The Histone Chaperone HIRA Is a Positive Regulator of Seed Germination

Histone chaperones regulate the flow and dynamics of histone variants and ensure their assembly into nucleosomal structures, thereby contributing to the repertoire of histone variants in specialized cells or tissues. To date, not much is known on the distribution of histone variants and their modifications in the dry seed embryo. Here, we bring evidence that genes encoding the replacement histone variant H3.3 are expressed in Arabidopsis dry seeds and that embryo chromatin is characterized by a low H3.1/H3.3 ratio. Loss of HISTONE REGULATOR A (HIRA), a histone chaperone responsible for H3.3 deposition, reduces cellular H3 levels and increases chromatin accessibility in dry seeds. These molecular differences are accompanied by increased seed dormancy in hira-1 mutant seeds. The loss of HIRA negatively affects seed germination even in the absence of HISTONE MONOUBIQUITINATION 1 or TRANSCRIPTION ELONGATION FACTOR II S, known to be required for seed dormancy. Finally, hira-1 mutant seeds show lower germination efficiency when aged under controlled deterioration conditions or when facing unfavorable environmental conditions such as high salinity. Altogether, our results reveal a dependency of dry seed chromatin organization on the replication-independent histone deposition pathway and show that HIRA contributes to modulating seed dormancy and vigor.     

In situ study of nucleation and growth of the irregular α-Al/β-Al5FeSi eutectic by 3-D synchrotron X-ray microtomography

In order to better understand the formation of β-Al₅FeSi intermetallic plates during solidification of Al–Si casting alloys, an Al–8% Si–4% Cu–0.8% Fe alloy has been studied by in situ microtomography using high-energy X-rays in the synchrotron. After formation of the aluminium dendrites, the β phase forms as an irregular eutectic together with eutectic α-Al. Only four plates were nucleated in the sample, and all nucleated in the very early stage of the eutectic reaction and subsequently developed into complex connected three-dimensional plates. The plates display very rapid lateral growth and slow thickening, which, together with the observation of imprints of dendrites and ridges in the plates, suggest a very weakly coupled eutectic.     

Two-dimensional (2D) and three-dimensional (3D) analyses of plasma-sprayed alumina microstructures for finite-element simulation of Young’s modulus

Thermally sprayed ceramic coatings such as plasma-sprayed alumina exhibit a composite microstructure actually due to the presence of defects such as pores, inter-lamellar and intra-lamellar cracks. These second phase-typed features influence the mechanical behaviour of the coating dramatically. In this study, a microstructure simulation of plasma-sprayed alumina was developed for the optimizing of component properties such as electrical tool used in the oil industry. This approach consisted of a finite-element analysis of mechanical properties from simulated microstructures. Several composite microstructures were tested from air plasma spraying of alumina. Various degrees of porosity and cracks could be obtained from different spraying conditions. Every composite microstructure was studied using a quantitative image analysis of scanning electron microscope (SEM) cross-sections. A finite-element model based on the actual microstructure was developed. First, two-dimensional (2D) finite elements meshes were created from SEM images of microstructures. Then, in order to have a realistic representation of the three-dimensional (3D) microstructure, pictures were obtained using X-ray microtomography. Volume tetrahedral grids were generated to simulate the properties of alumina coatings. This work studies the contribution of every part of the alumina coating to the final properties and shows potentials and limitations of the 2D and 3D computational approach.     

Influence of initiator on the curing of unsaturated polyester resin at 100 °C

Sheet molding compound (SMC) parts are fiber‐reinforced unsaturated polyester (UP) composites molded at 140–170 °C under a pressure of 60–100 bar. For economic and ecological reasons, the aim of this research project is to develop new SMC formulations to modify the molding conditions. For this, SMC formulations were modified and optimized to decrease the molding temperature to 100 °C. The strategy was to change the catalytic system (peroxides) in order to obtain highly reactive formulations at 100 °C. First, the temperatures of initiation of the reaction were determined by rheological and DSC measurements for each peroxide. Second, the UP resin crosslinking kinetics were measured for the various peroxides during an isothermal curing at 100 °C. The results obtained with the three experimental methods are compared and discussed. Finally, the laboratory analyses were validated by SMC molding trials. © 2019 Society of Chemical Industry     

Consolidation by spark plasma sintering of polyimide and polyetheretherketone

This article presents two high‐temperature thermoplastic powders which were sintered by spark plasma sintering in order to get homogeneous mechanical properties. Dense polyimide (PI) and polyetheretherketone (PEEK) specimens were obtained at temperatures as low as 320°C for PI and 200°C for PEEK, respectively. Relative densities higher than 99% were reached for both materials. In order to characterize their properties, in situ measurements with compression and hardness tests were carried out on sintered samples. This method allowed to obtain polymeric materials with improved mechanical properties. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40783.     

