Temperature Increment Research Articles

The Enhanced Hydrophobic, Photothermal, and Anti-Icing/Ice-Melting Performance of C/TiN/WC/PDMS Composite Coating by Inserting a Thermal Insulation Layer.

Enhancing the hydrophobic and photothermal characteristics of the coating can significantly boost its anti-icing/ice-melting capabilities. In this study, an epoxy resin thermal insulation layer is interposed between the aluminum sheet substrate and the C/TiN/WC/PDMS photothermal composite coating. This method not only equips the coating with exceptional superhydrophobic properties but also markedly elevates its photothermal and anti-icing/ice-melting performance. The incorporation of the thermal insulation layer has been observed to elevate the water contact angle from approximately 125° to 155° ± 0.5° while simultaneously reducing the water sliding angle from over 90° to about 4° ± 0.5°. In an environmental setting of -15 °C and 65% ± 5% humidity, under irradiation of 1.0, 0.7, 0.5, and 0.3 kW/m2, the coating with the thermal insulation layer exhibited saturation temperature increments of roughly 4.7, 3.4, 5.4, and 4.6 °C, respectively, compared to the photothermal coating without the insulation layer. In the absence of irradiation, the coating with the insulation layer delayed the freezing time of 80 μL water droplets by up to three and six times compared to the coating without an insulation layer and the bare aluminum sheet substrate, respectively. Furthermore, under 0.3 kW/m2 irradiation, the coating with the insulation layer reduced the initial melting time and complete melting time of ice beads by nearly half and one-third, respectively, whereas the ice beads on the aluminum sheet substrate remained unmelted throughout the observation period.

Study on temperature evolution law of coal containing gas under uniaxial loading process with different loading rates

AbstractIn order to investigate the evolution law of coal temperature during the gestation process of coal and gas outburst, laboratory experiments and numerical simulation approaches were employed. Infrared thermal radiation experiments on the surface of outburst coal during uniaxial loading and failure of coal were conducted. A coal and gas thermal‐hydromechanical coupling model considering the endothermic effect of desorption was established. Numerical simulation of uniaxial loading of gas‐containing coal was implemented to study the influences of deformation energy, frictional heat, and adsorption/desorption endothermic effects on coal temperature. The results indicate that the temperature of coal samples during the uniaxial loading and failure process generally exhibits a stepwise temperature increase. In the initial stage, the elastic thermal effect leads to a slow and fluctuating rise in the temperature of coal samples. During the yield and plastic deformation stages, frictional heat causes a rapid increase in the temperature of coal samples. With the increase of the loading rate, the increment of the temperature of coal samples gradually decreases and reaches the peak when the loading stress is 70% of the peak stress. According to the numerical calculation results, with the increase of the loading rate, the temperature reduction caused by gas desorption relatively decreases. By comparing the experimental results and numerical simulation results, it is found that the temperature reduction caused by desorption is greater than the temperature increments caused by deformation energy and frictional heat. The desorption endothermic effect and frictional heat effect are the dominant factors controlling the temperature variation of coal during the gestation process of outburst. The research achievements have significant theoretical significance and practical value for revealing the temperature evolution mechanism during the gestation process of coal and gas outburst, predicting coal and gas outburst, and protecting the atmospheric environment.

Optimization of nanoscale heat transport analysis of ternary hybrid nanofluid over three‐dimensional wedge geometry in magnetized environment

