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Search Results: 1 - 10 of 4724 matches for " Ulrich Hofmann "
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Emergent Inert Adjoint Scalar Field in SU(2) Yang-Mills Thermodynamics due to Coarse-Grained Topological Fluctuations
Ulrich Herbst,Ralf Hofmann
ISRN High Energy Physics , 2012, DOI: 10.5402/2012/373121
Dynamic Evacuation Architecture using Context-Aware Policy Management
Ulrich Hofmann,,Armin Veichtlbauer,Ilka Miloucheva
International Journal of Computer Science & Applications , 2009,
Sleep, Neuroengineering and Dynamics
Jens Christian Claussen,Ulrich G. Hofmann
Quantitative Biology , 2013, DOI: 10.1007/s11571-012-9204-2
Abstract: Modeling of consciousness-related phenomena and neuroengineering are fields that are rapidly growing together. We review recent approaches and developments and point out some promising directions of future research: Understanding the dynamics of consciousness states and associated oscillations, pathological oscillations as well as their treatment by stimulation, neuroprosthetics and brain-computer-interface approaches, and stimulation approaches that probe, influence and strengthen memory consolidation. In all these fields, computational models connect theory, neurophysiology and neuroengineering research and pave a way towards medical applications.
High-Q MEMS Resonators for Laser Beam Scanning Displays
Ulrich Hofmann,Joachim Janes,Hans-Joachim Quenzer
Micromachines , 2012, DOI: 10.3390/mi3020509
Abstract: This paper reports on design, fabrication and characterization of high-Q MEMS resonators to be used in optical applications like laser displays and LIDAR range sensors. Stacked vertical comb drives for electrostatic actuation of single-axis scanners and biaxial MEMS mirrors were realized in a dual layer polysilicon SOI process. High Q-factors up to 145,000 have been achieved applying wafer level vacuum packaging technology including deposition of titanium thin film getters. The effective reduction of gas damping allows the MEMS actuator to achieve large amplitudes at high oscillation frequencies while driving voltage and power consumption can be minimized. Exemplarily shown is a micro scanner that achieves a total optical scan angle of 86 degrees at a resonant frequency of 30.8 kHz, which fulfills the requirements for HD720 resolution. Furthermore, results of a new wafer based glass-forming technology for fabrication of three dimensionally shaped glass lids with tilted optical windows are presented.
Cellular Modulation of Polymeric Device Surfaces: Promise of Adult Stem Cells for Neuro-Prosthetics
Anja Richter,Andreas Moser,Ulrich G. Hofmann,Sandra Danner
Frontiers in Neuroscience , 2011, DOI: 10.3389/fnins.2011.00114
Abstract: Minimizing the foreign body response is seen as one critical research strategy for implants especially when designed for immune-privileged organs like the brain. The context of this work is to improve deep brain stimulating devices used in a consistently growing spectrum of psychomotor and psychiatric diseases mainly in form of stiff electrodes. Based on the compliance match hypothesis of biocompatibility we present another step forward using flexible implant materials covered with brain cell-mimicking layers. We covered two types of flexible polyimide films with glandular stem cells derived from pancreatic acini. Using real time-PCR and fluorescent immunocytochemistry we analyzed markers representing various cell types of all three germ layers and stemness. The results demonstrate an unchanged differentiation potential of the polyimide fixated cells as measured by mRNA and protein level. Additionally we developed a fibrinous hydrogel coating to protect them against shear forces upon eventual implantation. By repeating previous analysis and additional metabolism tests for all stages we corroborate the validity of this improvement. Consequently we assume that a stem cell-containing cover may provide a native, fully and actively integrating brain-mimicking interface to the neuropil.
An improved technique of image analysis for IACTs and IACT Systems
M. Ulrich,A. Daum,G. Hermann,W. Hofmann
Physics , 1997,
Abstract: In order to better utilize the information contained in the shower images generated by imaging Cherenkov telescopes (IACTs) equipped with cameras with small pixels, images are fit to a parametrization of image shapes gained from Monte Carlo simulations, treating the shower direction, impact point, and energy as free parameters. Monte Carlo studies for a system of IACTs predict an improvement of order 1.5 in the angular resolution. The fitting technique can also be applied to single-telescope images; simulations indicate that the shower direction in space can be reconstructed event-by-event with a resolution of 0.16 deg. to 0.20 deg., allowing to generate genuine source maps. Data from Crab observations with a single HEGRA telescope confirm this prediction.
Modeling effect of GABAergic current in a basal ganglia computational model
Felix Njap,Jens Christian Claussen,Andreas Moser,Ulrich G. Hofmann
Quantitative Biology , 2013, DOI: 10.1007/s11571-012-9203-3
Abstract: Electrical high frequency stimulation (HFS) of deep brain regions is a method shown to be clinically effective in different types of movement and neurological disorders. In order to shed light on its mode of action a computational model of the basal ganglia network coupled the HFS as injection current into the cells of the subthalamic nucleus (STN). Its overall increased activity rendered a faithful transmission of sensorimotor input through thalamo-cortical relay cells possible. Our contribution uses this model by Rubin and Terman (J Comput Neurosci, 16, 211-223, 2004) as a starting point and integrates recent findings on the importance of the extracellular concentrations of the inhibiting neurotransmitter GABA. We are able to show in this computational study that besides electrical stimulation a high concentration of GABA and its resulting conductivity in STN cells is able to re-establish faithful thalamocortical relaying, which otherwise broke down in the simulated parkinsonian state.
