Modeling rammed earth wall using discrete element method

International audienceRammed earth is attracting renewed interest throughout the world thanks to its “green” characteristics in the context of sustainable development. Several research studies have thus recently been carried out to investigate this material. Some of them attempted to simulate the rammed earth’s mechanical behavior by using analytical or numerical models. Most of these studies assumed that there was a perfect cohesion at the interface between earthen layers. This hypothesis proved to be acceptable for the case of vertical loading, but it could be questionable for horizontal loading. To address this problem, discrete element modeling seems to be relevant to simulate a rammed earth wall. To our knowledge, no research has been conducted thus far using discrete element modeling to study a rammed earth wall. This paper presents an assessment of the discrete element modeling’s robustness for rammed earth walls. Firstly, a brief description of the discrete element modeling is presented. Then the parameters necessary for discrete element modeling of the material law of the earthen layers and their interfaces law following the Mohr–Coulomb model with a tension cut-off and post-peak softening were given. The relevance of the model and the material parameters were assessed by comparing them with experimental results from the literature. The results showed that, in the case of vertical loading, interfaces did not have an important effect. In the case of diagonal loading, model with interfaces produced better results. Interface characteristics can vary from 85 to 100% of the corresponding earthen layer’s characteristics

On chip optical neural networks based on MMI microring resonators for image classification

We propose a new on-chip optical neural network (OONN) based on multimode interference-microring resonators (MMI-RRs). The suggested structure eliminates the need for wavelength division multiplexers (WDM) to create an optical neuron on a single chip. New microring resonator structure based on 4×4 MMI coupler with a size of 24µm × 2900 µm is used for the basic elements of the computation matrix, as a result a higher bandwidth and free spectral range (FSR) can be achieved. The Si3N4 platform along with the graphene sheet is designed to modulate the signals and weights of the neural networks at a very high speed. The Si3N4 can provide wide range of operating wavelengths and can work directly with the wavelengths of color images. The structure's benefits include rapid computing speed, little loss, and the ability to handle both positive and negative values. The OONN has been applied to the MNIST dataset with a speed faster than 2.8 to 14x times compared with the conventional GPU methods.This research is funded by Vietnam National Founda-tion for Science and Technology Development (NA-FOSTED) under grant number 103.03-2018.354

Temperature and food quantity effects on the harpacticoid copepod <i>Nitocra spinipes</i>: combining in vivo bioassays with population modeling

The harpacticoid copepod Nitocra spinipes has become a popular model species for toxicity testing over the past few decades. However, the combined influence of temperature and food shortage, two climate change-related stressors, has never been assessed in this species. Consequently, effects of three temperatures (15, 20 and 25°C) and six food regimes (between 0 and 5 × 105 algal cells/mL) on the life cycle of N. spinipes were examined in this study. Similarly to other copepod species, development times and brood sizes decreased with rising temperatures. Mortality was lowest in the 20°C temperature setup, indicating a close-by temperature optimum for this species. Decreasing food concentrations led to increased development times, higher mortality and a reduction in brood size. A sex ratio shift toward more females per male was observed for increasing temperatures, while no significant relationship with food concentration was found. Temperature and food functions for each endpoint were integrated into an existing individual-based population model for N. spinipes which in the future may serve as an extrapolation tool in environmental risk assessment. The model was able to accurately reproduce the experimental data in subsequent verification simulations. We suggest that temperature, food shortage, and potentially other climate change-related stressors should be considered in environmental risk assessment of chemicals to account for non-optimal exposure conditions that may occur in the field. Furthermore, we advocate combining in vivo bioassays with population modeling as a cost effective higher tier approach to assess such considerations

Introducing an agricultural app to rice farmers: A pilot study in Can Tho, Vietnam

