Hubbard exciton revealed by time-domain optical spectroscopy

We use broadband ultra-fast pump-probe spectroscopy in the visible range to study the lowest excitations across the Mott-Hubbard gap in the orbitally ordered insulator YVO3. Separating thermal and non-thermal contributions to the optical transients, we show that the total spectral weight of the two lowest peaks is conserved, demonstrating that both excitations correspond to the same multiplet. The pump-induced transfer of spectral weight between the two peaks reveals that the low-energy one is a Hubbard exciton, i.e. a resonance or bound state between a doublon and a holon. Finally, we speculate that the pump-driven spin-disorder can be used to quantify the kinetic energy gain of the excitons in the ferromagnetic phase.Comment: 5 pages and 6 figures, 9 pages and 12 figures with additional material

Compressibility of CeMIn5Ce M In_5 and Ce2MIn8Ce_2 M In_8 (M = Rh, Ir and Co) Compounds

The lattice parameters of the tetragonal compounds Ce$M$In$_{5}$ and Ce$_{2}M$In$_{8}$($M=$Rh, Ir and Co) have been studied as a function of pressure up to 15 GPa using a diamond anvil cell under both hydrostatic and quasihydrostatic conditions at room temperature. The addition of $M$In$_{2}$ layers to the parent CeIn$_{3}$ compound is found to stiffen the lattice as the 2-layer systems (average of bulk modulus values $B_{0}$ is 70.4 GPa) have a larger $B_{0}$ than CeIn$_{3}$ (67 GPa), while the 1-layer systems with the are even stiffer (average of $B_{0}$ is 81.4 GPa). Estimating the hybridization using parameters from tight binding calculations shows that the dominant hybridization is $fp$ in nature between the Ce and In atoms. The values of $V_{pf}$ at the pressure where the superconducting transition temperature $T_{c}$ reaches a maximum is the same for all Ce$M$In$_{5}$ compounds. By plotting the maximum values of the superconducting transition temperature $T_{c}$ versus $c/a$ for the studied compounds and Pu-based superconductors, we find a universal $T_{c}$ versus $c/a$ behavior when these quantities are normalized appropriately. These results are consistent with magnetically mediated superconductivity.Comment: Updated version resubmitted to Phys. Rev.

Piccole capitali creative

Nel secolo urbano che abbiamo di fronte, la citt\ue0 sar\ue0 lo scenario della competizione delle energie, delle risorse umane, delle intelligenze collettive e della creativit\ue0 per la costruzione di un\u2019evoluzione pi\uf9 compatibile con le identit\ue0 e le vocazioni e pi\uf9 sostenibile rispetto alle risorse ed alle sensibilit\ue0 del territorio. I segnali delle sue forme, delle sue relazioni e delle sue identit\ue0 sono gi\ue0 evidenti in alcune citt\ue0 del presente ed ad essi sono dedicate numerose ricerche urbanistiche, sociologiche ed economiche. Ma i segnali sono evidenti e trasmettono ispirazioni e stimoli anche a chi osserva la citt\ue0 per mestiere di progettista, di pianificatore, di stratega dello sviluppo. Il XXI secolo sar\ue0 l\u2019era indiscussa delle citt\ue0 e su di esse si misurer\ue0 lo sviluppo delle nazioni. Per la prima volta, pi\uf9 della met\ue0 della popolazione mondiale vivr\ue0 nelle citt\ue0, in Europa oggi la cifra \ue8 gi\ue0 di oltre il 75%, e nei paesi in via di sviluppo raggiunger\ue0 velocemente il 50%. Il mondo si svilupper\ue0 sia attorno a grandi megalopoli da decine di milioni di abitanti, ma anche attorno a citt\ue0 metropolitane, a conurbazioni diffuse e ad armature di micropoli: all\u2019armatura urbana delle citt\ue0 globali si annoder\ue0, soprattutto in Europa, l\u2019armatura delle citt\ue0 di secondo livello, produttrici di visioni alternative rispetto all\u2019esplosione delle megalopoli. L\u2019armatura urbana europea di secondo livello \u2013 le piccole capitali, sempre pi\uf9 citt\ue0-porta \u2013 si delinea come annodata attorno a \u201ccitt\ue0 della cultura\u201d, nel senso di citt\ue0 non solo detentrici di risorse culturali profonde lasciate dal palinsesto della storia, ma anche produttrici di nuova cultura: le culture-based competition cities saranno, infatti, quelle citt\ue0 in grado di competere nel panorama internazionale attraverso la valorizzazione e la promozione della propria identit\ue0 culturale, sia consolidata che in evoluzione

