ALBERT

Description: The aim of this paper is to analyse a numerical method to solve transient eddy current problems with input current intensities as data, formulated in terms of the magnetic field in a bounded domain including conductors and dielectrics. To this end, we introduce a time-dependent weak formulation and prove its well-posedness. We propose a finite element method for space discretization based on the Nédélec edge elements on tetrahedral meshes, for which we obtain error estimates. Then we introduce a backward Euler scheme for time discretization and prove error estimates for the fully discrete problem, too. Furthermore, a magnetic scalar potential is introduced to deal with the curl-free condition in the dielectric domain, which leads to an important saving in computational effort. Finally, the method is applied to solve two problems: a test with a known analytical solution and an application to electromagnetic forming.

Description: Journal of Medicinal Chemistry DOI: 10.1021/jm300425y

Description: Sea surface temperature (SST) anomalies in the tropical Atlantic have been associated with precipitation anomalies in West Africa that form a dipole pattern with centers over the Sahel and the Gulf of Guinea. Whilst this was clear before the 1970's, the dipole pattern almost disappeared after that date, as the anti-correlation between rainfall anomalies in the Sahel and Guinea dropped abruptly. Simultaneously, the anti-correlations between Sahel rainfall and tropical Pacific SSTs strengthened. It has been posited that these changes after the 1970's developed as rainfall over West Africa started to co-vary with SSTs in the global tropics. In this co-variability, enhanced summer rainfall over West Africa with a monopole pattern corresponds to warmer SSTs in the tropical Atlantic and Maritime Continent, and colder SSTs in the tropical Pacific and western Indian Oceans. The present paper describes the hitherto unexplored seasonal evolution of this co-variability and the physical mechanisms at work. Sensitivity experiments with two atmospheric general circulation models demonstrate that, after the 1970's, the impacts of SST anomalies in the Indo-Pacific counteract those in the Atlantic in terms of generating rainfall anomalies over the Sahel, and that this superposition of effects is primarily linear. Therefore, at interannual timescales, the change in the patterns of co-variability between West African rainfall and tropical SSTs can explain the non-stationary relationship between the anomalies in these two fields.

Description: We analyse the energetics of the major radio flare of 2005 October 8 in GRS 1915+105. The flare is of particular interest because it is one of the most luminous and energetic radio flares from a Galactic black hole that has ever been observed. The motivation is twofold. One, to learn more about the energetics of this most extreme phenomenon and its relationship to the accretion state. The second is to verify if the calibrated estimates of the energy of major radio flares (based on the peak low frequency optically thin flux) derived from flares in the period 1996–2001 in Punsly & Rodriguez, PR13 hereafter, can be used to estimate plasmoid energy beyond this time period. We find evidence that the calibrated curves are still accurate for this strong flare. Furthermore, the physically important findings of PR13 are supported by the inclusion of this flare: the flare energy is correlated with both the intrinsic bolometric X-ray luminosity, L bol , ~1 h before ejection and L bol averaged over the duration of the ejection of the plasmoid and L bol is highly elevated relative to historic levels just before and during the ejection episode. A search of the data archives reveal that only the 2005 October 8 flare and those in PR13 have adequate data sampling to allow estimates of both the energy of the flare and the X-ray luminosity before and during flare launch.

Description: The complex optical index ñ (= n  + i κ ) of InAs/GaSb type-II superlattice (T2SL) was determined in the 1–6  μ m range from reflectivity measurements of resonant structures at 80 K. Several air/superlattice/gold cavities of various thicknesses were fabricated and their reflectivity was measured. As the large variations induced by the cavity resonances in the studied range can be accurately modeled, we were able to determine the complex optical index ñ of InAs/GaSb T2SL with an error of only a few percent. We found that the in-plane refractive index n of the T2SL lies between 3.65 and 3.77 in the mid-infrared wavelength range, and the absorption coefficient κ decreases from 0.23 to 0.001 as the wavelength increases from 1.25 to 5.65  μ m. The subtractive Kramers-Kronig relation allowed us to verify our determination of ñ .

Description: ABSTRACT [1]  We present a numerical model that shows the transgressing upper shoreline of wave-dominated estuaries (bayhead deltas), which commonly contain populous urban and industrial centers, stabilize and their rate of retreat decreases at tributary junctions. The decreased rate of retreat across a tributary junction is caused by a decrease in total accommodation while sediment supply remains conserved. Our model predicts that bayhead deltas from smaller systems will be located closer to tributary confluences than their larger counterparts. An examination of modern bayhead deltas in Albemarle Sound, US Atlantic Coast reveals that bayhead deltas from smaller tributaries are located closer to tributary confluences than bayhead deltas associated with larger tributaries, supporting our model prediction. Our results highlight the importance of antecedent topography created during falling sea levels on shaping the nature of transgression during the ensuing sea-level rise. In particular, tributary junctions act as pinning points during transgression.

