Aurore: A platform for ultrafast sciences.

We present the Aurore platform for ultrafast sciences. This platform is based on a unique 20 W, 1 kHz, 26 fs Ti:sapphire laser system designed for reliable operation and high intensity temporal contrast. The specific design ensures the high stability in terms of pulse duration, energy, and beam pointing necessary for extended experimental campaigns. The laser supplies 5 different beamlines, all dedicated to a specific field: attosecond science (Aurore 1), ultrafast phase transitions in solids (Aurore 2 and 3), ultrafast luminescence in solids (Aurore 4), and femtochemistry (Aurore 5). The technical specifications of these five beamlines are described in detail, and examples of the recent results are given.

Small left colon syndrome in 3 sisters.

Neonatal small left colon syndrome is a rare cause of bowel obstruction. Its etiology remains unknown, but a significant association has been noted between maternal diabetes and small left colon. No reported cases within the same family could be found in the literature, excepting 2 sets of twins. We report 3 cases of small left colon syndrome in 3 consecutive sisters born of a nondiabetic mother. This raises the question of a genetic factor in its etiology.

First Report of Septoria sp. Infecting Stevia rebaudiana in France and Screening of Stevia rebaudiana Genotypes for Host Resistance.

Stevia rebaudiana, for which cultivation is on the increase worldwide, accumulates acaloric intense sweeteners called steviol glycosides (SGs) in its leaves. Yields can be affected by Septoria leaf spot (SLS) caused by Septoria spp. The objectives of the research were (1) to morphologically and genetically characterize five isolates of Septoria sp. found for the first time from outbreaks of Septoria in stevia fields in Southwestern France and (2) to screen S. rebaudiana germplasm from diverse origins through an automated inoculation method using one of the isolates. Multilocus sequence typing grouped the five isolates obtained from symptomatic plants, closely related to Septoria lycopersici and Septoria apiicola. The response to Septoria sp. of 10 genotypes from different origins was assessed for disease severity (DS), either by visually scoring the symptomatic portion of the whole plants or the portion of symptomatic foliar area (PLSA) determined by image analysis, and the area under the disease progress curve (AUDPC) calculated on the basis of the disease severity rating taken 12, 15, 18, and 21 days after inoculation. No genotypes with complete resistance were identified. Moderately susceptible genotypes "Gawi" and "Esplac1" exhibited only 10 to 15% of symptomatic part on whole plant and the slowest disease development. They could be distinguished from highly susceptible ones "E8", "C", and "E161718" exhibiting up to 40% of symptomatic part on whole plant. The variability of response to Septoria sp. that exists in S. rebaudiana opens up the field of breeding strategies for the development of new cultivars for sustainable and organic S. rebaudiana production.

Modeling of the interaction of an x-ray free-electron laser with large finite samples.

We describe a model for the study of the interaction of short x-ray free-electron laser (XFEL) pulses with large finite samples. Hydrodynamics is solved in one-dimensional planar geometry with consideration of the electron-ion energy exchange and of the possible elastoplastic behavior. From a time-dependent calculation of the complex refractive index and of the underlying atomic physics, XFEL energy deposition is modeled through a calculation of the radiation field in the material. In the case of hard x-ray irradiation, energetic electrons induced by the XFEL absorption can propagate and deposit their energy outside the interaction region. Simulations of the interaction of hard x-ray ultrashort pulses with solid materials Ru and Si at different grazing incidence angles are presented and discussed. The results obtained demonstrate the potential of this approach to predict damage dynamics for materials of interest for x-ray optics.

High-pressure structural changes in liquid silica.

The structural properties of liquid silica at high pressure and moderate temperature conditions, also referred to as the warm dense matter regime, were investigated using time-resolved K-edge x-ray absorption spectroscopy and ab initio calculations. We used a nanosecond laser beam to compress uniformly a solid SiO_{2} target and a picosecond laser beam to generate a broadband x-ray source. We obtained x-ray absorption spectra at the Si K edge over a large pressure-temperature domain to probe the liquid phase up to 3.6 times the normal solid density. Using ab initio simulations, we are able to interpret the changes in the x-ray absorption near-edge structure with increasing densities as an increase in the coordination number of silicon by oxygen atoms from 4 to 9. This indicates that, up to significant temperatures, the liquid structure becomes akin to what is found in the solid SiO_{2} phases.

