Decrease In Environmental Temperature Research Articles

Effects of Environmental Temperature and Trapped Air Bubbles on the Mechanical Properties of Ice Cubes.

Ice is a widespread material in natural and industrial fields. Trapped air bubbles form in ice cubes due to the differences in the solubility of air in ice and water, which directly affects the mechanical strength of the ice cubes. To investigate the effects of environmental temperature and trapped air bubbles on the mechanical properties of ice cubes, a series of experiments are designed and carried out. A mathematical model that predicts the mechanical strength of ice cubes with an accuracy over 80% is developed and validated. The results show that even a volume content of trapped air bubbles in an ice cube as low as 1.98% can greatly impact the mechanical properties. This model reveals the mechanisms and principles governing the influences of environmental temperature and bubble volume content on the mechanical strength of ice cubes. As the environmental temperature decreases from 0 to -20 °C, the compressive strength of clear ice cubes increases from 1.71 to 2.10 MPa, while that of bubble ice cubes increases from 1.58 to 1.95 MPa. This study has implications for utilizing trapped air bubbles to regulate the mechanical properties of ice and for optimizing various mechanical deicing techniques.

Integrated cellular response of the zebrafish (Danio rerio) heart to temperature change.

A decrease in environmental temperature represents a challenge to the cardiovascular system of ectotherms. To gain insight into the cellular changes that occur during cold exposure and cold acclimation we characterized the cardiac phosphoproteome and proteome of zebrafish following 24 h or one week exposure to 20 oC from 27 oC; or at multiple points during six weeks of acclimation to 20 oC from 27 oC. Our results indicate that cold exposure causes an increase in mitogen-activated protein kinase signaling, the activation of stretch sensitive pathways, cellular remodeling via ubiquitin-dependent pathways, and changes to the phosphorylation state of proteins that regulate myofilament structure and function including desmin and troponin T. Cold acclimation (2-6 weeks) led to a decrease in multiple components of the electron transport chain through time, but an increase in proteins for lipid transport, lipid metabolism, the incorporation of polyunsaturated fatty acids into membranes and protein turnover. For example, there was an increase in the levels of apolipoprotein C, prostaglandin reductase-3, and surfeit locus protein 4, involved in lipid transport, lipid metabolism, and lipid membrane remodeling. Gill opercular movements suggests that oxygen utilization during cold acclimation is reduced. Neither the amount of food consumed relative to body mass nor body condition were affected by acclimation. These results suggest that while oxygen uptake was reduced, energy homeostasis was maintained. This study highlights that the response of zebrafish to a decrease in temperature is dynamic through time and that investment in the proteomic response increases with the duration of exposure.

Phase-Change/Salt-Based Slow-Release Composite Material for Anti-Icing and Snow-Melting

Currently, self-desiccating asphalt mixtures on roads mainly incorporate phase-change materials or salt-based slow-release agents individually for de-icing. However, pure phase-change material mixtures have limited anti-freezing efficiency and short heat-release duration, making them impractical for large-scale snow melting; meanwhile, salt-based slow-release agents suffer from rapid deterioration in de-icing performance. To address these issues encountered, herein, we introduce the phase-change/salt-based slow-release composite materials via the integration of these two materials and investigate their pavement and de-icing performance with the asphalt mixture. For the pavement performance, the optimal asphalt–aggregate ratio for the anti-icing asphalt mixture was found to be 5.1% For anti-bonding and de-icing performance, the electrical conductivity tests, bonding pull-off tests, and interfacial contact melting experiments were conducted. The results indicate that the latent heat of the TH-ME5 (phase-change material) can delay the decrease in environmental temperature and inhibit salt release from T-SEN (salt-based slow-release material), thereby extending the lifespan of the anti-icing asphalt mixture. These results demonstrate that the synergistic effect between the two components of the composite material not only enhance the snow-melting and de-icing performance of the asphalt pavement but also prolong the snow-melting time of the pavement in a low-temperature environment.

