Underground measurements and simulations on the muon intensity and 12C-induced nuclear reactions at low energies

The reaction 12C(α,γ)16O is of paramount importance for the nucleosynthesis of heavier elements in stars. It takes place during helium burning and determines the abundance of 12C and 16O at the end of this burning stage and therefore influences subsequent nuclear reactions. Currently the cross section at astrophysically relevant energies is not known with satisfactory precision. Due to the low cross section of the reaction, low background, high beam intensities and target thicknesses are necessary for experiments. Therefore a new laboratory hosting a 5 MV ion accelerator, was built in the shallow-underground tunnels of Felsenkeller. The main background component in such laboratories was investigated with a muon telescope in this thesis. It was found, that the rock overburden of about 45 m vertical depth reduces the muons by a factor of about 40 compared to the surface. Furthermore the results of the measurements were compared to a simulation based on the geometry of the facility and showed good agreement. In the next step the accelerator was put into operation. Since the experiment on 12C(α,γ)16O will be done in inverse kinematics, an intense carbon beam is necessary to reach sufficient statistics. For this, the creation and extraction of carbon ions in an external ion source was improved. The external source now provides steady currents of 12C− of above 100 μA. In the following the transmission through the accelerator and the high-energy beamline was tested with a beam restricted in width. The pressure of the gas stripper in the centre of the accelerator and the parameters of different focusing elements after the accelerator were varied. It was found, that for a desired carbon beam energy of below 9 MeV, the 2+ charge state is suited best, where up to 35% of the inserted beam could be transmitted. To ease the planning of future experiments and aid the analysis of the data, the target chamber and two different kinds of cluster detectors were modelled in Geant4. The low-energy region was verified by comparing the simulations to measurements with radioactive calibration sources. Deviations for the detectors were below 10% without target chamber, and up to 30% for individual germanium crystals of the Cluster Detectors with the target chamber. A first test measurement was undertaken to investigate the capabilities of the new laboratory. Solid tantalum targets implanted with 4 He were prepared. An ERDA analysis of the used solid targets showed contaminations with carbon and oxygen. These led to beam-induced background in the region of interest during the irradiation. Then the targets were irradiated with a carbon beam at two different energies. While no clear signal of 12C(α,γ)16O could be observed, the beam could be steered on the target for the whole duration of the beam time spanning five days. Problems during this test, like low beam current, were identified. These could be partly remedied in the scope of this thesis. Suggestions for improvements for a second test run were developed as well

Underground measurements and simulations on the muon intensity and 12C-induced nuclear reactions at low energies

The reaction 12C(α,γ)16O is of paramount importance for the nucleosynthesis of heavier elements in stars. It takes place during helium burning and determines the abundance of 12C and 16O at the end of this burning stage and therefore influences subsequent nuclear reactions. Currently the cross section at astrophysically relevant energies is not known with satisfactory precision. Due to the low cross section of the reaction, low background, high beam intensities and target thicknesses are necessary for experiments. Therefore a new laboratory hosting a 5 MV ion accelerator, was built in the shallow-underground tunnels of Felsenkeller. The main background component in such laboratories was investigated with a muon telescope in this thesis. It was found, that the rock overburden of about 45 m vertical depth reduces the muons by a factor of about 40 compared to the surface. Furthermore the results of the measurements were compared to a simulation based on the geometry of the facility and showed good agreement. In the next step the accelerator was put into operation. Since the experiment on 12C(α,γ)16O will be done in inverse kinematics, an intense carbon beam is necessary to reach sufficient statistics. For this, the creation and extraction of carbon ions in an external ion source was improved. The external source now provides steady currents of 12C− of above 100 μA. In the following the transmission through the accelerator and the high-energy beamline was tested with a beam restricted in width. The pressure of the gas stripper in the centre of the accelerator and the parameters of different focusing elements after the accelerator were varied. It was found, that for a desired carbon beam energy of below 9 MeV, the 2+ charge state is suited best, where up to 35% of the inserted beam could be transmitted. To ease the planning of future experiments and aid the analysis of the data, the target chamber and two different kinds of cluster detectors were modelled in Geant4. The low-energy region was verified by comparing the simulations to measurements with radioactive calibration sources. Deviations for the detectors were below 10% without target chamber, and up to 30% for individual germanium crystals of the Cluster Detectors with the target chamber. A first test measurement was undertaken to investigate the capabilities of the new laboratory. Solid tantalum targets implanted with 4 He were prepared. An ERDA analysis of the used solid targets showed contaminations with carbon and oxygen. These led to beam-induced background in the region of interest during the irradiation. Then the targets were irradiated with a carbon beam at two different energies. While no clear signal of 12C(α,γ)16O could be observed, the beam could be steered on the target for the whole duration of the beam time spanning five days. Problems during this test, like low beam current, were identified. These could be partly remedied in the scope of this thesis. Suggestions for improvements for a second test run were developed as well