Plantix is an agricultural app developed by a private company based in Germany which offers a diagnosis and advice for more than 30 crops. It has great potential as a new form of extension service complementing a traditional face-to-face extension service. The CGIAR Plant Health Initiative seeks to introduce the app as part of a package of innovations available for integrated pest and disease management to facilitate behavioral change among farmers. Plantix has been widely used in India but has not yet become very common in Vietnam. The aim of this pilot study was to test the usability of Plantix app for progressive rural rice growers in Vinh Thanh District, Can Tho City, Vietnam. A group of 15 farmers (5 woman and 11 men) participated in the training on use of the app and provided feedback after a two-week trial. The results show that the farmers seem to have some trust issues with the app’s diagnosis, as it reportedly failed to identify or distinguish early signs of certain pests and diseases on young rice. Nevertheless, the farmers showed interest in using Plantix app and considered it a useful tool once its early detection capacity is improved. The participants were experienced large-scaled rice farmers who were already quite familiar with the symptoms of regular pests and diseases. They agreed with the knowledge provided by Plantix. The farmers appeared to be conscious of the recommended dosage of chemical pesticides as written on product labels, however, the current local practice still involves overusing. This suggests that additional measures might be needed along with the introduction and dissemination of Plantix for a stronger impact on farmers’ behaviors. The app can be very useful for farmers when they start growing new crops, when there are new pests and diseases, and when they have difficulties distinguishing one disease from others with similar symptoms. Some of the farmers suggested the need for information about new generation pesticides. They also expressed the need for recommendations of specific “top-ranked” pesticide products, to help them navigate the large number of products and brands currently on the market. Considering the gender division of labor and decision-making, the results show that men are usually responsible for pest and disease management, but women are also involved in decision-making to some extent. It will be interesting to observe how women’s improved knowledge on pest and disease management obtained through Plantix will lead to change in household decisions on pesticide use. The participating farmers use various sources such as TV, Internet, extension workers, input suppliers and peer farmers as means of accessing information and exchanging knowledge. Male farmers tend to learn new agricultural technologies through social networks within their villages and the Internet more often, while the women do that through the Internet and TV. However, both groups trusted their own experience the most. Therefore, introducing the community’s key farmers to new technologies though demonstration and success stories could work as a strategy to ignite behavior change among peer farmers. In addition, communication via the Internet and TV could quickly reach a large number of farmers. Involving input suppliers and extension workers in the introduction of the Plantix app could also be helpful. While this pilot study focused on large-scaled farmers, there are smallholder farmers from poor households in some remote areas in the Mekong Delta. Their needs and knowledge may be significantly different from those of progressive farmers. Introducing the app to different types of farmers can help us understand the diverse needs and priorities of farmers in the process of digitalization

Effectiveness of cervical pessary compared to cervical cerclage with or without vaginal progesterone for the prevention of preterm birth in women with twin pregnancies and a short cervix : Study protocol for a two-by-two factorial randomised clinical trial

Peer reviewedPublisher PD

Temporin L and aurein 2.5 have identical conformations but subtly distinct membrane and antibacterial activities

Frogs such as Rana temporaria and Litoria aurea secrete numerous closely related antimicrobial peptides (AMPs) as an effective chemical dermal defence. Damage or penetration of the bacterial plasma membrane is considered essential for AMP activity and such properties are commonly ascribed to their ability to form secondary amphipathic, α-helix conformations in membrane mimicking milieu. Nevertheless, despite the high similarity in physical properties and preference for adopting such conformations, the spectrum of activity and potency of AMPs often varies considerably. Hence distinguishing apparently similar AMPs according to their behaviour in, and effects on, model membranes will inform understanding of primary-sequence-specific antimicrobial mechanisms. Here we use a combination of molecular dynamics simulations, circular dichroism and patch-clamp to investigate the basis for differing anti-bacterial activities in representative AMPs from each species; temporin L and aurein 2.5. Despite adopting near identical, α-helix conformations in the steady-state in a variety of membrane models, these two AMPs can be distinguished both in vitro and in silico based on their dynamic interactions with model membranes, notably their differing conformational flexibility at the N-terminus, ability to form higher order aggregates and the characteristics of induced ion conductance. Taken together, these differences provide an explanation of the greater potency and broader antibacterial spectrum of activity of temporin L over aurein 2.5. Consequently, while the secondary amphipathic, α-helix conformation is a key determinant of the ability of a cationic AMP to penetrate and disrupt the bacterial plasma membrane, the exact mechanism, potency and spectrum of activity is determined by precise structural and dynamic contributions from specific residues in each AMP sequence