Comparative study of the X-ray reflectivity and in-depth profile of a-C, B4C and Ni coatings at 0.1-2 keV.

The use of soft X-rays near the carbon edge of absorption (270-300 eV) greatly enhances studies in various branches of science. However, the choice of reflecting coatings for mirrors operating in free-electron and X-ray free-electron laser (FEL and XFEL) beamlines in this spectral range is not so evident and experimental justifications of the mirror efficiency are rather limited. In the present paper it is demonstrated experimentally that the reflectivity of B4C- and Ni-coated grazing-incidence mirrors is high enough for their operation in FEL or XFEL beamlines near the carbon K-edge of absorption. The minimal reflectivity of both mirrors proves to exceed 80% near the carbon absorption edge at a grazing angle of 0.6°. An in-depth profile of the chemical elements composing the reflecting coatings is reconstructed based on analysis of a set of reflectivity curves measured versus the grazing angle at different photon energies in the soft X-ray spectral region. This allows us to predict correctly the mirror reflectivity at any X-ray energy and any grazing angle.

[Does prenatal diagnosis modify neonatal management and early outcome of children with esophageal atresia type III?]. / Le diagnostic anténatal modifie-t-il la prise en charge néonatale et le devenir à 1 an des enfants suivis pour atrésie de l'œsophage de type III ?

OBJECTIVE: Evaluate neonatal management and outcome of neonates with either a prenatal or a post-natal diagnosis of EA type III. STUDY DESIGN: Population-based study using data from the French National Register for EA from 2008 to 2010. We compared children with prenatal versus post-natal diagnosis in regards to prenatal, maternal and neonatal characteristics. We define a composite variable of morbidity (anastomotic esophageal leaks, recurrent fistula, stenosis) and mortality at 1 year. RESULTS: Four hundred and eight live births with EA type III were recorded with a prenatal diagnosis rate of 18.1%. Transfer after birth was lower in prenatal subset (32.4% versus 81.5%, P<0.001). Delay between birth and first intervention was not significantly different. Defect size (2cm vs 1.4cm, P<0.001), gastrostomy (21.6% versus 8.7%, P<0.001) and length in neonatal unit care were higher in prenatal subset (47.9 days versus 33.6 days, P<0.001). The composite variables were higher in prenatal diagnosis subset (38.7% vs 26.1%, P=0.044). CONCLUSION: Despite the excellent survival rate of EA, cases with antenatal detection have a higher morbidity related to the EA type (longer gap). Even if it does not modify neonatal management and 1-year outcome, prenatal diagnosis allows antenatal parental counseling and avoids post-natal transfer.

Multi-channel electronic and vibrational dynamics in polyatomic resonant high-order harmonic generation.

High-order harmonic generation in polyatomic molecules generally involves multiple channels of ionization. Their relative contribution can be strongly influenced by the presence of resonances, whose assignment remains a major challenge for high-harmonic spectroscopy. Here we present a multi-modal approach for the investigation of unaligned polyatomic molecules, using SF6 as an example. We combine methods from extreme-ultraviolet spectroscopy, above-threshold ionization and attosecond metrology. Fragment-resolved above-threshold ionization measurements reveal that strong-field ionization opens at least three channels. A shape resonance in one of them is found to dominate the signal in the 20-26 eV range. This resonance induces a phase jump in the harmonic emission, a switch in the polarization state and different dynamical responses to molecular vibrations. This study demonstrates a method for extending high-harmonic spectroscopy to polyatomic molecules, where complex attosecond dynamics are expected.

Metallization of warm dense SiO(2) studied by XANES spectroscopy.

We investigate the evolution of the electronic structure of fused silica in a dense plasma regime using time-resolved x-ray absorption spectroscopy. We use a nanosecond (ns) laser beam to generate a strong uniform shock wave in the sample and a picosecond (ps) pulse to produce a broadband x-ray source near the Si K edge. By varying the delay between the two laser beams and the intensity of the ns beam, we explore a large thermodynamical domain with densities varying from 1 to 5 g/cm^{3} and temperatures up to 5 eV. In contrast to normal conditions where silica is a well-known insulator with a wide band gap of 8.9 eV, we find that shocked silica exhibits a pseudogap as a semimetal throughout this thermodynamical domain. This is in quantitative agreement with density functional theory predictions performed using the generalized gradient approximation.

