µm. Depending on the implants material composition, visibility is poor with conventional 2D X-ray fluoroscopic and radiographic imaging. The metal structures of the implants also lead to artifacts in 3D X-ray images and can hamper the assessment of the device position. We investigated intravascular optical coherence tomography (OCT) as a new imaging tool for the evaluation of the vascular stent position, its shape and its correct expansion for 3 different vascular implants.
Simple concept for a wide-field lensless digital holographic microscope using a laser diode
Authors: Adinda-Ougba A. , Koukourakis N. , Gerhardt N. C. , Hofmann M. R.
Published: September 2015

Wide-field, lensless digital holographic microscopy is a new microscopic imaging technique for telemedicine and for resource limited setting [1]. In this contribution we propose a very simple wide-field lensless digital holographic microscope using a laser diode. It is based on in-line digital holography which is capable to provide amplitude and phase images of a sample resulting from numerical reconstruction. The numerical reconstruction consists of the angular spectrum propagation method together with a phase retrieval algorithm. Amplitude and phase images of the sample with a resolution of ∽2 µm and with ∽24 mm2 field of view are obtained. We evaluate our setup by imaging first the 1951 USAF resolution test chart to verify the resolution. Second, we record holograms of blood smear and diatoms. The individual specimen can be easily identified after the numerical reconstruction. Our system is a very simple, compact and low-cost possibility of realizing a microscope capable of imaging biological samples. The availability of the phase provide topographic information of the sample extending the application of this system to be not only for biological sample but also for transparent microstructure. It is suitable for fault detection, shape and roughness measurements of these structures.
Respiratory surface motion measurement by Microsoft Kinect
Authors: Ortmüller J. , Gauer T. , Wilms M. , Handels H. , Werner R.
Published: September 2015

In radiotherapy of abdominal and thoracic tumors, respiratory motion is a problem for an accurate treatment. Most current motion compensation techniques rely on externally acquired breathing signals of the patient. The systems in clinical use usually work with 1D surface motion signals to describe internal structure respiratory motion patterns. As a 1D signal is not able to describe complex motion patterns and breathing variations, in this work the Microsoft Kinect, which can record multidimensional respiratory surface motion signals, is proposed to be used instead. For the Kinect, a clinically acceptable measurement setup is designed and Kinect measurements are compared to the Varian RPM system (clinical standard). The results show that the signals are well aligned. An additional comparison of Kinect signals from different regions of interest on the chest further reveals variations between them. This illustrates that the use of a system that provides multidimensional signals is worthwhile; the knowledge about breathing variations could be applied for optimization of current clinical workflows.
Experimental computer tomograph
Authors: Heinemann D. , Keller A. , Jannek D.
Published: September 2015

The computed tomography is one of the most important medical instruments, allowing the non-invasive visualization of cross sections which are free from superpositions. Since 2000 an experimental computer tomo-graph of the third generation for the purpose of education and research was set up and further developed. Besides the mechanical construction design reconstruction algorithms, including certain corrections of the measured data were developed and implemented. In 2013 iterative reconstruction methods were investigated and implemented for advanced reconstructions and dose reduction using various ray tracing algorithms. The new reconstruction technique leads to improvements in image quality and low dose reconstructions.
Contribution of brownian rotation and particle assembly polarisation to the particle response in magnetic particle spectrometry
Authors: von Gladiss Anselm , Graeser Matthias , Lüdtke-Buzug Kerstin , Buzug Thorsten M.
Published: September 2015

The spectrometry of super-paramagnetic iron-oxide nanoparticles is a central tool for characterising particles that are used in Magnetic Particle Imaging. In Magnetic Particle Imaging, nanoparticles are excited by a magnetic field and the particle response is measured. Until now, the influence of the trajectory sequence on the dynamic particle relaxation has not been scoped. With a multi-dimensional Magnetic Particle Spectrometer, analysing the behaviour of different trajectories on the particles becomes possible. In this paper, the contribution of Brownian rotation and assembly polarisation on the particle signal is being analysed.
Construction of a device for magnetic separation of superparamagnetic iron oxide nanoparticles
Authors: Kläser Kerstin , Graeser Matthias , Steinhagen Dirk , Luedtke-Buzug Kerstin
Published: September 2015

