84 research outputs found
Conductive filament evolution dynamics revealed by cryogenic (1.5 K) multilevel switching of CMOS-compatible Al2O3/TiO2 resistive memories
This study demonstrates multilevel switching at 1.5 K of Al2O3/TiO2-x
resistive memory devices fabricated with CMOS-compatible processes and
materials. The I-V characteristics exhibit a negative differential resistance
(NDR) effect due to a Joule-heating-induced metal-insulator transition of the
Ti4O7 conductive filament. Carrier transport analysis of all multilevel
switching I-V curves show that while the insulating regime follows the space
charge limited current (SCLC) model for all resistance states, the conduction
in the metallic regime is dominated by SCLC and trap-assisted tunneling (TAT)
for low- and high-resistance states respectively. A non-monotonic conductance
evolution is observed in the insulating regime, as opposed to the continuous
and gradual conductance increase and decrease obtained in the metallic regime
during the multilevel SET and RESET operations. Cryogenic transport analysis
coupled to an analytical model accounting for the
metal-insulator-transition-induced NDR effects and the resistance states of the
device provide new insights on the conductive filament evolution dynamics and
resistive switching mechanisms. Our findings suggest that the non-monotonic
conductance evolution in the insulating regime is due to the combined effects
of longitudinal and radial variations of the Ti4O7 conductive filament during
the switching. This behavior results from the interplay between temperature-
and field-dependent geometrical and physical characteristics of the filament.Comment: 8 pages, 4 figure
Observation of Highly Nonlinear Resistive Switching of Al2O3/TiO2-x Memristors at Cryogenic Temperature (1.5 K)
In this work, we investigate the behavior of Al2O3/TiO2-x cross-point
memristors in cryogenic environment. We report successful resistive switching
of memristor devices from 300 K down to 1.5 K. The I-V curves exhibit negative
differential resistance effects between 130 and 1.5 K, attributed to a
metal-insulator transition (MIT) of the Ti4O7 conductive filament. The
resulting highly nonlinear behavior is associated to a maximum ION/IOFF ratio
of 84 at 1.5 K, paving the way to selector-free cryogenic passive crossbars.
Finally, temperature-dependant thermal activation energies related to the
conductance at low bias (20 mV) are extracted for memristors in low resistance
state, suggesting hopping-type conduction mechanisms.Comment: 4 pages, 4 figures, IEEE 14th Nanotechnology Materials & Devices
Conference (NMDC 2019
Patterns of belowground overyielding and fine-root biomass in native and exotic angiosperms and gymnosperms
Mixing tree species can lead to more productive forests, but how belowground productivity is affected by mixtures of trees of diverse phylogenetic and eco-evolutionary histories is unclear. Here, we examine how species origin and phylogeny affect belowground productivity in tree communities of varied richness and functional diversity. We measured standing fine-root biomass and annual fine-root production across 41 assemblages of 12 tree species, representing both angiosperms and gymnosperms originating from North America and Europe. Increasing functional diversity of mixtures stimulated overyielding of annual production but did not affect standing biomass. In general, annual productivity of mixtures of species that were less productive in monoculture had neutral (angiosperms) to positive (North American species: +16%) responses to mixing, whereas annual productivity of mixtures of species that were more productive in monoculture had neutral (European species) to negative (gymnosperms: â6%) responses to mixing. These differences translated into angiosperm mixtures overyielding in standing biomass by 16% but no effects of mixing on gymnosperm mixtures. The trends we observed between North American and European species annual production were reversed when considering standing biomass. European mixtures had 14% more standing biomass and North American mixtures had 10% less standing biomass than expected from monocultures. Our study offers a rare examination of the combined roles of origin and phylogeny in forest fine-root productivity, and suggests varied consequences of biodiversity change for forest belowground productivity based on composition. In North America, belowground productivity of young forests composed of angiosperms and native tree species may be more tightly linked to diversity than that of forests dominated by gymnosperms or European species. This suggests that increased diversity may lead to the greatest enhancement of belowground productivity in native, North American forests dominated by angiosperms, but also that declines in diversity may be felt most strongly in these forests as well
Violences sexuelles en milieu universitaire au QuĂ©bec : rapport de recherche de lâenquĂȘte ESSIMU
