Precision cosmology with redshift-space bispectrum: a perturbation theory based model at one-loop order

The large-scale matter distribution in the late-time Universe exhibits gravity-induced non-Gaussianity, and the bispectrum, three-point cumulant is expected to contain significant cosmological information. In particular, the measurement of the bispectrum helps to tighten the constraints on dark energy and modified gravity through the redshift-space distortions (RSD). In this paper, extending the work by Taruya, Nishimichi & Saito (2010, Phys.Rev.D 82, 063522), we present a perturbation theory (PT) based model of redshift-space matter bispectrum that can keep the non-perturbative damping effect under control. Characterizing this non-perturbative damping by a univariate function with single free parameter, the PT model of the redshift-space bispectrum is tested against a large set of cosmological $N$-body simulations, finding that the predicted monopole and quadrupole moments are in a good agreement with simulations at the scales of baryon acoustic oscillations (well beyond the range of agreement of standard PT). The validity of the univariate ansatz of the damping effect is also examined, and with the PT calculation at next-to-leading order, the fitted values of the free parameter is shown to consistently match those obtained from the PT model of power spectrum by Taruya, Nishimichi & Saito (2010).Comment: 21 pages, 13 figure

Computation of the Halo Mass Function Using Physical Collapse Parameters: Application to Non-Standard Cosmologies

In this article we compare the halo mass function predicted by the excursion set theory with a drifting diffusive barrier against the results of N-body simulations for several cosmological models. This includes the standard LCDM case for a large range of halo masses, models with different types of primordial non-Gaussianity, and the Ratra-Peebles quintessence model of Dark Energy. We show that in all those cosmological scenarios, the abundance of dark matter halos can be described by a drifting diffusive barrier, where the two parameters describing the barrier have physical content. In the case of the Gaussian LCDM, the statistics are precise enough to actually predict those parameters at different redshifts from the initial conditions. Furthermore, we found that the stochasticity in the barrier is nonnegligible making the simple deterministic spherical collapse model a bad approximation even at very high halo masses. We also show that using the standard excursion set approach with a barrier inspired by peak patches leads to inconsistent predictions of the halo mass function.Comment: 25 pages, 12 figure

Probing dark energy models with extreme pairwise velocities of galaxy clusters from the DEUS-FUR simulations

Observations of colliding galaxy clusters with high relative velocity probe the tail of the halo pairwise velocity distribution with the potential of providing a powerful test of cosmology. As an example it has been argued that the discovery of the Bullet Cluster challenges standard $\Lambda$CDM model predictions. Halo catalogs from N-body simulations have been used to estimate the probability of Bullet-like clusters. However, due to simulation volume effects previous studies had to rely on a Gaussian extrapolation of the pairwise velocity distribution to high velocities. Here, we perform a detail analysis using the halo catalogs from the Dark Energy Universe Simulation Full Universe Runs (DEUS-FUR), which enables us to resolve the high-velocity tail of the distribution and study its dependence on the halo mass definition, redshift and cosmology. Building upon these results we estimate the probability of Bullet-like systems in the framework of Extreme Value Statistics. We show that the tail of extreme pairwise velocities significantly deviates from that of a Gaussian, moreover it carries an imprint of the underlying cosmology. We find the Bullet Cluster probability to be two orders of magnitude larger than previous estimates, thus easing the tension with the $\Lambda$CDM model. Finally, the comparison of the inferred probabilities for the different DEUS-FUR cosmologies suggests that observations of extreme interacting clusters can provide constraints on dark energy models complementary to standard cosmological tests.Comment: Submitted to MNRAS, 15 pages, 12 figures, 3 table

Self-consistency of the Excursion Set Approach

The excursion set approach provides a framework for predicting how the abundance of dark matter halos depends on the initial conditions. A key ingredient of this formalism comes from the physics of halo formation: the specification of a critical overdensity threshold (barrier) which protohalos must exceed if they are to form bound virialized halos at a later time. Another ingredient is statistical, as it requires the specification of the appropriate statistical ensemble over which to average when making predictions. The excursion set approach explicitly averages over all initial positions, thus implicitly assuming that the appropriate ensemble is that associated with randomly chosen positions in space, rather than special positions such as peaks of the initial density field. Since halos are known to collapse around special positions, it is not clear that the physical and statistical assumptions which underlie the excursion set approach are self-consistent. We argue that they are at least for low mass halos, and illustrate by comparing our excursion set predictions with numerical data from the DEUS simulations.Comment: 5 pages, 2 figure

Modelling and experimental validation of tribocharging for space resource utilisation (SRU)