AbstractExponential space‐based heat source with shear‐thinning/thickening behavior offers innovative insights into the optimization of thermal transport process in complex systems, such as in the cooling of microelectronics, energy storage technologies, and biomedical devices, where accurate thermal control is critical. This study explores the investigation of an exponential space‐based heat source with effects of shear thinning/thickening behavior of a ternary infinite shear rate viscosity‐dependent Carreau water‐based nanofluid [Cu, Fe3O4, SiO2] over a three‐dimensional wedge in a magnetized environment. The interaction between heat transport and magnetic fields is explored through the behavior of the ternary nanofluid by classifying the both shear‐thinning and shear‐thickening effects. The incorporation of physical assumptions in the model gives the set of partial differential equations (PDEs) and similarity transformations are launched to convert them into ordinary differential equations (ODEs). Furthermore, bvp4c scheme is used to fetch the numerical solution. Temperature profile is increasing with exponential‐based source heat parameter due to a reduction in the rate of heat absorption by the fluid. Ternary nanofluids exhibit the highest rate of temperature increment due to the effects of multiple nanoparticles as compared to hybrid or single‐nanoparticle nanofluids. Rate of velocity decrement in ternary nanofluids compared to bi‐hybrid nanofluids and single‐particle nanofluids.

Simultaneous saccharification and fermentation for d-lactic acid production using a metabolically engineered Escherichia coli adapted to high temperature

BackgroundEscherichia coli JU15 is a metabolically engineered strain capable to metabolize C5 and C6 sugars with a high yield of d-lactic acid production at its optimal growth temperature (37 °C). The simultaneous saccharification and fermentation process allow to use lignocellulosic biomass as a cost-effective and high-yield strategy. However, this process requires microorganisms capable of growth at a temperature close to 50 °C, at which the activity of cellulolytic enzymes works efficiently.ResultsThe thermotolerant strain GT48 was generated by adaptive laboratory evolution in batch and chemostat cultures under temperature increments until 48 °C. The strain GT48 was able to grow and ferment glucose to d-lactate at 47 °C. It was found that a pH of 6.3 conciliated with GT48 growth and cellulase activity of a commercial cocktail. Hence, this pH was used for the SSF of a diluted acid-pretreated corn stover (DAPCS) at a solid load of 15% (w/w), 15 FPU/g-DAPCS, and 47 °C. Under such conditions, the strain GT48 exhibited remarkable performance, producing d-lactate at a level of 1.41, 1.42, and 1.48-fold higher in titer, productivity, and yield, respectively, compared to parental strain at 45 °C.ConclusionsIn general, our results show for the first time that a thermal-adapted strain of E. coli is capable of being used in the simultaneous saccharification and fermentation process without pre-saccharification stage at high temperatures.

Heat and cause-specific cardiopulmonary mortality in Germany: a case-crossover study using small-area assessment

High temperatures have been associated with increased mortality, with evidence reported predominately in large cities and for total cardiovascular or respiratory deaths. This case-crossover study examined heat-related cause-specific cardiopulmonary mortality and vulnerability factors using small-area data from Germany. We analyzed daily counts of cause-specific cardiopulmonary deaths from 380 German districts (2000-2016) and daily mean temperatures estimated by spatial-temporal models. We applied conditional quasi-Poisson regression using distributed lag nonlinear models to examine heat effects during May-September in each district and random-effects meta-analysis to pool the district-specific estimates. Potential individual- and district-level vulnerability factors were examined by subgroup analyses and meta-regressions, respectively. Heat was associated with increased mortality risks for all cardiopulmonary sub-causes. The relative risk (RR) of total cardiovascular and respiratory mortality for a temperature increment from the 75th to the 99th percentile was 1.24 (95% confidence interval: 1.23, 1.26) and 1.34 (1.30, 1.38), respectively. The RRs of cardiovascular sub-causes ranged from 1.16 (1.13, 1.19) for myocardial infarction to 1.32 (1.29, 1.36) for heart failure. For respiratory sub-causes, the RR was 1.27 (1.22, 1.31) for COPD and 1.49 (1.42, 1.57) for pneumonia. We observed greater susceptibility related to several individual- and district-level characteristics, e.g., among females or in highly urbanized districts. Heat vulnerability factors remained consistent between urban and rural areas. Our study highlights heat-related increases in cause-specific cardiopulmonary mortality across Germany and identifies key vulnerability factors, offering insights for improving public health practices to mitigate heat-related health impacts. European Union's Horizon 2020 research and innovation program; Helmholtz Associations Initiative and Networking Fund.

