Structural connectivity based on diffusion Kurtosis imaging

Structural connectivity models based on Diffusion Tensor Imaging (DTI) are strongly affected by the technique’s inability to resolve crossing fibres, either intra- or inter-hemispherical connections. Several models have been proposed to address this issue, including an algorithm aiming to resolve crossing fibres which is based on Diffusion Kurtosis Imaging (DKI). This technique is clinically feasible, even when multi-band acquisitions are not available, and compatible with multi-shell acquisition schemes. DKI is an extension of DTI enabling the estimation of diffusion tensor and diffusion kurtosis metrics. In this study we compare the performance of DKI and DTI in performing structural brain connectivity. Six healthy subjects were recruited, aged between 25 and 35 (three females). The MRI experiments were performed using a 3T Siemens Trio with a 32-channel head coil. The scans included a T1-weighted sequence (1mm3), and a DWI with b-values 0, 1000 and 2000 s:mm2. For each b-value, 64 equally spaced gradient directions were sampled. For DTI fitting only images with b-value of 0 and 1000 s:mm2 were considered, whereas for the DKI fitting, the whole cohort of images were considered. To fit both DTI and DKI tensors, extract the metrics and perform tract reconstructions, the toolbox DKIu was used, and the structural connectivity analysis was accomplished using the MIBCA toolbox. Tractography results revealed, as expected, that DKI-based tractography models can resolve crossing fibres within the same voxel, which posed a limitation to the DTI-based tractography models. Structural connectivity analysis showed DKI-based networks’ ability to establish both more inter-hemisphere and intra-hemisphere connections, when compared to DTI-based networks. This may be a direct consequence of the inability to resolve crossing fibres when using the DTI model. The DKI model ability to resolve crossing fibres may provide increased sensitivity to both inter- and intra-hemispherical connections. DTI-based modularity connectograms show a distinct intra-hemispherical configuration, whereas DKI-based connectograms show an increased number of inter-hemispherical connections, with several clusters extending over both hemispheres. Global and local connectivity metrics were also studied, but yielded no conclusive results. This may be due to a lack of reproducibility of the metrics or of the small cohort of subjects considered. DKI seems to provide additional insights into structural brain connectivity by resolving crossing fibres, otherwise undetected by DTI

Avaliação do ruído em refeitórios escolares

Tendo em consideração que os estudantes passam cerca de um terço do dia em estabelecimentos escolares, as condições ambientais das escolas influenciam não só a saúde dos estudantes mas também a respetiva atitude e desempenho. A avaliação do ruído em refeitórios escolares foi realizada no âmbito de um projeto mais amplo, o projeto QUAMIS – Qualidade do ambiente interior em salas de aula. No presente artigo são apresentados resultados da caracterização acústica de seis refeitórios escolares, abrangendo os níveis pré-primário, 1.º e 2.º ciclo do ensino básico. A caracterização acústica inclui a medição do tempo de reverberação e dos níveis sonoros ocorridos durante os horários das refeições. Apenas metade dos refeitórios escolares ensaiados cumprem os valores limite do tempo de reverberação. Os níveis sonoros a que os alunos estão expostos nos refeitórios escolares são elevados. Verificou-se que na generalidade dos refeitórios avaliados os alunos durante o horário das refeições estão expostos a níveis sonoros contínuos equivalentes superiores a 80 dB(A). Verifica-se a necessidade de projetos acústicos de qualidade e da verificação in situ através da realização de ensaios acústicos para verificação do cumprimento do RRAE para futuros refeitórios escolares e da necessidade de avaliação acústica dos refeitórios em edifícios escolares existentes e da consequente implementação de medidas de correção que permitam melhorar a sua qualidade acústica

Cerithiidae, Litiopidae, Modulidae and Planaxidae (Gastropoda, Cerithioidea) collected by the Marion Dufresne MD55 expedition in southeastern Brazil

