X-ray scattering studies of nanostructured patterned arrays

X-ray resonant magnetic scattering (XRMS) has been used to investigate patterned arrays created using electron beam lithography. Diffraction from the repeating pattern has been measured close to the origin of reciprocal space. The impact of the spatial coherence of x-ray radiation is discussed in the context of reproducing rocking curves at various azimuthal rotation angles from patterned arrays of multilayered circular and elliptical islands. We show how traditional diffraction theory implicitly assumes a high coherence which has to be adapted to account for both the finite number of elements coherently illuminated by the beam and the specific experimental configurations used. This allowed a generic theoretic framework to be developed to describe the scattering from patterned arrays. The derived computational foundation is formulated in a specifically developed simulation framework, of modular code design allowing for efficient data processing, simulation, and fitting. Utilising XRMS, and fitting the charge and magnetic scattering signals simultaneously, allowed quantitative fits to the in-plane diffraction data contained in rocking curves and the specular reflectivity from a patterned array of disk-like circular islands. The islands were spatially resolved into a three-dimensional chemical and magnetic profile revealing a core-shell structure. This structure is likely to be as a result from oxidation, affecting the surface of the islands. Simple models assuming at disks could not reproduce the data and failed to account for the modulations in the intensity of the Bragg peaks, often by several orders of magnitude. A spatial model in which the islands were domed was developed in order to accurately reproduce the scattering data. The doming is likely to occur as a result of the prepatterning process used in sample production. The limited number of diffraction orders limits the precision of the modelling and we show how a grazing incidence small angle scattering (GISAXS) geometry can be exploited to easily and quickly obtain diffraction data over many orders, allowing a straightforward characterisation of the sample. The alternative experimental geometry is tested under laboratory conditions in which the coherence could be varied. Finally, XRMS measurements were also used in order to investigate the intra-island magnetic structure. Due to the shape anisotropy, magnetic vortex states form in the disk-like patterns. Fits of the magnetic hysteresis derived from the magnetic signal allow the structure of a magnetic vortex to be determined directly and indicate elliptical deformation of an magnetic vortex as it approaches the edge of the cylindrical host element

Magnetic order and energy-scale hierarchy in artificial spin ice

In order to explain and predict the properties of many physical systems, it is essential to understand the interplay of different energy-scales. Here we present investigations of the magnetic order in thermalised artificial spin ice structures, with different activation energies of the interacting Ising-like elements. We image the thermally equilibrated magnetic states of the nano-structures using synchrotron-based magnetic microscopy. By comparing results obtained from structures with one or two different activation energies, we demonstrate a clear impact on the resulting magnetic order. The differences are obtained by the analysis of the magnetic spin structure factors, in which the role of the activation energies is manifested by distinct short-range order. This demonstrates that artificial spin systems can serve as model systems, allowing the definition of energy-scales by geometrical design and providing the backdrop for understanding their interplay.Comment: 8 pages, 5 figures (+ supplementary 6 pages, 4 figures

Nanotomography endstation at the P05 beamline : Status and perspectives

The Imaging Beamline IBL/P05 at the DESY storage ring PETRA III, operated by the Helmholtz-Zentrum Geesthacht, has two dedicated endstations optimized for micro- and nanotomography experiments [1-3]. Here we present the status of the nanotomography endstation, highlight the latest instrumentation upgrades and present first experimental results. In particular in materials science, where structures with ceramics or metallic materials are of interest, X-ray energies of 15 keV and above are required even for sample sizes of several 10 μm in diameter. The P05 imaging beamline is dedicated to materials science and is designed to allow for imaging applications with X-ray energies of 10 to 50 keV. In addition to the full field X-ray microscopy setup, the layout of the nanotomography endstation allows switching to cone-beam configuration. Kinematics for X-ray optics like compound refractive lenses (CRLs), Fresnel zone plates (FZP) or beam-shaping optics are implemented and the installation of a Kirkpatrick Baez-mirror (KB mirror) system is foreseen at a later stage of the beamline development. Altogether this leads to a high flexibility of the nanotomography setup such that the instrument can be tailored to the specific experimental requirements of a range of sample systems

Prediction Models for Clinical Outcome After a Carotid Revascularization Procedure.

