A Predictor-Informed Multi-Subject Bayesian Approach for Dynamic Functional Connectivity

Time Varying Functional Connectivity (TVFC) investigates how the interactions among brain regions vary over the course of an fMRI experiment. The transitions between different individual connectivity states can be modulated by changes in underlying physiological mechanisms that drive functional network dynamics, e.g., changes in attention or cognitive effort as measured by pupil dilation. In this paper, we develop a multi-subject Bayesian framework for estimating dynamic functional networks as a function of time-varying exogenous physiological covariates that are simultaneously recorded in each subject during the fMRI experiment. More specifically, we consider a dynamic Gaussian graphical model approach, where a non-homogeneous hidden Markov model is employed to classify the fMRI time series into latent neurological states, borrowing strength over the entire time course of the experiment. The state-transition probabilities are assumed to vary over time and across subjects, as a function of the underlying covariates, allowing for the estimation of recurrent connectivity patterns and the sharing of networks among the subjects. Our modeling approach further assumes sparsity in the network structures, via shrinkage priors. We achieve edge selection in the estimated graph structures, by introducing a multi-comparison procedure for shrinkage-based inferences with Bayesian false discovery rate control. We apply our modeling framework on a resting-state experiment where fMRI data have been collected concurrently with pupillometry measurements, leading us to assess the heterogeneity of the effects of changes in pupil dilation, previously linked to changes in norepinephrine-containing locus coeruleus, on the subjects' propensity to change connectivity states

Hierarchical Corannulene‐Based Materials: Energy Transfer and Solid‐State Photophysics

We report the first example of a donor–acceptor corannulene-containing hybrid material with rapid ligand-to-ligand energy transfer (ET). Additionally, we provide the first time-resolved photoluminescence (PL) data for any corannulene-based compounds in the solid state. Comprehensive analysis of PL data in combination with theoretical calculations of donor–acceptor exciton coupling was employed to estimate ET rate and efficiency in the prepared material. The ligand-to-ligand ET rate calculated using two models is comparable with that observed in fullerene-containing materials, which are generally considered for molecular electronics development. Thus, the presented studies not only demonstrate the possibility of merging the intrinsic properties of π-bowls, specifically corannulene derivatives, with the versatility of crystalline hybrid scaffolds, but could also foreshadow the engineering of a novel class of hierarchical corannulene-based hybrid materials for optoelectronic devices

Base-enhanced catalytic water oxidation by a carboxylate–bipyridine Ru(II) complex

Development of rapid, robust water oxidation catalysts remains an essential element in solar water splitting by artificial photosynthesis. We report here dramatic rate enhancements with added buffer bases for a robust Ru(II) polypyridyl catalyst with a calculated half-time for water oxidation of ∼7 μs in 1.0 M phosphate. The results of detailed kinetic studies provide insight into the water oxidation mechanism and an important role for added buffer bases in accelerating water oxidation by concerted atom–proton transfer

Measurement of the production of a W boson in association with a charm quark in pp collisions at √s = 7 TeV with the ATLAS detector

The production of a W boson in association with a single charm quark is studied using 4.6 fb−1 of pp collision data at s√ = 7 TeV collected with the ATLAS detector at the Large Hadron Collider. In events in which a W boson decays to an electron or muon, the charm quark is tagged either by its semileptonic decay to a muon or by the presence of a charmed meson. The integrated and differential cross sections as a function of the pseudorapidity of the lepton from the W-boson decay are measured. Results are compared to the predictions of next-to-leading-order QCD calculations obtained from various parton distribution function parameterisations. The ratio of the strange-to-down sea-quark distributions is determined to be 0.96+0.26−0.30 at Q 2 = 1.9 GeV2, which supports the hypothesis of an SU(3)-symmetric composition of the light-quark sea. Additionally, the cross-section ratio σ(W + +c¯¯)/σ(W − + c) is compared to the predictions obtained using parton distribution function parameterisations with different assumptions about the s−s¯¯¯ quark asymmetry

Measurement of the tt¯ production cross-section as a function of jet multiplicity and jet transverse momentum in 7 TeV proton-proton collisions with the ATLAS detector

The tt¯ production cross-section dependence on jet multiplicity and jet transverse momentum is reported for proton-proton collisions at a centre-of-mass energy of 7 TeV in the single-lepton channel. The data were collected with the ATLAS detector at the CERN Large Hadron Collider and comprise the full 2011 data sample corresponding to an integrated luminosity of 4.6 fb−1. Differential cross-sections are presented as a function of the jet multiplicity for up to eight jets using jet transverse momentum thresholds of 25, 40, 60, and 80 GeV, and as a function of jet transverse momentum up to the fifth jet. The results are shown after background subtraction and corrections for all known detector effects, within a kinematic range closely matched to the experimental acceptance. Several QCD-based Monte Carlo models are compared with the results. Sensitivity to the parton shower modelling is found at the higher jet multiplicities, at high transverse momentum of the leading jet and in the transverse momentum spectrum of the fifth leading jet. The MC@NLO+HERWIG MC is found to predict too few events at higher jet multiplicities

