Controlled release systems were developed using biodegradable polymers/copolymers via polycondensation of glycerol with acids (citric, adipic, and succinic) with potassium chloride (KCl) 0, 10, 20, ...and 40 wt% followed by crosslinking at 120°C. Polymers were characterized by thermogravimetry, X‐ray diffraction, Fourier transform infrared spectroscopy, scanning electron microscopy and UV‐Vis spectroscopy. All are thermally stable up to 200°C, therefore suitable for release in countries where temperatures reach 50°C. Fractographic analysis showed rubbery (rough and ductile) and hard (smooth and brittle) polymers depending on the acid used. The release profiles showed that hydrophilic (polar) polymers are easily hydrolyzed, generating faster release reaching 52% in 120 h. Less polar polymers delay KCl release below 20% at the same time. Therefore, it was possible to adjust the release by controlling the fertilizer content and the type of polymer, designing a fast or slow release to meet the needs of a given crop.
The efficiency of combining oestrous induction via a light program (16 h of light and 8 h of darkness for 60 days, ending on Day 0 – D0) with cloprostenol administration, followed by the male effect ...or not, was tested in acyclic Saanen goats during the non‐breeding season (June/2019 to January/2020). Initially, all animals (males and females) were submitted to the described light program; 60 days after its ending (D60), the females were divided into two groups, with (G1; n = 67) or without (G2; n = 61) a male effect from D60 to D75 after the light program. At D75, both groups received two cloprostenol doses (120 μg; intramuscular) 7.5 days apart (D75 and D82.5). Artificial insemination was performed at a specific time according to the oestrous onset (approximately 68.4 ± 1.2 h between the second cloprostenol dose and IA). Ultrasound scans were performed at different intervals to evaluate follicular dynamics and confirm pregnancy. At the first cloprostenol dose (D75), the proportion of does with at least a corpus luteum (CL), which indicates resumed cyclicity, was greater in G1 than in G2 (85.2% vs. 48.8%; p < .05), although no difference was found at the second dose (p > .05). The adjusted pregnancy rates (number of pregnant goats/oestrous goats) differed between G1 and G2 (21.7% vs. 42.0%; p < .05). G1 also showed a higher frequency of functional CL (based on blood flow and morphology) compared to G2 (96.9% vs. 66.7%; p < .05) at D116. A male effect using photo‐stimulated bucks after the first cloprostenol dose increased the number of does presenting CL after buck removal, and no impairment in the pregnancy rates of multiparous does was found.
Biodegradable adhesives are of great scientific and technological interest as an alternative to conventional commercial products, which generally can release toxic substances and take a long time to ...degrade. Composites using biodegradable polymers synthesized by polycondensation of glycerol and diacids, i.e., poly(glycerol succinate), PGSu, poly(glycerol maleate), PGM, and poly(glycerol maleate-co-succinate), PGMSu, reinforced with cellulose nanocrystals (CNC) were used as adhesives for Angelim (Vatairea heteroptera Ducke). CNC were added at 0, 5, 10 and 20 wt% to the glycerol-derived polymers in order to evaluate their effect on mechanical properties. Polymers and composites were analyzed by differential scanning calorimetry (DSC), thermogravimetric analysis (TGA) and Fourier transform infrared spectroscopy (FTIR). Adhesive joints were prepared using the synthesized glycerol-based polymers, and poly(vinyl acetate), PVAc, for comparison purposes. Thermal analyses indicated that most of the glycerol-based polymers tested are stable up to 260 °C while adhesion tests indicated that adhesives containing CNC showed superior shear strength as compared to pristine polymers and PVAc. These results suggest that the addition of cellulose nanocrystals (CNC) is a viable approach to tailor the mechanical and adhesive properties.
•Biodegradable adhesives are a new generation of adhesives with tailored adhesion and degradation.•Cellulose nanocrystals (CNC) are widely used due to their aspect ratio, crystallinity, mechanical properties and biodegradability.•The combination of glycerol polymers with CNC improves mechanical properties and controls degradation time to produce tailor-made adhesives.•These adhesives can be a viable alternative to using larger amounts of glycerol and adding value to a by-product of the biodiesel production market.