Towards simultaneous measurements of electronic and structural properties in ultra-fast x-ray free electron laser absorption spectroscopy experiments.

The rapidly growing ultrafast science with X-ray lasers unveils atomic scale processes with unprecedented time resolution bringing the so called "molecular movie" within reach. X-ray absorption spectroscopy is one of the most powerful x-ray techniques providing both local atomic order and electronic structure when coupled with ad-hoc theory. Collecting absorption spectra within few x-ray pulses is possible only in a dispersive setup. We demonstrate ultrafast time-resolved measurements of the LIII-edge x-ray absorption near-edge spectra of irreversibly laser excited Molybdenum using an average of only few x-ray pulses with a signal to noise ratio limited only by the saturation level of the detector. The simplicity of the experimental set-up makes this technique versatile and applicable for a wide range of pump-probe experiments, particularly in the case of non-reversible processes.

Prospective multicenter evaluation of colon capsule examination indicated by colonoscopy failure or anesthesia contraindication.

BACKGROUND AND STUDY AIMS: In France, in about 5% of cases colonoscopies are incomplete or temporarily contraindicated.We tested the diagnostic yield of colon capsule endoscopy (CCE) in these patients. PATIENTS AND METHODS: In a prospective study, in 17 French centers, inclusion criteria were colonoscopy failure or general disease that excluded colonoscopy with anesthesia. Patients underwent CCE using the first-generation PillCam Colon capsule. The main end point was CCE diagnostic yield, defined as identification of a colorectal lesion that directly explained symptoms or necessitated a diagnostic or therapeutic examination. A secondary objective was to test a simplified Movi-Prep colon cleansing. Follow-up to identify missed symptomatic cancer was scheduled. RESULTS: CCE showed positive findings in 36 patients (diagnostic yield 33.6 %), among whom 23 subsequently underwent therapeutic intervention. Among 64 patients with negative capsule findings, 9 had a complementary procedure showing adenomas in only 1 case. CCE was incomplete in 7/107 patients. Colonoscopy was done in one patient to retrieve a capsule retained in the left colon, and sigmoidoscopy in 11 because the rectum was not reached. No colorectal cancer was diagnosed during the follow-up period. Colon cleansing with MoviPrep was rated good or excellent in 75.9% of cases. CONCLUSION: This study shows the feasibility and the usefulness of CCE in the situation of colonoscopy failure or contraindication. The colon capsule modality should be tested against other available approaches, such as virtual colonoscopy or repeat colonoscopy by an expert.

Time-resolved investigation of nanometer scale deformations induced by a high flux x-ray beam.

We present results of a time-resolved pump-probe experiment where a Si sample was exposed to an intense 15 keV beam and its surface monitored by measuring the wavefront deformation of a reflected optical laser probe beam. By reconstructing and back propagating the wavefront, the deformed surface can be retrieved for each time step. The dynamics of the heat bump, build-up and relaxation, is followed with a spatial resolution in the nanometer range. The results are interpreted taking into account results of finite element method simulations. Due to its robustness and simplicity this method should find further developments at new x-ray light sources (FEL) or be used to gain understanding on thermo-dynamical behavior of highly excited materials.

Phase characterization of the reflection on an extreme UV multilayer: comparison between attosecond metrology and standing wave measurements.

We characterize the phase shift induced by reflection on a multilayer mirror in the extreme UV range (80-93 eV) using two techniques: one based on high order harmonic generation and attosecond metrology (reconstruction of attosecond beating by interference of two-photon transitions), and a second based on synchrotron radiation and measurements of standing waves (total electron yield). We find an excellent agreement between the results from the two measurements and a flat group delay shift (±40 as) over the main reflectivity peak of the mirror.

Interaction of short x-ray pulses with low-Z x-ray optics materials at the LCLS free-electron laser.