Suspensions of iron oxide particles, so called ferrofluids, are successfully used in various technical, biochemical and medical applications. For example they find use in the area of sensor engineering, magnetic resonance imaging (MRI) and especially magnetic particle imaging (MPI). MPI is a new tomographic imaging technique that determines the spatial distribution of superparamagnetic iron oxide nanoparticles (SPIONs). Besides a very high spatial and temporal resolution MPI provides quantitative realtime imageing. The nanoparticles cause a magnetization change that can be measured. As the particle size distribution has a huge impact on the magnetization behavior is an important parameter for optimization. While synthesizing, SPIONs particles with various dimensions are formed what necessitates a systematically separation by size. For this purpose a construction of a simple device for magnetic separation of SPIONs has been developed. First attemps of separation show the potential of this method.
Automated respiratory therapy system based on the ARDSNet protocol with systemic perfusion control
Authors: Pomprapa Anake , Walter Marian , Braun Wolfgang , Lachmann Burkhard , Leonhardt Steffen
Published: September 2015

A medical expert system of automatic artificial ventilation is set up in a star topology with additional closed-loop hemodynamic control. Arterial blood pressure (MAP) is controlled by noradrenaline (NA) as a controlling variable. The overall patient-in-the-loop expert system can intensively and intelligently perform a long-term treatment based on the Acute Respiratory Distress Syndrome Network (ARDSNet) protocol. Three main goals are actively carried out, namely the stabilization and regulation of oxygenation, plateau pressure and blood pH value. The developed system shows a distinctive experimental result based on a 31.5-kg pig, in order to fulfil the ventilatory goals and to ensure proper systemic perfusion. Hence, this system has enormous potentials to realize a commercial system for individual patient with ARDS.
A generic concept for the development of model-guided clinical decision support systems
Authors: Denecke Kerstin , Chalopin Claire
Published: September 2015

Disease development and progression are very complex processes which make clinical decision making non-trivial. On the one hand, examination results that are stored in multiple formats and data types in clinical information systems need to be considered. Beyond, biological or molecular-biological processes can influence clinical decision making. So far, biological knowledge and patient data is separated from each other. This complicates inclusion of all relevant knowledge and information into the decision making. In this paper, we describe a concept of model-based decision support that links knowledge about biological processes, treatment decisions and clinical data. It consists of three models: 1) a biological model, 2) a decision model encompassing medical knowledge about the treatment workflow and decision parameters, and 3) a patient data model generated from clinical data. Requirements and future steps for realizing the concept will be presented and it will be shown how the concept can support the clinical decision making.
Evaluation of local alterations in femoral bone mineral density measured via quantitative CT
Authors: Sitzer A. , Aulmann L. , Wendlandt R. , Handels H. , Weyers I. , Schulz A. P. , Buzug T. M.
Published: September 2015

The aim of this study was to investigate the accuracy of bone mineral density (BMD) determined by quantitative computed tomography (qCT) based on in situ and ex situ scans of cadavers of variable stature. The influence of surrounding tissue on the quantification of CT images of ex situ scanned femora was investigated in air and in water and compared with the in situ scanned femora. The study showed that the surrounding tissue has an impact on the grey value-based representation of the scanned object as well as on the calibration of BMD, influencing the determination of BMD. Local differences in BMD of up to 17.5% were observed, which might originate from beam hardening artifacts.
A machine learning approach for planning valve-sparing aortic root reconstruction
Authors: Hagenah J. , Scharfschwerdt M. , Schlaefer A. , Metzner C.
Published: September 2015

Choosing the optimal prosthesis size and shape is a difficult task during surgical valve-sparing aortic root reconstruction. Hence, there is a need for surgery planning tools. Common surgery planning approaches try to model the mechanical behaviour of the aortic valve and its leaflets. However, these approaches suffer from inaccuracies due to unknown biomechanical properties and from a high computational complexity. In this paper, we present a new approach based on machine learning that avoids these problems. The valve geometry is described by geometrical features obtained from ultrasound images. We interpret the surgery planning as a learning problem, in which the features of the healthy valve are predicted from these of the dilated valve using support vector regression (SVR). Our first results indicate that a machine learning based surgery planning can be possible.
Measuring different oxygenation levels in a blood perfusion model simulating the human head using NIRS
Authors: Rackebrandt K. , Gehring H.
Published: September 2015

The oxygenation, perfusion and metabolism of the brain - segmented in both hemispheres - can be estimated from the oxygenation and hemoglobin levels of the venous blood in the cerebral efferent vessels.

