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Search Results: 1 - 10 of 1964 matches for " Uwe Trautwein "
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Measurement-Based Performance Evaluation of Advanced MIMO Transceiver Designs
Uwe Trautwein,Christian Schneider,Reiner Thom?
EURASIP Journal on Advances in Signal Processing , 2005, DOI: 10.1155/asp.2005.1712
Abstract: This paper describes the methodology and the results of performance investigations on a multiple-input multiple-output (MIMO) transceiver scheme for frequency-selective radio channels. The method relies on offline simulations and employs real-time MIMO channel sounder measurement data to ensure a realistic channel modeling. Thus it can be classified in between the performance evaluation using some predefined channel models and the evaluation of a prototype hardware in field experiments. New aspects for the simulation setup are discussed, which are frequently ignored when using simpler model-based evaluations. Example simulations are provided for an iterative ( ¢ € turbo ¢ € ) MIMO equalizer concept. The dependency of the achievable bit error rate performance on the propagation characteristics and on the variation in some system design parameters is shown, whereas the antenna constellation is of particular concern for MIMO systems. Although in many of the considered constellations turbo MIMO equalization appears feasible in real field scenarios, there exist cases with poor performance as well, indicating that in practical applications link adaptation of the transmitter and receiver processing to the environment is necessary.
A survey of the GIT picture for the Yang-Mills equation over Riemann surfaces
Samuel Trautwein
Mathematics , 2015,
Abstract: The purpose of this paper is to give a self-contained exposition of the Atiyah-Bott picture for the Yang-Mills equation over Riemann surfaces with an emphasis on the analogy to finite dimensional geometric invariant theory. The main motivation is to provide a careful study of the semistable and unstable orbits: This includes the analogue of the Ness uniqueness theorem for Yang-Mills connections, the Kempf-Ness theorem, the Hilbert-Mumford criterion and a new proof of the moment-weight inequality following an approach outlined by Donaldson. A central ingredient in our discussion is the Yang-Mills flow for which we assume longtime existence and convergence.
Assessing Complexity Results in Feature Theories
Marten Trautwein
Computer Science , 1995,
Abstract: In this paper, we assess the complexity results of formalisms that describe the feature theories used in computational linguistics. We show that from these complexity results no immediate conclusions can be drawn about the complexity of the recognition problem of unification grammars using these feature theories. On the one hand, the complexity of feature theories does not provide an upper bound for the complexity of such unification grammars. On the other hand, the complexity of feature theories need not provide a lower bound. Therefore, we argue for formalisms that describe actual unification grammars instead of feature theories. Thus the complexity results of these formalisms judge upon the hardness of unification grammars in computational linguistics.
A Note on the Complexity of Restricted Attribute-Value Grammars
Leen Torenvliet,Marten Trautwein
Computer Science , 1995,
Abstract: The recognition problem for attribute-value grammars (AVGs) was shown to be undecidable by Johnson in 1988. Therefore, the general form of AVGs is of no practical use. In this paper we study a very restricted form of AVG, for which the recognition problem is decidable (though still NP-complete), the R-AVG. We show that the R-AVG formalism captures all of the context free languages and more, and introduce a variation on the so-called `off-line parsability constraint', the `honest parsability constraint', which lets different types of R-AVG coincide precisely with well-known time complexity classes.
Density Functional Theory Calculations for Spin Crossover Complexes
Hauke Paulsen,Alfred Xaver Trautwein
Physics , 2012, DOI: 10.1007/b95428
Abstract: Density functional theory (DFT) provides a theoretical framework for efficient and fairly accurate calculations of the electronic structure of molecules and crystals. The main features of density functional theory are described and DFT methods are compared with wavefunction-based methods like the Hartree-Fock approach. Some recent applications of DFT to spin crossover complexes are reviewed, e.g., the calculation of M\"ossbauer parameters, of vibrational modes and of differences of entropy, vibrational energy, and total electronic energy between high-spin and low-spin isomers.