This article considers the problem of multi-robot coverage control, where a group of robots has to spread out over an environment to provide coverage. We propose a new approach for a group of robots ...carrying out this collaborative task that will adapt online to performance variations among the robots. Two types of performance variations are considered: variations in sensing performance (e.g. differences in sensor types, calibration, or noise), and variations in actuation (e.g. differences in terrain, vehicle types, or lossy motors). The robots have no prior knowledge of the relative strengths of their performance compared to the others in the team. We present an algorithm that learns the relative performance variations among the robots online, in a distributed fashion, and automatically compensates by assigning the weak robots a smaller portion of the environment and the strong robots a larger portion. Using a Lyapunov-type proof, we show that the robots converge to a locally optimal coverage configuration. The algorithm is also demonstrated in both MATLAB simulations and experiments with Pololu m3pi ground robots.
Biodegradable, renewable, and environmentally friendly glycerol-based wood adhesives were synthesized through polycondensation reaction between dicarboxylic acids (sebacic and citric acid) and ...glycerol using different molar ratios, i.e. poly(glycerol sebacate) - PGS, poly(glycerol citrate-co-sebacate) - PGCS, and poly(glycerol citrate) - PGC. Thermal properties of the synthesized polymers were evaluated after cross-linking. Results showed that thermal stability was influenced by polymer molecular structure, being lower for PGC due to the presence of quaternary carbons of citric acid. Differential scanning calorimetry analyses showed an intermediate glass transition for the copolymer in comparison with homopolymers. Tensile shear strength tests showed that the presence of citric acid in the polymer improves adhesion and reduces adhesive flexibility, contrary to what happens to polymers with sebacic acid. This behavior was also proved through morphological analyses of the fracture surface. Adhesives with tailor-made properties were produced from glycerol, opening up new revenues for a by-product of the biodiesel production chain.
Fresh produce have a more limited shelf life than processed ones. Their sensory attributes such as appearance and surface texture are important features in consumer perception and liking. The ...decomposition of fresh produce, which is caused by enzymes, chemical reactions, and microbial infections, often caused by Colletotrichum species, is inevitable. However, it can be slowed down. Several materials have been developed for this purpose, with an emphasis on active coatings using nanomaterials. In this study, the protective effects of a zein coating containing chitosan nanowhiskers (CSW) for the maintenance of fruit quality were investigated using guava (Psidium guajava L.) as a model fruit. CSW were previously characterized, and their antifungal effects against distinct Colletotrichum species (Colletotrichum asianum, Colletotrichum tropicale, Colletotrichum gloeosporioides, and Colletotrichum brevisporum) were proven. Coatings were characterized by thermogravimetric analysis, optical profilometry, and mechanical properties. Total soluble solids, pH, mass loss, and visual inspection of uncoated and coated guava fruits were also verified during 9 days. Results show that CSW length and aspect ratio decreased for longer extraction times. A similar behavior was found for x‐ray diffraction in which peak intensity decreases under the same conditions. CSW degradation (ca. 250–400°C) also depends on extraction time in which more crystalline whiskers are the most thermally stable ones. The addition of CSW did not significantly (p < 0.05) modify the homogeneity and continuity of coating but prevented microbial growth assuring fruit quality during storage. In summary, coatings protected guava fruits from post‐harvest spoilage while preserving quality and extending shelf life.
Practical Application
Fresh foods such as fruits and vegetables have a more limited shelf life than processed ones.
