Electrochemistry of potentially bioreductive alkylating quinones : Part 1. Electrochemical properties of relatively simple quinones, as model compounds of mitomycin- and aziridinylquinone-type antitumour agents

The influence of methyl-, hydroxy and amino substituents on the electrochemical behaviour of simple 1,4-naphtho-and 1,4-benzoquinones, model compounds of many quinoid antitumour agents, in aqueous media was studied. Significant changes in electrochemical behaviour were observed, potentially the result of a change in the electron density of the quinone moiety, pre- or post-protonation of substituents, hydrogen bond formation, tautomerization reactions and steric interactions between the quinone moiety and substituents. The information obtained was of benefit in the elucidation of the reduction mechanisms of quinoid antitumour agents such as aziridnylquinones and mitomycins

Automated image segmentation of 3D printed fibrous composite micro-structures using a neural network

A new, automated image segmentation method is presented that effectively identifies the micro-structural objects (fibre, air void, matrix) of 3D printed fibre-reinforced materials using a deep convolutional neural network. The method creates training data from a physical specimen composed of a single, straight fibre embedded in a cementitious matrix with air voids. The specific micro-structure of this strain-hardening cementitious composite (SHCC) is obtained from X-ray micro-computed tomography scanning, after which the 3D ground truth mask of the sample is constructed by connecting each voxel of a scanned image to the corresponding micro-structural object. The neural network is trained to identify fibres oriented in arbitrary directions through the application of a data augmentation procedure, which eliminates the time-consuming task of a human expert to manually annotate these data. The predictive capability of the methodology is demonstrated via the analysis of a practical SHCC developed for 3D concrete printing, showing that the automated segmentation method is well capable of adequately identifying complex micro-structures with arbitrarily distributed and oriented fibres. Although the focus of the current study is on SHCC materials, the proposed methodology can also be applied to other fibre-reinforced materials, such as fibre-reinforced plastics. The micro-structures identified by the image segmentation method may serve as input for dedicated finite element models that allow for computing their mechanical behaviour as a function of the micro-structural composition

K* nucleon hyperon form factors and nucleon strangeness

A crucial input for recent meson hyperon cloud model estimates of the nucleon matrix element of the strangeness current are the nucleon-hyperon-K* (NYK*) form factors which regularize some of the arising loops. Prompted by new and forthcoming information on these form factors from hyperon-nucleon potential models, we analyze the dependence of the loop model results for the strange-quark observables on the NYK* form factors and couplings. We find, in particular, that the now generally favored soft N-Lambda-K* form factors can reduce the magnitude of the K* contributions in such models by more than an order of magnitude, compared to previous results with hard form factors. We also discuss some general implications of our results for hadronic loop models.Comment: 9 pages, 8 figures, new co-author, discussion extended to the momentum dependence of the strange vector form factor

Effects of testosterone administration on threat and escape anticipation in the orbitofrontal cortex.

Recent evidence suggests that the steroid hormone testosterone can decrease the functional coupling between orbitofrontal cortex (OFC) and amygdala. Theoretically this decoupling has been linked to a testosterone-driven increase of goal-directed behaviour in case of threat, but this has never been studied directly. Therefore, we placed twenty-two women in dynamically changing situations of escapable and inescapable threat after a within-subject placebo controlled testosterone administration. Using functional magnetic resonance imaging (fMRI) we provide evidence that testosterone activates the left lateral OFC (LOFC) in preparation of active goal-directed escape and decouples this OFC area from a subcortical threat system including the central-medial amygdala, hypothalamus and periaqueductal gray. This LOFC decoupling was specific to threatening situations, a point that was further emphasized by an absence of such decoupling in a second experiment focused on resting-state connectivity. These results not only confirm that testosterone administration decouples the LOFC from the subcortical threat system, but also show that this is specifically the case in response to acute threat, and ultimately leads to an increase in LOFC activity when the participant prepares a goal-directed action to escape. Together these results for the first time provide a detailed understanding of functional brain alterations induced by testosterone under threat conditions, and corroborate and extend the view that testosterone prepares the brain for goal-directed action in case of threat.FSW – Publicaties zonder aanstelling Universiteit Leide

Photomodulation of transmembrane transport and potential by stiff-stilbene based bis(thio)ureas

NWOSupramolecular & Biomaterials Chemistr