Electrically switching transverse modes in high power THz quantum cascade lasers.

The design and fabrication of a high power THz quantum cascade laser (QCL), with electrically controllable transverse mode is presented. The switching of the beam pattern results in dynamic beam switching using a symmetric side current injection scheme. The angular-resolved L-I curves measurements, near-field and far-field patterns and angular-resolved lasing spectra are presented. The measurement results confirm that the quasi-TM(01) transverse mode lases first and dominates the lasing operation at lower current injection, while the quasi-TM(00) mode lases at a higher threshold current density and becomes dominant at high current injection. The near-field and far-field measurements confirm that the lasing THz beam is maneuvered by 25 degrees in emission angle, when the current density changes from 1.9 kA/cm(2) to 2.3 kA/cm(2). A two-dimension (2D) current and mode calculation provides a simple model to explain the behavior of each mode under different bias conditions

BRAGGATIR: Bragg and total internal reflection waveguides

A novel type of waveguides utilizing simultaneously Bragg reflection and TIR (total internal reflection) for light confinement is proposed and studied. The BRAGGATIR waveguides combine the advantages of Bragg waveguides and lateral ARROWs (antiresonant reflecting optical waveguides) -- namely, large core sizes allowing easy and low loss fiber coupling and their reduced sensitivity to fabrication errors, with the properties of high index contrast ridge waveguides which tolerate small bending radius. Since the proposed waveguides have only one Fabry-Perot layer, they are more compact compared to the Bragg waveguides. Moreover, the large dispersion of the BRAGGATIR waveguides near the resonances may find applications in optical signal processing. Beam propagation method (BPM) and mode solver numerical simulations were performed and the bending losses of different waveguides, namely BRAGGATIR, ridge and ARROW, were compared for different bending radii down to 10 microns. The results demonstrate advantage of the proposed waveguides allowing very small radius ring resonators with large free spectral range and more compact integrated optics devices.Peer reviewed: YesNRC publication: Ye

Mid-infrared silicon-on-insulator Fourier-transform spectrometer chip

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Carbon monoxide exposure enhances arrhythmia after cardiac stress: involvement of oxidative stress

International audienceArrhythmias following cardiac stress are a key predictor of death in healthy population. Carbon monoxide (CO) is a ubiquitous pollutant promoting oxidative stress and associated with hospitalization for cardiovascular disease and cardiac mortality. We investigated the effect of chronic CO exposure on the occurrence of arrhythmic events after a cardiac stress test and the possible involvement of related oxidative stress. Wistar rats exposed chronically (4 weeks) to sustained urban CO pollution presented more arrhythmic events than controls during recovery after cardiac challenge with isoprenaline in vivo. Sudden death occurred in 22% of CO-exposed rats versus 0% for controls. Malondialdehyde (MDA), an end-product of lipid peroxidation, was increased in left ventricular tissue of CO-exposed rats. Cardiomyocytes isolated from CO-exposed rats showed higher reactive oxygen species (ROS) production (measured with MitoSox Red dye), higher diastolic Ca 2? resulting from SR calcium leak and an higher occurrence of irregular Ca 2? transients (measured with Indo-1) in comparison to control cells after a high pacing sequence. Acute treatment with a ROS scavenger (N-acetylcysteine, 20 mmol/L, 1 h) prevented this sequence of alterations and decreased the number of arrhythmic cells following high pacing. Chronic CO exposure promotes oxidative stress that alters Ca 2? homeostasis (through RYR2 and SERCA defects) and thereby mediates the triggering of ventricular arrhythmia after cardiac stress that can lead to sudden death

Optimisation de méthodes diélectriques pour l'hydrologie

National audienc

Clinical characteristics of pediatric hidradenitis suppurativa: a cross-sectional multicenter study of 140 patients

International audienceHidradenitis suppurativa (HS) rarely affects pediatric patients. The literature on pediatric HS patients is scarce. This is a cross-sectional study based on case note review or interviews and clinical examination of 140 pediatric patients undergoing secondary or tertiary level care. Patients were predominantly female (75.5%, n = 105) with a median age of 16. 39% reported 1st-degree relative with HS. Median BMI percentile was 88, and 11% were smokers (n = 15). Median modified Sartorius score was 8.5. Notable comorbidities found were acne (32.8%, n = 45), hirsutism (19.3%, n = 27), and pilonidal cysts (16.4%, n = 23). Resorcinol (n = 27) and clindamycin (n = 25) were the most frequently used topical treatments. Patients were treated with tetracycline (n = 32), or oral clindamycin and rifampicin in combination (n = 29). Surgical excision was performed in 18 patients, deroofing in five and incision in seven patients. Obesity seemed to be prominent in the pediatric population and correlated to parent BMI, suggesting a potential for preventive measures for the family. Disease management appeared to be similar to that of adult HS, bearing in mind that the younger the patient, the milder the disease in majority of cases

Species diversification – which species should we use?

Large detector systems for particle and astroparticle physics; Particle tracking detectors; Gaseous detectors; Calorimeters; Cherenkov detectors; Particle identification methods; Photon detectors for UV. visible and IR photons; Detector alignment and calibration methods; Detector cooling and thermo-stabilization; Detector design and construction technologies and materials. The LHCb experiment is dedicated to precision measurements of CP violation and rare decays of B hadrons at the Large Hadron Collider (LHC) at CERN (Geneva). The initial configuration and expected performance of the detector and associated systems. as established by test beam measurements and simulation studies. is described. © 2008 IOP Publishing Ltd and SISSA