Imaging of the Hip

Imaging evaluation of the hip joint requires expert knowledge about the detailed anatomy and specific injuries. This chapter will include various osseous pathologies that can affect the hip joint such as stress fractures, osteonecrosis, or subchondral insufficiency fractures. Several types of mechanical impingement between the osseous components of the hip joint will be discussed such as femoroacetabular impingement, abnormal antetorsion, and subspine impingement. Detailed evaluation of damage to the labrum, articular cartilage, and other intra-articular structures is described

Influence of nozzle geometry on spray and combustion characteristics related to large two-stroke engine fuel injection systems

As emission regulations for large two-stroke marine Diesel engines increase as well, the manufacturers face similar problems as small-sized engine builders. The fuel injection, spray formation and subsequent combustion process remain among the main drivers for emissions of direct-injection, compression-ignition internal combustion engines. Since the fuel injection nozzle design of large two-stroke marine Diesel engines differs significantly, not only in size but especially regarding their non-symmetricity and eccentrical orifice arrangement, compared with four-stroke engines, the bulk of research available related to this topic is very limited. To further deepen the understanding of how in-nozzle cavitation flow during the fuel injection process affects the combustion behaviour in large two-stroke marine Diesel engines, transparent nozzle geometries have been used to link the cavitation phenomena with spray and combustion characteristics. A total of six single-orifice nozzles based on the original five-orifice nozzle design of large two-stroke marine Diesel fuel injectors, with and without hydro-erosive grinding, have been experimentally investigated under realistic engine conditions using highspeed optical measurement techniques and a unique constant-volume spray chamber that geometrically represents a combustion chamber of a large two-stroke marine Diesel engine at top dead centre. The spray morphology and combustion results reveal significant differences between the non- and hydro-erosive ground nozzle geometries. While the standard and angled nozzle versions remain similar, the eccentrical nozzle with its distinctive in-nozzle swirl cavitation pattern behaves differently, leading to a very reliable start of ignition behaviour and extreme wide spray angle

Sleep and Health-Related Characteristics among Adolescents during COVID-19: An Update

Two opposing effects on adolescents' health during COVID-19 lockdown have been described: A beneficial one due to longer sleep times during school closures and a detrimental one of psychological distress. This study investigated how sleep and health changed in the course of the pandemic when schools were open again. Overall, 12,238 adolescents in Switzerland participated in three cross-sectional online surveys: In 2017 under regular conditions (control group), during pandemic school closures in 2020 (closure group), and in 2021 still under pandemic conditions, but schools were open again (postclosure group). Sleep behavior and health-related characteristics (health-related quality of life; caffeine, alcohol, and nicotine use) in all three groups and depressive symptoms in the closure and postclosure groups were assessed. The sleep period on school days was longer in the closure group (median 9.00 h, interquartile range 8.25-9.75) and similar in the postclosure (7.92, 7.00-8.50) compared to the control group (7.75, 7.08-8.33). Health-related characteristics were better during school closures and similar to worse in the postclosure compared to the control group. Depressive symptom levels were higher in the postclosure than in the closure group. Therefore, beneficial effects were specific to school closures and adolescents' psychological distress increased over the course of the pandemic

Teachers' preference for later school start times

Early morning school start times conflict with biologically determined sleep phase preference and thus contribute to common sleep deficits. This conflict is most pronounced in adolescents, and numerous studies have confirmed that later school start times are beneficial for their sleep and health. However, the conflict continues to exist beyond adolescence and, accordingly, also teachers might benefit from later school start times, but this has gained little attention so far. Importantly, teachers' resistance to delay school start time is one of the key barriers for a successful implementation and, therefore, teachers' school start time preferences and influencing factors are important to consider. To this end, we conducted an online survey. Teachers (n = 694, 56.1% female) from 17 high schools in Zurich, Switzerland, participated in the study. They indicated their school start time preference. In addition, four predictor blocks were assessed: sociodemographic, school-/work-related, and sleep characteristics, as well as teachers' perception of students in the first morning lesson. Mixed models were applied to predict the preference. The majority (51%) endorsed later school start times (median preferred delay 25.2 min). School start time, sleep characteristics and perception of students in the first morning lesson were significant predictors for the preference. Thus, teachers with more misaligned sleep and higher awareness for students' issues in the early morning were more likely to report a preference. This suggests psychoeducation about sleep biology throughout life span to be an effective measure to increase teachers' support to delay school start time, especially because also they themselves are likely to benefit from later school start times

Adolescents' preference for later school start times

As the chronotype delays progressively throughout puberty, early morning school start times (SSTs) contradict the sleep biology of adolescents. Various studies have demonstrated beneficial effects of later SSTs on sleep and health; however, adolescents' preferences for SSTs have to date never been investigated in detail. The present online survey study aimed to fill this gap and explored influencing factors. A total of 17 high schools in the Canton of Zurich, Switzerland, circulated the survey among their students. Participants were included if they reported their sex, age, and school (n = 5,308). Students indicated whether they preferred later SSTs. Additionally, five predictor blocks were assessed: sociodemographic, school-related, sleep, leisure-time, and health-related characteristics. We applied multivariate logistic regression models with fixed and random effects to predict the preference. The mean (SD) age of the students was 16.09 (1.76) years (65.1% female). The majority (63.2%) endorsed later SSTs with a preferred delay of 55 min (interquartile range 25-75 min). In the multilevel analysis (n = 2,627), sex, mother tongue, sleep characteristics, mobile device use at bedtime, caffeine consumption, and health-related quality of life were significant predictors for the preference. Hence, the majority of adolescents preferred later SSTs, and especially those with sleep or health-related problems. These characteristics have been consistently shown to improve after delaying SSTs. Thus, also from adolescents' view, later SSTs should be considered to improve the adolescents' health

