Maximum Temperature Thresholds Research Articles

The use of pulsating jet impingement to minimize temperature oscillations caused by fluctuating heat-flux boundary conditions

Thermal cycling poses a significant challenge in modern applications employing semiconductor devices such as power electronics, owing to the dynamic heat dissipation encountered across diverse operational conditions. The oscillatory variation between peak and low temperatures can induce thermal fatigue, thereby compromising long-term reliability. To address this issue, an innovative approach involving intermittent pulsation of jets has emerged as a promising solution to mitigate peak temperatures and attenuate temperature fluctuations within acceptable limits. This paper presents a comprehensive numerical investigation into the efficacy of intermittent jet impingement in minimizing temperature fluctuations arising from transient heat-flux boundary conditions across a frequency spectrum ranging from 1 to 25 Hz. Comparative analysis against steady jets reveals that intermittent jet pulsation enables superior control over maximum temperature thresholds. An enhancement factor is introduced to quantitatively assess the effectiveness of intermittent jet pulsation, elucidating that up to 8.2 Hz, the reduction in temperature oscillation is notably enhanced compared to higher frequencies. A reduced model is developed to facilitate estimation of transient heat-transfer coefficients during the off period of the jet, shedding light on the underlying mechanisms driving enhanced heat transfer under intermittent jet conditions due to vorticity rings.

The Oxidation of ZrB2/MoSi2 Ceramics in Dissociated Air: The Influence of the Elaboration Technique.

In order to investigate the most extreme conditions in which materials potentially applicable in reusable thermal shields can be operated, ultra-high-temperature ZrB2 ceramics with 20 vol.% MoSi2 were prepared using two different techniques, cold isostatic pressing (CIP) and robocasting (RC, an additive manufacturing technique), followed by consolidation using pressureless spark plasma sintering (SPS). The oxidation behavior of the resulting materials was analyzed in low-pressure dissociated air at three different temperatures, namely 1800, 2000 and 2200 K. Using XRD and surface and cross-section SEM (coupled with EDS), zirconia was found to form at all three temperatures, while silica was only present at 1800 K, with gaseous SiO forming at a higher temperature. The elaboration technique influences the density of the ceramic, and less dense materials undergo deeper oxidation. This investigation suggests that 2000 K is already beyond the maximum temperature threshold at which damage to ceramics is limited by the formation of protective silica. This study confirms that the selected material is a promising candidate for thermal protection applications.

Examining the impact of dry climates temperature on citrus fruit internal ripening

High temperatures alter the ripening process of citrus fruit, affecting quality, flavor, harvest time and marketing period. For example, citrus fruits ripen faster and are sweeter in tropical hot-humid climates than in Mediterranean warm-dry climates due to higher sugar accumulation and organic acid catabolism. Considering that: 1) over 60 % of the world's citrus exports come from countries with warm Mediterranean climates, and 2) the Mediterranean region is warming 20 % faster than the global average, the citrus industry will face significant challenges in the coming years. The range of high temperatures and the timing at which they determine sugar and acid content in dry climates have not been studied under field conditions. Therefore, a study was undertaken over 6 years to determine the relationship between high temperature and citrus ripening in two dry macroclimates, hot (Arid, in Morocco) and warm (Mediterranean, in Spain), and 5 microclimates of the Mediterranean region.Heat stress in these dry climates correlates with changes in fruit quality (lower juice and sugar content, and higher organic acids), depending on the maximum temperature threshold and the time of onset and duration of heat. In the arid climate, the heat stress threshold was found to be a significant number of days above 35 °C. This was particularly important at the beginning of summer (July in the northern hemisphere). However, in the current Mediterranean climate of Spain, the percentage of summer days above 35 °C is still low indicating that other microclimatic conditions are involved in determining fruit quality. In particular, an increase in the number of days with temperatures between 27 °C and 33 °C in late summer and early autumn was found to correlate with reduced citric acid concentration. Microclimate did not determine sucrose, fructose, and glucose concentrations.