We present a phantom based model to simulate the anatomical target region which was connected to hemodynamic perfusion circuit to provide different oxygenation rates inside of the simulated target vessel (measurement cell) reproducible. A triple-wavelength (770, 808 and 850 nm) multi-distance NIRS sensor (6 photodiodes, linearly arranged, separated 6 mm each) was used to detect these different saturation levels.

The results illustrate the capability to measure the optical property variation of hemoglobin due to oxygenation and deoxygenation processes in a specific vessel. Based on these first results a series of measurements is introduced to correlate the amount of reflected light to the actual oxygen saturation of the blood.
Multisegmental fusion of the lumbar spine a curse or a blessing?
Authors: Bauer S. , Paulus D.
Published: September 2015

Excessive mechanical load of the spinal structures during unfavorable movements in daily life can lead to degenerative damages especially of the lumbar spine. If the affected structures are damaged in such a way that conventional therapy does not improve the situation, often a surgery is unavoidable. One surgical method is the fusion of the affected spinal segments. In particularly difficult cases, the fusion may even extend over more than one functional spinal unit. An appropriate method for the estimation of the biomechanical effects of such interventions to adjacent vertebral segments is the computer simulation. This paper presents a 3D-MultiBodySimulation(MBS-) model of the lumbar spine with realistic surfaces and included intersegmental discs as well as ligamental structures. For these elements the physical behavior like force-deformation relations and characteristic curves for the torque-angle relations are formulated. The facet joints are modeled as cartilage, in order to simulate the contact between the corresponding articular surfaces. With this simulation, the effects of mono- and multisegmental fusions to the lumbar structures can be analyzed. The comparison of the simulations shows a redistribution of loads within the intervertebral discs. In the simulation case of monosegmental spinal fusion, the intervertebral disc below the fused segment are more loaded than in the simulated healthy state. The validation of the model was carried out by comparing the results with FE-simulations, various of vitro experiments and experimental data from biomedical literature.
Mathematical, numerical and in-vitro investigation of cooling performance of an intra-carotid catheter for selective brain hypothermia
Authors: Wolfertz J. , Meckel S. , Guber A. , Cattaneo G.
Published: September 2015

Therapeutic hypothermia (TH) has become an established neuroprotective therapy for patients after cardiac arrest [1, 2]. Selective brain cooling represents a promising way to shorten the time to reach the target brain temperature and additionally spare other organs from damage caused by temperature decrease. We present the investigation of the cooling performance of a single-balloon catheter dimensioned for the placement within the common carotid artery (CCA) by means of three different approaches: mathematical, numerical and in-vitro testing.
An ideally parameterized unscented Kalman filter for the inverse problem of electrocardiography
Authors: Ritter Christian , Schulze Walther H. W. , Potyagaylo Danila , Dössel Olaf
Published: September 2015

ECG imaging as noninvasive method is aiming to reconstruct the distribution of the transmembrane voltage amplitudes (TMVs) from the body surface potential map (BSPM). Due to the ill-posedness, standard approaches like the Tikhonov regularization method cause blurring and artefacts in the solution. To suppress blurring and artefacts, this work investigated a model based approach, the unscented Kalman filter (UKF). The intention of this paper is to show the potential of an UKF approach by using an idealized parametrization.
Realtime assessment of foot orientation by Accelerometers and Gyroscopes
Authors: Seel Thomas , Graurock David , Schauer Thomas
Published: September 2015

Foot orientation can be assessed in realtime by means of a foot-mounted inertial sensor. We consider a method that uses only accelerometer and gyroscope readings to calculate the foot pitch and roll angle, i.e. the foot orientation angle in the sagittal and frontal plane, respectively. Since magnetometers are avoided completely, the method can be used indoors as well as in the proximity of ferromagnetic material and magnetic disturbances. Furthermore, we allow for almost arbitrary mounting orientation in the sense that we only assume one of the local IMU coordinate axes to lie in the sagittal plane of the foot. The method is validated with respect to a conventional optical motion capture system in trials with transfemoral amputees walking with shoes and healthy subjects walking barefoot, both at different velocities. Root mean square deviations of less than 4° are found in all scenarios, while values near 2° are found in slow shoe walking. This demonstrates that the proposed method is suitable for realtime application such as the control of FES-based gait neuroprostheses and active orthoses.
Image based reconstruction for cystoscopy
Authors: Brischwein Matthias , Wittenberg Thomas , Bergen Tobias
Published: September 2015