An Ecological Weed Control Strategy in Paddy Fields: Light Interception from Duckweed Mulching

Rice–duckweed coculturing as an advanced technique has proven effective for weed control. However, the complex environmental interactions underlying its effectiveness remain unclear. In this study, a controlled pot experiment was conducted to isolate the shading effect of duckweeds (Landoltia punctata and Spirodela polyrhiza) from their intricate environmental interactions with paddy weeds (Cyperus difformis, Eclipta prostrata, and Ammannia auriculata). The results revealed that as the duckweeds grew, there were notable decreases in total weed density (52.41–77.01%) and biomass (42.33–99.23%) while rice biomass remained unaffected. Duckweed covering allowed less than 8.64% of light to pass through and led to decreases in environmental temperature, pH, and dissolved oxygen concentration in the floodwater, but had little impact on inorganic nitrogen levels. Through screening with random forest analysis and structural equation modelling, it was found that weed density and biomass were predominantly influenced by the reduced light transmittance (54.1% and 77.2%, p ≤ 0.001) resulting from duckweed covering while the decline in dissolved oxygen content partly influenced weed density (18%). In conclusion, this study’s results bring a different perspective, confirming the sunlight-shading effect of duckweed as a critical mechanism significantly inhibiting the germination and growth of weeds. These findings provide a scientific basis for the improved application of ecological weed control methods in paddy fields.

Susceptibility of hypertensive individuals to acute blood pressure increases in response to personal-level environmental temperature decrease

BackgroundEnvironmental temperature is negatively associated with blood pressure (BP), and hypertension may exacerbate this association. The aim of this study is to investigate whether hypertensive individuals are more susceptible to acute BP increases following temperature decrease than non-hypertensive individuals. MethodsThe study panel consisted of 126 hypertensive and 125 non-hypertensive (n = 251) elderly participants who completed 940 clinical visits during the winter of 2016 and summer of 2017 in Beijing, China. Personal-level environmental temperature (PET) was continuously monitored for each participant with a portable sensor platform. We associated systolic BP (SBP) and diastolic BP (DBP) with the average PET over 24 h before clinical visits using linear mixed-effects models and explored hourly lag patterns for the associations using distributed lag models. ResultsWe found that per 1 °C decrease in PET, hypertensive individuals showed an average (95 % confidence interval) increase of 0.96 (0.72, 1.19) and 0.28 (0.13, 0.42) mmHg for SBP and DBP, respectively; and non-hypertensive participants showed significantly smaller increases of 0.28 (0.03, 0.53) mmHg SBP and 0.14 (-0.01, 0.30) mmHg DBP. A lag pattern analysis showed that for hypertensive individuals, the increases in SBP and DBP were greatest following lag 1 h PET decrease and gradually attenuated up to lag 10 h exposure. No significant BP change was observed in non-hypertensive individuals associated with lag 1–24 h PET exposure. The enhanced increase in PET-associated BP in hypertensive participants (i.e., susceptibility) was more significant in winter than in summer. ConclusionsWe found that a decrease in environmental temperature was associated with acute BP increases and these associations diminished over time, disappearing after approximately 10 hours. This implies that any intervention measures to prevent BP increases due to temperature drop should be implemented as soon as possible. Such timely interventions are particularly needed for hypertensive individuals especially during the cold season due to their increased susceptibility.

THE MECHANICAL PROPERTIES AND FAILURE MODE OF SIMULATED LUNAR ROCK BY IN SITU TEMPERATURE REAL-TIME ACTION OF LUNAR-BASED

