Vanadium dioxide : A Peierls-Mott insulator stable against disorder

Vanadium dioxide undergoes a first order metal-insulator transition at 340 K. In this work, we develop and carry out state of the art linear scaling DFT calculations refined with non-local dynamical mean-field theory. We identify a complex mechanism, a Peierls-assisted orbital selection Mott instability, which is responsible for the insulating M$_1$ phase, and furthermore survives a moderate degree of disorder.Comment: 5 pages, 4 figures. Supplementary material 8 pages, 4 figures. This version (v2) matches that accepted for Physical Review Letters on 16th May 201

Adipose tissue dysfunction, inflammation, and insulin resistance alternative pathways to cardiac remodelling in schizophrenia. A multimodal, case-control study

Background Cardiovascular disease is the leading cause of excess mortality in schizophrenia. Patients with schizophrenia show evidence of increased concentric cardiac remodelling (CCR), defined as an increase in left-ventricular mass over end-diastolic volumes. CCR is a predictor of cardiac disease, but the molecular pathways leading to this in schizophrenia are unknown. We aimed to explore the relevance of hypertensive and non-hypertensive pathways to CCR, and their potential molecular underpinnings in schizophrenia. Methods and findings In this multimodal case-control study we collected cardiac and whole-body fat magnetic resonance imaging (MRI), clinical measures, and blood levels of several cardiometabolic biomarkers known to potentially cause CCR from individuals with schizophrenia, alongside healthy controls (HCs) matched for age, sex, ethnicity, and body surface area. Of 50 participants, 34 (68%) were male. Participants with schizophrenia showed increases in cardiac concentricity (d=0.71, 95%CI: 0.12,1.30; p=0.01), indicative of CCR, but showed no differences in overall content or regional distribution of adipose tissue compared to HCs. Despite the cardiac changes, participants with schizophrenia did not demonstrate activation of the hypertensive CCR pathway; however, they showed evidence of adipose dysfunction: adiponectin was reduced (d=-0.69, 95%CI: -1.28,-0.10; p=0.02), with evidence of activation of downstream pathways including hypertriglyceridemia, elevated C-reactive protein, fasting glucose, and alkaline phosphatase. Conclusions People with schizophrenia showed adipose tissue dysfunction compared to BMI-matched HCs. The presence of non-hypertensive CCR and a dysmetabolic phenotype may contribute to excess cardiovascular risk in schizophrenia. If our results are confirmed, acting on this pathway could reduce cardiovascular risk and resultant lifeyears lost in people with schizophrenia

Anxiety-like behavior and structural changes of the bed nucleus of the stria terminalis (BNST) in gestational protein-restricted male offspring

Animal evidence has suggested that maternal emotional and nutritional stress during pregnancy is associated with behavioral outcomes in offspring. The nature of the stresses applied may differ, but it is often assumed that the mother's hippocampus-hypothalamic-pituitary-adrenal (HHPA) axis response releases higher levels of glucocorticoid hormones. The bed nucleus of the stria terminalis (BNST) is in a pivotal position to regulate the HHPA axis and the stress response, and it has been implicated in anxiety behavior. In the current study, to search whether BNST structural changes and neurochemical alterations are associated with anxiety-related behavior in adult gestational protein-restricted offspring relative to an age-matched normal protein diet (NP) rats, we conduct behavioral tests and, BNST dendritic tree analysis by Sholl analysis, associated to immunoblotting-protein quantification [11β-HSD2, GR, MR, AT1R, 5HT1A and 5HT2A, corticotrophin-releasing factor (CRH) and CRH1]. Dams were maintained either on isocaloric standard rodent chow [with NP content, 17% casein or low protein content (LP), 6% casein] chow throughout their entire pregnancy. Here, in rats subjected to gestational protein restriction, we found: (a) a significant reduction in dendritic length and impoverished dendritic arborization in BNST neurons; (b) an elevated plasmatic corticosterone levels; and (c) associated with enhanced anxiety-like behavior when compared with age-matched NP offspring. Moreover, altered protein (11β-HSD2, GR, MR and type 1 CRH receptors) expressions may underlie the increase in anxiety-like behavior in LP offspring. This work represents the first demonstration that BNST developmental plasticity by maternal protein restriction, resulting in fine structural changes and neurochemical alterations that are associated with modified behavioral states.Fundação de Amparo à Pesquisa do Estado de São Paulo (2005/54362-4 and 2013/12486-5) and Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)info:eu-repo/semantics/publishedVersio

