Modeling and Simulation of Janus-like Nanoparticles Formation by Solid-Gas Exothermic Reactions

Theoretical model for the simulation of synthesis of Janus-like particles (JP) consisting two different phases using the Carbon Combustion Synthesis of Oxides (CCSO) is presented. The model includes the variation of sample initial porosity, carbon concentration and oxygen flow rate used to predict the formation of JP features. The two temperature (2T) combustion model of chemically active submicron-dispersed mixture of two phases including ferroelectric and ferromagnetic was implemented and assessed by using the experimentally estimated activation energy of 112±3.3 kJ/mol and combustion temperature. The experimental values allowed to account the thermal and concentration expansion effect along with the dispersion by the slip-jump simulation for high Knudsen numbers. The model predicted that the smaller initial porosity of the combustion media creates higher formation rate of Janus-like particles. The simulation of slippage and jumps of the gas temperature allowed the scale-bridging between macro- and micro- structures.

Thermogravimetric Analysis (TGA) of Graphene Materials: Effect of Particle Size of Graphene, Graphene Oxide and Graphite on Thermal Parameters

Thermogravimetric analysis (TGA) has been recognized as a simple and reliable analytical tool for characterization of industrially manufactured graphene powders. Thermal properties of graphene are dependent on many parameters such as particle size, number of layers, defects and presence of oxygen groups to improve the reliability of this method for quality control of graphene materials, therefore it is important to explore the influence of these parameters. This paper presents a comprehensive TGA study to determine the influence of different particle size of the three key materials including graphene, graphene oxide and graphite on their thermal parameters such as carbon decomposition range and its temperature of maximum mass change rate (Tmax). Results showed that Tmax values derived from the TGA-DTG carbon combustion peaks of these materials increasing from GO (558–616 °C), to graphene (659–713 °C) and followed by graphite (841–949 °C) The Tmax values derived from their respective DTG carbon combustion peaks increased as their particle size increased (28.6–120.2 µm for GO, 7.6–73.4 for graphene and 24.2–148.8 µm for graphite). The linear relationship between the Tmax values and the particle size of graphene and their key impurities (graphite and GO) confirmed in this study endows the use of TGA technique with more confidence to evaluate bulk graphene-related materials (GRMs) at low-cost, rapid, reliable and simple diagnostic tool for improved quality control of industrially manufactured GRMs including detection of “fake” graphene.

Combustion of torrefied pellets of furniture work dusts as blends with lignite

In this study, torrefaction of pellets formed from furniture work dusts collected as a part of space cleaning actions in the industry have been examined. Burning behaviour of torrefied dusts and lignite blends was studied. Torrefaction experiments were done under nitrogen atmosphere for one hour at temperatures of 220, 260 and 300°C which corresponded to light, mild and severe torrefaction, respectively. Combustion of blend pellets prepared by adding lignite in specific ratios to powders of torrefied pellets was carried out at 700°C initial temperature using a vertical furnace system through which air was flowing in natural convection. Ignition times of blend pellets were affected from volatile matter and moisture contents. Volatile matter combustion rates were lower than those of raw waste and accordingly, combustion times were higher. However, no relation between volatile matter combustion rates and times was observed. Blending raw or torrefied furniture work dusts with lignite have significantly influenced volatile matter and carbon combustion periods. There was no relation between carbon combustion rates and times. It was concluded that blend pellets of mild or severe torrefaction products of furniture work dusts and lignite behaved similarly to lignite during combustion.

Mapping the Mitochondrial Regulation of Epigenetic Modifications in Association With Carcinogenic and Noncarcinogenic Polycyclic Aromatic Hydrocarbon Exposure

Polycyclic aromatic hydrocarbons (PAHs) refer to a ubiquitous group of anthropogenic air pollutants that are generated through incomplete carbon combustion. Although the immunotoxic nature of PAHs has been previously reported, the underlying molecular mechanisms of this effect are not fully understood. In the present study, we investigated the mitochondrial-mediated epigenetic regulation of 2 PAHs, carcinogenic (benzo[a]pyrene; BaP) and noncarcinogenic (anthracene [ANT]), in peripheral lymphocytes. While ANT exposure triggered mitochondrial oxidative damage, no appreciable epigenetic modifications were observed. On the other hand, exposure to BaP perturbed the mitochondrial redox machinery and initiated cascade of epigenetic modifications. Cells exposed to BaP showed prominent changes in the expression of mitochondrial microRNAs (miR-24, miR-34a, miR-150, and miR-155) and their respective gene targets (NF-κβ, MYC, and p53). The exposure of BaP also caused significant alterations in the expression of epigenetic modifiers (DNMT1, HDAC1, HDAC7, KDM3a, EZH2, and P300) and hypomethylation within nuclear and mitochondrial DNA. This further induced methylation of histone tails, which play a crucial role in the regulation of chromatin structure. Overall, our study provides novel mechanistic insights into the mitochondrial regulation of epigenetic modifications in association with PAH-induced immunotoxicity.

Carbon emissions from wildfires in larch forest ecosystems of Northeast Siberia

<p>The boreal forest is one of the largest terrestrial carbon reservoirs on Earth and accounts for approximately 30% of the world’s forest cover. The boreal carbon balance is thus of global significance. Wildfires affect the boreal carbon balance, releasing large amounts of carbon into the atmosphere when soil organic layers and aboveground biomass are combusted. The boreal forest is warming faster than the global average. These higher temperatures lead to increases in the frequency and severity of wildfire disturbance in boreal regions.</p><p>Significant progress has been made in quantifying carbon combustion in North American boreal forests, yet few measurements have been conducted in the larch dominated boreal forests of Northeast Siberia. Deciduous needleleaf larch forest growing on continuous permafrost is a unique ecosystem of Siberia. Although these larch forests cover approximately 20% of the boreal biome, the consequences of intensifying fire regimes on the carbon stocks and vegetation dynamics of these ecosystems remain poorly understood.</p><p>We conducted a field campaign in larch forests around Yakutsk, Northeast Siberia, during the summer of 2019 with the goal of filling parts of these knowledge and data gaps by collecting ground measurements of carbon combustion from two large fire events in 2017 and 2018. During this campaign, we sampled 42 burned sites in two fire scars that cover gradients of fire severity, vegetation composition and landscape position. Within these sites, we performed a wide range of measurements to quantify aboveground and belowground carbon emissions, constrained by data from 12 unburned sites. We also assessed post-fire recovery and active layer deepening. We investigated major drivers of pre-fire carbon stocks and subsequent combustion at the site level. Our results will reduce uncertainties in larger scale estimates of carbon emissions from Siberian fires which is in turn essential for assessing the implications of the climate-induced intensification of fire regimes for the global carbon cycle.</p>