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Search Results: 1 - 10 of 15682 matches for " Christian Wolff "
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Event based classification of Web 2.0 text streams
Andreas Bauer,Christian Wolff
Computer Science , 2012,
Abstract: Web 2.0 applications like Twitter or Facebook create a continuous stream of information. This demands new ways of analysis in order to offer insight into this stream right at the moment of the creation of the information, because lots of this data is only relevant within a short period of time. To address this problem real time search engines have recently received increased attention. They take into account the continuous flow of information differently than traditional web search by incorporating temporal and social features, that describe the context of the information during its creation. Standard approaches where data first get stored and then is processed from a peristent storage suffer from latency. We want to address the fluent and rapid nature of text stream by providing an event based approach that analyses directly the stream of information. In a first step we want to define the difference between real time search and traditional search to clarify the demands in modern text filtering. In a second step we want to show how event based features can be used to support the tasks of real time search engines. Using the example of Twitter we present in this paper a way how to combine an event based approach with text mining and information filtering concepts in order to classify incoming information based on stream features. We calculate stream dependant features and feed them into a neural network in order to classify the text streams. We show the separative capabilities of event based features as the foundation for a real time search engine.
Impact of video quality and wireless network interface on power consumption of mobile devices
Norbert Zsak,Christian Wolff
Computer Science , 2014,
Abstract: During the last years, many improvements were made to the hardware capability of mobile devices. As mobile software also became more interactive and data processing intensive, the increased power demand could not be compensated by the improvements on battery technology. Adaptive systems can help to balance the demand of applications with the limitations of battery resources. For effective systems, the influence of multimedia quality on power consumption of the components of mobile devices needs to be better understood. In this paper, we analyze the impact of video quality and wireless network type on the energy consumption of a mobile device. We have found that the additional power consumption is up to 38% higher when a movie is played over a WiFi network instead from internal memory and 64% higher in case of a mobile network (3G). We have also discovered that a higher movie quality not only affects the power consumption of the CPU but also the power consumption of the WiFi unit by up to 58% and up to 72% respectively on mobile networks.
A Functional Driver Analyzing Concept
Tobias Islinger,Thorsten K?hler,Christian Wolff
Advances in Human-Computer Interaction , 2011, DOI: 10.1155/2011/413964
Abstract: It is evident that a lot of accidents occur because of drowsiness or inattentiveness of the driver. The logical consequence is that we have to find methods to better analyze the driver. A lot of research has been spent on camera-based systems which focus on the driver's eye gaze or his head movement. But there are few systems that provide camera-free driver analyzing. This is the main goal of the work presented here which is structured in three phases, with the operational goal of having a working driver analyzer implemented in a car. The main question is: is it possible to make statements concerning the driver and his state by using vehicle data from the CAN Bus only? This paper describes the current state of driver analyzing, our overall system architecture, as well as future work. At the moment, we focus on detecting the driving style of a person. 1. Introduction Driver analysis (DA) has been an active field of research for years. For example, [1] published an article about driver monitoring already in 2005. Among others, DA can be divided in the following subtopics: driver monitoring, driving style analysis, and merging vehicle data to derive conclusions concerning the driver (The word driver means both, female as well as male drivers. This is also relevant for words like “his” or “him” which reflect also both, female as well as male persons.) and his environment. For our research work, we focus on the following aspects. (i)How can the state of the driver be detected without using a camera or realtime biosensor data like a electrocardiogram (ecd)? (ii)How can we support the driver, depending on his actual driving situation, based on the results of the driver state detection? Driver monitoring is usually performed by cameras installed in the car for detecting the driver's behavior or state, mostly by using infrared cameras ([2, 3], or [1]). There are also first results for noncamera based research on driver analysis: By analyzing analog speed graphs, Rygula [4] makes conclusions about the driving style, speed profile and, depending on driving time and course, aggressiveness of the driver. Therefore, he evaluated ten analog speed graphs for two drivers by comparing their speed profile, their profile referring to the distance, or referring to route and direction. Rygula states that “Even a brake of 45 minutes reduce aggressivity of driving style” ([4, page 79]). A different approach is the research on context recognition in vehicles and the development of a driver model. Ferscha and Riener [5] describe this process of in-car context recognition and
Update: Cytokine Dysregulation in Chronic Nonbacterial Osteomyelitis (CNO)
Sigrun R. Hofmann,Angela Roesen-Wolff,Gabriele Hahn,Christian M. Hedrich
