Unveiling the inherent physical-chemical dynamics: Direct measurements of hydrothermal fluid flow, heat, and nutrient outflow at the Tagoro submarine volcano (Canary Islands, Spain)

Tagoro is one of the few submarine volcanoes in the world that has been monitored since its early eruptive stage in 2011 to present day. After six multidisciplinary oceanographic cruises conducted between 2014 and 2023 to gather a comprehensive dataset of georeferenced video-imagery and in situ measurements of hydrothermal flow velocities and hydrothermal fluid samples, we provide a robust characterization of the ongoing hydrothermal fluid velocity, heat flux, and nutrient release, along with an accurate delimitation of the hydrothermal field area. Our results reveal that Tagoro hydrothermal system extends from the main hydrothermal crater up to the summit, covering an area of 7600 m2. This hydrothermal field comprises thousands of small individual vents, displaying diverse morphologies such as crevices and delicate chimney-like structures, irregularly scattered across the dominant diffuse venting surface. Hydrothermal fluid temperatures and velocities at the substratum level reveal a clustered spatial distribution, ranging from 21.0 to 33.3 °C and 1.6-26.8 cm min-1, respectively. Furthermore, our findings indicate a discernible correlation between hydrothermal fluid temperature and vent density, while significant differences were observed between velocities from diffuse and focused areas. Additionally, heat fluxes exceed 200 MW across the entire active region, with heat flux values ranging from 6.06 to 146.87 kW m-2 and dissolve inorganic nutrient concentrations exhibit significant enrichments, comparable to the magnitude of important nutrient sources in the area as upwelling systems or mesoscale structures.

Air quality impacts of observationally constrained biomass burning heat flux inputs

Biomass burning is a major contributor to ambient air pollution worldwide, and the accurate characterization of biomass burning plume behavior is an important consideration for air quality models that attempt to reproduce these emissions. Smoke plume injection height, or the vertical level into which the combustion emissions are released, is an important consideration for determining plume behavior, transport, and eventual impacts. This injection height is dependent on several fire properties, each with estimates and uncertainties in terms of historical fire emissions inventories. One such property is the fire heat flux, a fire property metric sometimes used to predict and parameterize plume injection heights in current chemical transport models. Although important for plume behavior, fire heat flux is difficult to predict and parameterize efficiently, and is therefore often held to fixed, constant values in these models, leading to potential model biases relative to real world conditions. In this study we collect observed heat flux estimates from satellite data products for three wildfire events over northern California and use these estimates in a regional chemical transport model to investigate and quantify the impacts of observationally constrained heat fluxes on the modeled injection height and downwind air quality. We find large differences between these observationally derived heat flux estimates and fixed model assumptions, with important implications for modeled behavior of plume dynamics and surface air quality impacts. Overall, we find that using observationally constrained heat flux estimates tends to reduce modeled injection heights for our chosen fires, resulting in large increases in surface particulate matter concentrations. While local wind conditions contribute to variability and additional uncertainties in the impacts of modified plume injection heights, we find observationally constrained heat fluxes to be an impactful and potentially useful tool towards the improvement of emissions inventory assumptions and parameterizations.

A molecular dynamics simulation of the effect of the toluene catalytic ratios and initial temperature on the catalytic combustion of air/methane inside a microchannel

METHODS

This research studied the effect of initial temperature (300-400K), and atomic percentage of toluene catalyst (1-10%) on the atomic and thermal performance of air/methane catalytic combustion. The present study was performed using molecular dynamics (MD) simulation.

CONTEXT

The results demonstrate that by increasing the initial temperature from 300 to 400 K, the maximum velocity and temperature increased from 0.52 Å/ps and 585 K to 0.72 Å/ ps and 629 K, respectively. Moreover, the heat flux, thermal conductivity, and combustion efficiency increased from 2020 W/m2, 1.45 W/mK, and 93% to 2208 W/m2, 1.55 W/mK, and 97% by increasing initial temperature to 400 K. On the other hand, by increasing the atomic percentage of toluene catalyst from 1% to 4%, the maximum velocity and temperature increased from 0.41Å/ps and 546 K to 0.49 Å/ ps and 573 K, respectively. Thermal conductivity and combustion efficiency increased from 1.451.22 W/mK and 77% to 1.33 W/mK and 89%. With further increasing of the catalyst to 10%, the thermal performance of sample declined. This decrease could be attributed to the agglomeration process, where an excessive amount of catalyst may lead to agglomeration, negatively affecting the structure's catalytic activity and overall thermal performance.

