Kirigami Actuators

Thin elastic sheets bend easily and, if they are patterned with cuts, can deform in sophisticated ways. Here we show that carefully tuning the location and arrangement of cuts within thin sheets enables the design of mechanical actuators that scale down to atomically-thin 2D materials. We first show that by understanding the mechanics of a single, non-propagating crack in a sheet we can generate four fundamental forms of linear actuation: roll, pitch, yaw, and lift. Our analytical model shows that these deformations are only weakly dependent on thickness, which we confirm with experiments at centimeter scale objects and molecular dynamics simulations of graphene and MoS$_{2}$ nanoscale sheets. We show how the interactions between non-propagating cracks can enable either lift or rotation, and we use a combination of experiments, theory, continuum computational analysis, and molecular dynamics simulations to provide mechanistic insights into the geometric and topological design of kirigami actuators.Comment: Soft Matter, 201

Neutrino Masses in a Two Higgs Doublet Model with a U(1) Gauge Symmetry

General Two Higgs Doublet Models (2HDM) are popular Standard Model extensions but feature flavor changing interactions and lack neutrino masses. We discuss a 2HDM where neutrino masses are generated via type I seesaw and propose an extension where neutrino masses are generated via a type II seesaw mechanism with flavor changing interactions being absent via the presence of a U(1) gauge symmetry. After considering a variety of bounds such as those rising from collider and electroweak precision we show that our proposal stands as a UV complete 2HDM with a dark photon where neutrino masses and flavor changing interactions are addressed. A possible dark matter realization is also discussed.Comment: 2 figures, 44 pages. Version accepted for publication in JHE

Using soft computing tools for piezometric level prediction

The safety assessment of dams is a complex task that is made possible thanks to a constant monitoring of pertinent parameters. Once collected, the data is processed by statistical analysis models in order to describe the behaviour of the structure. The aim of those models is to detect early signs of abnormal behaviour so as to take corrective actions when required. Because of the uniqueness of each structure, the behavioural models need to adapt to each of these structures, thus flexibility is required. Simultaneously, generalisation capacities are sought, so a trade-off has to be found. This flexibility is even more important when the analysed phenomenon is characterised by non-linear features, as it is the case for the piezometric levels (PL) monitored at the rockconcrete interface of the arch dam that this study focuses on. In that case, the linear models that are classically used by engineers show insufficient performances. Consequently, interest naturally grows for the advanced learning algorithms known as machine learning techniques. In this work, the aim is to compare the predictive performances and generalization capacities of three different Data Mining algorithms that are likely to be used for monitoring purposes: Artificial Neural Networks (ANN), Support Vector Machines (SVM) and Multiple Regression (MR). The achieved results show that SVM and ANN stand out as the most efficient algorithms, when it comes to analysing non-linear monitored phenomenon. Through a global sensitivity analysis, the influence of the models’ attributes was measured, evidencing a high impact of Z (relative trough) in PL prediction.info:eu-repo/semantics/publishedVersio

Power Allocation, Relay Selection, and User Pairing for Cooperative NOMA Systems with Rate Fairness

Funding Information: This research was partially funded by Fundac¸ão para a Ciência e Tecnologia under the Projects CoSHARE (PTDC/EEI-TEL/30709/2017), UIDB/04111/2020, IF/00325/2015, and UIDB/50008/2020.Assuming a cooperative non-orthogonal multiple access (NOMA) system with rate fairness in a scenario with multiple users and arbitrary relays, this paper investigates adaptive power allocation (PA), relay selection (RS), and user pairing (UP) policies. Specifically, two adaptive PA optimization problems are formulated, one at the base station (BS) and another at the selected relays. Closed-form expressions for the power allocation factors are derived as well as an algorithm that provides the optimal solution at the BS. In order to show the superiority of the proposed study, our results are compared with other benchmark schemes in terms of outage probability, Jain's fairness index, and average sum rate.publishersversionpublishe

Physical and physiological quality of Jatropha curcas L. seeds at different maturity stages using image analysis

Aim of study: To assess the potential of automated X-ray image analysis to evaluate the physical characteristics of Jatropha curcas seeds, and to relate the parameters obtained with the physiological quality of the seeds harvested at different maturity stages.Area of study: Experimental area of Agronomy Department, Federal University of Viçosa (UFV), Brazil.Material and methods: The fruits were harvested from 20 plants, based on the external skin color (green, yellow, brownish-yellow and brown). The study was performed by automated and visual analysis of radiographic images of the seeds, in which measurements of tissue integrity, density and seed filling were performed. Seed dry matter, germination and seedling growth were also analysed.Main results: Variables obtained through automated analysis of radiographic images correlated significantly with all physiological variables (r > 0.9), as well as visual image evaluations (r > 0.75). The seeds extracted from green fruits presented lower tissue integrity and lower physiological quality. Radiographic analysis was efficient for monitoring J. curcas seed quality at different maturity stages. Morpho-anatomical parameters obtained from X-ray analysis were highly correlated with seed physiological attributes.Research highlights: It is important to develop and improve methodologies based on lower-cost techniques, such as X-ray analysis. In this context, we verified that X-ray images can be used for monitoring J. curcas seed filling and maturation. Radiographic images of seeds can be analyzed automatically with ImageJ software. Internal morphology and physical characteristics of seeds have relationship with their physiological quality

