Understanding the role of lipids in aroma formation of circulating non-fried roasted chicken using UHPLC-HRMS-based lipidomics and heat transfer analysis

The role of lipids in aroma formation of circulating non-fried roasted (CNR) chicken with different roasting times was studied using ultra-high performance liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS)-based lipidomics and heat transfer analysis. Thirteen odorants were confirmed as important aroma compounds of CNR chicken, including dimethyl trisulfide, 3,5-dimethyl-2-ethylpyrazine, nonanal, and 1-octen-3-ol. A comprehensive lipidomics analysis identified 1254 lipids in roasted chickens, classified into 23 distinct lipid categories that included 281 phosphatidylcholines (PC), 223 phosphatidylethanolamines (PE), and 202 triglycerides (TG). Using OPLS-DA analysis, the lipid PG (18:1_18:1) showed promise as a potential biomarker for distinguishing between chickens subjected to CNR treatments with varying roasting times. The lipids PC, PE, and their derivatives are likely to play a crucial role in the formation of aroma compounds. In addition, TGs that contributed to the retention of key odorants in roasted chicken included TG (16:0_16:0_18:1), TG (16:0_16:0_18:0), and TG (16:0_18:1_18:1). Findings further showed that lower water activity and specific heat capacity promoted the formation and retention of aroma compounds during the CNR process. This study contributed to a better understanding of the formation of aroma compounds through lipid oxidation in roasted chicken.

Water bath is more efficient than hot air oven at thermal inactivation of coronavirus

BACKGROUND

Thermal inactivation is a conventional and effective method of eliminating the infectivity of pathogens from specimens in clinical and biological laboratories, and reducing the risk of occupational exposure and environmental contamination. During the COVID-19 pandemic, specimens from patients and potentially infected individuals were heat treated and processed under BSL-2 conditions in a safe, cost-effective, and timely manner. The temperature and duration of heat treatment are optimized and standardized in the protocol according to the susceptibility of the pathogen and the impact on the integrity of the specimens, but the heating device is often undefined. Devices and medium transferring the thermal energy vary in heating rate, specific heat capacity, and conductivity, resulting in variations in efficiency and inactivation outcome that may compromise biosafety and downstream biological assays.

METHODS

We evaluated the water bath and hot air oven in terms of pathogen inactivation efficiency, which are the most commonly used inactivation devices in hospitals and biological laboratories. By evaluating the temperature equilibrium and viral titer elimination under various conditions, we studied the devices and their inactivation outcomes under identical treatment protocol, and to analyzed the factors, such as energy conductivity, specific heat capacity, and heating rate, underlying the inactivation efficiencies.

RESULTS

We compared thermal inactivation of coronavirus using different devices, and have found that the water bath was more efficient at reducing infectivity, with higher heat transfer and thermal equilibration than a forced hot air oven. In addition to the efficiency, the water bath showed relative consistency in temperature equilibration of samples of different volumes, reduced the need for prolonged heating, and eliminated the risk of pathogen spread by forced airflow.

CONCLUSIONS

Our data support the proposal to define the heating device in the thermal inactivation protocol and in the specimen management policy.

Response of thermal conductivity of loess after high temperature in northern Shaanxi burnt rock area, China

Spontaneous combustion of coal seams can produce a high temperature of about 800 ℃, which greatly changes the thermal conductivity of the overlying loess layer. The thermal conductivity of loess plays an important role in ecological restoration design and the calculation of roadbed and slope stability. In this study, loess in northern Shaanxi, China was taken as the research object to measure the mass-loss rate and heat conduction parameters of loess specimens after high temperature. The test results show that, between 23 and 900 °C, with temperature increasing, the mass-loss rate is reduced. And the heat conduction coefficient (λ), specific heat capacity (c), and thermal diffusion coefficient (α) decreased by 48.9%, 23.1%, and 35.6%. This is due to the air thermal resistance effect caused by the increase of pores and cracks in loess specimens after high temperature.

Fast differential scanning calorimetry to mimic additive manufacturing processing: specific heat capacity analysis of aluminium alloys

Eutectic AlSi12, commonly used in casting and in additive manufacturing, is investigated with Fast Differential Scanning Calorimetry to determine the impact of different cooling rates from the liquid state upon the apparent specific heat capacity on subsequent heating. A heat flow correction strategy is developed and refined for the reliable and precise measurement of sample heat flow using chip sensors and assessed by the evaluation of results on pure (99.999%) aluminium. That strategy is then applied to the study of the AlSi12 eutectic alloy, and rate-dependent perturbations in the measured apparent specific heat capacity are discussed in terms of Si supersaturation and precipitation. Several cooling rates were implemented from - 100 to - 30,000 K s^-1, and subsequent heating ranged from + 1000 to + 30,000 K s^-1. After rapid cooling, a drop in AlSi12 apparent specific heat capacity is found on heating above ~ 400 °C; even at rates of + 10,000 K s^-1, a result which has high relevance in metal additive manufacturing where similarly fast temperature cycles are involved. The Literature data, temperature modulated DSC and CALPHAD simulations on the heat capacity of AlSi12 are used to provide comparative context to the results from Fast Differential Scanning Calorimetry.

