Computing singularities of perturbation series

Many properties of current \emph{ab initio} approaches to the quantum many-body problem, both perturbational or otherwise, are related to the singularity structure of Rayleigh--Schr\"odinger perturbation theory. A numerical procedure is presented that in principle computes the complete set of singularities, including the dominant singularity which limits the radius of convergence. The method approximates the singularities as eigenvalues of a certain generalized eigenvalue equation which is solved using iterative techniques. It relies on computation of the action of the perturbed Hamiltonian on a vector, and does not rely on the terms in the perturbation series. Some illustrative model problems are studied, including a Helium-like model with $\delta$-function interactions for which M{\o}ller--Plesset perturbation theory is considered and the radius of convergence found.Comment: 11 figures, submitte

An approach towards rapid optical measurements of antioxidant activity in blueberry cultivars

Blueberries are well known for their high antioxidant levels. Compared to bilberries (V. myrtillus) with higher antioxidant activity and more intensive blue colour throughout the whole berry, highbush blueberries have the blue pigments concentrated in the skin. Highbush blueberry skin is found to contain a very high content of phenolic compounds. To measure the total antioxidant activity in blueberries, several methods, mostly destructive, including the FRAP assay, have been used. This work is an initial approach towards a simple and rapid method, combining optical and antioxidant activity measurements. Highbush blueberry (V. corymbosum) cultivars ‘Bluecrop’, ‘Hardyblue’, ‘Patriot’, and lowbush cultivars ‘Putte’ (a hybrid originated from V. angustifolium) and ‘Aron’ (V. corymbosum x V. uliginosum) were grown at the Norwegian University of Life Sciences (59º 40’N). Berries were harvested at commercial blue-ripe stage of maturity. Fresh berries were cut horizontally and placed on a scanner in order to examine berry size and skin thickness. Berries were weighed, and analysed for antioxidant activity using the FRAP (Ferric Reducing Ability of Plasma) assay. The FRAP assay is a non-specific method based on absorption changes following a reduction of a ferric- to a ferrous-complex in the presence of antioxidants.Own previous results have shown that antioxidant activity and berry weight varied between cultivars (REMBERG et al., 2003). Small berries had higher antioxidant activity compared to larger berries. In this follow-up project, skin thickness and berry diameter were measured by using an image- processing program. Berry and skin cross-section areas were correlated with the antioxidant activity

Effective interactions and large-scale diagonalization for quantum dots

The widely used large-scale diagonalization method using harmonic oscillator basis functions (an instance of the Rayleigh-Ritz method, also called a spectral method, configuration-interaction method, or ``exact diagonalization'' method) is systematically analyzed using results for the convergence of Hermite function series. We apply this theory to a Hamiltonian for a one-dimensional model of a quantum dot. The method is shown to converge slowly, and the non-smooth character of the interaction potential is identified as the main problem with the chosen basis, while on the other hand its important advantages are pointed out. An effective interaction obtained by a similarity transformation is proposed for improving the convergence of the diagonalization scheme, and numerical experiments are performed to demonstrate the improvement. Generalizations to more particles and dimensions are discussed.Comment: 7 figures, submitted to Physical Review B Single reference error fixe

Levels of State and Trait Anxiety in Patients Referred to Ophthalmology by Primary Care Clinicians: A Cross Sectional Study

Purpose There is a high level of over-referral from primary eye care leading to significant numbers of people without ocular pathology (false positives) being referred to secondary eye care. The present study used a psychometric instrument to determine whether there is a psychological burden on patients due to referral to secondary eye care, and used Rasch analysis to convert the data from an ordinal to an interval scale. Design Cross sectional study. Participants and Controls 322 participants and 80 control participants. Methods State (i.e. current) and trait (i.e. propensity to) anxiety were measured in a group of patients referred to a hospital eye department in the UK and in a control group who have had a sight test but were not referred. Response category analysis plus infit and outfit Rasch statistics and person separation indices were used to determine the usefulness of individual items and the response categories. Principal components analysis was used to determine dimensionality. Main Outcome Measure Levels of state and trait anxiety measured using the State-Trait Anxiety Inventory. Results State anxiety scores were significantly higher in the patients referred to secondary eye care than the controls (p0.1). Rasch analysis highlighted that the questionnaire results needed to be split into “anxiety-absent” and “anxiety-present” items for both state and trait anxiety, but both subscales showed the same profile of results between patients and controls. Conclusions State anxiety was shown to be higher in patients referred to secondary eye care than the controls, and at similar levels to people with moderate to high perceived susceptibility to breast cancer. This suggests that referral from primary to secondary eye care can result in a significant psychological burden on some patients

The Set3/Hos2 Histone Deacetylase Complex Attenuates cAMP/PKA Signaling to Regulate Morphogenesis and Virulence of Candida albicans

Candida albicans, like other pleiomorphic fungal pathogens, is able to undergo a reversible transition between single yeast-like cells and multicellular filaments. This morphogenetic process has long been considered as a key fungal virulence factor. Here, we identify the evolutionarily conserved Set3/Hos2 histone deacetylase complex (Set3C) as a crucial repressor of the yeast-to-filament transition. Cells lacking core components of the Set3C are able to maintain all developmental phases, but are hypersusceptible to filamentation-inducing signals, because of a hyperactive cAMP/Protein Kinase A signaling pathway. Strikingly, Set3C-mediated control of filamentation is required for virulence in vivo, since set3Δ/Δ cells display strongly attenuated virulence in a mouse model of systemic infection. Importantly, the inhibition of histone deacetylase activity by trichostatin A exclusively phenocopies the absence of a functional Set3C, but not of any other histone deacetylase gene. Hence, our work supports a paradigm for manipulating morphogenesis in C. albicans through alternative antifungal therapeutic strategies

Incorporating Genomics and Bioinformatics across the Life Sciences Curriculum

Undergraduate life sciences education needs an overhaul, as clearly described in the National Research Council of the National Academies’ publication BIO 2010: Transforming Undergraduate Education for Future Research Biologists. Among BIO 2010’s top recommendations is the need to involve students in working with real data and tools that reflect the nature of life sciences research in the 21st century [1]. Education research studies support the importance of utilizing primary literature, designing and implementing experiments, and analyzing results in the context of a bona fide scientific question [1–12] in cultivating the analytical skills necessary to become a scientist. Incorporating these basic scientific methodologies in undergraduate education leads to increased undergraduate and post-graduate retention in the sciences [13–16]. Toward this end, many undergraduate teaching organizations offer training and suggestions for faculty to update and improve their teaching approaches to help students learn as scientists, through design and discovery (e.g., Council of Undergraduate Research [www.cur.org] and Project Kaleidoscope [ www.pkal.org])