Investigating the temperature distribution behavior and flow parameters of argon fluid in a nanochannel with changing dimensions of the obstacle using the molecular dynamics (MD) method

This article, examines the flow of argon inside a nanochannel with respect to the molecular dynamics (MD) in the free molecular flow regime using LAMMPS software. The nanochannel is made of copper featuring a square cross-section and obstacles of varying dimensions and values. In this study, the flow of argon fluid is three-dimensional. To gain a deeper understanding of the effect of solid walls within the nanochannel and their influence on flow behavior, the research is simulated in a nanochannel with all side walls for the 3D model and without side walls for the 2D model. This research assesses the effect of the obstacles' dimensions and values on the nanochannel wall surface and areas above the wall surface. The total dimensions of all simulated two- and three-dimensional atomic structures with a square cross-section are assumed to be 60 × 60 × 100 Å3. and the presence of square obstacles (with dimensions of 8 × 8 × 8 Å3) and rectangular obstacles (with dimensions of 8 × 18 × 8 Å3) is examined. This study seeks to understand the influence on flow behavior, temperature distribution, density, heat flux, velocity, and thermal conductivity coefficient. This study is simulated using a time step of 1 fs for 10,000 time steps, involving approximately 10,000-15,000 argon and copper atoms. The results of this research indicate that obstacles with structures of P and R and larger dimensions increase the number of solid atoms exhibiting stronger attractive forces. Compared to a smooth nanochannel, the thermal exchange between fluid and solid atoms results in a density increase of 17.5 % and 17.3 %, respectively. On the other hand, in the 3D nanochannel, the sidewalls of the nanochannel have reduced the effect of the presence of R and P obstacles with larger dimensions, which comparing to a smooth nanochannel, have increased the density by 8.21 % and 7.53 %, respectively. The obstacles with different spatial positions (P and R structures) in the two-dimensional nanochannel cause a rise in the thermal conductivity coefficient. The P structure obstacles have a better effect on the thermal conductivity coefficient in the 2D nanochannel compared to the R structure. In the three-dimensional nanochannel, utilizing smaller obstacles proves to be more effective because it results in better atom distribution or temperature distribution due to increased atomic collisions in the central region compared to the wall regions.

Differential responses of CO2 and latent heat fluxes to climatic anomalies on two alpine grasslands on the northeastern Qinghai-Tibetan Plateau

Discrete extreme heat events, deluges, and droughts will become more frequent and disproportionately affect the processes and functions of grassland ecosystems. Here, we compared the responses of CO2 and heat fluxes to natural extreme events in 2016 in a lower alpine meadow and neighboring upper shrubland on the northeastern Qinghai-Tibetan Plateau. Unlike insensitive sensible heat flux, latent heat flux (LE) increased by 21.8 % in the meadow and by 56.4 % in the shrubland during a dry period and subsequent compound hot-dry period in August. Changes (Δ, data for 2016 minus the corresponding means from other years) in the heat flux at both sites were determined by changes in solar radiation (ΔSwin), as sufficient soil moisture was available. ΔLE was more sensitive to ΔSwin in the open-canopy shrubland, reflecting its greater capacity for evaporative cooling to buffer climate anomalies. CO2 fluxes responded weakly to extreme wet or dry events but strongly when those events were accompanied by exceptional heat. During single or compound hot events, the mean changes in total ecosystem respiration (ΔTER) increased by about 30 % in both grasslands, although ΔTER was more sensitive to changes in the topsoil temperature in the more productive meadow than in the shrubland. The mean changes in gross primary productivity (ΔGPP) fluctuated by <10 % in the warmer meadow but increased by 29.3 % in the cooler shrubland relative to the respective baseline, probably because of the differences in canopy structure and root depth and the consequent high-temperature stress on vegetation photosynthesis. The changes in net ecosystem CO2 exchange (ΔNEE) were significantly related to ΔTER in the meadow and increased by 55.8 %, whereas ΔNEE was controlled mainly by ΔGPP in the shrubland and decreased by 22.4 %. Overall, both alpine grasslands were resistant to rainfall anomalies but susceptible to exceptional warmth, with the differential responses being ascribed to canopy structure and root depth. Our results provide helpful insights based on which the carbon sequestration and water-holding functions of alpine grasslands during future climate change can be predicted.

