Search

The mechanism of comorbidity between alcohol dependence and depressive disorders are not well understood. This study investigated differences in the brain function of alcohol-dependent patients with and without depression by performing functional connectivity analysis using resting-state functional magnetic resonance imaging. A total of 29 alcohol-dependent patients with depression, 31 alcohol-dependent patients without depression and 31 healthy control subjects were included in this study. The resting-state functional connectivity between the amygdala and the whole brain was compared among the three groups. Additionally, we examined the correlation between functional connectivity values in significantly different brain regions and levels of alcohol dependence and depression. The resting-state functional connectivity between the left amygdala and the right caudate nucleus was decreased in alcohol-dependent patients. Additionally, the resting-state functional connectivity of the right amygdala with the right caudate nucleus, right transverse temporal gyrus, right temporal pole: superior temporal gyrus were also decreased. In alcohol-dependent patients with depression, not only was functional connectivity between the above brain regions significantly decreased, but so was functional connectivity between the right amygdala and the left middle temporal gyrus. Also, there was no significant correlation between the resting-state functional connectivity values in statistically significant brain regions and the levels of alcohol dependence and depression. The impairment of the functional connectivity of the amygdala with caudate nucleus and partial temporal lobe may be involved in the neural mechanism of alcohol dependence comorbidity depressive disorders. [ABSTRACT FROM AUTHOR]

Inelastic deformation of a high-strength martensitic steel (P91) is investigated using a strain gradient crystal plasticity model implemented using the finite element method. Voronoi tessellation is used to model the hierarchical structure, prior austenite grain (PAG)/packet/block, of the martensitic steel and the effect of PAG/packet/block size on the macro- and micro-scale mechanical response is analysed numerically. The role of lath interaction and the influence of dislocation type (statistically stored and geometrically necessary dislocations) are investigated. It is found that block size determines the overall mechanical response, consistent with the Hall-Petch relation, while packet and block diameters influence the microplastic strain distribution. A modified Hall-Petch relation is examined which provides a relationship between material flow strength and block diameter (size) which holds for a wide range of initial dislocation densities and block diameters. • Block diameter controls size dependent behaviour of flow stress in martensitic steel. • A new modified Hall-Petch relation is introduced which holds for a wide range of initial dislocation density and block size. • The effect of lath misorientation on the predicted tensile response is negligible. [ABSTRACT FROM AUTHOR]

Plastic deformation of aluminium alloy AA6061 under tension and compression is investigated using a strain gradient crystal plasticity model implemented with the finite element method. This approach takes into account the microstructure as determined experimentally by electron backscatter diffraction (EBSD). The asymmetry of stress strain curves in loading of tension and compression (TC) is revealed for the FCC crystal structure. Plastic slip on activated slip systems leads to lattice rotation of crystal matrix and particles towards specific orientations, resulting in variation of moduli. The evolution of two different types of dislocations, statistically stored dislocations (SSD) and geometrically necessary dislocations (GND), is investigated to reveal the TC asymmetry due to slip resistance. It is found that the TC asymmetry at the yield strain is caused by lattice rotation of both crystal matrix and particles. When strain increases, the TC asymmetry is due to a combination of lattice rotation of crystal matrix and particle and variation of the GND density. As particle content increases, the TC asymmetry is mainly attributed to lattice rotation of particles at large strain. • Tension/Compression (TC) of Al alloy was analysed with a crystal plasticity model. • Lattice rotation of particles makes a significant contribution to the TC asymmetry. • Compression leads to high GND density and rotation towards low-modulus orientation. [ABSTRACT FROM AUTHOR]

Discrete dislocation plasticity simulations are performed to investigate the static frictional behavior of a metal asperity on a large single crystal, in contact with a rigid platen. The focus of this study is on understanding the relative importance of contact slip opposed to plasticity in a single asperity at the micrometer size scale, where plasticity is size dependent. Slip of a contact point is taken to occur when the shear traction exceeds the normal traction at that point times a microscopic friction coefficient. Plasticity initiates through the nucleation of dislocations from Frank-Read sources in the metal and is modeled as the collective motion of edge dislocations. Results show that plasticity can delay or even suppress full slip of the contact. This generally happens when the friction coefficient is large. However, if the flattening depth is sufficiently large to induce nucleation of a large dislocation density, slip is suppressed even when the friction coefficient is very small. This study also shows that when self-similar asperities of different size are flattened to the same depth and subsequently loaded tangentially, their frictional behavior appears size independent. However, when they are submitted to the same contact pressure, smaller asperities slip while larger asperities deform plastically. [ABSTRACT FROM AUTHOR]

