Heat Flow Measurements Research Articles

Isothermal Titration Calorimetry in Biocatalysis

Isothermal titration calorimetry (ITC) is a popular chemical analysis technique that can be used to measure macromolecular interactions and chemical and physical processes. ITC involves the measurement of heat flow to and from a measurement cell after each injection during a titration experiment. ITC has been useful to measure the thermodynamics of macromolecular interactions such as protein-ligand or protein-protein binding affinity and also chemical processes such as enzyme catalyzed reactions. The use of ITC in biocatalysis has a number of advantages as ITC enables the measurement of enzyme kinetic parameters in a direct manner and, in principle, can be used for most enzymes and substrates. ITC approaches have been developed to measure reversible and irreversible enzyme inhibition, the effects of molecular crowding on enzyme activity, the activity of immobilized enzymes and the conversion of complex polymeric substrates. A disadvantage is that in order to obtain accurate kinetic parameters special care has to be taken in proper experimental design and data interpretation, which unfortunately is not always the case in reported studies. Furthermore, special caution is necessary when ITC experiments are performed that include solvents, reducing agents and may have side reactions. An important bottleneck in the use of calorimetry to measure enzyme activity is the relatively low throughput, which may be solved in the future by sensitive chip based microfluidic enzyme calorimetric devices.

The Effect of LiFePO4 Particle Size and Surface Area on the Performance of LiFePO4/Graphite Cells

In an effort to better understand capacity loss mechanisms in LiFePO4 (LFP)/graphite cells, this work considers carbon-coated LFP materials with different surface area and particle size. Cycling tests at room temperature (20 °C) and elevated temperatures show more severe capacity fade in cells with lower surface area LFP material. Measurements of Fe deposition on the negative electrode using micro X-ray fluorescence (μXRF) spectroscopy reveal more Fe on the graphite electrode from cells with low surface area. Measurements of parasitic heat flow using isothermal microcalorimetry show marginally higher parasitic heat flow in cells with low surface area. Cross-sectional SEM images of aged LFP electrodes show micro-fracture generation in large LFP particles, which are more prevalent in the low surface area material. Further, studies on the impact of vacuum drying procedures show that while Fe deposition can be inhibited by removing excess water contamination, the direct impact of Fe deposition on capacity fade is small. Despite the observed particle cracking, differential voltage analysis on aged cells suggested active material loss was not significant, leading to the conclusion that LFP particle fracture instead increases parasitic reaction rates leading to Li inventory loss.

Electric hysteresis and validity of indirect electrocaloric characterization in antiferroelectric ceramics

Antiferroelectric (AFE) materials have garnered considerable attention in electrocaloric (EC) refrigeration owing to the large entropy change accompanying their transitions and the coexistence of positive and negative EC effects. Almost all studies to date of EC response in AFEs have employed the indirect characterization of thermodynamic behavior based on the Maxwell relation, regardless of the significant electric hysteresis behavior of AFEs in unipolar polarization. Herein, using direct isothermal heat flow measurements in the AFE ceramic Pb0.99Nb0.02[(Zr0.6Sn0.4)0.94Ti0.06]0.98O3 as the benchmark, we discover the large deviation in carrying out indirect EC characterization on AFEs. The electric hysteresis also results in self-heating due to the asymmetric exothermic and endothermic cyclic response, and can be calculated quantificationally from the hysteresis area of P-E loops. Our work emphasizes the necessity in carrying out direct EC characterization on AFEs, and suggests the importance in designing AFE EC refrigeration materials with low electric hysteresis.