Estimating inputs for dispersion modeling in mobile platform applications

Mobile monitoring platforms (MMP) are popular in air quality studies. One application of MMP is in estimating pollutant emissions from area sources. The MMP is used to measure concentrations of the relevant species at several locations around the area source, while the associated meteorological information is measured at the same time. Emissions from the area source are inferred by fitting the measured concentrations to estimates from dispersion models. These models require meteorological inputs, such as the kinematic heat flux and the surface friction velocity, that are best computed with measurements of time resolved velocity and temperature made with 3-D sonic anemometers. Because the setting up and dismantling of a 3-D sonic anemometer is not compatible with the necessary mobility of the MMP, it is useful to use alternative instrumentation and methods that provide accurate estimates of these inputs. In this study, we demonstrate such a method based on measurements of horizontal wind speed and temperature fluctuations at a single height. The method was evaluated by comparing methane emissions from a dairy manure lagoon inferred from a dispersion model that uses modeled meteorological inputs to those inferred from measurements with 3-D sonic anemometers. The emission estimates from the modeled meteorological inputs were close to those based on measurements made with 3-D sonic anemometers. We then demonstrate how this approach can be adapted for mobile platform applications by showing that winds measured using a 2-D sonic anemometer and temperature fluctuations measured with a bead thermistor, which can all be carried or mounted on a MMP, yields results that are close to those from a 3-D sonic anemometer.

Numerical analysis of heat flux passing through an anti-theft door armed by phase change materials

The use of phase change materials (PCMs) in buildings is considered an effective way to reduce building heat flux and cooling input. In this study, a south-facing anti-theft door with PCM layer was simulated in hot summer weather in Rafsanjan city. The main purpose was decreasing the heat flux to buildings due to high temperatures and direct sunlight. Boundary conditions are set for the outside environment using local meteorological data, while indoor temperature is set at a constant degree (25 °C). Simulation studies were performed by changing the various materials inside the door and also by changing the type, thickness, and position of PCMs in different parts of the door. It was found that the use of PCMs along with a layer of extruded polystyrene commonly used in anti-theft doors can have up to 50% increased effect in reducing the heat transfer flux over a day compared with the conventional case.

Study on decomposition and by-products formation mechanism of urea solution impinging on heated plate in SCR system

Selective catalytic reduction technology is one of the most effective methods to control NOx emissions from diesel engines. However, the generation of solid urea and by-products, which will lead to the incomplete decomposition of urea and reduce NOx reduction efficiency. The accumulation of deposits will also affect the back pressure and even block the catalyst, causing a vicious cycle. In this paper, a numerical model coupled with a detailed decomposition mechanism of urea was established. Based on this model, four heat transfer methods and chemical reactions in the film were calculated. The results show that the main heat transfer methods between the film and the plate are conduction and evaporation, both of which have maximum values higher than 10⁷ W/m². The mass of the film varies with heat flux can be divided into four stages. In the first stage, the film forms rapidly, and intense heat exchange occurs. In the second stage, the film increases slowly and the decomposition mass of urea increases. The main component of the film is solid urea. In the third stage, the solid urea mass begins to decrease. In the fourth stage, film mass decreases, and a large amount of urea is decomposed. The main byproduct of urea decomposition is biuret in the first three stages and cyanuric acid in the fourth stage. The solid urea and byproducts are mainly distributed in regions with low heat flux. With an increase in the initial plate temperature, the heat flux increases, the film and solid urea masses decrease, the byproducts appear earlier and their mass increases faster. When the temperature is 523 K, 528 K, and 533 K, the maximums of biuret mass occur at about 3.1s, 1.4s and 0.5s, respectively. The present work provides guidance understanding the relationship between heat transfer characteristics and byproducts formation of urea decomposition.

