Low parasitic inductance multi-chip SiC devices packaging technology

This paper presents a novel packaging structure which employs stacked substrate and flexible printed circuit board (PCB) to obtain very low parasitic inductance and hence feature high switching speed SiC power devices. A half-bridge module aimed at blocking voltage up to 2.5kV has been designed to accommodate 8 SiC JFETs and 4 SiC diodes. Electromagnetic simulation results reveal extremely low inductance values of the major loops. Then the prototyping of the designed package including the assembly process, all the electrical test to evaluate the electrical performance are presented

Low parasitic inductance multi-chip SiC devices packaging technology

This paper presents a novel packaging structure which employs stacked substrate and flexible printed circuit board (PCB) to obtain very low parasitic inductance and hence feature high switching speed SiC power devices. A half-bridge module aimed at blocking voltage up to 2.5kV has been designed to accommodate 8 SiC JFETs and 4 SiC diodes. Electromagnetic simulation results reveal extremely low inductance values of the major loops. Then the prototyping of the designed package including the assembly process, all the electrical test to evaluate the electrical performance are presented

Multi-technique geochronology of intrusive and explosive activity on Piton des Neiges Volcano, Réunion Island

MD was supported by the AuScope NCRIS2 program, Australian Research Council (ARC) Discovery funding scheme (DP160102427) and Curtin Research Fellowship. CP was supported by the company Austral Energy and by the ANRT CIFRE program (agreement n°2017/1175).The construction of ocean island basaltic volcanoes consists of a succession of eruptions, intrusions, and metamorphism. These events are often temporally ill-constrained because the most widely used radiometric dating methods applicable to mafic volcanic rocks (K-Ar or 40Ar/39Ar on whole rock or groundmass) are prone to inaccuracy when applied to slowly-cooled, altered, or vesicular and aphyric products. Here we adopt a multi-technique geochronology approach (including zircon U-Pb, phlogopite 40Ar/39Ar, zircon and apatite (U-Th)/He, and zircon double-dating) to demonstrate its efficacy when applied to basaltic volcanoes. Taking the main volcano of Réunion Island (Piton des Neiges) as a case study, we establish the time of the major plutonic, metamorphic, and explosive events that had resisted previous dating attempts. We document four stages of pluton emplacement and metamorphism at 2200 - 2000 ka, 1414 ± 8 ka, 665 ± 78 ka, and 150 - 110 ka, all coinciding with volcanism revival after quiescent intervals. We also date a major Plinian eruption at 188.2 ± 10.4 ka, coeval with the formation age of a large caldera, and, finally, we constrain the last eruption of Piton des Neiges to 27 ka, revising a previous estimate of 12 ka. By resolving several conundrums of Réunion's geological history, our multi-technique geochronology approach reveals that endogenous growth of a volcanic island proceeds as pulses at the beginning of renewed volcanism. We also demonstrate that cross-checking eruptions ages by diversified dating techniques is important to better assess the timing and recurrence of basaltic volcanic activity, with implications for hazard prediction.Publisher PDFPeer reviewe

