Tuning and Tracking of Coherent Shear Waves in Molecular Films

We have determined the time-dependent displacement fields in molecular sub-micrometer thin films as response to femtosecond and picosecond laser pulse heating by time-resolved X-ray diffraction. This method allows a direct absolute determination of the molecular displacements induced by electron–phonon interactions, which are crucial for, for example, charge transport in organic electronic devices. We demonstrate that two different modes of coherent shear motion can be photoexcited in a thin film of organic molecules by careful tuning of the laser penetration depth relative to the thickness of the film. The measured response of the organic film to impulse heating is explained by a thermoelastic model and reveals the spatially resolved displacement in the film. Thereby, information about the profile of the energy deposition in the film as well as about the mechanical interaction with the substrate material is obtained

Experimental animal models for brain abscess: a systematic review

Brain abscess (BA) is a rare, but severe infection and experimental BA animal models may prove crucial for advances in treatment. This review describes the development of experimental BA models and the clinical advances obtained from these, in a historical perspective. Experimental BA studies from inception until June 15, 2022, were included by searching the PubMed and Embase databases. Inclusion required the use of an experimental BA animal model. Non-bacterial BA models, in vitro studies, veterinarian case-reports, and articles written in non-English language were excluded. Bias was not systematically assessed, and the review was not registered at the PROSPERO. 79 studies were included. The majority of animal BA models have been based on small rodents using Staphylococcus aureus. The models have delineated the natural development of BA and provided detailed descriptions of the histopathological characteristics consisting of a necrotic centre surrounded by layers of inflammatory cells and fibroblasts encapsulated by a dense collagenous layer. Radiological studies of animal BA have been shown to correlate with the corresponding stages of human BA in both computed tomography and magnetic resonance imaging and may guide diagnosis as well as the timing of neurosurgical intervention. Moreover, pharmacokinetic studies of the intracavitary penetration of various antimicrobials have helped inform medical treatment of BA. Other studies have examined the diverse effects of corticosteroids including decreased cerebral oedema, intracranial pressure, and intracavitary drug concentration, whereas concerns on decreased or weakened capsule formation could not be confirmed. Finally, studies on the immunological response to BA have highlighted potential future immunomodulatory targets. Animal models have been vital for improvements in the management of BA. Experimental BA models resembling human disease including polymicrobial infection by oral cavity flora in large animals are needed.</p

Brain abscess caused by oral cavity bacteria: a nationwide, population-based cohort study

BACKGROUND: Oral cavity bacteria are the most frequent etiology of brain abscess. Yet, data on the clinical presentation and outcome are scarce.METHODS: Nationwide, population-based study comprising all adults (≥18 years) with brain abscess due to oral cavity bacteria in Denmark from 2007-2020. Prognostic factors for unfavorable outcome (Glasgow Outcome Scale of 1-4) were examined by modified Poisson regression to compute adjusted relative risks (RR) with 95% confidence intervals (CI).RESULTS: Among 287 identified patients, the median age was 58 years (interquartile range 47-66) and 96/287 (33%) were female. Pre-existing functional impairment was absent or mild in 253/280 (90%) and risk factors for brain abscess included immuno-compromise 95/287 (33%), dental infection 68/287 (24%), and ear-nose-throat infection 33/287 (12%). Overall, a neurological deficit was present in 246/276 (86%) and in combination with headache and fever in 64/287 (22%). Identified microorganisms were primarily Streptococcus anginosus group, Fusobacterium, Actinomyces, and Aggregatibacter spp., and 117/287 (41%) were polymicrobial. Unfavorable outcome occurred in 92/246 (37%) at six months after discharge and was associated with antibiotics before neurosurgery (RR 3.28, 95% CI 1.53-7.04), rupture (RR 1.89, 95% CI 1.34-2.65), and immuno-compromise (RR 1.80, 95% CI 1.29-2.51), but not with specific targeted antibiotic regimens. Identified dental infection was associated with favorable prognosis (RR 0.58, 95% CI 0.36-0.93).CONCLUSION: Brain abscess due to oral cavity bacteria often occurred in previously healthy individuals without predisposing dental infections. Important risk factors for unfavorable outcome were rupture and immuno-compromise. However, outcome was not associated with specific antibiotic regimens supporting carbapenem-sparing strategies.</p