The Heat Transfer in Skin Tissues Under The General Two-Temperature Three-Phase-Lag Model of Heat Conduction with a Comparative Study

In this paper, a new and more general model of heat conduction that depends on the drift velocity due to thermomass motion assumption will be established and will be applied to the skin tissue. Four different heat conduction models will be incorporated into a unified equation of heat conduction: the Pennes, Vernotte-Cattaneo, dual-phase-lag of Tzou, and the general two-temperature three-phase-lag of Youssef. The governing partial differential equations of the general two-temperature three-phase-lag model of bioheat conduction will be implemented and solved directly in the domain of the Laplace transformation. The numerical solutions of the Laplace transform will be calculated by executing the Tzou iteration formula. The ramp-type heat on the surface of the skin tissue will be considered as thermal loading. The conductive and dynamic temperature increment reactions have been studied and discussed with different values of ramp-time heat, characteristic length, and drift velocity parameters. The novelty of this work is to introduce some comparisons of the four under-studied bioheat conduction models and show the differences between them in the figures. The numerical results show that the ramp-time heat, drift velocity, and characteristic length parameters have major impacts on the increment of both dynamical and conductive temperature distributions.

Wastewater Management as a Part of Solution for Water Resources Problem in Erbil City

In Erbil City, municipal wastewater (MWW) is disposed directly without any treatment processes in the natural environment water body and in some places used for irrigation purposes. Untreated MWW causes problems for the environment, and people's health. Water quantity and quality variation produce complications for water sources in Erbil City, Kurdistan Region-Iraq. There is a lack of performing MWW management fundamentals in the area as well. This research aimed to study the MWW management in Erbil City, presenting water resource difficulties and bringing about suitable solutions for the water resource problems, and also to highlight the risk for the poor Management. MWW Data on Erbil municipal (EMWW) water quality parameters were collected and analyzed for the study period (four months), beginning in October 2022 and ending in March 2023. Twelve EMWW quality parameters were captured and tested in the Laboratory, arranged, and compared with MWW disposal criteria and local standards. The following MWW parameters include pH, electrical conductivity (EC), total dissolved salts (TDS), chloride (CL), total solids (TS), total alkalinity, total acidity, chemical oxygen demand (COD), and colour. The results showed that Erbil's MWW characteristics in terms of temperatures ranged between 11-23 °C and in turn, affected biological species activities. Maximum PH value was 7.7. Total alkalinity found in the range from 140 to 178 mg/l. Chloride concentration results showed for October was 62 mg/l and the maximum value was 80 mg/l in November due to the increment in temperature and evaporation. The range of the COD values of sewage water for five months was 246 -773 mg. Erbil's MWW's moderate to medium strength may be treated and utilized for landscaping, fountains, and irrigation, minimizing the need for fresh water from resources like wells and surface water in the Greater Zab River.

The Influence of the Caputo Fractional Derivative on Time-Fractional Maxwell’s Equations of an Electromagnetic Infinite Body with a Cylindrical Cavity Under Four Different Thermoelastic Theorems

This paper introduces a new mathematical modeling of a thermoelastic and electromagnetic infinite body with a cylindrical cavity in the context of four different thermoelastic theorems; Green–Naghdi type-I, type-III, Lord–Shulman, and Moore–Gibson–Thompson. Due to the convergence of the four theories under study and the simplicity of putting them in a unified equation that includes these theories, the theories were studied together. The bunding plane of the cavity surface is subjected to ramp-type heat and is connected to a rigid foundation to stop the displacement. The novelty of this work is considering Maxwell’s time-fractional equations under the Caputo fractional derivative definition. Laplace transform techniques were utilized to obtain solutions by using a direct approach. The Laplace transform’s inversions were calculated using Tzou’s iteration method. The temperature increment, strain, displacement, stress, induced electric field, and induced magnetic field distributions were obtained numerically and represented in figures. The time-fractional parameter of Maxwell’s equations has a significant impact on all the mechanical studied functions and does not affect the thermal function. The time-fractional parameter of Maxwell’s equations works as a resistance to deformation, displacement, stress, and induced magnetic field distributions, while it acts as a catalyst to the induced electric field through the material.

