Summary
Endosymbiosis of bacteria by eukaryotes is a defining feature of cellular evolution. In addition to well‐known bacterial origins for mitochondria and chloroplasts, multiple origins of ...bacterial endosymbiosis are known within the cells of diverse animals, plants and fungi. Early‐diverging lineages of terrestrial fungi harbor endosymbiotic bacteria belonging to the Burkholderiaceae. We sequenced the metagenome of the soil‐inhabiting fungus Mortierella elongata and assembled the complete circular chromosome of its endosymbiont, Mycoavidus cysteinexigens, which we place within a lineage of endofungal symbionts that are sister clade to Burkholderia. The genome of M. elongata strain AG77 features a core set of primary metabolic pathways for degradation of simple carbohydrates and lipid biosynthesis, while the M. cysteinexigens (AG77) genome is reduced in size and function. Experiments using antibiotics to cure the endobacterium from the host demonstrate that the fungal host metabolism is highly modulated by presence/absence of M. cysteinexigens. Independent comparative phylogenomic analyses of fungal and bacterial genomes are consistent with an ancient origin for M. elongata – M. cysteinexigens symbiosis, most likely over 350 million years ago and concomitant with the terrestrialization of Earth and diversification of land fungi and plants.
Chfr is a checkpoint protein that plays an important function in cell cycle progression and tumor suppression, although its exact role and regulation are unclear. Previous studies have utilized ...overexpression of Chfr to determine the signaling pathway of this protein in vivo. In this study, we demonstrate, by using three different antibodies against Chfr, that the endogenous and highly overexpressed ectopic Chfr protein is localized and regulated differently in cells. Endogenous and lowly expressed ectopic Chfr are cytoplasmic and localize to the spindle during mitosis. Higher expression of ectopic Chfr correlates with a shift in the localization of this protein to the nucleus/PML bodies, and with a block of cell proliferation. In addition, endogenous and lowly expressed ectopic Chfr is stable throughout the cell cycle, whereas when highly expressed, ectopic Chfr is actively degraded during S-G2/M phases in an autoubiquitination and proteasome-dependent manner. A two-hybrid screen identified TCTP as a possible Chfr-interacting partner. Biochemical analysis with the endogenous proteins confirmed this interaction and identified beta-tubulin as an additional partner for Chfr, supporting the mitotic spindle localization of Chfr. The Chfr-TCTP interaction was stable throughout the cell cycle, but it could be diminished by the complete depolymerization of the microtubules, providing a possible mechanism where Chfr could be the sensor that detects microtubule disruption and then activates the prophase checkpoint.
An analytical approach of transient heat conduction in two-layered material, of finite depth, with an imperfect thermal contact, subjected to a moving gaussian laser beam was developed.
The method ...consists of deriving the solution of the homogeneous part of the heat equation by using the well known separation of variables method and expressing the source term in series form. The porous aspect of granular coating layer on substrate was also taken into account earlier in this modelling work. This model has been successfully applied on a practical system; laser cladding of electronic copper tracks on alumina substrates. This analytical model can be used also for estimation of the thermal contact resistance between layers.
A fundamental question in developmental biology is how different cell lineages acquire different cell cycle durations. With its highly stereotypical asymmetric and asynchronous cell divisions, the ...early Caenorhabditis elegans embryo provides an ideal system to study lineage-specific cell cycle timing regulation during development, with high spatio-temporal resolution. The first embryonic division is asymmetric and generates two blastomeres of different sizes (AB>P1) and developmental potentials that divide asynchronously, with the anterior somatic blastomere AB dividing reproducibly two minutes before the posterior germline blastomere P1. The evolutionarily conserved PAR proteins (abnormal embryonic PARtitioning of cytoplasm) regulate all of the asymmetries in the early embryo including cell cycle asynchrony between AB and P1 blastomeres. Here we discuss our current understanding and open questions on the mechanism by which the PAR proteins regulate asynchronous cell divisions in the early C. elegans embryo.
•Polarity PAR proteins regulate the asynchronous cell division of the 2-cell C. elegans embryo.•PAR proteins control mitotic entry and DNA replication.•PAR proteins influence cell cycle timing by regulating the asymmetric localization of cell cycle regulators.
