In-plane elastic wave propagation and band-gaps in layered functionally graded phononic crystals

AbstractIn-plane wave propagation in layered phononic crystals composed of functionally graded interlayers arisen from the solid diffusion of homogeneous isotropic materials of the crystal is considered. Wave transmission and band-gaps due to the material gradation and incident wave-field are investigated. A classification of band-gaps in layered phononic crystals is proposed. The classification relies on the analysis of the eigenvalues of the transfer matrix for a unit-cell and the asymptotics derived for the transmission coefficient. Two kinds of band-gaps, where the transmission coefficient decays exponentially with the number of unit-cells are specified. The so-called low transmission pass-bands are introduced in order to identify frequency ranges, in which the transmission is sufficiently low for engineering applications, but it does not tend to zero exponentially as the number of unit-cells tends to infinity. A polyvalent analysis of the geometrical and physical parameters on band-gaps is presented

The impact of COVID-19 on labor migration and the roles of small-scale farming in the pandemic in Vietnam

Drawing on in-depth interviews of migrant workers and their families in rural Vietnam, this study explores the impact of the COVID-19 pandemic on transnational and rural-urban migration as well as the role of small-scale farming in remittance-receiving households. Fieldwork was conducted in two provinces: the Son La province where ethnic minority women and men work in urban construction sites, and the Ha Tinh province where young men work in East Asia, such as Japan, South Korea, and Taiwan. Research findings show that in Son La, the pandemic exacerbated the already precarious lives and livelihoods of labor migrants, especially women and children. On the other hand, in Ha Tinh non-market-oriented small-scale farming and livestock production support remittance-receiving households, thereby limiting the impact of reduced remittances from transnational migration in the short-term. In both study sites, the pandemic did not change respondents’ perceptions of livelihood strategies. Labor migration remains the only available option for Son La farmers from the poor households to provide for their families and the best option for many young men in Ha Tinh to gain financial autonomy. These individuals are deeply affected by structural injustice in the commodification of the labor market, which is inherently unequal and exploitative. Current agricultural development must offer diverse options to accommodate the various needs of marginalized households that depend on off-farm incomes as well as small-scale farming

Women’s roles and opportunities in cassava value chains in Son La province in Vietnam: A technical report

Cassava is a major export-oriented cash crop in Vietnam. Unlike other cash crops, such as coffee, fruits, and maize, cassava requires limited agricultural input and labour and can grow in nutrient-poor uplands. Research on cassava breeding, seed systems and value chains in Southeast Asia is increasingly focused on market-oriented aspects such as developing hybrid varieties favourable to the cassava starch industry, disease control on large scale farms, and seed systems driven by the private sector. However, in the northern mountainous areas of Vietnam, ethnic minority farmers use cassava roots, leaves and sticks for numerous reasons, including starch production, fish and animal feed, firewood, and home consumption. Women play significant roles in those non market-oriented activities (often collecting left-over small roots in the field, drying roots, and cutting leaves and stems) but little is known about how this work influences women’s roles, decision-making and opportunities in cassava value chains. Hence, this study provides that data with an eye to see how women may find more opportunity for creating small business enterprises with cassava. Fieldwork was conducted in July 2021 in the Chieng La commune (Thuan Chau district) and the Muong Bon Commune (Mai Son district). Findings show that although women are less involved in decision making on cassava production and overall agricultural investment, they play important roles in cassava production and post-harvest activities. Therefore, it is extremely important to collect and analyze women’s preferences, concerns and constraints in cassava research and interventions. In the conclusion, we highlight additional areas for research on this topic

Discovering Spatio-Temporal Patterns in Precision Agriculture Based on Triclustering

Agriculture has undergone some very important changes over the last few decades. The emergence and evolution of precision agri culture has allowed to move from the uniform site management to the site-specific management, with both economic and environmental advan tages. However, to be implemented effectively, site-specific management requires within-field spatial variability to be well-known and character ized. In this paper, an algorithm that delineates within-field management zones in a maize plantation is introduced. The algorithm, based on tri clustering, mines clusters from temporal remote sensing data. Data from maize crops in Alentejo, Portugal, have been used to assess the suit ability of applying triclustering to discover patterns over time, that may eventually help farmers to improve their harvests.Ministerio de Economía y Competitividad TIN2017-88209-C2Fundaçao para a Ciéncia e a Tecnologia (FCT) UIDB/04561/202

