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Search Results: 1 - 10 of 4705 matches for " Maik Wagner "
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Hybrid Decision Models in Non-Proportional Reinsurance  [PDF]
Maik Wagner
Technology and Investment (TI) , 2010, DOI: 10.4236/ti.2010.11008
Abstract: Over the past years, risk measurement and therewith risk measures became more and more important in economics. While in the past risk measures were already adopted at the deposit of credit and shareholders equity, the approach now generates two hybrid decision models and applies them to the reinsurance business. The two introduced models implement a convex combination of risk measures and with it provide the possibility of modelling risk attitudes. By doing that, for the two hybrid decision models on the one hand can be shown, which risk attitude leads to the acceptance of a reinsurance contract and on the other hand, a deductible of which height an insurer is willing to undertake. Hence the possibility exists to identify the risk attitude of an insurer. In return, due to the knowledge of risk attitudes, under similar conditions the possibility arises to establish recommendations about the extent of the deductible at reinsurance contracts.
virtX: ein Lehr- und Lernsystem für mobile R ntgenger te zur Verbesserung der Ausbildung im Strahlenschutz
Wagner, Markus,Duwenkamp, Christopher,Ahrens, Christoph Alexander,Plischke, Maik
GMS Medizinische Informatik, Biometrie und Epidemiologie , 2009,
Abstract: Hintergrund und Fragestellung: Die durch r ntgentechnische Diagnoseverfahren in der Medizin entstehende Strahlenbelastung für Patient und Personal soll laut Strahlenschutzverordnung so gering wie m glich gehalten werden. Um dieses zu erreichen ist ein professioneller und bedachter Umgang mit den R ntgenger ten unabdingbar. Dieses Verhalten kann derzeit jedoch nur theoretisch vermittelt werden, da sich ein üben mit realer Strahlung von selbst verbietet. Daher stellt sich die Frage wie man die Strahlenschutzausbildung durch eine verbesserte Vermittlung der komplexen Thematik unterstützen kann. Methoden: Das CBT-System (Computer Based Training) virtX, welches das Erlernen der korrekten Handhabung mobiler R ntgenger te unterstützt, wurde um Aspekte aus dem Bereich des Strahlenschutzes erweitert. Es wurde eine prototypische Visualisierung der entstehenden Streustrahlung sowie die Darstellung des Nutzstrahlenganges integriert. Des Weiteren wurde die Berechnung und Anzeige der virtuellen Einfallsdosis für das durchstrahlte Volumen sowie für den Bereich des Bildverst rkers hinzugefügt. Für die Berechnung und Visualisierung all dieser Komponenten werden die in virtX parametrisierbaren C-Bogen-Einstellungen, z.B. Stellung der Blenden, Positionierung des R ntgenger tes zum durchstrahlten Volumen und Strahlenintensit t, herangezogen. Das so erweiterte System wurde auf einem dreit gigen Kurs für OP-Personal mit über 120 Teilnehmern eingesetzt und auf der Basis von Frageb gen evaluiert. Ergebnisse: Von den Teilnehmern gaben 55 einen ausgefüllten Evaluations-Fragebogen ab (Responserate 82%). Das Durchschnittsalter der 39 weiblichen und 15 m nnlichen Teilnehmer (einer o.A.) lag bei 33±8 Jahren, die Berufserfahrung bei 9,37±7 Jahren. Die Erfahrung mit dem C-Bogen wurde von einem Teilnehmer (2%) mit Keine oder bisher nur Einführung erhalten“, von acht Teilnehmern (14%) mit bediene einen C-Bogen gelegentlich“ und von 46 (84%) mit bediene einen C-Bogen regelm ig“ angegeben. 45 (92%) der Teilnehmer gaben an, durch die Visualisierung der Streustrahlung etwas Neues zur Vermeidung unn tiger Strahlenbelastung dazugelernt zu haben. Schlussfolgerung: Trotz einer bislang nur prototypischen Visualisierung der Streustrahlung k nnen mit virtX zentrale Aspekte und Verhaltensweisen zur Vermeidung unn tiger Strahlenbelastung erfolgreich vermittelt werden und so Lücken der traditionellen Strahlenschutzausbildung geschlossen werden.