Notch ankyrin domain: evolutionary rise of a thermodynamic sensor

Notch signalling pathway plays a key role in metazoan biology by contributing to resolution of binary decisions in the life cycle of cells during development. Outcomes such as proliferation/differentiation dichotomy are resolved by transcriptional remodelling that follows a switch from Notch^on to Notch^off state, characterised by dissociation of Notch intracellular domain (NICD) from DNA-bound RBPJ. Here we provide evidence that transitioning to the Notch^off state is regulated by heat flux, a phenomenon that aligns resolution of fate dichotomies to mitochondrial activity. A combination of phylogenetic analysis and computational biochemistry was utilised to disclose structural adaptations of Notch1 ankyrin domain that enabled function as a sensor of heat flux. We then employed DNA-based micro-thermography to measure heat flux during brain development, followed by analysis in vitro of the temperature-dependent behaviour of Notch1 in mouse neural progenitor cells. The structural capacity of NICD to operate as a thermodynamic sensor in metazoans stems from characteristic enrichment of charged acidic amino acids in β-hairpins of the ankyrin domain that amplify destabilising inter-residue electrostatic interactions and render the domain thermolabile. The instability emerges upon mitochondrial activity which raises the perinuclear and nuclear temperatures to 50 °C and 39 °C, respectively, leading to destabilization of Notch1 transcriptional complex and transitioning to the Notch^off state. Notch1 functions a metazoan thermodynamic sensor that is switched on by intercellular contacts, inputs heat flux as a proxy for mitochondrial activity in the Notch^on state via the ankyrin domain and is eventually switched off in a temperature-dependent manner.

Spatial Pattern and Land Surface Features Associated with Cloud-to-Ground Lightning in Bangladesh: An Exploratory Study

Severe weather events such as lightning appear to be a significant threat to humans and property in South Asia, an area known for intense convective activity directly related to the tropical climate of these areas. The current study was conducted in Bangladesh and examined the association between cloud-to-ground (CG) lightning and ground surface properties, with the aim of improving existing knowledge regarding this phenomenon. GLD360 data from 2015 to 2020 were used to describe the seasonal lightning climatology. Elevation, land use and land cover, vegetation and surface heat flux data were used to examine all land surface features possibly associated with CG lightning occurrence. Hot and cold spot spatial patterning was calculated using local indicators of spatial association. Results indicated a strong CG lightning seasonality. CG stroke density varied considerably across seasons with the pre-monsoon exhibiting the highest density. This was followed by occurrences in the monsoon season. The March-June period experienced 73% of the total observed. Elevation appeared to influence the post-monsoon CG stroke, however, its role in the other seasons was more difficult to define. The land cover/lightning index indicated that waterbodies and herbaceous wetlands had more influence than other land cover types, both during the day and at night, and it appeared that latent heat flux played a major role. The CG stroke hot and cold spot locations varied diurnally. The findings suggest that large-scale irrigation practices, especially during the pre-monsoon months, can influence the observed spatiotemporal pattern. The production of hotspot maps could be an initial step in the development of a reliable lightning monitoring system and play a part in increasing public awareness of this issue.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s41748-022-00310-4.

Analysis of nasal air conditioning in subjects with unilateral cleft lip nasal deformity

This study evaluated the impact of unilateral cleft lip nasal deformity (uCLND) on the ability of the nasal passages to warm and humidify inspired environmental air using computational fluid dynamics (CFD) modeling. Nasal air conditioning was simulated at resting inspiration in ten individuals with uCLND and seven individuals with normal anatomy. The overall heat and water transfer through nasal mucosa was significantly greater (p = 0.02 for both heat and moisture fluxes) on the non-cleft side than on the cleft side. Unilateral median and interquartile range (IQR) for heat flux (W/m²) was 190.3 (IQR 59.9) on the non-cleft side, 160.9 (IQR 105.0) on the cleft side, and 170.7 (IQR 87.8) for normal subjects. For moisture flux (mg/(s·m²), they were 357.4 (IQR 112.9), 298.7 (IQR 200.3) and 320.8 (IQR 173.0), respectively. Significant differences of SAHF50 between cleft side of uCLND and normal existed except for anterior region. Nevertheless, air conditioning ability in subjects with uCLND was generally comparable to that of normal subjects.

Numerical data on heat flux of a novel controlled-temperature double skin façade

Hourly heat flux for variant boundary conditions of a novel controlled-temperature double skin façade (DSF) building element in a two- dimensional time- dependent study was determined. The building element is subjected to boundary conditions, characterizing different orientations (azimuth 0°, 90°, 180°, 270°) and climatic conditions of the four seasons. This data article provides detailed numerical data on the hourly heat flux, temperatures attained at the exterior and within the building element for six different geometries and for the variant boundary conditions under study. The external boundary conditions were determined with the use of the PVGIS tool, corrected in accordance to the sol-air temperature equation. The numerical simulation studies were performed with the use of the computational fluid dynamics (CFD) tool Comsol Multiphysics [2].