Influence of elemental composition on structural, thermal and hydration behavior of gold-silver bimetallic nanoparticles

In this study, molecular dynamics simulations (MDs) have been employed to explore the influence of elemental composition on the structural, thermal, and hydration behavior of the core-shell gold-silver bimetallic nanoparticles with three different concentrations Au₁₃₅Ag₁₁₄, Au₈₇Ag₁₆₂, and Au₅₅Ag₁₉₄. The pure gold and silver metal nanoparticles have also been studied for the sake of comparison. The calculated cohesive and formation energy values reveal the enhancement in the stability of gold-silver bimetallic nanoparticles with the increase in the concentration of gold. The specific heat capacity value of the bimetallic gold-silver nanoparticles has been found to increase linearly with the concentration of silver. This suggests that the specific heat capacity value of the gold-silver bimetallic nanoparticles may be improved by raising their silver concentration. The enhancement of specific heat capacity value with respect to the concentration of silver may be attributed to the enhanced phonon density. There is no significant difference in the computed hydration shell and water residence time of the gold-silver bimetallic nanoparticles with respect to their mixing ratio. The obtained stable structure, tunable specific heat capacity values, and the predicted hydration properties of the gold-silver bimetallic nanoparticles may be harnessed for their technological and biological applications.

Investigation on the micromorphology and thermophysical properties of NaNO3 heat storage materials modified by solution combustion

Nitrate has a wide temperature range, wide operating temperature, low vapor pressure, low cost, strong heat transfer and stable chemical properties. It is widely used in solar thermal power generation heat storage material. In this paper, the alkali salt NaNO₃ was modified by solution combustion method with citric acid as fuel. The structure and thermal properties of the prepared salts were studied by field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR) and differential scanning calorimetry (DSC). The results show that the solution combustion process improves the structure and thermal properties of NaNO₃, and the resulting product has a new phase. The particle size and microscopic morphology of the prepared salt were changed. As the proportion of fuel increases, the hollow cuboid structure gradually grows on the surface and inside of the modified salt. The microstructure obtained is different at different ignition temperatures, and a finer and even rod-like structure is obtained at an ignition temperature of 600 °C. The specific heat capacity of all modified samples has been improved, among which solid specific heat and liquid specific heat have increased the most, respectively 3.10 J/g·K and 3.19 J/g·K, which are 140.31% and 131.16% higher than the base salt, respectively. This work not only studies the specific heat capacity of NaNO₃ modified by solution combustion, but also explores the effect of micromorphology and new phase formation on its performance, which provides innovative ideas for improving the specific heat capacity of molten salt heat storage materials.

National Standard and New Reference Material for Specific Heat Capacity Measurements

Thermal analysis and calorimetry share a close relationship in the field of thermal research. With regards to the specific heat capacity, researchers have been able to realize absolute measurement techniques by utilizing drop, conduction, and adiabatic methods that are used in calorimetry. Furthermore, it is possible to optimize differential scanning calorimetry, which is a comparative measurement technique for the specific heat capacity used in thermal analysis, by improving the absolute measurement techniques. At the National Metrology Institute of Japan (NMIJ), we developed a new certified reference material (CRM) for comparatively measuring the specific heat capacity, the single-crystalline silicon-NMIJ CRM 5806a, using a new type of cryogenic adiabatic calorimeter equipped with a pulse-tube refrigerator working in the temperature range from 50 to 350 K. This CRM was produced in accordance with the quality specifications of NMIJ, and complies with the ISO/IEC 17025, ISO 17034, and ISO GUIDE 35 standards. This paper reports on the procedure for fabricating this CRM and using it to perform specific heat capacity measurements at low temperatures. The specific heat capacity was measured using a differential scanning calorimeter in the temperature range from 280 to 340 K. NMIJ CRM 5806a was used to calibrate the heat flow. It was found that the uncertainty evaluation became easier because one factor of the uncertainty evaluation could be removed using the CRM. We show that the development of the CRM using the adiabatic calorimeter has led to an improvement in the specific heat capacity measurement results obtained by the differential scanning calorimeter.