Fatty Acid Profile of Elephant Grass Pastures with Different Grazing Heights

Ruminant milk and meat are a source of CLA and omega-3 in the human diet and these fatty acids (FAs) have a beneficial effect on human health (Mcguire and Mcguire 2000). The increase in CLA and omega-3 in ruminant products is mainly related to proportion of C18:2 and C18:3 in the animal feed, like forage and to incomplete ruminal biohydrogenation (Bauman et al. 2000). Evaluation of FAs have been performed in temperate forage pastures, without the interaction of animal grazing, and presenting samples collected at ground level and at fixed re-growth intervals or seasons as the main sampling criteria. Therefore, the objective of this study was to evaluate the proportion of fatty acid in strata of elephant grass cv. Pioneiro with different grazing heights

Are opportunities being missed? Burden of HIV, STI and TB, and unawareness of HIV among african migrants

Sub-Saharan African migrants (SSAMs) have been disproportionately affected by infectious disease burden. We aimed to identify correlates of HIV, past sexually transmitted infection (STI) and past Tuberculosis infection (TB), as well as examine HIV seropositivity unawareness and testing history among SSAMs. A venue-based sample of 790 SSAMs completed a cross-sectional biobehavioral survey on sexual practices, HIV testing and self-reported infectious diseases; an HIV rapid test was offered. Overall, 5.4% of participants were HIV-positive and 16.7% reported a past STI. Odds of being HIV positive or having a past STI were higher among participants with low socioeconomic status and who experienced violence from a partner. Increased odds of having a past STI were also found among long-term migrants and those who reported sexual risk behaviors. In total, 4.1% of participants had TB in the past; these were more likely male and HIV positive. Unawareness of HIV-positive status was notably high (35%). Half of the participants had never been tested for HIV before, including over a third of those who had STI or TB in the past. Efforts are needed to reduce missed opportunities for HIV/STIs prevention and uptake of HIV testing among SSAMs through more integrated care, while addressing social determinants of infectious diseases.publishersversionpublishe

Plastin and spectrin cooperate to stabilize the actomyosin cortex during cytokinesis

Cytokinesis, the process that partitions the mother cell into two daughter cells, requires the assembly and constriction of an equatorial actomyosin network. Different types of non-motor F-actin crosslinkers localize to the network, but their functional contribution remains poorly understood. Here, we describe a synergy between the small rigid crosslinker plastin and the large flexible crosslinker spectrin in the C. elegans one-cell embryo. In contrast to single inhibitions, co-inhibition of plastin and the βH-spectrin (SMA-1) results in cytokinesis failure due to progressive disorganization and eventual collapse of the equatorial actomyosin network. Cortical localization dynamics of non-muscle myosin II in co-inhibited embryos mimic those observed after drug-induced F-actin depolymerization, suggesting that the combined action of plastin and spectrin stabilizes F-actin in the contractile ring. An in silico model predicts that spectrin is more efficient than plastin at stabilizing the ring and that ring formation is relatively insensitive to βH-spectrin length, which is confirmed in vivo with a sma-1 mutant that lacks 11 of its 29 spectrin repeats. Our findings provide the first evidence that spectrin contributes to cytokinesis and highlight the importance of crosslinker interplay for actomyosin network integrity

Deteção remota multiespectral e hiperespetral como fonte de conhecimento no sector português da Faixa Piritosa Ibérica

ABSTRACT: Remote sensing is an invaluable tool to increase geological and mining knowledge, due to its screening view and variable discrimination and identification capabilities of the target materials. In this study an overview of remote sensing research developed and ongoing within the Portuguese sector of the Iberian Pyrite Belt (PSIPB) since 2000 is given. Multispectral and hyperspectral datasets were processed using hybrid methods, related both to general and detailed characterization, to: 1) support geological, mineral and hydrothermal mapping, 2) generate products derived from multivariate analysis and band ratios, 3) enhance correlation with radiometric data, 4) provide elements for environmental assessment concerning mining activity, 5) map Acid Mine Drainage (AMD) based on spectral field signatures, 6) quantify AMD based on high correlation mineralogical mapping, and 7) monitor AMD. The results highlight the importance of the quantitative digital support given by remote sensing tools within the Portuguese Sector of the Iberian Pyrite Belt (PSIPB), ruled by georesource exploitation in different stages of the Mine Lyfe Cycle.RESUMO: A deteção remota é uma ferramenta valiosa para aumentar o conhecimento geológico e mineiro, devido à visão sinótica e à capacidade variável de discriminação e identificação dos materiais-alvo. Neste trabalho dá-se uma visão geral da investigação através dos trabalhos de deteção remota desenvolvidos e em curso no Setor Português da Faixa Piritosa Ibérica (SPFPI) desde 2000. Os dados multiespectrais e hiperespectrais foram processados usando métodos híbridos quer para a sua caracterização geral quer detalhada para: 1) apoiar a cartografia geológica, de mineralizações e sistemas hidrotermais, 2) gerar produtos de análise multivariada e rácios de bandas, 3) melhorar a correlação com dados radiométricos 4) fornecer elementos para avaliação ambiental em áreas mineiras, 5) cartografar a drenagem ácida de mina (DAM) com assinaturas espectrais de campo, 6) quantificar a DAM através de cartografia mineralógica de alta correlação, e 7) monitorizar a DAM. Destaca-se a importância do suporte digital quantitativo dado por ferramentas de deteção remota no SPFPI, regido pela exploração de georrecursos em diferentes fases do Ciclo de Vida das Minas.info:eu-repo/semantics/publishedVersio