11,979 research outputs found
Graphene kirigami as a platform for stretchable and tunable quantum dot arrays
The quantum transport properties of a graphene kirigami similar to those
studied in recent experiments are calculated in the regime of elastic,
reversible deformations. Our results show that, at low electronic densities,
the conductance profile of such structures replicates that of a system of
coupled quantum dots, characterized by a sequence of minibands and stop-gaps.
The conductance and I-V curves have different characteristics in the distinct
stages of elastic deformation that characterize the elongation of these
structures. Notably, the effective coupling between localized states is
strongly reduced in the small elongation stage, whereas in the large elongation
regime the development of strong, localized pseudomagnetic field barriers can
reinforce the coupling and reestablish resonant tunneling across the kirigami.
This provides an interesting example of interplay between geometry and
pseudomagnetic field-induced confinement. The alternating miniband and
stop-gaps in the transmission lead to I-V characteristics with negative
differential conductance in well defined energy/doping ranges. These effects
should be stable in a realistic scenario that includes edge roughness and
Coulomb interactions, as these are expected to further promote localization of
states at low energies in narrow segments of graphene nanostructures.Comment: 10 pages, 10 figure
How to break access control in a controlled manner
The Electronic Medical Record (EMR) integrates heterogeneous information within a Healthcare Institution stressing the need for security and access control. The Biostatistics and Medical Informatics Department from Porto Faculty of Medicine has recently implemented a Virtual EMR (VEMR) in order to integrate patient information and clinical reports within a university hospital. With more than 500 medical doctors using the system on a daily basis, an access control policy and model were implemented. However, the healthcare environment has unanticipated situations (i.e. emergency situations) where access to information is essential. Most traditional policies do not allow for overriding. A policy that allows for Break-The-Glass (BTG) was implemented in order to override access control whilst providing for non-repudiation mechanisms for its usage. The policy was easily integrated within the model confirming its modularity and the fact that user intervention in defining security procedures is crucial to its successful implementation and use
Numerical solution of a two state variable contingent claims mortgage valuation modelªᵇ
Previously published work on mortgage component valuation has concentrated on the US market and is inapplicable to some of the mortgage arrangements outside of that market. We model UK repayment mortgages with capped Mortgage Insurance Guarantees (which affect both the equilibrium lending rates and the lender's residual exposure). A contingent claims framework is developed, with an explicit finite differences solution. Then the mortgage components are valued, assuming arrangement fees but no prepayment penalties, under various scenarios, and also under equilibrium conditions: The transformation of the original PDE, and the details of the finite difference solution are given, along with graphical sensitivities of the mortgage participants (including the options held or written by the borrower, the insurer, and the lender) to interest rates and house pricesinfo:eu-repo/semantics/publishedVersio
Peralkaline and alkaline magmatism of the Ossa-Morena zone (SW Iberia): Age, source, and implications for the Paleozoic evolution of Gondwanan lithosphere
The Ossa-Morena zone in SW Iberia represents a section of the northern margin of West Gondwana that formed part of a Cordilleran-type orogenic system during the Neoproterozoic (Cadomian orogeny). The crustal section in this zone preserves the record of rifting that led to the opening of the Rheic Ocean in the early Paleozoic and the collision of Gondwana and Laurussia in the late Paleozoic (Variscan orogeny). We present U-Pb zircon data from three alkaline to peralkaline syenites that intruded Neoproterozoic and Cambrian strata and give crystallization ages ranging between ca. 490 Ma and 470 Ma. Lu/Hf isotopic data from these zircons give positive initial εHf values (0 ≤ εHf(t) ≤ +11.5) that approach the model values for the depleted mantle at the time of crystallization. This suggests that a significant proportion of the magma was derived from the mantle, with limited mixing/assimilation with crustal-derived melts. Alkaline/peralkaline magmatic suites of similar age and chemical composition intruded other sections of the northern margin of West Gondwana and along the boundaries of the continental blocks that today make up Iberia. These blocks are further characterized by the presence of high-pressure metamorphic belts that formed during accretion and subsequent collision of peri-Gondwanan