Phase Field Modeling of Fracture and Stress Induced Phase Transitions

We present a continuum theory to describe elastically induced phase transitions between coherent solid phases. In the limit of vanishing elastic constants in one of the phases, the model can be used to describe fracture on the basis of the late stage of the Asaro-Tiller-Grinfeld instability. Starting from a sharp interface formulation we derive the elastic equations and the dissipative interface kinetics. We develop a phase field model to simulate these processes numerically; in the sharp interface limit, it reproduces the desired equations of motion and boundary conditions. We perform large scale simulations of fracture processes to eliminate finite-size effects and compare the results to a recently developed sharp interface method. Details of the numerical simulations are explained, and the generalization to multiphase simulations is presented

Mediation of the association between vascular risk factors and depressive symptoms by c-reactive protein: Longitudinal evidence from the UK Biobank

People with vascular risk factors (VRFs) are at higher risk for depressive symptoms. Given recent findings implicating low-grade systemic inflammation in both vascular and mental health, this study examined the extent to which the VRF–depressive symptom association might be mediated by low-grade systemic inflammation. To this end, we analysed longitudinal data of 9,034 participants from the UK Biobank (mean age = 56.54 years), who took part in three consecutive assessments over the course of about 8 years. Cumulative VRF burden at baseline was defined as the presence of 5 VRFs (hypertension, obesity, hypercholesterolemia, diabetes, and smoking). Low-grade systemic inflammation was assessed using serum-derived C-reactive protein (CRP) and depressive symptoms were measured using the Patient Health Questionnaire-9 (PHQ-9). We performed mediation models using longitudinal data and a path analytic framework, while controlling for age, gender, racial-ethnic background, socioeconomic status, and baseline mood. VRFs at baseline showed a small association with higher depressive symptoms at follow-up (total effect = 0.014, 95% CI [0.007; 0.021]). CRP mediated this association (indirect effect = 0.003, 95% CI [0.001; 0.005]) and accounted for 20.10% of the total effect of VRF burden on depressive symptoms. Exploratory analyses taking a symptom-based approach revealed that mediating pathways pertained to specific depressive symptoms: tiredness and changes in appetite. These results suggest that the small association between VRF burden and depressive symptoms may be partly explained by the inflammation-promoting effects of VRFs, which might promote a specific symptom-profile of depression

Kinematics of Crystal Growth in Single‐Seal Syntaxial Veins in Limestone ‐ A Phase‐Field Study

Building on recent developments in phase-field modeling of structural diagenesis, we present an analysis of single-seal syntaxial calcite vein microstructure in a variety of limestones. We focus on the effects of fracture aperture, intergranular versus transgranular fracturing, crystal habit and the presence of second phases in the host rock, to systematically investigate a simplified set of models covering the main classes of limestone in 2D. We incorporate the kinematic process of growth competition between differently oriented crystals, growth rate anisotropy between rough and faceted crystal surfaces and different growth rates on intergranular to transgranular fractures. Results show that within the considered parameter space we can reproduce a wide range of vein microstructures in limestone known in nature, such as stretched crystals, wide-blocky veins, and elongated crystals. We identify five archetypes of vein microstructures in limestones, which are diagnostic for different kinematics and evolution of transport processes and illustrate the effect of key parameters in microstructure maps. We show how syntaxial veins with median line form after intergranular fracturing, while stretched crystals indicate transgranular fracturing. Intergranular fracturing leads to stronger growth competition and more prominent CPO in syntaxial veins. Our results can be extended to 3D to include multiple crack-seal events, pore-space cementation and simulation of fluid flow, providing a generic platform for modeling structural diagenesis in limestones

Coniferous bark hot steam treatment for the elimination of the pinewood nematode

In order to develop an artificial heat treatment to eliminate the pinewood nematode (PWN), Bursaphelenchus xylophilus, from coniferous bark, an industrial equipment, based on hot steam was build up which enables continuous bark treatment for more than 30 min with temperatures above 80ºC. Biological assays were performed using experimental units (bags) with Pinus pinaster bark and wood chips containing more than 100 000 PWN (.60% third dispersal juvenile s tage). The bags were heat treated for 30 min and the temperature inside monitored by temperature probes. The total number of live nematodes was quantified immediately after treatment and after incubation (25ºC for 15 days) and in both situations no nematodes were detected revealing efficacy in eliminating PWN from coniferous bark

Distinct sites of opiate reward and aversion within the midbrain identified using a herpes simplex virus vector expressing GluR1

Repeated administration of morphine increases expression of GluR1 (an AMPA glutamate receptor subunit) in the ventral tegmental area (VTA) of the midbrain, an important neural substrate for the rewarding actions of morphine. Microinjections of a herpes simplex virus (HSV) vector that causes local overexpression of GluR1 (HSV-GluR1) into the VTA can enhance the ability of morphine to establish conditioned place preferences, suggesting that altered GluR1 expression in this region is directly associated with changes in the rewarding efficacy of morphine. We now report that in rats given HSV-GluR1 directly into the VTA, morphine is most rewarding when maximal transgene expression is in the rostral VTA, whereas morphine is aversive when maximal transgene expression is in the caudal VTA. Dual-labeling immunohistochemistry shows that this difference cannot be explained by a different fraction of dopaminergic neurons infected in the rostral versus caudal VTA. No such anatomical specificity is seen in rats given VTA microinjections of HSV-LacZ, a vector expressing a control protein (beta-galactosidase). These results suggest that distinct substrates within the VTA itself differentially contribute to the rewarding and aversive properties of opiates