Cette recherche, intitulĂ©e « EnquĂȘte SexualitĂ©, SĂ©curitĂ© et Interactions en Milieu Universitaire(ESSIMU) : Ce quâen disent Ă©tudiant.es, enseignant.es et employĂ©.es », a permis dâĂ©tablir un portrait des violences sexuelles se dĂ©roulant en contexte universitaire au QuĂ©bec. Cette enquĂȘte dâenvergure provinciale regroupe 12 chercheures provenant des 6 universitĂ©s suivantes : UniversitĂ© du QuĂ©bec Ă MontrĂ©al, UniversitĂ© de MontrĂ©al, UniversitĂ© Laval, UniversitĂ© de Sherbrooke, UniversitĂ© du QuĂ©bec en Outaouais et UniversitĂ© du QuĂ©bec Ă Chicoutimi. LâĂ©quipe interdisciplinaire et interuniversitaire compte Ă©galement le Regroupement quĂ©bĂ©cois des centres dâaide et de lutte contre les agressions Ă caractĂšre sexuel et le Service aux collectivitĂ©s de lâUQAM. Afin de documenter les situations de violence sexuelle vĂ©cues en milieu universitaire (VSMU), lâĂ©quipe ESSIMU a rĂ©alisĂ© en 2016 une vaste Ă©tude auprĂšs de 9 284 rĂ©pondant.es dans 6 universitĂ©s quĂ©bĂ©coises francophones. Le questionnaire, administrĂ© en ligne, a permis de rendre compte dâun large Ă©ventail de manifestations de violence sexuelle vĂ©cues par lâensemble de la communautĂ© universitaire (Ă©tudiant ou travaillant Ă lâuniversitĂ©). La mesure de victimisation distinguait le harcĂšlement sexuel (comportements verbaux et non verbaux qui traduisent des attitudes insultantes, hostiles et dĂ©gradantes), les comportements sexuels non dĂ©sirĂ©s (comportements verbaux et non verbaux Ă caractĂšre sexuel, offensants, non dĂ©sirĂ©s ou non rĂ©ciproques, incluant la tentative de viol et lâagression sexuelle) et la coercition sexuelle (chantage en retour de rĂ©compenses)
Young mixed planted forests store more carbon than monoculturesâa meta-analysis
Although decades of research suggest that higher species richness improves ecosystem functioning and stability, planted forests are predominantly monocultures. To determine whether diversification of plantations would enhance aboveground carbon storage, we systematically reviewed over 11,360 publications, and acquired data from a global network of tree diversity experiments. We compiled a maximum dataset of 79 monoculture to mixed comparisons from 21 sites with all variables needed for a meta-analysis. We assessed aboveground carbon stocks in mixed-species planted forests vs. (a) the average of monocultures, (b) the best monoculture, and (c) commercial species monocultures, and examined potential mechanisms driving differences in carbon stocks between mixtures and monocultures. On average, we found that aboveground carbon stocks in mixed planted forests were 70% higher than the average monoculture, 77% higher than commercial monocultures, and 25% higher than the best performing monocultures, although the latter was not statistically significant. Overyielding was highest in four-species mixtures (richness range 2â6 species), but otherwise none of the potential mechanisms we examined (nitrogen-fixer present vs. absent; native vs. non-native/mixed origin; tree diversity experiment vs. forestry plantation) consistently explained variation in the diversity effects. Our results, predominantly from young stands, thus suggest that diversification could be a very promising solution for increasing the carbon sequestration of planted forests and represent a call to action for more data to increase confidence in these results and elucidate methods to overcome any operational challenges and costs associated with diversification
Climate affects neighbourâinduced changes in leaf chemical defences and tree diversityâherbivory relationships
1. Associational resistance theory predicts that insect herbivory decreases with increasing tree diversity in forest ecosystems. However, the generality of this effect and its underlying mechanisms are still debated, particularly since evidence has accumulated that climate may influence the direction and strength of the relationship between diversity and herbivory. 2. We quantified insect leaf herbivory and leaf chemical defences (phenolic compounds) of silver birch Betula pendula in pure and mixed plots with different tree species composition across 12 tree diversity experiments in different climates. We investigated whether the effects of neighbouring tree species diversity on insect herbivory in birch, that is, associational effects, were dependent on the climatic context, and whether neighbour-induced changes in birch chemical defences were involved in associational resistance to insect herbivory. 3. We showed that herbivory on birch decreased with tree species richness (i.e. associational resistance) in colder environments but that this relationship faded as mean annual temperature increased. 4. Birch leaf chemical defences increased with tree species richness but decreased with the phylogenetic distinctiveness of birch from its neighbours, particularly in warmer and more humid environments
