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  • 1
    Language: English
    In: Advances in Water Resources, April 2017, Vol.102, pp.161-177
    Description: In the geostatistical inverse problem of subsurface hydrology, continuous hydraulic parameter fields, in most cases hydraulic conductivity, are estimated from measurements of dependent variables, such as hydraulic heads, under the assumption that the parameter fields are autocorrelated random space functions. Upon discretization, the continuous fields become large parameter vectors with elements. While cokriging-like inversion methods have been shown to be efficient for highly resolved parameter fields when the number of measurements is small, they require the calculation of the sensitivity of each measurement with respect to all parameters, which may become prohibitive with large sets of measured data such as those arising from transient groundwater flow. We present a Preconditioned Conjugate Gradient method for the geostatistical inverse problem, in which a single adjoint equation needs to be solved to obtain the gradient of the objective function. Using the autocovariance matrix of the parameters as preconditioning matrix, expensive multiplications with its inverse can be avoided, and the number of iterations is significantly reduced. We use a randomized spectral decomposition of the posterior covariance matrix of the parameters to perform a linearized uncertainty quantification of the parameter estimate. The feasibility of the method is tested by virtual examples of head observations in steady-state and transient groundwater flow. These synthetic tests demonstrate that transient data can reduce both parameter uncertainty and time spent conducting experiments, while the presented methods are able to handle the resulting large number of measurements.
    Keywords: Inverse Modeling ; Geostatistical Inversion ; Uncertainty Quantification ; Nonlinear Conjugate Gradients ; Preconditioning ; Engineering
    ISSN: 0309-1708
    E-ISSN: 1872-9657
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  • 2
    Language: English
    In: Hydrology and Earth System Sciences, Sept 21, 2018, Vol.22(9), p.4921
    Description: pThe ensemble Kalman filter (EnKF) is a popular data assimilation method in soil hydrology. In this context, it is used to estimate states and parameters simultaneously. Due to unrepresented model errors and a limited ensemble size, state and parameter uncertainties can become too small during assimilation. Inflation methods are capable of increasing state uncertainties, but typically struggle with soil hydrologic applications. We propose a multiplicative inflation method specifically designed for the needs in soil hydrology. It employs a Kalman filter within the EnKF to estimate inflation factors based on the difference between measurements and mean forecast state within the EnKF. We demonstrate its capabilities on a small soil hydrologic test case. The method is capable of adjusting inflation factors to spatiotemporally varying model errors. It successfully transfers the inflation to parameters in the augmented state, which leads to an improved estimation.
    Keywords: Hydrology – Methods ; Hydrology – Analysis ; Inflation (Economics) – Methods ; Inflation (Economics) – Analysis
    ISSN: 1027-5606
    E-ISSN: 16077938
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  • 3
    Language: English
    In: Hydrology and Earth System Sciences Discussions, 03/05/2018, pp.1-18
    Description: The ensemble Kalman filter (EnKF) is a popular data assimilation method in soil hydrology. In this context, it is used to estimate states and parameters simultaneously. Due to unrepresented model errors and a limited ensemble size, state and parameter uncertainties can become too small during assimilation. Inflation methods are capable of increasing state uncertainties, but typically struggle with soil hydrologic applications. We propose a multiplicative inflation method specifically designed for the needs in soil hydrology. It employs a Kalman filter within the EnKF to estimate inflation factors based on the difference between measurements and mean forecast state within the EnKF. We demonstrate its capabilities on a small soil hydrologic test case. The method is capable of adjusting inflation factors to spatiotemporally varying model errors. It successfully transfers the inflation to parameters in the augmented state, which leads to an improved estimation.