Materials used for hard x-ray-free-electron laser (XFEL) optics must withstand high-intensity x-ray pulses. The advent of the Linac Coherent Light Source has enabled us to expose candidate optical materials, such as bulk B4C and SiC films, to 0.83 keV XFEL pulses with pulse energies between 1 µJ and 2 mJ to determine short-pulse hard x-ray damage thresholds. The fluence required for the onset of damage for single pulses is around the melt fluence and slightly lower for multiple pulses. We observed strong mechanical cracking in the materials, which may be due to the larger penetration depths of the hard x-rays.

Small-bowel capsule endoscopy diagnoses early and advanced neoplasms in asymptomatic patients with Lynch syndrome.

BACKGROUND AND STUDY AIMS: Patients with Lynch syndrome are at increased risk of developing small-bowel adenocarcinoma, which usually has a bad prognosis and needs to be diagnosed early. Our aim was to evaluate the yield of capsule endoscopy and CT enteroclysis in this situation. PATIENTS AND METHODS: We performed a prospective, blinded, comparative study of capsule endoscopy and CT enteroclysis in five academic centers. Thirty-five consecutive asymptomatic patients with Lynch syndrome, all with one proven deleterious mutation, were included. A double reading was performed blind for both types of examination. RESULTS: Histologically confirmed small-bowel neoplasms were diagnosed in three patients (8.6 %): one adenocarcinoma (T3N0M0) and two adenomas with low-grade dysplasia. Capsule endoscopy identified all neoplasms. CT enteroclysis raised suspicion of one neoplasm (adenocarcinoma) but missed the two others. Concordance between the two capsule readings was high with a κ value of 0.78 (95 %CI 0.55 to 1.0), which was not the case for CT enteroclysis, where the κ value was 0.15 (95 %CI -0.27 to 0.58). CONCLUSION: Curable early or advanced neoplasms in asymptomatic patients with Lynch syndrome using capsule endoscopy can be detected with a better reproducibility than with CT enteroclysis. The clinical usefulness of systematic small-bowel screening in these patients should be confirmed through large prospective studies.

[Pylephlebitis in the child: a challenging diagnosis]. / Pyléphlébite chez l'enfant: un diagnostic difficile.

Pylephlebitis or septic thrombophlebitis of the portomesenteric veins is a complication of intra-abdominal infections. The disease is rare in children and the diagnosis is often delayed. The morbidity of pylephlebitis is relatively low, although there is a risk of residual thrombosis. We report on 2 cases of pylephlebitis in a 12-year-old girl and a 13-year-old boy, following undiagnosed appendicitis. In the 1st case, the young girl had been misdiagnosed with Salmonella infection and was given antibiotics; in the 2nd case, the boy had retrocecal appendicitis that was clinically subacute. An accurate diagnosis was finally made in both cases by CT scan. Both children evolved satisfactorily following appendectomy, long-term antibiotics, and anticoagulation. Clinically, the severe sepsis associated with pylephlebitis is at the forefront. Physical examination is often normal and therefore of little help; the knowledge of a preceding abdominal infection leads to further radiological investigations. Biologically, there are pronounced signs of infection. CT is the preferred exam for diagnosing pylephlebitis, as it can also show the underlying cause of the intra-abdominal sepsis or possible complications. Doppler sonography is recommended more for follow-up of the portal vein thrombosis. Treatment of pylephlebitis associated with appendicitis always includes long-term antibiotics. An appendectomy is always performed either at the time of diagnosis or later. The need for anticoagulation therapy in children is controversial. However, most pediatricians recommend its use, beginning as soon as possible, to be continued until normalization of portal vein flow.

Diagnostic accuracy of esophageal capsule endoscopy versus conventional upper digestive endoscopy for suspected esophageal squamous cell carcinoma.