domains against Laurussia during the Devonian and Carboniferous (Variscan orogeny). Our U-Pb and Lu-Hf data set indicates that during the Cambrian−Ordovician transition, lithosphere extension reached a stage of narrow intracontinental rifting, where deeply sourced magmas, probably coming from the lower crust and/or the upper mantle, intruded continental upper crust across various sections of previously stretched crust. We propose that necking of the Gondwana lithosphere into several continental microblocks with fertile mantle beneath them compartmentalized extension (multiblock model), which favored the onset of early Paleozoic peralkaline and alkaline magmas. The boundaries of microblocks represent zones of inherited crustal weakness that were later reactivated during the late Paleozoic as major accretionary faults related to the amalgamation of Pangea during the Variscan orogeny. Our dynamic model provides an explanation for the unusual spatial relationship between peralkaline and alkaline igneous provinces (usually shallow in the crust) and the occurrence of high-pressure rocks. Our observations suggest that Cordilleran-type orogens subjected to extension after long-lived subduction can develop wide continental platforms that feature multiple continental blocks. In addition, the formation of sequenced high-pressure belts in collisional orogens can be explained as the ultimate consequence of multiple necking events within continental lithosphere during previous collapse of a Cordilleran-type orogen
Drought-induced photosynthetic inhibition and autumn recovery in two Mediterranean oak species (Quercus ilex and Quercus suber)
Responses of leaf water relations and photosynthesis
to summer drought and autumn rewetting were studied
in two evergreen Mediterranean oak species, Quercus ilex
spp. rotundifolia and Quercus suber. The predawn leaf water
potential (ΨlPD), stomatal conductance (gs) and photosynthetic
rate (A) at ambient conditions were measured seasonally
over a 3-year period. We also measured the photosynthetic
response to light and to intercellular CO2 (A/PPFD and A/
Ci response curves) under water stress (summer) and after recovery
due to autumn rainfall. Photosynthetic parameters,
Vcmax, Jmax and triose phosphate utilization (TPU) rate, were
estimated using the Farquhar model. RuBisCo activity, leaf
chlorophyll, leaf nitrogen concentration and leaf carbohydrate
concentration were also measured. All measurements
were performed in the spring leaves of the current year. In
both species, the predawn leaf water potential, stomatal conductance
and photosynthetic rate peaked in spring, progressively
declined throughout the summer and recovered upon
autumn rainfall. During the drought period, Q. ilex maintained
a higher predawn leaf water potential and stomatal
conductance than Q. suber. During this period, we found that
photosynthesis was not only limited by stomatal closure, but
was also downregulated as a consequence of a decrease in the
maximum carboxylation rate (Vcmax) and the light-saturated
rate of photosynthetic electron transport (Jmax) in both species.
The Vcmax and Jmax increased after the first autumnal
rains and this increase was related to RuBisCo activity, leaf
nitrogen concentration and chlorophyll concentration. In addition,
an increase in the TPU rate and in soluble leaf sugar
concentration was observed in this period. The results obtained
indicate a high resilience of the photosynthetic apparatus
to summer drought as well as good recovery in the
following autumn rains of these evergreen oak species
Beetroot as a source of natural dyes for ham
Beetroot (Beta vulgaris L.) was subjected to extraction procedures in order to obtain the
respective extracts containing the natural dyes and subjected to cytotoxicity assays in AGS cell line.
Encapsulation of the extracts in nanosystems based on soybean lecithin and maltodextrin was
performed. Lyophilized extracts before and after encapsulation in maltodextrin were applied in the
formulation of leg ham and used in pilot scale of production. The colour of ham samples from the
different assays was evaluated visually and by colorimetry.Dias, S.; Pereira, D.M.; Castanheira, E.M.S.; Fortes, A.G.; Pereira, R.; Gonçalves, a.M.S.T. Beetroot as a Source of Natural Dyes for Ham. Proceedings 2019, 41, 82. https://doi.org/10.3390/ecsoc-23-0662
Laser-fabricated porous alumina membranes (LF-PAM) for the preparation of metal nanodot arrays
We report on an efficient photonic-based method to prepare nanodot array of
functional materials, independently of the nature of the substrate.Comment: Small (2008) Accepte
Workshop on meibomian gland dysfunction
Federal University of São Paulo Department of OphthalmologyUniversidade de São Paulo epartment of Ophthalmology, Otorhinolaryngology, and Head and Neck SurgerySchepens Eye Research InstituteHarvard Medical School Department of OphthalmologyTear Film & Ocular Surface SocietyUNIFESP, Department of OphthalmologySciEL
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