The in-flight oxidation of stainless steel particles in the plasma jet was investigated in this work. Two types of 316L austenitic stainless steel particles were sprayed by a dc plasma gun in ambient ...or controlled atmosphere varying gun parameters and surrounding gases composition. The in-flight collected particles were characterized to establish relationship between spray parameters and particle oxidation behavior. The in-flight particle oxidation mechanisms were then suggested. It was shown that besides diffusion based oxidation, convective oxidation in the particles can occur within the plasma jet core if plasma to particle kinematic viscosities ratio and relative Reynolds number (Re) are superior to 55 and 20, respectively. In these conditions, the oxide formed or oxygen dissolved at the surface of the liquid particle can be swept into its interior forming isolated oxide nodules. Fresh liquid metal is transported from interior towards particle surface. The oxidation rates were estimated to be higher compared to diffusion based oxidation which was found to be the dominant phenomenon in the plasma jet plume in the absence of convective oxidation. Spray parameters leading to higher kinematic viscosities ratio and Re, such as increasing arc current, hydrogen content in the plasma forming gases, or decreasing sprayed particle size range, resulted in enhanced convective oxidation in the plasma core. The diffusion based oxidation of particles in the plasma jet plume can be principally controlled by their size (specific surface area), temperature and velocity (dwell time) and the molar fraction of oxidizing and reducing species in the plasma jet. While investigating the influence of the atmosphere of plasma jet on the in-flight particle oxidation, it was found that the surface area of the oxide nodules and the mass percentage of total oxygen in collected particles followed a parabolic and linear relationship with pO2 in the surrounding atmosphere. Keeping surrounding pO2 at 0.1 and altering N2 and Ar content resulted in higher oxygen content in particles sprayed in Ar rich surrounding whereas no distinct difference in oxide nodules surface area was measured.
The spontaneous formation of organized nanocrystals in semiconductors has
been observed during heteroepitaxial growth and
chemical synthesis. The ability to fabricate size-controlled silicon ...nanocrystals
encapsulated by insulating SiO2 would be of significant interest
to the microelectronics industry. But reproducible manufacture of such crystals
is hampered by the amorphous nature of SiO2 and the differing thermal
expansion coefficients of the two materials. Previous attempts
to fabricate Si nanocrystals failed to achieve control over their shape and
crystallographic orientation, the latter property being important in systems
such as Si quantum dots. Here we report the self-organization of Si nanocrystals
larger than 80 into brick-shaped crystallites oriented along
the 〈111〉 crystallographic direction. The nanocrystals are formed
by the solid-phase crystallization of nanometre-thick layers of amorphous
Si confined between SiO2 layers. The shape and orientation of the
crystallites results in relatively narrow photoluminescence, whereas isotropic
particles produce qualitatively different, broad light emission. Our results
should aid the development of maskless, reproducible Si nanofabrication techniques.
The influence of the substrate surface temperature and oxidation state on the flattening of alumina and stainless steel particles and the morphology of resulting splats were studied in the current ...work. Particles were sprayed by a d.c. plasma gun on polished plain carbon steel and low alloy steel substrates preheated by plasma jet at different temperatures in air or in an oxidation limiting nitrogen shroud system added around substrates.
Extensively fragmented splats of alumina and stainless steel were collected on substrates kept at room temperature. On substrates preheated to 573 (±20) K, the splat morphology of both materials transformed from splashed one to disk-shaped one. Optimal flattening degrees for stainless steel and alumina splats were measured for this substrate temperature, and the former particles exhibited flattening degree of the order of 1.2 times those of alumina. On plain carbon steel substrates, preheated in air at temperatures well above 573 K, the particle flattening degree decreased drastically and collected splats were extensively fragmented with bubbles like holes in them. The splashing and bubble formation in splats on preheated substrate were more dominating for low viscosity and higher Reynolds number stainless steel particles. The splat flattening–splashing and bubble formation were effectively limited by preheating substrates in the nitrogen shroud system. After a detailed characterization of substrate surface oxide layers, formed under different preheating conditions, it was concluded that splat morphology and flattening were only partially affected by the oxide chemical composition and thickness and were principally controlled by the surface roughness (more exactly its topography), induced by the oxidation.
Understanding the combustion of methyl esters is crucial to elucidate kinetic pathways and predict combustion parameters, soot yields, and fuel performance of biodiesel, however most kinetic studies ...of methyl esters have focused on smaller, surrogate model esters. Methyl hexanoate is a larger methyl ester approaching the chain length of methyl esters found in biodiesel and has not received as much research attention as other smaller esters. The purpose of this work is to present the first atmospheric pressure combustion data of methyl hexanoate, CH3CH2CH2CH2CH2COOCH3. Mixtures of 2% methyl hexanoate in O2 and N2 are studied using a plug flow reactor at atmospheric pressure, wall temperatures from 573 to 973 K, residence times from roughly 1-2 s., and fuel equivalence ratios of 1, 1.5, and 2. Exhaust gases are analyzed by a gas chromatograph-mass spectrometer system and species mole fractions are presented. The literature model shows satisfactory agreement with the experimental species profiles and improvements for future mechanistic studies are suggested. In particular, this work proposes new unimolecular decomposition pathways of methyl hexanoate to form methanol or methyl acetate. Furthermore, the experiment detected three unsaturated esters that are direct products of the low temperature oxidation chemistry and it provides more insight into branching ratios for the formation of methyl hexanoate radicals and for the decomposition of hydroperoxyalkyl radicals.
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