Linearized Bayesian estimation of magnetization and depth to magnetic bottom from satellite data

SUMMARY Estimating the depth to magnetic bottom (DTB) from magnetic data is one of the most important and difficult potential field inversion problems. Since DTB can often be linked to the Curie isotherm depth of magnetite (∼580 °C), it could provide crucial constraints on heat flow, even in remote or inaccessible areas. Spectral methods are the most popular approach to estimate DTB, but their reliability has been challenged on many grounds. In contrast, space-domain methods have received relatively little attention, even though they might avoid some of the limitations of spectral methods. Furthermore, many DTB estimation methods are to some extent ad hoc, which makes uncertainty estimation and effective communication of the results difficult. In this work, we develop a Bayesian approach to estimate susceptibility and DTB from magnetic data. We describe the subsurface in terms of tesseroids and use a two-step inversion procedure that consists of a Monte Carlo Markov Chain hyperparameter optimization and a linearized inversion. This way, the uncertainties due to unknown hyperparameter are rigorously propagated to the final maps of susceptibility and DTB. Additionally, pointwise constraints based on heat flow measurements can be easily included into the inversion. Synthetic tests are used to determine the accuracy and reliability of the new algorithm. We find that heat flow constraints are necessary to achieve reliable results, although already a small number of points is sufficient. Finally, we apply the algorithm to the Australian continent and demonstrate applicability to real data.

Nature of the lithosphere-asthenosphere boundary beneath the Eastern Dharwar Craton of the Indian Shield

• Thickness and nature of lithosphere-asthenosphere boundary has been discussed. • Partial melts may explain the shallow and sharp lithosphere-asthenosphere boundary. • Plume induced lithospheric thinning argued beneath the Eastern Dharwar Craton . • The Eastern Dharwar Craton lithosphere has been substantially modified. The lithosphere-asthenosphere boundary (LAB) is a fundamental element of the plate tectonic hypothesis that accommodates the differential motion of rigid lithosphere over the weaker asthenosphere . In recent times, various usages have been used to define the LAB, depending on the nature of their measurements. Here, we investigate the lithospheric structure beneath the Eastern Dharwar Craton (EDC) of the Indian Shield using geochemical, thermal and seismological data sets. We analysed S-receiver functions from the stations deployed in the EDC along with the surface wave dispersion tomography. We also added thermal measurements from 5 different locations and geochemical data from 34 Kimberlite/Lamproite xenolith samples to constrain the nature of the LAB. The seismological measurements using Rayleigh wave dispersion and receiver function analysis indicate the lithospheric thickness of 98–118 and 94–118 km respectively, with sharp transition across the LAB. The P-T results from xenoliths are interpreted in concurrence with the heat-flow measurements suggesting a thick thermal lithosphere of ∼ 200 km for the normal mantle solidus with cold geotherm. To reconcile our observations, we invoke partial melts or melts enriched in volatiles, which significantly lowers the viscosity of mantle rocks inducing a zone of weakness between the rigid lithosphere (∼125 km) and the convective asthenosphere. Further, we favour the view that the thick lithosphere beneath the Indian plate has been thinned by a plume during the Gondwanaland breakup at ∼ 130 Ma. The presence of younger kimberlites from the Indian shield support that it is further degenerated by the delamination leading to an uneven topography in the LAB.

Wet roots of high elevation in the western United States

Lithospheric heat transfer strongly modulates the distributions of melt, rock strength, and buoyancy that are responsible for volcanism, seismicity, and elevation. Geotherm models often extrapolate shallow (<3 km) heat flow measurements but are complicated by near-surface hydrology, poorly-known crustal thermal properties, and deep advective transfer by melts and volatiles. Here we compare temperatures estimated from P-wave velocities in the uppermost mantle to those modeled from surface heat flow in the western United States. We show that U.S. Cordilleran regions of high heat flow and high elevation have deep temperatures much lower than predicted by steady-state conductive cooling models. We hypothesize that the discrepancy reflects reaction thermodynamics and advection by migration of volatiles and melts up the lithospheric column. Hydration of the mantle and lower crust by Farallon subduction consumes garnet into melts that absorb latent heat in the lower crust and upper mantle, while hydration reaction enthalpy heats the subduction back-arc mantle, and advection amplifies surface heat flow. This process would increase elevation both by raising temperatures and by converting dense constituents of the mineral assemblage to more buoyant intrusions in the middle and upper crust. The results imply hydration reaction enthalpy changes play a significant role in the dynamics of Cordilleran regions.