Response-Modality-Specific Encoding of Human Choices in Upper Beta Band Oscillations during Vibrotactile Comparisons

Perceptual decisions based on the comparison of two vibrotactile frequencies have been extensively studied in non-human primates. Recently, we obtained corresponding findings from human oscillatory electroencephalography (EEG) activity in the form of choice-selective modulations of upper beta band amplitude in medial premotor areas. However, the research in non-human primates as well as its human counterpart was so far limited to decisions reported by button presses. Thus, here we investigated whether the observed human beta band modulation is specific to the response modality. We recorded EEG activity from participants who compared two sequentially presented vibrotactile frequencies (f1 and f2), and decided whether f2 > f1 or f2 < f1, by performing a horizontal saccade to either side of a computer screen. Contrasting time-frequency transformed EEG data between both choices revealed that upper beta band amplitude (∼24–32 Hz) was modulated by participants’ choices before actual responses were given. In particular, “f2 > f1” choices were always associated with higher beta band amplitude than “f2 < f1” choices, irrespective of whether the choice was correct or not, and independent of the specific association between saccade direction and choice. The observed pattern of beta band modulation was virtually identical to our previous results when participants responded with button presses. In line with an intentional framework of decision making, the most likely sources of the beta band modulation were now, however, located in lateral as compared to medial premotor areas including the frontal eye fields. Hence, we could show that the choice-selective modulation of upper beta band amplitude is on the one hand consistent across different response modalities (i.e., same modulation pattern in similar frequency band), and on the other hand effector specific (i.e., modulation originating from areas involved in planning and executing saccades)

Additive mixed models with Dirichlet process mixture and P-spline priors

Longitudinal data often require a combination of flexible trends and individual-specific random effects. In this paper, we propose a fully Bayesian approach based on Markov chain Monte Carlo simulation techniques that allows for the semiparametric specification of both the trend function and the random effects distribution. Bayesian penalized splines are considered for the former, while a Dirichlet process mixture (DPM) specification allows for an adaptive amount of deviations from normality for the latter. We investigate the advantages of DPM prior structures for random effects in terms of a simulation study and present a challenging application that requires semiparametric mixed modeling

Production-oriented design of electric traction drives with hairpin winding

In recent years, the manufacturing of stators by hairpin technology has proven its ability to fulfill the requirements on quality, productivity and robustness of traction drive applications in automotive industry. However, the uncertainty and necessity of rapid product development despite fuzzy target systems still cause that processes, machines and equipment – as well as the electric design – are often in an imperfect prototype stage at the start of production ramp-up. Due to the complex interdependencies between the stator components in combination with a high sensitivity of the overall process reliability to minor adjustments of stator design features, possible production-related weaknesses in design are often recognized first in the prototype stage of the production system. In order to reduce the economic risk resulting from these volatile technological conditions, production-oriented design based on numerical simulation methods can be applied from the beginning of product development. Therefore, several techniques for numerical process modeling are presented in this paper as possibilities to consider manufacturing constraints in an early stage of product development. For this purpose, the influence of wire dimensions on the forming process of hairpin coils is investigated using the example of rotary bending as well as the twisting process of a full stator by finite element simulations. Furthermore, a numerical approach to investigate the influence of heat input during laser welding of hairpin coils on the required stripping length is introduced

Zum Konzept der künftigen Finanzaufsicht über Lebensversicherungsunternehmen in Deutschland - eine betriebswirtschaftliche Analyse von Solvency II unter besonderer Berücksichtigung von Bewertungsfragen

Die Arbeit untersucht die derzeit auf europäischer Ebene im Rahmen des Solvency II-Projektes reformierte Finanzaufsicht über Versicherungsunternehmen aus betriebswirtschaftlicher Perspektive, wobei von der Anwendung von Solvency II auf deutsche Lebensversicherungsunternehmen ausgegangen wird. Methodisch werden für die Analyse Anforderungen an zielkonforme Finanzaufsicht abgeleitet und die künftige Finanzaufsicht vor dem Hintergrund relevanter betriebswirtschaftlicher Erkenntnisse beurteilt

