Tensor networks and the numerical renormalization group

The full-density-matrix numerical renormalization group (NRG) has evolved as a systematic and transparent setting for the cal- culation of thermodynamical quantities at arbitrary temperatures within the NRG framework. It directly evaluates the relevant Lehmann representations based on the complete basis sets intro- duced by Anders and Schiller (2005). In addition, specific attention is given to the possible feedback from low energy physics to high energies by the explicit and careful construction of the full thermal density matrix, naturally generated over a distribution of energy shells. Specific examples are given in terms of spectral functions (fdmNRG), time-dependent NRG (tdmNRG), Fermi-Golden rule calculations (fgrNRG), as well as the calculation of plain thermodynamic expectation values. Furthermore, based on the very fact that, by its iterative nature, the NRG eigenstates are naturally described in terms of matrix product states, the language of tensor networks has proven enormously convenient in the description of the underlying algorithmic procedures. This paper therefore also provides a detailed introduction and discussion of the prototypical NRG calculations in terms of their corresponding tensor networks.Comment: 20 pages, 11 figures (adapted from habilitation thesis

GAWPS: A MRST-based module for wellbore profiling and graphical analysis of flow units

Several graphical methods have been developed to understand the stratigraphy observed in wells and assist experts in estimating rock quality, defining limits for barriers, baffles, and speed zones, and in particular, delineating hydraulic flow units. At present, there exists no computational tool that bundles the main graphical methods used for defining flow units. This paper introduces an add-on module to the MATLAB Reservoir Simulation Toolbox that contains computational routines to carry out such graphical analyses, both qualitatively and quantitatively. We also describe a new secondary method defined as the derivative of the stratigraphic modified Lorenz plot, which we use to classify depth ranges within the reservoir into barriers, strong baffles, weak baffles, and normal units, based on flow unit speed over those depths. We demonstrate the capabilities of the “Graphical Analysis for Well Placement Strategy” module by applying it to several case studies of both real and synthetic reservoirs.Cited as: Oliveira, G. P., Rodrigues, T. N. E., Lie, K.-A. GAWPS: A MRST-based module for wellbore profiling and graphical analysis of flow units. Advances in Geo-Energy Research, 2021, 6(1): 38-53. https://doi.org/10.46690/ager.2022.01.0

Shedding Light on the Enigmatic TcO2 ⋅ xH2O Structure with Density Functional Theory and EXAFS Spectroscopy

The β-emitting 99Tc isotope is a high-yield fission product in 235U and 239Pu nuclear reactors, raising special concern in nuclear waste management due to its long half-life and the high mobility of pertechnetate (TcO4−). Under the conditions of deep nuclear waste repositories, Tc is retained through biotic and abiotic reduction of TcO4− to compounds like amorphous TcO2 ⋅ xH2O precipitates. It is generally accepted that these precipitates have linear (Tc(μ-O)2(H2O)2)n chains, with trans H2O. Although corresponding Tc−Tc and Tc−O distances have been obtained from extended X-ray absorption fine structure (EXAFS) spectroscopy, this structure is largely based on analogy with other compounds. Here, we combine density-functional theory with EXAFS measurements of fresh and aged samples to show that, instead, TcO2 ⋅ xH2O forms zigzag chains that undergo a slow aging process whereby they combine to form longer chains and, later, a tridimensional structure that might lead to a new TcO2 polymorph

O processo de formação e institucionalização da estratégia no contexto governamental do estado de Santa Catarina

