Lattice Boltzmann Methods for Particulate Flows with Medical and Technical Applications

Particulate flows appear in numerous medical and technical applications. The main aim of this thesis is to contribute models and numerical schemes towards an accurate as well as efficient simulation of a huge number of arbitrarily shaped particles. We therefore develop holistic mesoscopic models and simulation approaches using the Lattice Boltzmann Method, that on massively parallel machines efficiently solve a variety of problems of particulate flows

Bosonic excitation spectra of superconducting Bi2Sr2CaCu2O8+δ\mathrm{Bi_2Sr_2CaCu_2O_{8+\delta}} and YBa2Cu3O6+x\mathrm{YBa_2Cu_3O_{6+x}} extracted from scanning tunneling spectra

A detailed interpretation of scanning tunneling spectra obtained on unconventional superconductors enables one to gain information on the pairing boson. Decisive for this approach are inelastic tunneling events. Due to the lack of momentum conservation in tunneling from or to the sharp tip, those are enhanced in the geometry of a scanning tunneling microscope compared to planar tunnel junctions. This work extends the method of obtaining the bosonic excitation spectrum by deconvolution from tunneling spectra to nodal $d$-wave superconductors. In particular, scanning tunneling spectra of slightly underdoped $\mathrm{Bi_2Sr_2CaCu_2O_{8+\delta}}$ with a $T_c$ of $82\,\mathrm{K}$ and optimally doped $\mathrm{YBa_2Cu_3O_{6+x}}$ with a $T_c$ of $92\,\mathrm{K}$ reveal a resonance mode in their bosonic excitation spectrum at $\Omega_\mathrm{res} \approx 63\,\mathrm{meV}$ and $\Omega_\mathrm{res} \approx 61\,\mathrm{meV}$ respectively. In both cases, the overall shape of the bosonic excitation spectrum is indicative of predominant spin scattering with a resonant mode at $\Omega_\mathrm{res}<2\Delta$ and overdamped spin fluctuations for energies larger than $2\Delta$. To perform the deconvolution of the experimental data, we implemented an efficient iterative algorithm that significantly enhances the reliability of our analysis

Prospective Prediction of Posttraumatic Stress Disorder Symptoms Using Fear Potentiated Auditory Startle Responses

Background: Posttraumatic stress disorder (PTSD) has been most consistently associated with exaggerated physiologic reactivity to startling sounds when such sounds occur in threatening contexts. There is conflicting evidence about whether startle hyperreactivity is a preexisting vulnerability factor for PTSD or an acquired result of posttrauma neural sensitization. Until now, there have been no prospective studies of physiologic reactivity to startling sounds in threatening contexts as predictors of PTSD symptoms. Methods: One hundred and thirty-eight police academy cadets without current psychopathology were exposed to repeated 106-dB startling sounds under increasing (low, medium, or high) threat of mild electric shock while their eye-blink electromyogram, skin conductance, heart rate, and subjective fear responses were recorded. Measures of response habituation were also calculated. Following 1 year of exposure to police-related trauma, these participants were assessed for PTSD symptom severity. Results: After accounting for other baseline variables that were predictive of PTSD symptom severity (age and general psychiatric distress), more severe PTSD symptoms were prospectively and independently predicted by the following startle measures: greater subjective fear under low threat, greater skin conductance under high threat, and slower skin conductance habituation. Conclusions: These results imply that hypersensitivity to contextual threat (indexed by greater fear under low threat), elevated sympathetic nervous system reactivity to explicit threat (indexed by larger responses under high threat), and failure to adapt to repeated aversive stimuli (evidenced by slower habituation) are all unique preexisting vulnerability factors for greater PTSD symptom severity following traumatic stress exposure. These measures may eventually prove useful for preventing PTSD

Psychiatric comorbidity and psychosocial impairment among patients with vertigo and dizziness

Background: Vertigo and dizziness are often not fully explained by an organic illness, but instead are related to psychiatric disorders. This study aimed to evaluate psychiatric comorbidity and assess psychosocial impairment in a large sample of patients with a wide range of unselected organic and non-organic (ie, medically unexplained) vertigo/dizziness syndromes. Methods: This cross-sectional study involved a sample of 547 patients recruited from a specialised interdisciplinary treatment centre for vertigo/dizziness. Diagnostic evaluation included standardised neurological examinations, structured clinical interview for major mental disorders (SCID-I) and self-report questionnaires regarding dizziness, depression, anxiety, somatisation and quality of life. Results: Neurological diagnostic workup revealed organic and non-organic vertigo/dizziness in 80.8% and 19.2% of patients, respectively. In 48.8% of patients, SCID-I led to the diagnosis of a current psychiatric disorder, most frequently anxiety/phobic, somatoform and affective disorders. In the organic vertigo/dizziness group, 42.5% of patients, particularly those with vestibular paroxysmia or vestibular migraine, had a current psychiatric comorbidity. Patients with psychiatric comorbidity reported more vertigo-related handicaps, more depressive, anxiety and somatisation symptoms, and lower psychological quality of life compared with patients without psychiatric comorbidity. Conclusions: Almost half of patients with vertigo/dizziness suffer from a psychiatric comorbidity. These patients show more severe psychosocial impairment compared with patients without psychiatric disorders. The worst combination, in terms of vertigo-related handicaps, is having non-organic vertigo/dizziness and psychiatric comorbidity. This phenomenon should be considered when diagnosing and treating vertigo/dizziness in the early stages of the disease