Background and Purpose- Prediction models may help physicians to stratify patients with high and low risk for periprocedural complications or long-term stroke risk after carotid artery stenting or carotid endarterectomy. We aimed to evaluate external performance of previously published prediction models for short- and long-term outcome after carotid revascularization in patients with symptomatic carotid artery stenosis. Methods- From a literature review, we selected all prediction models that used only readily available patient characteristics known before procedure initiation. Follow-up data from 2184 carotid artery stenting and 2261 carotid endarterectomy patients from 4 randomized trials (EVA-3S [Endarterectomy Versus Angioplasty in Patients With Symptomatic Severe Carotid Stenosis], SPACE [Stent-Protected Angioplasty Versus Carotid Endarterectomy], ICSS [International Carotid Stenting Study], and CREST [Carotid Revascularization Endarterectomy Versus Stenting Trial]) were used to validate 23 short-term outcome models to estimate stroke or death risk ≤30 days after the procedure and the original outcome measure for which the model was developed. Additionally, we validated 7 long-term outcome models for the original outcome measure. Predictive performance of the models was assessed with C statistics and calibration plots. Results- Stroke or death ≤30 days after the procedure occurred in 158 (7.2%) patients after carotid artery stenting and in 84 (3.7%) patients after carotid endarterectomy. Most models for short-term outcome after carotid artery stenting (n=4) or carotid endarterectomy (n=19) had poor discriminative performance (C statistics ranging from 0.49-0.64) and poor calibration with small absolute risk differences between the lowest and highest risk groups and overestimation of risk in the highest risk groups. Long-term outcome models (n=7) had a slightly better performance with C statistics ranging from 0.59 to 0.67 and reasonable calibration. Conclusions- Current models did not reliably predict outcome after carotid revascularization in a trial population of patients with symptomatic carotid stenosis. In particular, prediction of short-term outcome seemed to be difficult. Further external validation of existing prediction models or development of new prediction models is needed before such models can be used to support treatment decisions in individual patients

Pushing the temporal resolution in absorption and Zernike phase contrast nanotomography: Enabling fast in situ experiments

Hard X-ray nanotomography enables 3D investigations of a wide range of samples with high resolution (<100 nm) with both synchrotron-based and laboratory-based setups. However, the advantage of synchrotron-based setups is the high flux, enabling time resolution, which cannot be achieved at laboratory sources. Here, the nanotomography setup at the imaging beamline P05 at PETRA III is presented, which offers high time resolution not only in absorption but for the first time also in Zernike phase contrast. Two test samples are used to evaluate the image quality in both contrast modalities based on the quantitative analysis of contrast-to-noise ratio (CNR) and spatial resolution. High-quality scans can be recorded in 15 min and fast scans down to 3 min are also possible without significant loss of image quality. At scan times well below 3 min, the CNR values decrease significantly and classical image-filtering techniques reach their limitation. A machine-learning approach shows promising results, enabling acquisition of a full tomography in only 6 s. Overall, the transmission X-ray microscopy instrument offers high temporal resolution in absorption and Zernike phase contrast, enabling in situ experiments at the beamline

Long-term outcomes of stenting and endarterectomy for symptomatic carotid stenosis: a preplanned pooled analysis of individual patient data.

