Real-world complex systems may be mathematically modeled as graphs, revealing properties of the system. Here we study graphs of functional brain organization in healthy adults using resting state ...functional connectivity MRI. We propose two novel brain-wide graphs, one of 264 putative functional areas, the other a modification of voxelwise networks that eliminates potentially artificial short-distance relationships. These graphs contain many subgraphs in good agreement with known functional brain systems. Other subgraphs lack established functional identities; we suggest possible functional characteristics for these subgraphs. Further, graph measures of the areal network indicate that the default mode subgraph shares network properties with sensory and motor subgraphs: it is internally integrated but isolated from other subgraphs, much like a “processing” system. The modified voxelwise graph also reveals spatial motifs in the patterning of systems across the cortex.
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► Areal and modified voxelwise graph definitions are proposed ► Subgraphs reflect known and unknown brain systems ► Default mode, sensory, and motor systems share network properties ► Functional systems are patterned across the cortex with spatial regularities
But L’objectif de cette étude prospective, observationnelle (ODYSSÉE) était de comparer la durée de maintien de traitement sans modification (arrêt, substitution ou adjonction d’un traitement) chez ...des patients diabétiques de type 2, suivis par des médecins généralistes et débutant une bithérapie soit par metformine et sitagliptine (MetSita) soit par metformine et un sulfamide (MetSu) Patients et méthodes L’étude a été proposée à des médecins généralistes identifiés à partir d’un échantillon national aléatoire et traitant des patients diabétiques. Les médecins participants ont recruté tout patient remplissant les critères d’éligibilité suivants : âge ≥ 18 ans, diabétique de type 2, débutant une bithérapie MetSita ou MetSu pendant les 8 semaines avant l’inclusion. Les patients inclus ont été suivis jusqu’à 3 ans. Le suivi et les éventuelles modifications de traitement correspondaient à la pratique habituelle du médecin Résultats 1 874 patients ont été inclus dans le groupe MetSita et 733 patients dans le groupe MetSu. À l’inclusion, les deux groupes étaient comparables avec de petites différences en ce qui concerne l’âge moyen (62,4 vs 64,2 ans), l’IMC (30,3 vs 29,6 kg/m²) et l’ancienneté du diabète (6,4 vs 7,0 ans) ; l’HbA1c était comparable (7,5 % vs 7,6 %). La durée médiane de maintien de traitement était significativement plus longue ( p < 0,0001 ; test de logrank) dans le groupe MetSita (43,2 mois) que dans le groupe MetSu (20,2 mois). La baisse d’HbA1c sous traitement était comparable dans les deux groupes (– 0,6 %). Des hypoglycémies symptomatiques sont survenues sous traitement chez 9,7 % des patients du groupe MetSita et chez 21,0 % du groupe MetSu. Conclusion Une bithérapie par MetSita était maintenue sans modification de traitement plus longtemps qu’une bithérapie par MetSu. De plus, la survenue d’hypoglycémies symptomatiques était plus faible dans le groupe MetSita que dans le groupe MetSu, associée à un contrôle de la glycémie similaire. Déclaration d’intérêt Les auteurs déclarent avoir un intérêt avec un organisme privé, industriel ou commercial en relation avec le sujet présenté. Étude réalisée avec le soutien de MSD.
In this work, strength and microstructural evolution of superalloy Inconel 718 (IN718) are characterized as a function of the initial microstructure created via direct metal laser melting (DMLM) ...additive manufacturing (AM) technology along with subsequent hot isostatic pressing (HIP) and heat treatments as well as wrought processing. Stress-strain curves are measured in tension and compression from room temperature to 550 °C and crystallographic texture is characterized using neutron diffraction. Furthermore, a recently developed crystal plasticity model incorporating the effects of precipitates is extended to interpret the temperature dependent deformation behavior of the alloy. The model accounts for solid solution, precipitate shearing, and grain size and shape contributions to initial slip resistance, which evolves with a dislocation density-based hardening law considering latent hardening, while non-Schmid effects are taken into account in the activation stress. Part of the experimental data is used for calibration of the model, while the rest is used for experimental validation of the model. It is shown that the model is capable of modeling the data with accuracy. Based on the comparison of the data and model predictions, it is inferred that the grain structure and texture give rise to plastic anisotropy of the alloy, while its tension-compression asymmetry results from non-Schmid effects and latent hardening.
