Experimental Temperature Research Articles

Characterisation of Fe Distribution in the Liquid-Solid Boundary of Al-Zn-Mg-Si Alloy Using Synchrotron X-ray Fluorescence Microscopy.

Al-Zn-Mg-Si alloy coatings have been developed to inhibit the corrosion of cold-rolled steel sheets by offering galvanic and barrier protection to the substrate steel. It is known that Fe deposited from the steel strip modifies the microstructure of the alloy. We cast samples of Al-Zn-Mg-Si coating alloys containing 0.4 wt% Fe and directionally solidified them using a Bridgman furnace to quantify the effect of this Fe addition between 600 °C and 240 °C. By applying a temperature gradient, growth is encouraged, and by then quenching the sample in coolant, the microstructure may be frozen. These samples were analysed using scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS) to determine the morphological effects of the Fe distribution across the experimental temperature range. However, due to the sub 1 wt% concentration of Fe, synchrotron X-ray fluorescence microscopy (XFM) was applied to quantitatively confirm the Fe distribution. Directionally solidified samples were scanned at 7.05 keV and 18.5 keV using X-ray fluorescence at the Australian Synchrotron using the Maia array detector. It was found that a mass nucleation event of the Fe-based τ6 phase occurred at 495 °C following the nucleation of the primary α-Al phase as a result of a peritectic reaction with remaining liquid.

Multi-Objective Parameter Optimization Strategy of Rheological Instability and Power Dissipation for Molybdenum Alloy Based on Genetic Algorithm

Because of the limited performance of the core material of heat pipe reactor, the cooling effect of nuclear power source is restricted. Molybdenum alloy with excellent comprehensive performance has been a popular core material. To improve the performance of the molybdenum alloy hot forming process, the rheological instability and power dissipation of recrystallized molybdenum alloys are studied by orthogonal arrays L16 with three factors and four levels in this paper. Considering the experimental temperature, strain rate and true strain, the rheological instability and power dissipation are optimized based on a genetic algorithm (GA), with optimal process parameters of recrystallized molybdenum alloys obtained as follows by taking the rheological instability and power dissipation as the objectives. The experimental temperature is 792.424 ℃, the strain rate is 0.01 s-1, the true strain is 0.1N, the rheological instability is 0.23336, and the power dissipation is 0.6832. The rheological instability is increased by 21.79% and the power dissipation is decreased by 64.95% compared with that in the experiment (the experimental temperature is 650 ℃, the strain rate is 0.01 s-1, and the true strain is 0.1N in the experiment with similar parameters in the orthogonal arrays).

Investigating phase changes in cyanide-containing organic compounds with high melting points based on Quantitative Structure-Property Relationship modelling

Cyanide-containing organic compounds exhibit heat-resistant properties due to their high melting points, which can exceed 250 °C. These compounds find widespread applications in various industries. To predict their thermal decomposition temperatures, a straightforward model is introduced in this study. Unlike complex descriptors and computer codes, this model relies on structural parameters specific to cyanide-containing organic compounds. The investigation revealed that certain structural variables significantly influence the onset decomposition temperature. Among these, the number and type of rings play a crucial role. The model was developed and tested using a dataset of 77 experimental thermal decomposition onset temperatures for cyanide-containing organic compounds. For training and test sets comprising 62 and 15 compounds, respectively, the predicted values demonstrated good agreement with experimental data. Specifically, the coefficient of determination (R2) was 0.922 for the training set and 0.897 for the test set. The root mean square deviation (RMSD) and average absolute deviation (AAD) were 14.37 and 17.11 K for the training set, and 11.10 and 13.80 K for the test set. Furthermore, the proposed model outperformed a more complex existing model when applied to 13 cyanide-containing organic compounds. Additionally, this method can be utilized for designing cyanide-containing organic compounds with desired decomposition temperatures.