Specific heat and thermal conductivity of municipal solid waste and its effect on landfill fires

Municipal Solid Waste (MSW) landfills are sources of physical, chemical and microbiological processes and as a result, gases and heat are generated as by-products. The generated heat flows from the higher to lower temperature regions within the landfill. Specific heat and thermal conductivities are two important properties that determine heat flow in MSW landfills. The goal of this study was to determine the thermal conductivity and specific heat capacity of MSW samples of Indian origin and to study its effect on landfill fires. Thermal conductivity and specific heat capacity of waste samples collected from dumpsite at Bhandewadi landfill, Nagpur & Bellahalli landfill, Bangalore (India) and the synthetic MSW (prepared in the lab) were determined using newly designed and fabricated experimental set-up. Results showed that moisture and organic content of MSW are directly proportional to specific heat capacity and indirectly proportional to thermal conductivity. Thermal conductivity of MSW is directly proportional to its density and specific heat is indirectly proportional to the density of MSW. MSW with specific heat and thermal conductivity in the range 0.003 J/g. K - 0.47 J/g. K and 0.35-3.6 J/s. m. K, respectively were found between 30 and 75 °C with 5% to 25% moisture content. As the temperature increases above 75 °C, decrease in thermal conductivity & increase in specific heat was observed and thermal conductivity of 0.07 J/s. m. K was observed at 130-140 °C. As a result of this, heat does not flow and gets concentrated in that region leading to landfill fire.

Simulation studies on structural and thermal properties of alkane thiol capped gold nanoparticles

The structural and thermal properties of the passivated gold nanoparticles were explored employing molecular dynamics simulation for the different surface coverage densities of the self-assembled monolayer (SAM) of alkane thiol. The structural properties of the monolayer protected gold nanoparticles such us overall shape, organization and conformation of the capping alkane thiol chains were found to be influenced by the capping density. The structural order of the thiol capped gold nanoparticles enhances with the increase in the surface coverage density. The specific heat capacity of the alkane thiol capped gold nanoparticles was found to increase linearly with the thiol coverage density. This may be attributed to the enhancement in the lattice vibrational energy. The present simulation results suggest, that the structural and thermal properties of the alkane thiol capped gold nanoparticles may be modified by the suitable selection of the SAM coverage density.

Effect of high energy electron beam (10MeV) on specific heat capacity of low-density polyethylene/hydroxyapatite nano-composite

In the present work, thermal properties of low density polyethylene (LDPE) and its nano composites are investigated. For this purpose LDPE reinforced with different weight percents of hydroxyapatite (HAP) powder which was synthesized via hydrolysis method are produced. The samples were irradiated with 10MeV electron beam at doses of 75 to 250kGy. Specific heat capacity measurement have been carried out at different temperatures, i.e. 25, 50, 75 and 100°C using modulated temperature differential scanning calorimetry (MTDSC) apparatus and the effect of three parameters include of temperature, irradiation dose and the amount of HAP nano particles as additives on the specific heat capacity of PE/HAP have been investigated precisely. The MTDSC results indicate that the specific heat capacity have decreased by addition of nano sized HAP as reinforcement for LDPE. On the other hand, the effect of radiation dose is reduction in the specific heat capacity in all materials including LDPE and its nano composites. The HAP nano particles along with cross-link junctions due to radiation restrain the movement of the polymer chains in the vicinity of each particle and improve the immobility of polymer chains and consequently lead to reduction in specific heat capacity. Also, the obtained results confirm that the radiation effect on the specific heat capacity is more efficient than the reinforcing effect of nano-sized hydroxyapatite.

Thermal Storage Properties of Molten Nitrate Salt-Based Nanofluids with Graphene Nanoplatelets

In this study, the effect of concentration of nanoparticles on the thermal storage properties of molten nitrate salt-based nanofluids with graphene nanoplatelets (GNPs) was investigated. Solar salt consisting of sodium nitrate and potassium nitrate was utilized as the base material for the nanofluids. Homogeneous dispersion of GNPs within the solar salt was observed through scanning electron microscopy analysis. For both solar salt and resultant nanofluids, differential scanning calorimetry was employed to measure the thermal storage properties, including characteristic temperatures of phase change, startup heat, and specific heat capacity (SHC). A maximum increase of 16.7 % in SHC at the liquid phase was found at an optimal concentration of 1 wt% of GNPs. At the same concentration, the onset temperature decreased by 10.4 °C, the endset temperature decreased by 4.7 °C, and the startup heat decreased by 9 %.

On the specific heat capacity enhancement in nanofluids

Molten salts are used as heat transfer fluids and for short-term heat energy storage in solar power plants. Experiments show that the specific heat capacity of the base salt may be significantly enhanced by adding small amounts of certain nanoparticles. This effect, which is technically interesting and economically important, is not yet understood. This paper presents a critical discussion of the existing attendant experimental literature and the phenomenological models put forward thus far. A common assumption, the existence of nanolayers surrounding the nanoparticles, which are thought to be the source of, in some cases, the large increase of a nanofluid's specific heat capacity is criticized and a different model is proposed. The model assumes that the influence of the nanoparticles in the surrounding liquid is of long range. The attendant long-range interfacial layers may interact with each other upon increase of nanoparticle concentration. This can explain the specific heat maximum observed by different groups, for which no other theoretical explanation appears to exist.