Thresholds and extent of temperature effects on maize yield differ in different grain-filling stages

Temperature is a vital environmental factor affecting grain filling and maize yield. The response of maize yield to temperature at different stages of grain filling, however, remains uncharacterized. This study used “Zhengdan 958” as the test material to analyze the high-temperature threshold and yield sensitivity of grain-filling in different periods without water stress by using the data from staging sowing experiments at agro-meteorological experimental stations in Hebi and Suzhou in the Huang-Huai-Hai Plain from 2019 to 2022. The results demonstrated that: (1) the maximum temperature threshold was different in various periods of maize grain-filling in the Huang-Huai-Hai Plain, showing the early grain-filling period (EP) > the active grain-filling period (AP) > the late grain-filling period (LP). With the largest differences in temperature thresholds found in AP, the maximum temperature threshold of AP can better reflect the characteristics of grain filling rather than the whole filling period. (2) The heat of the grain-filling period can explain more than 80 % of the yield variation and affect the yield by influencing the number of days required to reach the maximum grain-filling rate (Vmaxd) and the duration of the active grain-filling period (DAP). (3) The growing degree days (GDD) is the most significant controlling factor affecting yield; however, the effect of heat degree days (HDD) cannot be ignored. The HDD and cumulative thresholds of HDD in the EP and AP of grain-filling can better reflect the effect of heat on yield. The accumulation thresholds of HDD at Hebi and Suzhou were 28.1 °C·d and 15.2 °C·d in the EP period, and 31.0 °C·d and 14.9 °C·d in the AP period, respectively. The results provide a basis for the precise identification of heat disasters during grain-filling and the scientific adjustment of sowing dates.

Identifying heat thresholds for South Africa towards the development of a heat-health warning system.

Exposure to heatwaves may result in adverse human health impacts. Heat alerts in South Africa are currently based on defined temperature-fixed threshold values for large towns and cities. However, heat-health warning systems (HHWS) should incorporate metrics that have been shown to be effective predictors of negative heat-related health outcomes. This study contributes to the development of a HHWS for South Africa that can potentially minimize heat-related mortality. Distributed lag nonlinear models (DLNM) were used to assess the association between maximum and minimum temperature and diurnal temperature range (DTR) and population-adjusted mortality during summer months, and the effects were presented as incidence rate ratios (IRR). District-level thresholds for the best predictor from these three metrics were estimated with threshold regression. The mortality dataset contained records of daily registered deaths (n = 8,476,532) from 1997 to 2013 and data for the temperature indices were for the same period. Maximum temperature appeared to be the most statistically significant predictor of all-cause mortality with strong associations observed in 40 out of 52 districts. Maximum temperature was associated with increased risk of mortality in all but three of the districts. Our results also found that heat-related mortality was influenced by regional climate because the spatial distribution of the thresholds varied according to the climate zones across the country. On average, districts located in the hot, arid interior provinces of the Northern Cape and North West experienced some of the highest thresholds compared to districts located in temperate interior or coastal provinces. As the effects of climate change become more significant, population exposure to heat is increasing. Therefore, evidence-based HHWS are required to reduce heat-related mortality and morbidity. The exceedance of the maximum temperature thresholds provided in this study could be used to issue heat alerts as part of effective heat health action plans.

Thermal risk analysis for winter-spring maize (Zea mays L.) in the Yaqui Valley Sonora, Mexico

The state of Sonora in Mexico contributed with 2.8 % of the maize national production (788,885.77 t) in 2021; however, its production has been affected by low temperatures. The objective was to analyze the effect of minimum (MINTT < 3 °C) and maximum temperature threshold levels (MAXTT > 33 °C) on maize production. Five commercial fields sown with hybrid Hipotótamo and five with DK-4050 were selected in the Yaqui Valley. Temperature data were obtained from the automated weather station network in the state from December 2021 to June 2022. The minimum temperatures recorded between March 8 and 10, 2022, covered about 35 % of the total area sown with maize in southern Sonora. Foliar damage as shown by necrosis between the 5th and 10th leaf oscillated from 3 to 12 %, and it was associated with a temperature range of 1.05 and 4.30 ºC. Frost severity was not significant, so the crop recovered by the production of new leaves. From April, different periods of days with different continuous hours with MAXTT were recorded by weather stations; the highest number of periods occurred in fields B-419 and B-1101 with six. The highest number of hours with MAXTT was recorded in B-1922 with 374, followed by B-419 with 288. Hipopótamo showed the highest grain yield in field B-1101 (16.62 t ha-1). Damage by MAXTT to maize production during 2021-2022 winter-spring season, caused a reduction of 1.53 t ha-1 in relation to the regional average in the previous season.

Effects of Temperature on the Developmental and Reproductive Biology of North American Bean Thrips, Caliothrips fasciatus (Pergande) (Thysanoptera: Thripidae: Panchaetothripinae).