BACKGROUND: The risk of periprocedural stroke or death is higher after carotid artery stenting (CAS) than carotid endarterectomy (CEA) for the treatment of symptomatic carotid stenosis. However, long-term outcomes have not been sufficiently assessed. We sought to combine individual patient-level data from the four major randomised controlled trials of CAS versus CEA for the treatment of symptomatic carotid stenosis to assess long-term outcomes. METHODS: We did a pooled analysis of individual patient-level data, acquired from the four largest randomised controlled trials assessing the relative efficacy of CAS and CEA for treatment of symptomatic carotid stenosis (Endarterectomy versus Angioplasty in Patients with Symptomatic Severe Carotid Stenosis trial, Stent-Protected Percutaneous Angioplasty of the Carotid Artery versus Endarterectomy trial, International Carotid Stenting Study, and Carotid Revascularization Endarterectomy versus Stenting Trial). The risk of ipsilateral stroke was assessed between 121 days and 1, 3, 5, 7, 9, and 10 years after randomisation. The primary outcome was the composite risk of stroke or death within 120 days after randomisation (periprocedural risk) or subsequent ipsilateral stroke up to 10 years after randomisation (postprocedural risk). Analyses were intention-to-treat, with the risk of events calculated using Kaplan-Meier methods and Cox proportional hazards analysis with adjustment for trial. FINDINGS: In the four trials included, 4775 patients were randomly assigned, of whom a total of 4754 (99·6%) patients were followed up for a maximum of 12·4 years. 21 (0·4%) patients immediately withdrew consent after randomisation and were excluded. Median length of follow-up across the studies ranged from 2·0 to 6·9 years. 129 periprocedural and 55 postprocedural outcome events occurred in patients allocated CEA, and 206 and 57 for those allocated CAS. After the periprocedural period, the annual rates of ipsilateral stroke per person-year were similar for the two treatments: 0·60% (95% CI 0·46-0·79) for CEA and 0·64% (0·49-0·83) for CAS. Nonetheless, the periprocedural and postprocedural risks combined favoured CEA, with treatment differences at 1, 3, 5, 7, and 9 years all ranging between 2·8% (1·1-4·4) and 4·1% (2·0-6·3). INTERPRETATION: Outcomes in the postprocedural period after CAS and CEA were similar, suggesting robust clinical durability for both treatments. Although long-term outcomes (periprocedural and postprocedural risks combined) continue to favour CEA, the similarity of the postprocedural rates suggest that improvements in the periprocedural safety of CAS could provide similar outcomes of the two procedures in the future. FUNDING: None

Body mass index and outcome after revascularization for symptomatic carotid artery stenosis.

OBJECTIVE: To determine whether the obesity paradox exists in patients who undergo carotid artery stenting (CAS) or carotid endarterectomy (CEA) for symptomatic carotid artery stenosis. METHODS: We combined individual patient data from 2 randomized trials (Endarterectomy vs Angioplasty in Patients with Symptomatic Severe Carotid Stenosis and Stent-Protected Angioplasty vs Carotid Endarterectomy) and 3 centers in a third trial (International Carotid Stenting Study). Baseline body mass index (BMI) was available for 1,969 patients and classified into 4 groups: 120 days after randomization). This outcome was compared between different BMI strata in CAS and CEA patients separately, and in the total group. We performed intention-to-treat multivariable Cox regression analyses. RESULTS: Median follow-up was 2.0 years. Stroke or death occurred in 159 patients in the periprocedural (cumulative risk 8.1%) and in 270 patients in the postprocedural period (rate 4.8/100 person-years). BMI did not affect periprocedural risk of stroke or death for patients assigned to CAS (ptrend = 0.39) or CEA (ptrend = 0.77) or for the total group (ptrend = 0.48). Within the total group, patients with BMI 25-<30 had lower postprocedural risk of stroke or death than patients with BMI 20-<25 (BMI 25-<30 vs BMI 20-<25; hazard ratio 0.72; 95% confidence interval 0.55-0.94). CONCLUSIONS: BMI is not associated with periprocedural risk of stroke or death; however, BMI 25-<30 is associated with lower postprocedural risk than BMI 20-<25. These observations were similar for CAS and CEA

Safety of Carotid Revascularization in Patients With a History of Coronary Heart Disease.