Towards Quantitative Characterisation of the Small Force Transducer Used in Nanoindentation Instruments  [PDF]
Zhi Li, Uwe Brand
Modern Instrumentation (MI) , 2013, DOI: 10.4236/mi.2013.24009

Quantitative characterization of the mechanical properties of materials in micro-/nano-scale using depth-sensing indentation technique demands high performance of nanoindentation instruments in use. In this paper, the efforts to calibrate the capacitive force transducer of a commercial nanoindentation instrument are presented, where the quasi-static characteristic of the force transducer has been calibrated by a precise compensation balance with a resolution of ~1 nN. To investigate the dynamic response of the transducer, an electrostatic MEMS (Micro-Electro-Mechanical System) based on nano-force transfer standard with nano-Newton (10-9 Newton) resolution and a bandwidth up to 6 kHz have been employed. Preliminary experimental results indicate that 1) the force transducer under calibration has a probing force uncertainty less than 300 nN (1σ) in the calibration range of 1 mN; 2) the transient duration at contact points amounts to 10 seconds; 3) the overshoot of engagement is pre-load dependent.

Affiliation of Dihydrolipoyl Dehydrogenase Allozymes in Mycorrhizae of European Forest Trees and Characterization of the Enzyme of the Matt Bolete (Xerocomus pruinatus) and the Bay Bolete (X. badius)  [PDF]
Uwe Schirkonyer, Gunter M. Rothe
Open Journal of Ecology (OJE) , 2018, DOI: 10.4236/oje.2018.86022
Abstract: Mycorrhizal roots of the deciduous trees European beech (Fagus sylvatica (L.)) and Sessile oak (Quercus petraea (MattuschkaLiebl.)) and the conifers Norway spruce (Picea abies (L.) H. Karst.) and European larch (Larix decidua (Mill.)) associated with the ectomycorrhizal fungi matt bolete (Xerocomus pruinatus (Fries 1835)) or bay bolete (X. badius (Fries 1818)) were analysed with respect to the occurrence of dihydrolipoyl dehydrogenase (EC allozymes. In root tissues of the two deciduous trees, two gene loci could be visualized after cellulose acetate electrophoresis while three loci were expressed in root tissues of the two coniferous species. The two fungal species and further ectomycorrhizal fungi expressed exclusively one dihydrolipoyl dehydrogenase gene. In Xerocomus pruinatus and X. badius, the dihydrolipoyl dehydrogenase gene consists of 1460 bp and 1370 bp, respectively, including five introns each consisting of 52 bp. Their DNA sequences correspond to 70 to 90% to other fungal dihydrolipoyl dehydrogenase genes. One monomer of the dimeric dihydrolipoyl dehydrogenase enzyme consists of 486 (X. pruinatus) or 454 (X.
Drosophila muscleblind Codes for Proteins with One and Two Tandem Zinc Finger Motifs
Uwe Irion
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0034248
Abstract: Muscleblind-like proteins, Muscleblind (Mbl) in Drosophila and MBNL1-3 in vertebrates, are regulators of alternative splicing. Human MBNL1 is a key factor in the etiology of myotonic dystrophy (DM), a muscle wasting disease caused by the occurrence of toxic RNA molecules containing CUG/CCUG repeats. MBNL1 binds to these RNAs and is sequestered in nuclear foci preventing it from exerting its normal function, which ultimately leads to mis-spliced mRNAs, a major cause of the disease. Muscleblind-proteins bind to RNAs via N-terminal zinc fingers of the Cys3-His type. These zinc fingers are arranged in one (invertebrates) or two (vertebrates) tandem zinc finger (TZF) motifs with both fingers targeting GC steps in the RNA molecule. Here I show that mbl genes in Drosophila and in other insects also encode proteins with two TZF motifs, highly similar to vertebrate MBNL proteins. In Drosophila the different protein isoforms have overlapping but possibly divergent functions in vivo, evident by their unequal capacities to rescue the splicing defects observed in mbl mutant embryos. In addition, using whole transcriptome analysis, I identified several new splicing targets for Mbl in Drosophila embryos. Two of these novel targets, kkv (krotzkopf-verkehrt, coding for Chitin Synthase 1) and cora (coracle, coding for the Drosophila homolog of Protein 4.1), are not muscle-specific but expressed mainly in epidermal cells, indicating a function for mbl not only in muscles and the nervous system.
