This study aimed to develop new biobased materials containing plasticized cellulose acetate (CA) by Fused Filament Fabrication (FFF). We investigated the influence of CA on the ...viscoelastic/dielectric properties and the influence of 3D printing on the dielectric properties of the polymer blends. A microstructural analysis showed that the blends had a strong heterogeneous morphology, as the two phases formed a fibrillar and lamellar structure. CA strongly increased the blend viscosity at 175 °C, multiplying by 100 times the complex viscosity between neat PLA and the blend containing 40% of CA by weight (CA-40). The addition of CA to the blends increased the dielectric constant (ε') and dielectric loss (ε''), as well as the alternative current electrical conductivity (σAC). The dielectric constant of CA (ε'CA) was proportional to its percentage in the blend, showing a behavior analogous to a rule of mixture. Moreover, the activation energy of the electrical conductivity (σDC) measured at T > 124 °C decreased with increasing CA content and was associated with the enhancement of the ionic conductivity provided by the CA and its plasticizer. A decrease in the α-relaxation temperature and the associated activation energy of the PLA was also linked to the presence of the CA plasticizer. Finally, 3D printing greatly decreased both ε', ε'' and σAC due to the internal voids induced by the 3D printing process. The porosity was measured at 12% for neat PLA and between 20% and 25% for the blends. These results showed the advantage provided by FFF technology in the production of PLA:CA blends with controlled dielectric properties, thereby favoring the use of these new materials in key dielectric areas.
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•PLA:CA blends with 40% CA were successfully obtained by 3D printing.•CA improved the mechanical properties of PLA in its rubbery state.•CA influenced the dielectric properties of the blend due to its polar nature.•The CA plasticizer reduced the relaxation phenomenon of PLA.•3D-printed PLA:CA blends were suitable for electrical insulation applications.
Under natural conditions, plants experience external mechanical stresses such as wind and touch that impact their growth. A remarkable feature of this mechanically induced growth response is that it ...may occur at a distance from the stimulation site, suggesting the existence of a signal propagating through the plant. In this study, we investigated the electrical response of poplar trees to a transient controlled bending stimulation of the stem that mimics the mechanical effect of wind. Stem bending was found to cause an electrical response that we called “gradual” potential, similar in shape to an action potential. However, this signal can be distinguished from the well‐known plant action potential by its propagation up to 20 cm along the stem and its strong dumping in velocity and amplitude. Two hypotheses regarding the mode of propagation of the “gradual” potential are discussed.
In this study, we used the phenotype simulation package naturalgwas to test the performance of Zhao's Random Forest method in comparison to an uncorrected Random Forest test, latent factor mixed ...models (LFMM), genome‐wide efficient mixed models (GEMMA), and confounder adjusted linear regression (CATE). We created 400 sets of phenotypes, corresponding to five effect sizes and two, five, 15, or 30 causal loci, simulated from two empirical data sets containing SNPs from Striped Bass representing three and 13 populations. All association methods were evaluated for their ability to detect genotype–phenotype associations based on power, false discovery rates, and number of false positives. Genomic inflation was highest for uncorrected Random Forest and LFMM tests and lowest for Gemma and Zhao's Random Forest. All association tests had similar power to detect causal loci, and Zhao's Random Forest had the lowest false discovery rate in all scenarios. To measure the performance of association tests in small data sets with few loci surrounding a causal gene we also ran analyses again after removing causal loci from each data set. All association tests were only able to find true positives, defined as loci located within 30 kbp of a causal locus, in 3%–18% of simulations. In contrast, at least one false positive was found in 17%–44% of simulations. Zhao's Random Forest again identified the fewest false positives of all association tests studied. The ability to test the power of association tests for individual empirical data sets can be an extremely useful first step when designing a GWAS study.