Dissertação (mestrado) - Universidade Federal de Santa Catarina, Centro Sócio-Econômico, Programa de Pós-Graduação em Administração, Florianópolis, 2016.O objetivo desta pesquisa foi analisar de que forma ocorre o processo de formação e de institucionalização da estratégia no contexto governamental do Estado de Santa Catarina. Para tanto, procurou-se consubstanciá-la em um marco teórico composto por um tripé formado (i) pela estratégia e seu processo de formação, com foco no modelo integrador proposto por Andersen (2013); (ii) pela teoria institucional e seus processos e estágios e; (iii) pelo papel do Estado e a gestão pública. Estes campos de estudo das teorias organizacionais possuem diversos pontos de imbricamento, principalmente quando observados a partir das contribuições de teóricos como Barnard (1938) ? incerteza como essência do ato de administrar ? e Simon (1957) ? racionalidade limitada do decisor, e que permitiram que as pesquisas dos fenômenos organizacionais adotassem outras perspectivas. Para responder à questão de pesquisa, optou-se pela abordagem metodológica qualitativa, por meio de estudo de caso único. As técnicas para coletas de dados passaram pelo uso de observação participante, entrevistas semiestruturadas e análise documental. Com isso, buscou-se estabelecer as bases que possibilitaram a aplicação de técnicas de análise de dados como o pattern matching (TROCHIM, 1989). A pesquisa permitiu entender, empiricamente, como o fenômeno da formação da estratégia toma forma e se institucionaliza em uma organização pública. Além disso, constatou-se a presença de indícios de que, apesar de uma aparente tendência ao processo deliberado, existem vetores estratégicos com caráter emergente, resultando num processo de formação de estratégia predominantemente integrador e que este se encontra semi-institucionalizado na organização.Abstract : The goal of this research was to analyse how the strategy formation and institutionalization processes happen in the government context of the State of Santa Catarina. Therefore, it was aimed to substantiating it in a theoretical framework that consists on a tripod formed by: (i) the strategy and its formation process, focused on the integrative model proposed by Andersen (2013); (ii) institutional theory and its processes and stages and; (iii) the role of the State and the public management. These fields of study related to the organizational theories have several points of connection, mostly when observed from the theoretical contributions of researchers like Barnard (1938) ? uncertainty as an essence of the managerial action ? and Simon (1957) ? limited rationality of the decision maker, and thus allowed research regarding the organizational phenomena to adopt different perspectives. In order to answer the research question, it was decided to use the qualitative methodological approach, through a single case study. Techniques for data collection go through the use of participant observation, semi structured interviews and document analysis. Therewith, it was expected to stablish the basis that enable the application of data analysis techniques such as pattern matching (TROCHIM, 1989). This research allowed us to understand, empirically, how the strategy formation process takes place and becomes institutionalized in a public organization. Besides, despite an apparent bias to a more deliberate process, evidences show the existence of emergent vectors, resulting in a predominantly integrative strategy formation process that is semi institutionalized in the organization

Non-collinear Hox gene expression in bivalves and the evolution of morphological novelties in mollusks

Hox genes are key developmental regulators that are involved in establishing morphological features during animal ontogeny. They are commonly expressed along the anterior--posterior axis in a staggered, or collinear, fashion. In mollusks, the repertoire of body plans is widely diverse and current data suggest their involvement during development of landmark morphological traits in Conchifera, one of the two major lineages that comprises those taxa that originated from a uni-shelled ancestor (Monoplacophora, Gastropoda, Cephalopoda, Scaphopoda, Bivalvia). For most clades, and bivalves in particular, data on Hox gene expression throughout ontogeny are scarce. We thus investigated Hox expression during development of the quagga mussel, Dreissena rostriformis, to elucidate to which degree they might contribute to specific phenotypic traits as in other conchiferans. The Hox/ParaHox complement of Mollusca typically comprises 14 genes, 13 of which are present in bivalve genomes including Dreissena. We describe here expression of 9 Hox genes and the ParaHox gene Xlox during Dreissena development. Hox expression in Dreissena is first detected in the gastrula stage with widely overlapping expression domains of most genes. In the trochophore stage, Hox gene expression shifts towards more compact, largely mesodermal domains. Only few of these domains can be assigned to specific developing morphological structures such as Hox1 in the shell field and Xlox in the hindgut. We did not find traces of spatial or temporal staggered expression of Hox genes in Dreissena. Our data support the notion that Hox gene expression has been coopted independently, and to varying degrees, into lineage-specific structures in the respective conchiferan clades. The non-collinear mode of Hox expression in Dreissena might be a result of the low degree of body plan regionalization along the bivalve anterior--posterior axis as exemplified by the lack of key morphological traits such as a distinct head, cephalic tentacles, radula apparatus, and a simplified central nervous system

Leaf-associated macroinvertebrate assemblage and leaf litter breakdown in headwater streams depend on local riparian vegetation

Headwater streams harbor diverse macroinvertebrate communities and are hotspots for leaf litter breakdown. The process of leaf litter breakdown mediated by macroinvertebrates forms an important link between terrestrial and aquatic ecosystems. Yet, how the vegetation type in the local riparian zone influences leaf-associated macroinvertebrate assemblages and leaf litter breakdown rates is still not resolved. We investigated how leaf-associated macroinvertebrate assemblages and leaf litter fragmentation rates differ between forested and non-forested sites using experimental leaf litter bags in sixteen sites paired across eight headwater streams in Switzerland. Our results show that sensitive taxa of the invertebrate orders Ephemeroptera, Plecoptera and Trichoptera (EPT) and the functional group of shredders were strongly associated with forested sites with overall higher values of abundance, diversity, and biomass of EPTs in forested compared to non-forested sites. However, the importance of riparian vegetation differed between study regions, especially for shredders. Fragmentation rates, which are primarily the result of macroinvertebrate shredding, were on average three times higher in forested compared to non-forested sites. Our results demonstrate that not only the composition of the aquatic fauna but also the functioning of an essential ecosystem process depend on the vegetation type in the local riparian zone