Region Of Temperature Gradient Research Articles

Circumpolar and Regional Seascape Drivers of Genomic Variation in a Southern Ocean Octopus.

Understanding how ecological, environmental and geographic features influence population genetic patterns provides crucial insights into a species' evolutionary history, as well as their vulnerability or resilience under climate change. In the Southern Ocean, population genetic variation is influenced across multiple spatial scales ranging from circum-Antarctic, which encompasses the entire continent, to regional, with varying levels of geographic separation. However, comprehensive analyses testing the relative importance of different environmental and geographic variables on genomic variation across these scales are generally lacking in the Southern Ocean. Here, we examine genome-wide single nucleotide polymorphisms of the Southern Ocean octopus Pareledone turqueti across the Scotia Sea and the Antarctic continental shelf, at depths between 102 and 1342 m, throughout most of this species' range. The circumpolar distribution of P. turqueti is biogeographically structured with a clear signature of isolation-by-geographical distance, but with long-distance genetic connectivity also detected between East and West Antarctica. Genomic variation of P. turqueti was also associated with bottom water temperature at a circumpolar scale, driven by a genotype-temperature association with the warmer sub-Antarctic Shag Rocks and South Georgia. Within the Scotia Sea, geographic distance, oxygen and fine-scale isolation-by-water depth were apparent drivers of genomic variation at regional scales. Putative positive selection of haemocyanin (oxygen transport protein), calcium ion transport and genes linked to RNA modification, detected within the Scotia Sea, suggest physiological adaptation to the regional sharp temperature gradient (~0-+2°C). Overall, we identified seascape drivers of genomic variation in the Southern Ocean at circumpolar and regional scales in P. turqueti and contextualised the role of environmental adaptations in the Southern Ocean.

The interior of Uranus

We present improved empirical density profiles of Uranus and interpret them in terms of their temperature and composition using a new random algorithm. The algorithm to determine the temperature and composition is agnostic with respect to the temperature gradient in non-isentropic regions and chooses amongst all possible gradients randomly that are stable against convection and correspond to an Equation of State (EoS) compatible composition. Our empirical models are based on an efficient implementation of the Theory of Figures (ToF) up to tenth order including a proper treatment of the atmosphere. The accuracy of tenth order ToF enables us to present accurate calculations of the gravitational moments of Uranus up to J14: J6 = (5.3078 ± 0.3312) 10−7, J8 = (−1.1114 ± 0.1391) 10−8, J10 = (2.8616 ± 0.5466) 10−10, J12 = (−8.4684 ± 2.0889) 10−12, and J14 = (2.7508 ± 0.7944) 10−13. We consider two interior models of Uranus that differ with respect to the maximal number of materials allowed per layer of Uranus (three versus four composition components). The case with three materials does not allow Hydrogen and Helium (H-He) in deeper parts of Uranus and results in a higher water (H2O) abundance which leads to lower central temperatures. On the other hand, the models with four materials allow H-He to be mixed into the deeper interior and lead to rock-dominated solutions. We find that these four composition components’ models are less reliable due to the underlying empirical models’ incompatibility with realistic Brunt frequencies. Most of our models are found to be either purely convective with the exception of boundary layers, or only convective in the outermost region above ~80% of the planets’ radius rU. Almost all of our models possess a region ranging between ~(0.75–0.9) rU that is convective and consists of ionic H2O which could explain the generation of Uranus’ magnetic field.

Analysis of climate change and climate variability impacts on coastal storms induced by extratropical cyclones: a case study of the August 2015 storm in central Chile

ABSTRACT The projected increase in coastal risk requires a reevaluation of coastal risk reduction strategies. A multi-model approach is proposed to examine the variability of coastal storms influenced by climate change and El Niño Southern Oscillation (ENSO). To this end, the historic coastal storm of August 8 2015, resulting from a local extratropical cyclone (ETC) off the central Chilean coast, was analyzed through the coupling of the WRF atmospheric model, Delft3D FM (D-FLOW and D-WAVE modules), and EOT20 astronomical tide model. The results show that the characteristics of local ETCs are susceptible to regional temperature gradients associated with climate change and ENSO. The coastal storm of August 8 2015, presented a decrease in wave height and counterclockwise rotation of wave direction along the Chilean coast under the climate change scenario. Meanwhile, the ENSO scenarios under cold conditions generated a ETC track’s displacement toward the north, causing both an increase in wave height along the coast of the Antofagasta and Atacama regions and a decrease in wave height in the Valparaíso, O’Higgins, and Maule regions. Findings from this study emphasize the importance of considering dynamic design for coastal structures rather than traditional methods to adapt to changing storm patterns.