To achieve in situ condition-preserved coring of the lunar surface and deep lunar rocks and a return mission, it is necessary to explore the mechanical properties and failure modes of simulated lunar rocks that have physical and mechanical properties approximately equivalent to those of mare basalt under simulated lunar temperature environments ([Formula: see text][Formula: see text]C to 200[Formula: see text]C). To this end, real-time uniaxial compression tests were conducted on simulated lunar rocks under corresponding in situ temperature conditions, and the mechanical properties, deformation characteristics, micromorphology, and failure modes were analyzed. Based on the macroscopic analysis, as the environmental temperature decreases, the uniaxial compressive strength, peak strain, and peak strain duration of simulated lunar rocks exhibit a nonlinear increasing trend, with maximum increases of 33.00[Formula: see text], 36.16[Formula: see text], and 49.25[Formula: see text] from those at room temperature, respectively. Based on microscopic analysis, the intergranular fractures run through the entire samples under the environmental temperature. As the environmental temperature increases, intergranular and transgranular fractures coexist, and layered fractures appear at high temperatures. At the same time, some samples exhibit undulating and stepped morphologies caused by shear stress. For the fractal dimension of a simulated lunar rock main fracture surface, the fractal dimension of the actual angle and the corrected angle increase first and then decrease with increasing environmental temperature, and the maximum error of the two is only 1.84[Formula: see text]. The overall fractal dimension ranges from 2.02 to 2.28, and the fractal dimension under real-time high-temperature conditions is higher than that under real-time low-temperature conditions. In addition, the failure mode of the simulated lunar rocks under real-time in situ temperature changes is a combined tensile–shear failure mode with shear failure (primary) and tensile failure (secondary). The above research results are expected to be applied to in situ condition-preserved coring in extreme lunar environments and provide a scientific basis for the design and development of in situ condition-preserved coring robot systems for the extreme environment of deep space.

Standard metabolic rate variation among New Zealand Orthoptera

Standard metabolic rates (SMR) of ectotherms reflect the energetic cost of self-maintenance and thus provide important information about life-history strategies of organisms. We examined variation in SMR among fifteen species of New Zealand orthopteran. These species represent a heterogeneous group with a wide geographic distribution, differing morphologies and life histories. Gathering original data on morphological and physiological traits of individual species is a first step towards understanding existing variability. Individual metabolic rates of ectotherms are one of the first traits to respond to climate change. Baseline SMR datasets are valuable for modeling current species distributions and their responses to a changing climate. At higher latitudes, the average environmental temperature decreases. The pattern that cold-adapted ectotherms display higher SMR at colder temperatures and greater thermal sensitivity to compensate for lower temperatures and the shorter growing and reproductive seasons is predicted from the metabolic cold adaptation (MCA) hypothesis. We predict higher SMR for the orthopteran species found at higher latitudes. We further compared the index of thermal sensitivity Q10 per species. We used closed-system respirometry to measure SMR, at two test temperatures (4 °C and 14 °C), for the fifteen species acclimated to the same conditions. As expected, we found significant differences in SMR among species. The rate of oxygen consumption was positively correlated with body mass. Our findings do not support the MCA hypothesis. In fact, we found evidence of co-gradient variation in SMR, whereby insects from higher elevations and latitudes presented lower SMR. We discuss our findings in relation to life histories and ecology of each species. The novel physiological data presented will aid in understanding potential responses of these unusual species to changing climatic conditions in Aotearoa/New Zealand.

Incidence of perioperative hypothermia in a high-quality high-volume spay/neuter setting and association with environmental temperature

Introduction: Perioperative inadvertent hypothermia (PIH) can prolong anesthetic recovery times. Study goals included determining PIH incidence (rectal temperature<36°C (96.8°F)) in the high-quality high-volume spay/neuter (HQHVSN) setting and evaluating associations between environmental temperature and PIH incidence. Secondary objectives included evaluating associations between PIH incidence, anesthesia recovery times, and postoperative pain. Methods: Prospective observational cohort study conducted at five HQHVSN shelters enrolling dogs undergoing ovariohysterectomy or castration and cats undergoing ovariohysterectomy. Blankets and electric heating pads were only used routinely in the immediate postoperative period. Regression models were used to evaluate associations between PIH incidence, environmental temperature, and pain data. Results: One hundred and forty dogs undergoing 65 castrations and 75 ovariohysterectomies, and 161 cats were enrolled. Mean surgical times were 19.6 (8.0) min (canine ovariohysterectomies), 7.2 (3.0) min (canine castrations), and 10.6 (3.6) min (feline ovariohysterectomies). PIH incidence was 22% (95% CI = 17–27). The risk of developing PIH was associated with environmental temperature, with a 22% increase in the odds of experiencing PIH for each degree centigrade decrease in environmental temperature (OR = 1.22, 95% CI = 1.03–1.44, P = 0.02) over a recorded range of 15.6–26.1°C (60.1–79.0°F). In cats, PIH was associated with a prolongation of time to extubation by 3.8 min (95% CI 2.27–5.37, P = 0.01). On average, each degree centigrade reduction in rectal temperature at extubation was associated with an increase in pain scale of 0.51 units (95% CI = 0.06–0.97, P = 0.03) for both species. In dogs, each degree centigrade reduction in rectal temperature at extubation was associated with a reduction in mechanical threshold (indicating increased sensitivity to pain) of 1.40 N (95% CI = 0.44–2.35, P = 0.004). Conclusion: PIH is common in a spay/neuter population despite rapid surgical times and is associated with prolonged anesthetic recovery in cats and increased postoperative pain in cats and dogs. Raising the environmental temperature in operative and recovery areas may reduce incidence.

