Excitons and biexcitons in symmetric electron-hole bilayers

Symmetric electron-hole bilayer systems have been studied at zero temperature using the diffusion quantum Monte Carlo method. A flexible trial wave function is used that can describe fluid, excitonic and biexcitonic phases. We calculate condensate fractions and pair correlation functions for a large number of densities rs and layer separations d. At small d we find a one-component fluid phase, an excitonic fluid phase, and a biexcitonic fluid phase, and the transitions among them appear to be continuous. At d = 0, excitons appear to survive down to about rs = 0.5 a.u., and biexcitons form at rs > 2.5 a.u.Comment: 5 pages, 4 figure

Tail-regression estimator for heavy-tailed distributions of known tail indices and its application to continuum quantum Monte Carlo data.

Standard statistical analysis is unable to provide reliable confidence intervals on expectation values of probability distributions that do not satisfy the conditions of the central limit theorem. We present a regression-based estimator of an arbitrary moment of a probability distribution with power-law heavy tails that exploits knowledge of the exponents of its asymptotic decay to bypass this issue entirely. Our method is applied to synthetic data and to energy and atomic force data from variational and diffusion quantum Monte Carlo calculations, whose distributions have known asymptotic forms [J. R. Trail, Phys. Rev. E 77, 016703 (2008)PLEEE81539-375510.1103/PhysRevE.77.016703; A. Badinski et al., J. Phys.: Condens. Matter 22, 074202 (2010)JCOMEL0953-898410.1088/0953-8984/22/7/074202]. We obtain convergent, accurate confidence intervals on the variance of the local energy of an electron gas and on the Hellmann-Feynman force on an atom in the all-electron carbon dimer. In each of these cases the uncertainty on our estimator is 45% and 60 times smaller, respectively, than the nominal (ill-defined) standard error

Functional Information Stored in the Conserved Structural RNA Domains of Flavivirus Genomes

The genus Flavivirus comprises a large number of small, positive-sense single-stranded, RNA viruses able to replicate in the cytoplasm of certain arthropod and/or vertebrate host cells. The genus, which has some 70 member species, includes a number of emerging and re-emerging pathogens responsible for outbreaks of human disease around the world, such as the West Nile, dengue, Zika, yellow fever, Japanese encephalitis, St. Louis encephalitis, and tick-borne encephalitis viruses. Like other RNA viruses, flaviviruses have a compact RNA genome that efficiently stores all the information required for the completion of the infectious cycle. The efficiency of this storage system is attributable to supracoding elements, i.e., discrete, structural units with essential functions. This information storage system overlaps and complements the protein coding sequence and is highly conserved across the genus. It therefore offers interesting potential targets for novel therapeutic strategies. This review summarizes our knowledge of the features of flavivirus genome functional RNA domains. It also provides a brief overview of the main achievements reported in the design of antiviral nucleic acid-based drugs targeting functional genomic RNA elements.Work in our laboratory is supported by the Spanish Ministerio de Economía y Competitividad (BFU2012-31213 and BFU2015-64359-P) and the Consejería de Economía Innovación, Ciencia y Empleo, Junta de Andalucía (CVI-7430). It is also partially funded by FEDER funds from the EU.The authors also acknowledge support of the publication fee by the CSIC Open Access Publication Support Initiative through its Unit of Information Resources for Research (URICI).Peer reviewedPeer Reviewe

Efficient treatment of three-body interactions in transcorrelated methods

An efficient implementation for approximate inclusion of the three-body operator arising in transcorrelated methods via exclusion of explit three body correlation (xTC) is presented and tested against results in the ``HEAT'' benchmark set [A. Tajti et al., J. Chem. Phys. 121, 11599 (2004)]. Using relatively modest basis sets and computationally simple methods, total, atomization, and formation energies within near-chemical accuracy from HEAT results were obtained. The xTC ansatz reduces the nominal scaling of the three-body part of transcorrelation by two orders of magnitude to O(N^5) and can readily be used with almost any quantum chemical correlation method

Management of Entrepreneurship Projects from Project‐Based Learning: Coworking StartUPS Project at Universidad Politécnica Salesiana (Salesian Polytechnic University), Ecuador