Thermal performance of brick and stone masonry: Cumulative heat flux dataset for main orientations and under diverse seasonal conditions

This dataset consists of the hourly heat flux for four seasons and orientations of 15 different construction configurations of brick and stone masonry combined with insulation system solutions. The analysis was conducted with the use of Finite Element Modelling (FEM). The development of the models and the investigation of their thermal performance was conducted with the use of thermal modelling and numerical simulation analysis with COMSOL Multiphysics. For this purpose, a transient 2D multi- dimensional, time- dependent simulation model on finite elements was developed. The governing equations of heat transfer were considered as well as the convection and radiation heat transfer coefficients in accordance to the ISO 6946:2017 [1].

A case study of Chlorophyll a response to tropical cyclone Wind Pump considering Kuroshio invasion and air-sea heat exchange

New evidences provided that the tropical cyclone (TC) Linfa in 2015 induced looping path of Kuroshio invasion into the northeastern South China Sea (NESCS) through the northwestern Luzon Strait (LS), based on the in-situ measurements, satellite data and model output data. This TC-enhanced Kuroshio invasion with low nutrients and denser waters suppressed the TC "Wind Pump" induced upwelling and nutrients uptake, and therefore inhibited the Chlorophyll a concentration (Chl-a) increase from surface to ~50 m in the open ocean of the NESCS. The TC-induced Kuroshio invasion promoted the generation of the strong cyclonic eddy to its left side where weak Ekman Pumping Velocity was observed. This enhancing cyclonic eddy then dominated the nutrients uplift and increased the surface and subsurface (0-50 m) Chl-a through eddy pumping rather than Ekman Pumping. The TC-declined anti-cyclonic eddy, which shoaled the Mixed Layer Depth (MLD), benefited to the nutrient uptake through TC-induced upwelling and thereby increased the surface Chl-a and raised the Chl-a Maximum Layer (CML) to ~20 m over the southwestern LS. The temporal Chl-a variations were also influenced by TC intensities and biochemical processes. The air-sea heat budget analysis indicated that, the air-sea heat exchange contributed to nearly 80% of the sea surface cooling (SST cooling) over the northwestern LS with Kuroshio invasion, while eddy-induced upwelling dominated the SST cooling over the western LS, and the wind-driven upwelling (and mixing) controlled the SST cooling over the southwestern LS. These different formations of SST cooling then played important role in Chl-a variations. This study is the first case of TC "Wind Pump" induced Chl-a variations considering air-sea heat exchange, Kuroshio invasion and mesoscale eddies over LS, which would help to evaluate the influence of TCs over the other major heat transport arteries of the world ocean: The Gulf Stream area.

Calculation of the thermal conductivity of human serum albumin (HSA) with equilibrium/non-equilibrium molecular dynamics approaches

BACKGROUND AND OBJECTIVE

Human serum albumin (HSA) controls the flow of numerous chemical structures and molecules in the cardiovascular system. So, thermal conductivity of this atomic compound is important in medicinal applications.

METHODS

In this work, the thermal conductivity of HSA is calculated with equilibrium/non-equilibrium molecular dynamic approaches. In these methods each HSA molecule is exactly represented by C, N, O and S atoms and their implemented dreiding potential. Finally by using Green-Kubo and Fourier's law the thermal conductivity of HSA/H₂O mixture is calculated.

RESULTS

Our calculated rates for thermal conductivity via equilibrium/non-equilibrium molecular dynamics methods are 0.496 W/m K and 0.448 W/m K, respectively. The calculated thermal conductivity for this structure was very close to the thermal conductivity calculated for water molecules which were reported by other research groups. Furthermore our simulated structures show that thermal conductivity of HAS/H₂O mixtures has inverse relation with HAS molecules numbers and temperature of simulated atomic structures.

CONCLUSIONS

Comparing thermal conductivity from equilibrium/non-equilibrium molecular dynamics methods for HAS/H₂O shows that EMD and NEMD results are reliable and EMD calculated results are higher than NEMD results.

