A Model-Based Assessment of the Seizure Onset Zone Predictive Power to Inform the Epileptogenic Zone

This is the final version. Available on open access from Frontiers media via the DOI i this recordEpilepsy surgery is a clinical procedure that aims to remove the brain tissue responsible for the emergence of seizures, the epileptogenic zone (EZ). It is preceded by an evaluation to determine the brain tissue that must be resected. The identification of the seizure onset zone (SOZ) from intracranial EEG recordings stands as one of the key proxies for the EZ. In this study we used computational models of epilepsy to assess to what extent the SOZ may or may not represent the EZ. We considered a set of different synthetic networks (e.g., regular, small-world, random, and scale-free networks) to represent large-scale brain networks and a phenomenological network model of seizure generation. In the model, the SOZ was inferred from the seizure likelihood (SL), a measure of the propensity of single nodes to produce epileptiform dynamics, whilst a surgery corresponded to the removal of nodes and connections from the network. We used the concept of node ictogenicity (NI) to quantify the effectiveness of each node removal on reducing the network's propensity to generate seizures. This framework enabled us to systematically compare the SOZ and the seizure control achieved by each considered surgery. Specifically, we compared the distributions of SL and NI across different networks. We found that SL and NI were concordant when all nodes were similarly ictogenic, whereas when there was a small fraction of nodes with high NI, the SL was not specific at identifying these nodes. We further considered networks with heterogeneous node excitabilities, i.e., nodes with different susceptibilities of being engaged in seizure activity, to understand how such heterogeneity may affect the relationship between SL and NI. We found that while SL and NI are concordant when there is a small fraction of hyper-excitable nodes in a network that is otherwise homogeneous, they do diverge if the network is heterogeneous, such as in scale-free networks. We observe that SL is highly dependent on node excitabilities, whilst the effect of surgical resections as revealed by NI is mostly determined by network structure. Together our results suggest that the SOZ is not always a good marker of the EZ.Medical Research Council (MRC)Epilepsy Research UKEngineering and Physical Sciences Research Council (EPSRC)Wellcome Trus

A B-Spline-Based Generative Adversarial Network Model for Fast Interactive Airfoil Aerodynamic Optimization

Airfoil aerodynamic optimization is of great importance in aircraft design; however, it relies on high-fidelity physics-based models that are computationally expensive to evaluate. In this work, we provide a methodology to reduce the computational cost for airfoil aerodynamic optimization. Firstly, we develop a B-spline based generative adversarial networks (BSplineGAN) parameterization method to automatically infer design space with sufficient shape variability. Secondly, we construct multi-layer neural network (MNN) surrogates for fast predictions on aerodynamic drag, lift, and pitching moment coefficients. The BSplineGAN has a relative error lower than 1% when fitting to UIUC database. Verification of MNN surrogates shows the root means square errors (RMSE) of all aerodynamic coefficients are within the range of 20%–40% standard deviation of testing points. Both normalized RMSE and relative errors are controlled within 1%. The proposed methodology is then demonstrated on an airfoil aerodynamic optimization. We also verified the baseline and optimized designs using a high-fidelity computational fluid dynamic solver. The proposed framework has the potential to enable web-based fast interactive airfoil aerodynamic optimization

Temporally correlated fluctuations drive epileptiform dynamics

Published onlineJournal ArticleMacroscopic models of brain networks typically incorporate assumptions regarding the characteristics of afferent noise, which is used to represent input from distal brain regions or ongoing fluctuations in non-modelled parts of the brain. Such inputs are often modelled by Gaussian white noise which has a flat power spectrum. In contrast, macroscopic fluctuations in the brain typically follow a 1/f(b) spectrum. It is therefore important to understand the effect on brain dynamics of deviations from the assumption of white noise. In particular, we wish to understand the role that noise might play in eliciting aberrant rhythms in the epileptic brain. To address this question we study the response of a neural mass model to driving by stochastic, temporally correlated input. We characterise the model in terms of whether it generates "healthy" or "epileptiform" dynamics and observe which of these dynamics predominate under different choices of temporal correlation and amplitude of an Ornstein-Uhlenbeck process. We find that certain temporal correlations are prone to eliciting epileptiform dynamics, and that these correlations produce noise with maximal power in the δ and θ bands. Crucially, these are rhythms that are found to be enhanced prior to seizures in humans and animal models of epilepsy. In order to understand why these rhythms can generate epileptiform dynamics, we analyse the response of the model to sinusoidal driving and explain how the bifurcation structure of the model gives rise to these findings. Our results provide insight into how ongoing fluctuations in brain dynamics can facilitate the onset and propagation of epileptiform rhythms in brain networks. Furthermore, we highlight the need to combine large-scale models with noise of a variety of different types in order to understand brain (dys-)function.This work was supported by the European Commission through the FP7 Marie Curie Initial Training Network 289146 (NETT: Neural Engineering Transformative Technologies), by the Spanish Ministry of Economy and Competitiveness and FEDER (project FIS2012-37655-C02-01). J.G.O. also acknowledges support from the ICREA Academia programme, the Generalitat de Catalunya (project 2014SGR0947), and the “María de Maeztu” Programme for Units of Excellence in R&D (Spanish Ministry of Economy and Competitiveness, MDM-2014-0370) M.G. gratefully acknowledges the financial support of the EPSRC via grant EP/N014391/1. The contribution of M.G. was generously supported by a Wellcome Trust Institutional Strategic Support Award (WT105618MA)

