Buoyancy-induced time delays in Babcock-Leighton flux-transport dynamo models

The Sun is a magnetic star whose cyclic activity is thought to be linked to internal dynamo mechanisms. A combination of numerical modelling with various levels of complexity is an efficient and accurate tool to investigate such intricate dynamical processes. We investigate the role of the magnetic buoyancy process in 2D Babcock-Leighton dynamo models, by modelling more accurately the surface source term for poloidal field. Methods. To do so, we reintroduce in mean-field models the results of full 3D MHD calculations of the non-linear evolution of a rising flux tube in a convective shell. More specifically, the Babcock-Leighton source term is modified to take into account the delay introduced by the rise time of the toroidal structures from the base of the convection zone to the solar surface. We find that the time delays introduced in the equations produce large temporal modulation of the cycle amplitude even when strong and thus rapidly rising flux tubes are considered. Aperiodic modulations of the solar cycle appear after a sequence of period doubling bifurcations typical of non-linear systems. The strong effects introduced even by small delays is found to be due to the dependence of the delays on the magnetic field strength at the base of the convection zone, the modulation being much less when time delays remain constant. We do not find any significant influence on the cycle period except when the delays are made artificially strong. A possible new origin of the solar cycle variability is here revealed. This modulated activity and the resulting butterfly diagram are then more compatible with observations than what the standard Babcock-Leighton model produces.Comment: 13 pages, 10 figures, accepted for publication in A&

Minimally invasive repair of pectus excavatum using the Nuss technique in children and adolescents: Indications, outcomes, and limitations

AbstractBackgroundPectus excavatum (PE) is a common congenital deformity. The Nuss technique for minimally invasive repair of PE involves thoracoscopy-assisted insertion of a bar or plate behind the deformity to displace the sternum anteriorly. Our objective here was to clarify the indications and limitations of the Nuss technique based on a review of 70 patients.Materials and methodsA retrospective review of children managed at two centres identified 70 patients who had completed their growth and had their plate removed. Mean age was 13.8 years (range, 6–19 years). The reason for surgery was cosmetic disfigurement in 66 (95%) patients. The original Nuss technique was used in 63 patients, whereas 7 patients required an additional sub-xiphoid approach. Time to implant removal ranged from 8 months to 3 years.ResultsThe cosmetic outcome was considered satisfactory by the patients in 64 (91%) cases and by the surgeon in 60 (85.7%) cases. Major complications requiring further surgery occurred in 6 (8.5%) patients and consisted of haemothorax (n=2), chest wall sepsis (n=2, including 1 after implant removal), allergy (n=1), and implant displacement (n=1). Early or delayed minor complications occurred in 46 (65%) patients and resolved either spontaneously or after non-surgical therapy.DiscussionThe minimal scarring and reliably good outcomes support the widespread use of the Nuss technique in children and adolescents. Our complication rates (minor, 65%; and major, 8.5%) are consistent with previous publications. In our opinion, contra-indications to thoracoscopic PE correction consist of a history of cardio-thoracic surgery and the finding by computed tomography of a sternum-to-spine distance of less than 5cm or of sternum rotation greater than 35°. In these situations, we recommend a sub- and retro-xiphoid approach to guide implant insertion or a classic sterno-chondroplasty procedure.Level of evidenceLevel IV, retrospective descriptive cohort study

Inequality and Inclusion in Latin America

Editors' foreword to the special issue

Gold-Silver Catalysts: Ruling Factors for Establishing Synergism

DPU and SOL immobilisation have been used to prepare 1 %AuAg/TiO2 with internal ratio 1 : 1 and 4 : 1 which have been studied as fresh, calcined in air at 300 \ub0C and reduced at 550 \ub0C in H2. TEM-EDS, XPS, UV-Vis and CO-DRIFT allowed to characterize the samples in terms of particle size, particle composition, exposure and oxidation state of metals. Correlating these characteristics to the catalytic behaviour we concluded that only Au-rich catalysts show synergistic effect, silver in bimetallic systems appears more resistant to oxidation than in monometallic one, thermal treatment enhances the SMSI thus producing (regardless to the post-treatment) almost the same amount of Au\u3b4+ and also Ag\u3b4+. Catalysts prepared by DPU (calcined in air or reduced in H2) are more active than SOL (fresh or calcined) probably due to the higher presence of gold at the surface

