An 800-year high-resolution black carbon ice core record from Lomonosovfonna, Svalbard

Produced by the incomplete combustion of fossil fuel and biomass, black carbon (BC) contributes to Arctic warming by reducing snow albedo and thus triggering a snow-albedo feedback leading to increased snowmelt. Therefore, it is of high importance to assess past BC emissions to better understand and constrain their role. However, only a few long-term BC records are available from the Arctic, mainly originating from Greenland ice cores. Here, we present the first long-term and high-resolution refractory black carbon (rBC) record from Svalbard, derived from the analysis of two ice cores drilled at the Lomonosovfonna ice field in 2009 (LF-09) and 2011 (LF-11) and covering 800 years of atmospheric emissions. Our results show that rBC concentrations strongly increased from 1860 on due to anthropogenic emissions and reached two maxima, at the end of the 19th century and in the middle of the 20th century. No increase in rBC concentrations during the last decades was observed, which is corroborated by atmospheric measurements elsewhere in the Arctic but contradicts a previous study from another ice core from Svalbard. While melting may affect BC concentrations during periods of high temperatures, rBC concentrations remain well preserved prior to the 20th century due to lower temperatures inducing little melt. Therefore, the preindustrial rBC record (before 1800), along with ammonium (NH4+), formate (HCOO−) and specific organic markers (vanillic acid, VA, and p-hydroxybenzoic acid, p-HBA), was used as a proxy for biomass burning. Despite numerous single events, no long-term trend was observed over the time period 1222–1800 for rBC and NH4+. In contrast, formate, VA, and p-HBA experience multi-decadal peaks reflecting periods of enhanced biomass burning. Most of the background variations and single peak events are corroborated by other ice core records from Greenland and Siberia. We suggest that the paleofire record from the LF ice core primarily reflects biomass burning episodes from northern Eurasia, induced by decadal-scale climatic variations.</p

Phytohormone collaboration: zooming in on auxin-brassinosteroid interactions.

Similar to animal hormones, classic plant hormones are small organic molecules that regulate physiological and developmental processes. In development, this often involves the regulation of growth through the control of cell size or division. The plant hormones auxin and brassinosteroid modulate both cell expansion and proliferation and are known for their overlapping activities in physiological assays. Recent molecular genetic analyses in the model plant Arabidopsis suggest that this reflects interdependent and often synergistic action of the two hormone pathways. Such pathway interactions probably occur through the combinatorial regulation of common target genes by auxin- and brassinosteroid-controlled transcription factors. Moreover, auxin and brassinosteroid signaling and biosynthesis and auxin transport might be linked by an emerging upstream connection involving calcium-calmodulin and phosphoinositide signaling

Thin film in-plane actuator: Assessment of monolayer and bilayer mechanical output

This article shows that in an in-plane configuration a thin film and a bulk actuators deliver the same amount of mechanical power under the same voltage. This opens the possibility to reach more powerful actuators while keeping the same geometric dimensions by simply stacking these films. It also demonstrates that the effective transverse-plane piezoelectric coefficient is constant with electric field which is a crucial result for this actuator

rf-sputtering of PMNT thin films

We report on the realization of relaxor ferroelectric thin films by rf magnetron sputtering deposition. We investigated fabrication of films in the solid solution of PMN (Pb(Mg1/3Nb2/3)O3) with PT (PbTiO3). This material is the most studied among the relaxor ferroelectric family for applications in the field of microelectronics and microsystems. We chose the composition with 30% of PT, close to the morphotropic phase boundary between relaxor and normal ferroelectric behavior which exhibits good piezoelectric properties suited to actuators. We have grown the films in a cold deposition process. The substrates used were Si/SiO2 coated by Ti/Pt electrodes. This allowed to synthesize pyrochlore-free PMNT ceramic thin films at temperatures between 450 and 675°C in a postdeposition conventional annealing. We performed dielectric and ferroelectric characterizations of the films with Pt upper electrodes. Dielectric constant was measured as a function of temperature (up to 155°C) and frequency (1 kHz ~ 1 MHz). We obtained relative dielectric constant of the order of 1500. Relaxor behavior and ferroelectric properties are evidenced and are shown to be enhanced by annealing temperature

Semi-Automatic Perspective Lines from Paintings

Perspective cues play an important role in painting analysis as it may unveil important characteristics about the painter's techniques and creation process. Nevertheless, extracting perspective lines and their corresponding vanishing points is usually a laborious manual task. Moreover, small variations in the lines may lead to large variations in the vanishing points. In this work, we propose a semi-automatic method to extract perspective lines from paintings in order to mitigate the human variability factor and reduce the workload.Computer Graphics and Visualisatio

Semi-Automatic Perspective Lines from Paintings

Perspective cues play an important role in painting analysis as it may unveil important characteristics about the painter's techniques and creation process. Nevertheless, extracting perspective lines and their corresponding vanishing points is usually a laborious manual task. Moreover, small variations in the lines may lead to large variations in the vanishing points. In this work, we propose a semi-automatic method to extract perspective lines from paintings in order to mitigate the human variability factor and reduce the workload

An experimental study on vapor cloud explosion of propane-oxygen stoichiometric mixture

International audienceVapor cloud explosions (VCEs) are serious hazards in refining and petrochemical industries. Statistics indicate that 75% of the total losses were caused by explosion so that considerable research effort has been focused on this subject. Consequences of an explosion are aerial overpressure and impulse, responsible for injury to humans and structures. Many studies were performed with fuel-air explosions but few works focused on fuel-oxygen mixtures explosion. In this study, experiments were performed on a large experimental field. In order to represent realistic conditions, the shape of the gas envelope was elongated like the dispersion shape from leakage with small wind. The flammable cloud was ignited with SEMTEX explosive charges put at the center of the gas volume envelopes. Overpressure values were collected at different positions on the field. Flame propagation was recorded by high speed camera and gave a constant velocity of 2384 m.s-1 , indicating a detonation regime