North American bean thrips, Caliothrips fasciatus, native to California U.S., has been detected inside the navels of navel oranges exported from California for more than 120 years. Despite this long history of accidental movement into new areas, this thrips has failed to establish populations outside of its native range. The cold accumulation hypothesis postulates that increasing levels of cold stress experienced by thrips overwintering inside navels is compounded when harvested fruit is shipped under cold storage conditions. Consequently, the fitness of surviving thrips is compromised, which greatly diminishes invasion potential. At the time this study was conducted, the effects of temperature on C. fasciatus fitness were unknown. To address this shortcoming, the effects of nine fluctuating temperatures that averaged 8, 10, 15, 20, 25, 30, 32, 35, and 37 °C over a 24 h period on the developmental and reproductive biology of C. fasciatus were evaluated. One linear and five nonlinear regression functions were fit to egg-to-adult development rate data for parent and offspring thrips to characterize thermal performance curves. Estimates of minimum, optimal, and maximum temperature thresholds for development were in the ranges of -4.37-6.52 °C (i.e., Tmin), 31.19-32.52 °C (i.e., Topt), and 35.07-37.98 °C (i.e., Tmax), respectively. Degree day accumulation to complete development, estimated from linear regression, ranged 370.37-384.61. Average development times for eggs, first and second instar larvae, propupae, pupae, and adult longevity, and mean lifetime fecundity of females were significantly affected by temperature. These biological responses to temperature may provide insight into how this abiotic variable affects the invasion potential of C. fasciatus.

Spatial Variability of Summer Temperature and Related All-cause Mortality from 2006 to 2015 for Indian Cities: A Time Series Analysis

Abundant literature is available on an extremely high temperature associated with mortality for cities of the developed world, but there is a dearth in the literature for coastal, desert and dry cities of the developing world, especially for India. We examined all-cause mortality and extreme high temperature in three Indian cities representing coastal, desert and dry areas for summer months (March to June) from 2006 to 2015. We obtained the data on temperature and all-cause mortality for ten years for the summer months. The city-specific effect of ambient heat on all-cause mortality was assessed through time series ordinary least square linear regression model. A total of 75,571, 122,117 and 53,042 deaths for 1,203, 1,220 and 1,180 summer days from 2006 to 2015 were analysed with ambient temperature for Jaipur, Hyderabad and Surat, respectively. There were 994 (27.6%) out of 3,603 summer days having temperature ≥40°C and 2,495 (69.3%) out of 3,602 summer days having feel temperature/heat index (HI) of ≥41°C. According to the Indian Meteorological Department (IMD) criteria for the heatwave, Surat has the maximum number of 75 days with a maximum temperature of ≥40°C, whereas Hyderabad has only 4 days and Jaipur faced 35 days with a maximum temperature of ≥45°C during the study period. The per-day mean all-cause mortality increased to 39% and 11% for Jaipur and Hyderabad, respectively, at ≥45°C and 20% for the coastal city of Surat at ≥40°C as per IMD heatwave criteria. A time-series linear regression model shows that adjusted R-squared is 0.593, 0.629 and 0.348, which explained the variation of 59.3%, 62.9% and 34.8% for all-cause mortality (dependent variable) by independent variables (maximum temperature, humidity and HI) for Jaipur, Hyderabad and Surat, respectively. The maximum temperature threshold (cut-off) for all-cause mortality for Jaipur, Hyderabad and Surat is 42°C, 41°C and 40°C, respectively. The impact of ambient heat in the rise of all-cause mortality for all study sites was evident. Hence, findings support the efforts for reducing the public health burden of high ambient temperature through developing and implementing city-specific heat action plans.

Effect of pedoclimatic variables on analytical and organoleptic characteristics in olive fruit and virgin olive oil

Due to the expansion of olive oil cultivation around the world and the increasing effects of climate change, Olea europaea (L:) cultivation must deal with ever higher temperatures and drought conditions, with productivity and virgin olive oil (VOO) quality issues. At the same time the demand for premium quality products with high nutraceutical value, chemical and organoleptic characteristics related to specific areas of cultivation is steadily rising. Within this framework a deep knowledge of the olive variety with regards to environment interaction is necessary to achieve VOO production and qualitative standards required by the market. Rainfed adult olives (cv Bosana) cultivated in five typical areas of north and central Sardinia (Italy) were the subject of a three-year study, with the aim to investigate the influence of pedoclimatic variability on olive and olive oil characteristics. Physical and chemical attributes of fruits (morphometric features, firmness, pH, titratable acidity, sugar content, moisture, and oil yield) and VOO (fatty acid and sensory profile) were analysed at harvest and related to monthly weather data (precipitation, maximum, average, and minimum temperatures) of the whole fruit development period and soil composition. Monthly maximum temperatures were the most relevant variables. However, the role of each meteorologic variable was specific per olive and olive oil parameters and their relevance varied according to the period of the season. An emblematic example is that the maximum temperatures during summer months reduced oil yield and improved oleic acid concentration, but during the following months, the same variable exerted an opposite effect. This suggests the presence of a maximum temperature threshold in the olive fruits, for lipogenesis processes. Meteoclimatic conditions during maturation were the principal element responsible for VOO sensory profile: high precipitation and low thermal amplitude promoted an attribute’s intensities.

