The PERCIVAL detector: first user experiments

The PERCIVAL detector is a CMOS imager designed for the soft X-ray regime at photon sources. Although still in its final development phase, it has recently seen its first user experiments: ptychography at a free-electron laser, holographic imaging at a storage ring and preliminary tests on X-ray photon correlation spectroscopy. The detector performed remarkably well in terms of spatial resolution achievable in the sample plane, owing to its small pixel size, large active area and very large dynamic range; but also in terms of its frame rate, which is significantly faster than traditional CCDs. In particular, it is the combination of these features which makes PERCIVAL an attractive option for soft X-ray science.

Injury incidence rates in women's football: a systematic review and meta-analysis of prospective injury surveillance studies

OBJECTIVE

To review the literature to establish overall, match and training injury incidence rates (IIRs) in senior (≥18 years of age) women's football (amateur club, elite club and international).

DESIGN

Systematic review and meta-analysis of overall, match and training IIRs in senior women's football, stratified by injury location, type and severity.

DATA SOURCES

MEDLINE via PubMed; EMBASE via Ovid; CINAHL via EBSCO and Web of Science were searched from earliest record to July 2021.

ELIGIBILITY CRITERIA FOR SELECTING STUDIES

(1) football players participating in a senior women's football league (amateur club or elite club) or a senior women's international football tournament; (2) the study had to report IIRs or provide sufficient data from which this outcome metric could be calculated through standardised equations; (3) a full-text article published in a peer-reviewed journal before July 2021; (4) a prospective injury surveillance study and (5) case reports on single teams were ineligible.

RESULTS

17 articles met the inclusion criteria; amateur club (n=2), elite club (n=10), international (n=5). Overall, match and training 'time-loss' IIRs are similar between senior women's elite club football and international football. 'Time-loss' training IIRs in senior women's elite club football and international football are approximately 6-7 times lower than their equivalent match IIRs. Overall 'time-loss' IIRs stratified by injury type in women's elite club football were 2.70/1000 hours (95% CI 1.12 to 6.50) for muscle and tendon, 2.62/1000 hours (95% CI 1.26 to 5.46) for joint and ligaments, and 0.76/1000 hours (95% CI 0.55 to 1.03) for contusions. Due to the differences in injury definitions, it was not possible to aggregate IIRs for amateur club football.

CONCLUSION

Lower limb injuries incurred during matches are a substantial problem in senior women's football. The prevention of lower limb joint, ligament, muscle and tendon injuries should be a central focus of injury prevention interventions in senior women's amateur club, elite club and international football.

PROSPERO REGISTRATION NUMBER

CRD42020162895.

Systematic Review of Pre-injury Migraines as a Vulnerability Factor for Worse Outcome Following Sport-Related Concussion

Background

Individuals with migraine disorders may be affected differently by concussions compared to individuals without migraine disorders. Prior studies on this topic have had mixed results. The purpose of this study was to systematically examine clinical outcomes following a sport-related concussion in athletes who have a pre-injury history of migraines.

Methods

All studies published prior to 15 May 2021 that examined pre-injury migraines as a possible predictor of clinical recovery from concussion were included. The search included (i) sport/athlete-related terms, (ii) concussion-related terms, and (iii) diverse predictor/modifier terms. After removing duplicates, 5,118 abstracts were screened, 538 full-text articles were reviewed, and 27 articles were included for narrative synthesis without meta-analysis (n = 25 with unique samples). Risk of bias was assessed using the domain-based Quality In Prognosis Studies (QUIPS) tool.

Results

Most studies did not find pre-injury migraines to be associated with concussion outcome, but several of these studies had small or very small sample sizes, as well as other methodological weaknesses. Risk of bias varied greatly across studies. Some of the larger, better-designed studies suggested pre-injury migraines may be a risk factor for worse concussion outcome. Most articles examined pre-injury migraines as an exploratory/secondary predictor of concussion outcome; very few were designed to examine migraine as the primary focus of the study. Migraine history was predominantly based on self-report and studies included minimal information about migraine (e.g., age of onset, frequency/severity, past treatment). Effect sizes were usually not reported or able to be calculated from reported study data.