Inter-ELM pedestal turbulence dynamics dependence on q95 and temperature gradient

A series of dedicated experiments from the DIII-D tokamak provide spatially and temporally resolved measurements of electron density and temperature, and multiscale and multichannel fluctuations over a wide range of conditions. Measurements of long wavelength density fluctuations in the type-I ELMing H-mode pedestals routinely reveal a coexistence of multiple instabilities that exhibit dramatic different dynamic behaviors as q95 and temperature gradients are varied, apparently responsible for limiting pedestal temperature profiles. Two distinct frequency bands of density fluctuations are modulated by an ELM cycle with frequency above 200 kHz propagating in the electron diamagnetic direction in the lab frame (electron mode) and below 200 kHz propagating in the ion diamagnetic direction (ion mode). The electron mode amplitude peaks near the electron temperature gradient region and increases with q95 which seems to be correlated with the increased χe at higher q95, similar to the characteristics expected for the micro-tearing mode (MTM). At higher q95, during the inter-ELM period, the ion mode decays at the later phase of the ELM cycle. Consistently, the poloidal correlation length of the ion mode is also found to reduce, which suggests the possible E × B flow shear suppression of the ion mode at the later phase of the ELM cycle as the Er well recovers. In contrast, the electron mode grows during the ELM cycle and reaches saturation at around 50%–60% of the ELM period. Linear gyrokinetic simulations find the MTMs to be the most unstable mode in the pedestal electron temperature gradient region. The higher q95 and lower magnetic shear destabilize the MTMs. These observations provide key insights into the underlying physics of multifield properties and a rich dataset of experimental ‘fingerprints’ that enable new tests of theoretical pedestal models and lead to the development of a predictive model for pedestal formation on the ITER and future burning plasma experiments.

Thermal Field Simulation and Optimization of PbF2 Single Crystal Growth by the Bridgman Method

PbF2 single crystals are usually grown in the temperature gradient region by the Bridgman–Stockbarger method. Temperature distribution during the growth process is particularly important for the preparation of high-quality crystals. In this study, the temperature field during the growth of the PbF2 single crystals was simulated based on the finite element method. The temperature distribution and temperature gradient changes in the crucible were investigated at different growth stages, including the seeding, shouldering, and iso-diameters stages. The calculated results show that as the crucible position continues downward during the growth process, the axial temperature gradient increases and then decreases from the bottom to the top of the crucible, with almost flat isotherms near the solid–liquid interface where the axial temperature gradient is larger. At the shoulder below the crucible, the solid–liquid interface was improved by adjusting the tilt angle. Furthermore, based on a novel design of the heat-insulating baffle, the concave solid–liquid interface in the iso-diameter stage can be effectively adjusted to realize a lower radial temperature gradient. This study provides theoretical guidance for the optimization of the growth of high-quality PbF2 crystals by the Bridgman method.

ПРЕОБРАЗОВАНИЕ ТЕПЛОВОЙ ЭНЕРГИИ В ЭЛЕКТРИЧЕСТВО: ПОТЕНЦИАЛ И ЭФФЕКТИВНОСТЬ ТЕРМОЭЛЕКТРИЧЕСКИХ ГЕНЕРАТОРОВ НА ОСНОВЕ ЭЛЕМЕНТОВ ПЕЛЬТЬЕ