Materials for low-permittivity and electrical insulation applications need to be re-engineered to achieve sustainable development. To address this challenge, the proposed study focused on the ...dielectric and mechanical optimization of 3D-printed cellulose-based composites for electrical insulation applications. Two different fillers, microcrystalline cellulose (MCC) and nanocrystalline cellulose (NCC), were used to create biocomposites and bionanocomposites, respectively, blended into a polylactic acid (PLA) matrix. The effects of infill ratio, printing temperature, and filler content on dielectric and mechanical properties were measured using an incomplete L9 (3^3) factorial design. The findings showed that the infill ratio was the most significant factor influencing the properties tested, directly attributable to the increase in material availability for polarization and mechanical performance. The second most influential factor was the filler content, increasing the polarity of the tested composites and decreasing the toughness of the biocomposites and bionanocomposites. Finally, printing temperature had no significant effect. Results for the biocomposites at a 50% infill ratio, 200 °C printing temperature, and a weight content of MCC of 15% gave a 60% higher tensile-mode stiffness than neat PLA printed under the same conditions, while exhibiting lower dielectric properties than neat PLA printed with a 100% infill ratio. These results pave the way for new lightweight materials for electrical insulation.
Summary
Damage can be signalled by extracellular ATP (eATP) using plasma membrane (PM) receptors to effect cytosolic free calcium ion (Ca2+cyt) increase as a second messenger. The downstream PM Ca2+ ...channels remain enigmatic. Here, the Arabidopsis thaliana Ca2+ channel subunit CYCLIC NUCLEOTIDE‐GATED CHANNEL2 (CNGC2) was identified as a critical component linking eATP receptors to downstream Ca2+cyt signalling in roots.
Extracellular ATP‐induced changes in single epidermal cell PM voltage and conductance were measured electrophysiologically, changes in root Ca2+cyt were measured with aequorin, and root transcriptional changes were determined by quantitative real‐time PCR. Two cngc2 loss‐of‐function mutants were used: cngc2‐3 and defence not death1 (which expresses cytosolic aequorin).
Extracellular ATP‐induced transient depolarization of Arabidopsis root elongation zone epidermal PM voltage was Ca2+ dependent, requiring CNGC2 but not CNGC4 (its channel co‐subunit in immunity signalling). Activation of PM Ca2+ influx currents also required CNGC2. The eATP‐induced Ca2+cyt increase and transcriptional response in cngc2 roots were significantly impaired.
CYCLIC NUCLEOTIDE‐GATED CHANNEL2 is required for eATP‐induced epidermal Ca2+ influx, causing depolarization leading to Ca2+cyt increase and damage‐related transcriptional response.
Due to strict environmental regulations, the construction sector has observed extensive use of supplementary cementitious materials (SCMs) in recent years. As a result, new alternative SCMs have ...emerged and research in this particular area has considerably developed. Although a large number of research devoted to cement-based materials blended with SCMs has been conducted, there continue to be debates about their characteristics, effects on the hydration, and the durability of cement pastes, mortars and concrete. Therefore, this review summarized the most widespread methods for SCMs characterization, major characteristics, and the role of each of the five widely used SCMs including coal fly ash, silica fume, ground granulated blast furnace slag, limestone powder, and metakaolin in the hydration and durability of cement-based materials. Ultimately, their environmental and economic advantages were also reviewed. A huge variation in the SCMs physical and chemical characteristics has been highlighted as the major concern when it comes to the establishment of standards and characterization methods. The literature has also shown that the hydration, compressive strength and durability of cement-based materials blended with SCMs typically depend on the replacement ratios, fineness and synergic effect of the SCMs’ reactivity mechanisms. Owing to their high specific surface area and pozzolanic activity, partial cement replacement with a suitable amount of silica fume and metakaolin considerably accelerates the hydration and increases the heat of hydration of cement-based materials. Besides, limestone powder and ground granulated blast slag reportedly present better environmental and economic benefits compared to metakaolin and silica fume.