Electronic and Thermoelectric Properties of RuIn_{3-x}A_{x} (A = Sn, Zn)
Deepa Kasinathan,Maik Wagner,Klaus Koepernik,Raul Cardoso-Gil,Yu. Grin,Helge Rosner
Physics , 2011, DOI: 10.1103/PhysRevB.85.035207
Abstract: Recently, we reported [M. Wagner et al., J. Mater. Res. 26, 1886 (2011)] transport measurements on the semiconducting intermetallic system RuIn3 and its substitution derivatives RuIn_{3-x}A_{x} (A = Sn, Zn). Higher values of the thermoelectric figure of merit (zT = 0.45) compared to the parent compound were achieved by chemical substitution. Here, using density functional theory based calculations, we report on the microscopic picture behind the measured phenomenon. We show in detail that the electronic structure of the substitution variants of the intermetallic system RuIn_{3-x}A_{x} (A = Sn, Zn) changes in a rigid-band like fashion. This behavior makes possible the fine tuning of the substitution concentration to take advantage of the sharp peak-like features in the density of states of the semiconducting parent compound. Trends in the transport properties calculated using the semi-classical Boltzmann transport equations within the constant scattering time approximation are in good agreement with the former experimental results for RuIn_{3-x}Sn_{x}. Based on the calculated thermopower for the p-doped systems, we reinvestigated the Zn-substituted derivative and obtained ZnO-free RuIn_{3-x}Zn_{x}. The new experimental results are consistent with the calculated trend in thermopower and yield large zT value of 0.8.
Phonon-drag effect in FeGa3
Maik Wagner-Reetz,Deepa Kasinathan,Walter Schnelle,Raul Cardoso-Gil,Helge Rosner,Yuri Grin,Peter Gille
Physics , 2014, DOI: 10.1103/PhysRevB.90.195206
Abstract: The thermoelectric properties of single- and polycrystalline FeGa3 are systematically investigated over a wide temperature range. At low temperatures, below 20 K, previously not known pronounced peaks in the thermal conductivity (400-800 W K^-1m-1) with corresponding maxima in the thermopower (in the order of -16000 microV/K) were found in single crystalline samples. Measurements in single crystals along [100] and [001] directions indicate only a slight anisotropy in both the electrical and thermal transport. From susceptibility and heat capacity measurements, a structural or magnetic phase transition was excluded. Using density functional theory-based calculations, we have revisited the electronic structure of FeGa3 and compared the magnetic (including correlations) and non-magnetic electronic density of states. Thermopower at fixed carrier concentrations are calculated using semi-classical Boltzmann transport theory, and the calculated results match fairly with our experimental data and exclude the possibility of strong electronic correlations as an explanation for the low temperature enhancement. Eventually, after a careful review, we assign the peaks in the thermopower as a manifestation of the phonon-drag effect, which is supported by thermopower measurements in a magnetic field.
Particle asymmetries in the early universe
Maik Stuke
Physics , 2010, DOI: 10.1016/j.ppnp.2011.01.010
Abstract: The total lepton asymmetry $l=\sum_f l_f$ in our universe is only poorly constrained by theories and experiments. It might be orders of magnitudes larger than the observed baryon asymmetry $b\simeq {\cal O}(10^{-10})$, $|l|/b \leq {\cal O}(10^{9})$. We found that the dynamics of the cosmic QCD transition changes for large asymmetries. Predictions for asymmetries in a single flavour $l_f$ allow even larger values. We find that asymmetries of $l_f\leq {\cal O}(1)$ in a single or two flavours change the relic abundance of WIMPs. However, large lepton and large individual lepton flavour asymmetries influences significantly the dynamics of the early universe.
The Madelung Picture as a Foundation of Geometric Quantum Theory
Maik Reddiger
Physics , 2015,
Abstract: Despite its age quantum theory remains ill-understood, which is partially to blame on its deep interwovenness with the mysterious concept of quantization. In this article we argue that a quantum theory recoursing to quantization algorithms is necessarily incomplete. To provide a new axiomatic foundation, we give a rigorous proof showing how the Schr\"odinger equation follows from the Madelung equations, which are formulated in the language of Newtonian mechanics. We show how the Schr\"odinger picture relates to this Madelung picture and how the "classical limit" is directly obtained. This suggests a reformulation of the correspondence principle, stating that a quantum theory must reduce to a probabilistic version of Newtonian mechanics for large masses. We then enhance the stochastic interpretation developed by Tsekov, which speculates that quantum mechanical behavior is caused by random vibrations in spacetime. A new, yet incomplete model of particle creation and annihilation is also proposed.
Conditioning of Gaussian processes and a zero area Brownian bridge
Maik Gorgens
Mathematics , 2013,
Abstract: We generalize the notion of Gaussian bridges by conditioning Gaussian processes given that certain linear functionals of the sample paths vanish. We show the equivalence of the laws of the unconditioned and the conditioned process and by an application of Girsanov's theorem, we show that the conditioned process follows a stochastic differential equation (SDE) whenever the unconditioned process does. In the Markovian case, we are able to determine the coefficients in the SDE of the conditioned process explicitly. Our main example is Brownian motion on $[0,1]$ pinned down in 0 at time 1 and conditioned to have vanishing area spanned by the sample paths.