    Keywords: Geography;
    ISSN: Hydrology and Earth System Sciences Discussions
    E-ISSN: 1812-2116
    Source: CrossRef
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  • 4
    In: BioMed Research International, 2018, Vol.2018, 10 pages
    Description: High temperatures during drilling can cause thermal osteonecrosis and abnormal wound healing. According to our best knowledge, a widely accepted recommendation for optimal drilling parameters in routine oral surgery bone removals does not exist. Our aim was to investigate the correlations of different drilling parameters, including axial load and revolution speed on drilling temperatures and preparation times. Standard, 5 mm deep cavities were drilled in 20 PCF (lb/ft) dens polyurethane blocks with 3 mm (50PCF) cortical layer using new and worn, 3.1mm in diameter tungsten carbide round drills. Worn drills were used in 50 impacted third molar operations before. Axial loads of 3N, 10N, and 25N and speeds of 4.000-8.000-16.000-40.000 revolutions per minute (rpm) were tested. Temperature differences of drilling parameters were calculated by 1-way ANOVA, followed by Tukey’s HSD post hoc tests. Time differences and differences among “optimal” and “suboptimal” groups (with the cut-off value of 3°C and 3s) were estimated by Kruskal-Wallis test with pairwise comparisons. P〈0.05 was considered significant.. The highest mean temperatures with new and worn drills were 4.64±0.53°C and 6.89±1.16°C, while drilling times varied between 0.16±0.02s and 22.77±5.45s. A 3°C and 3s cut-off value classified drillings significantly to (1) optimal [] or suboptimal due to (2) high temperatures or (3) long preparation times. Using worn drills, the following parameters should be avoided: 3N with 4.000-8.000 rpm, 10N with 40000 rpm, and 25N at any revolutions.. The study extensively mapped the drilling temperatures and preparation times of tungsten carbide round drills. Temperatures did not exceed 10°C during drillings with maximal amount of cooling, as well as the drilling parameters, which kept temperatures and preparation times in the most optimal range which were clearly established.
    Keywords: Research Article
    ISSN: 2314-6133
    E-ISSN: 2314-6141
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  • 5
    Language: English
    In: 2016 IEEE 83rd Vehicular Technology Conference (VTC Spring), May 2016, pp.1-5
    Description: Regarding capacity as well as commercial aspects deploying small cells is a proper way to cover user hotspots. In particular when macro and pico eNodeBs are running on the same frequency the pico site should be located near to the hotspot centre. However, practical user localisation methods have a mean error in the range of 50m. In order to investigate if hotspot detection is possible although the quite large localisation error we simulate erroneous user locations in realistic hotspot scenarios. According to our simulations the hotspots is visually to find on user density maps and a numerical hotspot detection is possible for hotspot user density exceeding 4 times that one outside the hotspot. The deviation between the real and the detected hotspot centre point is well below 20m.
    Keywords: Land Mobile Radio ; Global Positioning System ; Nakagami Distribution ; Shape ; Solids ; Urban Areas ; Layout
    ISSN: 15502252
    Source: IEEE Conference Publications
    Source: IEEE Xplore
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  • 6
    Language: English
    In: Science (New York, N.Y.), 21 March 2003, Vol.299(5614), pp.1889-92
    Description: Local circuits in the spinal cord that generate locomotion are termed central pattern generators (CPGs). These provide coordinated bilateral control over the normal limb alternation that underlies walking. The molecules that organize the mammalian CPG are unknown. Isolated spinal cords from mice lacking either the EphA4 receptor or its ligand ephrinB3 have lost left-right limb alternation and instead exhibit synchrony. We identified EphA4-positive neurons as an excitatory component of the locomotor CPG. Our study shows that dramatic locomotor changes can occur as a consequence of local genetic rewiring and identifies genes required for the development of normal locomotor behavior.
    Keywords: Membrane Transport Proteins ; Vesicular Transport Proteins ; Walking ; Ephrin-B3 -- Physiology ; Neurons -- Physiology ; Receptor, Epha4 -- Physiology ; Spinal Cord -- Physiology
    ISSN: 00368075
    E-ISSN: 1095-9203
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  • 7
    Language: English
    In: Wireless Personal Communications, 2008, Vol.46(1), pp.67-82
    Description: We propose and evaluate the Frame Descriptor Table (FDT) concept, a method to increase efficiency of signalling resource allocation in frame based Medium Access Control (MAC) protocols. MAC protocols for Beyond 3G mobile radio networks, also known as IMT-Advanced systems, will operate on high data rate channels resulting in short packet transmission duration. The scheduling overhead per packet must also be reduced, correspondingly. The new concept is suitable also to reduce the MAC control overhead spent per hop in mobile radio systems with Relay Enhanced Cells (REC)s that apply multi-hop communication by dynamically allocating TDMA channels. This paper’s focus is on performance evaluation of multi-hop scenarios using analytical models and event-driven stochastic simulations. It is shown that FDT based MAC protocols are suited to increase throughput and reduce delay in REC based cellular radio systems.