Description: Trichodesmium, a nonheterocystous cyanobacterium widely abundant in the surface water of the tropical and subtropical ocean, fixes dinitrogen under high light conditions while concurrently undergoing photosynthesis. The new production considerably influences the cycling of nitrogen and carbon in the ocean. Here, we investigated how light intensity and nickel (Ni) availability interplay to control daily rates and diel patterns of N2 fixation in Trichodesmium. We found that increasing Ni concentration increased N2 fixation rates by up to 30-fold in the high light treatment. Cultures subjected to high Ni and light levels fixed nitrogen throughout most of the 24 H light:dark regime with the highest rate coinciding with the end of the 12 H light period. Our study demonstrates the importance of Ni on nitrogen fixation rates for Trichodesmium under high light conditions. Scientific Reports 4 doi: 10.1038/srep04445

Description: Seasonal drought, typical of temperate and Mediterranean environments, creates problems in establishing plantations and affects development and yield, and it has been widely studied in numerous species. Forestry fast-growing species such as Eucalyptus spp. are an important resource in such environments, selected clones being generally used for production purposes in plantations in these areas. However, use of mono-specific plantations increases risk of plant loss due to abiotic stresses, making it essential to understand differences in an individual clone's physiological responses to drought stress. In order to study clonal differences in drought responses, nine Eucalyptus globulus (Labill.) clones (C14, C46, C97, C120, C222, C371, C405, C491 and C601) were gradually subjected to severe drought stress (〈14% of field capacity). A total of 31 parameters, physiological (e.g., photosynthesis, gas exchange), biochemical (e.g., chlorophyll content) and hormonal (abscisic acid [ABA] content), were analysed by classic and multivariate techniques. Relationships between parameters were established, allowing related measurements to be grouped into functional units (pigment, growth, water and ABA). Differences in these units showed that there were two distinct groups of E. globulus clones on the basis of their different strategies when faced with drought stress. The C14 group (C14, C120, C405, C491 and C601) clones behave as water savers, maintaining high water content and showing high stomatal adjustment, and reducing their aerial growth to a great extent. The C46 group (C46, C97, C222 and C371) clones behave as water spenders, reducing their water content drastically and presenting osmotic adjustment. The latter maintains the highest growth rate under the conditions tested. The method presented here can be used to identify appropriate E. globulus clones for drought environments, facilitating the selection of material for production and repopulation environments.

Description: Sea-level anomalies are intra-seasonal increases in water level forced by meteorological and oceanographic processes unrelated to storms. The effects of sea-level anomalies on beach morphology are unknown, but important to constrain because these events have been recognized over large stretches of continental margins. Here, we present beach erosion measurements along Onslow Beach, a barrier island on the U.S. East Coast, in response to a year with frequent sea-level anomalies and no major storms. The anomalies enabled extensive erosion, which was similar and in most places greater than the erosion that occurred during a year with a hurricane. These results highlight the importance of sea-level anomalies in facilitating coastal erosion and advocate for their inclusion in beach-erosion models and management plans. Sea-level anomalies amplify the erosive effects of accelerated sea-level rise and changes in storminess associated with global climate change.

Description: Using data obtained with the Australia Telescope Compact Array (ATCA), we have characterized the amount, spatial distribution and kinematics of the molecular gas in the merging, double-nucleus type 2 quasar (QSO) SDSS J002531.46–104022.2 (hereafter SDSS J0025–10) at z  = 0.30 using the CO(1–0) transition. This is one of the scarce examples of quasar host galaxies where the CO emission has been resolved spatially at any redshift. We infer a molecular gas mass $M_{\rm H_2}=(6\pm 1)\times 10^9$ M , which is distributed in two main reservoirs separated by ~9 kpc. It has been found that ~60 per cent of the gas is in the central region, associated with the QSO nucleus and/or the intermediate region between the two nuclei. The other 40 per cent is associated with the northern tidal tail and is therefore unsettled. With its high infrared (IR) luminosity L IR  = (1.1 ± 0.3)  x 10 12 L , SDSS J0025–10 is an analogue of local luminous infrared galaxies (LIRGs with high L IR 〉 several x 10 11 L ) and ultraluminous infrared galaxies (ULIRGs). The clear evidence for an ongoing major merger of two gas-rich progenitors, the high L IR dominated by a starburst, the massive reservoir of molecular gas, with a large fraction still unsettled, and the quasar activity are all properties consistent with a transition phase in the (U)LIRG–optical QSO evolutionary scenario. We propose that we are observing the system during a particular transient phase, prior to more advanced mergers where the nuclei have already coalesced. We argue that a fraction of the molecular gas reservoir is associated with a tidal dwarf galaxy identified in the optical Hubble Space Telescope image at the tip of the northern tidal tail. The formation of such structures is predicted by simulations of colliding galaxies.