Space Resource Utilisation (SRU) technology will enable further exploration and habitation of space by humankind. For example, oxygen produced \textit{in situ} can be used as the oxidiser in rocket propellant, or for life support systems. The production of oxygen on the Moon can be achieved through the thermo-chemical reduction of the lunar soil, also known as regolith. All reduction techniques require a consistent feedstock from this mix of fine mineral particles to produce oxygen reliably and consistently. The preparation of this feedstock, known as beneficiation, is a critical intermediate stage of the SRU flowsheet, however it has received little research attention relative to the preceding excavation, and the subsequent oxygen production stages. Triboelectric charging and free-fall separation are attractive technologies for mineral beneficiation as they offers low mass, low power, and low mechanical complexity compared to other approaches. Tribocharging is a process by which particles (conductors, semi-conductors, and insulators) acquire charge through frictional rubbing and subsequent separation. Previous experimental studies have tested different designs of tribocharging apparatuses for terrestrial and space applications, however charge transfer modelling methods have not been employed to optimise design parameters. Furthermore, whilst modelling of the triboelectrification process has been presented in the literature using the discrete element method (DEM), these models often depend on poorly quantified or ill-defined parameters, such as an effective work function for insulating materials. Previous studies have also been restricted to either 2D or 3D domains and have not considered the impact of this on the performance of the models. To address these knowledge and research gaps, the objectives of this thesis are as follows: \begin{enumerate} \item Develop a novel tribocharge modelling approach based on the discrete element method that de-emphasises the poorly-defined quantities found in the high-density limit approach that has been demonstrated previously; \item Determine the suitability of modelling tribocharging in 2D and 3D; \item Validate this novel tribocharge modelling method by comparing simulation outputs and experimental data; \item Present and validate a new DEM-based method for tribocharger design optimisation; and, \item Evaluate experimentally the impact of an optimised tribocharger design on the performance of an electrostatic separator using standard mineral processing criteria. \end{enumerate} A straightforward experimental method to quantify key tribocharging model parameters, namely the charge transfer limit, $\Gamma$, and the charging efficiency, $\kappa_c$, is presented herein. These parameters are then used in both 2D and 3D DEM charge transfer simulations (particle-particle and particle-wall interactions; single and multiple particles and contacts) to evaluate the suitability of faster 2D models. Both the 2D and 3D models were found to perform well against the experimental data for single-contact and single-particle, multi-contact systems, however 2D models failed to produce good agreement with multi-particle, multi-contact systems. A novel DEM-based approach for tribocharger design optimisation using particle-wall and particle-particle contact areas as proxies for charge transfer is demonstrated. This optimisation method is used to design an optimal tribocharger for use under terrestrial conditions. The novel tribocharge modelling approach was then applied to the optimised charger design. This design was then built and validated experimentally, with good agreement found between the model outputs and experimental data. The optimised terrestrial design was then employed to study the charging behaviour of pure silica and ilmenite, as well as binary mixtures of silica and ilmenite, and samples of lunar regolith simulant JSC-1. Ilmenite was used because it is a target mineral for oxygen production from the lunar regolith, and silica was used because of its position in the triboelectric series relative to ilmenite. The optimised tribocharger design affected significantly the movement of pure ilmenite in the electrostatic field, despite a negligible change in bulk charge. Experimental results from the binary mixtures indicate that ilmenite recovery is independent of initial ilmenite concentration and can be predicted from the mass distribution of pure ilmenite samples. For JSC-1, the tribocharger was found to increase the density of the material in certain collectors. This thesis presents new modelling approaches for both tribocharging and tribocharger design optimisation. These techniques will facilitate ultimately the development of beneficiation technologies for SRU. The use of these modelling methods should increase confidence in the performance of tribocharger designs proposed for future SRU missions to the Moon.Open Acces

Imprints of Dark Energy on Cosmic Structure Formation: III. Sparsity of Dark Matter Halo Profiles

We study the imprint of Dark Energy on the density profile of Dark Matter halos using a set of high-resolution large volume cosmological N-body simulations from the Dark Energy Universe Simulation Series (DEUSS). We first focus on the analysis of the goodness-of-fit of the Navarro-Frenk-White (NFW) profile which we find to vary with halo mass and redshift. We also find that the fraction of halos ill-fitted by NFW varies with cosmology, thus indicating that the mass assembly of halos with perturbed density profiles carries a characteristic signature of Dark Energy. To access this information independently of any parametric profile, we introduce a new observable quantity: the halo sparsity $s_\Delta$. This is defined as the mass ratio $M_{200}/M_\Delta$, i.e. the ratio of mass inside a sphere of radius $r_{200}$ to that contained within a radius $r_\Delta$, enclosing 200 and $\Delta$ times the mean matter density respectively. We find the average sparsity to be nearly independent of the total halo mass, while its value can be inferred to better than a few percent from the ratio of the integrated halo mass functions at overdensities $\Delta$ and 200 respectively. This provides a consistency relation that can validate observational measurements of the halo sparsity. Most importantly, the sparsity significantly varies with the underlying Dark Energy model, thus providing an alternative cosmological probe.Comment: 12 pages, 16 figures. accepted by MNRA