Histone H3 and H4 Modifications Point to Transcriptional Suppression as a Component of Winter Freeze Tolerance in the Gall Fly Eurosta solidaginis.

The goldenrod gall fly (Eurosta solidaginis) is a well-studied model of insect freeze tolerance. In situations of prolonged winter subzero temperatures, larvae of E. solidaginis accept ice penetration throughout extracellular spaces while protecting the intracellular environment by producing extreme amounts of glycerol and sorbitol as cryoprotectants. Hypometabolism (diapause) is implemented, and energy use is reprioritized to essential pathways. Gene transcription is one energy-expensive process likely suppressed over the winter, in part, due to epigenetic controls. The present study profiled the prevalence of 24 histone H3/H4 modifications of E. solidaginis larvae after 3-week acclimations to decreasing environmental temperatures (5 °C, -5 °C and -15 °C). Using immunoblotting, the data show freeze-mediated reductions (p < 0.05) in seven permissive histone modifications (H3K27me1, H4K20me1, H3K9ac, H3K14ac, H3K27ac, H4K8ac, H3R26me2a). Along with the maintenance of various repressive marks, the data are indicative of a suppressed transcriptional state at subzero temperatures. Elevated nuclear levels of histone H4, but not histone H3, were also observed in response to both cold and freeze acclimation. Together, the present study provides evidence for epigenetic-mediated transcriptional suppression in support of the winter diapause state and freeze tolerance of E. solidaginis.

Competition of Carrier Kinetics Contributes to Amplified Spontaneous Emission in Quasi-2D/3D (PBA)2MAn–1PbnBr3n+1 Thin Films under Strip Light Mode

Quasi-2D halide perovskites have potential in lasing due to their amplified spontaneous emission (ASE) properties. The ASE of (PBA)2MAn-1PbnBr3n+1 thin films has been confirmed by photoluminescence (PL) testing using stripe light excitation (SLE). The ASE threshold decreases with decreasing environmental temperature (TE) or increasing number of inorganic layers (n). Using the transient absorption technique, the Auger recombination and the cooling process of the high-activity carrier are accelerated with the decrease of n or TE. A new ASE mechanism is proposed where high-activity carriers directly emit photons under photon perturbation from adjacent sites, leading to the accumulation and amplification of emitted photons only in the SLE region for ASE to occur. In addition, the reduction of n promotes light scattering between nano-thin layers, which supports a rapid increase in the ASE signal after the ASE threshold is crossed.

A cold-responsive liquid crystal elastomer provides visual signals for monitoring a critical temperature decrease.

