Filamentation of a relativistic proton bunch in plasma.

We show in experiments that a long, underdense, relativistic proton bunch propagating in plasma undergoes the oblique instability, which we observe as filamentation. We determine a threshold value for the ratio between the bunch transverse size and plasma skin depth for the instability to occur. At the threshold, the outcome of the experiment alternates between filamentation and self-modulation instability (evidenced by longitudinal modulation into microbunches). Time-resolved images of the bunch density distribution reveal that filamentation grows to an observable level late along the bunch, confirming the spatiotemporal nature of the instability. We provide a rough estimate of the amplitude of the magnetic field generated in the plasma by the instability and show that the associated magnetic energy increases with plasma density.

Hosing of a Long Relativistic Particle Bunch in Plasma.

Experimental results show that hosing of a long particle bunch in plasma can be induced by wakefields driven by a short, misaligned preceding bunch. Hosing develops in the plane of misalignment, self-modulation in the perpendicular plane, at frequencies close to the plasma electron frequency, and are reproducible. Development of hosing depends on misalignment direction, its growth on misalignment extent and on proton bunch charge. Results have the main characteristics of a theoretical model, are relevant to other plasma-based accelerators and represent the first characterization of hosing.

FOCUS: fast Monte Carlo approach to coherence of undulator sources.

FOCUS (Fast Monte CarlO approach to Coherence of Undulator Sources) is a new GPU-based simulation code to compute the transverse coherence of undulator radiation from ultra-relativistic electrons. The core structure of the code, which is written in the language C++ accelerated with CUDA, combines an analytical description of the emitted electric fields and massively parallel computations on GPUs. The combination is rigorously justified by a statistical description of synchrotron radiation based on a Fourier optics approach. FOCUS is validated by direct comparison with multi-electron Synchrotron Radiation Workshop (SRW) simulations, evidencing a reduction in computation times by up to five orders of magnitude on a consumer laptop. FOCUS is then applied to systematically study the transverse coherence in typical third- and fourth-generation facilities, highlighting peculiar features of undulator sources close to the diffraction limit. FOCUS is aimed at fast evaluation of the transverse coherence of undulator radiation as a function of the electron beam parameters, to support and help prepare more advanced and detailed numerical simulations with traditional codes like SRW.

Transition between Instability and Seeded Self-Modulation of a Relativistic Particle Bunch in Plasma.

We use a relativistic ionization front to provide various initial transverse wakefield amplitudes for the self-modulation of a long proton bunch in plasma. We show experimentally that, with sufficient initial amplitude [≥(4.1±0.4) MV/m], the phase of the modulation along the bunch is reproducible from event to event, with 3%-7% (of 2π) rms variations all along the bunch. The phase is not reproducible for lower initial amplitudes. We observe the transition between these two regimes. Phase reproducibility is essential for deterministic external injection of particles to be accelerated.

Preoperative nutrition forseverely malnourished patients in digestive surgery: A retrospective study.

INTRODUCTION: Malnutrition increases postoperative morbidity and mortality. The objective of this study was to evaluate preoperative refeeding in malnourished patients at risk of refeeding syndrome (RS). METHODOLOGY: A retrospective study, conducted between June 2016 and January 2017, reported to the CNIL, compared two groups of malnourished patients: a group of refeeding patients (RP) and a group of non-refeeding patients (NRP). The inclusion criteria were weight loss of more than 10% or albuminemia less than 35g/L and RS risk factor. The primary endpoint was postoperative morbidity. The secondary endpoints were weight change and serum albumin over 6 months. RESULTS: Seventy-three patients (30 RP and 43 NRP) were included. At the time of initial management, median weight loss was 18% [1-71], while albuminemia was 26g/L [13-40] in the RP group and 32.5g/L [32-48] in the NRP group (P=0.01). The overall postoperative morbidity rate was 88% (83% RP versus 90% NRP, P=0.47), and there was no significant difference between the 2 groups. The rate of anastomotic complications was 4% for RP versus 26% for NRP (P=0.03) after exclusion of liver surgery. Medium-term weight loss tended to be greater in RP (P=0.7). Nutritional support was continued until the third postoperative month in 13% of RPs vs. no NRPs (P=0.0002). CONCLUSION: After preoperative renutrition, we did not observe a decrease in morbidity but rather a decrease in the rate of anastomotic complications in favor of the RP group. This study underscores the middle-term importance of nutritional management in view of preserving the benefits of preoperative renutrition.