Uma nova proposta para evitar sintering de nanopartículas em catálise

Sintering is a process whereby nanoparticles increase their size and reduce their number under high temperatures. Since catalytic activity depends on the number of active sites, and those lie on the surface of nanoparticles, the most detrimental consequence of sintering for catalysis is the loss of surface area, which reduces the number of active sites. Sintering is the main cause of catalyst deactivation and the current prevention strategies demand specific synthesis methods, modification of the chemical properties of the nanoparticles or nanostructuring of supports. A new proposal for the prevention of sintering of nanoparticles, easily reproducible, is presented and applied to Cu nanoparticles supported on MgO. A combination of XRD, in situ EXAFS and TEM shows the prevention of sintering of Cu nanoparticles under H2 atmosphere at 300◦C. In situ timeresolved XANES and XPS techniques were used to investigate the possibility of catalyst poisoning due to the strategy employed. The results show no evidence of poisoned species. Furthermore, by modelling the system with Monte Carlo simulations, it was possible to reproduce sintering prevention and to propose a possible mechanism whereby the method operates, besides getting a better picture of the pertinent parameters value range that allows sintering prevention.Sintering e um processo pelo qual nanopartíıculas aumentam o seu tamanho e reduzem seu numero sob altas temperaturas. Como a atividade catalítica depende do número de síıtios ativos, e estes se encontram na superfície das nanopartículas, a consequência mais prejudicial do sintering para catalise é a perda de área superficial, que reduz o número de sítios ativos. Sintering e a principal causa de desativacão de catalisadores e as estratégias de prevenção atuais demandam métodos de síntese específicas, modificação das propriedades quíımicas das nanopartíıculas ou nanoestruturação dos suportes. Uma nova proposta para a prevenção de sintering de nanopartículas, facilmente reproduzível, e apresentada e aplicada a nanopartículas de Cu suportadas em MgO. Uma combinação de medidas de XRD, EXAFS in situ e TEM demonstra a prevenção de sintering das nanopartículas de Cu sob atmosfera de H2 a 300◦C. As técnicas de XANES in situ resolvido no tempo e XPS foram utilizadas para explorar a possibilidade de envenenamento do catalisador devido a estratégia empregada. Os resultados indicam que não há qualquer composto envenenado. Ademais, modelando o sistema utilizando simulações de Monte Carlo foi possível reproduzir a prevenção de sintering e propôr um mecanismo pelo qual o método opera, além de se obter uma figura mais ampla do intervalo de valores de parâmetros que permitem a prevenção de sintering

Grãos de mostarda como fonte de compostos com propriedades antioxidantes : um estudo baseado nos processos de germinação, extração e identificação