International Journal of Rheumatology , 2012, DOI: 10.1155/2012/310206
Abstract: Chronic nonbacterial osteomyelitis (CNO) with its most severe form chronic recurrent multifocal osteomyelitis (CRMO) is a non-bacterial osteitis of yet unknown origin. Secondary to the absence of both high-titer autoantibodies and autoreactive T lymphocytes, and the association with other autoimmune diseases, it was recently reclassified as an autoinflammatory disorder of the musculoskeletal system. Since its etiology is largely unknown, the diagnosis is based on clinical criteria, and treatment is empiric and not always successful. In this paper, we summarize recent advances in the understanding of possible etiopathogenetic mechanisms in CNO. 1. Introduction Chronic nonbacterial osteomyelitis (CNO) (OMIM number 259680) is an autoinflammatory, noninfectious disorder that affects the skeletal system and has first been described in 1972 [1]. An association with further autoimmune and autoinflammatory disorders such as pustolusis palmoplantaris [2], chronic inflammatory bowel disease (IBD), psoriasis, c-ANCA positive vasculitis, Takayasu’s arteriitis, and deficiency of IL-1 receptor antagonist (DIRA) has been discussed [3–5]. CNO covers a wide clinical spectrum from non- or oligo-symptomatic monofocal bony lesions to its most severe form chronic recurring multifocal osteomyelitis (CRMO). Generally, any skeletal site can be affected. However, metaphyses of long bones are predominantly involved [6] with a predilection for the lower extremities (distal femur, proximal tibia, distal tibia, and distal fibula [7]), followed by the clavicle and spine. A symmetric involvement is common. Systemic symptoms occur in a subset of patients and include low-grade fevers and malaise. Even though Scully et al. (2008) [7] reported a predominance in females (up to 85%), larger studies did not confirm this. However, little is known about the pathophysiology of CNO. Most research articles focus on clinical aspects of CNO, and only few reports discuss putative pathomechanisms underlying this autoinflammatory disorder. 2. Classification, Clinical Picture, Diagnosis, and Treatment Autoinflammatory diseases are rare disorders, characterized by recurrent episodes of fever and inflammation, and mostly affect joints, serosal surfaces, eyes and skin in the absence of high-titer autoantibodies, autoreactive T lymphocytes [11], and underlying infection [7]. In 2006, McGonagle and McDermott [12] suggested a clinical continuum with autoimmune disorders on the one, and autoinflammatory diseases on the other end of the spectrum. Disorders located towards the middle of the continuum exhibit
Cerebral vasculitis associated with Schistosoma mansoni infection
Camuset Guillaume,Wolff Valérie,Marescaux Christian,Abou-Bacar Ahmed
BMC Infectious Diseases , 2012, DOI: 10.1186/1471-2334-12-220
Abstract: Background Cerebral involvement in schistosomiasis is not rare, but it is underdiagnosed because of the lack of clinical suspicion and the frequency of asymptomatic forms. Neurologic complications are generally supported by granuloma formation around ectopic eggs which have migrated to the brain. Moreover, vascular lesions and cerebral arteritis have been well documented in histopathological studies. Nevertheless, cerebral vasculitis in later stages of the Schistosoma mansoni infection have not yet been described in living subjects. Case presentation A 28-year-old french woman had a stroke linked with cerebral vasculitis, 6 monthes after returning from Burkina-Faso. At the same time, a S. mansoni disseminated infection was diagnosed. She suffered from a new stroke after undertaking praziquantel therapy, which lead us to associate the S. mansoni infection and cerebral vasculitis. Conclusion This is the first report of such association, since cerebral vasculitis has never been described in later stages of the S. mansoni infection. Although the causal link between the two pathologies could not be proved, we suggest that S. mansoni is able to cause severe vascular damage in cerebral vessels. Schistosomiasis must be investigated in the event of a brain infarct in young people, particularly in patients originating or returning from an endemic area.
Stimulated Brillouin Scattering in integrated photonic waveguides: forces, scattering mechanisms and coupled mode analysis
Christian Wolff,Michael J. Steel,Benjamin J. Eggleton,Christopher G. Poulton
Physics , 2014, DOI: 10.1103/PhysRevA.92.013836
Abstract: Recent theoretical studies of Stimulated Brillouin Scattering (SBS) in nanoscale devices have led to an intense research effort dedicated to the demonstration and application of this nonlinearity in on-chip systems. The key feature of SBS in integrated photonic waveguides is that small, high-contrast waveguides are predicted to experience powerful optical forces on the waveguide boundaries, which are predicted to further boost the SBS gain that is already expected to grow dramatically in such structures because of the higher mode confinement alone. In all recent treatments, the effect of radiation pressure is included separately from the scattering action that the acoustic field exerts on the optical field. In contrast to this, we show here that the effects of radiation pressure and motion of the waveguide boundaries are inextricably linked. Central to this insight is a new formulation of the SBS interaction that unifies the treatment of light and sound, incorporating all relevant interaction mechanisms --- radiation pressure, waveguide boundary motion, electrostriction and photoelasticity --- from a rigorous thermodynamic perspective. Our approach also clarifies important points of ambiguity in the literature, such as the nature of edge-effects with regard to electrostriction, and of body-forces with respect to radiation pressure. This new perspective on Brillouin processes leads to physical insight with implications for the design and fabrication of SBS-based nanoscale devices.