Heat Flow variations in Siberia and neighboring regions: A new look

The present work deals with an updated evaluation of heat flow in Siberia (Asian part of Russia) and neighboring regions. It is based on results of geothermal measurements in more than 1680 boreholes and shallow measurements of bottom sediments in lakes localities in Siberia. Also considered are results of heat flow measurements in about 1500 sites in neighboring areas of China, Mongolia and Kazakhstan. Features of geological structures and development of adjacent regions have been factors considered in the evaluation of thermal regime of Siberia. Most of this territory is occupied by two broad platforms (West-Siberian and East-Siberian), markedly different in their thermal regimes. Heat flow in the West-Siberian plate averages 55–60 mW/m2, sometimes rising to 70–80 mW/m2. The East-Siberian platform is characterized by a predominance of low heat flow values in the range of 30–40 mW/m2. The southern and eastern segments of these platforms are framed by mountain-folded areas (Sayano-Baikal, Transbaikal, Verkhoyano-Kolymskaya areas) with heat flow values (in the range of 70–80 mW/m2). These are formed mainly under the influence of mantle heat sources (asthenosphere upwellings and mantle diapirs). Analysis of temperature distributions shows that thermal conditions in the five-kilometer upper layer of rocks are determined by heat flow values. Nevertheless, the thermal field of the Asian part of Siberia has been insufficiently studied. The work also considers heat flow variations of adjacent regions located south of Siberia: Kazakhstan, Northern China and Mongolia.

The Heat Source Origin of Geothermal Resources in Xiong’an New Area, North China, in View of the Influence of Igneous Rocks

The Xiong’an new area has abundant geothermal resources, and heat source research plays an important role in the geothermal system. Using the logging curve, we calculated the radioactive heat production of sedimentary layers and igneous rocks in non-sample wells; analyzed the influence of igneous rock distribution, residual heat, and its thermal increment on crust; and clarified the heat source origin of hydrothermal geothermal resources in Xiong’an new area. Sedimentary layers data (5,504) of 20 wells were converted to determine the applicable GR-A empirical relationship, and the radioactive heat production of igneous rocks with different lithologies was estimated. Finite element simulations show that igneous rock intrusions in the study area reach thermal equilibrium with the surrounding rock after 0.5 Ma at most. Upon cooling, the difference in thermal physical properties to the surrounding rock only leads to a higher heat flow of about 3.55 mW/m2 in the partial of the Niutuozhen salient. It is known that the development of igneous facies impacts the heat source. Under the geothermal background of “cold crust-hot mantle,” the mantel heat was the primary source, which the Yanshanian intrusions injected into the central salient, increasing the crustal heat by about 12% and the heat source by about 6%. The measured heat flow becomes higher in the salient (raised about 12.04 mW/m2–29.25 mW/m2) where the deep faults developed due to the groundwater convection. Heat conduction from crust-mantle heat flow and heat convection caused by deep faults are responsible for the current geothermal state in Xiong’an new area.

Experimental evaluation of the partial thermal energy compensation of hydrate crystallization from cyclopentane-loaded porous activated carbon particles immersed in brine

Hydrate-based desalination (HBD) is a potential water desalination technology that has been studied over the past decades. Recently, an HBD process based on hydrate formation from cyclopentane (CP) loaded on porous activated carbon particles (PACP) was patented (“Method for crystallizing clathrate hydrates, and method for purifying an aqueous liquid using the clathrate hydrates thus crystallized”, EP3153606, 2017). It is thought that the crystallization of CP hydrates from CP adsorbed on PACP might cause partial thermal energy compensation. Actually, the heat released by the exothermic hydrate crystallization should be partially balanced by the endothermic desorption of CP from the PACP. In order to investigate this phenomenon, calorimetric and optical studies (heat flow and refractive index measurements respectively) of hydrate formation in systems consisting of CP-saturated PACP immersed in brines (3.5 wt% NaCl and 8 wt% NaCl) were performed. Comparison of the thermal energy measured directly (through the calorimetric study) - i.e. the energy produced by both hydrate crystallization and CP desorption - and the thermal energy measured indirectly (deduced from the optical study) - i.e. the energy generated by hydrate crystallization only - revealed a balanced energy ranging from 9 to 47 kJ/mol of CP. Comparison of the latter with the differential enthalpy of CP desorption from PACP suggests that the CP converted to hydrates was contained in the large pores of the PACP. It is interesting to note that salinity had no significant impact on the degree of thermal energy compensation obtained.