Pelagic Functional Group Modeling: Progress, Challenges and Prospects

In this paper, we review the state of the art and major challenges in current efforts to incorporate biogeochemical functional groups into models that can be applied on basin-wide and global scales, with an emphasis on models that might ultimately be used to predict how biogeochernical cycles in the ocean will respond to global warming. We define the term biogeochemical functional group to refer to groups of organisms that mediate specific chemical reactions in the ocean. Thus, according to this definition, functional groups have no phylogenetic meaning-these are composed of many different species with common biogeochemical functions. Substantial progress has been made in the last decade toward quantifying the rates of these various functions and understanding the factors that control them. For some of these groups, we have developed fairly sophisticated models that incorporate this understanding, e.g. for diazotrophs (e.g. Trichodesmium), silica producers (diatoms) and calcifiers (e.g. coccolithophorids and specifically Emiliania huxleyi). However, current representations of nitrogen fixation and calcification are incomplete, i.e., based primarily upon models of Trichodesmium and E huxleyi, respectively, and many important functional groups have not yet been considered in open-ocean biogeochemical models. Progress has been made over the last decade in efforts to simulate dimethylsulfide (DMS) production and cycling (i.e., by dinoflagellates and prymnesiophytes) and denitrification, but these efforts are still in their infancy, and many significant problems remain. One obvious gap is that virtually all functional group modeling efforts have focused on autotrophic microbes, while higher trophic levels have been completely ignored. It appears that in some cases (e.g., calcification), incorporating higher trophic levels may be essential not only for representing a particular biogeochemical reaction, but also for modeling export. Another serious problem is our tendency to model the organisms for which we have the most validation data (e.g., E huxleyi and Trichodesmium) even when they may represent only a fraction of the biogeochemical functional group we are trying to represent. When we step back and look at the paleo-oceanographic record, it suggests that oxygen concentrations have played a central role in the evolution and emergence of many of the key functional groups that influence biogeochemical cycles in the present-day ocean. However, more subtle effects are likely to be important over the next century like changes in silicate supply or turbulence that can influence the relative success of diatoms versus dinoflagellates, coccolithophorids and diazotrophs. In general, inferences drawn from the paleo-oceanographic record and theoretical work suggest that global warming will tend to favor the latter because it will give rise to increased stratification. However, decreases in pH and Fe supply could adversely impact coccolithophorids and diazotrophs in the future. It may be necessary to include explicit dynamic representations of nitrogen fixation, denitrification, silicification and calcification in our models if our goal is predicting the oceanic carbon cycle in the future, because these processes appear to play a very significant role in the carbon cycle of the present-day ocean and they are sensitive to climate change. Observations and models suggest that it may also be necessary to include the DMS cycle to predict future climate, though the effects are still highly uncertain. We have learned a tremendous amount about the distributions and biogeochemical impact of bacteria in the ocean in recent years, yet this improved understanding has not yet been incorporated into many of our models. All of these considerations lead us toward the development of increasingly complex models. However, recent quantitative model intercomparison studies suggest that continuing to add complexity and more functional groups to our ecosystem models may lead to decreases in predictive ability if the models are not properly constrained with available data. We also caution that capturing the present-day variability tells us little about how well a particular model can predict the future. If our goal is to develop models that can be used to predict how the oceans will respond to global warming, then we need to make more rigorous assessments of predictive skill using the available data

Forecasting Prorocentrum minimum blooms in the Chesapeake Bay using empirical habitat models

Aquaculturists, local beach managers, and other stakeholders require forecasts of harmful biotic events, so they can assess and respond to health threats when harmful algal blooms (HABs) are present. Based on this need, we are developing empirical habitat suitability models for a variety of Chesapeake Bay HABs to forecast their occurrence based on a set of physical-biogeochemical environmental conditions, and start with the dinoflagellate Prorocentrum minimum (also known as P. cordatum).To identify an optimal set of environmental variables to forecast P. minimum blooms, we first assumed a linear relationship between the environmental variables and the inverse of the logistic function used to forecast the likelihood of bloom presence, and repeated the method using more than 16,000 combinations of variables. By comparing goodness-of-fit, we found water temperature, salinity, pH, solar irradiance, and total organic nitrogen represented the most suitable set of variables. The resulting algorithm forecasted P. minimum blooms with an overall accuracy of 78%, though with a significant variability ~ 30-90% depending on region and season. To understand this variability and improve model performance, we incorporated nonlinear effects into the model by implementing a generalized additive model. Even without considering interactions between the five variables used to train the model, this yielded an increase in overall model accuracy (~ 81%) due to the model’s ability to refine the regions in which P. minimum blooms occurred. Including nonlinear interactions increased the overall model accuracy even further (~ 85%) by accounting for seasonality in the interaction between solar irradiance and water temperature. Our findings suggest that the influence of predictors of these blooms change in time and space, and that model complexity impacts the model performance and our interpretation of the driving factors causing P. minimum blooms. Apart from their forecasting potential, our results may be particularly useful when constructing explicit relationships between environmental conditions and P. minimum presence in mechanistic models