Several deep-water mollusks collected during the Marion Dufresne MD55 expedition off SE Brazil have been studied in recent papers. The present work focuses on eight species belonging to the cerithioidean families Cerithiidae, Litiopidae, Modulidae and Planaxidae. Three species have their geographic distributions greatly expanded: Bayericerithium bayeri Petuch, 2001 from Pernambuco to Rio Grande do Norte and Ceará states (north) and to Bahia and Espírito Santo states (south), Brazilian coast; Ittibittium oryza (Mörch, 1876), from the Caribbean to the SW Atlantic; and Angiola lineata (Costa, 1778), from Trindade Island, Brazil to the Abrolhos Slope, nearly 870 km westward. Four species reported herein had their bathymetric ranges greatly expanded: Alaba incerta (d’Orbigny, 1841) from 0-40 m to 300 m; B. bayeri from 0-2 m to 120 m (live specimens); Litiopa melanostoma Rang, 1829 from 0-805 m to 1,550 m; Fossarus orbignyi Fischer, 1864 from 0-40 to 830 m (shells only)

Concise server-wide causality management for eventually consistent data stores

Large scale distributed data stores rely on optimistic replication to scale and remain highly available in the face of net work partitions. Managing data without coordination results in eventually consistent data stores that allow for concurrent data updates. These systems often use anti-entropy mechanisms (like Merkle Trees) to detect and repair divergent data versions across nodes. However, in practice hash-based data structures are too expensive for large amounts of data and create too many false conflicts. Another aspect of eventual consistency is detecting write conflicts. Logical clocks are often used to track data causality, necessary to detect causally concurrent writes on the same key. However, there is a nonnegligible metadata overhead per key, which also keeps growing with time, proportional with the node churn rate. Another challenge is deleting keys while respecting causality: while the values can be deleted, perkey metadata cannot be permanently removed without coordination. Weintroduceanewcausalitymanagementframeworkforeventuallyconsistentdatastores,thatleveragesnodelogicalclocks(BitmappedVersion Vectors) and a new key logical clock (Dotted Causal Container) to provides advantages on multiple fronts: 1) a new efficient and lightweight anti-entropy mechanism; 2) greatly reduced per-key causality metadata size; 3) accurate key deletes without permanent metadata.(undefined

DottedDB: anti-entropy without merkle trees, deletes without tombstones

To achieve high availability in the face of network partitions, many distributed databases adopt eventual consistency, allow temporary conflicts due to concurrent writes, and use some form of per-key logical clock to detect and resolve such conflicts. Furthermore, nodes synchronize periodically to ensure replica convergence in a process called anti-entropy, normally using Merkle Trees. We present the design of DottedDB, a Dynamo-like key-value store, which uses a novel node-wide logical clock framework, overcoming three fundamental limitations of the state of the art: (1) minimize the metadata per key necessary to track causality, avoiding its growth even in the face of node churn; (2) correctly and durably delete keys, with no need for tombstones; (3) offer a lightweight anti-entropy mechanism to converge replicated data, avoiding the need for Merkle Trees. We evaluate DottedDB against MerkleDB, an otherwise identical database, but using per-key logical clocks and Merkle Trees for anti-entropy, to precisely measure the impact of the novel approach. Results show that: causality metadata per object always converges rapidly to only one id-counter pair; distributed deletes are correctly achieved without global coordination and with constant metadata; divergent nodes are synchronized faster, with less memory-footprint and with less communication overhead than using Merkle Trees.This work is financed by the ERDF – European Regional Development Fund through the Operational Programme for Competitiveness and Internationalisation - COMPETE 2020 Programme within project «POCI-01-0145-FEDER-006961», and by National Funds through the Portuguese funding agency, FCT - Fundação para a Ciência e a Tecnologia as part of project «UID/EEA/50014/2013».info:eu-repo/semantics/publishedVersio

Diversity of the Nests of Social Wasps (Hymenoptera: Vespidae: Polistinae) in the Northern Pantanal, Brazil