Discrete dislocation plasticity simulations are performed to investigate the role of interaction between neighboring asperities on the contact pressure induced by a rigid platen on a rough surface. The rough surface is modeled as an array of equispaced asperities with a sinusoidal profile. The spacing between asperities is varied and the contact pressure necessary to flatten the surface to a given strain is computed. Plasticity in the asperities and in the crystal below is described by the collective glide of dislocations of edge character. Results show that the mean contact pressure necessary to flatten closely spaced asperities is larger than that required to flatten widely separated asperities. A small dependence on asperity density is already observed for a purely elastic material, but it is enhanced for small asperities, in the presence of dislocation plasticity. Plastic strain gradients, dislocation limited plasticity and interaction between neighboring plastic zones all contribute to what we will call the asperity density effect. Since dislocation limited plasticity plays a dominant role, the asperity density effect will mainly be relevant for surfaces having small asperity roughness. [ABSTRACT FROM AUTHOR]

Abstract: The texture evolution in commercial-purity aluminum (AA1070) processed by accumulative roll-bonding (ARB) is investigated with the aid of X-ray diffraction and crystal plasticity modeling. The experimental results indicate strong texture gradients through the sheet thickness, from rolling-type textures with orthorhombic symmetry at the center to shear-type textures with monoclinic symmetry near the surface. The experimental textures are reproduced well by polycrystal plasticity modeling carried out with deformation histories from finite element simulations. The observations of a relatively strong {4411}〈11118〉 component at the center and a {001}〈110〉 component at the surface are attributed to their higher orientation stability than the other rolling- and shear-type orientations. Examination of the average through-thickness textures suggests that the ARB technique may not be an effective means to develop apparent {111}〈u v w〉 components and thus to enhance the normal anisotropy of plasticity of the bulk sheet materials. [Copyright &y& Elsevier]

The objective of this work is to investigate the plastic deformation and associated microstructural evolution and damage in a martensitic steel at multiple length scales, using a combination of finite-element (FE) modelling and experimental measurements. A multiscale model is developed to predict damage evolution in the necked region of a uniaxial tensile test specimen. At the macroscale, a von Mises plasticity FE model in conjunction with a Gurson-Tvergaard-Needleman damage model is used to predict the global deformation and damage evolution. A physically-based crystal plasticity model, incorporating a damage variable is used to investigate the microscale plastic deformation behaviour and the changes in crystal orientation under large strains. The model predicts that slip bands form at the onset of plastic deformation and rotate to become almost parallel to the loading direction at large strain. In the necked region, the initially randomly orientated microstructure develops texture, brought about by inelastic deformation and lattice rotation towards the stable [011] orientation. The predicted crystal orientations and misorientation distribution are in good agreement with measurements obtained through electron backscatter diffraction in the centre of the necked region of the tensile test specimens. The experimental and modelling techniques developed in this work can be used to provide information on the evolution of plastic deformation and damage as well as the orientation-dependent crack initiation and microstructural evolution during large deformation of engineering materials. • Microstructure and damage evolution of a martensitic steel have been analysed using a multiscale finite element model. • The model has been validated experimentally over multiple length scales using multiple techniques. • The model predicts crystal orientation consistent theoretical predictions of orientation change under uniaxial loading. • Large plastic deformations can lead to generation or annihilation of high angle grain boundaries. [ABSTRACT FROM AUTHOR]

• Arbuscular mycorrhizal fungi reduced soil carbon (C) and nitrogen (N) stocks. • Neither elevated temperature nor N deposition alter the response of soil C and N stocks to AM fungi. • AM fungi can mitigate the negative effect of increasing N accumulation on ecosystem stability. Arbuscular mycorrhizal (AM) fungi are key players in the soil carbon (C) and nitrogen (N) cycles; on the one hand, AM fungi have been influenced by global changes, while on the other hand, they are involved in shaping the future climate. However, few field studies have combined AM fungi with both elevated temperatures and N deposition to examine their potential combined effects on the stocks of soil C and N in temperate meadow ecosystems. A 5-year experiment was conducted to explore the effects of AM fungal reductions on soil C and N stocks under elevated temperatures and N deposition. The stock of soil C and N and the C:N ratio were measured. The results showed that AM fungi significantly reduced soil C stocks by 8.5% across all treatment combinations compared to the AM fungi suppression treatment, and slight soil C accumulation was detected across the five years. The response of the soil C stocks was not influenced by elevated temperatures and N deposition simultaneously. The soil N stocks in the treatments without AM fungal suppression were, on average, 9.7% lower across all treatments than those in the AM fungal suppression treatment. AM fungi, elevated temperatures, and N deposition did not affect the soil C:N ratio. The robust decreases in soil C and N stocks caused by AM fungi observed here, even when combined with other global changes, suggest that AM fungi might accelerate soil C losses in temperate meadow ecosystems; however, there is a strong potential for reduced soil N accumulations to mitigate the negative impact of increasing N deposition on the stability of grassland ecosystems under future global changes. Overall, our results highlight that the effect of AM fungi on soil C and N stocks has a high resistance to global warming and N deposition in temperate meadow ecosystems. [ABSTRACT FROM AUTHOR]