[TAVI in women, very encouraging results]. / TAVI chez les femmes, des résultats très encourageants.

The population of elderly patients comprises a high percentage of women. This population is more vulnerable due to the presence of numerous comorbidities and is, therefore, particularly exposed to the risk of aortic valve degeneration, resulting in aortic valve stenosis whose symptoms are predictors of poor short-term outcomes. In the presence of symptomatic aortic stenosis, the recommended therapeutic option in this vulnerable population is the implementation of transcatheter aortic valve implantation, preferably via the femoral route. The outcomes of this procedure are better in women than in men despite a more frequent occurrence of vascular, bleeding and cerebral complications. Several hypotheses have been reported in the literature regarding the reasons for such differences. Among other reasons, it is likely that in female patients, the myocardium adjusts better to the occurrence of aortic stenosis and that recovery after valve treatment is also more optimal. Another explanation is the higher frequency of coronary artery disease in this older population. This has a considerable impact on the outcome even when coronary lesions are treated prior to valve implantation. There is still room for improvement and progress can be achieved by further reducing the size of the equipment used in order to decrease the diameter of the vascular access, and by continuing to simplify TAVI procedures. Less invasive techniques should result in decreased complication rates. In addition, dedicated studies should allow us to further improve our practice in this growing population of vulnerable patients.

[TAVI simplification: A focus]. / Simplification des procédures TAVI : mise au point.

After a first procedure carried out in 2002 by Pr Cribier's, Transcatheter Aortic Valve Replacement or TAVR revolutionized the management of aortic stenosis with a constant increase in the number of procedures performed worldwide. Experience of operators and teams and evolution of the technique has been accompanied by a drastic reduction in complications in patients at lower surgical risk. In parallel, the procedure was considerably simplified, carried out more and more under local anesthesia, with percutaneous femoral approach, secondary radial approach, prosthesis implantation without predilatation, rapid pacing on left ventricle wire and early discharge. Thus, the "simplified" TAVR adopted in most centers nowadays is a real revolution of the technique. However, simplified TAVR must be accompanied upstream by a rigorous selection of patients who can benefit from a minimalist procedure in order to guarantee its safety.

Proton-driven plasma wakefield acceleration in AWAKE.

In this article, we briefly summarize the experiments performed during the first run of the Advanced Wakefield Experiment, AWAKE, at CERN (European Organization for Nuclear Research). The final goal of AWAKE Run 1 (2013-2018) was to demonstrate that 10-20 MeV electrons can be accelerated to GeV energies in a plasma wakefield driven by a highly relativistic self-modulated proton bunch. We describe the experiment, outline the measurement concept and present first results. Last, we outline our plans for the future. This article is part of the Theo Murphy meeting issue 'Directions in particle beam-driven plasma wakefield acceleration'.

A surface spectroscopy study of a Pseudomonas fluorescens biofilm in the presence of an immobilized air bubble.

A linear spectral mapping technique was applied to monitor the growth of biomolecular absorption bands at the bio-interface of a nascent Pseudomonas fluorescens biofilm during and after interaction with a surface-adhered air bubble. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectra were obtained in different locations in a microchannel with adequate spatial and temporal resolution to study the effect of a static bubble on the evolution of protein and lipid signals at the ATR crystal surface. The results reveal that the presence of a bubble during the lag phase modified levels of extracellular lipids and affected a surface restructuring process, many hours after the bubble's disappearance.

Kidney cortex segmentation in 2D CT with U-Nets ensemble aggregation.

PURPOSE: This work presents our contribution to one of the data challenges organized by the French Radiology Society during the Journées Francophones de Radiologie. This challenge consisted in segmenting the kidney cortex from coronal computed tomography (CT) images, cropped around the cortex. MATERIALS AND METHODS: We chose to train an ensemble of fully-convolutional networks and to aggregate their prediction at test time to perform the segmentation. An image database was made available in 3 batches. A first training batch of 250 images with segmentation masks was provided by the challenge organizers one month before the conference. An additional training batch of 247 pairs was shared when the conference began. Participants were ranked using a Dice score. RESULTS: The segmentation results of our algorithm match the renal cortex with a good precision. Our strategy yielded a Dice score of 0.867, ranking us first in the data challenge. CONCLUSION: The proposed solution provides robust and accurate automatic segmentations of the renal cortex in CT images although the precision of the provided reference segmentations seemed to set a low upper bound on the numerical performance. However, this process should be applied in 3D to quantify the renal cortex volume, which would require a marked labelling effort to train the networks.