Validation studies of virtual reality simulation performance metrics for mechanical thrombectomy in ischemic stroke

Introduction: Mechanical thrombectomy (MT) has transformed the treatment of ischemic stroke. However, patient access to MT may be limited due to a shortage of doctors specifically trained to perform MT. The studies reported here were done to (1) develop, operationally define, and seek consensus from procedure experts on the metrics which best characterize a reference procedure for the performance of an MT for ischemic stroke and (2) evaluate their construct validity when implemented in a virtual reality (VR) simulation. Methods: In study 1, the metrics for a reference approach to an MT procedure for ischemic stroke of 10 phases, 46 steps, and 56 errors and critical errors, were presented to an international Delphi panel of 21 consultant level interventional neuroradiologists (INRs). In study 2, the metrics were used to assess 8 expert and 10 novice INRs performing a VR simulated routine MT procedure. Results: In study 1, the Delphi panel reached consensus on the appropriateness of the procedure metrics for a reference approach to MT in ischemic stroke. Group differences in median scores in study 2 demonstrated that experienced INRs performed the case 19% faster (P=0.029), completed 40% more procedure phases (P=0.009), 20% more steps (P=0.012), and made 42% fewer errors (P=0.016) than the novice group. Conclusions: The international Delphi panel agreed metrics implemented in a VR simulation of MT distinguished between the computer scored procedure performance of INR experts and novices. The studies reported here support the demonstration of face, content, and construct validity of the MT metrics

Tribological system for cold sheet metal forming based on volatile lubricants and laser structured surfaces

AbschlussberichtA novel tribological system has been developed, in which volatile lubricants (carbon dioxide - CO2 or nitrogen- N2) are used as a substitute for mineral oil-based lubricants in deep drawing processes. This process enables the introduction of an intermediate medium under high pressure through flow-optimized, laser-drilled micro holes into the contact surfaces. This eliminates the need for subsequent, cost-intensive cleaning processes, as the volatile lubricants evaporate without leaving any residue during expansion to ambient pressure. The design of initial micro hole geometries was based on simulations of the flow behaviour of the lubricants passing through, which in turn were validated using pressure reactor tests. In addition, the wetting behaviour of CO2 on relevant surfaces (tool surface and sheet material surface) was investigated experimentally using the captive-bubble-method. Thus, the optimal design of the micro holes (diameter, hole geometry and number of micro holes) could be determined using flat strip drawing tests. The optimal micro hole geometry determined in this way is suited for the use of both CO2 and N2 as volatile lubricant. Furthermore, extensive investigations for the production of the required micro hole geometry by laser drilling were carried out. The fundamentals for drilling micro holes in steel with high aspect ratios could be developed using an ultrashort pulsed research laser with very high pulse energy. Further experiments were conducted using an ultrashort pulsed prototype laser of the kW-class specially developed to increase productivity when drilling a multitude of micro holes with higher average laser power. The novel tribological system has been characterised by means of strip drawing tests and stretch bending tests. For both, CO2 (liquid) and N2 (gaseous), relatively low friction values could be achieved compared to conventional lubricants. It could be shown that deep drawing with both CO2 and N2 as dry lubricants is possible. Here, usage of the volatile lubricants not only allows the replacement of mineral oil based lubricants, but even improves the tribological system with regard to frictional forces in sheet metal forming. The feasibility of the new tribological system has been proven by performing deep drawing tests of rectangular cups. These tests showed a significantly enlarged process window of the forming process, which emphasise the tremendous potential of this new tribological system.12816

Whole Genome Pyrosequencing of Rare Hepatitis C Virus Genotypes Enhances Subtype Classification and Identification of Naturally Occurring Drug Resistance Variants

Background. Infection with hepatitis C virus (HCV) is a burgeoning worldwide public health problem, with 170 million infected individuals and an estimated 20 million deaths in the coming decades. While 6 main genotypes generally distinguish the global geographic diversity of HCV, a multitude of closely related subtypes within these genotypes are poorly defined and may influence clinical outcome and treatment options. Unfortunately, the paucity of genetic data from many of these subtypes makes time-consuming primer walking the limiting step for sequencing understudied subtypes. Methods. Here we combined long-range polymerase chain reaction amplification with pyrosequencing for a rapid approach to generate the complete viral coding region of 31 samples representing poorly defined HCV subtypes. Results. Phylogenetic classification based on full genome sequences validated previously identified HCV subtypes, identified a recombinant sequence, and identified a new distinct subtype of genotype 4. Unlike conventional sequencing methods, use of deep sequencing also facilitated characterization of minor drug resistance variants within these uncommon or, in some cases, previously uncharacterized HCV subtypes. Conclusions. These data aid in the classification of uncommon HCV subtypes while also providing a high-resolution view of viral diversity within infected patients, which may be relevant to the development of therapeutic regimens to minimize drug resistanc