Was sind die Charakteristika von Patienten, die nach einer Erstbehandlung aus einer interdisziplinären Notaufnahme entlassen wurden und sich innerhalb von 7 Tagen ungeplant wieder vorstellten: eine retrospektive Studie an 240 Patienten

Ein wiederkehrendes Problem in klinischen Notaufnahmen sind Patienten, die sich nach erfolgter Behandlung ungeplant wieder vorstellen. Diese Patienten wurden in der Literatur auch als „bounce back“ Patienten bezeichnet. Autoren von bisher veröffentlichten Studien zu vergleichbaren Patientenkollektiven stellten dafür vielfältige Ursachen fest. Obwohl prozentual nicht führend legten verschiedene Publikationen aus klinischem Interesse einen besonderen Schwerpunkt auf Fehldiagnosen als mögliche Ursachen für eine ungeplante Wiedervorstellung. Unsere Studienziele waren die verschiedenen Ursachen einer ungeplanten Patientenwiedervorstellung in der Notaufnahme der Universitätsklinik Jena herauszuarbeiten, der Vergleich unserer berechneten „bounce back“ Rate mit den Raten anderer Studien, die Erfassung potenzieller Fehldiagnosen, die Untersuchung der Studienpopulation auf eventuelle pathologische Vital- und Blutparameter und die Diskussion über eine mögliche Verminderung der verschiedenen Wiedervorstellungsursachen

Isolated Multiport Converter as Cost Efficient Solution for DC-Fast Charger of Electric Vehicle

The ongoing electrification of the transport sector raises demands for new power electronic solutions. As a consequence, modular converter structures are state of the art for fast charging, since high power and short charging times are required. This work presents a modular multiport DC-DC converter which has the capability to decrease the cost and size of the required charging station. Furthermore, design guidelines for the investigated topology are presented. The analysis is validated with a three port isolated DC-DC converter with separated loads

Multiwinding based Semi-Dual Active Bridge Converter

Modular converter structures are state of the art for fast charging, since high power and short charging times are required. Multiwinding converter structures can bring several positive advantages, like cost and space reduction. However, the increased complexity due to the magnetically coupled ports needs to be handled. This paper introduces a multiwinding based Semidual-Active-Bridge converter with separated output voltages. The related design challenges in terms of independent charging voltage regulation are evaluated and design guidelines for the medium frequency transformer are presented. The theoretical analysis is validated experimentally

How to Clear Polytrauma Patients for Fracture Fixation: Results of a systematic review of the literature

Introduction Early patient assessment is relevant for surgical decision making in severely injured patients and early definitive surgery is known to be beneficial in stable patients. The aim of this systematic review is to extract parameters indicative of risk factors for adverse outcome. Moreover, we aim to improve decision making and separate patients who would benefit from early versus staged definitive surgical fixation. Methods Following the PRISMA guidelines, a systematic review of peer-reviewed articles in English or German language published between (2000 and 2022) was performed. The primary outcome was the pathophysiological response to polytrauma including coagulopathy, shock/haemorrhage, hypothermia and soft tissue injury (trauma, brain injury, thoracic and abdominal trauma, and musculoskeletal injury) to determine the treatment strategy associated with the least amount of complications. Articles that had used quantitative parameters to distinguish between stable and unstable patients were summarized. Two authors screened articles and discrepancies were resolved by consensus. Quantitative values for relevant parameters indicative of an unstable polytrauma patient were obtained. Results The initial systematic search using MeSH criteria yielded 1550 publications deemed relevant to the following topics (coagulopathy (n = 37), haemorrhage/shock (n = 7), hypothermia (n = 11), soft tissue injury (n = 24)). Thresholds for stable, borderline, unstable and in extremis conditions were defined according to the existing literature as follows: Coagulopathy; International Normalized Ratio (INR) and viscoelastic methods (VEM)/Blood/shock; lactate, systolic blood pressure and haemoglobin, hypothermia; thresholds in degrees Celsius/Soft tissue trauma: traumatic brain injury, thoracic and abdominal trauma and musculoskeletal trauma. Conclusion In this systematic literature review, we summarize publications by focusing on different pathways that stimulate pathophysiological cascades and remote organ damage. We propose that these parameters can be used for clinical decision making within the concept of safe definitive surgery (SDS) in the treatment of severely injured patients. Keywords Polytrauma surgical treatment strategy Safe Definitive Surgery Timing of major trauma surgery Damage contro