Conclusion

There is some evidence to suggest that pre-injury migraines may be a vulnerability factor for a worse outcome following concussion, with studies having the lowest risk of bias reporting a positive association. Future studies should focus on improving methodological quality when assessing the relationship between pre-injury migraines and concussion outcome and better characterizing pre-injury migraine status.

Systematic Review Registration

https://www.crd.york.ac.uk/prospero/display_record.php?ID=CRD42019128292, identifier: PROSPERO 2019 CRD42019128292.

Implementing the 27 PRISMA 2020 Statement items for systematic reviews in the sport and exercise medicine, musculoskeletal rehabilitation and sports science fields: the PERSiST (implementing Prisma in Exercise, Rehabilitation, Sport medicine and SporTs science) guidance

Poor reporting of medical and healthcare systematic reviews is a problem from which the sports and exercise medicine, musculoskeletal rehabilitation, and sports science fields are not immune. Transparent, accurate and comprehensive systematic review reporting helps researchers replicate methods, readers understand what was done and why, and clinicians and policy-makers implement results in practice. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) Statement and its accompanying Explanation and Elaboration document provide general reporting examples for systematic reviews of healthcare interventions. However, implementation guidance for sport and exercise medicine, musculoskeletal rehabilitation, and sports science does not exist. The Prisma in Exercise, Rehabilitation, Sport medicine and SporTs science (PERSiST) guidance attempts to address this problem. Nineteen content experts collaborated with three methods experts to identify examples of exemplary reporting in systematic reviews in sport and exercise medicine (including physical activity), musculoskeletal rehabilitation (including physiotherapy), and sports science, for each of the PRISMA 2020 Statement items. PERSiST aims to help: (1) systematic reviewers improve the transparency and reporting of systematic reviews and (2) journal editors and peer reviewers make informed decisions about systematic review reporting quality.

Age of First Exposure to Contact and Collision Sports and Later in Life Brain Health: A Narrative Review

A controversial theory proposes that playing tackle football before the age of 12 causes later in life brain health problems. This theory arose from a small study of 42 retired National Football League (NFL) players, which reported that those who started playing tackle football at a younger age performed worse on selected neuropsychological tests and a word reading test. The authors concluded that these differences were likely due to greater exposure to repetitive neurotrauma during a developmentally sensitive maturational period in their lives. Several subsequent studies of current high school and collegiate contact/collision sports athletes, and former high school, collegiate, and professional tackle football players have not replicated these findings. This narrative review aims to (i) discuss the fundamental concepts, issues, and controversies surrounding existing research on age of first exposure (AFE) to contact/collision sport, and (ii) provide a balanced interpretation, including risk of bias assessment findings, of this body of evidence. Among 21 studies, 11 studies examined former athletes, 8 studies examined current athletes, and 2 studies examined both former and current athletes. Although the literature on whether younger AFE to tackle football is associated with later in life cognitive, neurobehavioral, or mental health problems in former NFL players is mixed, the largest study of retired NFL players (N = 3,506) suggested there was not a significant association between earlier AFE to organized tackle football and worse subjectively experienced cognitive functioning, depression, or anxiety. Furthermore, no published studies of current athletes show a significant association between playing tackle football (or other contact/collision sports) before the age of 12 and cognitive, neurobehavioral, or mental health problems. It is important to note that all studies were judged to be at high overall risk of bias, indicating that more methodologically rigorous research is needed to understand whether there is an association between AFE to contact/collision sports and later in life brain health. The accumulated research to date suggests that earlier AFE to contact/collision sports is not associated with worse cognitive functioning or mental health in (i) current high school athletes, (ii) current collegiate athletes, or (iii) middle-aged men who played high school football. The literature on former NFL players is mixed and does not, at present, clearly support the theory that exposure to tackle football before age 12 is associated with later in life cognitive impairment or mental health problems.

Condition-specific health-related quality of life amongst amateur athletes six months and one-year following sport-related concussion: A prospective, follow-up

OBJECTIVE

To prospectively investigate the condition-specific health-related quality of life (HRQoL) of athletes six months and one-year following sport-related concussion.

DESIGN

Prospective, longitudinal study.

SETTING

Clinical research centre at university school of public health.

