Search results for " correlation."
showing 10 items of 1333 documents
An ab initio study of the tautomeric equilibria of the N-oxides of hydroxypyridines in the vapour phase
1993
Abstract An ab initio self-consistent field molecular orbital study of the N-oxides of hydroxypyridines has been carried out. The optimized structures have been obtained at the 6-31G ∗ level, and the energy values have been computed at the 6-31G ∗ and MP2-6-31G ∗ //6-31G ∗ levels. The tautomerization energies for the three couples of systems in the vapour phase have been evaluated.
A theoretical determination of the dissociation energy of the nitric oxide dimer
1994
Multi-reference CI methods have been applied to determine the dissociation energy and structure of thecis-N2O2 molecule. The convergence of the theoretical result has been checked with respect to a systematic expansion of the one-electron basis set and the multi-reference CI wave function. The best calculated value, 13.8 kJ/mol, is in agreement with the experimental value, 12.2 kJ/mol. It has been obtained with an extended ANO-type basis set [6s5p3d2f], including the effect of the basis set superposition error (BSSE) in the geometry optimization, and additional effects, such as the electron correlation of core electrons and relativistic corrections, using the average coupled pair functional…
Analysis of the CIPSI/DCCI approach to characterize the HF AND F2 single bond
1990
Abstract The aim of the present work is to account for the main differential correlation contributions occurring during the bond breaking process of HF and F2 molecules in an accurate and inexpensive way. Starting from the dissociation-consistent configuration interaction (DCCI) scheme by Goddard and co-workers the corresponding contributions are evaluated within the framework reported by Malrieu and co-workers, namely configuration interaction by perturbation with multiconfigurational zeroth-order wavefunction selected by iterative process (CIPSI). In addition, the DCCI scheme has been improved by introducing the dispersion effects associated with the valence MOs adjacent to the bond. The …
Diagnostic efficacy of panoramic mandibular index to identify postmenopausal women with low bone mineral densities
2011
Objectives: The aim of the study was to compare and assess the accuracy of panoramic mandibular index (PMI) and antegonial index (AI) in the panoramic radiographs of postmenopausal women with normal and low skeletal bone mineral densities( BMD) diagnosed by using dual energy x-ray absorptiometry ( DXA). Study Design: In panoramic radiographs obtained from 40 post menopausal women( 20 normal and 20 osteoporo tic) aged between 50-75 who’s BMD has already been assessed by a DXA, the mean was calculated for PMI and AI index values measured in the right and left mandibles. The PMI and AI index values were evaluated using the student’s t test. The correlation between the observers for indices was…
Emergence of statistically validated financial intraday lead-lag relationships
2014
According to the leading models in modern finance, the presence of intraday lead-lag relationships between financial assets is negligible in efficient markets. With the advance of technology, however, markets have become more sophisticated. To determine whether this has resulted in an improved market efficiency, we investigate whether statistically significant lagged correlation relationships exist in financial markets. We introduce a numerical method to statistically validate links in correlation-based networks, and employ our method to study lagged correlation networks of equity returns in financial markets. Crucially, our statistical validation of lead-lag relationships accounts for mult…
Functional connectivity inference from fMRI data using multivariate information measures
2022
Abstract Shannon’s entropy or an extension of Shannon’s entropy can be used to quantify information transmission between or among variables. Mutual information is the pair-wise information that captures nonlinear relationships between variables. It is more robust than linear correlation methods. Beyond mutual information, two generalizations are defined for multivariate distributions: interaction information or co-information and total correlation or multi-mutual information. In comparison to mutual information, interaction information and total correlation are underutilized and poorly studied in applied neuroscience research. Quantifying information flow between brain regions is not explic…
Discovering hidden brain network responses to naturalistic stimuli via tensor component analysis of multi-subject fMRI data
2021
The study of brain network interactions during naturalistic stimuli facilitates a deeper understanding of human brain function. To estimate large-scale brain networks evoked with naturalistic stimuli, a tensor component analysis (TCA) based framework was used to characterize shared spatio-temporal patterns across subjects in a purely data-driven manner. In this framework, a third-order tensor is constructed from the timeseries extracted from all brain regions from a given parcellation, for all participants, with modes of the tensor corresponding to spatial distribution, time series and participants. TCA then reveals spatially and temporally shared components, i.e., evoked networks with the …
Theoretical study of the low‐lying states of trans‐1,3‐butadiene
1992
We present extensive ab initio calculations on the low‐lying electronic states of trans‐1,3‐butadiene within the multireference configuration interaction (MRCI) framework by selecting the configurations with a perturbative criterion. The X 1Ag ground state and 1 3Bu, 1 3Ag, 2 1Ag, and 1 1Bu valence excited states have been calculated at a fixed geometry. The results obtained are in good agreement with previous experimental and calculated values, and could help to understand polyene spectroscopy, photochemistry, and photophysics. The advantages of a MRCI method where the most important contributions to the total MRCI wave function, perturbatively selected, are treated variationally, and the …
Genotype‐phenotype correlations in Brazilian patients with hereditary angioedema due to C1 inhibitor deficiency. [Carta]
2019
Use of CD64 for the diagnosis of sepsis: a case-control study.
2010
CD64 is the high-affinity receptor of IgG. It is upregulated by inflammatory cytokines on neutrophils. The upregulation of CD64 is linked with PMN activation in SIRS or sepsis. Our aim is to verify these correlations.