This paper summarizes our initial efforts to reconstruct the urinary bladder from endoscopic images acquired in the clinical routine. We found that up to now, only very few attempts have been reported which achieve a true 3D reconstruction of the human bladder. One promising approach which yields a geometric reconstruction up to scale from a monocular stream of images is highlighted and our initial results obtained from adapting the method for its use in clinical cystoscopy are presented.
Smartphone supported upper limb prosthesis
Authors: Hepp D. , Kirsch J. , Capanni F.
Published: September 2015

State of the art upper limb prostheses offer up to six active DoFs (degrees of freedom) and are controlled using different grip patterns. This low number of DoFs combined with a machine-human-interface which does not provide control over all DoFs separately result in a lack of usability for the patient. The aim of this novel upper limb prosthesis is both offering simplified control possibilities for changing grip patterns depending on the patients’ priorities and the improvement of grasp capability. Design development followed the design process requirements given by the European Medical Device Directive 93/42 ECC and was structured into the topics mechanics, software and drive technology. First user needs were identified by literature research and by patient feedback. Consequently, concepts were evaluated against technical and usability requirements. A first evaluation prototype with one active DoF per finger was manufactured. In a second step a test setup with two active DoF per finger was designed. The prototype is connected to an Android based smartphone application. Two main grip patterns can be preselected in the software application and afterwards changed and used by the EMG signal. Three different control algorithms can be selected: “all-day”, “fine” and “tired muscle”. Further parameters can be adjusted to customize the prosthesis to the patients’ needs. First patient feedback certified the prosthesis an improved level of handling compared to the existing devices. Using the two DoF test setup, the possibilities of finger control with a neural network are evaluated at the moment. In a first user feedback test, the smartphone based software application increased the device usability, e.g. the change within preselected grip patterns and the “tired muscle” algorithm. Although the overall software application was positively rated, the handling of the prosthesis itself needs to be proven within a patient study to be performed next. The capability of the neural network to control the hand has also to be proven in a next step.
Evaluation of adhesion promoters for Parylene C on gold metallization
Authors: Radun V. , von Metzen R. P. , Stieglitz T. , Bucher V. , Stett A.
Published: September 2015

Delamination of thin film polymeric coatings from metallization layers is a common cause of failure in biomedical implants. To address the problem, different adhesion promotion techniques can be applied which include surface pre-treatment with oxygen and argon plasma and the use of different adhesion promoters. In this paper the applicability of titanium (Ti), silicon oxide (SiOx), diamond-like carbon (DLC), tetramethylsilane (TMS) and aluminium oxide (AlOx) as adhesion promoters is evaluated. A cross cut, peel and scratch test are used to qualify and quantify the adhesion before and after storage in phosphate buffered saline (PBS) for 48 hours at a temperature of 37 °C. Promising results could be achieved by a combination of Ti and DLC as well as by AlOx.
The influence of metallic ions from CoCr28Mo6 on the osteogenic differentiation and cytokine release of human osteoblasts
Authors: Jonitz-Heincke A , Schröder M , Hansmann D , Utzschneider S. , Kretzer J.P. , Bader R.
Published: September 2015

Inflammatory reactions associated with osteolysis and implant loosening can be the result of generated CoCr particles and the simultaneous release of ions, which are the consequence of wear at the articulating surfaces of metallic implants. By now, there is little knowledge about the influence of CoCr ions on the viability of human osteoblasts (hOB).

Therefore, metallic ions were generated from solid CoCr28Mo6 alloys using electric potentials against hydrogen bridge electrodes. For the cell experiments, hOBs (n ≥ 4) in the third passage were used. Cells were cultured for 24 h before incubated with the generated ion solution in two different concentrations (100 µg/l and 500 µg/l in DMEM with 10 % FCS). Cells incubated without ions served as controls. After 48 h and 96 h cell viability was determined (WST-1 assay, live-dead-stainings). Additionally, gene expression levels of osteogenic markers and cytokines were analysed.