Study on adaptive parameter internal mode control method for argon-oxygen refining ferrochrome alloy

To enhance the rate of argon–oxygen refining of ferroalloys, this article is based on the physical and chemical reactions of the smelting process as well as the actual smelting data. A mechanistic model of the rate of change of oxygen supply and carbon content in the smelting process and the temperature of the reaction fluid in the furnace is established. An expert internal model control framework with furnace temperature and carbon content as output and oxygen supply rate as input is constructed. An adaptive parameter adjustment mechanism is added to the control framework by combining data on the maximum gas supply rate and temperature threshold of the stage in the actual production process. The method improves smelting speed and smelting accuracy compared to the general method. It is also able to adjust the furnace temperature according to the actual smelting situation. The actual smelting was carried out according to this method, the improved method reduced the smelting time by 12.79% compared to the general method, and the furnace temperature was controlled below 1950 K.

Pest categorisation of Paracoccus marginatus.

The EFSA Panel on Plant Health performed a pest categorisation of Paracoccus marginatus (Hemiptera: Sternorrhyncha: Pseudococcidae), the papaya scale, for the EU. It is native to Central America and since the 1990s, it has spread rapidly in mainly tropical areas of the Caribbean, islands in the Indian and Pacific Oceans, Africa and southern Asia. Large populations were detected in northern Israel in 2016. It has not been reported within the EU. It is not listed in Annex II of Commission Implementing Regulation (EU) 2019/2072. It reproduces sexually and there are up to 11 generations per year in India. The estimated minimum, optimum and maximum temperature thresholds for the adult females are 13.9, 28.4 and 32.1°C, respectively. First-instar nymphs may move to neighbouring plants by crawling, or be passively dispersed by wind, or hitchhiking on clothing, equipment or animals. It is highly polyphagous, feeding on plants in 172 genera and 54 families. It is an important pest of custard apple (Annona spp.), papaya (Carica papaya) and Hibiscus spp. It also feeds on a wide range of plants cultivated in the EU such as eggplant (Solanum melongena), avocado (Persea americana), citrus (Citrus spp.), cotton (Gossypium hirsutum), grapevine (Vitis vinifera), guava (Psidium guajava), mango (Mangifera indica), passionfruit (Passiflora edulis), pomegranate (Punica granatum), pepper (Capsicum annuum) and tomato (Solanum lycopersicum). Plants for planting, fruits, vegetables and cut flowers are the main potential pathways for entry of P. marginatus into the EU. Climatic conditions in the warmest areas of Cyprus, Greece, Italy and Spain, where host plants occur, would likely allow this species to successfully establish and spread. Reductions in yield and quality of some cultivated hosts including Annona spp., Hibiscus spp. and papaya are anticipated if establishment occurs. Phytosanitary measures are available to reduce the likelihood of entry and spread. P. marginatus meets the criteria that are within the remit of EFSA to assess for this species to be regarded as a potential Union quarantine pest.

Limits on phenological response to high temperature in the Arctic

Tundra plants are widely considered to be constrained by cool growing conditions and short growing seasons. Furthermore, phenological development is generally predicted by daily heat sums calculated as growing degree days. Analyzing over a decade of seasonal flower counts of 23 plant species distributed across four plant communities, together with hourly canopy-temperature records, we show that the timing of flowering of many tundra plants are best predicted by a modified growing degree day model with a maximum temperature threshold. Threshold maximums are commonly employed in agriculture, but until recently have not been considered for natural ecosystems and to our knowledge have not been used for tundra plants. Estimated maximum temperature thresholds were found to be within the range of daily temperatures commonly experienced for many species, particularly for plants at the colder, high Arctic study site. These findings provide an explanation for why passive experimental warming—where moderate changes in mean daily temperatures are accompanied by larger changes in daily maximum temperatures—generally shifts plant phenology less than ambient warming. Our results also suggest that many plants adapted to extreme cold environments may have limits to their thermal responsiveness.