2D CFD modeling for pyrolysis of a large biomass particle: Effect of L/D ratio, internal convection and shrinkage

A transient 2D kinetic-heat transfer model for the pyrolysis of a large biomass particle, incorporating, primary and secondary reaction kinetics, internal convection and shrinkage in particles was developed and validated with experimental results. The RMS errors between the predicted and experimental temperature and residual mass fraction were estimated to be small - 0.020, 0.017, 0.011, 0.018 and 0.024, 0.022, 0.016, 0.025 at reactor temperatures of 573, 623, 673, 723 K, respectively. The pyrolysis behaviour was explained by the computed spatial distributions of velocity, pressure, temperature and residual mass fraction within the biomass particle. At a high L/D (∼5), two symmetric hot spots were formed near the two axial flat edges after 400 s, which formed a single dumbbell-shaped in the axial central core after 600 s and existed for a long time of 1500 s. It merged into a single spherical hot spot at the centre after a long reaction time. For a low L/D (∼1), however, an elliptical-shaped hot spot formed after 400 s changes to a spherical hot spot at the particle centre after 500 s. Uniformity in temperature inside the particle was attained much earlier at a smaller L/D ratio.

Experimental study on pore structure evolution of thermally treated shales: implications for CO2 storage in underground thermally treated shale horizons

Extracting gas from unconventional shale reservoirs with low permeability is challenging. To overcome this, hydraulic fracturing (HF) is employed. Despite enhancing shale gas production, HF has drawbacks like groundwater pollution and induced earthquakes. Such issues highlight the need for ongoing exploration of novel shale gas extraction methods such as in situ heating through combustion or pyrolysis to mitigate operational and environmental concerns. In this study, thermally immature shales of contrasting organic richness from Rajmahal Basin of India were heated to different temperatures (pyrolysis at 350, 500 and 650 °C) to assess the temperature protocols necessary for hydrocarbon liberation and investigate the evolution of pore structural facets with implications for CO2 sequestration in underground thermally treated shale horizons. Our results from low-pressure N2 adsorption reveal reduced adsorption capacity in the shale splits treated at 350 and 500 ºC, which can be attributed to structural reworking of the organic matter within the samples leading to formation of complex pore structures that limits the access of nitrogen at low experimental temperatures. Consequently, for both the studied samples BET SSA decreased by ∼58% and 72% at 350 °C, and ∼67% and 68% at 500 °C, whereas average pore diameter increased by ∼45% and 91% at 350 °C, and ∼100% and 94% at 500 °C compared to their untreated counterparts. CO2 adsorption results, unlike N2, revealed a pronounced rise in micropore properties (surface area and volume) at 500 and 650 ºC (∼30%–35% and ∼41%–63%, respectively for both samples), contradicting the N2 adsorption outcomes. Scanning electron microscope (SEM) images complemented the findings, showing pore structures evolving from microcracks to collapsed pores with increasing thermal treatment. Analysis of the SEM images of both samples revealed a notable increase in average pore width (short axis): by ∼4 and 10 times at 350 °C, ∼5 and 12 times at 500 °C, and ∼10 and 28 times at 650 °C compared to the untreated samples. Rock-Eval analysis demonstrated the liberation of almost all pyrolyzable kerogen components in the shales heated to 650 °C. Additionally, the maximum micropore capacity, identified from CO2 gas adsorption analysis, indicated 650 °C as the ideal temperature for in situ conversion and CO2 sequestration. Nevertheless, project viability hinges on assessing other relevant aspects of shale gas development such as geomechanical stability and supercritical CO2 interactions in addition to thermal treatment.

Numerical Simulation and Experimental Comparison of System Analysis Module 1D Mixing Model for Cold Shock Transients in the Gallium Thermal-Hydraulic Mixing Facility