Critical temperature indicators have been extensively utilized in various fields, ranging from healthcare to food safety. However, the majority of the temperature indicators are designed for upper critical temperature monitoring, indicating when the temperature rises and exceeds a predefined limit, whereas stringently demanded low critical temperature indicators are scarcely developed. Herein, we develop a new material and system that monitor temperature decrease, e.g., from ambient temperature to the freezing point, or even to an ultra-low temperature of -20 °C. For this purpose, we create a dynamic membrane which can open and close during temperature cycles from high temperature to low temperature. This membrane consists of a gold-liquid crystal elastomer (Au-LCE) bilayer structure. Unlike the commonly used thermo-responsive LCEs which actuate upon temperature rise, our LCE is cold-responsive. This means that geometric deformations occur when the environmental temperature decreases. Specifically, upon temperature decrease the LCE creates stresses at the gold interface by uniaxial deformation due to expansion along the molecular director and shrinkage perpendicular to it. At a critical stress, optimized to occur at the desired temperature, the brittle Au top layer fractures, which allows contact between the LCE and material on top of the gold layer. Material transport via cracks enables the onset of the visible signal for instance caused by a pH indicator substance. We apply the dynamic Au-LCE membrane for cold-chain applications, indicating the loss of the effectiveness of perishable goods. We anticipate that our newly developed low critical temperature/time indicator will be shortly implemented in supply chains to minimize food and medical product waste.

Larger insects in a colder environment? Elevational and seasonal intraspecific differences in tropical moth sizes on Mount Cameroon

Abstract Bergmann’s Rule describes an increase in the body size of endothermic animals with decreasing environmental temperatures. However, in ectothermic insects including moths, some of the few existing studies investigating size patterns along temperature gradients do not follow the Bergmann’s Cline. Intraspecific differences in moth sizes along spatiotemporal temperature gradients are unknown from the Palaeotropics, hindering general conclusions and understanding of the mechanism responsible. We measured intraspecific forewing size differences in 28 Afrotropical moth species sampled in 3 seasons along an elevational gradient on Mount Cameroon, West/Central Africa. Size increased significantly with elevation in 14 species but decreased significantly in 5 species. Additionally, we found significant inter-seasonal size differences in 21 species. Most of these variable species had longer forewings in the transition from the wet to dry season, which had caterpillars developing during the coldest part of the year. We conclude that environmental temperature affects the size of many Afrotropical moths, predominantly following prevailingly following Bergmann’s Cline. Nevertheless, the sizes of one-third of the species demonstrated a significant interaction between elevation and season. The responsible mechanisms can thus be assumed to be more complex than a simple response to ambient temperature.

Study of rolling-sliding contact damage and tribo-chemical behaviour of wheel-rail materials at low temperatures

The influence of the decrease in environmental temperature on the wear and tribo-chemical behaviours of wheel-rail materials was studied. The results indicated that, at all tested temperatures, a tribo-film zone, oxidation zone and metallic zone were formed on the worn rail surfaces. The decrease in the temperature could decrease the content of O and Fe3+ ions both in the tribo-film zone and the oxidation zone. As the temperature was reduced below 0 °C, the tribo-film zone on the rail surface enlarged significantly, leading to a decline in the wear rate of the rail material. With the decrease in the temperature, the embedded wear debris spots on the wheel surface increased and the wear rate of wheel decreased gradually. As the temperature declined from 20 °C to −40 °C, the wear form of wheel-rail would transform from the severe wear to mild the wear.

Walking is regulated by environmental temperature

The mechanisms that regulate human walking are not fully understood, although there has been substantial research. In our study, we hypothesized that, although walking can be volitionally modified, it is also involuntary and controlled by evolutionary factors, such as the relationship between temperature and movement speed in poikilotherms. This study aimed to determine the effects of environmental temperature on speed, step length, and cadence during unrestrained walking over long periods. Customers of a private insurance company were asked to use a background smartphone GPS application that measured walking parameters. Participants were 1065 app users (298 men and 767 women) aged 14–86 years. Observed walking speed and cadence were higher in winter (average maximum temperature: 10.2 °C) than in summer (average maximum temperature: 29.8 °C) (p < 0.001). The walking parameters were closely related to environmental temperature, with cadence most strongly correlated with daily maximum temperature (r = − 0.812, p < 0.001) and indicating a curvilinear relationship. A decrease in environmental temperature was found to increase cadence when the temperature was below 30 °C. The findings suggest that walking may be regulated by environmental temperature and potentially by the autonomic nervous system’s response to environmental temperature.

The role of environmental temperature on movement patterns of giant anteaters.