    Keywords: Relay enhanced cell ; Multi-hop ; MAC protocol ; Analysis ; Simulation ; Frame descriptor table ; WINNER ; Quality of service ; Beyond 3G ; IMT-advanced ; IEEE 802.11e ; IEEE 802.16a ; HiperLAN/2
    ISSN: 0929-6212
    E-ISSN: 1572-834X
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  • 8
    Language: English
    In: Proceedings of the 2006 international conference on wireless communications and mobile computing, 03 July 2006, pp.647-652
    Description: The employment of the OFDMA transmission technique in broadband radio systems shows several benefits. Especially the exploitation of multi-user diversity with the help of sophisticated scheduling algorithms can significantly increase the system capacity. In this paper, the performance of joint scheduling of downlink data transmissions for access point sets is evaluated in a multi-cellular system. The latter is compared with an independent scheduling on orthogonal subchannel sets in the access points. The general MAC structure of the investigated system is thereby based on IEEE 802.16a. However, concerning the Physical Layer there is an important difference. In IEEE 802.16a, the exploitation of multi-user diversity is not possible since the OFDMA subchannel scheme is based on an interference and fading averaging approach. The technique examined in this paper in contrast can be regarded as an avoidance approach which is subject to diversity in the subchannel quality. A basic OFDMA scheduling algorithm, which is able to exploit multi-user diversity and provide fairness, is used both for the joint and for the independent scheme.
    Keywords: Ieee 802.16a ; Ofdma ; Qos ; Access Point Controller ; Joint Downlink Scheduling ; Multi User Diversity ; Resource Partitioning ; Engineering
    ISBN: 1595933069
    ISBN: 9781595933065
    Source: ACM Digital Library (Association for Computing Machinery)
    Source: KESLI (ACM Digital Library)
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  • 9
    In: Nature Medicine, 1999, Vol.5(3), p.347
    Description: Mitochondria are particularly vulnerable to oxidative stress, and mitochondrial swelling and vacuolization are among the earliest pathologic features found in two strains of transgenic amyotrophic lateral sclerosis (ALS) mice with SOD1 mutations. Mice with the G93A human SOD1 mutation have altered electron transport enzymes, and expression of the mutant enzyme in vitro results in a loss of mitochondrial membrane potential and elevated cytosolic calcium concentration. Mitochondrial dysfunction may lead to ATP depletion, which may contribute to cell death. If this is true, then buffering intracellular energy levels could exert neuroprotective effects. Creatine kinase and its substrates creatine and phosphocreatine constitute an intricate cellular energy buffering and transport system connecting sites of energy production (mitochondria) with sites of energy consumption, and creatine administration stabilizes the mitochondrial creatine kinase and inhibits opening of the mitochondrial transition pore. We found that oral administration of creatine produced a dose-dependent improvement in motor performance and extended survival in G93A transgenic mice, and it protected mice from loss of both motor neurons and substantia nigra neurons at 120 days of age. Creatine administration protected G93A transgenic mice from increases in biochemical indices of oxidative damage. Therefore, creatine administration may be a new therapeutic strategy for ALS.
    Keywords: Medicine ; Biology;
    ISSN: 1078-8956
    E-ISSN: 1546-170X
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  • 10
    Language: English
    In: Movement Disorders, April 2012, Vol.27(4), pp.590-591
    Description: To purchase or authenticate to the full-text of this article, please visit this link: http://onlinelibrary.wiley.com/doi/10.1002/mds.24907/abstract Byline: Julia Richter, Silke Appenzeller, Ole Ammerpohl, G. Deuschl, Steffen Paschen, Norbert Bruggemann, Christine Klein, Gregor Kuhlenbaumer ***** No abstract is available for this article. ***** Author Affiliation: Institute of Human Genetics, Christian-Albrechts-University, Kiel, Germany Institute of Experimental Medicine, Molecular Neurobiology Christian-Albrechts-University, Kiel, Germany Department of Neurology, Christian-Albrechts-University, Kiel, Germany Section of Clinical and Molecular Neurogenetics at the Department of Neurology University of Lubeck, Lubeck, Germany Institute of Human Genetics, Christian-Albrechts-University, Kiel, Germany Institute of Experimental Medicine, Molecular Neurobiology Christian-Albrechts-University, Kiel, Germany Department of Neurology, Christian-Albrechts-University, Kiel, Germany Section of Clinical and Molecular Neurogenetics at the Department of Neurology University of Lubeck, Lubeck, Germany Article Note: (*) Funding agencies: This study was supported by funds from the "Fakultatsubergreifende Forschungsforderung des Medizin-Ausschusses beider Medizinischer Fakultaten in Kiel und Lubeck." ([dagger]) Relevant conflicts of interest/financial disclosures: G. Deuschl, Gregor Kuhlenbaumer, and Silke Appenzeller are members of the cluster of excellence "Inflammation at Interfaces." ([double dagger]) Full financial disclosures and author roles may be found in the online version of this article.
    Keywords: Methylation – Analysis ; DNA – Analysis ; Neurophysiology – Analysis;
    ISSN: 0885-3185
    E-ISSN: 1531-8257
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