Effect of polydispersity on the transport and sound absorbing properties of three-dimensional random fibrous structures

Sophisticated numerical approaches can predict the properties of composite nonwovens. However, for polydisperse random fibrous media, we need to identify microstructural descriptors for accurate predictions. We manufactured polydisperse composite felts with different fibrous structures and characterized them using scanning electron microscope images. The images showed a wide distribution of fiber diameters and a decreasing standard deviation of the azimuthal angle of fibers with increasing compression rate. Current models could not capture the evolution of their transport properties with compression rate. Therefore, we developed a fiber network model for the transport processes of transversely isotropic random fibrous media. The model relates the main visco-thermal dissipation mechanisms to the largest channels within the fluid phase, while the smallest channels lead the inertial behaviors. We estimated the viscous and thermal permeabilities from a representative elementary volume (REV) with a volume weighted average diameter, and the viscous and thermal characteristic lengths from a REV with inverse volume weighted average diameter. A unified empirical model was proposed. The model predictions agree with the experimental results.Comment: 29 pages, 19 figure

MUSCLE : automated multi-objective evolutionary optimization of targeted LC-MS/MS analysis:Automated multi-objective evolutionary optimization of targeted LC-MS/MS analysis

Summary: Developing liquid chromatography tandem mass spectrometry (LC-MS/MS) analyses of (bio)chemicals is both time consuming and challenging, largely because of the large number of LC and MS instrument parameters that need to be optimized. This bottleneck significantly impedes our ability to establish new (bio)analytical methods in fields such as pharmacology, metabolomics and pesticide research. We report the development of a multi-platform, user-friendly software tool MUSCLE (multi-platform unbiased optimization of spectrometry via closed-loop experimentation) for the robust and fully automated multi-objective optimization of targeted LC-MS/MS analysis. MUSCLE shortened the analysis times and increased the analytical sensitivities of targeted metabolite analysis, which was demonstrated on two different manufacturer’s LC-MS/MS instruments. Availability and implementation: Available at http://www.muscleproject.org. Contact: [email protected] Supplementary information: Supplementary data are available at Bioinformatics online

Magnetic cycles of the planet-hosting star Tau Bootis: II. a second magnetic polarity reversal

In this paper, we present new spectropolarimetric observations of the planet-hosting star Tau Bootis, using ESPaDOnS and Narval spectropolarimeters at Canada-France-Hawaii Telescope (CFHT) and Telescope Bernard Lyot (TBL), respectively. We detected the magnetic field of the star at three epochs in 2008. It is a weak magnetic field of only a few Gauss, oscillating between a predominant toroidal component in January and a dominant poloidal component in June and July. A magnetic polarity reversal was observed relative to the magnetic topology in June 2007. This is the second such reversal observed in two years on this star, suggesting that Tau Boo has a magnetic cycle of about 2 years. This is the first detection of a magnetic cycle for a star other than the Sun. The role of the close-in massive planet in the short activity cycle of the star is questioned. Tau Boo has strong differential rotation, a common trend for stars with shallow convective envelope. At latitude 40 deg., the surface layer of the star rotates in 3.31 d, equal to the orbital period. Synchronization suggests that the tidal effects induced by the planet may be strong enough to force at least the thin convective envelope into corotation. Tau Boo shows variability in the Ca H & K and Halpha throughout the night and on a night to night time scale. We do not detect enhancement in the activity of the star that may be related to the conjunction of the planet. Further data is needed to conclude about the activity enhancement due to the planet.Comment: 9 pages, 5 figures, 3 tables Accepted to MNRA