Automatic knee meniscus tear detection and orientation classification with Mask-RCNN.

PURPOSE: This work presents our contribution to a data challenge organized by the French Radiology Society during the Journées Francophones de Radiologie in October 2018. This challenge consisted in classifying MR images of the knee with respect to the presence of tears in the knee menisci, on meniscal tear location, and meniscal tear orientation. MATERIALS AND METHODS: We trained a mask region-based convolutional neural network (R-CNN) to explicitly localize normal and torn menisci, made it more robust with ensemble aggregation, and cascaded it into a shallow ConvNet to classify the orientation of the tear. RESULTS: Our approach predicted accurately tears in the database provided for the challenge. This strategy yielded a weighted AUC score of 0.906 for all three tasks, ranking first in this challenge. CONCLUSION: The extension of the database or the use of 3D data could contribute to further improve the performances especially for non-typical cases of extensively damaged menisci or multiple tears.

Position paper of French Interventional Group (GACI) for TAVI in France in 2018.

Aortic stenosis is a frequent disease in the elderly. Its prevalence is 0.4% with a sharp increase after the age of 65, and its outcome is very poor when the patient becomes symptomatic. The interventional procedure known as TAVI (trans-catheter aortic valve implantation), which was developed in France and carried out for the first time in Rouen by Prof. Alain Cribier and his team in 2002, has proven to be a valid alternative to surgical aortic valve replacement. At first, this technique was shown to be efficient in patients with contra-indications to surgical treatment or deemed to be at high surgical risk. Given the very promising outcomes achieved as a result of close heart team collaboration, appropriate patient selection, simplified procedures and reduced complication rates, transfemoral (TF) TAVI is now preferred in symptomatic intermediate risk patients>75 years old according to the latest ESC guidelines. In 2017, in France, TAVI is currently performed in 50 centers with on-site cardiac surgery. The 2016 TAVI outcomes recorded in the French national TAVI registry (France TAVI) are very encouraging and show that for 7133 patients treated (age 83.4±7 years, logistic Euroscore 14%), 87% of whom via the TF approach, cross-over to surgery was very low (0.5%) with a 3.0% in-hospital mortality rate. The substantial increase in TAVI indications and the improvement of its outcomes may in the near future call for a reconsideration of the number of high volume centers authorized to carry out this technique.

Direct Observation of Incoherent Cherenkov Diffraction Radiation in the Visible Range.

We report on the observation of incoherent Cherenkov radiation emitted by a 5.3 GeV positron beam circulating in the Cornell electron-positron storage ring as the beam passes in the close vicinity of the surface of a fused silica radiator (i.e., at a distance larger than 0.8 mm). The shape of the radiator was designed in order to send the Cherenkov photons towards the detector, consisting of a compact optical system equipped with an intensified camera. The optical system allows both the measurements of 2D images and angular distribution including polarization study. The corresponding light intensity has been measured as a function of the distance between the beam and the surface of the radiator and has shown a good agreement with theoretical predictions. For highly relativistic particles, a large amount of incoherent radiation is produced in a wide spectral range. A light yield of 0.8×10^{-3} photon per particle per turn has been measured at a wavelength of 600±10 nm in a 2 cm long radiator and for an impact parameter of 1 mm. This will find applications in accelerators as noninvasive beam diagnostics for both leptons and hadrons.

Experimental Observation of "Shadowing" in Optical Transition Radiation.

We report the observation of shadowing between two optical transition radiation (OTR) sources from a 205 MeV electron beam. The total optical intensity is measured as a function of the distance d between the sources, covering the range 0

Novel integrated 3D multidetector computed tomography and fluoroscopy fusion for left atrial appendage occlusion procedures.

