A time-dependent variational principle for dissipative dynamics

We extend the time-dependent variational principle to the setting of dissipative dynamics. This provides a locally optimal (in time) approximation to the dynamics of any Lindblad equation within a given variational manifold of mixed states. In contrast to the pure-state setting there is no canonical information geometry for mixed states and this leads to a family of possible trajectories --- one for each information metric. We focus on the case of the operationally motivated family of monotone riemannian metrics and show further, that in the particular case where the variational manifold is given by the set of fermionic gaussian states all of these possible trajectories coincide. We illustrate our results in the case of the Hubbard model subject to spin decoherence.Comment: Published versio

The benefits of combining seasonal anomalies and technical trading rules

Although many seasonal anomalies and technical trading rules have been shown to have predictive ability, investigations have focused only on them operating individually. We study the benefits of trading based on combinations of three of the best known effects: the moving average rule, the turn of the month effect, and the Halloween effect. We show that the rules can be combined effectively, giving significant levels of returns predictability with low risk and offering the possibility of profitable trading. This new investment approach is especially beneficial for a typical individual investor, who faces high transaction costs and is poorly diversified

Ground States of Fermionic lattice Hamiltonians with Permutation Symmetry

We study the ground states of lattice Hamiltonians that are invariant under permutations, in the limit where the number of lattice sites, N -> \infty. For spin systems, these are product states, a fact that follows directly from the quantum de Finetti theorem. For fermionic systems, however, the problem is very different, since mode operators acting on different sites do not commute, but anti-commute. We construct a family of fermionic states, \cal{F}, from which such ground states can be easily computed. They are characterized by few parameters whose number only depends on M, the number of modes per lattice site. We also give an explicit construction for M=1,2. In the first case, \cal{F} is contained in the set of Gaussian states, whereas in the second it is not. Inspired by that constructions, we build a set of fermionic variational wave functions, and apply it to the Fermi-Hubbard model in two spatial dimensions, obtaining results that go beyond the generalized Hartree-Fock theory.Comment: 23 pages, published versio

Oral Hygiene Facilitators and Barriers in Greek 10 Years Old Schoolchildren

Aim: The aim of this study was to determine the oral hygiene facilitators and barriers for 10 years old Greek children, via a questionnaire and clinical examination. Materials and Methods: This was a cross-sectional study of 266, 10 years old, children recruited from schools in 3 locations in Greece. Data were collected via questionnaires and clinical examination. Questionnaires referred to children\u27s oral hygiene knowledge, behavior and attitude as well as parents\u27 oral hygiene behavior and educational level. Children were clinically examined by two calibrated pediatric dentists using a WHO probe and artificial light to assess dental plaque (hygiene index-HI), gingivitis (simplified gingival index-GIs) and dental caries (DMFT-BASCD criteria). Results: Regarding oral hygiene knowledge, although 80% of the children were literate of the proper means of oral hygiene, only 58.64% brushed their teeth twice daily and 36.84% used dental floss. Children\u27s oral hygiene knowledge was positively correlated with both parental brushing frequency (ρ = 0.175, p \u3c 0.05) and educational level (ρ = -0.216, p \u3c 0.05). Toothpaste use was reported by 92.11% of the children. Regarding children\u27s attitude, 62.28% were concerned whether their teeth were clean, with girls showing greater concern than boys (p \u3c 0.001). Their reported beliefs regarding brushing avoidance were boredom (84.06%), low oral health literacy (73.91%) and forgetfulness (56.52%). Conclusion: Oral hygiene facilitators were found to be the concern about how clean were their teeth, oral health literacy of both children and parents and toothpaste appeal to children. Oral hygiene barriers were children\u27s boredom, low oral health literacy, forgetfulness and low socioeconomic level

Exploring Ecological Factors Influencing Economic Advocacy for Domestic Violence Survivors

Domestic violence advocates accompany and support victims as they navigate community systems (e.g. legal, medical, and social) to obtain needed services and prevent future partner violence. Research suggests victims believe economic services will increase their sense of safety in abusive relationships. Although advocates acknowledge economic services are critical to victims’ safety, the ecological factors that impact how advocates are providing these services have not been examined in the literature. The purpose of this study is to explore the factors that challenge and facilitate advocates’ work with domestic violence survivors around economic/financial issues from an ecological perspective. Qualitative interviews were conducted with 20 domestic violence advocates in the state of Illinois to understand their experiences working with survivors on economic/financial issues. Findings help to identify what advocates and domestic violence programs need to be more effective at working with survivors around economic/financial issues. This can help inform training, technical assistance, funding, and other resources for working with women on economic services

Space Biosciences Division

In the Space Biosciences Division at NASA's Ames Research Center, we perform the biological research and technology development necessary to tackle the challenges of living in the extreme environments of space and to enable NASA's long-term human exploration mission. This brochure provides a broad overview for our research and development capabilities, several case study examples, and finally real-world applications and collaborative partnerships