A significant increase of metabolic activity and vital cells could be shown for both ion concentrations. Gene expression of alkaline phosphatase and Col1 was highly induced after 96 h for 100 µg/l whereas Col1 protein was significantly reduced on both time points (48 h: p=0.008 (100 µg/l, 500 µg/l); 96 h: p=0,029 (500 µg/l)) compared to the control. Additionally, MMP1 expression was decreased after 48 h and 96 h. IL6 mRNA was concentration-dependent increased after 48 h whereas a significant decrease could be shown for the highest ion concentration (p=0.029). Compared to the lower ion concentration, IL8, MCP1 (p=0.029) and TNF mRNA were clearly reduced for the higher ion solution after 96 h. Our results suggest that ions from CoCr28Mo6 alloys have only marginal effects on osteoblast viability whereas Col1 expression is reduced and cytokine release is induced. In further studies, the effects of metallic ions and particles from CoCr28Mo6 on other cells will be examined.
Development of a bending test procedure for the characterization of flexible ECoG electrode arrays
Authors: Kohler Fabian , Michiels Rebecca , Schuettler Martin , Stieglitz Thomas
Published: September 2015

An automatized mechanical test has been developed to characterize flexible ECoG and grid electrode arrays under cyclic bending load. Electrodes with different test structures were designed and the bending cycle dependant failure rate was found to follow a Weibull distribution. A corresponding failure mode analysis revealed a characteristic lifetime of more than 25000 bending cycles for some designs. However, design parameters as e.g. a smaller track width reduced this lifetime by a factor of two. In comparison to a similar BMI grid electrode array which was implanted for several months in an animal, failure patterns were comparable to those simulated with the bending test.
Investigation of the dynamic diameter deformation of vascular stents during fatigue testing with radial loading
Authors: Boeck Maria , Kamke F. , Grabow N. , Schmidt W.
Published: September 2015

Endovascular stents are exposed to cyclic loads resulting from daily activity and pulsatile arterial blood pressure. DIN EN ISO 25539-2 and FDA guideline 1545 recommend durability testing, exposing stents to physiological cyclic loads for a 10 year equivalent. For accelerated testing, the simulated deformation has to be comparable to physiological in-vivo deformation. A new test setup is presented to determine diameter deformation of vascular stents during fatigue testing with radial loading.

Methods

The new setup allows the investigation of stents (n = 1–10) up to a length of 200 mm using a CCD line camera independent from special configurations. For demonstration, the radial deformation of two peripheral stents (stent 1: 8.0×40 mm, stent 2: 4.5×40 mm) and coronary stents (stent 3: 2.5×22 mm, stent 4: 4.0×40 mm) is determined as a function of the longitudinal measuring position. The stents are implanted in polyurethane tubes and exposed to physiologically relevant pressure at test frequencies 100 Hz.

Results

In addition to the verification of test frequencies for fatigue testing the setup can also be used for the investigation of radial deformation performance. The results show that radial deformation may vary along the stent length. Larger radial deformation was detected at the middle of the stent. For stent 1 a maximum deformation of 0.21 ± 0.07 mm (± 2.65 %) was measured at 50 ± 40 mmHg, 90 Hz. It was also measured that the radial deformation is dependent on stent design, geometric dimension and external loading.

Conclusion

The new setup allows for test frequency verification for accelerated fatigue testing with radial loading. It is also suitable for more detailed investigation of the radial deformation performance of stents along their longitudinal axis. This is necessary for a better understanding of potential mechanical failure especially in the case of long or overlapping stents.
Würde, Selbstachtung und persönliche Identität
Authors: Neuhäuser Christian
Published: September 2015