Liquid metals are being investigated as coolants in many advanced reactor designs because of their high thermal conductivity and effectiveness at high temperatures. However, they often pose challenges to reactor operation and safety because of the complex thermal mixing and stratification in the plenum of pool-type reactor designs. The advanced system analysis code System Analysis Module (SAM) currently under development at Argonne National Laboratory aims to develop and implement thermal mixing models to accurately capture these complex thermal fluid behaviors. In this study, the SAM thermal mixing model was compared against experimental data from the Gallium Thermal-Hydraulic Experiment facility, a scaled liquid metal test facility that uses gallium as a surrogate fluid to investigate the stratification and thermal mixing of low-Prandtl-number fluids in the upper plenum of a liquid metal–cooled reactor. Two cold shock transient cases were used: one with stable stratified flow (Ri = 32) and one with stronger thermal mixing (Ri = 0.5). The resultant temperatures were then compared with the experimental temperatures over the entire plenum to assess the ability of the mixing models to capture the thermal behavior and to better correspond mixing parameters to various flow scenarios. Generally, the zero-dimensional mixing model was more capable of capturing the bulk temperature of the component modeled assuming that an accurate mass flow rate was provided, but it was inherently unable to capture thermal gradients in space. The one-dimensional mixing model was capable of capturing that the thermal gradients provided accurate selection of the mixing coefficients. The temperature at the outlet junction was compared over time for each of the mixing models with the recorded experimental temperature. The implemented mixing models demonstrated the ability to effectively capture the overall thermal behavior for stronger mixing scenarios but struggled with more stably stratified flows. It was found that a system analysis code’s covering of the entire range of different operating conditions still remains a challenging task, and it is suggested that further model and closure improvements are necessary to accurately capture complex thermal mixing and stratification phenomena.

Pyrolytic hydrocarbon generation characteristics of the Chang 7 shale based on different experimental methods: Implications for shale oil and gas in the Ordos Basin

Shale oil and gas resources are abundant in the Chang 7 shale of the Yanchang Formation in Ordos Basin. To determine the characteristics and influencing factors of hydrocarbon generation evolution of the Chang 7 shale, a series of thermal simulation experiments were conducted on low‐maturity shale and kerogen samples. The results indicate that the maximum yield of shale oil are 294.5 and 304.3 mg/g TOC for kerogen sample at heating rates of 20 and 2°C/h, and the corresponding experimental temperatures are 360.2°C and 408.0°C, respectively. The utilization of lower heating rates is favourable for shale oil generation and it is recommended to employ a lower heating rate during in situ heating processes to maximize the economic benefits. The formation of crude oil cracking gas begins when simulating temperature exceeds 528.0°C (Easy Ro 2.6%) at a heating rate of 20°C/h and 480.0°C (Easy Ro 2.5%) at a heating rate of 2°C/h, as indicated by the carbon isotopic composition of gaseous hydrocarbons. The maximum oil production rate of the rock powder sample is 159.8 mg/g TOC, which is lower than that of the kerogen sample. It suggests that certain minerals in the Chang 7 shale may impede hydrocarbon generation. After the addition of pyrite, the highest yield of shale oil is 213.96 mg/g TOC, 33.9% higher than the yield of the original rock powder sample, reflecting the positive catalytic effect of pyrite on hydrocarbon generation of Chang 7 shale. Under geologic conditions, pyrite catalytic hydrocarbon generation may act primarily on the migration of organic matter by macromolecules, which considerably increases the probability of direct contact between pyrite and organic matter. Therefore, the organic‐rich shale with high pyrite content in Chang 7 member is the preferred target for in situ conversion of shale oil and gas in the Ordos Basin.

Thermophysical properties of Ni-Ti melts measured by electromagnetic levitation method using static magnetic field

The normal spectral emissivity, molar heat capacity at constant pressure, and thermal conductivity of Ni-Ti melts were measured during electromagnetic levitation under a static magnetic field. The emissivity and heat capacity of the Ni-Ti melts were measured under a 3 T static magnetic field. The temperature range for the emissivity measurements was 1240–1839 K, and the temperature range for the heat capacity measurements ranged was 1223–1851 K. The emissivity and heat capacity of the Ni-Ti melts, except for the Ni mole fractions (xNi) of 0 and 0.25, showed without temperature dependence within the experimental temperature range. Furthermore, the heat capacity was larger than the ideal solution over the whole range of compositions. The emissivity of the Ni-Ti melts was discussed based on the Drude model. The temperature dependence of thermodynamic functions, such as enthalpy of mixing, excess entropy, and excess Gibbs energy, were calculated using excess heat capacity. The thermal conductivity of Ni-Ti melts was measured under a static magnetic field of 10 T. The temperature range for the thermal conductivity measurements was 1177–1900 K. The thermal conductivities of the Ni-Ti melts increased with increasing temperature, exhibited a local minimum for xNi = 0.75, and were higher than those calculated using the Wiedemann–Franz laws. This difference in thermal conductivity was discussed by considering the contribution of atomic vibrations.