N-acetylcyteine and flavonoid rich diet: The protective effect of 15 different antioxidants on cigarette smoke-damaged primary human osteoblasts  [PDF]
Sabrina Ehnert, Stefan D?bele, Karl Friedrich Braun, Britta Burkhardt, Valeska Hofmann, Mario Hausmann, José Tomás Ega?a, Ulrich St?ckle, Thomas Freude, Andreas Klaus Nussler
Advances in Bioscience and Biotechnology (ABB) , 2012, DOI: 10.4236/abb.2012.38139
Abstract: Cigarette consumption increases oxidative stress in many organs. Increased oxidative stress harms bone cells, which negatively affects bone-matter and -stability. This leads to an increased fracture risk and delayed fracture healing in smokers. A supporting therapy with antioxidants could be of great benefit for surgeons dealing with delayed fracture healing due to increased oxidative stress. In this article we complement and compare our published data with hitherto unpublished data and show the protective effect of 15 different antioxidants on cigarette smoke induced damage in primary human osteoblasts. Exposure to cigarette smoke medium (CSM) rapidly induces formation of ROS in osteoblasts in a concentration- and time-dependent manner. Massive cell damage is seen already after 4 h (EC50 ≈ 0.75 OD320). Pre-, co- and post-incubation with the different antioxidants reduces the formation of ROS and consequently improves the viability of the CSM exposed osteoblasts. Small compounds, e.g. N-acetylcysteine, proved highly effective if pre- or co-incubated before exposure to the CSM. Thus, they are good candidates for acute therapy support as they can be administered in high doses. However, our data suggest that a balanced daily diet could lead to an accumulation of various natural antioxidants (flavonoids) that effectively protect osteoblasts from oxidative stress-induced damage in all three settings investigated. Together with their partly phytoestrogenic properties this may even abate alterations in bone and thus reduce fracture risk on the long run.
A New Method for in Situ Measurement of Bt-Maize Pollen Deposition on Host-Plant Leaves
Frieder Hofmann,Mathias Otto,Ulrike Kuhn,Steffi Ober,Ulrich Schlechtriemen,Rudolph V?gel
Insects , 2011, DOI: 10.3390/insects2010012
Abstract: Maize is wind pollinated and produces huge amounts of pollen. In consequence, the Cry toxins expressed in the pollen of Bt maize will be dispersed by wind in the surrounding vegetation leading to exposure of non-target organisms (NTO). NTO like lepidopteran larvae may be affected by the uptake of Bt-pollen deposited on their host plants. Although some information is available to estimate pollen deposition on host plants, recorded data are based on indirect measurements such as shaking or washing off pollen, or removing pollen with adhesive tapes. These methods often lack precision and they do not include the necessary information such as the spatial and temporal variation of pollen deposition on the leaves. Here, we present a new method for recording in situ the amount and the distribution of Bt-maize pollen deposited on host plant leaves. The method is based on the use of a mobile digital microscope (Dino-Lite Pro, including DinoCapture software), which can be used in combination with a notebook in the field. The method was evaluated during experiments in 2008 to 2010. Maize pollen could be correctly identified and pollen deposition as well as the spatial heterogeneity of maize pollen deposition was recorded on maize and different lepidopteran host plants ( Centaurea scabiosa, Chenopodium album, Rumex spp., Succina pratensis and Urtica dioica) growing adjacent to maize fields.
In vivo monitoring of glial scar proliferation on chronically implanted neural electrodes by fiber optical coherence tomography
Yijing Xie,Christina Hassler,Robert D. Kirch,Thomas Stieglitz,Ulrich G. Hofmann
Frontiers in Neuroengineering , 2014, DOI: 10.3389/fneng.2014.00034
Abstract: In neural prosthetics and stereotactic neurosurgery, intracortical electrodes are often utilized for delivering therapeutic electrical pulses, and recording neural electrophysiological signals. Unfortunately, neuroinflammation impairs the neuron-electrode-interface by developing a compact glial encapsulation around the implants in long term. At present, analyzing this immune reaction is only feasible with post-mortem histology; currently no means for specific in vivo monitoring exist and most applicable imaging modalities can not provide information in deep brain regions. Optical coherence tomography (OCT) is a well established imaging modality for in vivo studies, providing cellular resolution and up to 1.2 mm imaging depth in brain tissue. A fiber based spectral domain OCT was shown to be capable of minimally invasive brain imaging. In the present study, we propose to use a fiber based spectral domain OCT to monitor the progression of the tissue's immune response through scar encapsulation progress in a rat animal model. A fine fiber catheter was implanted in rat brain together with a flexible polyimide microelectrode in sight both of which acts as a foreign body and induces the brain tissue immune reaction. OCT signals were collected from animals up to 12 weeks after implantation and thus gliotic scarring in vivo monitored for that time. Preliminary data showed a significant enhancement of the OCT backscattering signal during the first 3 weeks after implantation, and increased attenuation factor of the sampled tissue due to the glial scar formation.
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