A Spectroscopic Method for Hydroxyl Value Determination of Polyols

A relatively simple method is described for routine determination of hydroxyl values for a wide range of hydroxyl containing compounds including soybean oil polyols, polyols derived from soy meal, polyether polyols and ethylene glycol as well as their blends. This method is based on reacting the hydroxyl compound with hexamethyldisilazane (HMDS) and determining the FTIR peak area of the silylated product at 1,251 cm^?1. The method is simple, accurate and reproducible. It is not limited to a specific family of polyol compounds. It does not require any special equipment, hazardous chemicals and can be carried out by non‐technical staff as a rapid and convenient method for quantitative determination of hydroxyl values. An excellent linear correlation was obtained between this spectroscopic method and conventional titration methods for different polyols over a wide range of hydroxyl values. Furthermore, unlike the titration methods the current method is not affected by the presence of acid, base or small amounts of water in the test sample.     

Application of synchrotron X-ray radiography to the study of dendritic equiaxed microstructure formation in Al–Cu alloys

The phenomena involved during equiaxed growth, which is the most common growth morphology in metal casting, are dynamic. Therefore, in situ investigation is necessary to fully analyse the microstructure formation. Synchrotron X-ray radiography has become a major tool for in situ characterization of solidification in metallic systems. This paper reports on dedicated equiaxed solidification experiments carried out at the European Synchrotron Radiation Facility (ESRF) in Grenoble-France on Al–10 wt.% Cu alloy. The analysis is based on the recorded images obtained through absorption radiography. Equiaxed growth is achieved in nearly isothermal conditions and observed continuously in real time from the early stages of solidification to the final state. The evolution of the dendrite arm lengths and the corresponding growth rates are analysed for two couples of grains in relation with their environment. This analysis suggests that the solutal interaction is dominant between equiaxed grains.     

The synthesis of multilayer graphene materials by the fluorination of carbon nanodiscs/nanocones

Multilayer carbonaceous nanomaterial has been synthesized using a two-step process: carbon nanodiscs/nanocones were fluorinated using either the direct reaction with pure F₂ gas or the thermal decomposition of solid fluorinating agent (TbF₄). Then the fluorinated parts were removed by treatment at 600 °C in air. When the fluorine atoms are homogenously dispersed, using fluorination by TbF₄, thinning due to thermal defluorination results in multilayer materials with 7–10 nm of thickness and 400–500 nm of width. Such resulting materials and the fluorinated precursors have been characterized by solid state NMR, TGA, XRD, SEM, TEM, AFM and Raman spectroscopy.     

Nucleation of polystyrene latex particles in the presence of gamma-methacryloxypropyltrimethoxysilane: functionalized silica particles

Silica/polystyrene nanocomposite particles with different morphologies were synthesized through emulsion polymerization of styrene in the presence of silica particles previously modified by gamma-methacryloxypropyltrimethoxysilane (MPS). Grafting of the silane molecule was performed by direct addition of MPS to the aqueous silica suspension in the presence of an anionic surfactant under basic conditions. The MPS grafting density on the silica surface was determined using the depletion method and plotted against the initial MPS concentration. The influence of the MPS grafting density, the silica particles size and concentration and the nature of the surfactant on the polymerization kinetics and the particles morphology was investigated. When the polymerization was performed in the presence of an anionic surfactant, transmission electron microscopy images showed the formation of polymer spheres around silica for MPS grafting densities lower than typically 1 micromole x m(-2) while the conversion versus time curves indicated a strong acceleration effect under such conditions. In contrast, polymerizations performed in the presence of a larger amount of MPS moieties or in the presence of a non ionic emulsifier resulted in the formation of "excentered" core-shell morphologies and lower polymerization rates. The paper identifies the parameters that allow to control particles morphology and polymerization kinetics and describes the mechanism of formation of the nanocomposite colloids.