Benchmark calculations for reduced density-matrix functional theory

Reduced density-matrix functional theory (RDMFT) is a promising alternative approach to the problem of electron correlation. Like standard density functional theory, it contains an unknown exchange-correlation functional, for which several approximations have been proposed in the last years. In this article, we benchmark some of these functionals in an extended set of molecules with respect to total and atomization energies. Our results show that the most recent RDMFT functionals give very satisfactory results compared to more involved quantum chemistry and density functional approaches.Comment: 17 pages, 1 figur

Generalized Pauli constraints in reduced density matrix functional theory

Functionals of the one-body reduced density matrix (1-RDM) are routinely minimized under Coleman's ensemble $N$-representability conditions. Recently, the topic of pure-state $N$-representability conditions, also known as generalized Pauli constraints, received increased attention following the discovery of a systematic way to derive them for any number of electrons and any finite dimensionality of the Hilbert space. The target of this work is to assess the potential impact of the enforcement of the pure-state conditions on the results of reduced density-matrix functional theory calculations. In particular, we examine whether the standard minimization of typical 1-RDM functionals under the ensemble $N$-representability conditions violates the pure-state conditions for prototype 3-electron systems. We also enforce the pure-state conditions, in addition to the ensemble ones, for the same systems and functionals and compare the correlation energies and optimal occupation numbers with those obtained by the enforcement of the ensemble conditions alone

Relating correlation measures: the importance of the energy gap

The concept of correlation is central to all approaches that attempt the description of many-body effects in electronic systems. Multipartite correlation is a quantum information theoretical property that is attributed to quantum states independent of the underlying physics. In quantum chemistry, however, the correlation energy (the energy not seized by the Hartree-Fock ansatz) plays a more prominent role. We show that these two different viewpoints on electron correlation are closely related. The key ingredient turns out to be the energy gap within the symmetry-adapted subspace. We then use a few-site Hubbard model and the stretched H$_2$ to illustrate this connection and to show how the corresponding measures of correlation compare.Comment: 6 pages, 3 figure

Networked Hospitality and Placemaking in the Sharing Economy

This article investigates the similarities and differences for tangible and intangible elements (factors and language use) contributing to placemaking in Airbnb English language reviews in Paris (59,057 reviews), Barcelona (19,291 reviews) and London (30,403 reviews). This paper contributes to provide new insights on the narrative construction of reputational capital which is connected to placemaking strategies. A combined quantitative approach using large scale text analysis enabled the analysis of review content and style. Patterns in the words usage were identified. Findings suggest that tangible and intangible elements work together in the discourse, contributing to the place-narrative built on the host’s reputational capital. The host-guest interaction is the main aspect of the reviews, followed by the importance of transport and local amenities. Cities have different profiles in the composition of the word clusters which indicates differences in the guests’ perceived experience. Keywords: Hospitality; Sharing economy; Placemaking; Airbnb, Narrative, Reputational capita

The complexity of neuropsychiatric manifestations of COVID-19 in South Africa

SARS-CoV-2 was first identified in Wuhan City, China, in 2019. Initially it was associated with the development of pulmonary disease, but research over the past 2 years has identified effects on multiple systems. Neuropsychiatric manifestations of COVID-19 have been reported in countries around the world, including new-onset psychosis in patients with no personal or family psychiatric history. We present the first case series describing neuropsychiatric manifestations of patients in Johannesburg, South Africa (SA). All four patients presented with their index-episode psychosis, and evidence of COVID-19 infection. The patients had varied psychiatric presentations, from delirium and psychosis to mania, and all responded well to low doses of antipsychotics. One patient had newly diagnosed HIV in addition to COVID-19. Further research is needed to determine the prevalence of neuropsychiatric manifestations in acute SARS-CoV-2 infections in SA

Tonsillar ulceration as manifestation of disseminated African histoplasmosis in an immunocompetent Portuguese host

Free PMC Article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5466580/Histoplasmosis is a systemic mycosis caused by Histoplasma capsulatum. Rare in Europe but endemic in some regions of Brazil, United States, Africa and Asia. Most of the cases are asymptomatic. Disseminated form is defined by the presence of an extra-pulmonary focus, particularly associated with immunosuppression. We report a case of an unilateral persisted tonsillar ulceration, in an immunocompetent Portuguese host, as manifestation of disseminated African histoplasmosis 45 years later after living 3 years in Africa.info:eu-repo/semantics/publishedVersio

Tonsillar ulceration as manifestation of disseminated African histoplasmosis in an immunocompetent Portuguese host

Free PMC Article: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5466580/Histoplasmosis is a systemic mycosis caused by Histoplasma capsulatum. Rare in Europe but endemic in some regions of Brazil, United States, Africa and Asia. Most of the cases are asymptomatic. Disseminated form is defined by the presence of an extra-pulmonary focus, particularly associated with immunosuppression. We report a case of an unilateral persisted tonsillar ulceration, in an immunocompetent Portuguese host, as manifestation of disseminated African histoplasmosis 45 years later after living 3 years in Africa.info:eu-repo/semantics/publishedVersio

A time-dependent density functional theory scheme for efficient calculations of dynamic (hyper)polarizabilities

We present an efficient perturbative method to obtain both static and dynamic polarizabilities and hyperpolarizabilities of complex electronic systems. This approach is based on the solution of a frequency dependent Sternheimer equation, within the formalism of time-dependent density functional theory, and allows the calculation of the response both in resonance and out of resonance. Furthermore, the excellent scaling with the number of atoms opens the way to the investigation of response properties of very large molecular systems. To demonstrate the capabilities of this method, we implemented it in a real-space (basis-set free) code, and applied it to benchmark molecules, namely CO, H2O, and paranitroaniline (PNA). Our results are in agreement with experimental and previous theoretical studies, and fully validate our approach.Comment: 9 pages, 4 figure

Estimativa do parentesco numa população de melhoramento de Eucalyptus globulus através de microsatélites nucleares

É situação comum desconhecer-se o grau de parentesco entre a população na origem da maioria dos programas de melhoramento genético de espécies florestais. Para resolver este problema, desenvolvemos um protocolo de avaliação do parentesco utilizando 125 indivíduos e 16 microssatélites, da população base ou de referência (PR) de Eucalyptus globulus do RAIZ. Através da recombinação gamética in silico foram simulados 105 indivíduos com diferentes graus de parentesco: descendentes de autopolinização, meiosirmãos, irmãos completos e indivíduos não aparentados. Por simulação Monte-Carlo foram calculados o valor médio e a variância associada à média dos diferentes grupos de parentesco, com quatro coeficientes de similaridade genética. Compararam-se as funções densidade dos diferentes grupos de parentesco, obtidas com quatro coeficientes de parentesco, utilizando o valor crítico correspondente à intercepção das funções densidade dos indivíduos não aparentados e dos meios-irmãos. O estimador escolhido foi aplicado à PR. Detectaram-se 4,4% de pares de indivíduos potencialmente aparentados, com um erro de tipo II de 8%. Inferimos também, o parentesco de um conjunto de 24 clones elite e encontrámos 4 pares que são potencialmente aparentados. Futuros cruzamentos entre estes indivíduos deverão ser evitados