Increased Handpiece Speeds without Air Coolant: Aerosols and Thermal Impact

This study assessed the impact of increased speed of high-speed contra-angle handpieces (HSCAHs) on the aerosolization of a severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) surrogate virus and any concomitant thermal impact on dental pulp. A bacteriophage phantom-head model was used for bioaerosol detection. Crown preparations were performed with an NSK Z95L Contra-Angle 1:5 (HSCAH-A) and a Bien Air Contra-Angle 1:5 Nova Micro Series (HSCAH-B) at speeds of 60,000, 100,000, and 200,000 revolutions per minute (rpm), with no air coolant. Bioaerosol dispersal was measured with Φ6-bacteriophage settle plates, air sampling, and particle counters. Heating of the internal walls of the pulp chambers during crown preparation was assessed with an infrared camera with HSCAH-A and HSCAH-B at 200,000 rpm (water flows ≈15 mL min−1 and ≈30 mL min−1) and an air-turbine control (≈23.5 mL min−1) and correlated with remaining tissue thickness measurements. Minimal bacteriophage was detected on settle or air samples with no notable differences observed between handpieces or speeds (P > 0.05). At all speeds, maximum settled aerosol and average air detection was 1.00 plaque-forming units (pfu) and 0.08 pfu/m3, respectively. Irrespective of water flow rate or handpiece, both maximum temperature (41.5°C) and temperature difference (5.5°C) thresholds for pulpal health were exceeded more frequently with reduced tissue thickness. Moderate and strong negative correlations were observed based on Pearson’s correlation coefficient, between remaining dentine thickness and either differential (r = −0.588) or maximum temperature (r = −0.629) measurements, respectively. Overall, HSCAH-B generated more thermal energy and exceeded more temperature thresholds compared to HSCAH-A. HSCAHs without air coolant operating at speeds of 200,000 rpm did not increase bioaerosolization in the dental surgery. Thermal risk is variable, dependent on handpiece design and remaining dentine thickness.

Potential Impacts of Different Occupational Outdoor Heat Exposure Thresholds among Washington State Crop and Construction Workers and Implications for Other Jurisdictions.

Occupational heat exposure is associated with substantial morbidity and mortality among outdoor workers. We sought to descriptively evaluate spatiotemporal variability in heat threshold exceedances and describe potential impacts of these exposures for crop and construction workers. We also present general considerations for approaching heat policy-relevant analyses. We analyzed county-level 2011–2020 monthly employment (Bureau of Labor Statistics Quarterly Census of Employment and Wages) and environmental exposure (Parameter-elevation Relationships on Independent Slopes Model (PRISM)) data for Washington State (WA), USA, crop (North American Industry Classification System (NAICS) 111 and 1151) and construction (NAICS 23) sectors. Days exceeding maximum daily temperature thresholds, averaged per county, were linked with employment estimates to generate employment days of exceedances. We found spatiotemporal variability in WA temperature threshold exceedances and crop and construction employment. Maximum temperature exceedances peaked in July and August and were most numerous in Central WA counties. Counties with high employment and/or high numbers of threshold exceedance days, led by Yakima and King Counties, experienced the greatest total employment days of exceedances. Crop employment contributed to the largest proportion of total state-wide employment days of exceedances with Central WA counties experiencing the greatest potential workforce burden of exposure. Considerations from this analysis can help inform decision-making regarding thresholds, timing of provisions for heat rules, and tailoring of best practices in different industries and areas.

Spatio-Temporal Variation of Extreme Heat Events in Southeastern Europe

Many studies in the last few years have been dedicated to the increasing temperatures and extreme heat in Europe since the second half of the 20th century because of their adverse effects on ecosystems resilience, human health, and quality of life. The present research aims to analyze the spatio-temporal variations of extreme heat events in Southeastern Europe using daily temperature data from 70 selected meteorological stations and applying methodology developed initially for the quantitative assessment of hot weather in Bulgaria. We demonstrate the suitability of indicators based on maximum temperature thresholds to assess the intensity (i.e., magnitude and duration) and the tendency of extreme heat events in the period 1961–2020 both by individual stations and the Köppen’s climate zones. The capability of the used intensity-duration hot spell model to evaluate the severity of extreme heat events has also been studied and compared with the Excess Heat Factor severity index on a yearly basis. The study provides strong evidence of the suitability of the applied combined approach in the investigation of the spatio-temporal evolution of the hot weather phenomena over the considered domain.