Surface mesoscale pico–nanoplankton patterns at the main fronts of the Alboran Sea

© 2014 Elsevier B.V. The mesoscale (10-100. km, days-weeks) plays a key role in the Ocean's ecosystem structure and dynamics. This work compares the pico-nanoplankton patterns observed in the Alboran Sea (Western Mediterranean) during three oceanographic cruises. We analyse its response to different expressions of mesoscale circulation associated with the three major hydrodynamic features in the basin; namely the Northwestern Alboran Front (NWAF, surveyed in OMEGA-1 cruise), the Almeria-Oran Front (AOF, surveyed in OMEGA-2 cruise) and the Western Alboran Gyre (WAG, surveyed in BIOMEGA cruise). The first two surveys were carried out under the most typical quasi-stationary twin gyre conditions of the Alboran Sea, whereas the third cruise was performed after an eastward migration of the WAG. The analysis of pico and nanoplankton populations was carried out using flow cytometry. The patchiness observed in the three cruises indicates an association of phytoplankton peaks with the main frontal structures: abundances were higher in the NWAF/upwelling area in OMEGA-1, at the Mediterranean side of the AOF in OMEGA-2, and at a tongue of recent Atlantic Water west of the WAG in BIOMEGA. However, a more detailed analysis reveals that different factors explain the origin of the phytoplankton biomass in each front/cruise. Mixing processes at the Strait of Gibraltar and the subsequent advection of water properties into the Western Alboran Sea were the mechanisms responsible for the abundances observed in the NWAF. The highest concentrations observed in the AOF were related to the intrusion of Mediterranean Surface Waters to the north of the front. During the migrating WAG the phytoplankton distribution was influenced by the formation of a new gyre. The relation between phytoplankton and mesoscale dynamics is further explored in terms of vertical velocity diagnosis. In all cases, intense vertical motion is negatively correlated with the abundance of phytoplankton populations. This resulted from the intense geostrophic background flow associated with large vertical velocities, which drove low residence times of water mass properties and hence a weak biological response. Fast-repeated surveys made during the OMEGA-1 and OMEGA-2 cruises reveal that the surveyed hydrographic features are subjected to significant temporal variability. In this case, the impact on the biology is most evident at taxa level.This work was partially supported by the EU funded MAST project OMEGA (MAS3-CT95-0001) and by the BIOMEGA project, funded by the Spanish Marine Science and Technology Program (REN2002-04044-C02-02). P. Leon was financed by a FPI grant from the Spanish Ministry of Education and Science (BES-2003-1032)Peer Reviewe

Immersed boundary-finite element model of fluid-structure interaction in the aortic root

It has long been recognized that aortic root elasticity helps to ensure efficient aortic valve closure, but our understanding of the functional importance of the elasticity and geometry of the aortic root continues to evolve as increasingly detailed in vivo imaging data become available. Herein, we describe fluid-structure interaction models of the aortic root, including the aortic valve leaflets, the sinuses of Valsalva, the aortic annulus, and the sinotubular junction, that employ a version of Peskin's immersed boundary (IB) method with a finite element (FE) description of the structural elasticity. We develop both an idealized model of the root with three-fold symmetry of the aortic sinuses and valve leaflets, and a more realistic model that accounts for the differences in the sizes of the left, right, and noncoronary sinuses and corresponding valve cusps. As in earlier work, we use fiber-based models of the valve leaflets, but this study extends earlier IB models of the aortic root by employing incompressible hyperelastic models of the mechanics of the sinuses and ascending aorta using a constitutive law fit to experimental data from human aortic root tissue. In vivo pressure loading is accounted for by a backwards displacement method that determines the unloaded configurations of the root models. Our models yield realistic cardiac output at physiological pressures, with low transvalvular pressure differences during forward flow, minimal regurgitation during valve closure, and realistic pressure loads when the valve is closed during diastole. Further, results from high-resolution computations demonstrate that IB models of the aortic valve are able to produce essentially grid-converged dynamics at practical grid spacings for the high-Reynolds number flows of the aortic root

Sinking Jelly-Carbon Unveils Potential Environmental Variability along a Continental Margin