OBJECTIVES: This report demonstrates the application and feasibility of novel 3D-MDCT real-time fusion technology with fluoroscopy, for left atrial appendage (LAA) occlusion procedures. BACKGROUND: A successful LAA occlusion procedure relies on multiple imaging modalities, including TEE or 3D-MDCT, and fluoroscopy. Effectively integrating these imaging modalities may improve implantation safety and success. To our knowledge this technique has not been previously described for LAA occlusions. METHODS: This observational study compared clinical and procedural parameters for procedures performed with or without fusion integration. All patients had a pre-procedural 3D-MDCT for LAA measurements, along with 3D analyses of LAA morphology and surrounding structures. Using the image fusion software (Valve ASSIST 2, GE Healthcare, UK), landmarks were identified on fluoroscopy, and MDCT LAA anatomy outlines were then projected onto the real-time fluoroscopy image during the procedure, to guide all steps of the intervention. RESULTS: A total of 57 patients underwent LAA occlusion, with 16 performed using fusion software. In comparison to the pre-fusion group, reductions in contrast volume (21.0 ± 11.7 vs. 95.9 ± 80.5 ml, P < 0.001), procedure time (63.0 ± 22.0 vs. 87.3 ± 43.0 min, P = 0.01), and fluoroscopy time (6.2 vs. 8.3 min, P = 0.03) were observed. Incomplete sealing (0 vs. 14.6%, P = 0.16) and device deployment success (100 vs. 92.7%, P = 0.17) were not significantly different. CONCLUSIONS: The addition of this novel fusion technology is safe and feasible. To optimize LAA procedural success, fusion integration may offer a promising addition, or alternative, to current imaging modalities. © 2017 Wiley Periodicals, Inc.

A quantitative analysis of the supercontraction-induced molecular disorientation of major ampullate spider silk.

Spider silks exhibit remarkable properties, among which the so-called supercontraction, a physical phenomenon by which fibers undergo a longitudinal shrinkage and a radial swelling when exposed to water. The process is marked by a significant decrease in chain orientation resulting from plasticisation of the amorphous phase. Despite several studies that determined the Hermans orientation function, more quantitative data are required to be able to describe theoretically the macroscopic water-induced shrinkage from molecular reorganization. Here, we have examined the supercontraction of the major ampullate silk single fibers of Nephila clavipes (Nc) and Araneus diadematus (Ad) using polarized Raman spectromicroscopy. We determined the order parameters, the orientation distribution and the secondary structure content. Our data suggest that supercontraction induces a slight increase in ß-sheet content, consistently with previous works. The ß-sheet orientation is slightly affected by supercontraction compared to that of the amorphous phase, which becomes almost isotropic with shrinkage. Despite an initially lower orientation level, the Ad fiber shows a larger orientation decrease than Nc, consistently with its higher shrinkage amplitude. Although they share similar trends, absolute values of the orientation parameters from this work differ from those found in the literature. We took advantage of having determined the distribution of orientation to estimate the amplitude of shrinkage from changes in macromolecular size resulting from molecular disorientation. Our calculations show that more realistic models are needed to correlate molecular reorientation/refolding to macroscopic shrinkage. This work also underlines that more accurate data relative to molecular orientation are necessary.

Sex-based differences in outcomes with bivalirudin or unfractionated heparin for transcatheter aortic valve replacement: Results from the BRAVO-3 randomized trial.

BACKGROUND: Women comprise almost 50% of patients undergoing transcatheter aortic valve replacement (TAVR) and previous studies have indicated higher rates of procedural complications and bleeding in women compared to men. It is unknown whether men and women demonstrate a differential response to bivalirudin versus unfractionated heparin (UFH) in TAVR. We sought to evaluate outcomes by sex and type of anticoagulant from the Bivalirudin Versus Heparin Anticoagulation in Transcatheter Aortic Valve Replacement (BRAVO-3) trial of transfemoral TAVR. METHODS: BRAVO-3 was a randomized multicenter trial comparing transfemoral TAVR with bivalirudin versus UFH (31 centers, n = 802). The primary endpoint was 48 h major bleeding defined as Bleeding Academic Research Consortium (BARC) type ≥3b. Major adverse cardiovascular events (MACE) were a composite of 30-day death, myocardial infarction, or stroke. Net adverse cardiovascular events (NACE) were a composite of BARC ≥3b bleeding or 30-day MACE. We examined the outcomes in men and women. RESULTS: The total cohort included 49% women (n = 391, 195 received bivalirudin and 196 UFH) and 51% men (n = 411, 209 received bivalirudin and 202 UFH). Women were older than men with fewer comorbidities including coronary artery disease, atrial fibrillation, diabetes but similar EuroSCORE I. Women received smaller sheath and device sizes compared with men without differences in the use of vascular closure devices. At 48-hr post-TAVR there was no difference in bleeding or vascular complications in women compared to men. The use of bivalirudin did not result in significantly lower bleeding at 48 hr or 30-days compared to UFH. CONCLUSIONS: There was no difference in early outcomes with bivalirudin versus UFH in men or women undergoing contemporary TAVR. © 2016 Wiley Periodicals, Inc.

