52 research outputs found
Size consistent excited states via algorithmic transformations between variational principles
We demonstrate that a broad class of excited state variational principles is
not size consistent. In light of this difficulty, we develop and test an
approach to excited state optimization that transforms between variational
principles in order to achieve state selectivity, size consistency, and
compatibility with quantum Monte Carlo. To complement our formal analysis, we
provide numerical examples that confirm these properties and demonstrate how
they contribute to a more black box approach to excited states in quantum Monte
Carlo.Comment: 27 pages, 10 figures, 2 table
Tracking excited states in wave function optimization using density matrices and variational principles
We present a method for finding individual excited states' energy stationary
points in complete active space self-consistent field theory that is compatible
with standard optimization methods and highly effective at overcoming
difficulties due to root flipping and near-degeneracies. Inspired by both the
maximum overlap method and recent progress in excited state variational
principles, our approach combines these ideas in order to track individual
excited states throughout the orbital optimization process. In a series of
tests involving root flipping, near-degeneracies, charge transfers, and double
excitations, we show that this approach is more effective for state-specific
optimization than either the naive selection of roots based on energy ordering
or a more direct generalization of the maximum overlap method. Furthermore, we
provide evidence that this state-specific approach improves the performance of
complete active space perturbation theory. With a simple implementation, a low
cost, and compatibility with large active space methods, the approach is
designed to be useful in a wide range of excited state investigations.Comment: 13 pages, submitted to JCT
An N-scaling excited-state-specific perturbation theory
We show that by working in a basis similar to that of the natural transition
orbitals and using a modified zeroth order Hamiltonian, the cost of a
recently-introduced perturbative correction to excited state mean field theory
can be reduced from seventh to fifth order in the system size. The
(occupied)(virtual) asymptotic scaling matches that of ground state
second order M{\o}ller-Plesset theory, but with a significantly higher
prefactor because the bottleneck is iterative: it appears in the
Krylov-subspace-based solution of the linear equation that yields the first
order wave function. Here we discuss the details of the modified zeroth order
Hamiltonian we use to reduce the cost as well as the automatic code generation
process we used to derive and verify the cost scaling of the different terms.
Overall, we find that our modifications have little impact on the method's
accuracy, which remains competitive with singles and doubles equation-of-motion
coupled cluster.Comment: 11 pages, 2 figures, 7 tables, accepted by the Journal of Chemical
Theory and Computatio
Studying excited-state-specific perturbation theory on the Thiel set
We explore the performance of a recently-introduced -scaling
excited-state-specific second order perturbation theory (ESMP2) on the singlet
excitations of the Thiel benchmarking set. We find that, without
regularization, ESMP2 is quite sensitive to system size, performing well
in molecules with small systems but poorly in those with larger
systems. With regularization, ESMP2 is far less sensitive to system size
and shows a higher overall accuracy on the Thiel set than CC2, EOM-CCSD, CC3,
and a wide variety of time-dependent density functional approaches.
Unsurprisingly, even regularized ESMP2 is less accurate than multi-reference
perturbation theory on this test set, which can in part be explained by the
set's inclusion of some doubly excited states but none of the strong charge
transfer states that often pose challenges for state-averaging. Beyond
energetics, we find that the ESMP2 doubles norm offers a relatively low-cost
way to test for doubly excited character without the need to define an active
space
Integrating a health-related-quality-of-life module within electronic health records: a comparative case study assessing value added
<p>Abstract</p> <p>Background</p> <p>Health information technology (HIT) applications that incorporate point-of-care use of health-related quality of life (HRQL) assessments are believed to promote patient-centered interactions between seriously ill patients and physicians. However, it is unclear how willing primary care providers are to use such HRQL HIT applications. The specific aim of this study was to explore factors that providers consider when assessing the value added of an HRQL application for their geriatric patients.</p> <p>Methods</p> <p>Three case studies were developed using the following data sources: baseline surveys with providers and staff, observations of staff and patients, audio recordings of patient-provider interactions, and semi-structured interviews with providers and staff.