Background and Purpose- We investigated whether procedural stroke or death risk of carotid artery stenting (CAS) compared with carotid endarterectomy (CEA) is different in patients with and without history of coronary heart disease (CHD) and whether the treatment-specific impact of age differs. Methods- We combined individual patient data of 4754 patients with symptomatic carotid stenosis from 4 randomized trials (EVA-3S [Endarterectomy Versus Angioplasty in Patients With Symptomatic Severe Carotid Stenosis], SPACE [Stent-Protected Angioplasty Versus Carotid Endarterectomy], ICSS [International Carotid Stenting Study], and CREST [Carotid Revascularization Endarterectomy Versus Stenting Trial]). Procedural risk was defined as any stroke or death ≤30 days after treatment. We compared procedural risk between both treatments with Cox regression analysis, stratified by history of CHD and age (<70, 70-74, ≥75 years). History of CHD included myocardial infarction, angina, or coronary revascularization. Results- One thousand two hundred ninety-three (28%) patients had history of CHD. Procedural stroke or death risk was higher in patients with history of CHD. Procedural risk in patients treated with CAS compared with CEA was consistent in patients with history of CHD (8.3% versus 4.6%; hazard ratio [HR], 1.96; 95% CI, 0.67-5.73) and in those without (6.9% versus 3.6%; HR, 1.93; 95% CI, 1.40-2.65; Pinteraction=0.89). In patients with history of CHD, procedural risk was significantly higher after CAS compared with CEA in patients aged ≥75 (CAS-to-CEA HR, 2.78; 95% CI, 1.32-5.85), but not in patients aged <70 (HR, 1.71; 95% CI, 0.79-3.71) and 70 to 74 years (HR, 1.09; 95% CI, 0.45-2.65). In contrast, in patients without history of CHD, procedural risk after CAS was higher in patients aged 70 to 74 (HR, 3.62; 95% CI, 1.80-7.29) and ≥75 years (HR, 2.64; 95% CI, 1.52-4.59), but equal in patients aged <70 years (HR, 1.05; 95% CI, 0.63-1.73; 3-way Pinteraction=0.09). Conclusions- History of CHD does not modify procedural stroke or death risk of CAS compared with CEA. CAS might be as safe as CEA in patients with history of CHD aged <75 years, whereas for patients without history of CHD, risk after CAS compared with CEA was only equal in those aged <70 years

Gelingendes Leben - Krise als Chance für Person & Gesellschaft. Band II

• Peter Antes, Rel.wiss. • Petra Bahr, Theol. / Journ. • Matthias Beck Med./JS, AT • Gottfried Biewer, Bildungswiss., AT • Aladin El-Mafaalani, Pol.wiss.• Johannes Eurich, Diak.wiss. • Mario Feigel, Med. CH • Heike Gramkow, Manag.Dir. • Heinrich Greving, Heilpäd. • Udo Hahn, Theol.• Maria-C. Hallwachs, Stud., Beratg. schon betroffen • Walter Hirche, Min. a.D./Präs. Dt. UNESCO • Wolfgang Jantzen †, Soz. • Jochen-C. Kaiser, Hist. • Karl-J. Kemmelmeyer, Präs. Musikrat • Hermes Kick, Med.-Ethik • Waldemar Kippes Redemptorist JN • Ferdinand Klein, SoPäd., SK • Berthold Krüger, bpb • Christian Larsen, Arzt, CH • Ulrich Lilie Präs. Diak.W • Christian Lindmeier, SoPäd., DGfE • Ralf Meister, Bischof • Bertolt Meyer, Org.- u. Wirtschaftspsych, schon betroffen, CH • Peter Neher, Präs. Caritas • Ekkehard Nuissl, Dir. Dt. Inst. EB, DIE • Ulrich Pohl, Vorst. Bethel • Hartmann Römer, Physiker • David Roth, Lt. Hospiz • Hartmut Schlegel SoPäd. • Joachim Schoss, Unternehmer, schon betroffen, CH • Walter Surböck Med., AT• Karl-H. Steinmetz, Trad. Europ. Med., AT • Rudolf Tippelt, Bildg. Forschg. • Inge Wasserberg, Inklu.Beratg. • Walter Thirring †, Phys. CERN, C

Hard X‐ray full‐field nanoimaging using a direct photon‐counting detector

Full‐field X‐ray nanoimaging is a widely used tool in a broad range of scientific areas. In particular, for low‐absorbing biological or medical samples, phase contrast methods have to be considered. Three well established phase contrast methods at the nanoscale are transmission X‐ray microscopy with Zernike phase contrast, near‐field holography and near‐field ptychography. The high spatial resolution, however, often comes with the drawback of a lower signal‐to‐noise ratio and significantly longer scan times, compared with microimaging. In order to tackle these challenges a single‐photon‐counting detector has been implemented at the nanoimaging endstation of the beamline P05 at PETRA III (DESY, Hamburg) operated by Helmholtz‐Zentrum Hereon. Thanks to the long sample‐to‐detector distance available, spatial resolutions of below 100 nm were reached in all three presented nanoimaging techniques. This work shows that a single‐photon‐counting detector in combination with a long sample‐to‐detector distance allows one to increase the time resolution for in situ nanoimaging, while keeping a high signal‐to‐noise level.A direct photon‐counting detector was used for different nanoimaging phase contrast techniques, increasing the temporal resolution