Research on Experimental and Simulated Temperature Control Performance of Power Batteries Based on Composite Phase Change Materials

The power battery is a key component of electric vehicles and its performance is greatly affected by temperature. Battery thermal management systems based on phase change materials can effectively control the battery temperature and at the same time have the advantages of simple structures, energy savings, and good temperature uniformity, and has broad development prospects. In this paper, expanded graphite–paraffin composite phase change materials were prepared, phase change material cooling experiments were carried out, and a phase change material cooling simulation model was also established using the Fluent software to study the influence of phase change material thermophysical parameters on thermal management performance. The results show that the phase change material thermal management method has excellent cooling performance. The best thermal management performance is achieved at the 3C discharge rate, with a phase change material filling thickness of 4 mm, a melting point of 40 °C above ambient temperature, and a thermal conductivity of 3 W/(m·K). When the phase change latent heat was increased from 150 J/g to 250 J/g, the liquid phase ratio decreased from 0.84 to 0.51, and the subsequent cooling performance was greatly improved, so the phase change latent heat should be increased as much as possible.

Utilization of Nanocenospheres a waste material to improve the physical and rheological properties of SBS asphalt binders

The performance enhancement of asphalt binders by incorporating innovative additives has been a subject of significant research and industry interest. This study emphasizes the potential of Nano polymer composites as a promising additive for improving the performance of asphalt binders, providing valuable insights into developing advanced asphalt materials for sustainable road infrastructure construction and maintenance. It explores the utilization of nano cenospheres to amplify the attributes of Styrene-Butadiene-Styrene (SBS) modified asphalt binders. It introduces a novel approach by incorporating Nano polymer composites (NPC) comprising nanocenosphere particles and Styrene-butadiene-Styrene Particles. Nanocenosphere particles are the waste materials derived from coal combustion in thermal power plants. Styrene-butadiene-styrene is a type of thermoplastic elastomer, a synthetic rubber. A series of experimental tests, penetration, softening point, ductility, performance grading, temperature sweep, multiple stress and creep recovery, frequency sweep, linear amplitude sweep, and rutting aging index, is conducted to evaluate changes in physical and rheological properties. Results indicate that adding nano cenospheres particles in SBS asphalt binder enhances its softening point, elasticity recovery, rutting resistance, fatigue life, storage stability, and aging resistance compared to traditional SBS-modified asphalt binders. Statistical analyses were accomplished to comprehend the influence of the Nano polymer composites. This analysis provides valuable insights into the effects of nanocenospheres on SBS-modified binders. Through rigorous statistical analysis, a thorough interpretation of how the incorporation of nanocenospheres influences the attributes of Nano-polymer composites.

The experimental implications of the rate of temperature change and timing of nutrient availability on growth and stoichiometry of a natural marine phytoplankton community

AbstractClimate change increases the need to understand the effect of predicted future temperature and nutrient scenarios on marine phytoplankton. However, experimental studies addressing the effects of both drivers use a variety of design approaches regarding their temperature change rate and nutrient supply regimes. This study combines a systematic literature map to identify the existing bias in the experimental design of studies evaluating the phytoplankton response to temperature change, with a laboratory experiment. The experiment was designed to quantify how different temperature levels (6°C, 12°C, and 18°C), temperature regimes (abrupt vs. gradual increase), timings of nutrient addition (before or after the temperature change) and nutrient regimes (limiting vs. balanced) alter the growth and stoichiometry of a natural marine phytoplankton community. The systematic map revealed three key biases in marine global change experiments: (1) 66% of the studies do not explicitly describe the experimental temperature change or nutrient regime, (2) 84% applied an abrupt temperature exposure, and (3) only 15% experimentally manipulated the nutrient regime. Our experiment demonstrated that the identified biases in experimental design toward abrupt temperature exposure induced a short‐term growth overshoot compared to gradually increasing temperatures. Additionally, the timing of nutrient availability strongly modulated the direction of the temperature effect and strength of growth enhancement along balanced N : P supply ratios. Our study stresses that the rate of temperature change, the timing of nutrient addition and the N : P supply ratio should be considered in experimental planning to produce ecologically relevant results as different setups lead to contrasting directions of outcome.