Mammals can show conspicuous behavioral responses to thermal variation, including changes in movement patterns. We used an integrative approach to understand how environmental temperature can drive the movement behavior of a mammal with low capacity for physiological thermoregulation, the giant anteater (Myrmecophaga tridactyla). We tracked 52 giant anteaters in 7 areas throughout the Brazilian savannah. We estimated the distance moved, area used, use of forest areas, and mean environmental temperature for each monitoring day of each individual. We modeled these data with Mixed Structural Equations - considering the possible interactions between our variables and controlling for sex and body mass. Giant anteaters reduced displacement and increased forest use with decreasing environmental temperature, probably because of their low body heat production. It is possible that they reduce distance moved and area used by reducing the duration of activity. With decreasing temperature, forest habitats become warmer than open ones, besides buffer rain and chilly winds. Reducing displacement and using forests are important strategies to reduce body heat loss and the energetic costs of thermoregulation. However, decreasing movement can limit food access and, consequently, fitness. Therefore, we highlight the importance of forests as thermal shelters. With increasing frequency and intensity of extreme weather events, we showed the need to preserve forest patches to offer suitable conditions for tropical mammals' behavioral thermoregulation. In this context, policies favoring deforestation on Brazilian territory are especially worrisome. Finally, we emphasize the need of integrative approaches to understand the complex interactions between organisms and the environment.

Design exploration study of a smart passive window based on NiTi bent actuator

This paper presents a multi-functional (sensing -actuating) greenhouse ventilation window design heated/cooled naturally by convection, to overcome different industry challenges in terms of designing smart applications. This ventilation window design includes a smart C-shaped NiTi actuator and three-pulley system, and all attached to the window. The force generated in the NiTi wire shrinks the C-shaped to open the ventilation window when the environmental temperature increases. When the environmental temperature decreases, the C-Shaped NiTi actuator returns to its initial position and closes the window. This smart actuation allows energy saving due to natural phase transformation induction (i.e. convection) and high force generation compared to the small NiTi wire mass. Using the pulley system is important as well to reduce the load on the NiTi actuator and enhance its long-life time. In this paper, the smart ventilation window actuator design has been disused followed by a simulation study to investigate the NiTi C-shaped element behavior. The simulation results predict the thermomechanical behavior of the NiTi wire at the proposed greenhouse environmental conditions and the force generated in the wire. For future studies, an experimental investigation could be done to prove the simulation results.

Corylus avellana bark optical properties differ during and out of the vegetation season

We compared different bark traits of the common hazel (Corylus avellana L.) in four different months during the vegetation season (September, November) and out of the vegetation season (January, February) to get an insight into the changes in bark morphological, biochemical, and optical properties. Since bark of woody plants contains a layer of chlorenchyma, which can harvest transmitted light and perform photosynthesis, we also measured bark potential photochemical efficiency of photosystem II. The values of the latter parameter decreased during the research period, ranging from 0.77 in September to 0.22 in February. This could be attributed to low temperatures. The shapes of the bark reflectance curves were similar between the four samplings, with a peak in red and pronounced reflectance in the near-infrared spectrum. However, the level of reflectance differed between the four samplings. Regarding the time of the season, we obtained the most pronounced changes in the green, yellow, and red reflectance spectra. Light reflectance in these regions was positively related with chlorophyll b and carotenoid contents, while it was negatively related with anthocyanins and UV-B–absorbing substances. Transmittance spectra showed less variability between the four samplings. Regarding the studied pigments, the most pronounced changes were obtained for anthocyanin and UV-B–absorbing substances contents, which decreased in accordance with decreasing environmental temperatures. On the contrary, the level of photosynthetic pigments remained high, thus enabling undisturbed primary metabolism.