Relevance Energy extraction using thermoelectric generators powered by Peltier elements through the application of both natural and engineered heat sources, aiming to create a new green method for clean energy production. Aim of research This study delves into the literature analysis to identify the factors that influence the accuracy of energy conversion, and aims to investigate the performance of Peltier elements while learning the principles of heat transfer, creating optimal conditions for the operation of a thermoelectric generator based on them. During the experiments, by adapting the process conditions, a process transfer function is formed, which aims to improve the energy generation efficiency. The aim of the study is to analyze the efficiency of thermoelectric generators based on Peltier cells. Research methods Physical foundations of thermoelectricity, development of a mathematical model. Results The study analyzed that the simulation revealed the presence of temperature gradients in regions with thermal waters of the mountain mass, and a mathematical model of the process was developed.

Integration of ramped temperature oxidation and combustion tube tests for kinetic modeling of heavy oil in-Situ combustion

In-situ combustion (ISC) has been applied as a follow-up process after steam injection-based technologies to improve heavy oil recovery and lower operating costs. Comprehensive understanding of the oxidation behavior and reliable prediction of the ISC performance are of great importance in the design of a ISC process. In this work, a calibration workflow was proposed to investigate the oxidation behavior and then establish a reaction kinetics model. A Ramped Temperature Oxidation (RTO) experiment was firstly conducted to capture the detailed oxidation behavior at elevated temperature conditions. Subsequently, a Combustion Tube (CT) test was performed to further evaluate the overall performance of ISC. Based on the integration of RTO and CT results, a comprehensive reaction kinetics model was developed to predict the ISC performance within a wide temperature range, including Low Temperature Oxidation (LTO), Negative Temperature Gradient Region (NTGR), and High Temperature Oxidation (HTO) reactions. It is found that the NGTR of heavy oil with high saturate and low asphaltene exhibits a narrow temperature range. The combustion front velocity in the RTO is comparable with that in the CT. In a stable HTO region, the CO2 concentrations in the RTO experiment and CT test were kept around 17% and 14%, respectively. The existence of LTO reactions in the RTO experiment caused the deviation of CO2 concentration. With the incorporation of the reaction model into simulation, a good agreement between measured and predicted results was obtained. This demonstrates that the established reaction model is capable of capturing the key oxidation mechanisms. In addition, the proposed workflow also helps upscale the oxidation behavior from a RTO experiment to a CT test and provide benchmarks for field operations.

Фактологическое обоснование структуры данных ГИС «Паспорт климатической безопасности республики Адыгея»

The study is aimed at determining the optimal data structure of the regional monitoring and forecasting system of climate change and related weather and climate risks for the socio-economic infrastructure of the Republic of Adygea. The basic spatial units of monitoring identified landscape and climatic regions, allocated according to a combination of factors correcting the zonal mode of meteorological processes in the North-West Caucasus under the conditions of the mountain-plain Adygea. With regard to landscape and climatic areas, differences have been identified in both the variation of climatic parameters in the multi-year and annual course, and in the recurrence and severity of hazardous and adverse hydrometeorological processes. Preliminary studies of climate change in Adygea and the results of reanalysis have revealed a steady trend of warming of the climate, especially intensive in the last 20 years (1.2°C/10 years), caused by the increase of temperature in the cold half of the year, at a low temperature change of the warm period. The dramatic increase in air temperature over the past two decades highlights the challenge of current climate change and its impacts. The results proving coherence of the course of parameters of the energetic field of the ground atmosphere (gradient field of temperature) with the course of parameters of intensity of the hydrometeorological phenomenon at the forecasting point have been obtained. It is proposed to use the regional temperature gradient value reflecting the dynamics of the thermal field of the region as a predictor in models of forecasting hydrometeorological phenomena and processes of different advance. Successful long-term forecasting of weather-climatic phenomena will provide the fulfillment of those functions, which are intended “Climate Safety Passport”.