PARTICIPANTS

Amateur athletes who were diagnosed with sport-related concussion within one-week after presenting to a hospital emergency department were recruited along with sex-, age-, and activity-matched, non-concussed, control athletes. Concussion and control participants were assessed six months and one-year following sport-related concussion and study enrolment, respectively.

MAIN OUTCOME MEASURES

Participants completed the Post-Concussion Symptom Scale and five condition-specific HRQoL patient-reported outcome measures - Headache Impact Test-6, Fatigue Severity Scale, Neck Disability Index, Generalised Anxiety Disorder-7, and Dizziness Handicap Inventory. We performed Frequentist and Bayesian mixed-design analyses of variance to compare the concussion group and control group at both assessments and quantify whether there was greater evidence in favour of the null hypothesis compared with the alternative hypothesis.

RESULTS

At six-month and one-year assessments, the concussion group (n = 47; male = 72%; mean (SD) age = 22.68 (5.07)) and the control group (n = 47; male = 72%; mean (SD) age = 23.81 (4.60)) reported similar clinical symptom severity scores and condition-specific HRQoL. The proportion of athletes in the concussion group with clinically-impaired scores was similar to the proportion of non-concussed athletes with clinically-impaired scores. At six-month and one-year assessments, there was moderate-to-very strong evidence that there was no difference between concussion and control participants' perceptions of the effects of headache, fatigue, neck pain, anxiety, and dizziness on HRQoL.

CONCLUSION

There was moderate-to-very strong evidence in favour of no difference between the concussion and control groups on symptom severity scores and condition-specific HRQoL patient-reported outcome measures at six-month and one-year assessments. These results suggest that condition-specific HRQoL returns to the levels of non-concussed individuals within six months following sport-related concussion.

Age of First Exposure to Football Is Not Associated With Later-in-Life Cognitive or Mental Health Problems

Background: The purpose of this study was to determine if earlier age of first exposure to football is associated with worse brain health in middle-aged and older adult men who played high school football.

Methods: Men from the United States, aged 35 and older, who reported playing high school football, completed a customized, online health survey via the Amazon Mechanical Turk (mTurk) platform. Survey items included physical, psychological, and cognitive symptoms over the past week and over the past year, sports participation history (including age of first exposure to football), medical history, and concussion history. Participants also completed the Patient Health Questionnaire-8 (PHQ-8) and the British Columbia Post-Concussion Symptom Inventory (BC-PSI).

Results: There were 186 men (age M = 51.78, SD = 10.93) who participated in high school football, and 87 (46.8%) reported football participation starting before the age of 12 and 99 (53.2%) reported football participation at or after the age of 12. Those who started playing football at an earlier age reported a greater number of lifetime concussions (M = 1.95, SD = 1.79) compared to those who started playing at age 12 or later (M = 1.28, SD = 1.52; U = 3,257.5, p = 0.003). A similar proportion of men who played football before vs. after the age of 12 reported a lifetime history of being prescribed medications for depression, anxiety, chronic pain, headaches, or memory problems. When comparing men who played football before vs. after the age of 12, the groups did not differ significantly in their ratings of depression, anger, anxiety, headaches, migraines, neck or back pain, chronic pain, concentration problems, or memory problems over the past week or the past year. The two groups did not differ significantly in their ratings of current symptoms of depression (PHQ-8; U = 4,187.0, p = 0.74) or post-concussion-like symptoms (BC-PSI; U = 3,944.0, p = 0.53). Furthermore, there were no statistically significant correlations between the age of first exposure to football, as a continuous variable, and PHQ-8 or BC-PSI scores.

Conclusion: This study adds to a rapidly growing body of literature suggesting that earlier age of first exposure to football is not associated with later-in-life brain health.

Participation in pre-injury level sport one-year following sport-related concussion: A prospective, matched cohort study

OBJECTIVES

To estimate the times taken to receive clearance to return to sporting activity and to return to pre-injury level of sport competition following sport-related concussion, and to estimate the proportion of athletes who were participating at their pre-injury level of sport competition six months and one-year following sport-related concussion.

DESIGN

Prospective cohort study.