Means of measurement of heat flows in thermal vacuum research and testing of products of space engineering

We present the results of the comparative analysis of the characteristics of the domestic-made heat flux sensor PTP-1B with widely used foreign-made area sensor FOA-020. The conditions are typical to the ground-based thermovacuum research and testing of space technology products, conducted in the absence of validated converter-sensors of the aggregated heat flux within the density range of up to 2000 W/sq. m and a spectral range of 0.2 - 20 µm. Experimental studies were performed in a thermal vacuum chamber of the experimental stand TEC-2.5 at the temperature of its internal surfaces of 20 0C. Recommendations regarding the possible use of the PTP-1B sensor as a working instrument of measurements in monitoring and diagnostic systems during the processes of ground testing of space technology objects are given

The Lunar Geophysical Network Landing Sites Science Rationale

Abstract The Lunar Geophysical Network (LGN) mission is proposed to land on the Moon in 2030 and deploy packages at four locations to enable geophysical measurements for 6–10 yr. Returning to the lunar surface with a long-lived geophysical network is a key next step to advance lunar and planetary science. LGN will greatly expand our primarily Apollo-based knowledge of the deep lunar interior by identifying and characterizing mantle melt layers, as well as core size and state. To meet the mission objectives, the instrument suite provides complementary seismic, geodetic, heat flow, and electromagnetic observations. We discuss the network landing site requirements and provide example sites that meet these requirements. Landing site selection will continue to be optimized throughout the formulation of this mission. Possible sites include the P-5 region within the Procellarum KREEP Terrane (PKT; (lat: 15°; long: −35°), Schickard Basin (lat: −44.°3; long: −55.°1), Crisium Basin (lat: 18.°5; long: 61.°8), and the farside Korolev Basin (lat: −2.°4; long: −159.°3). Network optimization considers the best locations to observe seismic core phases, e.g., ScS and PKP. Ray path density and proximity to young fault scarps are also analyzed to provide increased opportunities for seismic observations. Geodetic constraints require the network to have at least three nearside stations at maximum limb distances. Heat flow and electromagnetic measurements should be obtained away from terrane boundaries and from magnetic anomalies at locations representative of global trends. An in-depth case study is provided for Crisium. In addition, we discuss the consequences for scientific return of less than optimal locations or number of stations.

Evaluation of Thermal anomaly Preceding Northern Red Sea Earthquake, the 16th June 2020

On the 16th June, 2020, a moderate earthquake (Mw = 5.2) hit the Northern Red Sea region, Egypt, that was felt throughout the Hurghada and Sharm El-Sheikh cities and the surrounding areas without any damages. The thermal anomaly before the earthquakes was widely studied with satellite data, such as NOAA/AVHRR and MODIS. The case study aims to monitor and demonstrate the possibility of any variation of the thermal anomaly of sea surface temperature (SST) before and after the 16th June 2020 earthquake and to correlate the results with the previous heat flow study (deep thermal action). The Daytime/Nighttime (SST) data are retrieved from the OBPG serves as a Distributed Active Archive Center (OB. DAAC). The outputs indicated a thermal anomaly on the June 12th, 2020 a few days before the earthquake, covered a large area around the epicenter 60 km impact area, and reached a high value on the 15th June 2020, one day before the earthquake. For the deep thermal action of the entire crust, the earthquake frequency distributions presumed from the reviewed catalogue indicated that the peak of the seismicity is concentrated close to the center of the rift axis in the Northern Red Sea. The heat flow measurements are increased toward the center of the Red Sea rift and decreased toward both sides, generating some partial melt of the rocks and producing crustal subsidence at the center of the Red Sea rift. These results are compatible with the pattern of the seismic activity and heat flow effect around the epicenter. It could be considered as a short-term precursor of the earthquake.

