Massively parallel approximate Gaussian process regression

We explore how the big-three computing paradigms -- symmetric multi-processor (SMC), graphical processing units (GPUs), and cluster computing -- can together be brought to bare on large-data Gaussian processes (GP) regression problems via a careful implementation of a newly developed local approximation scheme. Our methodological contribution focuses primarily on GPU computation, as this requires the most care and also provides the largest performance boost. However, in our empirical work we study the relative merits of all three paradigms to determine how best to combine them. The paper concludes with two case studies. One is a real data fluid-dynamics computer experiment which benefits from the local nature of our approximation; the second is a synthetic data example designed to find the largest design for which (accurate) GP emulation can performed on a commensurate predictive set under an hour.Comment: 24 pages, 6 figures, 1 tabl

Absorption and emission spectroscopies of homogeneous and inhomogeneously broadened multilevel systems in strong light fields

A method is introduced to calc., for a model set of mol. levels, the spectral line shapes expected for a variety of conventional laser expts. including absorption, hole burning, fluorescence line narrowing, and Raman scattering. The method allows the incident laser field to have arbitrary intensity. Furthermore, the effects of model gaussian or lorenzian inhomogeneous distributions are readily incorporated. Earlier results for a 2-level system are easily obtained and new results are presented for inhomogeneously broadened 2- and 3-level systems, and for the effects of pure dephasing on the strong field spectra. The differences between fluorescence and Raman in strong fields, and the effect of strong fields on the spontaneous emission of inhomogeneously broadened transitions were described. Some predictions are made regarding line narrowing expts. in the strong-field limit

Diffusion-annihilation dynamics in one spatial dimension

We discuss a reaction-diffusion model in one dimension subjected to an external driving force. Each lattice site may be occupied by at most one particle. The particles hop with asymmetric rates (the sum of which is one) to the right or left nearest neighbour site if it is vacant, and annihilate with rate one if it is occupied. We compute the long time behaviour of the space dependent average density in states where the initial density profiles are step functions. We also compute the exact time dependence of the particle density for uncorrelated random initial conditions. The representation of the uncorrelated random initial state and also of the step function profile in terms of free fermions allows the calculation of time-dependent higher order correlation functions. We outline the procedure using a field theoretic approach.Comment: 26 pages, 1 Postscript figure, uses epsf.st

Sympathetic cooling route to Bose-Einstein condensate and Fermi-liquid mixtures

We discuss a sympathetic cooling strategy that can successfully mitigate fermion-hole heating in a dilute atomic Fermi-Bose mixture and access the temperature regime in which the fermions behave as a Fermi liquid. We introduce an energy-based formalism to describe the temperature dynamics with which we study a specific and promising mixture composed of 6Li and 87Rb. Analyzing the harmonically trapped mixture, we find that the favourable features of this mixture are further enhanced by using different trapping frequencies for the two species.Comment: 4 pages, 2 figure

Constraining the structure and formation of the Galactic bulge from a field in its outskirts. FLAMES-GIRAFFE spectra of about 400 red giants around (l,b)=(0{\deg},-10{\deg})

The presence of two stellar populations in the Milky Way bulge has been reported recently. We aim at studying the abundances and kinematics of stars in the outer bulge, thereby providing additional constraints on models of its formation. Spectra of 401 red giant stars in a field at (l,b)=(0{\deg},-10{\deg}) were obtained with FLAMES at the VLT. Stars of luminosities down to below the two bulge red clumps (RCs) are included. From these spectra we measure general metallicities, abundances of Fe and the alpha-elements, and radial velocities (RV) of the stars. These measurements as well as photometric data are compared to simulations with the Besancon and TRILEGAL models of the Galaxy. We confirm the presence of two populations among our sample stars: i) a metal-rich one at [M/H] ~+0.3, comprising about 30% of the sample, with low RV dispersion and low alpha-abundance, and ii) a metal-poor population at [M/H] ~-0.6 with high RV dispersion and high alpha-abundance. The metal-rich population could be connected to the Galactic bar. We identify this population as the carrier of the double RC feature. We do not find a significant difference in metallicity or RV between the two RCs, a small difference in metallicity being probably due to a selection effect. The RV dispersion agrees well with predictions of the Besancon Galaxy model, but the metallicity of the "thick bulge" model component should be shifted to lower metallicity by 0.2 to 0.3dex to well reproduce the observations. We present evidence that the metallicity distribution function depends on the evolutionary state of the sample stars, suggesting that enhanced mass loss preferentially removes metal-rich stars. We also confirm the decrease of \alpha-element over-abundance with increasing metallicity.Comment: 19 pages (excluding on-line table), 21 figures, accepted for publication in A&