First observation of scissors mode states in an odd-mass nucleus

Nuclear resonance fluorescence experiments are reported to search for enhanced M1 scissors mode states in the deformed odd-mass nucleus Dy163. A concentration of dipole strengths near 3 MeV excitation energy is found, which fits nicely into the systematics observed for M1 excitations in the neighboring even-even Dy isotopes. The observed strength distribution and the decay branching ratios are discussed in the context of the interacting boson-fermion model.Dirección General de Investigación Científica y Técnica PB89-063

Laminin-binding integrins and their tetraspanin partners as potential antimetastatic targets

Within the integrin family of cell adhesion receptors, integrins α3β1, α6β1, α6β4 and α7β1 make up a laminin-binding subfamily. The literature is divided on the role of these laminin-binding integrins in metastasis, with different studies indicating either pro- or antimetastatic functions. The opposing roles of the laminin-binding integrins in different settings might derive in part from their unusually robust associations with tetraspanin proteins. Tetraspanins organise integrins into multiprotein complexes within discrete plasma membrane domains termed tetraspanin-enriched microdomains (TEMs). TEM association is crucial to the strikingly rapid cell migration mediated by some of the laminin-binding integrins. However, emerging data suggest that laminin-binding integrins also promote the stability of E-cadherin-based cell–cell junctions, and that tetraspanins are essential for this function as well. Thus, TEM association endows the laminin-binding integrins with both pro-invasive functions (rapid migration) and anti-invasive functions (stable cell junctions), and the composition of TEMs in different cell types might help determine the balance between these opposing activities. Unravelling the tetraspanin control mechanisms that regulate laminin-binding integrins will help to define the settings where inhibiting the function of these integrins would be helpful rather than harmful, and may create opportunities to modulate integrin activity in more sophisticated ways than simple functional blockade

Sediment dispersal in the northwestern Adriatic Sea

Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 113 (2008): C11S03, doi:10.1029/2006JC003868.Sediment dispersal in the Adriatic Sea was evaluated using coupled three-dimensional circulation and sediment transport models, representing conditions from autumn 2002 through spring 2003. The calculations accounted for fluvial sources, resuspension by waves and currents, and suspended transport. Sediment fluxes peaked during southwestward Bora wind conditions that produced energetic waves and strengthened the Western Adriatic Coastal Current. Transport along the western Adriatic continental shelf was nearly always to the south, except during brief periods when northward Sirocco winds reduced the coastal current. Much of the modeled fluvial sediment deposition was near river mouths, such as the Po subaqueous delta. Nearly all Po sediment remained in the northern Adriatic. Material from rivers that drain the Apennine Mountains traveled farther before deposition than Po sediment, because it was modeled with a lower settling velocity. Fluvial sediment delivered to areas with high average bed shear stress was more highly dispersed than material delivered to more quiescent areas. Modeled depositional patterns were similar to observed patterns that have developed over longer timescales. Specifically, modeled Po sediment accumulation was thickest near the river mouth with a very thin deposit extending to the northeast, consistent with patterns of modern sediment texture in the northern Adriatic. Sediment resuspended from the bed and delivered by Apennine Rivers was preferentially deposited on the northern side of the Gargano Peninsula, in the location of thick Holocene accumulation. Deposition here was highest during Bora winds when convergences in current velocities and off-shelf flux enhanced delivery of material to the midshelf.The authors are grateful for funding and support from the Office of Naval Research’s Coastal Geosciences and Marine Modeling programs, the U.S. Geological Survey, and NATO’s SACLANT-CEN