The effect of the sample pan position on the determination of the specific heat capacity for lipid materials using heat flux DSC

Accurate measurements of specific heat capacity for lipids as a function of temperature, Cp (T), are needed for modeling their crystallization behavior. Differential Scanning Calorimetry, DSC, has been the main technique to determine Cp (T) for numerous materials, including lipids. Key experimental conditions (heating/cooling ramps, sample size, purge gas, and temperature modulation) that affect the measured heat flow, from which Cp (T) is calculated, have been extensively discussed in the literature. Usually, DSC manufacturers provide procedures of what they consider to be the best experimental conditions to measure accurate Cp (T) values with the least uncertainties. The successive nature of these procedures requires the user to perform each step separately, which means that the user needs to take out the empty pan from the DSC furnace to load either the standard material (usually sapphire) or the sample and place it back again into the furnace. Following this method will result in a different pan placement on the sensor each time the DSC furnace is opened, which consequently will influence the heat flow signals. Utilizing the Guide to the Expression of Uncertainty in Measurements (GUM),this paper is intended to quantitatively evaluate the uncertainties in Cp (T) measurements due to the pan position on a heat-flux DSC sensor. Due to this effect, relative expanded uncertainty U values were ∼1.5%, and at least 15–25% as a result of pan placement. The sapphire uncertainty values were much smaller than those from the trimyristin (MMM) sample. With the assistance of FEM simulation, the effect of the different thermal diffusivity of MMM and sapphire on the Cp (T) measurements is elucidated.

Terrestrial Heat Flow Measurement and Numerical Simulation of Lithospheric Thermal State in Western Sichuan, China

Terrestrial Heat Flow Measurement and Numerical Simulation of Lithospheric Thermal State in Western Sichuan, China

Heat Flow Measurement of Human Skin Using a Calorimetric Sensor with a Programmable Thermostat. An Alternative to Climate Chambers

Heat Flow Measurement of Human Skin Using a Calorimetric Sensor with a Programmable Thermostat. An Alternative to Climate Chambers

Geothermal anomalies on the eastern flank of the Cherokee basin, southeastern Kansas, USA

Bottomhole temperature measurements from oil and gas drilling in southeastern Kansas on the eastern flank of the Cherokee basin, in combination with a suite of about 2,200 differential temperature logs recently obtained from wireline logging in coalbed methane wells, define several higher-temperature anomalies at the top of the Mississippian Subsystem strata. Temperatures slightly in excess of 90 oF (35 oC) at depths of about 900 ft (275 m) correspond to geothermal gradients as high as about 60 oC/km.&#x0D; Sparse historical measurements of heat flow in the cratonic Cherokee basin indicate that the thermal anomalies are not likely caused by locally high heat flow. Heat flow in the Cherokee basin is probably in line with most other shallow cratonic basins. The higher-temperature thermal anomalies defined by logging temperatures do not correspond to previously mapped faults or other structural features in the Phanerozoic sedimentary section, but some anomalies are underlain by Precambrian basement lineations that are detectable with aeromagnetic and gravity measurements. Well-log determination of shale content in the Pennsylvanian sedimentary strata overlying the Mississippian limestones indicates that low thermal conductivity caused by higher shale content may cause some of the thermal anomalies. &#x0D; Lateral (advective) movement of warmer, highly saline water from the basin axis cannot account for the anomalies because the anomalies are not characterized by exceptionally highly saline water in Mississippian strata. Similarly, recorded static fluid levels of wells disposing of oilfield saltwater into the Mississippian strata and the deeper Cambrian-Ordovician Arbuckle Group indicate that the deeper Arbuckle strata generally do not have sufficient formation pressure to force Arbuckle formation water upward into the Mississippian through either natural fractures or leaky wellbores. Small-scale changes in salinity, in combination with geologic structuring indicating faulting, make a case for vertical (convective) movement of heated, less saline water from the Arbuckle Group into overlying Mississippian limestones in isolated localities. Buoyancy of the Arbuckle formation water (due to temperature and salinity differences with the cooler and more saline Mississippian water) could also be the primary force behind the convection. Convergence of cooler freshwater moving westward off the Ozark dome and more saline basinal water moving eastward also could be a factor in defining the limits of some thermal anomalies.