Modeling the Risk of Secondary Malignancies after Radiotherapy
Uwe Schneider
Genes , 2011, DOI: 10.3390/genes2041033
Abstract: In developed countries, more than half of all cancer patients receive radiotherapy at some stage in the management of their disease. However, a radiation-induced secondary malignancy can be the price of success if the primary cancer is cured or at least controlled. Therefore, there is increasing concern regarding radiation-related second cancer risks in long-term radiotherapy survivors and a corresponding need to be able to predict cancer risks at high radiation doses. Of particular interest are second cancer risk estimates for new radiation treatment modalities such as intensity modulated radiotherapy, intensity modulated arc-therapy, proton and heavy ion radiotherapy. The long term risks from such modern radiotherapy treatment techniques have not yet been determined and are unlikely to become apparent for many years, due to the long latency time for solid tumor induction. Most information on the dose-response of radiation-induced cancer is derived from data on the A-bomb survivors who were exposed to γ-rays and neutrons. Since, for radiation protection purposes, the dose span of main interest is between zero and one Gy, the analysis of the A-bomb survivors is usually focused on this range. With increasing cure rates, estimates of cancer risk for doses larger than one Gy are becoming more important for radiotherapy patients. Therefore in this review, emphasis was placed on doses relevant for radiotherapy with respect to radiation induced solid cancer. Simple radiation protection models should be used only with extreme care for risk estimates in radiotherapy, since they are developed exclusively for low dose. When applied to scatter radiation, such models can predict only a fraction of observed second malignancies. Better semi-empirical models include the effect of dose fractionation and represent the dose-response relationships more accurately. The involved uncertainties are still huge for most of the organs and tissues. A major reason for this is that the underlying processes of the induction of carcinoma and sarcoma are not well known. Most uncertainties are related to the time patterns of cancer induction, the population specific dependencies and to the organ specific cancer induction rates. For radiotherapy treatment plan optimization these factors are irrelevant, as a treatment plan comparison is performed for a patient of specific age, sex, etc. If a treatment plan is compared relative to another one only the shape of the dose-response curve (the so called risk-equivalent dose) is of importance and errors can be minimized.
Pathophysiology of fluid imbalance
Uwe Kreimeier
Critical Care , 2000, DOI: 10.1186/cc968
Abstract: A discussion of the pathophysiology of fluid imbalance typically focuses on hypovolemia. A relevant clinical scenario is described in the following case report.A laboratory worker was taken to the emergency department with malaise, headache, nausea and vomiting [1]. There was evidence of circulatory failure and infection. The patient's pulse was 114 beats/min, blood pressure 42/20 mmHg and oral temperature 40°C. The pre-load filling pressure was very low, while cardiac index was elevated. Clinical symptoms were consistent with a generalized capillary leak syndrome. The patient received 14.9 l fluid in excess of measured output during the period of hypotension. Inotropic support with dopamine and nor-epinephrine was also provided. The presumptive diagnosis was septic shock.It was discovered 11 h after admission that the patient had self-administered 1 mg Salmonella minnesota endotoxin 2.5 h prior to arrival at the emergency department in an attempt to treat a recently diagnosed tumor. This single, large intravenous dose of endotoxin had provoked the manifestations of septic shock syndrome, including hypotension with high cardiac output, disseminated intravascular coagulation, abnormalities of hepatic and renal function, and pulmonary edema. A dose of 100 mg human monoclonal antibody against the lipid A moiety of bacterial lipopolysaccharide (HA-1A) antibody was administered 23 h after the injection of endotoxin. Norepinephrine infusion was discontinued 50 h after the endotoxin injection. The patient was discharged on the eighth hospital day.Although the precipitating cause of this patient's condition was unusual, hypovolemia necessitating fluid administration is a common occurrence. Nevertheless, a proper consideration of fluid imbalance extends beyond hypovolemia alone. Fluid imbalance indeed encompasses a triad of conditions consisting of hypovolemia, normovolemia with maldistribution of fluid, and hypervolemia. Each of these is now discussed.One frequent cause of
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