Statistical mixing and aggregation in Feller diffusion

We consider Feller mean-reverting square-root diffusion, which has been applied to model a wide variety of processes with linearly state-dependent diffusion, such as stochastic volatility and interest rates in finance, and neuronal and populations dynamics in natural sciences. We focus on the statistical mixing (or superstatistical) process in which the parameter related to the mean value can fluctuate - a plausible mechanism for the emergence of heavy-tailed distributions. We obtain analytical results for the associated probability density function (both stationary and time dependent), its correlation structure and aggregation properties. Our results are applied to explain the statistics of stock traded volume at different aggregation scales.Comment: 16 pages, 3 figures. To be published in Journal of Statistical Mechanics: Theory and Experimen

A probabilistic approach to emission-line galaxy classification

We invoke a Gaussian mixture model (GMM) to jointly analyse two traditional emission-line classification schemes of galaxy ionization sources: the Baldwin-Phillips-Terlevich (BPT) and $\rm W_{H\alpha}$ vs. [NII]/H$\alpha$ (WHAN) diagrams, using spectroscopic data from the Sloan Digital Sky Survey Data Release 7 and SEAGal/STARLIGHT datasets. We apply a GMM to empirically define classes of galaxies in a three-dimensional space spanned by the $\log$ [OIII]/H$\beta$, $\log$ [NII]/H$\alpha$, and $\log$ EW(H${\alpha}$), optical parameters. The best-fit GMM based on several statistical criteria suggests a solution around four Gaussian components (GCs), which are capable to explain up to 97 per cent of the data variance. Using elements of information theory, we compare each GC to their respective astronomical counterpart. GC1 and GC4 are associated with star-forming galaxies, suggesting the need to define a new starburst subgroup. GC2 is associated with BPT's Active Galaxy Nuclei (AGN) class and WHAN's weak AGN class. GC3 is associated with BPT's composite class and WHAN's strong AGN class. Conversely, there is no statistical evidence -- based on four GCs -- for the existence of a Seyfert/LINER dichotomy in our sample. Notwithstanding, the inclusion of an additional GC5 unravels it. The GC5 appears associated to the LINER and Passive galaxies on the BPT and WHAN diagrams respectively. Subtleties aside, we demonstrate the potential of our methodology to recover/unravel different objects inside the wilderness of astronomical datasets, without lacking the ability to convey physically interpretable results. The probabilistic classifications from the GMM analysis are publicly available within the COINtoolbox (https://cointoolbox.github.io/GMM\_Catalogue/).Comment: Accepted for publication in MNRA

Bipolar HII regions - Morphology and star formation in their vicinity - I - G319.88++00.79 and G010.32−-00.15

Our goal is to identify bipolar HII regions and to understand their morphology, their evolution, and the role they play in the formation of new generations of stars. We use the Spitzer and Herschel Hi-GAL surveys to identify bipolar HII regions. We search for their exciting star(s) and estimate their distances using near-IR data. Dense clumps are detected using Herschel-SPIRE data. MALT90 observations allow us to ascertain their association with the central HII region. We identify Class 0/I YSOs using their Spitzer and Herschel-PACS emissions. These methods will be applied to the entire sample of candidate bipolar HII regions. This paper focuses on two bipolar HII regions, one interesting in terms of its morphology, G319.88$+$00.79, and one in terms of its star formation, G010.32$-$00.15. Their exciting clusters are identified and their photometric distances estimated to be 2.6 kpc and 1.75 kpc, respectively. We suggest that these regions formed in dense and flat structures that contain filaments. They have a central ionized region and ionized lobes perpendicular to the parental cloud. The remains of the parental cloud appear as dense (more than 10^4 per cm^3) and cold (14-17 K) condensations. The dust in the PDR is warm (19-25 K). Dense massive clumps are present around the central ionized region. G010.32-00.14 is especially remarkable because five clumps of several hundred solar masses surround the central HII region; their peak column density is a few 10^23 per cm^2, and the mean density in their central regions reaches several 10^5 per cm^3. Four of them contain at least one massive YSO; these clumps also contain extended green objects and Class II methanol masers. This morphology suggests that the formation of a second generation of massive stars has been triggered by the central bipolar HII region. It occurs in the compressed material of the parental cloud.Comment: 32 pages, 28 figures, to be published in A&

Controle integrado da vassoura-de-bruxa aumenta produção de cupuaçuzeiros.