Evaluation on tension-compression anisotropic behavior of recycled asphalt mixture

The utilization of recycled asphalt pavement (RAP) is the effective way to improve resource conservation and reduce energy consumption. The asphalt mixture is a kind of typical anisotropic pavement materials due to its heterogeneity in composition and microstructure. This could lead to the differences of mechanical response between the tensile and compressive direction. However, there are limited researches to study the effect of RAP on the tension-compression anisotropic behavior of asphalt mixture. The strength, modulus and fatigue resistance tests are carried out and different loading modes are adopted. The results show that the tension-compression anisotropic behavior is more prominent with the increase of RAP content. The regenerant served as a kind of typical additive could alleviate this effect. In addition, the result of dynamic modulus test shows that the tension-compression anisotropic behavior has an increasing trend with the decrease of frequency and the increment of temperature. The ranking of fatigue life is opposite for the direct tensile and compressive loading mode, and the fatigue life ratio of compression to tension also show positive relation with the RAP content. Due to the difference in the stress mode, the fatigue life between the indirect tensile loading and four-point bending loading also show opposite trend, and the indirect tensile fatigue life has a larger discreteness.

Mechanical properties of shale during pyrolysis: Atomic force microscopy and nano-indentation study

Quantitative characterization of the geo-mechanical properties of shale and organic matter (OM) holds paramount significance in the assessment of shale gas reserves and the design of hydraulic fracturing. However, the mechanical evolution processes during shale hydrocarbon generation and its influencing factors have received limited attention. This study examines the changes in shale mechanical properties during pyrolysis at high temperatures (415–600 °C) and high pressure (50–125 MPa) for mature to over-mature stages. The nanoindentation and in-situ AFM-QNM analysis are utilized to characterize the changes in mechanical properties during evolution. Subsequently, gas adsorption, Fourier Transform infrared spectroscopy (FTIR), and laser Raman spectroscopy (Raman) are used to investigate the factors influencing the mechanical properties of shale and the associated OM, and establish a model for the evolution of the mechanical properties. The results demonstrate that with increasing maturity, the overall Young's modulus of the bulk shale gradually increases from 42.8 GPa to 58.4 GPa for the temperature increment from 415 °C to 600 °C. During the thermal maturation process, the mesopore structure and quartz content of the shale significantly influence its mechanical properties. Young's modulus of OM shows an S-shaped trend, with variations in the micromechanical properties of OM corresponding to stages of hydrocarbon generation. In particular, two peaks of Young's modulus increase are observed during the mature and over-mature stages. In the mature stage, the aromatization of the kerogen leads to substantial detachment of aliphatic side chains and oxygenated functional groups, resulting in a higher degree of aromatization. This reduces the kerogen spacing and consequently increases the Young's modulus. In the over-matured stage, the process of aromatics condensation leads to the orientation and arrangement of aromatic rings, reducing the number of key site vacancies and crystal defects, thereby forming large aromatic clusters and significantly increasing the graphite-like structure. This study will facilitate the analysis of shale matrix deformation mechanisms at the microscale, providing a fundamental theoretical and scientific basis for shale fracturing design, exploration, and development.

Performance evaluation of solar dryer integrated with solar panel for drying of carrot (Daucus carota) vegetable

ABSTRACT Solar energy is a well-known and economically efficient energy source. Solar energy is harvested in two modes: one is direct and another is indirect. In the direct type, the global radiation is used directly to dry the food samples, while in indirect mode, solar energy is converted into electricity to operate the integrated exhaust fan for enhancement of the drying rate. Thermal analyses of the various components of the PVT hybrid dryer have been incorporated into this performance evaluation. Carrot has been chosen as a food sample because it has good moisture content and is used for nutritive purposes. The maximum ambient temperature has been monitored as 41°C at maximum global radiation conditions. The effect of the PVT system with solar dryer in both cases i.e. natural convection and forced convection have also been discussed in terms of temperature profiles of the drying chamber, sample temperature, and thermal efficiency. The thermal efficiency has been found as 55.3% for forced convection and 53.4% for natural convection. Similarly, a 3°C temperature increment has been found in food samples. Results have been supported and analyzed by the comparison between outcomes of natural and induced convection.