Human dignity is a contested and maybe essentially contested concept. One prominent interpretation links dignity with self-respect, claiming that a violation of dignity is a form of disrespect that erodes the grounds of self-respect. However, this linkage of dignity and self-respect does not immediately solve the difficulty of understanding dignity. Self-respect might turn out to be a similarly contested concept, but it might also be more open to analytical scrutiny than dignity is. Following this possibility, I discuss three different contemporary theories that link dignity with self-respect in different ways, which were developed by Peter Schaber, Arnd Pollmann and Ralf Stoecker respectively. I will then argue that those theories present illuminating interpretations of respect, but somewhat neglect a thorough discussion of the self that is to be respected. However, such a discussion of the self or - to express it in a rather less metaphysical way - identity is necessary, or so I will argue, for a full understating of the relation of dignity and self-respect.
Optimized synthesis of 3′-O-aminothymidine and evaluation of its oxime derivative as an anti-HIV agent
Authors: Solyev Pavel N. , Jasko Maxim V. , Martynova Tatiana A. , Kalnina Ludmila B. , Nosik Dmitry N. , Kukhanova Marina K.
Published: September 2015

The synthesis and isolation of 3′-O-aminothymidine oximes have been optimized. Synthesized compounds were characterized by NMR and UV spectral and analytical data. A mixture of previously not reported syn and anti isomers of acetaldoximes was assessed for anti-HIV activity and the prevention of syncytia formation caused by HIV-1 infection.
The role of a caring disposition in service leadership
Authors: Shek Daniel T.L. , Li Xiang
Published: September 2015

A caring disposition is an important and fundamental attribute of a service leader. At the Hong Kong Polytechnic University, a lecture on a caring disposition in the subject “Service Leadership” was designed to help students understand the importance of caring dispositions. The curriculum design with reference to the basic concepts and theories as well as the content of the lecture are presented in this paper. In the first part of the paper, several uncaring cases are presented to serve as negative examples to inspire students’ reflection on caring leaders. Then, the three most important traits of a caring disposition, including awareness, love and nurturing people are introduced. Next, the relationships between a caring disposition and service leadership are analyzed and practical ways of improving a caring disposition are proposed. Finally, the impacts of a caring disposition on the leader-follower relationship are discussed. To provide a general overview of this lecture, the content including detailed lecture sessions and four designed activities relevant to a caring disposition are also presented in the paper.
Numerical Simulation of Liquid-Fueled Detonations by an Eulerian–Lagrangian Model
Authors: Shen Hua , Wang Gang , Liu Kaixin , Zhang Deliang
Published: September 2015

In this paper, an Eulerian–Lagrangian two-phase flow model for liquid-fueled detonations is constructed. The gaseous mixture is described by an Eulerian method, and liquid particles in gaseous mixture are traced by a Lagrangian method. An improved space-time conservation element and solution element (CE/SE) scheme is applied to the simulations of detonations in liquid C
10
H
22
-O
2
/air systems. Different fuel droplet sizes and equivalence ratios are considered in the present study. Interestingly, the numerical results show that liquid-fueled detonations have some difference with gaseous detonations. Especially, a deficit in the propagation velocity compared to the gaseous detonation velocity is observed in mixtures with lean fuel and larger droplet sizes, while an increase in the propagation velocity compared to the gaseous detonation velocity is observed in the mixtures with very rich fuel. The surprising phenomenon is analyzed and discussed with the aid of detailed numerical results. In addition, the formation and propagation of two-phase detonation waves are characterized by series of results and the influence of particle radii is also discussed. All numerical results show that the present model can describe the gas-particle two-phase system accurately, and can be applied to numerical simulations of liquid-fueled detonations.
Fabrication and Mechanical Properties of a Micro/Nanoscale Hybrid Composite
Authors: Wang Genwei , Zhao Han , Bai Jinbo , Zhao Ya-Pu
Published: September 2015

Microscale SiC particles with multiwalled carbon nanotubes grow on were filled in epoxy resin to construct multiscale hybrid composite. Static and dynamic compressive responses of composites were investigated. A dynamic experimental technique, split Hopkinson press bar (SHPB), was introduced to study the constitutive laws of materials at high strain rates. SEM observations show good dispersion of carbon nanotubes and SiC particles, but bad link between SiC particles and carbon nanotubes exists. Experimental results of static and dynamic tests verify that increase of strength happens with SiC/CNT as reinforcement Increment of strength under dynamic loading is bigger than under static loading.
Large Mass Protection with Close-celled Metallic Foams Under Low Velocity Impact: Spring-damper-foam Collision Model
Authors: Li Bin Chao , Zhao Gui Ping , Lu Tian Jian
Published: September 2015