Thermoregulatory costs in molting Antarctic Weddell seals: impacts of physiological and environmental conditions: Themed Issue Article: Conservation of Southern Hemisphere Mammals in a Changing World

For polar marine mammals, the energetic cost of thermoregulation depends on ambient conditions in the highly variable surrounding environment. Heat conservation strategies used by pinnipeds to reduce total heat loss include small surface area to volume ratios, the ability to limit perfusion and thick subcutaneous blubber layers. There are limits to how cool the skin surface may remain without compromising function, especially during the annual pelage molt, when hair and skin are replaced. To determine if actively molting seals incur higher thermoregulatory costs, surface temperature (ST) and heat flux (HF) were measured in 93 adult female Weddell seals (Leptonychotes weddellii) both prior to and during the active molting period using direct sensors and infrared imaging. Linear mixed-effect models revealed that ST increased significantly with increased ambient temperature and decreased wind speed (contributing 44.6 and 41.7% of the attributed variance, respectively). Seal STs were not impacted by molt status, but were maintained at 11.2 ± 0.3°C warmer than the ambient temperature. Infrared imaging results averaged 15.1 ± 1.4°C warmer than direct ST measurements. In contrast, HF was significantly higher in seals in early molting stages compared to the pre-molt season ( P < 0.001) and molt status accounted for 66.5% of the variance in HF. Thermoregulatory costs calculated from estimated basal metabolic rate and measured HF were more than double for molting seals as compared to those in pre-molt. This suggests that perfusion is increased during molt to support follicle development, despite the increased energetic costs associated with higher HF rates. Because ST, HF and thermoregulatory costs are strongly influenced by ambient conditions, molt timing is likely under selective pressure to occur during the warmest period of the year. Shifts in environmental conditions that delay molt phenology or increase HF rates could negatively impact seal populations by further increasing thermoregulatory costs.

Investigation of thermal properties of DNA structure with precise atomic arrangement via equilibrium and non-equilibrium molecular dynamics approaches

BACKGROUND AND OBJECTIVE

Thermal conductivity of Deoxyribonucleic acid molecules is important for nanotechnology applications. Theoretical simulations based on simple models predict thermal conductivity for these molecular structures.

METHODS

In this work, we calculate the thermal properties of Deoxyribonucleic acid with precise atomic arrangement via equilibrium and non-equilibrium molecular dynamics approaches. In these methods, each Deoxyribonucleic acid molecule is represented by C, N, O, and P atoms and implemented dreidng potential to describe their atomic interactions.

RESULTS

Our calculated rate for thermal conductivity via equilibrium and non-equilibrium molecular dynamics methods is 0.381 W/m K and 0.373 W/m K, respectively. By comparing results from these two methods, it was found that the results from equilibrium and non-equilibrium molecular dynamics methods are identical, approximately. On the other hand, the number of DNA molecules and the equilibrium temperature of the simulated structures were important factors in their thermal conductivity rates, and their thermal conductivity was calculated at 0.323 W/m K-0.381 W/m K intervals for equilibrium and 0.303 W/m K-0.373 W/m K interval for non-equilibrium calculations.

CONCLUSIONS

These results are in good agreement with thermal conductivity calculation with other research groups.

Geometry and airflow dynamics analysis in the nasal cavity during inhalation

BACKGROUND

A major issue among computational respiratory studies is the wide variety of nasal morphologies being studied, caused by both inter-population and inter-subject variations.

METHOD

Six nasal cavity geometries exhibiting diverse geometry variations were subjected to steady inhalation flow rate of 15L/min. to determine if any consistent flow behaviour could be found.

FINDINGS

Despite vastly different geometries we were able to identify consistent flow patterns including relatively high velocity in the nasal valve region, followed by flow continuing predominantly in the inferior half of the airway. We also found conformity among models where the inhaled air reached a near-conditioned state by the middle of the nasal cavity. Air from the front of the face reached the olfactory regions while air from the lateral sides of the face moved through the inferior half of the nasal cavity.

INTERPRETATION

The ability to predict gross flow features provides a baseline flow field to compare against. This contributes towards establishing well defined flow predictions and be used as a comparison for future larger studies.