Vibrational and vibrational-torsional interactions in the 0–600 cm-1 region of the S1 ← S0 spectrum of p-xylene investigated with resonance-enhanced multiphoton ionization (REMPI) and zero-kinetic-energy (ZEKE) spectroscopy

We assign the 0–600 cm-1 region of the S1 ← S0 transition in p-xylene using resonance-enhanced multiphoton ionization (REMPI) and zero-kinetic-energy (ZEKE) spectroscopy. In the 0–300 cm-1 range, as well as the intense origin band there are a number of torsional and vibration-torsion (vibtor) features. The latter are discussed in more detail in an accompanying paper [Gardner et al. J. Chem. Phys. XXX, xxxxxx (2016)]. Here we focus on the origin and the 300–650 cm-1 region, where vibrational bands and some vibtor activity is observed. From the origin ZEKE spectrum we derive the ionization energy of p-xylene as 68200 ± 5 cm-1. The assignment of the REMPI spectrum is based on the activity observed in the ZEKE spectra coupled with knowledge of the vibrational wavenumbers obtained from quantum chemical calculations. We assign several isolated vibrations, and a complex Fermi resonance that is found to comprise contributions from both vibrations and vibtor levels, and we examine this via a two-dimensional ZEKE (2D-ZEKE) spectrum. A number of the vibrational features in the REMPI and ZEKE spectra of p-xylene that have been reported previously are reassigned and now largely consist of totally-symmetric contributions. We briefly discuss the appearance of non-Franck-Condon allowed transitions. Finally, we find remarkably similar spectral activity to that in the related disubstituted benzenes, para-difluorobenzene and para-fluorotoluene

Optoelectronic Studies of Methylammonium Lead Iodide Perovskite Solar Cells with Mesoporous TiO2: Separation of Electronic and Chemical Charge Storage, Understanding Two Recombination Lifetimes, and the Evolution of Band Offsets during J-V Hysteresis

Methylammonium lead iodide (MAPI) cells of the design FTO/sTiO2/ mpTiO2/MAPI/Spiro-OMeTAD/Au, where FTO is fluorine-doped tin oxide, sTiO2 indicates solid-TiO2, and mpTiO2 is mesoporous TiO2, are studied using transient photovoltage (TPV), differential capacitance, charge extraction, current interrupt, and chronophotoamperometry. We show that in mpTiO2/MAPI cells there are two kinds of extractable charge stored under operation: a capacitive electronic charge (&sim;0.2 &mu;C/ cm2) and another, larger charge (40 &mu;C/cm2), possibly related to mobile ions. Transient photovoltage decays are strongly double exponential with two time constants that differ by a factor of &sim;5, independent of bias light intensity. The fast decay (&sim;1 &mu;s at 1 sun) is assigned to the predominant charge recombination pathway in the cell. We examine and reject the possibility that the fast decay is due to ferroelectric relaxation or to the bulk photovoltaic effect. Like many MAPI solar cells, the studied cells show significant J&minus;V hysteresis. Capacitance vs open circuit voltage (Voc) data indicate that the hysteresis involves a change in internal potential gradients, likely a shift in band offset at the TiO2/MAPI interface. The TPV results show that the Voc hysteresis is not due to a change in recombination rate constant. Calculation of recombination flux at Voc suggests that the hysteresis is also not due to an increase in charge separation efficiency and that charge generation is not a function of applied bias. We also show that the J&minus;V hysteresis is not a light driven effect but is caused by exposure to electrical bias, light or dark.</div