Fluid Inclusion Petrography and Microthermometry of the Middle Valley Hydrothermal System, Northern Juan de Fuca Ridge

Middle Valley is a hydrothermally active, sediment-covered rift at the northernmost end of the Juan de Fuca Ridge. Two hydrothermal centers are known from previous work: (1) a 60-m-high sediment mound with a 35-m-high inactive sulfide mound and two 20-m-high sulfide mounds 330 m to the south, one of which is known to be active, and (2) several mounds with attendant active hydrothermal chimneys. These sites (Sites 856 and 858, respectively), as well as other adjacent areas (Sites 857 and 855), were drilled during Leg 139 of the Ocean Drilling Program. Fluid inclusion petrographic observations and microthermometric measurements were made on a variety of samples and minerals recovered from these cores: (1) quartz from hydrothermally altered sediment; (2) low iron sphalerite and interstitial dolomite in massive sulfide; (3) calcite-sulfide veins cross-cutting sediment; (4) calcite and anhydrite concretions in sediment; (5) anhydrite veins cross-cutting sediment; and (6) wairakite and quartz veins cross-cutting mafic sills and sediment. Trapping temperatures of fluid inclusions in hydrothermal alteration minerals precipitated with massive sulfides range between 90° and 338°C. Fluid inclusions in calcite in carbonate concretions indicate these concretions formed between 112° and 192°C. Anhydrite in veins and concretions was precipitated between 137° and 311 °C. Quartz-wairakiteepidote veins in mafic sills and hydrothermally altered sediment were precipitated between 210° and 350°C. For all inclusions, there is a general increase in minimum trapping temperatures with increasing subsurface depth for all sites, with temperatures ranging from around 100°C at 2400 meters below sea level to around 275°C at 3100 mbsl. Eutectic and hydrohalite melting temperatures indicate that Ca, Na, and Cl are the dominant ionic species present in the inclusion fluids. Salinities for most inclusion fluids range between 2.5 and 7.0 equivalent weight percent NaCl. Most analyses are between 3 and 4.5 eq. wt% NaCl and similar to ambient bottom water, pore fluids, and vent fluid from Site 858. Trapped fluids are modified seawater, and there is no evidence for a significant magmatic fluid component. Oxygen isotopic compositions for fluids from which calcite concretions were precipitated, calculated from isotopic analyses of carbonates formed at low temperatures (133° to 158°C from fluid inclusions), are significantly enriched in 18O (δ1 8θ = +9.3‰ to +13.2‰), likely due to reaction with subsurface sediments at low water/rock ratios. Calcite that formed at higher temperatures (233°C) in hydrothermally altered sediment was precipitated from fluid only slightly enriched in 18O (δ1 8θ = +0.4%o). Estimated carbon isotope compositions of the fluid vary between δ13C = -7.0%e and -35.4‰ and are similar to the measured range for vent fluids

Nocardia kroppenstedtii sp. nov., a novel actinomycete isolated from a lung transplant patient with a pulmonary infection

An actinomycete, strain N1286T, isolated from a lung transplant patient with a pulmonary infection, was provisionally assigned to the genus Nocardia. The strain had chemotaxonomic and morphological properties typical of members of the genus Nocardia and formed a distinct phyletic line in the Nocardia 16S rRNA gene tree. It was most closely related to Nocardia farcinica DSM 43665T (99.8% gene similarity) but was distinguished from the latter by a low level of DNA:DNA relatedness. These strains were also distinguished by a broad range of phenotypic properties. On the basis of these data, it is proposed that isolate N1286T (=DSM 45810T = NCTC 13617T) should be classified as the type strain of a new Nocardia species for which the name Nocardia kroppenstedtii is proposed