Heat flux in manatees: an individual matter and a novel approach to assess and monitor the thermal state of Florida manatees (Trichechus manatus latirostris)

Florida manatees (Trichechus manatus latirostris) possess an unusual suite of adaptations to accommodate both a fully aquatic lifestyle and an herbivorous diet, including a low metabolic rate and a very limited thermoneutral zone. Their relatively high lower critical temperature of around 20 °C suggests strong sensitivity to cold, thereby limiting their distribution to tropical and subtropical waters. "Cold stress syndrome" affects and kills Florida manatees every year during intense or prolonged cold weather, posing one of the major threats to manatees. However, knowledge regarding manatee thermoregulation is sparse, but essential for effective conservation and management of this threatened species. We measured heat flux in two captive Florida manatees at multiple times of the year, at 41 sites distributed across the entire body surface of each manatee. Heat flux differed significantly between individuals, and among body sites and times of the year. The pectoral flippers and axillae were identified as areas with highest heat exchange. Despite exposure to constant water temperature throughout the year, the manatees in this study had significantly lower heat flux in winter than in summer. We used the measured heat flux values to calculate total heat dissipation in individual manatees. The values estimated this way correspond well with the low metabolic rates estimated in previous studies, confirming the reliability of our novel approach. Our method provides simple and useful options for enhancing manatee welfare by monitoring the animals' thermal state during potentially stressful activities such as during medical treatment, capture restraints and transportation.

Experimental and numerical study of heat transfer through a synchronous belt transmission type AT10

In most industrial applications, the re-use of belts in power transmissions continues to increase and invade the market especially in automobiles where various types of belts are used. For this purpose, the belt manufacturers are aware of the importance and the valuable advantages of this transmission member and put all their efforts to develop and improve its geometrical and mechanical characteristics in order to achieve an optimal service life. Indeed, this article is devoted to an experimental and numerical thermal study of a toothed belt transmission type AT10. The tests were carried out on an original derrick of test for the purpose of measuring belt and pulley temperatures, detector devices and data acquisitions will also be described. Further, we have developed a model that calculates the heat flux through our pulley-belt transmission. The results will be synthesized to make a comparison between two thermal fluxes. The first is determined from our mathematical model and the second is calculated using the thermal simulation of this belt pulley transmission. Finally, a discussion of the results, which will allow us to fully understand this thermal phenomenon.

Impact of elevated carbon dioxide on soil heat storage and heat flux under unheated low-tunnels conditions

Suboptimal regimes of air and soil temperature usually occur under unheated low-tunnels during winter crop cycles. CO2 is one of the most important gases linked to climate change and posing challenge to the current agricultural productivity. Field experiment was conducted in unheated low-tunnels (10.0 m long, 1.5 m wide and 1.0 m high) during winter and spring periods to evaluate the increasing CO2 concentration (352, 709, 1063, 1407, and 1761 ppm) on net radiation budget, soil-air thermal regime and pepper plants growth development and yield. CO2 was injected into each hollow space of the tunnel double-layer transparent polyethylene covers. Recorded integral net longwave radiation increased from 524.81 to 1111.84 Wm(-2) on January when CO2 concentration increased from 352 to 1761 ppm. A similar trend was recorded on February. Moreover, minimum soil surface and air temperatures were markedly increased from -1.3 and -6.8 °C to 3.4 and 0.6 °C, when CO2 concentration increased from 352 to 1761 ppm. Additionally, soil heat flux as well as soil heat storage increased with increasing CO2 concentrations accordingly. Increasing the tunnel minimum air and soil temperatures with the CO2 concentration treatments 1063, 1407 and 1761 ppm reflected in a significant pepper yield (3.19, 5.06 and 6.13 kg m(-2)) due to the modification of the surrounding plants microenvironment and prevented pepper plants from freezing and the accelerated the plant growth. On the contrary, the drop of minimum air and soil temperatures to freezing levels with the CO2 concentration treatments 352 and 709 ppm resulted in the deterioration of pepper plants development during the early growth stages on January.

Characterizing human nasal airflow physiologic variables by nasal index

Although variations in nasal index (NI) have been reported to represent adaptation to climatic conditions, assessments of NI with airflow variables have not been rigorously investigated. This study uses computational fluid dynamics modeling to investigate the relationship between NI and airflow variables in 16 subjects with normal nasal anatomy. Airflow simulations were conducted under constant inspiratory pressure. Nasal resistance (NR) against NI showed weak association from nostrils to anterior inferior turbinate (R(2)=0.26) and nostril to choanae (R(2)=0.12). NI accounted for 38% and 41% of the respective variation in wall shear stress (WSS) and heat flux (HF) at the nasal vestibule, and 52% and 49% of variability in WSS and HF across the entire nose. HF and WSS had strong correlation with NI<80, and weakly correlated with NI>80; these differences in HF and WSS for NI<80 and NI>80 were not statistically significant. Results suggest strong relationship between NI and both WSS and HF but not NR, particularly in subjects with NI<80.