The in-situ neutron diffraction technique, in combination with both the full-field crystal elasto-viscoplastic finite element model and microstructural characterization, was used to study the deformation-induced damage anisotropy in a commercial Al alloy, subjected to uniaxial tensile and cyclic loading. The simulations capture well the crystallographic-orientation-dependent lattice strain behavior. The hard grains, e.g. those orientated with the <111> and <422> orientations parallel with the uniaxial loading direction (LD), feature large Taylor factors and seem more prone to form damage-related band structures. Their effective elastic moduli decrease with the accumulation of damage, which are different from the soft grains orientated with the <200> orientation along the LD. Correlation between the distribution of voids and that of the residual lattice strain developed after failure may exist. The maximum tensile type residual lattice strain observed after failure may be resulted from the band structure formed in the hardest <111> grains. It was revealed that the band structure triggered by the hard particles could be one of sources of damage. In addition, while the specimen was obviously damaged, a fast stress relief was evidenced after unloading from the tension, especially at the beginning of unloading. Our present investigations provide a novel method for exploring the damage mechanisms of polycrystalline materials during plastic deformation. Image, graphical abstract [ABSTRACT FROM AUTHOR]

The use of articulate-filtering facemasks (hereinafter referred to as facemasks) as a defensive measure to reduce air pollution exposure has not been adopted by the Chinese public. Our descriptive investigation reveals hidden barriers other than facemask expenditure that determine the choice to use facemasks. Whether discomfort or inconvenience are the major sources of inaction is largely unknown. By conducting a choice experiment, we observed how people made trade-offs between the costs and health benefits of facemask use in monetary terms, defined as willingness to pay (WTP). The results first demonstrated that discomfort and inconvenience majorly account for the inaction of facemask use, as they are, on average, valuated 6.94 and 24.00 times the facemask expenditures for year 2017 and 2022, respectively. Second, we estimated the threshold of lung cancer mortality above which the cost of facemask use weighs less than the health benefits, which implies a trigger point of health protection behavior. Third, we predicted, in the contexts of air pollution in 2017 and 2021 at the city level, that people refused to wear facemasks if they perceived lung cancer mortality as the one presented in current scientific assessments. We suggested the need to study the subjective reality of public defensive measures if the objectives of air quality and, more generally, environmental management are to be achieved. • The particulate-filtering facemask use was not advocated during the pollution episodes. • People experienced physiological and psychological discomfort and inconvenience when wearing a facemask. • The hidden cost was substantially larger than facemask expenditure. • The level of lung cancer mortality above which the health benefits outweighed the costs of facemask use is estimated. • People would refuse to wear facemasks in the context of air pollution at the city level in 2017. [ABSTRACT FROM AUTHOR]

• The oscillation frequencies of an edge skyrmion in circular nano-pillars are analytically derived. • The size of the sample to produce isolated edge skyrmion oscillation is relatively small. • The oscillation frequencies strongly depend on the eccentricity and the perimeter of the elliptical nanopillar. The magnetic skyrmions have received a lot of attention because they have potential applications in spin torque nano-oscillators. In this paper, we numerically and analytically study the dynamics of edge skyrmions in circular nano-pillar oscillators with perpendicular magnetic anisotropy (PMA) free layer and spin polarizer. Numerical simulations demonstrate that a steady edge skyrmion oscillation mode with GHz frequency can be driven by spin currents and magnetic fields. The oscillation frequencies in circular nano-pillars with different radius are analytically derived, which agrees well with the numerical results. In addition, the steady oscillations of edge skyrmions are also observed in elliptical nano-pillars, in which the oscillation frequencies strongly depend on the eccentricity and perimeter of the elliptical nanopillar. It is found that the oscillation frequency of this edge skyrmion can range from 1 GHz to 6.7 GHz. The line width is about 55 MHz. [ABSTRACT FROM AUTHOR]