Towards a 2DEnVar surface data assimilation approach within the convective scale numerical weather prediction model AROME‐France

AbstractSurface data assimilation (DA) plays a key role in the initialisation of soil variables in coupled surface–atmosphere numerical weather prediction (NWP) models. Météo‐France, as many other NWP centres, uses an operational surface DA method based on an optimal interpolation (OI), implemented more than 30 years ago. The current surface DA system implemented at Météo‐France in the operational limited‐area AROME‐France model operates in two steps. First, a two‐dimensional OI method analyses the diagnostic screen‐level parameters, which are then used to initialise the prognostic soil variables according to a one‐dimensional OI method. This article presents the implementation and the results of a new two‐dimensional ensemble‐based variational (2DEnVar) system, using the object‐oriented prediction system framework, for the diagnostic screen‐level variable analyses (2‐m temperature and 2‐m relative humidity) within the AROME‐France model. These analysed variables are then used to initialise the soil temperature and soil moisture of the first and second soil layers. A two‐dimensional variational system is initially implemented and compared with an equivalent system that uses an OI surface analysis. The comparison of 2‐m temperature increments shows that the two systems behave in a similar way. From this two‐dimensional variational approach, a 2DEnVar scheme is developed and compared with the OI screen‐level analysis used operationally (reference system). The results are encouraging even though a degradation in forecast quality is noticed at short ranges for 2‐m temperature and 2‐m relative humidity. This is mainly due to a low spread near the surface in the ensemble‐based data assimilation that is used to compute background‐error covariances in 2DEnVar. Sensitivity tests have been performed to improve the initial version of the 2DEnVar scheme. A positive and significant impact is noticed when a multiplicative inflation is applied to the background perturbations coming from the ensemble‐based data assimilation for the computation of 2‐m temperature and 2‐m relative humidity background‐error covariances. Finally, when comparing the inflated 2DEnVar system with the reference, the two systems behave similarly. This suggests that the 2DEnVar scheme, based on ensemble statistics, is capable of properly reconstructing background‐error structures derived from the empirical correlations described in OI.

Variable density and heat generation impact on chemically reactive carreau nanofluid heat-mass transfer over stretching sheet with convective heat condition

The present study focuses on the physical significance of heat generation and chemical reaction on Carreau nanofluid with convective heat conditions. Heat transfer is characterized using convective boundary conditions. The governing partial differential equations (PDEs) are transformed into ordinary differential equations (ODEs) by using well define stream functions and similarity transformations. Using a shooting methodology, the Keller-box method with Newton Raphson scheme is used to elaborate the numerical solutions of physical phenomena. Utilizing a similar technique to find the impact of physical parameter such as the production of heat δ, the rate of reaction Λ, Biot numbers γ, Brownian motion variable Nb, the thermophoresis parameters Nt, the Weissenberg quantity We, Prandtl number Pr, and Lewis number Le on velocity profile, temperature profile and mass transmission profile are determined graphically. The skin-friction coefficient −f″(0), local Nusselt −θ′(0), and Sherwood numbers −ϕ′(0) are analyzed numerically. Increment in fluid velocity and slip temperature are depicted with high Biot number. Maximum magnitude of fluid temperature and fluid concentration function are depicted at high value of temperature dependent density. The magnitude of heat and mass transportation enhanced with maximum choice of Brownian motion.