SlicerAstro: a 3-D interactive visual analytics tool for HI data

SKA precursors are capable of detecting hundreds of galaxies in HI in a single 12 hours pointing. In deeper surveys one will probe more easily faint HI structures, typically located in the vicinity of galaxies, such as tails, filaments, and extraplanar gas. The importance of interactive visualization has proven to be fundamental for the exploration of such data as it helps users to receive immediate feedback when manipulating the data. We have developed SlicerAstro, a 3-D interactive viewer with new analysis capabilities, based on traditional 2-D input/output hardware. These capabilities enhance the data inspection, allowing faster analysis of complex sources than with traditional tools. SlicerAstro is an open-source extension of 3DSlicer, a multi-platform open source software package for visualization and medical image processing. We demonstrate the capabilities of the current stable binary release of SlicerAstro, which offers the following features: i) handling of FITS files and astronomical coordinate systems; ii) coupled 2-D/3-D visualization; iii) interactive filtering; iv) interactive 3-D masking; v) and interactive 3-D modeling. In addition, SlicerAstro has been designed with a strong, stable and modular C++ core, and its classes are also accessible via Python scripting, allowing great flexibility for user-customized visualization and analysis tasks.Comment: 18 pages, 11 figures, Accepted by Astronomy and Computing. SlicerAstro link: https://github.com/Punzo/SlicerAstro/wiki#get-slicerastr

Exact joint density-current probability function for the asymmetric exclusion process

We study the asymmetric exclusion process with open boundaries and derive the exact form of the joint probability function for the occupation number and the current through the system. We further consider the thermodynamic limit, showing that the resulting distribution is non-Gaussian and that the density fluctuations have a discontinuity at the continuous phase transition, while the current fluctuations are continuous. The derivations are performed by using the standard operator algebraic approach, and by the introduction of new operators satisfying a modified version of the original algebra.Comment: 4 pages, 3 figure

Excited electronic states from a variational approach based on symmetry-projected Hartree--Fock configurations

Recent work from our research group has demonstrated that symmetry-projected Hartree--Fock (HF) methods provide a compact representation of molecular ground state wavefunctions based on a superposition of non-orthogonal Slater determinants. The symmetry-projected ansatz can account for static correlations in a computationally efficient way. Here we present a variational extension of this methodology applicable to excited states of the same symmetry as the ground state. Benchmark calculations on the C$_2$ dimer with a modest basis set, which allows comparison with full configuration interaction results, indicate that this extension provides a high quality description of the low-lying spectrum for the entire dissociation profile. We apply the same methodology to obtain the full low-lying vertical excitation spectrum of formaldehyde, in good agreement with available theoretical and experimental data, as well as to a challenging model $C_{2v}$ insertion pathway for BeH$_2$. The variational excited state methodology developed in this work has two remarkable traits: it is fully black-box and will be applicable to fairly large systems thanks to its mean-field computational cost

PyMT-Maclow: A novel, inducible, murine model for determining the role of CD68 positive cells in breast tumor development

CD68+ tumor-associated macrophages (TAMs) are pro-tumorigenic, pro-angiogenic and are associated with decreased survival rates in patients with cancer, including breast cancer. Non-specific models of macrophage ablation reduce the number of TAMs and limit the development of mammary tumors. However, the lack of specificity and side effects associated with these models compromise their reliability. We hypothesized that specific and controlled macrophage depletion would provide precise data on the effects of reducing TAM numbers on tumor development. In this study, the MacLow mouse model of doxycycline-inducible and selective CD68+ macrophage depletion was crossed with the murine mammary tumor virus (MMTV)-Polyoma virus middle T antigen (PyMT) mouse model of spontaneous ductal breast adenocarcinoma to generate the PyMT-MacLow line. In doxycycline-treated PyMT-MacLow mice, macrophage numbers were decreased in areas surrounding tumors by 43%. Reducing the number of macrophages by this level delayed tumor progression, generated less proliferative tumors, decreased the vascularization of carcinomas and down-regulated the expression of many pro-angiogenic genes. These results demonstrate that depleting CD68+ macrophages in an inducible and selective manner delays the development of mammary tumors and that the PyMT-MacLow model is a useful and unique tool for studying the role of TAMs in breast cancer

Integración de Tareas de Visualización Espacial para Mejorar los Niveles de Pensamiento Geométrico de los Estudiantes siguiendo el Modelo de Van Hiele: Una Base para el Desarrollo de una Guía Definitiva en Geometría