Phosphine Resistance in the Rust Red Flour Beetle, Tribolium castaneum (Coleoptera: Tenebrionidae): Inheritance, Gene Interactions and Fitness Costs

The recent emergence of heritable high level resistance to phosphine in stored grain pests is a serious concern among major grain growing countries around the world. Here we describe the genetics of phosphine resistance in the rust red flour beetle Tribolium castaneum (Herbst), a pest of stored grain as well as a genetic model organism. We investigated three field collected strains of T. castaneum viz., susceptible (QTC4), weakly resistant (QTC1012) and strongly resistant (QTC931) to phosphine. The dose-mortality responses of their test- and inter-cross progeny revealed that most resistance was conferred by a single major resistance gene in the weakly (3.2×) resistant strain. This gene was also found in the strongly resistant (431×) strain, together with a second major resistance gene and additional minor factors. The second major gene by itself confers only 12–20× resistance, suggesting that a strong synergistic epistatic interaction between the genes is responsible for the high level of resistance (431×) observed in the strongly resistant strain. Phosphine resistance is not sex linked and is inherited as an incompletely recessive, autosomal trait. The analysis of the phenotypic fitness response of a population derived from a single pair inter-strain cross between the susceptible and strongly resistant strains indicated the changes in the level of response in the strong resistance phenotype; however this effect was not consistent and apparently masked by the genetic background of the weakly resistant strain. The results from this work will inform phosphine resistance management strategies and provide a basis for the identification of the resistance genes

Artifacts In Magnetic Resonance Imaging and Computed Tomography Caused By Dental Materials

BACKGROUND: Artifacts caused by dental restorations, such as dental crowns, dental fillings and orthodontic appliances, are a common problem in MRI and CT scans of the head and neck. The aim of this in-vitro study was to identify and evaluate the artifacts produced by different dental restoration materials in CT and MRI images. METHODS: Test samples of 44 materials (Metal and Non-Metal) commonly used in dental restorations were fabricated and embedded with reference specimens in gelatin moulds. MRI imaging of 1.5T and CT scan were performed on the samples and evaluated in two dimensions. Artifact size and distortions were measured using a digital image analysis software. RESULTS: In MRI, 13 out of 44 materials produced artifacts, while in CT 41 out of 44 materials showed artifacts. Artifacts produced in both MRI and CT images were categorized according to the size of the artifact. SIGNIFICANCE: Metal based restoration materials had strong influence on CT and less artifacts in MRI images. Rare earth elements such as Ytterbium trifluoride found in composites caused artifacts in both MRI and CT. Recognizing these findings would help dental materials manufacturers and developers to produce materials which can cause less artifacts in MRI and CT images

Variable Anisotropic Brain Electrical Conductivities in Epileptogenic Foci

Source localization models assume brain electrical conductivities are isotropic at about 0.33 S/m. These assumptions have not been confirmed ex vivo in humans. This study determined bidirectional electrical conductivities from pediatric epilepsy surgery patients. Electrical conductivities perpendicular and parallel to the pial surface of neocortex and subcortical white matter (n = 15) were measured using the 4-electrode technique and compared with clinical variables. Mean (±SD) electrical conductivities were 0.10 ± 0.01 S/m, and varied by 243% from patient to patient. Perpendicular and parallel conductivities differed by 45%, and the larger values were perpendicular to the pial surface in 47% and parallel in 40% of patients. A perpendicular principal axis was associated with normal, while isotropy and parallel principal axes were linked with epileptogenic lesions by MRI. Electrical conductivities were decreased in patients with cortical dysplasia compared with non-dysplasia etiologies. The electrical conductivity values of freshly excised human brain tissues were approximately 30% of assumed values, varied by over 200% from patient to patient, and had erratic anisotropic and isotropic shapes if the MRI showed a lesion. Understanding brain electrical conductivity and ways to non-invasively measure them are probably necessary to enhance the ability to localize EEG sources from epilepsy surgery patients