Particulate matter export fuels benthic ecosystems in continental margins and the deep sea, removing carbon from the upper ocean. Gelatinous zooplankton biomass provides a fast carbon vector that has been poorly studied. Observational data of a large-scale benthic trawling survey from 1994 to 2005 provided a unique opportunity to quantify jelly-carbon along an entire continental margin in the Mediterranean Sea and to assess potential links with biological and physical variables. Biomass depositions were sampled in shelves, slopes and canyons with peaks above 1000 carcasses per trawl, translating to standing stock values between 0.3 and 1.4 mg C m2 after trawling and integrating between 30,000 and 175,000 m2 of seabed. The benthopelagic jelly-carbon spatial distribution from the shelf to the canyons may be explained by atmospheric forcing related with NAO events and dense shelf water cascading, which are both known from the open Mediterranean. Over the decadal scale, we show that the jelly-carbon depositions temporal variability paralleled hydroclimate modifications, and that the enhanced jelly-carbon deposits are connected to a temperature-driven system where chlorophyll plays a minor role. Our results highlight the importance of gelatinous groups as indicators of large-scale ecosystem change, where jelly-carbon depositions play an important role in carbon and energy transport to benthic systems

The bed nucleus of stria terminalis and the amygdala as targets of antenatal glucocorticoids: implications for fear and anxiety responses

Rationale: Several human and experimental studies have shown that early life adverse events can shape physical and mental health in adulthood. Stress or elevated levels of glucocorticoids (GCs) during critical periods of development seem to contribute for the appearance of neurospyschiatric conditions such as anxiety and depression, albeit the underlying mechanisms remain to be fully elucidated. Objectives: The aim of the present study was to determine the long-term effect of prenatal erxposure to dexamethasone- DEX (synthetic GC widely used in clinics) in fear and anxious behavior and identify the neurochemical, morphological and molecular correlates. Results: Prenatal exposure to DEX triggers a hyperanxious phenotype and altered fear behavior in adulthood. These behavioral traits were correlated with increased volume of the bed nucleus of the stria terminalis (BNST), particularly the anteromedial subivision which presented increased dendritic length; in parallel, we found an increased expression of synapsin and NCAM in the BNST of these animals. Remarkably, DEX effects were opposite in the amygdala, as this region presented reduced volume due to significant dendritic atrophy. Albeit no differences were found in dopamine and its metabolite levels in the BNST, this neurotransmitter was substantially reduced in the amygdala, which also presented an up-regulation of dopamine receptor 2. Conclusions: Altogether our results show that in utero DEX exposure can modulate anxiety and fear behavior in parallel with significant morphological, neurochemical and molecular changes; importantly, GCs seem to differentially affect distinct brain regions involved in this type of behaviors.This study was supported by a grant from the Institute for the Study of Affective Neuroscience (ISAN). AJR is supported by a Fundação para a Ciência e Tecnologia (FCT) grant

Trauma mechanism and patient reported outcome in tibial plateau fractures with posterior involvement

Introduction: Posterior tibial plateau fractures (PTPF) have a high impact on functional outcome and the optimal treatment strategy is not well established. The goal of this study was to assess the relationship between trauma mechanism, fracture morphology and functional outcome in a large multicenter cohort and define possible strategies to improve the outcome. Methods: An international retrospective cohort study was conducted in five level-1 trauma centers. All consecutive operatively treated PTPF were evaluated. Preoperative imaging was reviewed to determine the trauma mechanism. Patient reported outcome was scored using the Knee injury and Osteoarthritis Outcome Score (KOOS). Results: A total of 145 tibial plateau fractures with posterior involvement were selected with a median follow-up of 32.2 months (IQR 24.1-43.2). Nine patients (6%) sustained an isolated posterior fracture. Seventy-two patients (49%) sustained a two-column fracture and three-column fractures were diagnosed in 64 (44%) patients. Varus trauma was associated with poorer outcome on the 'symptoms' (p = 0.004) and 'pain' subscales (p = 0.039). Delayed-staged surgery was associated with worse outcome scores for all subscales except 'pain'. In total, 27 patients (18%) were treated with posterior plate osteosynthesis without any significant difference in outcome. Conclusions: Fracture morphology, varus trauma mechanism and delayed-staged surgery (i.e. extensive soft-tissue injury) were identified as important prognostic factors on postoperative outcome in PTPF. In order to assess possible improvement of outcome, future studies with routine preoperative MRI to assess associated ligamentous injury in tibial plateau fractures (especially for varus trauma) are needed. (c) 2021 Elsevier B.V. All rights reserved