Assessing the intergranular crack initiation probability of a grain boundary distribution by an experimental misalignment study of adjacent slip systems

Crack initiation at grain boundaries due to blocked slip transfer of dislocations is a main failure mechanism during the fatigue of metals. A quantification of the resistance effect of a grain boundary is needed to assess a textured or texture-free microstructure for fatigue strength. Geometric approaches based on the misalignment of slip systems in adjacent grains are widely used. Hence, we validated the geometric transmission factor of Shen et al. in coarse-grained high-purity aluminum under the assumption that the combination of a large slip activity and a blocked slip at a grain boundary leads to intergranular crack initiation and revealed that a detailed knowledge of the 3D-orientation of the grain boundary is essential. Thereby we gathered information about the 3D-microstructure using FIB-cross-sectioning. Hence it is possible to evaluate potential crack initiation sites for a specific microstructure or to estimate the fatigue strength of a textured microstructure in terms of a crack initiation probability

Transition from Jaynes-Cummings to Autler-Townes ladder in a quantum dot-microcavity system

The research leading to these results has received funding from the German Research Foundation (DFG) via Projects No. Ka2318/4-1 and No. Re2974/3-1, the SFB 787 "Semiconductor Nanophotonics: Materials, Models, Devices", and from the European Research Council under the European Union's Seventh Framework ERC Grant Agreement No. 615613. A. C. gratefully acknowledges support from SFB 910: "Control of self-organizing nonlinear systems".We study experimentally and theoretically a coherently-driven strongly-coupled quantum dot-microcavity system. Our focus is on physics of the unexplored intermediate excitation regime where the resonant laser field dresses a strongly-coupled single exciton-photon (polariton) system resulting in a ladder of laser-dressed Jaynes-Cummings states. In that case both the coupling of the emitter to the confined light field of the microcavity and to the light field of the external laser are equally important, as proved by observation of injection pulling of the polariton branches by an external laser. This intermediate interaction regime is of particular interest since it connects the purely quantum mechanical Jaynes-Cummings ladder and the semi-classical Autler-Townes ladder. Exploring the driving strength-dependence of the mutually coupled system we establish the maximum in the resonance fluorescence signal to be a robust fingerprint of the intermediate regime and observe signatures indicating the laser-dressed Jaynes-Cummings ladder. In order to address the underlying physics we excite the coupled system via the matter component of fermionic nature undergoing saturation - in contrast to commonly used cavity-mediated excitation.PostprintPeer reviewe

Late-Onset Prosthetic Endocarditis with Paraaortic Abscess Caused by Cutibacterium acnes

Cutibacterium acnes, an integral component of the skin’s customary bacterial flora, represents a Gram-positive anaerobic bacterium characterized by its low virulence. Despite its low virulence, the pathogen can cause profound-seated infections as well as infections linked to medical devices. We report a case study of a prosthesis endocarditis accompanied by a paraaortic abscess caused by C. acnes, a development occurring five years prior to composite aortic root and valve replacement. At the point of admission, the patient presented with a combination of symptoms hinting at a subacute progression, such as weight loss, chest pain, and limitations of cardiopulmonary functionality. An anaerobic pathogen, namely C. acnes, was detected in a singular blood culture vial. Since first-line imaging modalities such as echocardiography did not reveal any signs of inflammation, and in the case of a suspected diagnosis for IE, did not show high pretest probability, further diagnostic imaging such as 18F-FDG PET CT was put to use. Here, a highly elevated glucose metabolism around the aortic valve ring was detected, pointing to an inflammatory process. The patient received adjusted intravenous antibiotic therapy over a course of six weeks; he then underwent surgical therapy via re-replacement of the aortic root and valve using a composite conduit. Advanced microbiological analyses, including the amplification of PCR and valve sequencing via 16S rDNA, mainly detected one pathogen: C. acnes. Delayed onset with mild symptoms and laboratory findings is characteristic of infective endocarditis by C. acnes. Due to its high rate of complications, mortality, and morbidity, an infection should not be disregarded as contamination. Recommendations from different studies underline a combination of a positive blood culture and microbiological evidence to differentiate between contamination and true infection in the case of an infection involving C. acnes. Serial blood cultures with prolonged incubation, advanced microbiological analyses, and modified Duke criteria including second-line imaging techniques should be utilized for further evaluation

Symptomatic Diastasis Rectus Abdominis in Children: Review of Current Management Options and Presentation of a Novel Minimally Invasive Epifascial Repair Technique

Several surgical techniques are available for an adult patient collective with diastasis recti. Only few research papers addresses the treatment options of diastasis of the rectus abdominis in children. In this case series, we present a new technique of epifascial repair as a novel possibility in successfully repairing defects of the anterior abdominal wall using minimally invasive surgery. In this case series, we present an epifascial repair technique for patients with a diastasis recti with a dehiscence cranial of the umbilicus. Four pediatric patients with symptomatic rectus diastasis were treated with this new surgical technique. All procedures were conducted successfully, and no recurrence was observed in the follow up. All patients showed clinical regression of the rectus diastasis without any postoperative abdominal wall protrusion and good improvement of the symptoms. Intraoperative intraperitoneal air loss, postoperative scar keloid, thermal lesions due to Ultracision and one seroma/hematoma after the removal of the drain were minor complications observed during the follow-up