METHODS

Amateur, adult athletes (16-38 years old) were diagnosed with sport-related concussion at a university-affiliated hospital emergency department. Participants were assessed within one-week, upon medical clearance to return to sporting activity, two weeks following return to sporting activity, six months, and 12 months following sport-related concussion. We assessed sex-, age-, and activity-matched non-injured, control participants at matched time-points. Participants were asked during each study assessment whether they were participating in any sport, in a different sport than before their sport-related concussion, in the same sport but at a lower level of competition than before their sport-related concussion, or in the same sport at the same level of competition than before their sport-related concussion.

RESULTS

Fifty concussed participants and 50 non-injured, control participants completed the study. The median times taken to receive clearance to return to sporting activity and to return to pre-injury level of sport competition following sport-related concussion were 13 days (95%CI=12,16) and 31 days (95%CI=28,32), respectively. One-year following sport-related concussion, 52% of participants reported that they were no longer participating in the same sport and at the same level of competition as they were before their sport-related concussion, compared with only 24% of participants in the non-injured, control group (p=0.003).

CONCLUSIONS

A greater percentage of athletes in the concussion group were not participating at their perceived pre-injury level of sport competition one-year following sport-related concussion compared with a non-injured control group. Factors that explain the lower proportion of amateur athletes participating at their pre-injury level of sport competition one-year after sport-related concussion are likely multifaceted and should be considered in future investigations.

Age of First Exposure to Football Is Not Associated with Midlife Brain Health Problems

The purpose of this study was to determine if earlier age of first exposure (AFE) to football is associated with worse brain health in middle-aged men who played high school football. We assessed 123 men 35-55 years of age, who played high school football, using (1) a survey of demographic information as well as medical, sport participation, and concussion history; (2) the Patient Health Questionnaire-8 (PHQ-8); and (3) the British Columbia Post-Concussion Symptom Inventory (BC-PSI). Sixty-two (50.4%) men reported football participation starting before the age of 12 (i.e., AFE <12 years) and 61 (49.6%) reported football participation at or after the age of 12 (AFE > 12 years). Compared with those with AFE >12 years, a similar proportion of former high school football players who began playing tackle football before age 12 reported that they had been prescribed medications for mental health problems or that they had recently experienced symptoms of anxiety, depression, memory loss, chronic pain, or headaches. Moreover, there was no significant difference in their lifetime history of treatment by a mental health professional. The groups did not differ significantly on PHQ-8 (U = 1839.0, p = 0.791) or BC-PSI total scores (U = 1828.5, p = 0.751). These findings suggest that earlier AFE to football is not associated with worse brain health in middle-aged men in this sample who played high school football.

Using functional movement tests to investigate the presence of sensorimotor impairment in amateur athletes following sport-related concussion: A prospective, longitudinal study

OBJECTIVE

To longitudinally investigate the presence of sensorimotor impairments in amateur athletes following sport-related concussion using two functional movement tests.

DESIGN

Prospective, longitudinal study.

SETTING

Human movement analysis laboratory.

PARTICIPANTS

Athletes who presented to a hospital emergency department and were diagnosed with sport-related concussion, and sex-, age-, and activity-matched non-concussed, control athletes. Concussed participants were assessed within one-week following sport-related concussion, upon clearance to return-to-sporting activity (RTA), and two weeks after RTA. Control participants were assessed at an initial time-point and approximately two and four weeks following their initial study assessment.

MAIN OUTCOMES MEASURES

At each laboratory assessment, participants completed two functional movement tests: the Star Excursion Balance Test to evaluate anterior reach distance (normalised for leg length) and fractal dimension (centre of pressure path complexity), and the Multiple Hop Test to evaluate corrective postural strategies and time-to-stabilisation.

RESULTS

Fifty concussed athletes and 50 control athletes completed the study. There were no significant differences at any study assessment between the concussion and control group on the Star Excursion Balance Test anterior reach distance or fractal dimension (centre of pressure path complexity). During the Multiple Hop Test, the concussion group used a significantly greater number of corrective postural strategies than the control group one-week following sport-related concussion and upon clearance to RTA, but not two weeks following RTA.

CONCLUSION

Recently concussed athletes made a greater number of corrective postural strategies than control participants during the Multiple Hop Test upon clearance to RTA but not two weeks after RTA. The Multiple Hop Test may offer a clinically useful tool for practitioners to examine the recovery of subtle sensorimotor impairments and related RTA readiness.

