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Berlin, Germany

Selen F.,Yalova University | Can V.,Helmholtz Institute | Can V.,Technical University of Istanbul | Temel G.,Yalova University
RSC Advances | Year: 2016

Polyacrylamide (PAAm) hydrogels were prepared by micellar copolymerization methodology in the presence of acrylamide and photo-decomposable hydrophobic crosslinker (diacrylated Irgacure-2959). After the synthesis of hydrophobically functionalized hydrogels via free radical copolymerization, gel samples were exposed to UV irradiation for different time intervals between 0 and 17 hours in aqueous medium. According to the results of swelling and compression tests, the physical properties of the hydrogels were altered by UV exposure time. The swelling degree of the hydrogels increased gradually with the irradiation time. Moreover, the 17 h irradiated hydrogel sample was entirely decomposed at the end of the swelling test. According to Scanning Electron Microscopy images, UV irradiated hydrogel samples exhibited an apparent degradation behavior. © The Royal Society of Chemistry 2016. Source


Paffen C.L.E.,University Utrecht | Van der Stigchel S.,Helmholtz Institute
Attention, Perception, and Psychophysics | Year: 2010

Although it has been argued that visual attention and the dynamics of binocular rivalry are closely linked, strong evidence for this proposition is still lacking. Here, we investigate how perceptual alternations during binocular rivalry are affected by spatial attention by employing a cuing paradigm. We show a tight link between the occurrence of perceptual alternations and the spatiotemporal properties of visual attention: Alternations occurred earlier and more frequently at locations where visual attention was summoned by an exogenous cue. We argue that cuing a location where rival images are presented leads to a transient increase in the effective contrast of these rival images. This transient increase in effective contrast increases the probability of an alternation at that location. Furthermore, we suggest that an occipito-fronto-parietal network known to be involved in selective attention and binocular rivalry mediates perceptual alternations by boosting the neural response at attended locations. © 2010 The Psychonomic Society, Inc. Source


Kumar V.J.,Indian Institute of Technology Madras | Blazek V.,Helmholtz Institute
2013 IEEE International Conference on Smart Instrumentation, Measurement and Applications, ICSIMA 2013 | Year: 2013

Photo-plethysmo-graphy (PPG) is a noninvasive method of obtaining a signal proportional to blood volume changes using light. From the initial trials seven decades back, the PPG technique has grown leaps and bounds and today its application has become indispensible not only during surgical procedures but also in patient monitoring in critical care environment. This paper traces the path of advancement of this technique and highlights the research outcomes of an "Indo German" collaborative research between Indian Institute of Technology Madras, Chennai, India and Technical University (RWTH) Aachen, Germany funded by ministry of science (BMBF), Germany, Research projects funded by Department of Science and Technology and Department of Biotechnology, Government of India. © 2013 IEEE. Source


Graefe R.,Helmholtz Institute | Henseler A.,ReinVAD GmbH | Steinseifer U.,Helmholtz Institute
Artificial Organs | Year: 2016

Pump gaps are the most critical regions in a rotary blood pump when it comes to blood trauma in the form of hemolysis, protein destruction, and platelet activation. This study investigated six pump design parameters affecting the flow in a radial pump gap. A multivariate approach was employed to determine individual and quantitative parameter effects on blood trauma as well as parameter interactions. To consider the effect of shear stress and blood cell residence time, a validated numerical Lagrangian particle tracking approach was used. Based on the results, small-diameter pumps can be as blood compatible, if not more blood compatible, as large-diameter pumps as long as identical circumferential velocities and clearance gaps are maintained. Furthermore, the results indicate that an eccentric rotor position in the casing is not harmful and that a pressure difference generating washout flow and thereby reducing the cell residence time is of significant importance. © 2016 Wiley Periodicals, Inc. and International Center for Artificial Organs and Transplantation. Source


Klinge U.,RWTH Aachen | Klinge U.,Helmholtz Institute | Klink C.D.,RWTH Aachen | Klosterhalfen B.,Institute For Pathologie
Zentralblatt fur Chirurgie - Zeitschrift fur Allgemeine, Viszeral- und Gefasschirurgie | Year: 2010

Modern meshes permit a radical treatment of hernias, an expectation that Billroth articulated already more than 100years ago. Because clinicaltrials are insufficient to evaluate the distinct effects of modified mesh materials in regard to tissue biocompatibility and functionality, a basic understanding of the physico-chemical properties is essential for a rational selection of the most appropriate device. Experimental data indicate that particularly the meshs porosity is of outstanding importance, resulting from the demanded tensile strength as well as the employed fibre material. Considering that different operation techniques require different mesh materials, specific requirements are discussed using the example of intraabdominal meshes, of parastomal meshes, of meshes in areas with bacterial contamination and of meshes in the hiatus region. Considering the late manifestation of some complications even after many years, any thorough quality control should include an assessment of explanted implant failures in addition to clinical experience. © Georg Thieme Verlag KG Stuttgart. Source

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