Continental Geometry’s Role in Shaping Wintertime Temperature Variance

Abstract The factors controlling the present-day pattern of temperature variance are poorly understood. In particular, it is unclear why the variance of wintertime near-surface temperatures on daily and synoptic time scales is roughly twice as high over North America as over Eurasia. In this study, continental geometry’s role in shaping regional wintertime temperature variance is investigated using idealized climate model simulations run with midlatitude continents of different shapes. An isolated, rectangular midlatitude continent suggests that in the absence of other geographic features, the highest temperature variance will be located in the northwest of the continent, roughly collocated with the region of largest meridional temperature gradients, and just north of the maximum near-surface wind speeds. Simulations with other geometries, mimicking key features of North America and Eurasia, investigate the impacts of continental length and width, sloping coastlines, and inland bodies of water on regional temperature variance. The largest effect comes from tapering the northwest corner of the continent, similar to Eurasia, which substantially reduces the maximum temperature variance. Narrower continents have smaller temperature variance in isolation, implying that the high variances over North America must be due to the nonlocal influence of stationary waves. Support for this hypothesis is provided by simulations with two midlatitude continents, which show how continental geometry and stationary waves can combine to shape regional temperature variance. Significance Statement Wintertime temperature variance over North America is roughly twice as high as over Eurasia, but the reasons for this are unknown. Here we use idealized climate model simulations to investigate how continental geometry shapes regional temperature variance. We find that the smaller variance over Eurasia is largely due to the tapering of its northwest coast, which weakens temperature gradients in the continental interior. Our simulations also suggest that in isolation a narrow continent, like North America, should have weak temperature variance, implying that stationary waves are responsible for the high variance over North America. Understanding the controls on regional temperature variance is important for interpreting present-day winter climates and how these will change in the future.

On the impact of dropsondes on the ECMWF Integrated Forecasting System model (CY47R1) analysis of convection during the OTREC (Organization of Tropical East Pacific Convection) field campaign

Abstract. The Organization of Tropical East Pacific Convection (OTREC) field campaign, conducted August through October 2019, focuses on studying convection in the eastern Pacific and the Caribbean. An unprecedented number of dropsondes were deployed (648) during 22 missions to study the region of strong sea surface temperature (SST) gradients in the eastern Pacific region, the region just off the coast of Columbia, and in the uniform SST region in the southwestern Caribbean. The dropsondes were assimilated in the European Centre for Medium-Range Weather Forecasts (ECMWF) model. This study quantifies departures, observed minus the model value of a variable, in dropsonde denial experiments and studies time series of convective variables, saturation fraction which measures moisture and instability index and deep convective inhibition which quantify atmospheric stability and boundary layer stability to convection, respectively. Departures are small whether dropsondes are assimilated or not, except in a special case of developing convection and organization prior to Tropical Storm Ivo where wind departures are significantly larger when dropsondes are not assimilated. Departures are larger in cloudy regions compared to cloud-free regions when comparing a vertically integrated departure with a cloudiness estimation. Abovementioned variables are all well represented by the model when compared to observations, with some systematic deviations in and above the boundary layer. Time series of these variables show artificial convective activity in the model, in the eastern Pacific region off the coast of Costa Rica, which we hypothesize occurs due to the overestimation of moisture content in that region.

Growth-climate sensitivity of two pine species shows species-specific changes along temperature and moisture gradients in southwest China

A better understanding of tree growth-climate sensitivity across regions and species may reduce uncertainties in simulating forest carbon budgets. We studied the spatial heterogeneity of growth-climate sensitivity of Pinus yunnanensis and Pinus kesiya across temperature and moisture gradients in the complex mountain regions of Southwest China. We developed tree ring-width chronologies from 22 sites for P. yunnanensis and 20 sites for P. kesiya, totaling 903 trees (1684 cores). We applied generalized additive mixed models (GAMMs) on basal area increment (BAI) series to remove the age and size effects on tree growth, and correlated BAI residual chronologies with climate variables. Radial growth of P. yunnanensis and P. kesiya at most sites (> 75%) were positively correlated with precipitation and one-month Standardized Precipitation-Evapotranspiration Index (SPEI1) during the early growing season. In contrast, high precipitation and SPEI1 during the late growing season reduced tree growth of both pine species. The growth-climate sensitivity of both pine species varied along the temperature and moisture gradients, i.e., moisture sensitivity of tree growth decreased along a dry-to-humid moisture gradients for P. kesiya during early growing season, whereas temperature sensitivity of P. yunnanensis shifted from positive (beneficial) to negative (limitative) along cold-to-warm gradients. Our results indicate that the growth-climate sensitivity of both pine species varies with site-specific environmental conditions. These findings contribute to improve our understanding about the spatial patterns of tree growth-climate responses of these economically important conifer species in Southwest China.