EEG Sleep Slow-Wave Activity as a Mirror of Cortical Maturation

Deep (slow wave) sleep shows extensive maturational changes from childhood through adolescence, which is reflected in a decrease of sleep depth measured as the activity of electroencephalographic (EEG) slow waves. This decrease in sleep depth is paralleled by massive synaptic remodeling during adolescence as observed in anatomical studies, which supports the notion that adolescence represents a sensitive period for cortical maturation. To assess the relationship between slow-wave activity (SWA) and cortical maturation, we acquired sleep EEG and magnetic resonance imaging data in children and adolescents between 8 and 19 years. We observed a tight relationship between sleep SWA and a variety of indexes of cortical maturation derived from magnetic resonance (MR) images. Specifically, gray matter volumes in regions correlating positively with the activity of slow waves largely overlapped with brain areas exhibiting an age-dependent decrease in gray matter. The positive relationship between SWA and cortical gray matter was present also for power in other frequency ranges (theta, alpha, sigma, and beta) and other vigilance states (theta during rapid eye movement sleep). Our findings indicate a strong relationship between sleep EEG activity and cortical maturation. We propose that in particular, sleep SWA represents a good marker for structural changes in neuronal networks reflecting cortical maturation during adolescenc

Digitalization of the IOM: A comprehensive cadaveric study for obtaining three-dimensional models and morphological properties of the forearm's interosseous membrane

State-of-the-art of preoperative planning for forearm orthopaedic surgeries is currently limited to simple bone procedures. The increasing interest of clinicians for more comprehensive analysis of complex pathologies often requires dynamic models, able to include the soft tissue influence into the preoperative process. Previous studies have shown that the interosseous membrane (IOM) influences forearm motion and stability, but due to the lack of morphological and biomechanical data, existing simulation models of the IOM are either too simple or clinically unreliable. This work aims to address this problematic by generating 3D morphological and tensile properties of the individual IOM structures. First, micro- and standard-CT acquisitions were performed on five fresh-frozen annotated cadaveric forearms for the generation of 3D models of the radius, ulna and each of the individual ligaments of the IOM. Afterwards, novel 3D methods were developed for the measurement of common morphological features, which were validated against established optical ex-vivo measurements. Finally, we investigated the individual tensile properties of each IOM ligament. The generated 3D morphological features can provide the basis for the future development of functional planning simulation of the forearm

Visuomotor adaptation, internal modelling, and compensatory movements in children with developmental coordination disorder

Background: Developmental coordination disorder (DCD) is one of the most prevalent developmental disorders in school-aged children. The mechanisms and etiology underlying DCD remain somewhat unclear. Altered visuomotor adaptation and internal model deficits are discussed in the literature. Aims: The study aimed to investigate visuomotor adaptation and internal modelling to determine whether and to what extent visuomotor learning might be impaired in children with DCD compared to typically developing children (TD). Further, possible compensatory movements during visuomotor learning were explored. Methods and procedures: Participants were 12 children with DCD (age 12.4 ± 1.8, four female) and 18 age-matched TD (12.3 ± 1.8, five female). Visuomotor learning was measured with the Motor task manager. Compensatory movements were parameterized by spatial and temporal variables. Outcomes and results: Despite no differences in visuomotor adaptation or internal modelling, significant main effects for group were found in parameters representing movement accuracy, motor speed, and movement variability between DCD and TD. Conclusions and implications: Children with DCD showed comparable performances in visuomotor adaptation and internal modelling to TD. However, movement variability was increased, whereas movement accuracy and motor speed were reduced, suggesting decreased motor acuity in children with DCD

A compactness theorem for complete Ricci shrinkers

We prove precompactness in an orbifold Cheeger-Gromov sense of complete gradient Ricci shrinkers with a lower bound on their entropy and a local integral Riemann bound. We do not need any pointwise curvature assumptions, volume or diameter bounds. In dimension four, under a technical assumption, we can replace the local integral Riemann bound by an upper bound for the Euler characteristic. The proof relies on a Gauss-Bonnet with cutoff argument.Comment: 28 pages, final version, to appear in GAF

Naturally-Occurring Zirconolites - Analogues for the Long-Term Encapsulation of Actinides in Synroc

The use of natural zirconolites to assess the effect of α-decay damage and geochemical alteration on the release of actinides from HLW wasteforms is critically examined. There is evidence that the natural zirconolites provide a good chemical and radi-ation damage analogy for the HLW wasteforms, but additional work is required to define the geochemical environments in which zirconolite is stable or unstable (e.g., suffering corrosion or chemical alteration, including loss of actinides)