In the engineering education field, there is an identified need of innovative learning and teaching methods to improve students’ entrepreneurship competencies in order to make connections between engineering and real society. This chapter addresses a management strategy for entrepreneurship projects in the university framework. It is the result of a cooperative experience from the Research Groups of Salesian Polytechnic University (UPS), the Technical University of Madrid (UPM), and the collaboration of other external entities. The management strategy is applied to undergraduate and postgraduate programs at UPS and has been called Coworking StartUPS Project. The research method is made up of different teaching methodologies—project‐based learning, coworking, case studies—and different activities in and out of the university. The data were collected from students who were enrolled in the Coworking StartUPS Project, along with students and researchers from the three University Branch Campuses in the cities of Cuenca, Quito, and Guayaquil. The Coworking StartUPS Project links teaching & research activities with entrepreneurship are founded in cooperation and interaction, offering multiple possibilities for entrepreneurial skills development in the international context. This preprofessional experience promotes students to integrate the knowledge they have learnt and apply the new knowledge in an entrepreneurship project

Bonding Situation of σ‐E−H Complexes in Transition Metal and Main Group Compounds

The ambiguous bonding situation of σ-E−H (E=Si, B) complexes in transition metal compounds has been rationalized by means of Density Functional Theory calculations. To this end, the combination of the Energy Decomposition Analysis (EDA) method and its Natural Orbital for Chemical Valance (NOCV) extension has been applied to representative complexes described in the literature where the possible η1 versus η2 coordination mode is not unambiguously defined. Our quantitative analyses, which complement previous data based on the application of the Quantum Theory of Atoms in Molecules (QTAIM) approach, indicate that there exists a continuum between genuine η1 and η2 modes depending mainly on the strength of the backdonation. Finally, we also applied this EDA-NOCV approach to related main-group species where the backdonation is minimal

El gasto regional por funciones: Análisis y clasificación de las ccaa

El objetivo de la financiación autonómica es dotar a las regiones de los recursos para financiar las competencias transferidas, sin embargo, nos parecía que una cuestión que había sido poco tratada por la literatura era el comportamiento del gasto autonómico por funciones, por esta razón el objetivo principal de este trabajo es el análisis de los gastos de las CCA según dicha clasificación, durante el período comprendido entre los años 1989 y 2002. El estudio se estructura en dos partes diferenciadas, aunque complementarias: por una parte se calcula un índice de disimilitud, en concreto el que emplean Sanz y Velázquez (2002) para, en una segunda parte, realizar una clasificación de las CCA de régimen común según la estructura funcional del gasto. El estudio nos permite extraer conclusiones sobre las siguientes cuestiones: qué gastos explican las similitudes entre CCAA , qué regiones se asemejan en cuanto a la composición del gasto, y si en el periodo analizado se ha producido una convergencia de las regiones por tipos de gasto o si, por el contrario, las diferencias han ido aumentando

Choline kinase inhibitors EB-3D and EB-3P interferes with lipid homeostasis in HepG2 cells

A full understanding of the molecular mechanism of action of choline kinase α (ChoKα) inhibitors at the cell level is essential for developing therapeutic and preventive approaches for cancer. The aim of the present study was to evaluate the effects of the ChoKα inhibitors EB-3D and EB-3P on lipid metabolism in HepG2 cells. We used [methyl-14C]choline, [1,2-14C]acetic acid and [2-3H]glycerol as exogenous precursors of the corresponding phospholipids and neutral lipids. [Methyl-14C]choline was also used to determine choline uptake. Protein levels were determined by Western blot. Ultrastructural alterations were investigated by transmission electron microscopy. In this work, we demonstrate that EB-3D and EB-3P interfere with phosphatidylcholine biosynthesis via both CDP-choline pathway and choline uptake by the cell. Moreover, the synthesis of both diacylglycerols and triacylglycerols was affected by cell exposure to both inhibitors. These effects were accompanied by a substantial decrease in cholesterol biosynthesis, as well as alterations in the expression of proteins related to cholesterol homeostasis. We also found that EB-3D and EB-3P lowered ChoKα protein levels. All these effects could be explained by the modulation of the AMP-activated protein kinase signalling pathway. We show that both inhibitors cause mitochondrial alteration and an endoplasmic reticulum stress response. EB-3D and EB-3P exert effects on ChoKα expression, AMPK activation, apoptosis, endoplasmic reticulum stress and lipid metabolism. Taken together, results show that EB-3D and EB-3P have potential anticancer activity through the deregulation of lipid metabolism.This work was aided by the Andalusian Regional Government (P11-CVI-7859). The inhibitors were developed under the Cei-Biotic Project CEI2013-MP-1 (University of Granada)