Effects of Hotspot‐Induced Long‐Wavelength Mantle Melting Variations on Magmatic Segmentation at the Reykjanes Ridge: Insights From 3D Geodynamic Modeling

AbstractSpatial variations in mantle melting induced by the Iceland hotspot have strong effects on meso‐scale mantle upwelling and crustal production along the slow‐spreading Reykjanes Ridge. The ridge‐hotspot interaction has been recorded by diachronous V‐shaped ridges and troughs extending away from Iceland, as well as by changes in ridge segmentation since 37 Ma. The origins of V‐shaped structures are widely debated, while the causes of the gradual erasion of ridge segments bounded by transform faults are rarely investigated. Through 3D time‐dependent geodynamic modeling, this study investigates how the hotspot‐induced regional mantle melting variations affect ridge segmentation. Periodic temperature perturbations were initially imposed beneath the melting zone to trigger buoyant upwelling cells, which corresponded to the offset ridge segments at the Reykjanes Ridge. Iceland hotspot‐induced long‐wavelength mantle melting variations were generated by applying a regional linear temperature gradient at the bottom of the model domain. Modeling reveals a two‐stage evolution of the buoyant upwelling cells that characterizes the segmentation transition at the Reykjanes Ridge. In Stage 1, the regional mantle melting variations trigger along‐axis pressure‐driven mantle flow, which alters the segment‐scale mantle upwelling and promotes the propagation of segment boundaries away from the region with relatively higher mantle temperature. In Stage 2, buoyant upwelling cells are destroyed progressively as along‐axis mantle flow dominants, leaving V‐shaped diachronous boundaries between the segmented and unsegmented crust. These results advance our understanding of the effects of long‐wavelength mantle melting variations induced by regional mantle heterogeneities on ridge segment evolution at slow‐spreading ridges.

Direct observation of the non-locality of non-diffusive counter-gradient electron thermal transport during the formation of hollow electron-temperature profiles in the Large Helical Device

A heating source with off-axis electron cyclotron heating (ECH) alone produced a plasma with a quasi-steady-state hollow electron-temperature profile in the Large Helical Device. The clear formation of this quasi-steady-state hollow electron-temperature profile can be explained by adding the outward heat convection term to the diffusion term, as a simple model to describe the electron heat flux, using the energy conservation equation. In addition, we directly observed the non-locality of the non-diffusive (convective) contribution in transient electron thermal transport in the condition that power-modulated on-axis ECH was applied to the plasma sustained by off-axis ECH. The experimentally evaluated flux-gradient relation shows two different positive values of the electron heat flux at zero temperature gradient by going back and forth between positive and negative temperature gradient regions in the transport hysteresis phenomenon.

Информативность геоинформационной вычислительной визуализации процессов формирования природных объектов

The paper discusses informative possibilities and prospects of application of digital nature-like methodology for computational visualization of natural processes of natural system formation based on the proposed order parameter—intensity of integral geophysical field created by host structure-forming outer space. Since the designated order parameter defines the structure and properties of natural systems and processes, the gradient of the parameter defining the structure of the natural object is a measure of its order parameter and, therefore, can serve as a predictor of forecasting the change in its properties and structure. The declared approach is tested using an example of forecasting the process of flood formation and processes of visualization of tectonic stress fields. The authors have developed a method of point prediction of the onset time and flood level based on a three-level neural network model and a method of vector space-time visualization of a hierarchy of tectonic stress fields on the territory of an unlimited area. The research shows that computational operations with the parameter of the regional temperature gradient along with intelligent forecasting methods illustrate the prospects of point medium-, long-term forecasting of hydrometeorological processes provided with long rows of instrumental observation data. Computational visualization of general, background and local fields of tectonic stresses in the territories of unlimited area serves as a source of parametric data for geoinformation-mathematical modeling of tectonic stress field restructuring in processes of tectonosphere self-organization, calculation of position of geodynamic instability loci—epicenters of possible earthquakes, visualization of tectonic currents in the Earth’s crust. Monitoring geophysical data at geodynamic instability loci opens up prospects for point prediction of earthquakes. Calculation of order parameters of natural objects and processes opens up prospects of their computational modeling, derivation of numerical laws of their conjugate development and a scale series of interaction, as well as prediction of the state of geo objects and geo processes at a given geo space point in conditions of increasing global natural variability.