Learning-based quality control for cardiac MR images

The effectiveness of a cardiovascular magnetic resonance (CMR) scan depends on the ability of the operator to correctly tune the acquisition parameters to the subject being scanned and on the potential occurrence of imaging artifacts, such as cardiac and respiratory motion. In the clinical practice, a quality control step is performed by visual assessment of the acquired images; however, this procedure is strongly operator-dependent, cumbersome, and sometimes incompatible with the time constraints in clinical settings and large-scale studies. We propose a fast, fully automated, and learning-based quality control pipeline for CMR images, specifically for short-axis image stacks. Our pipeline performs three important quality checks: 1) heart coverage estimation; 2) inter-slice motion detection; 3) image contrast estimation in the cardiac region. The pipeline uses a hybrid decision forest method—integrating both regression and structured classification models—to extract landmarks and probabilistic segmentation maps from both long- and short-axis images as a basis to perform the quality checks. The technique was tested on up to 3000 cases from the UK Biobank and on 100 cases from the UK Digital Heart Project and validated against manual annotations and visual inspections performed by expert interpreters. The results show the capability of the proposed pipeline to correctly detect incomplete or corrupted scans (e.g., on UK Biobank, sensitivity and specificity, respectively, 88% and 99% for heart coverage estimation and 85% and 95% for motion detection), allowing their exclusion from the analyzed dataset or the triggering of a new acquisition

Understanding non-linearity in electrochemical systems using multisine-based non-linear characterization

Background: With the development of advanced characterization techniques, lithium-ion battery non-linearities have recently gained increased attention which can benefit battery health diagnosis and ageing mechanism identification. In comparison to conventional single sine wave-based methods, the multisine-based non-linear characterization method has the advantage of capturing the dynamic voltage response within a short testing duration, and therefore has further development potential for on-board applications. However, understanding lithium-ion battery electrochemical processes that contribute to battery non-linearities is still unclear. Methods: In this paper, the sensitivity of the Doyle–Fuller–Newman model parameters are analysed in the frequency domain to investigate the electrochemical processes that contribute to the non-linear dynamics of the voltage response. To begin with, the non-linearities of the Doyle–Fuller–Newman model with validated parameters are characterized and compared to experimental data from a commercial cell. This demonstrated a significant difference between the mathematical model and the non-linearities determined experimentally. Then, a global sensitivity analysis is applied to determine the most sensitive parameter contributing to battery non-linearities. Finally, the appropriate value of the most sensitive parameter which results in the closest non-linear response to the commercial battery is estimated through minimizing the root mean square error. Results: The results show that the charge transfer coefficient is the most sensitive parameter contributing to battery non-linearities among the Doyle–Fuller–Newman model parameters. The non-linear response of the Doyle–Fuller–Newman model is validated with good agreement with the experimental results, when the Butler–Volmer kinetic is asymmetrical due to the unequal anodic and cathodic charge transfer coefficients

The role of hole transport between dyes in solid-state dye-sensitized solar cells

In dye-sensitized solar cells (DSSCs) photogenerated positive charges are normally considered to be carried away from the dyes by a separate phase of hole-transporting material (HTM). We show that there can also be significant transport within the dye monolayer itself before the hole reaches the HTM. We quantify the fraction of dye regeneration in solid-state DSSCs that can be attributed to this process. By using cyclic voltammetry and transient anisotropy spectroscopy, we demonstrate that the rate of interdye hole transport is prevented both on micrometer and nanometer length scales by reducing the dye loading on the TiO₂ surface. The dye regeneration yield is quantified for films with high and low dye loadings (with and without hole percolation in the dye monolayer) infiltrated with varying levels of HTM. Interdye hole transport can account for >50% of the overall dye regeneration with low HTM pore filling. This is reduced to about 5% when the infiltration of the HTM in the pores is optimized in 2 μm thick films. Finally, we use hole transport in the dye monolayer to characterize the spatial distribution of the HTM phase in the pores of the dyed mesoporous TiO₂