232 research outputs found
Dynamical Mean-Field Theory Simulations with the Adaptive Sampling Configuration Interaction Method
In the pursuit of accurate descriptions of strongly correlated quantum
many-body systems, dynamical mean-field theory (DMFT) has been an invaluable
tool for elucidating the spectral properties and quantum phases of both
phenomenological models and ab initio descriptions of real materials. Key to
the DMFT process is the self-consistent map of the original system into an
Anderson impurity model, the ground state of which is computed using an
impurity solver. The power of the method is thus limited by the complexity of
the impurity model the solver can handle. Simulating realistic systems
generally requires many correlated sites. By adapting the recently proposed
adaptive sampling configuration interaction (ASCI) method as an impurity
solver, we enable much more efficient zero temperature DMFT simulations. The
key feature of the ASCI method is that it selects only the most relevant
Hilbert space degrees of freedom to describe the ground state. This reduces the
numerical complexity of the calculation, which will allow us to pursue future
DMFT simulations with more correlated impurity sites than in previous works.
Here we present the ASCI-DMFT method and example calculations on the
one-dimensional and two-dimensional Hubbard models that exemplify its efficient
convergence and timing properties. We show that the ASCI approach is several
orders of magnitude faster than the current best published ground state DMFT
simulations, which allows us to study the bath discretization error in
simulations with small clusters, as well as to address cluster sizes beyond the
current state of the art. Our approach can also be adapted for other embedding
methods such as density matrix embedding theory and self-energy embedding
theory.Comment: 12 pages, 11 figures, supplemental informatio
Evolution and Modern Approaches for Thermal Analysis of Electrical Machines
In this paper, the authors present an extended survey on the evolution and the modern approaches in the thermal analysis of electrical machines. The improvements and the new techniques proposed in the last decade are analyzed in depth and compared in order to highlight the qualities and defects of each. In particular, thermal analysis based on lumped-parameter thermal network, finite-element analysis, and computational fluid dynamics are considered in this paper. In addition, an overview of the problems linked to the thermal parameter determination and computation is proposed and discussed. Taking into account the aims of this paper, a detailed list of books and papers is reported in the references to help researchers interested in these topics
Matrix solid-phase dispersion followed by liquid chromatographytandem mass spectrometry for the determination of selectiveciclooxygenase-2 inhibitors in sewage sludge samples
A straightforward single-step extraction method based on matrix solid-phase dispersion (MSPD), followed by high-performance liquid chromatography with hybrid quadrupole time of flight mass spectrometry (LC–QTOF-MS), was developed and optimized to determine five non-steroidal anti-inflammatory drugs (Valdecoxib, Etoricoxib, Parecoxib, Celecoxib and 2,5-Dimethylcelecoxib) in sewage sludge samples. The influence of different operational parameters on the extraction efficiency a well as in the matrix effects of the produced extracts was evaluated in detail. Under final working conditions, freeze dried samples (0.2 g) were first soaked with 100 μL of aqueous potassium hydroxide solution (60%, w/v), mixed with 1 g of anhydrous sodium sulfate and dispersed with 1 g of Florisil. This blend was transferred to the top of a polypropylene column cartridge containing 3 g of silica. Analytes were recovered using 15 mL of hexane/acetone (1:2, v/v) mixture. The extracts were concentrated by evaporation and reconstituted with 1 mL of methanol/water (1:1, v/v), filtered and injected in the LC system. Quantification limits from 0.005 and 0.05 ng g−1 and absolute recoveries between 86 and 105% were achieved. Results indicated the presence of two of the targeted COXIBs in real samples of sewage sludge, the highest average concentration (22 ng g−1) corresponding to celecoxib. Moreover, the screening capabilities of the LC–QTOF-MS system demonstrated that the developed MSPD extraction procedure might be useful for the selective extraction of some other pharmaceuticals (e.g. amiodarone and their metabolite N-desethylamiodarone, miconazole, clotrimazole and ketoprofen) from sludge samplesThis study has been supported by the Spanish Government and E.U. FEDER funds (project CTQ2015-68660-P) and Xunta de Galicia (GRC2013/020)S
Visual acuity and olfatory sensitivity in the swordfish (Xiphias gladius) for the detection of prey during field experiments using the surface longline gear with different bait types
During a total of 20 sets carried out on board a surface longliner, the different degrees of
effectiveness obtained in the capture of swordfish were evaluated using 5 different bait types
(natural, artificial and mixed). The results point to substantial and significant differences in the
CPUEs obtained among the different bait types tested to catch swordfish. However, the results
show few mean differences that were not statistically significant between the CPUEs obtained
using natural bait (control) or mixed bait consisting of artificial bait on the outside -which in
itself was of null effectiveness- into which was inserted a piece of natural bait, concealed from
view. Both types of bait (control and mixed) were effective in the capture of swordfish despite
the differences in constitution and properties. On the basis of these results, it is possible to make
an indirect assessment of the importance of visual and odor stimuli in the swordfish to detect
and carry out the final attack on its prey. Odor was found to be the key element in this process
Decision Support in Patients with mild Alzheimer’s Disease.
Introduction: Making advantageous decisions is a key competence of individuals of all ages. However, previous studies reported a reduction of this competence in patients with neurodegenerative diseases such as Alzheimer’s disease, which is explained by impairments of executive functions such as cognitive flexibility or working memory. While previous findings from healthy participants with reduced executive functions showed that support can improve decision making under risk, the study at hand aimed to investigate this effect in patients with mild Alzheimer’s disease (mAD).