Thermoelectric behavior of Al/PTFE reactive materials induced by temperature gradient

In order to reveal the physical effect of Al/PTFE (mass percentage of 50%/50%) heat conduction and deflagration reaction induced by temperature gradient under the condition of flame heating, the loading and testing systems of cookoff experiment were conducted to measure the thermal response and electrical output characteristics of Al/PTFE before and after deflagration induced by temperature gradient. The thermal shock wave and thermoelectromotive force before deflagration, voltage signal induced by flame plasma expansion after deflagration were measured simultaneously. Meanwhile, the flash signal and the evolutionary process of flame region and temperature after deflagration were obtained. The results show that the thermal shock wave was generated by emergent temperature change in the stage of heat conduction, and the thermoelectromotive force was generated by the superposition of temperature gradients in different regions. The thermoelectromotive force can be equivalent to the series connection of electric source in each striped region. Under the temperature gradient of 6-10 K/mm, the maximum thermoelectromotive force can reach 0.8 V. Before deflagration, the local phase transition of molten or gaseous state induced by thermal decomposition destroyed the stable distribution of the temperature gradient of the sample, which leads to the decrease of the thermoelectric force. Based on the electric output signal of flame plasma, the reaction was divided into two stages including deflagration stage (lasting for 2–3 s) and stable combustion stage (lasting for about 10s). The average temperature of flame first increased and then decreased abruptly. The maximum temperature was 1585 K, and the propagation rate of flame was about 81.6 m/s in the initial stage of deflagration; however, the average temperature of the flame decreased slowly in the stable combustion stage, there was no obvious electrical output and the flash intensity decreased.

Reaction model of low asphaltene heavy oil from ramped temperature oxidation experimental analyses and numerical simulations

In situ combustion (ISC) is an advanced thermal recovery technique for crude oil exploitation. The crude oil reaction models with accurate kinetic data are crucial to predict the ISC process. This study investigated the China Xinjiang crude oil reaction kinetics through Ramped Temperature Oxidation (RTO) experiments and numerical simulations. Three different ISC behaviors with low-temperature oxidation (LTO), Negative Temperature Gradient Region (NTGR) reactions and high-temperature oxidation (HTO) were observed from the RTO experiments. The effects of the air injection rate and heating rate on the temperature profile and effluent gas composition were carefully investigated. Experimental results showed that the higher air injection rate and lower heating rate enhanced the heat generation, mainly from the more intensive exothermic HTO reactions. A simplified crude oil reaction model involving LTO, NTGR, and HTO was proposed and implemented with a numerical model to simulate the RTO behaviors. This study also suggested a workflow to build the reaction scheme and calibrate the kinetic data for good predictability and generalization. Acceptable consistency was achieved between the RTO experiments and numerical simulation, which demonstrates the proposed reaction model was predictive to capture the key oxidation mechanism and reproduce the ISC behaviors of the Xinjiang crude oil.