Impact of nonlinear loss on Stimulated Brillouin Scattering
Christian Wolff,Philipp Gutsche,Michael J. Steel,Benjamin J. Eggleton,Christopher G. Poulton
Physics , 2015, DOI: 10.1364/JOSAB.32.001968
Abstract: We study the impact of two-photon absorption (2PA) and fifth-order nonlinear loss such as 2PA-induced free-carrier absorption in semiconductors on the performance of Stimulated Brillouin Scattering devices. We formulate the equations of motion including effective loss coefficients, whose explicit expressions are provided for numerical evaluation in any waveguide geometry. We find that 2PA results in a monotonic, algebraic relationship between amplification, waveguide length and pump power, whereas fifth-order losses lead to a non-monotonic relationship. We define a figure of merit for materials and waveguide designs in the presence of fifth-order losses. From this, we determine the optimal waveguide length for the case of 2PA alone and upper bounds for the total Stokes amplification for the case of 2PA as well as fifth-order losses. The analysis is performed analytically using a small-signal approximation and is compared to numerical solutions of the full nonlinear modal equations.
Brillouin resonance broadening due to structural variations in nanoscale waveguides
Christian Wolff,Raphael Van Laer,Michael J. Steel,Benjamin J. Eggleton,Christopher G. Poulton
Physics , 2015,
Abstract: We study the impact of structural variations (that is slowly varying geometry aberrations and internal strain fields) on the resonance width and shape of stimulated Brillouin scattering (SBS) in nanoscale waveguides. We find that they lead to an inhomogeneous resonance broadening through two distinct mechanisms: firstly, the acoustic frequency is directly influenced via mechanical nonlinearities; secondly, the optical wave numbers are influenced via the opto-mechanical nonlinearity leading to an additional acoustic frequency shift via the phase-matching condition. We find that this second mechanism is proportional to the opto-mechanical coupling and, hence, related to the SBS-gain itself. It is absent in intra-mode forward SBS, while it plays a significant role in backward scattering. In backward SBS increasing the opto-acoustic overlap beyond a threshold defined by the fabrication tolerances will therefore no longer yield the expected quadratic increase in overall Stokes amplification. Our results can be transferred to other micro- and nano-structured waveguide geometries such as photonic crystal fibres.
Power limits and a figure of merit for stimulated Brillouin scattering in the presence of third and fifth order loss
Christian Wolff,Philipp Gutsche,Michael J. Steel,Benjamin J. Eggleton,Christopher G. Poulton
Physics , 2015, DOI: 10.1364/OE.23.026628
Abstract: We derive a set of design guidelines and a figure of merit to aid the engineering process of on-chip waveguides for strong Stimulated Brillouin Scattering (SBS). To this end, we examine the impact of several types of loss on the total amplification of the Stokes wave that can be achieved via SBS. We account for linear loss and nonlinear loss of third order (two-photon absorption, 2PA) and fifth order, most notably 2PA-induced free carrier absorption (FCA). From this, we derive an upper bound for the output power of continuous-wave Brillouin-lasers and show that the optimal operating conditions and maximal realisable Stokes amplification of any given waveguide structure are determined by a dimensionless parameter $\mathcal{F}$ involving the SBS-gain and all loss parameters. We provide simple expressions for optimal pump power, waveguide length and realisable amplification and demonstrate their utility in two example systems. Notably, we find that 2PA-induced FCA is a serious limitation to SBS in silicon and germanium for wavelengths shorter than 2200nm and 3600nm, respectively. In contrast, three-photon absorption is of no practical significance.
The PAXgene? Tissue System Preserves Phosphoproteins in Human Tissue Specimens and Enables Comprehensive Protein Biomarker Research
Sibylle Gündisch, Christina Schott, Claudia Wolff, Kai Tran, Christian Beese, Christian Viertler, Kurt Zatloukal, Karl-Friedrich Becker
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0060638
Abstract: Precise quantitation of protein biomarkers in clinical tissue specimens is a prerequisite for accurate and effective diagnosis, prognosis, and personalized medicine. Although progress is being made, protein analysis from formalin-fixed and paraffin-embedded tissues is still challenging. In previous reports, we showed that the novel formalin-free tissue preservation technology, the PAXgene Tissue System, allows the extraction of intact and immunoreactive proteins from PAXgene-fixed and paraffin-embedded (PFPE) tissues. In the current study, we focused on the analysis of phosphoproteins and the applicability of two-dimensional gel electrophoresis (2D-PAGE) and enzyme-linked immunosorbent assay (ELISA) to the analysis of a variety of malignant and non-malignant human tissues. Using western blot analysis, we found that phosphoproteins are quantitatively preserved in PFPE tissues, and signal intensities are comparable to that in paired, frozen tissues. Furthermore, proteins extracted from PFPE samples are suitable for 2D-PAGE and can be quantified by ELISA specific for denatured proteins. In summary, the PAXgene Tissue System reliably preserves phosphoproteins in human tissue samples, even after prolonged fixation or stabilization times, and is compatible with methods for protein analysis such as 2D-PAGE and ELISA. We conclude that the PAXgene Tissue System has the potential to serve as a versatile tissue fixative for modern pathology.
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