Heat Flow Distribution in the Chukchi Borderland and Surrounding Regions, Arctic Ocean

AbstractFifty new heat flow measurements from the Chukchi Borderland (CBL) and adjacent regions of the central Arctic Ocean are reported, where heat flow measurements have been very limited. The average heat flow of the CBL (65 mW/m2) is significantly higher than that of the entire Amerasia Basin (53 mW/m2). In the CBL, the heat flow of the Chukchi Plateau (CP), Northwind Basin (NWB), and Northwind Ridge (NWR) are 64 mW/m2, 69 mW/m2, and 60 mW/m2, respectively. With the aid of nearby seismic profiles, the elevated regional heat flow in the CP and NWR was attributed to the enhanced radiogenic heating of the thick crust (25–29 km), while the most prominent heat flow in the relatively thin crust of the NWB is likely due to the residual heat of a major tectonic extension event. Further numerical heat conduction modeling suggests that the initial rifting of the Amerasia Basin during the Jurassic–Early Cretaceous could not induce such high heat flow in the NWB. Together with recent interpretations of seismic profiles, the elevated heat flow in the NWB could be explained by the residual heat of the Late Cretaceous–early Cenozoic extension. This extension event was contemporaneous with the seafloor spreading in the Makarov Basin and had also been associated with the onset of seafloor spreading in the Eurasia Basin.

Regional Heat Flow Analysis Reveals Frictionally Weak Dead Sea Fault

AbstractThe strength of faults was vigorously debated for years, but lately a growing number of studies suggest that faults are weaker than originally suggested. Nonetheless, only a handful of natural faults have been studied in detail, and only one, the San Andreas, is a strike‐slip fault. Here, we reanalyze 268 surface heat flow measurements taken in the proximity of the southern Dead Sea Transform fault to evaluate its friction. To account for large terrain relief, and the presence of salt diapirs, we apply 3‐D terrain and salt diapir corrections. Based on these corrected heat flow values we estimate that the long‐term frictional resistance of the Dead Sea fault is 0.28 ± 0.17. This low value is similar to friction estimates from the San Andreas fault and several subduction zones.

Analysis of UV-Assisted direct ink writing rheological properties and curing degree

In this research, the relationship between the viscosity and curing degree of an acrylate-based resin under UV light was investigated by UV-rheometer and photo-DSC. The influences of different material compositions were studied with single-factor analysis. Viscosity and heat flow measurements were carried out to identify the relative states of the curing and to evaluate the material curing behavior by quantitative analysis. Different intensities were used to observe the effects on viscosity and curing degree. The findings of this work reveal the correlation between the relative curing degree and viscosity, which is divided into two parts depending on the light intensity. The correlated curve follows second-order polynomial under higher intensities, while the lower intensity follows a Gauss distribution. From the results, the relative curing degree is estimated by observing the viscosity of the resin system during the process. The critical curing degree was also determined to identify the resin phase transfer from the liquid to solid.

The Melt Enthalpy of Pu6Fe

Schwartz, et al., previously reported calorimetry measurements conducted on a Pu-Pu6Fe mixture, from which they derived a melt enthalpy of 31.2 J/g (46.6 kJ/mol) for Pu6Fe. This was the first—and remains the only—such value to appear in the literature. We reanalyze those results in light of two contributions to the measured heat flow not considered in the original report: the melt enthalpy of the excess Pu and the subsequent heating of the liquid mixture. These corrections yield a revised value of 24.4 J/g (36.3 kJ/mol), which we show to be consistent with the melt enthalpy of U6Fe.