Are questionable research practices facilitating new discoveries in sport and exercise medicine? The proportion of supported hypotheses is implausibly high

Questionable research practices (QRPs) are intentional and unintentional practices that can occur when designing, conducting, analysing, and reporting research, producing biased study results. Sport and exercise medicine (SEM) research is vulnerable to the same QRPs that pervade the biomedical and psychological sciences, producing false-positive results and inflated effect sizes. Approximately 90% of biomedical research reports supported study hypotheses, provoking suspicion about the field-wide presence of systematic biases to facilitate study findings that confirm researchers' expectations. In this education review, we introduce three common QRPs (ie, HARKing, P-hacking and Cherry-picking), perform a cross-sectional study to assess the proportion of original SEM research that reports supported study hypotheses, and draw attention to existing solutions and resources to overcome QRPs that manifest in exploratory research. We hypothesised that ≥ 85% of original SEM research studies would report supported study hypotheses. Two independent assessors systematically identified, screened, included, and extracted study data from original research articles published between 1 January 2019 and 31 May 2019 in the British Journal of Sports Medicine, Sports Medicine, the American Journal of Sports Medicine, and the Journal of Orthopaedic & Sports Physical Therapy We extracted data relating to whether studies reported that the primary hypothesis was supported or rejected by the results. Study hypotheses, methodologies, and analysis plans were preregistered at the Open Science Framework. One hundred and twenty-nine original research studies reported at least one study hypothesis, of which 106 (82.2%) reported hypotheses that were supported by study results. Of 106 studies reporting that primary hypotheses were supported by study results, 75 (70.8%) studies reported that the primary hypothesis was fully supported by study results. The primary study hypothesis was partially supported by study results in 28 (26.4%) studies. We detail open science practices and resources that aim to safe-guard against QRPs that bely the credibility and replicability of original research findings.

Concussed athletes walk slower than non-concussed athletes during cognitive-motor dual-task assessments but not during single-task assessments 2 months after sports concussion: a systematic review and meta-analysis using individual participant data

Objectives

To determine whether individuals who sustained a sports concussion would exhibit persistent impairments in gait and quiet standing compared to non-injured controls during a dual-task assessment .

Design

Systematic review and meta-analysis using individual participant data (IPD).

Data sources

The search strategy was applied across seven electronic bibliographic and grey literature databases: MEDLINE, EMBASE, CINAHL, SportDISCUS, PsycINFO, PsycARTICLES and Web of Science, from database inception until June 2017.

Eligibility criteria for study selection

Studies were included if; individuals with a sports concussion and non-injured controls were included as participants; a steady-state walking or static postural balance task was used as the primary motor task; dual-task performance was assessed with the addition of a secondary cognitive task; spatiotemporal, kinematic or kinetic outcome variables were reported, and; included studies comprised an observational study design with case–control matching.

Data extraction and synthesis

Our review is reported in line with the Preferred Reporting Items for Systematic review and Meta-Analyses-IPD Statement. We implemented the Risk of Bias Assessment tool for Non-randomised Studies to undertake an outcome-level risk of bias assessment using a domain-based tool. Study-level data were synthesised in one of three tiers depending on the availability and quality of data: (1) homogeneous IPD; (2) heterogeneous IPD and (3) aggregate data for inclusion in a descriptive synthesis. IPD were aggregated using a ‘one-stage’, random-effects model.

Results

26 studies were included. IPD were available for 20 included studies. Consistently high and unclear risk of bias was identified for selection, detection, attrition, and reporting biases across studies. Individuals with a recent sports concussion walked with slower average walking speed (χ2=51.7; df=4; p<0.001; mean difference=0.06 m/s; 95% CI: 0.004 to 0.11) and greater frontal plane centre of mass displacement (χ2=10.3; df=4; p=0.036; mean difference −0.0039 m; 95% CI: −0.0075 to −0.0004) than controls when evaluated using a dual-task assessment up to 2 months following concussion.

Summary/conclusions

Our IPD evidence synthesis identifies that, when evaluated using a dual-task assessment, individuals who had incurred a sports concussion exhibited impairments in gait that persisted beyond reported standard clinical recovery timelines of 7–10 days. Dual-task assessment (with motion capture) may be a useful clinical assessment to evaluate recovery after sports concussion.