The vibration isolation and energy absorption capability of high porosity metallic foams with closed cells for large mass protection under low velocity impact is theoretically studied. To explore the underlying physical mechanisms of shock attenuation, a double degree of freedom (DDF) spring-damper-foam collision model is developed. The effects of key system parameters (such as spring stiffness, damping ratio, mass ratio, initial velocity and foam thickness) on optimal foam mass and minimum acceleration peak are discussed.
On the Energy of Dynamic Fractures
Authors: Xia Kaiwen , Liu Cangli , Kanopoulos Patrick
Published: September 2015

The validity of the constant propagation fracture energy postulation for dynamic fracture is discussed. As shown from existing direct and indirect experimental results, this assumption may not represent the physical reality. For spontaneous fractures, the fracture energy was shown to increase linearly with the crack length, and for dynamic fractures driven by known amplitude impulsive loading (generated by planar impact), the fracture energy was not a constant either. Despite of its phenomenogical origin, the Broberg’s theory developed for self-similar crack growth works well for both spontaneous fractures and dynamic fractures produced by well defined dynamic loading. In this theory, the fracture energy is not a constant. Furthermore, with given far-field loading or equivalent far-field loading, the crack speed is uniquely determined by a strength-like material parameter. This parameter is related to the cohesive strength as proposed by H. J. Gao for hyperelastic materials in the crack-tip process zone. It is proposed in this work that the strength-like parameter (or equivalently the constant fracture speed) is a better material parameter to describe the dynamic fracture propagation process for most dynamic fractures.
Experimental Study on Dynamic Mechanical Properties of Amphibolites, Sericite-quartz Schist and Sandstone under Impact Loadings
Authors: Liu Jun-Zhong , Xu Jin-Yu , Lv Xiao-Cong , Zhao De-Hui , Leng Bing-Lin
Published: September 2015

In order to investigate rock dynamic mechanical properties of amphibolites, sericite-quartz schist and sandstone under the different strain rates varying from 30 s
-1
to 150 s
-1
, the specimens were subjected to axial impact at different projectile speeds by using the split Hopkinson pressure bar (SHPB) of 100 mm in diameter. The optimal experimental size of rock samples is verified by analyzing the stress equilibrium of cylindrical rock samples in different thicknesses. It has studied the mechanic properties of these three rocks which under impact loadings; and analysed the dynamic compressive strength, failure modes, energy dissipation variation with the strain-rate and the strain-rate hardening effect from the perspective of material microstructure. Experimental results show that the dynamic Young’s modulus of rock samples increase with strain-rate slightly. The dynamic failure modes of different rock samples are always different. When at a lower strain-rate, the damage of sandstone takes a peeling off the external radial tensile failure mode, but that of amphibolites takes axial splitting mode; when at a higher strain-rate, sandstone takes granular crushing failure mode, and that of amphibolites and of sericite-quartz schist take massive crushing mode. Significant strain-rate effect can be represented by a linear relation between the specific energy absorption and the strain-rate

, or between the dynamic strength increase factor η and

.
On the Mutual Effect of the Turbulent Dispersion Model and Thermophoresis on Nanoparticle Deposition
Authors: Mehel Amine , Sagot Benoit , Tanière Anne , Oesterlé Benoit
Published: September 2015

Nanoparticles applications, whether for pharmaceuticals, for environmental assessment or for evaluation of global climatic has led to the use of CFD tools to improve the understanding of their dynamical behaviour (transport, deposition and coagulation).

Due to small particle sizes and low Stokes numbers, nanoparticles are typically considered to deposit at the wall as a combined result of Brownian motion and turbulent dispersion. To simulate these mechanisms in this work, the two-phase flow is computed using a RANS model (Reynolds Averaged Navier-Stokes) for the mean fluid properties, and a Lagrangian tracking approach for the dispersed phase in which the fluctuating fluid velocity at particle location, that ensures the particle turbulent dispersion, is predicted through a user implemented Langevin-based dispersion model.