Effect of cryogenic oils-on-water compared with cryogenic minimum quantity lubrication in finishing turning of 17-4PH stainless steel

17-4PH stainless steel is widely used for applications of critical importance owing to its favorable property profile. However, the great mechanical performance of 17-4PH stainless steel is at the cost of its unsatisfied machinability. Exploring suitable cooling method becomes an effective way to improve its machinability. This study aims to explore the applicability and feasibility of oils-on-water (OoW), which is a hybrid cooling/lubrication technique, compared with minimum quantity lubrication (MQL) in the finishing turning of 17-4PH stainless steel mixed with different cooling media, namely, cryogenic air (CA, −50 °C) and liquid nitrogen (LN, −178 °C). A comprehensive investigation of the cutting temperature, cutting forces, tool wear characterization and surface quality were studied. The result showed that CA or LN mixed with OoW (CAOoW/LNOoW) achieved the lowest flank wear compared with CA or LN mixed with MQL (CAMQL/LNMQL). Besides, CAMQL had the lowest friction force and coefficient of friction, thus resulting in significant surface roughness, which diminished by 38.4% when compared with dry cutting. The greatest anti-abrasion capability was acquired under LNOoW, wherein the addition of water improved the strength and longevity of the lubrication layer. It was found that the anti-adhesion capacity of the cutting tool increased with the decrease in environmental temperature. Even at cryogenic environment, it is still vital to provide cooling and lubrication to the tool–chip interface for further improving cutting performance.

Bioprospection of native psychrotolerant plant-growth-promoting rhizobacteria from Peruvian Andean Plateau soils associated with Chenopodium quinoa.

The Peruvian Andean Plateau, one of the main production areas of native varieties of Chenopodium quinoa, is exposed to abrupt decreases in environmental temperature, affecting crop production. Plant-growth-promoting rhizobacteria that tolerate low temperatures could be used as organic biofertilizers in this region. We aimed to bioprospect the native psychrotolerant bacteria of the quinoa rhizosphere in this region that show plant-growth-promoting traits. Fifty-one strains belonging to the quinoa rhizosphere were characterised; 73% of the total could grow at low temperatures (4, 6, and 15 °C), whose genetic diversity based on DNA amplification of interspersed repetitive elements (BOX) showed 12 different profiles. According to the 16S rRNA sequence, bacterial species belonging to the classes Beta- and Gammaproteobacteria were identified. Only three (6%) isolates identified as nonpathogenic bacteria exhibited plant-growth-promoting activities, like IAA production, phosphate solubilization, growth in a nitrogen-free medium, and ACC deaminase production at 6 and 15 °C. ILQ215 (Pseudomonas silesiensis) and JUQ307 (Pseudomonas plecoglossicida) strains showed significantly positive plant growth effects in aerial length (about 50%), radicular length (112% and 79%, respectively), and aerial and radicular mass (above 170% and 210%, respectively) of quinoa plants compared with the control without bacteria. These results indicate the potential of both psychrotolerant strains to be used as potential organic biofertilizers for quinoa in this region.

Does social thermal regulation constrain individual thermal tolerance in an ant species?

In ants, social thermal regulation is the collective maintenance of a nest temperature that is optimal for individual colony members. In the thermophilic ant Aphaenogaster iberica, two key behaviours regulate nest temperature: seasonal nest relocation and variable nest depth. Outside the nest, foragers must adapt their activity to avoid temperatures that exceed their thermal limits. It has been suggested that social thermal regulation constrains physiological and morphological thermal adaptations at the individual level. We tested this hypothesis by examining the foraging rhythms of six populations of A. iberica, which were found at different elevations (from 100 to 2,000m) in the Sierra Nevada mountain range of southern Spain. We tested the thermal resistance of individuals from these populations under controlled conditions. Janzen's climatic variability hypothesis (CVH) states that greater climatic variability should select for organisms with broader temperature tolerances. We found that the A. iberica population at 1,300m experienced the most extreme temperatures and that ants from this population had the highest heat tolerance (LT50=57.55°C). These results support CVH's validity at microclimatic scales, such as the one represented by the elevational gradient in this study. Aphaenogaster iberica maintains colony food intake levels across different elevations and mean daily temperatures by shifting its rhythm of activity. This efficient colony-level thermal regulation and the significant differences in individual heat tolerance that we observed among the populations suggest that behaviourally controlled thermal regulation does not constrain individual physiological adaptations for coping with extreme temperatures.