UâPb zircon dating of post-obduction volcanic-arc granitoids and a granulite-facies xenolith from New Caledonia. Inference on Southwest Pacific geodynamic models
Tectonic history of northern New Caledonia Basin from deep offshore seismic reflection: Relation to late Eocene obduction in New Caledonia, southwest Pacific
International audienceNew, high-quality multichannel seismic reflection data from the western New Caledonia offshore domain allow for the first time the direct, continuous connection of seismic reflectors between the Deep Sea Drilling Project 208 drill hole on the Lord Howe Rise and the New Caledonia Basin. A novel seismic interpretation is hence proposed for the northern New Caledonia Basin stratigraphy, which places the Eocene/Oligocene unconformity deeper than previously thought and revisits the actual thickness of the pre-Oligocene sequences. A causal link is proposed between the obduction of the South Loyalty Basin over New Caledonia (NC) and the tectonic history of the northern New Caledonia Basin. Here it is suggested that as the South Loyalty Basin was being obducted during early Oligocene times, the NC Basin subsided under the effect of the overloading and underthrusted to accommodate the compressional deformation, which resulted in (1) the uplift of the northern Fairway Ridge and (2) the sinking of the western flank of New Caledonia. This event also had repercussions farther west with the incipient subsidence of the Lord Howe Rise
A discharge summary adapted to the frail elderly to ensure transfer of relevant information from the hospital to community settings: a model
<p>Abstract</p> <p>Background</p> <p>Elderly patients admitted to Geriatric Assessment Units (GAU) typically have complex health problems that require multi-professional care. Considering the scope of human and technological resources solicited during hospitalization, as well as the many risks and discomforts incurred by the patient, it is important to ensure the communication of pertinent information for quality follow-up care in the community setting. Conventional discharge summaries do not adequately incorporate the elements specific to an aging clientele.</p> <p>Objective</p> <p>To develop a discharge summary adapted to the frail elderly patient (D-SAFE) in order to communicate relevant information from hospital to community services.</p> <p>Methods</p> <p>The items to be included in the D-SAFE have been determined by means of a modified Delphi method through consultation with clinical experts from GAUs (11 physicians and 5 pharmacists) and the community (10 physicians and 5 pharmacists). The consensus analysis and the level of agreement among the experts were reached using a modified version of the RAND<sup>Ÿ</sup>/University of California at Los Angeles appropriateness method.</p> <p>Results</p> <p>A consensus was reached after two rounds of consultation for all the items evaluated, where none was judged «inappropriate». Among the items proposed, four were judged to be « uncertain » and were eliminated from the final D-SAFE, which was divided into two sections: the medical discharge summary (22 main items) and the discharge prescription (14 main items).</p> <p>Conclusions</p> <p>The D-SAFE was developed as a more comprehensive tool specifically designed for GAU inpatients. Additional research to validate its acceptability and practical impact on the continuity of care is needed before it can be recommended for use on a broader scale.</p
For the sake of resilience and multifunctionality, let's diversify planted forests!
As of 2020, the world has an estimated 290 million ha of planted forests and this number is continuously increasing. Of these, 131 million ha are monospecific planted forests under intensive management. Although monospecific planted forests are important in providing timber, they harbor less biodiversity and are potentially more susceptible to disturbances than natural or diverse planted forests. Here, we point out the increasing scientific evidence for increased resilience and ecosystem service provision of functionally and species diverse planted forests (hereafter referred to as diverse planted forests) compared to monospecific ones. Furthermore, we propose five concrete steps to foster the adoption of diverse planted forests: (1) improve awareness of benefits and practical options of diverse planted forests among land-owners, managers, and investors; (2) incentivize tree species diversity in public funding of afforestation and programs to diversify current maladapted planted forests of low diversity; (3) develop new wood-based products that can be derived from many different tree species not yet in use; (4) invest in research to assess landscape benefits of diverse planted forests for functional connectivity and resilience to global-change threats; and (5) improve the evidence base on diverse planted forests, in particular in currently under-represented regions, where new options could be tested
- âŠ