In situ production of titanium dioxide nanoparticles in molten salt phase for thermal energy storage and heat-transfer fluid applications

In this study, TiO₂ nanoparticles (average particle size 16 nm) were successfully produced in molten salt phase and were showed to significantly enhance the specific heat capacity of a binary eutectic mixture of sodium and potassium nitrate (60/40) by 5.4 % at 390 °C and 7.5 % at 445 °C for 3.0 wt% of precursors used. The objective of this research was to develop a cost-effective alternate method of production which is potentially scalable, as current techniques utilized are not economically viable for large quantities. Enhancing the specific heat capacity of molten salt would promote more competitive pricing for electricity production by concentrating solar power plant. Here, a simple precursor (TiOSO₄) was added to a binary eutectic mixture of potassium and sodium nitrate, heated to 450 °C, and cooled to witness the production of nanoparticles.

Increment of specific heat capacity of solar salt with SiO2 nanoparticles

Thermal energy storage (TES) is extremely important in concentrated solar power (CSP) plants since it represents the main difference and advantage of CSP plants with respect to other renewable energy sources such as wind, photovoltaic, etc. CSP represents a low-carbon emission renewable source of energy, and TES allows CSP plants to have energy availability and dispatchability using available industrial technologies. Molten salts are used in CSP plants as a TES material because of their high operational temperature and stability of up to 500°C. Their main drawbacks are their relative poor thermal properties and energy storage density. A simple cost-effective way to improve thermal properties of fluids is to dope them with nanoparticles, thus obtaining the so-called salt-based nanofluids. In this work, solar salt used in CSP plants (60% NaNO3 + 40% KNO3) was doped with silica nanoparticles at different solid mass concentrations (from 0.5% to 2%). Specific heat was measured by means of differential scanning calorimetry (DSC). A maximum increase of 25.03% was found at an optimal concentration of 1 wt.% of nanoparticles. The size distribution of nanoparticle clusters present in the salt at each concentration was evaluated by means of scanning electron microscopy (SEM) and image processing, as well as by means of dynamic light scattering (DLS). The cluster size and the specific surface available depended on the solid content, and a relationship between the specific heat increment and the available particle surface area was obtained. It was proved that the mechanism involved in the specific heat increment is based on a surface phenomenon. Stability of samples was tested for several thermal cycles and thermogravimetric analysis at high temperature was carried out, the samples being stable.

PACS

65.: Thermal properties of condensed matter; 65.20.-w: Thermal properties of liquids; 65.20.Jk: Studies of thermodynamic properties of specific liquids.

Temperature-dependent thermal properties of ex vivo liver undergoing thermal ablation

Thermotherapy uses a heat source that raises temperatures in the target tissue, and the temperature rise depends on the thermal properties of the tissue. Little is known about the temperature-dependent thermal properties of tissue, which prevents us from accurately predicting the temperature distribution of the target tissue undergoing thermotherapy. The present study reports the key thermal parameters (specific heat capacity, thermal conductivity and heat diffusivity) measured in ex vivo porcine liver while being heated from 20 ° C to 90 ° C and then naturally cooled down to 20 ° C. The study indicates that as the tissue was heated, all the thermal parameters resulted in plots with asymmetric quasi-parabolic curves with temperature, being convex downward with their minima at the turning temperature of 35-40 ° C. The largest change was observed for thermal conductivity, which decreased by 9.6% from its initial value (at 20 ° C) at the turning temperature (35 ° C) and rose by 45% at 90 ° C from its minimum (at 35 ° C). The minima were 3.567 mJ/(m(3) ∙ K) for specific heat capacity, 0.520 W/(m.K) for thermal conductivity and 0.141 mm(2)/s for thermal diffusivity. The minimum at the turning temperature was unique, and it is suggested that it be taken as a characteristic value of the thermal parameter of the tissue. On the other hand, the thermal parameters were insensitive to temperature and remained almost unchanged when the tissue cooled down, indicating that their variations with temperature were irreversible. The rate of the irreversible rise at 35 ° C was 18% in specific heat capacity, 40% in thermal conductivity and 38.3% in thermal diffusivity. The study indicates that the key thermal parameters of ex vivo porcine liver vary largely with temperature when heated, as described by asymmetric quasi-parabolic curves of the thermal parameters with temperature, and therefore, substantial influence on the temperature distribution of the tissue undergoing thermotherapy is expected.