Measurement of the low-mass Drell-Yan differential cross section at √s = 7 TeV using the ATLAS detector

The differential cross section for the process Z/γ ∗ → ℓℓ (ℓ = e, μ) as a function of dilepton invariant mass is measured in pp collisions at s√ = 7 TeV at the LHC using the ATLAS detector. The measurement is performed in the e and μ channels for invariant masses between 26 GeV and 66 GeV using an integrated luminosity of 1.6 fb−1 collected in 2011 and these measurements are combined. The analysis is extended to invariant masses as low as 12 GeV in the muon channel using 35 pb−1 of data collected in 2010. The cross sections are determined within fiducial acceptance regions and corrections to extrapolate the measurements to the full kinematic range are provided. Next-to-next-to-leading-order QCD predictions provide a significantly better description of the results than next-to-leading-order QCD calculations, unless the latter are matched to a parton shower calculation

Dijet production in √s = 7 TeV pp collisions with large rapidity gaps at the ATLAS experiment

A 6.8 nb−¹ sample of pp collision data collected under low-luminosity conditions at √s = 7 TeV by the ATLAS detector at the Large Hadron Collider is used to study diffractive dijet production. Events containing at least two jets with pT > 20 GeV are selected and analysed in terms of variables which discriminate between diffractive and non-diffractive processes. Cross sections are measured differentially in ΔηF, the size of the observable forward region of pseudorapidity which is devoid of hadronic activity, and in an estimator, ξ˜, of the fractional momentum loss of the proton assuming single diffractive dissociation (pp → p X). Model comparisons indicate a dominant non-diffractive contribution up to moderately large ηF and small ξ˜, with a diffractive contribution which is significant at the highest ΔηF and the lowest ξ˜. The rapidity-gap survival probability is estimated from comparisons of the data in this latter region with predictions based on diffractive parton distribution functions

Computational, Spectroscopic, and Electrochemical Studies of Molybdoenzyme and Hydrogenase Active Site Inspired Complexes

Production of H2 as an alternate fuel source requires the discovery of new, efficient, and cheap catalysts. Extensive studies on the development of active site analogues of the [FeFe] hydrogenase enzyme have been carried out for this reason. In our studies, electrochemistry, photoelectron spectroscopy and density functional theory calculations were utilized to develop and study the catalytic mechanisms for many catalysts that produce molecular hydrogen. These techniques have also been used to determine the factors that influence the correlation between gas-phase ionizations and solution-phase oxidations for a series of Tp*Mo(V) complexes.Mechanistic studies were carried out on two hydrogenase-inspired catalysts: [(eta5-C5H5)Fe(CO)2]2 and (mu-1,2-benzenedithiolato)[Fe(CO)3]2. Electrochemistry and calculations indicate that both molecules enter into catalytic cycles from the reduction of the neutral procatalyst complexes. The molecules, after reduction, catalytically produce H2 from acids such as acetic acid and 4-tert-butylphenol through CECE mechanisms. During one of the studies, it was found that calculations and electrochemical simulations did not agree with the liturature pKa value for (eta5 C5H5)Fe(CO)2H, which is one of the proposed species in the catalytic mechanism. The pKa of (eta5-C5H5)Fe(CO)2H was redetermined experimentally and found to be 26.7.The aim of the third chapter is to make improvements on the catalytic activity of (mu-1,2-C6H4S2)[Fe(CO),3]2 by perturbing the electronic structure through ligand exchanges. Two different phosphine ligands, triphenyl phosphine and 1,3,5-triaza-7-phosphaadamantane, were successfully substituted for CO ligands on the (mu-1,2-benzenedithiolato)Fe2(CO)6 complex. The 1,2-benzenedithiolate ligand was also exchanged for 1,4-dimethyoxy-2,3-benzenedithiolate.The last chapter focuses on complexes of the general form Tp*MoO(OX)2 (where Tp* = hydrotris(3,5-dimethyl-1-pyrazolyl)borate and (OX)2 = (OMe)2, (OEt)2, and (OnPr)2 for alkoxide ligands, and (OX)2 = O(CH2)3O, O(CH2)4O, and O[CH(CH3)CH2CH(CH3)]O for diolato ligands). Oxidation potentials and first ionization energies are shown to be highly sensitive to the number of carbon atoms present in the diolato and alkoxide ligands. A linear correlation between the solution-phase oxidation potentials and the gas-phase ionization energies resulted in an unexpected slope of greater than unity. Density functional theory calculations indicated that cation reorganization energies ranged from 0.15 - 0.51 eV, and this unique correlation was a result of the large differences in the cation reorganization energies