Nanostructuring of Ba8Ga16Ge30 clathrates
Vicente Pachecoa,Raul Cardoso--Gil,Deepa Kasinathan,Helge Rosner,Maik Wagner,Lorenzo Tepech--Carrillo,Wilder Carrillo--Cabrera,Katrin Meier,Yuri Grin
Physics , 2011,
Abstract: First thermoelectric properties measurements on bulk nanostructured Ba8Ga16Ge30 clathrate-I are presented. A sol-gel-calcination route was developed for preparing amorphous nanosized precursor oxides. The further reduction of the oxides led to quantitative yield of crystalline nanosized Ba8Ga16Ge30 clathrate-I. TEM investigations show the clathrate nanoparticles retain the size and morphology of the precursor oxides. The clathrate nanoparticles contain mainly thin plates (approx. 300 nm x 300 nm x 50 nm) and a small amount of nanospheres (diameter ~ 10 nm). SAED patterns confirm the clathrate-I structure type for both morphologies. The powders were compacted via Spark Plasma Sintering (SPS) to obtain a bulk nano-structured material. The Seebeck coefficient S, measured on low-density samples (53% of {\delta}x-ray), reaches -145 {\mu}V/k at 375 {\deg}C. The ZT values are quite low (0.02) due to the high resistivity of the sample (two orders of magnitude larger than bulk materials) and the low sample density. The trend of the temperature dependence of S is in agreement with the values obtained from electronic structure calculations and semi-classical Boltzmann transport theory within the constant scattering approximation. The total thermal conductivity (1.61 W/mK), measured on high density samples (93% of {\delta}x-ray), shows a reduction of 20-25% in relation to the bulk materials (2.1 W/mK). A further shaping of the sample for the Seebeck coefficient and electrical conductivity measurements was not possible due to the presence of cracks. An improvement on the design of the pressing tools, loading of the sample and profile of the applied pressure will enhance the mechanical stability of the samples. These investigations are now in progress.
Role of Ryanodine Receptor Subtypes in Initiation and Formation of Calcium Sparks in Arterial Smooth Muscle: Comparison with Striated Muscle
Kirill Essin,Maik Gollasch
Journal of Biomedicine and Biotechnology , 2009, DOI: 10.1155/2009/135249
Abstract: Calcium sparks represent local, rapid, and transient calcium release events from a cluster of ryanodine receptors (RyRs) in the sarcoplasmic reticulum. In arterial smooth muscle cells (SMCs), calcium sparks activate calcium-dependent potassium channels causing decrease in the global intracellular [Ca2
Diseases of the salivary glands in infants and adolescents
Maik Ellies, Rainer Laskawi
Head & Face Medicine , 2010, DOI: 10.1186/1746-160x-6-1
Abstract: Salivary gland diseases are rare in childhood and adolescence. Their pattern of incidence differs very much from that of adults. Acute and chronic sialadenitis not responding to conservative treatment requires an appropriate surgical approach. The rareness of salivary gland tumors is particularly true for the malignant parotid tumors which are more frequent in juvenile patients, a fact that has to be considered in diagnosis and therapy.Diseases of the salivary glands are rare in infants and children (with the exception of diseases such as parotitis epidemica and cytomegaly) and the therapeutic regimen differs from that in adults. It is therefore all the more important to gain exact and extensive insight into general and special aspects of pathological changes of the salivary glands in these age groups. Previous studies [1-3] have dealt with the clinical distribution pattern of the various pathological entities in infants and older children.According to these studies, important pathologies in these age groups are acute and chronic sialadenitis (with special regard to chronic recurrent parotitis) and secondary inflammation associated with sialolithiasis [2,4-6]. The etiology and pathogenesis of these entities in young patients, however, are still not yet sufficiently understood, so that therapeutic strategies based on extensive clinical experience cannot be defined, particularly in view of the small number of patients in the relevant age groups. The acute forms of sialadenitis are mainly caused by viral or bacterial infections. The predominant cause of parotid swelling in infancy is parotitis epidemica [7]. This disease has its peak incidence between the ages of 2 and 14 [8]. Acute inflammation of the parotid gland, with evidence of Staphylococcus aureus, is often seen in neonates and in children with an underlying systemic disease accompanied by fever, dehydration, immunosuppression and general morbidity [4,9]. Acute inflammation of the submandibular gland, as oppose
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