Hepatitis E virus seroprevalence in indigenous residents of the Hà Giang northern province of Vietnam

Vietnam is an endemic territory of the South-East Asia in terms of the prevalence of hepatitis E virus. However, the data on the prevalence of HEV infection among the indigenous population of Vietnam are limited, whereas the data on various minor ethnic groups are not available. Рopulation of the Northern province Hà Giang is characterized by ethnic diversity and consists of about 22 ethnic groups that have preserved their ethnic identity determining the features of their lifestyle and farming. The goal of the current study was to conduct a cross-sectional examination to assess prevalence of serological markers of HEV infection in the indigenous population of the Northern province of Vietnam, Hà Giang. Materials and methods. A total of 1127 healthy indigenous residents aged 18 to 83 years (average age 42.8±1.5) who lived in three regions (Yên Minh, Bắc Mê and Đông Văn) of Hà Giang province in 2019 were enrolled in the study. The presence of HEV-specific IgG antibodies (anti-HEV IgG) was determined by the ELISA using kits “DS-IFA-ANTI-HEV-G” (LLC NPO “Diagnostic Systems”, Russia). Results. The prevalence of anti-HEV IgG antibodies in the indigenous population in the Hà Giang province was 74.4% (838/1127; 95% CI 71.7–76.8), with the peak occurrence of anti-HEV IgG (87.6%) found in Đông Văn region, which was significantly higher compared to those in the Bắc Mê (χ2 = 16.37, p = 0.000052) and Yên Minh (χ2 = 214.64, p &lt; 0.00001) regions. The Yên Minh Region was characterized by the lowest percentage of subjects involved in the epidemic process (χ2 = 77.55, p &lt; 0.00001). No significant gender-related differences were detected in antiHEV IgG level both in general and in individual regions. The peak frequency of anti-HEV IgG (85.9%) was found in the H’mong ethnic group, which was significantly higher than in the Tay ethnic groups (χ2 = 77.32, p &lt; 0.00001) and in the remaining minor ethnic groups (χ2 = 63.44, p &lt; 0.00001). Conclusion. The results of this study indicate a high seroprevalence of hepatitis E virus in the minor ethnic groups, which preserve the national lifestyle in the Hà Giang province of the Northern Vietnam. As the Hà Giang province is located in remote mountain areas, a number of which are still difficult to access, its low economic status, poor sanitary and hygienic living conditions, lack of high-quality water supply, multinational population following different lifestyles, the contact of population with natural potential sources of HEV infection, including various wild and domestic animals, contribute to the successful spread of the hepatitis E virus in the region and the involvement of all populational age groups in the epidemic process. Taking into account the rapid development of the tourism industry in the Hà Giang Province particularly in the Đông Văn Region, where the Đông Văn Karst Plateau Geopark being recognized by UNESCO as national treasure is located, the results of this study emphasize a need to plan and perform the events aimed for preventing and monitoring HEV infection in endemic regions in Vietnam in order to reduce a risk of spread of hepatitis E virus not only inside, but also outside the country

Upgrading of shielding for rare decay search in CANDLES

In the CANDLES experiment aiming to search for the very rare neutrino-less double beta decays (0νββ) using 48Ca, we introduced a new shielding system for high energy γ-rays from neutron captures in massive materials near the detector, in addition to the background reduction for 232Th decays in the 0νββ target of CaF2 crystals. The method of background reduction and the performance of newly installed shielding system are described