[Transfemoral TAVI procedure in women: Minimally-invasive technique]. / Procédure de TAVI par voie fémorale chez la femme : technique minimaliste.

Demographic data point to a substantial proportion of women in the population of elderly patients with an increasing prevalence of aortic stenosis. Implantation of an aortic bioprosthesis via an endovascular approach known as Transcatheter aortic valve implantation (TAVI) in patients presenting with a symptomatic tight aortic stenosis (severe aortic stenosis) (AS) is an alternative therapeutic option to surgical aortic valve replacement in patients at high surgical risk or ineligible for surgery. The literature has shown that this technique seems to be particularly beneficial in female patients. In the Partner A trial, the 1-year mortality rate was significantly lower in women compared to their male counterparts. Other data revealed that although women have a higher risk of experiencing periprocedural complications (vascular events, bleeding and stroke), their outcome is good and often better than that of men. These results are continuously improving thanks to the enhancement of techniques and devices. In view of the published reports reflecting the increasing experience of the teams, it clearly appears that the simplification of TAVI procedures has resulted in improved outcomes. We report here the case of a patient treated by means of a "minimalist" approach to TAVI allowing a reduction of the risks inherent in the procedure. This simplified strategy relies on an optimal use of CT scan findings prior to TAVI. The procedure is carried out under local anesthesia and the main access site is sutured percutaneously (Proglides). The radial artery is used as a secondary access site. Contrast medium is diluted and stimulation is administered via the intraventricular guidewire. Direct stenting is performed when deemed feasible on the basis of CT scan results. Simplified procedures such as these contribute to the improvement of TAVI outcomes. However, further studies focusing on female patients are warranted in order to corroborate these findings.

A general framework for a reliable multivariate analysis and pattern recognition in high-dimensional epidemiological data, based on cluster robustness: a tutorial to enrich the epidemiologists' toolkit.

BACKGROUND: In an epidemiologist's toolbox, three main types of statistical tools can be found: means and proportions comparisons, linear or logistic regression models and Cox-type regression models. All these techniques have their own multivariate formulations, so that biases can be accounted for. Nonetheless, there is an entire set of natively massive multivariate techniques, which are based on weaker assumptions than classical statistical techniques are, and which seem to be underestimated or remain unknown to most epidemiologists. These techniques are used for pattern recognition or clustering ­ that is, for retrieving homogeneous groups in data without any a priori about these groups. They are widely used in connex domains such as genetics or biomolecular studies. METHODS: Most clustering techniques require tuning specific parameters so that groups can be identified in data. A critical parameter to set is the number of groups the technique needs to discover. Different approaches to find the optimal number of groups are available, such as the silhouette approach and the robustness approach. This article presents the key aspects of clustering techniques (how proximity between observations is defined and how to find the number of groups), two archetypal techniques (namely the k-means and PAM algorithms) and how they relate to more classical statistical approaches. RESULTS: Through a theoretical, simple example and a real data application, we provide a complete framework within which classical epidemiological concerns can be reconsidered. We show how to (i) identify whether distinct groups exist in data, (ii) identify the optimal number of groups in data, (iii) label each observation according to its own group and (iv) analyze the groups identified according to separate and explicative data. In addition, how to achieve consistent results while removing sensitivity to initial conditions is explained. CONCLUSIONS: Clustering techniques, in conjunction with methods for parameter tuning, provide the epidemiologist with substantial additional tools. They differ from the usual approaches based on hypothesis-testing because no assumptions are made on the data and these clustering techniques are natively multivariate.