Reliability analysis for running safety of vehicle on slab track via an improved second-order fourth-moment approach

The reliability assessment for running safety of vehicle on slab track under temperature action and seismic excitation is challenging due to the extensive computational efforts. This study proposes an improved second-order fourth-moment (ISOFM) approach for the reliability analysis for running safety of vehicle on slab track under temperature action and seismic excitation. The dimensionless limit state function (LSF) for running safety of vehicle on slab track is formulated considering four failure modes. The proposed ISOFM approach is verified by the Monte Carlo simulation (MCS) method. The proposed ISOFM approach greatly reduces the number of computations of nonlinear LSF. The merit of the proposed ISOFM approach lies in significantly enhancing the computation efficiency and precision of reliability considering nonlinear LSF with multi-failure modes. Additionally, the influences of temperature action and seismic excitation on the reliability for running safety of vehicle on slab track are discussed. The reliability for vehicle running safety decreases more significantly with the increment in overall temperature compared to the positive temperature gradient (PTG). The reliability for running safety of vehicle on slab track decreases nonlinearly with the increase of the earthquake intensity.

Dependence of martensitic stabilization on Ms temperature in Cu-Al-Ni shape memory alloys

The occurrence of martensitic stabilization shows a strong positive dependence on Ms temperature in Cu-Zn-Al alloys. Compared with Cu-Zn-Al alloys, Cu-Al-Ni alloys have a more excellent resistance to martensitic stabilization. However, whether the occurrence of martensitic stabilization is dependent on Ms temperature in Cu-Al-Ni alloys is still unknown. To clarify this question, we investigated the relationship between SME and Ms temperature in directly-quenched Cu-Al-Ni alloys. Results showed that the positive dependence of martensitic stabilization on Ms temperature indeed existed in directly-quenched Cu-Al-Ni alloys. The Cu-Al-Ni alloys with Ms≤488 K possess a good resistance to martensitic stabilization. For the directly-quenched Cu-Al-Ni alloys with remarkably higher than 488 K, they cannot obtain SME due to the occurrence of martensitic stabilization after recovery heating at <25 K/s. The original number of vacancies at martensite boundaries (Nvmb) rising with the increment in Ms temperature was responsible for the remarkable lowering in resistance to martensitic stabilization during the process of slow heating. To adjust the original Nvmb in alloys with remarkably high Ms temperature, we changed the Ms temperature through precipitating α phase. The precipitation of α phase can enrich the matrix with Al and Ni elements and thus decrease the Ms temperature. The reduction in Ms temperature to below ∼500 K significantly decreased the original Nvmb and improved the resistance to martensitic stabilization during the slow heating process.

Effects of temperature on Two-point statistical characteristics in turbulent jets

Abstract large eddy simulations are carried out for jets at Mach number 0.9, temperature ratio 2.0 and 3.4. Simulations are validated by comparing with experiments from literature. Two-point correlation- and coherence- functions are analyzed. Results show that the increment of jet temperature affects the decay rate of correlation functions. The correlation functions are analyzed both in space and time by employed a normalization method. The normalization coefficient is found changing with the temperature. Compared to spatial normalization coefficients, the time normalization coefficient is found more sensitive to the temperature. The coherence function is found asymmetric in the upstream and downstream of the reference point. The present attempt to construct an empirical model to normalize the coherence function, so as to provide reference for the study of acoustic field.

State-Space Approach to the Time-Fractional Maxwell’s Equations under Caputo Fractional Derivative of an Electromagnetic Half-Space under Four Different Thermoelastic Theorems

This paper introduces a new mathematical modelling method of a thermoelastic and electromagnetic half-space in the context of four different thermoelastic theorems: Green–Naghdi type-I, and type-III; Lord–Shulman; and Moore–Gibson–Thompson. The bunding plane of the half-space surface is subjected to ramp-type heat and traction-free. We consider that Maxwell’s time-fractional equations have been under Caputo’s fractional derivative definition, which is the novelty of this work. Laplace transform techniques are utilized to obtain solutions using the state-space approach. Laplace transform’s inversions were calculated using Tzou’s iteration method. The temperature increment, strain, displacement, stress, induced electric field, and induced magnetic field distributions were obtained numerically and are illustrated in figures. The time-fraction parameter of Maxwell’s equations had a major impact on all the studied functions. The time-fractional parameter of Maxwell’s equations worked as resistant to the changing of temperature, particle movement, and induced magnetic field, while it acted as a catalyst to the induced electric field through the material. Moreover, all the studied functions have different values in the context of the four studied theorems.