</p> <p>Results</p> <p>The primary factors providers considered when assessing value added were whether the HRQL information from the module was (1) duplicative of information gathered via other means during the encounter; (2) specific enough to be useful and/or acted upon, and; (3) useful for enough patients to warrant time spent reviewing it for all geriatric patients. Secondary considerations included level of integration of the HRQL and EHR, impact on nursing workflow, and patient reluctance to provide HRQL information.</p> <p>Conclusions</p> <p>Health-related quality of life modules within electronic health record systems offer the potential benefit of improving patient centeredness and quality of care. However, the modules must provide benefits that are substantial and prominent in order for physicians to decide that they are worthwhile and sustainable. Implications of this study for future research include the identification of perceived "costs" as well as a foundation for operationalizing the concept of "usefulness" in the context of such modules. Finally, developers of these modules may need to make their products customizable for practices to account for variation in EHR capabilities and practice workflows.</p
Independent susceptibility markers for atrial fibrillation on chromosome 4q25
Background-: Genetic variants on chromosome 4q25 are associated with atrial fibrillation (AF). We sought to determine whether there is more than 1 susceptibility signal at this locus. Methods and results-: Thirty-four haplotype-tagging single-nucleotide polymorphisms (SNPs) at the 4q25 locus were genotyped in 790 case and 1177 control subjects from Massachusetts General Hospital and tested for association with AF. We replicated SNPs associated with AF after adjustment for the most significantly associated SNP in 5066 case and 30 661 referent subjects from the German Competence Network for Atrial Fibrillation, Atherosclerosis Risk In Communities Study, Cleveland Clinic Lone AF Study, Cardiovascular Health Study, and Rotterdam Study. All subjects were of European ancestry. A multimarker risk score composed of SNPs that tagged distinct AF susceptibility signals was constructed and tested for association with AF, and all results were subjected to meta-analysis. The previously reported SNP, rs2200733, was most significantly associated with AF (minor allele odds ratio 1.80, 95% confidence interval 1.50 to 2.15, P=1.2×10) in the discovery sample. Adjustment for rs2200733 genotype revealed 2 additional susceptibility signals marked by rs17570669 and rs3853445. A graded risk of AF was observed with an increasing number of AF risk alleles at SNPs that tagged these 3 susceptibility signals. Conclusions-: We identified 2 novel AF susceptibility signals on chromosome 4q25. Consideration of multiple susceptibility signals at chromosome 4q25 identifies individuals with an increased risk of AF and may localize regulatory elements at the locus with biological relevance in the pathogenesis of AF
Association between anthropometric indices and cardiometabolic risk factors in pre-school children
ABSTRACT: The world health organization (WHO) and the Identification and prevention of dietary- and lifestyle-induced health effects in children and infants- study (IDEFICS), released anthropometric reference values obtained from normal body weight children. This study examined the relationship between WHO [body mass index (BMI) and triceps- and subscapular-skinfolds], and IDEFICS (waist circumference, waist to height ratio and fat mass index) anthropometric indices with cardiometabolic risk factors in pre-school children ranging from normal body weight to obesity. Methods: A cross-sectional study with 232 children (aged 4.1 ± 0.05 years) was performed. Anthropometric measurements were collected and BMI, waist circumference, waist to height ratio, triceps- and subscapular-skinfolds sum and fat mass index were calculated. Fasting glucose, fasting insulin, homeostasis model analysis insulin resistance (HOMA-IR), blood lipids and apolipoprotein (Apo) B-100 (Apo B) and Apo A-I were determined. Pearson’s correlation coefficient, multiple regression analysis and the receiver-operating characteristic (ROC) curve analysis were run. Results: 51 % (n = 73) of the boys and 52 % (n = 47) of the girls were of normal body weight, 49 % (n = 69) of the boys and 48 % (n = 43) of the girls were overweight or obese. Anthropometric indices correlated (p 0.68 to AUC < 0.76). Conclusions: WHO and IDEFICS anthropometric indices correlated similarly with fasting insulin and HOMA-IR. The diagnostic accuracy of the anthropometric indices as a proxy to identify children with insulin resistance was similar. These data do not support the use of waist circumference, waist to height ratio, triceps- and subscapular- skinfolds sum or fat mass index, instead of the BMI as a proxy to identify pre-school children with insulin resistance, the most frequent alteration found in children ranging from normal body weight to obesity
African-Caribbean cancer consortium for the study of viral, genetic and environmental cancer risk factors
This is a short summary of a meeting of the "African-Caribbean Cancer Consortium", jointly organized by the University of Pittsburgh, Department of Epidemiology and the University of Pittsburgh Cancer Institute, held in Montego Bay, Jamaica as a satellite meeting at the Caribbean Health Research Council, 52nd Annual Council and Scientific meeting on May 4, 2007
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