Experimental study of parchment coffee drying using the combined fluidization and microwave process: Analysis of drying curves and thermal imaging

In this study, several experimental drying conditions for parchment coffee were investigated using microwave-assisted fluidization. The experiments were carried out in a prototype equipment consisting of a multimode microwave equipment (700 W and 2.45 GHz frequency) with a drying chamber inside of the cavity. Fluidization was provided by a centrifugal blower (1500 rpm nominal) operating at different controlled speeds. The experimental design corresponded to three microwave power levels (0, 210 and 350 W) and different air speeds (0, 1.7 and 3.4 m/s) at 25 and 40 °C. The experimental moisture evolution and temperature distribution showed that fluidization homogenizes the temperature profiles. Thermographic images further indicated that intermediate microwave power levels (210 W) achieved high uniformity in surface temperature distribution. The combination of fluidization and microwaves facilitated a significant acceleration of the drying rate without exceeding temperature limits, thus preventing any adverse effects on the final product's quality.

Gas phase product evolution during high temperature pyrolysis of PTFE: Development of ReaxFF simulation protocol

The formation of products of incomplete destruction (PIDs) from fluoropolymer incineration is poorly understood and it is imperative to environmental impact studies. The lack of analytical standards limits the experimental approaches targeting product analysis. To navigate this challenge, computational modeling of the thermal degradation of fluoropolymers provides simulated product distributions. However, it is essential to benchmark reactive forcefields to accurately simulate fluoropolymer pyrolysis. The present work describes a protocol to perform accurate simulations of the thermal degradation of fluoropolymers to probe the PIDs. The ReaxFF force field was applied to reproduce the experimental bulk density and glass transition temperature of polytetrafluoroethylene (PTFE). The benchmarked methodology developed has been extended to provide simulated product distributions and mechanistic insights which are in excellent agreement with primary literature. On the basis of our simulated data, we observe a degradation mechanism that proceeds through three primary steps: 1) initiation of random backbone cleavage, 2) C2F4 unzipping through β–scission (as opposed to CF2 unzipping), and 3) secondary product formation. An extension of the developed protocol has the potential to simulate the thermal degradation of non-polymeric per- and polyfluoroalkyl substances (PFASs) in addition to long-chain fluoropolymers.

Energy optimization of a steel slab reheating furnace through the use of swirl and diffusion burners using a new mathematical simulation methodology

This study proposed a new methodology to optimize the fuel use in a walking beam reheating furnace that uses swirl burners in the soaking zone through mathematical simulation. Likewise, the radiative effect of the WSGGM model over the heating and thermal gradient of the slab was analyzed, as well as its thermal implications of using swirl and diffusion burners. The model was validated with experimental temperatures obtained inside the furnace by using 16 thermocouples, and they were compared with those in the simulation, reaching an average error of 3.19%. This methodology has allowed the proposal of new operating conditions in fuel management, making the combustion process more efficient with an average saving of 5,067,360 kg of methane annually, representing 9% of the plant’s current use. This optimization process would mean substantial economic savings for the industry and would also be reflected in a significant decrease of greenhouse gases with adverse effects on the planet.