When a temperature gradient is present, the aerosol particles experience a thermophoretic force in addition to the drag and the Brownian forces. Depending on the temperature gradient and particle size, the thermophoretic force could become the predominant deposition mechanism. This size dependence makes it important to appropriately choose the turbulent dispersion model in wall-bounded turbulent flows. Actually, in most commercial codes, the turbulent dispersion of particles is predicted using the so-called Eddy Interaction Model (EIM), whose major drawback is that it cannot account for turbulence non-homogeneity, thus leading to some unphysical accumulation of low-inertia particles near the wall and therefore to an overestimation of the deposition velocity which is accentuated by thermophoresis. This study shows that turbulent and thermophoretic depositions are not completely independent, since thermophoresis enhances the deposition of particles which are sensitive to the turbulent dispersion model.
Boiling Shocks and Self-Oscillations in Critical Nozzle Flow
Authors: Ivashniov Oleg , Ivashneva Marina
Published: September 2015

Experiments on the depressurization of high-pressure vessels have shown the vaporization to occur in ‘boiling shocks’ moving with the velocity of ∼10 m s−1. This phenomenon was explained by proposing a boiling liquid model accounting for bubble fragmentation. It was shown that an explosive boiling-up was caused by a sharp increase in the interphase area due to a chain process of bubble breakup. In the present study, we use this model, with no change in its free parameters, to simulate the flow in a Laval nozzle. In a critical nozzle flow, boiling occurs to proceed in a shock-type wave as well. It is shown that the formation of boiling shocks may cause autovibrations. The investigation of the shock structure shows that the fulfillment of two conditions is necessary for its realization: Weber number must reach its critical value and the flow velocity must be less than an equilibrium speed of sound. When the conditions cannot be simultaneously realized at a steady-state regime, the flow goes over into a self-oscillation mode.
A Study on Application of Smoothed Particle Hydrodynamics to Multi-Phase Flows
Authors: Szewc K. , Tanière A. , Pozorski J. , Minier J.-P.
Published: September 2015

Smoothed Particle Hydrodynamics (SPH) is a fully Lagrangian, particle-based technique for fluid-flow computations. The main advantage over Eulerian techniques is no requirement of the grid, therefore this is a natural approach to simulate multi-phase flows. The main purpose of this study is an overview and the critical analysis of the SPH variants to see their influence on the flow computations with many components (the historical way of improving the SPH approach). The comparison is performed using common validation (two- and three-dimensional) tests: the Rayleigh-Taylor instability, a square-droplet deformation and a bubble rising in water. The special attention will be given to compare different surface-tension models.
Method of Taylor Expansion Moment Incorporating Fractal Theories for Brownian Coagulation of Fine Particles
Authors: Wan Zhanhong , You Zhenjiang , Sun Zhilin , Yin Wenbin
Published: September 2015

Fine particles aggregating into larger units or flocculation body is a random combination process. Increasing the size and density of flocculation body is the main approach to rapid particle removal or sedimentation in water. Aiming at the Brownian coagulation of fine particles, a new method of Taylor expansion moment construction of fractal flocs has been developed in this paper, incorporating the Taylor expansion approach based on the moment method and the fractal dimension of the floc structure originated from fractal theories. This method successfully overcomes the limit of previous moment methods that require pre-assumed particle size distribution. Results of the zero and second order moments of Brownian flocs from the proposed method are compared with those from the Laguerre method, integral moment method and finite element method. It is found that the higher accuracy and efficiency of computation have been achieved by the new method, compared to the previous ones. Effects of the fractal dimension on the zero and second order moments, geometric average volume and standard deviation are also analyzed using this method. The self-conservation characteristics of particle distribution is observed without presumption of initial distributions.
Numerical Solution of Nonlinear Kaup-Kupershmit Equation, KdV-KdV and Hirota-Satsuma Systems
Authors: Mohebbi Akbar
Published: September 2015

In this work we investigate the numerical solution of Kaup-Kupershmit (KK) equation, KdV-KdV and generalized Hirota-Satsuma (HS) systems. The proposed numerical schemes in this paper are based on fourth-order time-stepping schemes in combination with discrete Fourier transform. We discretize the original partial differential equations (PDEs) with discrete Fourier transform in space and obtain a system of ordinary differential equations (ODEs) in Fourier space which will be solved with fourth order time-stepping methods. After transforming the equations to a system of ODEs, the linear operator in KK and HS equation is diagonal but in KDV-KDV equation is not diagonal. However for KDV-KDV system which is the focus of this paper, we show that the exponential of linear operator and related inverse matrix have definite structure which enable us to implement the methods such as diagonal case. Comparing numerical solutions with exact traveling wave solutions demonstrates that those methods are accurate and readily implemented.