Protocol pre-registration

This systematic review was prospectively registered in PROSPERO CRD42017064861.

Magnetostatic twists in room-temperature skyrmions explored by nitrogen-vacancy center spin texture reconstruction

Magnetic skyrmions are two-dimensional non-collinear spin textures characterized by an integer topological number. Room-temperature skyrmions were recently found in magnetic multilayer stacks, where their stability was largely attributed to the interfacial Dzyaloshinskii-Moriya interaction. The strength of this interaction and its role in stabilizing the skyrmions is not yet well understood, and imaging of the full spin structure is needed to address this question. Here, we use a nitrogen-vacancy centre in diamond to measure a map of magnetic fields produced by a skyrmion in a magnetic multilayer under ambient conditions. We compute the manifold of candidate spin structures and select the physically meaningful solution. We find a Néel-type skyrmion whose chirality is not left-handed, contrary to preceding reports. We propose skyrmion tube-like structures whose chirality rotates through the film thickness. We show that NV magnetometry, combined with our analysis method, provides a unique tool to investigate this previously inaccessible phenomenon.

A six stage operational framework for individualising injury risk management in sport

Managing injury risk is important for maximising athlete availability and performance. Although athletes are inherently predisposed to musculoskeletal injuries by participating in sports, etiology models have illustrated how susceptibility is influenced by repeat interactions between the athlete (i.e. intrinsic factors) and environmental stimuli (i.e. extrinsic factors). Such models also reveal that the likelihood of an injury emerging across time is related to the interconnectedness of multiple factors cumulating in a pattern of either positive (i.e. increased fitness) or negative adaptation (i.e. injury).

The process of repeatedly exposing athletes to workloads in order to promote positive adaptations whilst minimising injury risk can be difficult to manage. Etiology models have highlighted that preventing injuries in sport, as opposed to reducing injury risk, is likely impossible given our inability to appreciate the interactions of the factors at play. Given these uncertainties, practitioners need to be able to design, deliver, and monitor risk management strategies that ensure a low susceptibility to injury is maintained during pursuits to enhance performance. The current article discusses previous etiology and injury prevention models before proposing a new operational framework.

Domain wall transformations and hopping in La(0.7)Sr(0.3)MnO(3) nanostructures imaged with high resolution x-ray magnetic microscopy

We investigate the effect of electric current pulse injection on domain walls in La(0.7)Sr(0.3)MnO(3) (LSMO) half-ring nanostructures by high resolution x-ray magnetic microscopy at room temperature. Due to the easily accessible Curie temperature of LSMO, we can employ reasonable current densities to induce the Joule heating necessary to observe effects such as hopping of the domain walls between different pinning sites and nucleation/annihilation events. Such effects are the dominant features close to the Curie temperature, while spin torque is found to play a small role close to room temperature. We are also able to observe thermally activated domain wall transformations and we find that, for the analyzed geometries, the vortex domain wall configuration is energetically favored, in agreement with micromagnetic simulations.

Breakdown of the x-ray resonant magnetic scattering signal during intense pulses of extreme ultraviolet free-electron-laser radiation

We present results of single-shot resonant magnetic scattering experiments of Co/Pt multilayer systems using 100 fs long ultraintense pulses from an extreme ultraviolet (XUV) free-electron laser. An x-ray-induced breakdown of the resonant magnetic scattering channel during the pulse duration is observed at fluences of 5  J/cm(2). Simultaneously, the speckle contrast of the high-fluence scattering pattern is significantly reduced. We performed simulations of the nonequilibrium evolution of the Co/Pt multilayer system during the XUV pulse duration. We find that the electronic state of the sample is strongly perturbed during the first few femtoseconds of exposure leading to an ultrafast quenching of the resonant magnetic scattering mechanism.