•Mechanical response of alloy IN718 is studied as a function of the initial microstructure created by variation in processing.•The room and elevated temperature stress-strain responses are provided for the alloy.•An elasto-plastic crystal plasticity model is extended to predict temperature-dependent deformation of the alloy.•The model predicts hardening and texture evolution for several test directions across the studied temperature range.•The model reveals that anisotropy stems from grain structure, while asymmetry from non-Schmid activation and latent hardening.
Tools for three-dimensional elemental characterization are available on length scales ranging from individual atoms, using electrons as a probe, to micrometers with X-rays. However, for larger ...volumes up to millimeters or centimeters, quantitative measurements of elemental or isotope densities were hitherto only possible on the surface. Here, a novel quantitative elemental characterization method based on energy-resolved neutron imaging, utilizing the known neutron absorption cross sections with their 'finger-print' absorption resonance signatures, is demonstrated. Enabled by a pixilated time-of-flight neutron transmission detector installed at an intense short-pulsed spallation neutron source, for this demonstration 3.25 million state-of-the-art nuclear physics neutron transmission analyses were conducted to derive isotopic densities for five isotopes in 3D in a volume of 0.25 cm
. The tomographic reconstruction of the isotope densities provides elemental maps similar to X-ray microprobe maps for any cross section in the probed volume. The bulk isotopic density of a U-20Pu-10Zr-3Np-2Am nuclear transmutation fuel sample was measured, agrees well with mass-spectrometry and is evidence of the accuracy of the method.
A time-interleaved multichannel analog-to-digital converter (ADC) achieves high sampling rates with the drawback of additional distortions caused by channel mismatches. In this paper, we consider the ...dependency of the signal-to-noise-and-distortion ratio (SINAD) on the combination of several different channel mismatch effects. By using either explicitly given mismatch parameters or given parameter distributions, we derive closed-form equations for calculating the explicit or the expected SINAD for an arbitrary number of channels. Furthermore, we extend the explicit SINAD by the impact of timing jitter. We clarify how channel mismatches interact and perform a worst case analysis of the explicit SINAD for individual mismatch errors. We also show that equations describing the expected SINAD of individual mismatch errors are special cases of our general formulation. We indicate how to use the expected SINAD for finding efficient optimization priorities and demonstrate the importance of worst case analyses.
This work adapts a recently developed multi-level constitutive model for polycrystalline metals that deform by a combination of elasticity, crystallographic slip, and deformation twinning to ...interpret the deformation behavior of alloy WE43 as a function of strain rate. The model involves a two-level homogenization scheme. First, to relate the grain level to the level of a polycrystalline aggregate, a Taylor-type model is used. Second, to relate the aggregate level response at each finite element (FE) integration point to the macro-level, an implicit FE approach is employed. The model features a dislocation-based hardening law governing the activation stress at the slip and twin system level, taking into account the effects of temperature and strain rate through thermally-activated recovery, dislocation debris formation, and slip-twin interactions. The twinning model employs a composite grain approach for multiple twin variants and considers double twinning. The alloy is tested in simple compression and tension at a quasi-static deformation rate and in compression under high strain rates at room temperature. Microstructure evolution of the alloy is characterized using electron backscattered diffraction and neutron diffraction. Taking the measured initial texture as inputs, it is shown that the model successfully captures mechanical responses, twinning, and texture evolution using a single set of hardening parameters, which are associated with the thermally activated rate law for dislocation density across strain rates. The model internally adjusts relative amounts of active deformation modes based on evolution of slip and twin resistances during the imposed loadings to predict the deformation characteristics. We observe that WE43 exhibits much higher strain-hardening rates under high strain rate deformation than under quasi-static deformation. The observation is rationalized as primarily originating from the pronounced activation of twins and especially contraction and double twins during high strain rate deformation. These twins are effective in strain hardening of the alloy through the texture and barrier hardening effects.