Method: A group of elderly individuals diagnosed with mAD (n = 14; mean Mini-Mental State Examination, MMSE = 24.14, SD = 3.18) and a group of healthy age-matched controls (n = 14; mean MMSE = 29.29, SD = 1.98) performed the Game of Dice Task (GDT) three times (t0, t1, t2) with intervals of five to nine days between each: The standard GDT plus other neurocognitive tasks (t0), the GDT with decision support (t1), and again the standard GDT (t2).
Results: At any time, mAD patients made more disadvantageous decisions than controls. However, the decision-making performance of mAD patients improved significantly with decision support. Interestingly, when the standard GDT was played again (t2), mAD patients’ performance remained similar to the performance in the GDT with decision support (t1). GDT performance correlated consistently with executive function measures in the control group, but only at t0 in the mAD group.
Conclusions: The findings indicate that supportive information about the riskiness of options can compensate for mAD-related deficits in decision making under risk. Thus, decision support can improve the quality of mAD patients’ decisions. Further, it may prevent mAD patients from making highly risky decisions in similar situations in the future. The persistence of decision support should be further investigated as it has relevant implications for everyday decisions that include risks.pre-print577 K
A Parallel, Distributed Memory Implementation of the Adaptive Sampling Configuration Interaction Method
Many-body simulations of quantum systems is an active field of research that
involves many different methods targeting various computing platforms. Many
methods commonly employed, particularly coupled cluster methods, have been
adapted to leverage the latest advances in modern high-performance
computing.Selected configuration interaction (sCI) methods have seen extensive
usage and development in recent years. However development of sCI methods
targeting massively parallel resources has been explored only in a few research
works. In this work, we present a parallel, distributed memory implementation
of the adaptive sampling configuration interaction approach (ASCI) for sCI. In
particular, we will address key concerns pertaining to the parallelization of
the determinant search and selection, Hamiltonian formation, and the
variational eigenvalue calculation for the ASCI method. Load balancing in the
search step is achieved through the application of memory-efficient determinant
constraints originally developed for the ASCI-PT2 method. Presented benchmarks
demonstrate parallel efficiency exceeding 95\% for the variational ASCI
calculation of Cr (24e,30o) with , and variational
determinants up to 16,384 CPUs. To the best of the authors' knowledge, this is
the largest variational ASCI calculation to date.Comment: 32 pages, 4 figure
A Cultural Comparison of the ''Dark Constellations'' in the Milky Way
Cultures around the world find meaning in the groupings of stars and features in the Milky Way. The striking appearance of our Galaxy in the night sky serves as a reference to traditional knowledge, encoding science and culture to a memory space, becoming part of their overarching cosmologies. This paper examines traditional views of the Milky Way from cultures around the world, primarily in the Southern Hemisphere. These views comprise dark constellations: familiar shapes made up of the dark dust lanes in the Milky Way, rather than the bright stars. Some of the better-known examples include the celestial emu from Aboriginal traditions of Australia, and the llama in Inca traditions of the Andes. We conduct a comparative analysis of cultural perceptions of ‘dark constellations’ in the Milky Way, examining common cultural themes and meanings at the crossroads of Indigenous Knowledge and Western science with applications to topics ranging from Indigenous Studies to psychology.Fil: Gullberg, Steven R.. Oklahoma State University; Estados UnidosFil: Hamacher, Duane. University of Melbourne; AustraliaFil: Lopez, Alejandro Martin. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Instituto de Ciencias Antropológicas. Sección de Etnología y Etnografía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Mejuto, Javier. Universidad Nacional Autónoma de Honduras; HondurasFil: Munro, Andrew M.. University of Oklahoma; Estados UnidosFil: Orchiston, Wayne. University of Southern Queensland; Australia. National Astronomical Research Institute of Thailand; Tailandi
Changes in the Second Ventilatory Threshold Following Individualised versus Standardised Exercise Prescription among Physically Inactive Adults: A Randomised Trial
The second ventilatory threshold (VT2) is established as an important indicator of exercise intensity tolerance. A higher VT2 allows for greater duration of higher intensity exercise participation and subsequently greater reductions in cardiovascular disease (CVD) risk. This study aimed to compare the efficacy of standardised and individualised exercise prescription on VT2 among physically inactive adults. Forty-nine physically inactive male and female participants (48.6 ± 11.5 years) were recruited and randomised into a 12-week standardised (n = 25) or individualised (n = 24) exercise prescription intervention. The exercise intensity for the standardised and individualised groups was prescribed as a percentage of heart rate reserve (HRR) or relative to the first ventilatory threshold (VT1) and VT2, respectively. Participants were required to complete a maximal graded exercise test at pre-and post-intervention to determine VT1 and VT2. Participants were categorised as responders to the intervention if an absolute VT2 change of at least 1.9% was attained. Thirty-eight participants were included in the analysis. A significant difference in VT2 change was found between individualised (pre vs. post: 70.6% vs. 78.7% maximum oxygen uptake (VO2max)) and standardised (pre vs. post: 72.5% vs. 72.3% VO2max) exercise groups. Individualised exercise prescription was significantly more efficacious (p = 0.04) in eliciting a positive response in VT2 (15/19, 79%) when compared to the standardised exercise group (9/19, 47%). Individualised exercise prescription appears to be more efficacious than standardised exercise prescription in eliciting a positive VT2 change among physically inactive adults. Increasing VT2 allows for greater tolerance to higher exercise intensities and therefore greater cardiovascular health outcomes
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