Orientador: Ruann Janser Soares de CastroDissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia de AlimentosResumo: Germinação é um processo econômico e natural que oferece novas oportunidades para a melhoria da qualidade nutricional e do potencial biológico de grãos. As transformações bioquímicas que acontecem durante esse processo em mostarda ainda não foram elucidadas pela literatura, mas sabe-se que as condições de germinação influenciam diretamente a composição final dos germinados. Os grãos de mostarda apresentam grande potencial bioativo, e, além de baratos, são mundialmente conhecidos e consumidos. Desta forma, o presente projeto teve como objetivos avaliar a influência dos parâmetros (luz, temperatura e tempo) na germinação de sementes de mostarda; determinar o solvente mais adequado (água, acetona e metanol) para obtenção de extratos com maior teor de compostos fenólicos e atividade antioxidante e avaliar as propriedades antioxidantes dos extratos obtidos utilizando os métodos FRAP, ORAC, ABTS e DPPH, além da determinação do teor de compostos fenólicos totais (TPC), flavonoides totais e taninos condensados, das frações solúveis e insolúveis de grãos de mostarda germinados e não germinados. Adicionalmente, foi realizada a identificação dos compostos fenólicos por cromatografia líquida de alta eficiência nos extratos de grãos de mostarda não germinados. As análises foram realizadas utilizando-se grãos de mostarda branca (Sinapsis alba) e preta (Brassica nigra). As condições de germinação que permitiram a produção de extratos com maior conteúdo de compostos fenólicos e melhores propriedades antioxidantes para mostarda branca foram: 72 h de germinação, temperatura de incubação de 25°C no escuro. Para as amostras de mostarda preta, a condição definida como mais adequada foi: 48 h de germinação a 25°C, com períodos alternados de luz e escuro. A combinação de solventes selecionada para a extração de compostos fenólicos com propriedades antioxidantes para ambas as variedades foi acetona e água (50% v:v), condição em que os resultados foram no mínimo 20 vezes maiores quando comparados com acetona pura. Em relação ao estudo comparativo entre os extratos de mostarda não germinada com a germinada nas condições escolhidas, observou-se melhoria nas propriedades antioxidantes dos grãos. As propriedades antioxidantes avaliadas pelos métodos FRAP, DPPH, ABTS e ORAC apresentaram aumento de 68%, 43%, 66% e 45%, respectivamente, para a fração solúvel de mostarda branca, e 29%, 3%, 160% e 42%, respectivamente, para a fração solúvel de mostarda preta após a germinação. As transformações entre a fração solúvel e insolúvel foram perceptíveis durante o processo. Enquanto a atividade antioxidante da fração solúvel e insolúvel da mostarda branca aumentou durante o processo, para a mostarda preta, o comportamento foi inverso: a 9 atividade antioxidante para fração solúvel aumentou e para a insolúvel diminuiu. Este contexto exemplifica a complexidade e as peculiaridades do processo germinativo, visto que as transformações que nele ocorrerem podem alterar significativamente o poder antioxidante dos extratos obtidos. A priori, apenas o ácido sinápico foi identificado em ambas as variedades de mostarda não germinadas. A complexidade do processo germinativo em mostarda ainda não foi totalmente elucidada, mas o presente trabalho mostrou algumas justificativas para as mudanças positivas encontradas. Além disso, diante dos resultados obtidos podemos concluir que o processo de germinação se apresenta como uma alternativa de consumo para os grãos de mostarda, que são, até então, largamente consumidos na forma de molhosAbstract: Germination is an economic and natural process that offers new opportunities to improve nutritional quality and biological potential of grains. The biochemical transformations that happen during this process in mustard grains were not elucidated by literature yet, but it is known that germination conditions influence directly the final composition of sprouts. Mustard grains present a bioactive potential, and besides being cheap, are consumed and known worldwide. Thus, the aim of this project was to evaluate the influence of parameters such as light, temperature and time, on germination of mustard seeds; determinate the most adequate solvent (water, acetone and methanol) to obtain extracts with the maximum of phenolic compounds and antioxidant activity; and evaluate the antioxidant activity of the extracts by FRAP, ORAC, ABTS and DPPH, besides the determination of total phenolic compounds (TPC), flavonoids and total condensed tannins of soluble and insoluble fractions of non-germinated and germinated mustard grains. Additionally, it was made the identification of phenolic compounds by high performance liquid chromatography of non-germinated mustard grains. All analysis were made with white (Sinapsis alba) and black (Brassica nigra) mustard grains. Germination conditions that allowed the production of extracts with higher content of phenolic compounds for white mustard were: 72h of germination at 25°C at dark and for black mustard 48h at 25°C with altered periods of light and dark. The combination of solvents selected for extraction of phenolic compounds with antioxidant activity as acetone and water (50% v/v), condition with results at least 20-folds higher when compared with pure acetone. Regarding the comparison between non-germinated and germinated mustard in the chosen conditions, it was observed an improvement of antioxidant properties of the grain. The antioxidant properties evaluated by FRAP, DPPH, ABTS and ORAC methods showed an increase of 68%, 43%, 66% and 45%, respectively, for soluble fraction of white mustard and 29%, 3%, 160% and 42%, respectively, for soluble fraction of black mustard. The transformation of bound and soluble fraction was noted during the process. While antioxidant activity of soluble and bound fraction of white mustard increased during the process, for black mustard this behavior was inverse: the antioxidant activity in soluble fraction increased and insoluble fraction decreased. This context exemplifies the complexity and peculiarity of germinative process, since transformations can change significantly antioxidant power of the extracts. Initially, only sinapic acid was found in both mustard species without germination. The complexity of germinative process in mustard was not elucidate yet, but the present word shows some justifications of the positive changes observed. Besides that, we can conclude that germination process is an alternative of consumption of mustard grains, that are until now, largely consumed as saucesMestradoCiência de AlimentosMestra em Ciência de Alimentos134000/2017-0CNP

Toward the utilisation of resources in space: knowledge gaps, open questions, and priorities

There are many open science questions in space resource utilisation due to the novelty and relative immaturity of the field. While many potential technologies have been proposed to produce usable resources in space, high confidence, large-scale design is limited by gaps in the knowledge of the local environmental conditions, geology, mineralogy, and regolith characteristics, as well as specific science questions intrinsic to each process. Further, the engineering constraints (e.g. energy, throughput, efficiency etc.) must be incorporated into the design. This work aims to summarise briefly recent activities in the field of space resource utilisation, as well as to identify key knowledge gaps, and to present open science questions. Finally, future exploration priorities to enable the use of space resources are highlighted