Some species of wasps demonstrate plasticity with diverse nesting habits according to the environmental conditions and substrates used for building the nests, while others are restricted to habitats with specific conditions and may exhibit some degree of fide-lity. The aim of this study was to estimate species richness and abundance of nests of Polistini and Epiponini wasps in four landscape units in the Pantanal of Poconé, Retiro Novo Farm, southwestern Mato Grosso state, Brazil. The nests of social wasps were sampled in four plant physiognomies locally known as cambarazal, landizal, pombeiral and campo limpo from August 25, 2011 to April 11, 2012, being recorded 308 nests of eight genera and 14 species of social wasps. The highest number of nests belongs to Polybia ruficeps xanthops (32.69%), Poly. sericea (24.27%) and Synoeca surinama (15.21%). The highest species richness was recorded in cambarazal and the highest abundance of nests in pombeiral, while campo limpo showed the lowest richness and abundance of nests. The nests of S. surinama were associated with cambarazal and landizal (IndVal = 93.3, P = 0.001), while the nests of Poly. ruficeps xanthops and Poly. chrysothorax were associated with cambarazal, landizal and pombeiral (IndVal = 97, P = 0.001). There was lower abundance and lower species richness of wasps in campo limpo. These results demonstrate that the maintenance of forest environments in the Pantanal is essential for the establishment and maintenance of social wasp nests

Gene structure and splicing in schistosomes

Schistosomes are blood dwelling platyhelminths with a complex life cycle and persist in the definitive host during decades, indicating that they are very successful parasites. The challenge of infecting two hosts from different evolutionary branches, namely an invertebrate snail and a vertebrate, suggests that Schistosomes must display a very sophisticated genetic program to circumvent all the barriers imposed by the hosts' immune systems. Recent large-scale genome and transcriptome data from Schistosomes are facilitating the analysis of gene structure and splicing. Studying the structure of genes coding for secreted proteins is of particular interest since these proteins mediate processes in the host-parasite interface. Recent description of Micro-Exon Genes (MEGs), polymorphic mucin genes (SmPoMucs) and venom allergen-like (SmVALs) proteins with unusual gene structure apparently oriented towards generation of protein variability through alternate splicing, and the presence of multiple copies of these genes, indicate that the parasite developed a sophisticated system to interact with its hosts. This opens up opportunities for further studies with the use of proteomic techniques to better characterize the protein variability created by these systems and their role in parasite survival. Complete description of the functions of these variable proteins will greatly contribute to our understanding of host-parasite interactions

Brief announcement: efficient causality tracking in distributed storage systems with dotted version vectors

Version vectors (VV) are used pervasively to track dependencies between replica versions in multi-version distributed storage systems. In these systems, VV tend to have a dual functionality: identify a version and encode causal dependencies. In this paper, we show that by maintaining the identifier of the version separate from the causal past, it is possible to verify causality in constant time (instead of O(n) for VV) and to precisely track causality with information with size bounded by the degree of replication, and not by the number of concurrent writers.(undefined

Evaluating dotted version vectors in Riak

The NoSQL movement is rapidly increasing in importance, acceptance and usage in major (web) applications, that need the partition-tolerance and availability of the CAP theorem for scalability purposes, thus sacrificing the consistency side. With this approach, paradigms such as Eventual Consistency became more widespread. An eventual consistent system must handle data divergence and conflicts, that have to be carefully accounted for. Some systems have tried to use classic Version Vectors (VV) to track causality, but these reveal either scalability problems or loss of accuracy (when pruning is used to prevent vector growth). Dotted Version Vectors (DVV) is a novel mechanism for dealing with data versioning in eventual consistent systems, that allows both accurate causality tracking and scalability both in the number of clients and servers, while limiting vector size to replication degree. In this paper we describe briefly the challenges faced when incorporating DVV in Riak (a distributed key-value store), evaluate its behavior and performance, and discuss the advantages and disadvantages of this specific implementation