Renewable dielectric materials have attracted the attention of industries and stakeholders, but such materials possess limited properties. This research focused on studying polylactic acid ...(PLA)/cellulose acetate (CA) blends produced by 3D printing to facilitate their integration into the electrical insulation field. The dielectric findings showed that a blend containing 40% of CA by weight had a dielectric constant of 2.9 and an electrical conductivity of 1.26 × 10−11 S·cm−1 at 100 Hz and 20 °C while exhibiting better mechanical rigidity in the rubbery state than neat PLA. In addition, it was possible to increase the electrical insulating effect by reducing the infill ratio at the cost of reduced mechanical properties. The differential scanning calorimetry, broadband dielectric spectroscopy, and dynamic mechanical analysis results showed that the PLA plasticizer reduced the energy required for PLA relaxations. These preliminary results demonstrated the benefits of using a combination of PLA, CA, and 3D printing for electrical insulation applications.
The colonization of the atmosphere by land plants was a major evolutionary step. The mechanisms that allow for vertical growth through air and the establishment and control of a stable erect habit ...are just starting to be understood. A key mechanism was found to be continuous posture control to counterbalance the mechanical and developmental challenges of maintaining a growing upright structure. An interdisciplinary systems biology approach was invaluable in understanding the underlying principles and in designing pertinent experiments. Since this discovery previously held views of gravitropic perception had to be reexamined and this has led to the description of proprioception in plants. In this review, we take a purposefully pedagogical approach to present the dynamics involved from the cellular to whole-plant level. We show how the textbook model of how plants sense gravitational force has been replaced by a model of position sensing, a clinometer mechanism that involves both passive avalanches and active motion of statoliths, granular starch-filled plastids, in statocytes. Moreover, there is a transmission of information between statocytes and other specialized cells that sense the degree of organ curvature and reset asymmetric growth to straighten and realign the structure. We give an overview of how plants have used the interplay of active posture control and elastic sagging to generate a whole range of spatial displays during their life cycles. Finally, a position-integrating mechanism has been discovered that prevents directional plant growth from being disrupted by wind-induced oscillations.
To bring surface hydrophobicity to thermoplastic starch (TPS) materials for food packaging, fatty acid starch esters (FASE), specifically starch tri-laurate, were incorporated into TPS formulations. ...A total of three different ratios of FASE (2%, 5% and 10%) were added to the TPS formulation to evaluate the influence of FASE onto physico-chemical properties of TPS/FASE blends, i.e., surface hydrophobicity, dynamic vapor sorption (DVS), and tensile behaviors. Blending TPS with FASE leads to more hydrophobic materials, whatever the FASE ratio, with initially measured contact angles ranging from 90° for the 2%-FASE blend to 99° for the 10%-blend. FT-IR study of the material surface and inner core shows that FASE is mainly located at the material surface, justifying the increase of material surface hydrophobicity. Despite this surface hydrophobicity, blending TPS with FASE seems not to affect blend vapor sorption behavior. From a mechanical behavior perspective, the variability of tensile properties of starch-based materials with humidity rate is slightly reduced with increasing FASE ratio (a decrease of maximal stress of 10–30% was observed for FASE ratio 2% and 10%), leading to more ductile materials.
This study describes the elaboration and characterization of plasticized starch composites based on lignocellulosic fibers. The transformation of native to plasticized starch (TPS) and the ...preparation of TPS blends were performed with a new lab-scale mixer based on an original concept. Firstly, the morphology and chemical composition of flax shives were analyzed to better understand the intrinsic properties of these natural fillers. Then, the impact of the processing parameters (temperature, speed screw) on the quality and the structural properties of plasticized starch were examined by SEM and DRX. After that, we focused on the elaboration of various formulations based on plasticized starch matrix by varying TPS formulation and filler content (from 10 to 30%). The viscoelastic and rheological properties of TPS/flax blends have been analyzed by TGA, SEM, and DMTA.
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