Frictional Properties of Feldspar‐Chlorite Gouges and Implications for Fault Reactivation in Hydrothermal Systems

AbstractAs a particularly common mineral in granites, the presence of feldspar and feldspar‐chlorite gouges at hydrothermal conditions has important implications in fault strength and reactivation. We present laboratory observations of frictional strength and stability of feldspar (K‐feldspar and albite) and feldspar‐chlorite gouges under conditions representative of deep geothermal reservoirs to evaluate the impact on fault stability. Velocity‐stepping experiments are performed at a confining stress of 95 MPa, pore pressures of 35–90 MPa, and temperatures of 120–400°C representative of in situ conditions for such reservoirs. Our experiment results indicate that the feldspar gouge exhibits strong friction (μ ∼ 0.71) at all experimental temperatures (∼120–400°C) but when T > 120°C, the frictional response transitions from velocity‐strengthening to slightly velocity‐weakening. At constant confining pressure and temperature, increasing the pore pressure increases the friction coefficient (∼0.70–0.85) and the gouge remains slightly velocity weakening. The presence of alteration‐sourced chlorite leads to a transition from velocity weakening to velocity strengthening in the mixed gouge at experimental temperatures and pore pressures. As a ubiquitous mineral in reservoir rocks, feldspar is shown to potentially contribute to unstable sliding over ranges in temperature and pressure typical in deep hydrothermal reservoirs. These findings emphasize that feldspar minerals may increase the potential for injection‐induced seismicity on pre‐existing faults if devoid of chloritization.

Land use modulates resistance of grasslands against future climate and inter-annual climate variability in a large field experiment.

Climate and land-use change are key drivers of global change. Full-factorial field experiments in which both drivers are manipulated are essential to understand and predict their potentially interactive effects on the structure and functioning of grassland ecosystems. Here, we present 8 years of data on grassland dynamics from the Global Change Experimental Facility in Central Germany. On large experimental plots, temperature and seasonal patterns of precipitation are manipulated by superimposing regional climate model projections onto background climate variability. Climate manipulation is factorially crossed with agricultural land-use scenarios, including intensively used meadows and extensively used (i.e., low-intensity) meadows and pastures. Inter-annual variation of background climate during our study years was high, including three of the driest years on record for our region. The effects of this temporal variability far exceeded the effects of the experimentally imposed climate change on plant species diversity and productivity, especially in the intensively used grasslands sown with only a few grass cultivars. These changes in productivity and diversity in response to alterations in climate were due to immigrant species replacing the target forage cultivars. This shift from forage cultivars to immigrant species may impose additional economic costs in terms of a decreasing forage value and the need for more frequent management measures. In contrast, the extensively used grasslands showed weaker responses to both experimentally manipulated future climate and inter-annual climate variability, suggesting that these diverse grasslands are more resistant to climate change than intensively used, species-poor grasslands. We therefore conclude that a lower management intensity of agricultural grasslands, associated with a higher plant diversity, can stabilize primary productivity under climate change.

Effect of Rearing Technology on Production Performance, Selected and Blood Parameters and Welfare Levels of Broiler Chickens During the Summer Production Cycle

Abstract The aim of the present study was to determine the effect of rearing technology (rearing system and dietary supplementation with a mixed herbal extract) on the production results, selected physiological and blood parameters, and welfare of broiler chickens during the summer production cycle. In the CON and HE groups, broiler chickens were kept on litter without access to free range; additionally, in the HE group, birds from 22 to 42 days of rearing received a mixed herbal extract (50% Melissa officinalis L. and 50% Urtica dioica L.) in the amount of 2 ml/l of water to drinkers with water. In the AP group, birds were reared on litter with access to pasture. During the experiment, production performance and body temperature of the birds were monitored. Blood was also taken from birds in each group and the H:L ratio, levels of corticosterone, glucose and thyroid hormones were determined. The application of 2 ml/l of mixed herbal extract to the drinking water did not improve the production results, nor did it affect the physiological indices of the birds studied. The addition of 2 ml/l of mixed herbal extract to the drinking water only resulted in lower corticosterone levels in the blood of the chickens on day 35 of the experiment. The free-range housing system had a negative effect on the slaughter performance of the broiler chickens. However, housing with access to the free range resulted in lower body temperature, lower mortality, as well as lower glucose, corticosterone and a narrower H:L ratio in the blood of the chickens during the period of increasing air temperature. It can therefore be concluded that housing with access to a free range reduces stress levels and thus improves the welfare of broiler chickens during the summer production cycle compared to confined housing. Comparing the rearing technologies used in the study, it was found that the free-range housing system contributed more to improving the comfort of broiler chickens during the summer than dietary supplementation with the tested herbal mixture extract.