Ultrafast optical demagnetization manipulates nanoscale spin structure in domain walls

During ultrafast demagnetization of a magnetically ordered solid, angular momentum has to be transferred between the spins, electrons, and phonons in the system on femto- and picosecond timescales. Although the intrinsic spin-transfer mechanisms are intensely debated, additional extrinsic mechanisms arising due to nanoscale heterogeneity have only recently entered the discussion. Here we use femtosecond X-ray pulses from a free-electron laser to study thin film samples with magnetic domain patterns. We observe an infrared-pump-induced change of the spin structure within the domain walls on the sub-picosecond timescale. This domain-topography-dependent contribution connects the intrinsic demagnetization process in each domain with spin-transport processes across the domain walls, demonstrating the importance of spin-dependent electron transport between differently magnetized regions as an ultrafast demagnetization channel. This pathway exists independent from structural inhomogeneities such as chemical interfaces, and gives rise to an ultrafast spatially varying response to optical pump pulses.

Endstation for ultrafast magnetic scattering experiments at the free-electron laser in Hamburg

An endstation for pump-probe small-angle X-ray scattering (SAXS) experiments at the free-electron laser in Hamburg (FLASH) is presented. The endstation houses a solid-state absorber, optical incoupling for pump-probe experiments, time zero measurement, sample chamber, and detection unit. It can be used at all FLASH beamlines in the whole photon energy range offered by FLASH. The capabilities of the setup are demonstrated by showing the results of resonant magnetic SAXS measurements on cobalt-platinum multilayer samples grown on freestanding Si(3)N(4) membranes and pump-laser-induced grid structures in multilayer samples.

Holographically aided iterative phase retrieval

Fourier transform holography (FTH) is a noise-resistant imaging technique which allows for nanometer spatial resolution x-ray imaging, where the inclusion of a small reference scattering object provides the otherwise missing phase information. With FTH, one normally requires a considerable distance between the sample and the reference to ensure spatial separation of the reconstruction and its autocorrelation. We demonstrate however that this requirement can be omitted at the small cost of iteratively separating the reconstruction and autocorrelation. In doing so, the photon efficiency of FTH can be increased due to a smaller illumination area, and we show how the presence of the reference prevents the non-uniqueness problems often encountered with plane-wave iterative phase retrieval. The method was tested on a cobalt/platinum multilayer exhibiting out of plane magnetized domains, where the magnetic circular dichroism effect was used to image the magnetic domains at the cobalt L₃-edge at 780eV.

Photooxygenation of the helimers of (-)-isocolchicine: regio- and facial selectivity of the [4 + 2] cycloaddition with singlet oxygen and surprising endoperoxide transformations

Photooxygenation of the helimeric mixture of (-)-(M,7S)/(P,7S)-isocolchicine (6) with the superdienophile singlet oxygen has been studied. Cycloaddition occurred with high regioselectivity at the 7a,11-positions of the alkaloid and predominantly at the diene face anti to the amidic substituent at the stereogenic center C-7, leading to two endoperoxides 7 (syn) and 8 (anti) with an 1:7 ratio. The structure of the minor product 7 was established by X-ray analysis. Investigation of the triethylamine induced transformation of the predominant endoperoxide 8 furnished a mixture of two isomers (M,7S)-10a/(M,7S)-10b in a 2:1 ratio possibly with constitutional interconversion and with (M,7S)-9 as plausible intermediate. Treatment of this mixture with silica gel/ethyl acetate at ambient temperature surprisingly led to an atropenantiomerically pure colchicinoid (M,7S)-12 characterized by an eightmembered oxocine B-ring, the structure and absolute configuration of which could be determined by X-ray analysis. For the unprecedented formation of the novel colchicinoid (M,7S)-12 a plausible reaction pathway is suggested, involving a complete transfer of the (M) helical asymmetry of the intermediate (M)-11 into (S) asymmetry of the newly formed carbon center of (M,7S)-12. Prerequisite for such a scenario is the configurational stability of the intermediate pseudobiaryl (M)-11, under the conditions employed, allowing to transmit the axial chirality onto the chiral center of the product (M,7S)-12.

[Diagnosis of spondylitis by MR tomography]

The results of MR tomography in 13 patients with specific and nonspecific spondylitis are reported. There were characteristic changes in signal intensity and in the configuration of the vertebral bodies and the intervertebral discs. The extent of intraspinal stenosis can be demonstrated accurately by MR. Paravertebral abscesses can be shown accurately and their position can be clarified by means of multiplanar sections. The early diagnosis of spondylitis by MR tomography is discussed.