Spatial environmental heterogeneity affects plant growth and thermal performance on a green roof

Green roofs provide ecosystem services, including stormwater retention and reductions in heat transfer through the roof. Microclimates, as well as designed features of green roofs, such as substrate and vegetation, affect the magnitude of these services. Many green roofs are partially shaded by surrounding buildings, but the effects of this within-roof spatial environmental heterogeneity on thermal performance and other ecosystem services have not been examined. We quantified the effects of spatial heterogeneity in solar radiation, substrate depth and other variables affected by these drivers on vegetation and ecosystem services in an extensive green roof. Spatial heterogeneity in substrate depth and insolation were correlated with differential growth, survival and flowering in two focal plant species. These effects were likely driven by the resulting spatial heterogeneity in substrate temperature and moisture content. Thermal performance (indicated by heat flux and substrate temperature) was influenced by spatial heterogeneity in vegetation cover and substrate depth. Areas with less insolation were cooler in summer and had greater substrate moisture, leading to more favorable conditions for plant growth and survival. Spatial variation in substrate moisture (7%-26% volumetric moisture content) and temperature (21°C-36°C) during hot sunny conditions in summer could cause large differences in stormwater retention and heat flux within a single green roof. Shaded areas promote smaller heat fluxes through the roof, leading to energy savings, but lower evapotranspiration in these areas should reduce stormwater retention capacity. Spatial heterogeneity can thus result in trade-offs between different ecosystem services. The effects of these spatial heterogeneities are likely widespread in green roofs. Structures that provide shelter from sun and wind may be productively utilized to design higher functioning green roofs and increase biodiversity by providing habitat heterogeneity.

Computational simulation of temperature and velocity distribution in human upper respiratory airway during inhalation of hot air

The present study provides an accurate simulation of velocity and temperature distributions of inhalation thermal injury in a human upper airway, including vestibule, nasal cavity, paranasal sinuses, nasopharynx, oropharynx, larynx, and upper part of main bronchus. To this end, a series of CT scan images, taken from an adult woman, was used to construct a three dimensional model. The airway walls temperature was adjusted according to existing in vivo temperature measurements. Also, in order to cover all breathing activities, five different breathing flow rates (10, 15, 20, 30, and 40 l/min) and different ambient air temperatures (100, 200, 300, 400, and 500 °C) were studied. Different flow regimes, including laminar, transitional, and turbulence were considered and the simulations were validated using reliable experimental data. The results show that nostrils, vestibule, and nasal cavity are damaged more than other part of airway. Finally, In order to obtain the heat flux through the walls, correlations for Nusselt number for each individual parts of airway (vestibule, main upper airway, nasopharynx etc.,) are proposed.

Spatial resolution of anthropogenic heat fluxes into urban aquifers

Urban heat islands in the subsurface contain large quantities of energy in the form of elevated groundwater temperatures caused by anthropogenic heat fluxes (AHFS) into the subsurface. The objective of this study is to quantify these AHFS and the heat flow they generate in two German cities, Karlsruhe and Cologne. Thus, statistical and spatial analytical heat flux models were developed for both cities. The models include the spatial representation of various sources of AHFS: (1) elevated ground surface temperatures, (2) basements, (3) sewage systems, (4) sewage leakage, (5) subway tunnels, and (6) district heating networks. The results show that the district heating networks induce the largest AHFS with values greater than 60 W/m(2) and one order of magnitude higher than fluxes from other sources. A covariance analysis indicates that the spatial distribution of the total flux depends mainly on the thermal gradient in the unsaturated zone. On a citywide scale, basements and elevated ground surface temperatures are the dominant sources of heat flow. Overall, 2.1 PJ/a and 1.0 PJ/a of heat are accumulated on average in Karlsruhe and the western part of Cologne, respectively. Extracting this anthropogenically originated energy could sustainably supply significant parts of the urban heating demand. Furthermore, using this heat could also keep groundwater temperatures from rising further.