Computational fluid dynamics model-based design of continuous forced convection freezing processes for human induced pluripotent stem cells considering supercooling of extracellular solutions

This work presents a computational fluid dynamics (CFD) model-based process design of forced convection continuous freezing for human induced pluripotent stem (hiPS) cells considering supercooling of extracellular solutions. The overall model consists of a CFD model for velocity field and heat transfer calculations including the effect of the supercooling, and a cell layer model for cell survival rate calculations. Experimental temperature profiles were obtained using a forced convection-based batch freezer, and the validation of the heat transfer and solidification models was performed. The experiments were carried out by applying a 1.0 K min–1 cooling rate with an inlet velocity of 2.0 m s–1. The model was applied to three different freezer sizes with shelves containing 10, 20 and 30 rows. The applied coolant inlet velocities ranged from 0.50 m s–1 to 4.0 m s–1. It was found that the application of an inlet velocity of 3.0 m s−1 yielded an average cell survival rate of 0.934 with low survival rate heterogeneity in the freezers. This way, the freezing process for hiPS cells could be scaled to up to 170-fold compared to currently used equipment for hiPS cell freezing.

Investigation of methyl radical with methane and methanol reactions in the framework of a non-equilibrium approach; dynamic aspect

Within the framework of the non-equilibrium approach, the thermal rate constants of the methyl radical with methane (reaction (1)) and CH and OH bonds of methanol (respectively, reactions (2) and (3)) were calculated in the experimental temperature range: 450–800 K for reaction 1 and 350 – 550 K for reactions (2) and (3); geometry optimization level B3LYP/6-31+G**, SP calculation levels CСSD(T)/6-311++G** for reaction (1) and CСSD(T)/6-311G** for reactions 2 and 3.The analysis of the obtained results demonstrates differences in the dynamics of the H-atom transition. The possibility of describing the dynamic situation in terms of the tunneling time of the H atom and the half-life of the umbrella oscillation of the methyl radical is discussed.

Clumped Isotope Signatures of Abiotic Methane: The Role of the Combinatorial Isotope Effect

AbstractMethane clumped isotope signatures of abiogenesis may be diagnostic of the origin of methane on Earth and other planetary bodies. We performed synthesis of abiogenic methane in hydrothermal conditions between 130 and 300°C and determined δ13C, δD, Δ13CH3D, and Δ12CH2D2. The experiments were performed by heating water in the presence of Fe0 powder and CO. The reduction of water on metallic iron led to the formation of H2. CO was reacted with both H2 and H2O, generating both CH4 and CO2. Methane δ13C values are isotopically depleted by ∼25‰ relative to the CO starting material. This is consistent with carbon isotopic equilibrium between methane, carbon monoxide and carbon dioxide in our experiments. In contrast, D/H ratios are inconsistent with equilibrium isotopic fractionation, as illustrated by δD values of methane fractionated by ∼500‰ relative to starting H2O. This suggests that under our experimental conditions, hydrogen additions to carbon may be governed by kinetics. Δ13CH3D values track experimental temperature, with values between +1.5‰ and +5.0‰ for most samples. In contrast, Δ12CH2D2 values are displaced from equilibrium. We find exclusively negative Δ12CH2D2 values, showing deficits down to 40‰ relative to thermodynamic equilibrium. We interpret the data as evidence for distinct, kinetically induced D/H pools contributing to methane assembly, that is, a combinatorial effect. The cumulative D/H fractionations associated with CO hydrogenation explain the direction and magnitude of Δ12CH2D2 values during abiotic methane formation. We suggest that near equilibrium Δ13CH3D with negative Δ12CH2D2 signatures will help identify methane formed abiotically in nature.