Students who have the ability to manipulate shapes in free play situations, such as building, solving spatial problems, drawing two and three-dimensional objects, exploring shapes through physical actions, describing shapes from different perspectives, and fitting shapes together are commonly observed to have a more advanced level of Geometric thinking. From this perspective students’ level of geometric thinking is associated with spatial visualization ability. Hence, the study was conducted specifically to develop a definitive guide integrating spatial visualization tasks to enhance students’ level of geometric thinking following the van Hiele model of instruction. The pre-experimental research design was employed with a definitive instructional guide as the final output of the study. The subjects of the study consist of one intact class of Bachelor of Secondary Education Major in Mathematics who are enrolled in Math 213c (Solid Geometry) during the first semester of the school year 2015-2016 purposively selected for the study. The instructional guide contains instructional plans which include worksheets, activity sheets, and homework sheets integrating students’ spatial visualization tasks. All materials which were developed in the study were subjected to face and content validation through several subject area specialists. The findings reveal that there are remarkable changes for both the students’ level of geometric thinking and spatial visualization ability. It can be concluded that the integration of spatial visualization tasks is effective not only in improving students’ spatial visualization ability but also effective in assisting students raised their van Hiele level and preventing them drop their van Hiele level.Los alumnos que tienen la capacidad de manipular las formas en situaciones de juego libre, como construir, resolver problemas espaciales, dibujar objetos bidimensionales y tridimensionales, explorar las formas mediante acciones físicas, describir las formas desde diferentes perspectivas y encajar las formas, suelen tener un nivel más avanzado de pensamiento geométrico. Desde esta perspectiva, el nivel de pensamiento geométrico de los estudiantes está asociado a la capacidad de visualización espacial. Por lo tanto, el estudio se realizó específicamente para desarrollar una guía definitiva que integrara tareas de visualización espacial para mejorar el nivel de pensamiento geométrico de los estudiantes siguiendo el modelo de instrucción de van Hiele. Se empleó el diseño de investigación preexperimental con una guía de instrucción definitiva como resultado final del estudio. Los sujetos del estudio consisten en una clase intacta de la Licenciatura en Educación Secundaria con especialización en Matemáticas que están inscritos en Matemáticas 213c (Geometría Sólida) durante el primer semestre del año escolar 2015-2016 seleccionados intencionalmente para el estudio. La guía didáctica contiene planes de instrucción que incluyen hojas de trabajo, hojas de actividades y hojas de tareas que integran las tareas de visualización espacial de los estudiantes. Todos los materiales que se desarrollaron en el estudio fueron sometidos a una validación facial y de contenido a través de varios especialistas en la materia. Los resultados revelan que hay cambios notables tanto en el nivel de pensamiento geométrico como en la capacidad de visualización espacial de los alumnos. Se puede concluir que la integración de las tareas de visualización espacial es eficaz no sólo para mejorar la capacidad de visualización espacial de los estudiantes, sino también para ayudar a los estudiantes a elevar su nivel de van Hiele y evitar que bajen su nivel de van Hiele.Os estudantes que têm a capacidade de manipular formas em situações de jogo livre, como construir, resolver problemas espaciais, desenhar objetos tridimensionais e tridimensionais, explorar formas através de ações físicas, descrever formas de diferentes perspectivas e ajustar formas são comumente observados para ter um nível avançado de pensamento geométrico. A partir dessa perspectiva, o nível de pensamento geométrico do aluno está associado à capacidade de visualização espacial. Assim, o estudo foi conduzido especificamente para desenvolver um guia definitivo integrando tarefas de visualização espacial para melhorar o nível de pensamento geométrico dos alunos seguindo o modelo de instrução de van Hiele. Projeto de pesquisa pré-experimental foi empregado com guia instrutivo definitivo como o resultado final do estudo. Os sujeitos do estudo consistem em uma classe intacta de Bacharel em Educação Secundária Maior em Matemática que estão matriculados na Matemática 213c (Geometria Sólida) durante o primeiro semestre do ano letivo de 2015-2016 propositadamente selecionados para o estudo. O guia de instrução contém planos de instrução que incluem planilhas, folhas de atividades e folhas de trabalhos de casa que integram as tarefas de visualização espacial dos alunos. Todos os materiais que foram desenvolvidos no estudo foram submetidos a validação de rosto e conteúdo através de vários especialistas da área. As descobertas revelam que há mudanças notáveis ​​tanto no nível de pensamento geométrico dos alunos quanto na capacidade de visualização espacial. Pode-se concluir que a integração das tarefas de visualização espacial é eficaz não só para melhorar a capacidade de visualização espacial dos alunos, mas também para ajudar os alunos a elevar o nível de van Hiele e impedir que abandonem o nível de van Hiele