Quantum walks on two-dimensional grids with multiple marked locations

The running time of a quantum walk search algorithm depends on both the structure of the search space (graph) and the configuration of marked locations. While the first dependence have been studied in a number of papers, the second dependence remains mostly unstudied. We study search by quantum walks on two-dimensional grid using the algorithm of Ambainis, Kempe and Rivosh [AKR05]. The original paper analyses one and two marked location cases only. We move beyond two marked locations and study the behaviour of the algorithm for an arbitrary configuration of marked locations. In this paper we prove two results showing the importance of how the marked locations are arranged. First, we present two placements of $k$ marked locations for which the number of steps of the algorithm differs by $\Omega(\sqrt{k})$ factor. Second, we present two configurations of $k$ and $\sqrt{k}$ marked locations having the same number of steps and probability to find a marked location

IN-SYNC. VIII. Primordial Disk Frequencies in NGC 1333, IC 348, and the Orion A Molecular Cloud

In this paper, we address two issues related to primordial disk evolution in three clusters (NGC 1333, IC 348, and Orion A) observed by the INfrared Spectra of Young Nebulous Clusters (IN-SYNC) project. First, in each cluster, averaged over the spread of age, we investigate how disk lifetime is dependent on stellar mass. The general relation in IC 348 and Orion A is that primordial disks around intermediate mass stars (2--5$M_{\odot}$) evolve faster than those around loss mass stars (0.1--1$M_{\odot}$), which is consistent with previous results. However, considering only low mass stars, we do not find a significant dependence of disk frequency on stellar mass. These results can help to better constrain theories on gas giant planet formation timescales. Secondly, in the Orion A molecular cloud, in the mass range of 0.35--0.7$M_{\odot}$, we provide the most robust evidence to date for disk evolution within a single cluster exhibiting modest age spread. By using surface gravity as an age indicator and employing 4.5 $\mu m$ excess as a primordial disk diagnostic, we observe a trend of decreasing disk frequency for older stars. The detection of intra-cluster disk evolution in NGC 1333 and IC 348 is tentative, since the slight decrease of disk frequency for older stars is a less than 1-$\sigma$ effect.Comment: 25 pages, 26 figures; submitted for publication (ApJ

Aqua­bis(o-vanillinato-κ2 O,O′)nickel(II)

The NiII atom in the title complex, aqua­bis(2-formyl-6-meth­oxy­phenolato-κ2 O,O′)nickel(II), [Ni(C8H7O3)2(H2O)], is five-coordinated by four O atoms from two o-vanillinate ligands and one water mol­ecule in a slightly distorted square-pyramidal geometry (τ = 0.06). In the crystal structure, the mol­ecules are linked into dimers by inter­molecular O—H⋯O hydrogen bonds

Construção de saberes com agricultores familiares no Nordeste paraense.

O objetivo do artigo é analisar o processo de construção de saberes decorrente de uma interação entre agricultores familiares, técnicos e pesquisadores visando à criação de peixes no Nordeste Paraense. Para isso, são discutidas as lógicas orientadoras das ações desses agricultores, bem como são analisados os elementos que favoreceram a construção de saberes e a socialização de novos conteúdos. O entendimento prévio sobre a noção de construção de conhecimento e de saberes orienta a análise

Projeto ver-o-peixe aspectos metodológicos.

Este estudo foi realizado no Nordeste Paraense, partindo de uma demanda real de agricultores familiares que tinham interesse em criar peixes, mas acumulavam várias experiências frustradas, tendo por principal limitação a falta de conhecimento técnico para conduzir a atividade. Neste contexto, para apoiar a piscicultura local, foi elaborado o projeto Ver-o-Peixe seguindo uma adaptação do método de propriedades de referência. O projeto apoiou a formação de uma rede de estabelecimentos familiares que tinham criações de peixes e esta foi acompanhada durante dois anos, sendo analisada com enfoque sistêmico. Este acompanhamento sistemático gerou uma série de referências técnicas e econômicas que foram apresentadas em reuniões de socialização abertas ao território do Nordeste Paraense e onde também haviam capacitações cujos temas foram sugeridos pelos próprios agricultores da rede. Embora esteja sendo usada uma metodologia concebida originalmente na França, sua adaptação às condições brasileiras, agregando outros elementos, é uma ação ainda inovadora, mesmo que já tenha sido adotada em outros projetos. Acreditamos que se trata de uma excelente ferramenta para se alcançar os objetivos propostos, principalmente por nela estarem contidos elementos de colaboração estreita com os agricultores e associações, de validação das tecnologias adaptadas à realidade local, econômicos e sociais dos sistemas, acompanhamento sistemático, socializações e envolvimento dos atores de assistência técnica em todas as etapas

Quantitative Evidence for an Intrinsic Age Spread in the Orion Nebula Cluster

Aims. We present a study of the distribution of stellar ages in the Orion Nebula Cluster (ONC) based on accurate HST photometry taken from the HST Treasury Program observations of the ONC utilizing the most recent estimate of the cluster's distance (Menten et al. 2007). We investigate the presence of an intrinsic age spread in the region and a possible trend of age with the spatial distribution. Methods. We estimate the extinction and accretion luminosity towards each source by performing synthetic photometry on an empirical calibration of atmospheric models (Da Rio et al. 2010) using the package Chorizos (Maiz-Apellaniz 2004). The position of the sources in the HR-diagram is compared with different theoretical isochrones to estimate the mean cluster age and age dispersion. Through Monte Carlo simulations we quantify the amount of intrinsic age spread in the region, taking into account uncertainties on the distance, spectral type, extinction, unresolved binaries, accretion and photometric variability. Results. According to Siess et al. (2000) evolutionary models the mean age of the Cluster is 2.2 Myr with a scatter of few Myrs. With Monte Carlo simulations we find that the observed age spread is inconsistent with a coeval stellar population, but is in agreement with a star formation activity between 1.5 and 3.5 Myrs. We also observe light evidence for a trend of ages with spatial distribution.Comment: 12 pages, 12 figures, Accepted for publication in Astronomy and Astrophysic

Molecular structure and the twist-bend nematic phase : the role of terminal chains

Peer reviewedPostprin