Sub-GHz communication provides long-range coverage with low power consumption and reduced deployment cost. LoRa (Long-Range) has emerged, among existing LPWAN (Low Power Wide Area Networks) ...technologies, as a promising physical layer alternative to provide ubiquitous connectivity to outdoor IoT devices. LoRa modulation technology supports adapting transmissions based on parameters such as carrier frequency, channel bandwidth, spreading factor, and code rate. In this paper, we propose SlidingChange, a novel cognitive mechanism to support the dynamic analysis and adjustment of LoRa network performance parameters. The proposed mechanism uses a sliding window to smooth out short-term variations and reduce unnecessary network re-configurations. To validate our proposal, we conducted an experimental study to evaluate the performance concerning the Signal-to-Noise Ratio (SNR) parameter of our SlidingChange against InstantChange, an intuitive mechanism that considers immediate performance measurements (parameters) for re-configuring the network. The SlidingChange is compared with LR-ADR too, a state-of-the-art-related technique based on simple linear regression. The experimental results obtained from a testbed scenario demonstrated that the InstanChange mechanism improved the SNR by 4.6%. When using the SlidingChange mechanism, the SNR was around 37%, while the network reconfiguration rate was reduced by approximately 16%.
In this work, poly(vinyl alcohol)chitosan (PVA/CS) nanofibers were produced by solution blow spinning (SBS). The influence of chitosan addition on solution viscosity as well as on thermal and ...morphological properties of PVA/CS nanofibers were analyzed. A green production route was used using distilled water as solvent without crosslinking agents. Spun fibers were characterized by scanning electron microscopy (SEM), thermogravimetric analysis (TGA), differention scanning calorimetry (DSC), Fourier transform infrared (FTIR), porosity, water uptake and swelling behavior.The greater the amount of CS in the PVA solutions, the higher the viscosity of the spinning solutions, hindering the nanofibers formation. PVA/CS nanofiber mats produced by SBS presented a randomly interconnected and highly porous structure, with diameters ranging from 251 to 377 nm. An increase in the thermal stability and a reduction in both water uptake and swelling behavior of the hybrid nanofibers were observed with the addition of CS.
An adult male free-living yellow armadillo (Euphractus sexcinctus) was found by hunters and referred for clinical evaluation because of a tumour-like lesion on the carapace. The animal was lethargic ...and weak with severe dehydration, enophthalmos and cachexia, and was euthanized because of its very poor clinical condition. Necropsy revealed a whitish, exophytic, irregular and moist mass (7 × 6.5 × 1.5 cm) in the caudal third of the carapace. On cut section, the mass was hard, compact, irregular and whitish. Histopathology revealed a densely cellular, expansive, poorly delimited neoplasm composed of malignant mesenchymal cells arranged in islands and cords, interspersed by numerous areas of irregularly mineralized osteoid matrix. Neoplastic cells were intensely immunolabelled for vimentin. The diagnosis of a high-grade osteosarcoma of osteoblastic subtype was based on the clinical, gross, histopathological and immunohistochemical findings. This first report of an osteosarcoma in an armadillo expands the list of armadillo diseases and will assist the management of these animals by veterinarians.
Vigna unguiculata, one of the most important legumes, mainly in underdeveloped countries, is susceptible to post-harvest losses in storage by Callosobruchus maculatus (Fabricius, 1775) (Coleoptera: ...Chrysomelidae). The work evaluated the toxicity, inhibition of oviposition, instantaneous rate of population growth (r
) and the development of fumigated C. maculatus with the essential oil of Vanillosmopsis arborea and its major constituent, α-bisabolol. The experimental units consisted of 0.8 L flasks treated with concentrations of 1.2-11.2 μL L
of the essential oil of V. arborea or its major constituent applied to disks of filter paper. α-Bisabolol was quantified as 409.33 mL L
of the essential oil. The development rate of C. maculatus was evaluated by daily adult counts. Oviposition was evaluated at lethal concentrations (LC
, LC
, LC
and LC
). The LC
and LC
of the essential oil of V. arborea and α-bisabolol were 5.23 and 12.97 μL L
of air and 2.47 and 8.82 μL L
of air, respectively. At some concentrations, the α-bisabolol was more toxic to males than to females of the insect. Increased concentrations of the essential oil reduced the r
, rate of development, oviposition, and number of eggs of C. maculatus and therefore have potential for pest control.
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