•A multi-level grain-to-polycrystalline aggregate-to-macro-level model, T-CPFE, is adapted for modeling of WE43.•EBSD, neutron diffraction, and mechanical testing data are used to calibrate and validate the model.•Anisotropy in mechanical response induced by microstructural evolution is predicted.•Role of deformation modes on the mechanical behavior and texture evolution is discussed.•Formation of contraction twins is identified to increase the rate of strain hardening under high strain rate deformation.
This paper presents an analytic model for the analysis of co-planar turbine fences that partially span the width of a channel in which the flow is driven by a sinusoidally oscillating driving head. ...The thrust presented by the turbines reduces the flow rate through the channel leading to a solution for overall power that is dependent upon turbine resistance and flow blockage as well as on channel characteristics. We introduce a return parameter, in terms of power per turbine area, to assess optimum turbine fence deployment for a given channel. We find that the optimal deployment rests on a universal curve independent of the channel characteristics, and that these characteristics – namely the integrated channel bed friction and a modified channel Froude number – move the optimum along this curve. We find that blockage considerations play a large role in the performance of a tidal farm – its achievable power, optimal return, channel flow rate reduction and device thrust – and that the scales of blockage must be considered even when designing relatively unblocked farms. The impact of the channel characteristics on the optimal arrangement, alongside environmental constraints that may limit permissible flow blockage, are quantified and discussed.
In this work, lamellar composite sheets combining one of two fully hexagonal magnesium-lithium alloys (Mg–4Li and Mg–5Li wt%) and pure niobium (Nb) are manufactured via accumulative roll bonding ...(ARB). With extreme straining of over two true strain, the individual layers were refined to 200 μm. The strength differential between co-deforming phases with strain is characterized to be low enough to facilitate bonding without instabilities. Additionally, homogeneity in deformation was enhanced by intermediate annealing, especially for the Mg-xLi phase. Diffraction methods and polycrystal modeling are employed to study the microstructure and texture evolution of the individual phases after each subsequent ARB pass. Characterization by electron backscatter diffraction and neutron diffraction reveals substantial changes in microstructure and texture in both phases and very little deformation twinning in the Mg-xLi phase. Evolution of grain morphology and the number of grains that span a layer with ARB and annealing are determined and discussed. To link texture evolution to slip-based deformation mechanisms during the processing, a multiscale polycrystalline model of the two-phase Mg–4Li/Nb composite was developed, which included a relative directional compliance (RDC) method to account for anisotropic interactions in the phases, allowing appropriate slip sensitivity to dislocation density based hardening on the multiple slip modes in Mg–4Li and in Nb. The model indicates that the deformation of the Mg–4Li phase during ARB cycles was accommodated by more basal and progressively smaller amounts of prismatic , pyramidal <c+a>, and twinning than previously reported for rolling of Mg–4Li. The experimental textures cannot be entirely explained by grain shape and an increase in pyramidal and prismatic slip resistance are required as expected with a small grain size. Consistent with measurements, the model predicts that c-axis of the Mg–4Li phase tilts from the sheet's normal direction towards the rolling direction, and that the strong γ-fiber and the unusually weak α-fiber should develop in Nb with large ARB straining of the Mg-xLi/Nb composites.
Combined in-situ neutron diffraction measurements during post-processing heat treatment and thermo-mechanical crystal plasticity finite element (CPFE) simulations were utilized to study the residual ...phase stress development in the two-phase microstructure of an additively manufactured (AM) 304L stainless steel. The steel, fabricated via the laser engineering net shaping technique, has a microstructure comprising primarily of the austenite phase, with ∼ 2.5% ferrite phase by volume fraction. The post-build material was heated to greater than 1300 K and neutron diffraction data was recorded during heating and cooling. Specifically, the evolution of lattice strains in the individual phases were measured with temperature and the corresponding coefficients of thermal expansion (CTEs) calculated. The dislocation densities, phase fractions and textures, before and after heat treatment, were also measured. CPFE simulations were performed to study the interplay of the stress-free thermal strains and the mechanical strains in inducing inter-granular residual stresses in individual phases. The simulations confirmed the presence of process induced inter-granular residual stress primarily in the ferrite phase of the as-built AM material. Comparison of the relevant simulation data with experiments indicate that model predictions of the lattice strains and CTEs in both phases, as well as the inter-granular residual phase stress and pressure in the ferrite phase are in qualitative agreement with the experimental measurements and calculations.
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