BACKGROUND AND STUDY AIM: A video capsule similar to that used in small-bowel capsule endoscopy is now available for esophageal exploration. The aim of our study was to compare the accuracy of upper endoscopy (esophageal gastroduodenoscopy [EGE]) with esophageal capsule endoscopy (ECE) in patients at risk of esophageal squamous cell cancer (SCC). PATIENTS AND METHODS: 68 patients at risk of SCC secondary to a history of head and neck neoplasia were included in this comparison of techniques for detecting SCC and dysplasia. ECE was done using the first generation Pillcam ESO and EGE was performed in accordance with the usual practice of each center, followed by examination with 2 % Lugol staining and biopsy of unstained areas (39 neoplasia comprising 5 low grade dysplasia, 8 high grade dysplasia and 26 SCC). RESULTS: Compared with EGE with and without Lugol staining, the sensitivities of ECE for neoplasia diagnosis were 46 % and 54 %, respectively. On a per-patient basis, the sensitivity, specificity, and positive and negative predictive value of ECE were 63 %, 86 %, 77 % and 76 %, respectively, compared with EGE without staining, and 61 %, 86 %, 77 % and 73 % compared with EGE with iodine staining. Neither the ECE transit time nor the distance between the esopharyngeal line and the neoplastic lesion differed between the 21 false-negative and 18 true-positive cases diagnosed by ECE; the only difference was a smaller median diameter among false negatives ( P < 0.001). CONCLUSION: In a cohort at high risk for esophageal SCC, ECE is not sensitive enough to diagnose neoplastic lesions.

Spot size characterization of focused non-Gaussian X-ray laser beams.

We present a new technique for the characterization of non-Gaussian laser beams which cannot be described by an analytical formula. As a generalization of the beam spot area we apply and refine the definition of so called effective area (A(eff)) [1] in order to avoid using the full-width at half maximum (FWHM) parameter which is inappropriate for non-Gaussian beams. Furthermore, we demonstrate a practical utilization of our technique for a femtosecond soft X-ray free-electron laser. The ablative imprints in poly(methyl methacrylate) - PMMA and amorphous carbon (a-C) are used to characterize the spatial beam profile and to determine the effective area. Two procedures of the effective area determination are presented in this work. An F-scan method, newly developed in this paper, appears to be a good candidate for the spatial beam diagnostics applicable to lasers of various kinds.

Real-time evolution of the valence electronic structure in a dissociating molecule.

Time-resolved valence band photoelectron spectroscopy with a temporal resolution of 135 fs is used to map the entire occupied valence electronic structure of photoexcited gas-phase Br2 molecules during dissociation. The observed shifting and mixing of valence energy levels defines a transition period where the system appears to be intermediate between atoms and molecules. The surprisingly short bond breaking or dissociation time is determined by monitoring in real time how the photoelectron multiplet structure of the free atom arises from the valence states of the photoexcited molecule.

Esophageal capsule endoscopy vs. EGD for the evaluation of portal hypertension: a French prospective multicenter comparative study.

OBJECTIVES: Esophagogastroduodenoscopy (EGD) is the standard method for the diagnosis of esophago-gastric varices. The aim of this prospective multicenter study was to evaluate the PillCam esophageal capsule endoscopy (ECE) for this indication. METHODS: Patients presenting with cirrhotic or noncirrhotic portal hypertension underwent ECEfollowed by EGD at the time of diagnosis. Capsule recordings were blindly read by two endoscopists. RESULTS: A total of 120 patients (72 males, mean age: 58 years; mean Child-Pugh score: 7.2) were included. Esophageal varices were detected in 74 patients. No adverse event was observed after either EGD or ECE. Seven (6%) patients were unable to swallow the capsule. The mean recording time was 204 s (range 1-876). Sensitivity, specificity, negative predictive value, and positive predictive value of ECE for the detection of esophageal varices were 77%, 86%, 69%, and 90%, respectively. Sensitivity, specificity, negative and positive predictive values of ECE for the indication of primary prophylaxis (esophageal varices > or = grade 2 and/or red signs) were 77, 88, 90, and 75%, respectively, and 85% of the patients were adequately classified for the indication (or not) of prophylaxis. Interobserver concordance for ECE readings was 79.4% for the diagnosis of varices, 66.4% for the grading of varices, and 89.7% for the indication of prophylaxis. CONCLUSIONS: This large multicenter study confirms the safety and acceptable accuracy of ECE for the evaluation of esophageal varices. ECE might be proposed as an alternative to EGD for the screening of portal hypertension, especially in patients unable or unwilling to undergo EGD.