Characteristics of cyclones following different pathways in the Gulf Stream region

AbstractThe Northwest Atlantic is a region of strong temperature gradients and hence is a favourable location for wintertime cyclone intensification co‐located with the storm track. The temperature gradient is associated with both the sea surface temperature front along the Gulf Stream and the land–sea contrast. To understand the respective influences of the sea surface temperature (SST) front and land–sea contrast in the Gulf Stream region, as well as the role of upper‐level forcing on cyclone development, we track individual cyclones and categorise them depending on their propagation relative to the SST front. We concentrate on cyclones staying either on the cold (C1) or warm (C2) side of the SST front, and on cyclones that cross the SST front from the warm to the cold side (C3). Comparing these categories, we find that the land–sea contrast is more important for supplying baroclinicity to cyclones in C1, while the strong low‐level baroclinicity in C3 is also partially attributable to the SST front. The propagation of cyclones in C1 and C3 near the left exit region of the North Atlantic jet explains the higher intensification and precipitation.

Latitudinal gradient of termite diversity indicates higher diversification and narrower thermal niches in the tropics

AbstractAimTo investigate the contributions of ecosystem productivity, temperature‐dependent metabolism and climatic tolerances to the latitudinal gradient in species richness and changes in species composition in tropical and subtropical regions.LocationGlobal.Time periodContemporary.Major taxa studiedTermites.MethodsWe compiled termite occurrence data from papers using the standardized sampling protocol proposed 20 years ago by Jones and Eggleton. Three continents, 28 countries and 494 sampling plots were included in our database. We used structural equation models to determine the direct and indirect effects of productivity, and the average and extreme values of temperature and precipitation on termite species richness. We also compared the observed association between diversity and temperature with predictions from the metabolic theory of ecology and compared how the similarity in species composition relates to geographic distance and environmental differences in tropical versus subtropical regions.ResultsTermite species richness was, directly and indirectly, related to average and extreme temperatures, but not to productivity. However, the association of species richness and temperature was much stronger than predicted by the metabolic theory of ecology. Moreover, species composition changed more rapidly with geographic distance and temperature differences between plots in the tropics than in the subtropics.Main conclusionsThese results suggest that the increase of species richness toward the equator cannot be explained by productivity gradients. Instead, the increase in the speciation rates and the narrow species niches along the temperature gradient in tropical regions likely determine the distribution of termites at broad spatial scales.

The influence of thermal distribution on macro profile and dendrites morphology based on temperature field simulation of 6061 aluminum alloy laser welded joint

Temperature distribution has an important influence on grain morphology during laser welding process. In this investigation, a three-dimensional finite element model considering the effect of different laser welding parameters on heat distribution was established. Moreover, the macro profile and grain morphology in different regions of 6061 aluminum alloy laser welded joints were studied considering different welding heat input. It was found that the upper and bottom weld widths increase with the welding heat input. As the welding speed and laser power increase, the high temperature regions during welding process are elongated in the welding direction. Besides, the size of coarse equiaxed dendrites in the center of weld seam increase with welding heat input and cooling rate. The thermal field simulation results shows that the different temperature distribution and temperature gradient in different regions of weld seam have great effect on grain morphology. Besides, the temperature gradient is smallest in the center of molten pool, while biggest at the edge of molten pool.

Global picophytoplankton niche partitioning predicts overall positive response to ocean warming

Ocean phytoplankton biomass is predicted to decline in Earth system models, due in large part to an expansion of nutrient-deplete ocean regions. However, the representation of ecosystems in these models is simplified and based on only a few functional types. As a result, they fail to capture the high diversity known to exist within and across phytoplankton communities. Here we present an assessment of the global biogeography of the very abundant but little studied picoeukaryotic phytoplankton by analysing a global abundance dataset with a neural-network-derived quantitative niche model. Combining this niche model with previous assessments of the distribution of Prochlorococcus and Synechococcus, we find that different cell sizes among picophytoplankton lineages are clearly partitioned into latitudinal niches. In addition, picophytoplankton biomass increases along a temperature gradient in low-latitude regions. We infer that future warmer ocean conditions can lead to elevated phytoplankton biomass in regions that are already dominated by picophytoplankton. Finally, we demonstrate that elevated upper-ocean nutrient recycling and lower nutrient requirements of phytoplankton have the potential to support increasing low-latitude phytoplankton biomass with future warming. Picophytoplankton are partitioned into niches, globally, and their abundance may increase as ocean temperatures rise, suggest analyses of a global abundance dataset with a neural-network-based niche model.