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Genome-wide significant schizophrenia risk variation on chromosome 10q24 is associated with altered cis-regulation of BORCS7, AS3MT, and NT5C2 in the human brain

Chromosome 10q24.32-q24.33 is one of the most robustly supported risk loci to emerge from genome-wide association studies (GWAS) of schizophrenia. However, extensive linkage disequilibrium makes it difficult to distinguish the actual susceptibility gene(s) at the locus, limiting its value for improving biological understanding of the condition. In the absence of coding changes that can account for the association, risk is likely conferred by altered regulation of one or more genes in the region. We, therefore, used highly sensitive measures of allele-specific expression to assess cis-regulatory effects associated with the two best-supported schizophrenia risk variants (SNP rs11191419 and indel ch10_104957618_I/rs202213518) on the primary positional candidates BORCS7, AS3MT, CNNM2, and NT5C2 in the human brain. Heterozygosity at rs11191419 was associated with increased allelic expression of BORCS7 and AS3MT in the fetal and adult brain, and with reduced allelic expression of NT5C2 in the adult brain. Heterozygosity at ch10_104957618_I was associated with reduced allelic expression of NT5C2 in both the fetal and adult brain. Comparisons between cDNA ratios in heterozygotes and homozygotes for the risk alleles indicated that cis-effects on NT5C2 expression in the adult dorsolateral prefrontal cortex could be largely accounted for by genotype at these two risk variants. While not excluding effects on other genes in the region, this study implicates altered neural expression of BORCS7, AS3MT, and NT5C2 in susceptibility to schizophrenia arising from genetic variation at the chromosome 10q24 locus

Construções sustentáveis na Província do Huambo – Angola. Características dos geomateriais utilizados

Na actualidade, as questões ambientais são discutidas com o objectivo fundamental de alertar as sociedades contemporâneas para a necessidade de se encontrarem soluções sustentáveis. Os problemas de sustentabilidade, nomeadamente, as alterações climáticas, são questões pertinentes no mundo de hoje. A sustentabilidade das construções em terra crua tem demonstrado a sua importância ao longo da história, reaparecendo em perfeita sintonia com a ambição de se reduzir os materiais fabricados com o recurso aos combustíveis fósseis e os consequentes impactos negativos para o ambiente. Por este motivo, a construção em terra continua a ser objecto de estudos, investigação e inovação técnica e tecnológica sobre as suas potencialidades e optimização. Na região do Huambo, Planalto Central de Angola, a maioria das habitações de famílias de baixa renda, são construídas em terra crua. A técnica mais usada é a do adobe, não obstante, a existência de algumas construções em pau-a-pique e taipa. Devido à falta de conhecimento das propriedades dos geomateriais utilizados e das técnicas que permitem a sua estabilização e conservação, aquelas estruturas são vulneráveis e apresentam degradação precoce, agravadas por um clima predominantemente subtropical quente e húmido. Não obstante os esforços que têm sido desenvolvidos no país, a falta de habitação digna, ainda constitui o maior drama pós-guerra para as populações mais carenciadas. Será desejável, por isso, encontrar soluções para melhorar a durabilidade e a resistência dos adobes na região em estudo, o que passa, necessariamente, pelo estudo das características geotécnicas dos materiais usados no seu fabrico e nos métodos construtivos. Neste trabalho, pretende-se avaliar as propriedades mineralógicas e físicas dos solos, bem como, as características mecânicas dos adobes construídos com os mesmos, utilizando as técnicas locais. Para o efeito, recorreu-se à realização de ensaios in-situ e laboratoriais para determinar as características mineralógicas (DRX), físicas (granulometria, peso específico, textura, consistência, expansibilidade) e mecânicas (resistência à tracção por flexão) dos adobes, a durabilidade pelo método de Geelong e o ensaio de avaliação do ciclo húmido/seco, aplicando as normas neozelandesas (4298:1998 e 4297:1998). Os resultados obtidos permitirão identificar e caraterizar os geomateriais e os métodos mais utilizados na construção em terra crua na Província de Huambo, contribuindo para o conhecimento e melhoramento destas soluções sustentáveis, com forte implantação nesta região. Este estudo contribuirá ainda para a definição da estratégia a seguir no âmbito de um projecto de investigação mais abrangente, que visa a proposta de soluções construtivas com melhores características de desempenho, conforto, segurança, durabilidade e sustentabilidade ambiental, económica e social