Effect of environmental factors on the mechanism of arsenic release from clay layers during natural compaction

Clay layers are presumed sources of original arsenic (As) in the groundwater of underlying aquifers. However, studies have focused less on the release mechanism of As from clay layers compared to well-studied As release from aquifers, especially during the natural compaction process of clay layers and its role in As mobilization. Herein, simulation experiments of the natural compaction of clay layers were performed at different compaction rates and temperatures. Hydrochemistry, parallel chemical extraction, and high-throughput sequencing of the full-length 16S rRNA gene were employed to investigate the release mechanism of As from clay layers during compaction. While the compaction rate and temperature were found to promote the release of As from clay sediments, increasing the compaction rate caused As to enter pore water through reductive dissolution from crystalline iron (hydr)oxides to ferrihydrite and very poorly crystalline goethite; Meanwhile, temperature increment only increased the microbial activity and did not alter the release mechanism of As. When the natural burial rate of clay layers was altered, the compaction rate has greater effect than temperature on As release from clay sediments.. Under natural compaction, the concentration of As transported to the groundwater by clay layers was found to be 43.58–116.70 μg/L. These results suggested that the contribution of the natural compaction of As-rich clay layers to the formation of high As groundwater in aquifers is underestimated.

Proportional increment of oxygen consumption, heart rate and core body temperature in the digesting Python bivittatus.

The Burmese python has a remarkable digestive physiology with large elevations of metabolic rate and heart rate following feeding. Here, we investigated the relationship between heart rate, oxygen consumption and core body temperature during digestion in five pythons (Python bivittatus) by implantation of data loggers. The snakes were placed in respirometers at 30±0.1°C for 26 days and voluntarily ingested three meals of different size, whilst heart rate, core body temperature and oxygen consumption rate were measured continuously. Both oxygen consumption and heart rate increased severalfold during digestion, and metabolic heat production increased core body temperature by 2°C, explaining 12% of the observed tachycardia. The rise in core body temperature means that standard metabolic rate increased during digestion, and we estimate that failure to account for core body temperature leads to a 4% overestimation of the specific dynamic action (SDA) response. Our study reveals a close correlation between oxygen consumption and heart rate during digestion, further supporting the use of heart rate as a proxy for metabolism.

Molecular Identification and Engineering a Salt-Tolerant GH11 Xylanase for Efficient Xylooligosaccharides Production.

This study identified a salt-tolerant GH11 xylanase, Xynst, which was isolated from a soil bacterium Bacillus sp. SC1 and can resist as high as 4 M NaCl. After rational design and high-throughput screening of site-directed mutant libraries, a double mutant W6F/Q7H with a 244% increase in catalytic activity and a 10 °C increment in optimal temperature was obtained. Both Xynst and W6F/Q7H xylanases were stimulated by high concentrations of salts. In particular, the activity of W6F/Q7H was more than eight times that of Xynst in the presence of 2 M NaCl at 65 °C. Kinetic parameters indicated they have the highest affinity for beechwood xylan (Km = 0.30 mg mL-1 for Xynst and 0.18 mg mL-1 for W6F/Q7H), and W6F/Q7H has very high catalytic efficiency (Kcat/Km = 15483.33 mL mg-1 s-1). Molecular dynamic simulation suggested that W6F/Q7H has a more compact overall structure, improved rigidity of the active pocket edge, and a flexible upper-end alpha helix. Hydrolysis of different xylans by W6F/Q7H released more xylooligosaccharides and yielded higher proportions of xylobiose and xylotriose than Xynst did. The conversion efficiencies of Xynst and W6F/Q7H on all tested xylans exceeded 20%, suggesting potential applications in the agricultural and food industries.