Safe at Home?

Problem, research strategy, and findings Indoor residential environments will be an increasing source of dangerous heat exposure as summer temperatures rise. Although air conditioning is a recognized preventative measure, many vulnerable residents either lack air conditioning or cannot always afford the electricity. Understanding the relative influence of different building characteristics and percentages of tree canopy coverage on indoor air temperatures during extreme heat events can help prioritize intervention strategies. We measured indoor and outdoor temperatures at 140 homes in Detroit (MI), Atlanta (GA), and Phoenix (AZ) and surveyed residents to determine the presence of a working central air-conditioning system and their ability to afford utilities. For each home, we collected information on construction year, interior size, single versus multifamily structure, façade type, and percentage of tree canopy. After air conditioning, the importance of building characteristics versus tree canopy measures varied by city. In Detroit, masonry façades worsened the influence of outdoor temperatures, whereas increased tree canopy coverage moderated the influence. In Atlanta, building characteristics were not significant, but tree canopy moderated indoor temperatures in late afternoon. In Phoenix, some building characteristics moderated the influence of outdoor temperatures in late afternoon. Takeaway for practice In Detroit, only 35% of respondents had and used central air conditioning as needed compared with 57% in Atlanta and 95% in Phoenix. The influence of tree canopy and building characteristics on indoor temperatures varied by city depending on its background climate. We recommend adding questions about air conditioning and utility poverty to the U.S. Census. For rental properties, municipalities should establish and enforce maximum indoor temperature thresholds. States should include cooling in their Low Income Home Energy Assistance (LIHEAP) programs. Public cooling centers need to anticipate electricity outages. Urban planners must ensure efforts to increase mechanical cooling are powered by renewable energy sources.

Disentangling thermal effects using life cycle simulation modelling on the biology and demographic parameters of Dolichogenidea gelechiidivoris, a parasitoid of Tuta absoluta

Dolichogenidea gelechiidivoris (Marsh) (Syn. Apanteles gelechiidivoris) (Hymenoptera: Braconidae), a konoibiont larval endoparasitoid of the South American tomato pinworm Tuta absoluta (Meyrick), was imported into Kenya in 2017 for the first classical biological control of T. absoluta in Africa. We determined the thermal thresholds of D. gelechiidivoris, with T. absoluta as host, using life cycle simulation modelling. Life-table data of D. gelechiidivoris were generated at six constant temperatures (10, 15, 20, 25, 30, and 35 °C, 65 ± 5% RH, and 12L: 12D photoperiod). Multiple non-linear functions were fitted to model some aspects of the biology of the parasitoid, including its longevity, mortality, reproduction, and senescence using Insect Life Cycle Modelling (ILCYM) software. The phenology models established were used to estimate life table parameters. Except at 35 °C, D. gelechiidivoris completed its development (i.e., egg-larval-pupa-adult) at all tested temperatures. The minimum temperature threshold from egg to cocoon was 7.0 °C and 5.9 °C from cocoon to adult wasp, while the maximum temperature thresholds were 34 °C and 36 °C, respectively. The optimal temperature for immature survival was 20–25 °C, while fecundity was optimum at 22.5 °C, with 69.5 eggs per female. Simulations of the population growth parameters indicated that the intrinsic rate of increase (rm) was maximum at 20 °C with 15 daughters per female per generation. Based on our findings the release of D. gelechiidivoris for inoculative augmentation in countries with temperatures ranging between 15 and 30 °C could be considered to control the pest.

Global population densities, climate change, and the maximum monthly temperature threshold as a potential tipping point for high urban densities

Heat waves lasting days or weeks are among potential hazards expected to increase with climate change, but beyond heat waves, sustained temperatures may be incompatible with high urban population densities. I examined patterns of population density classes and exposure to maximum monthly temperature to identify where high urban population density classes were more at risk for prolonged heat than other density classes and if heat may have influenced high urban population densities during the recent past (1970–2000). Then, I considered exposure of population density classes to maximum monthly temperature during the near future (2021–2040, under the sustainability shared socio-economic pathway ssp1-2.6) and the long-range future (2081–2100, under fossil fuel-driven ssp5-8.5) for three general circulation models. Population densities generally increased with increasing maximum monthly temperature by country; the highest density urban class had the greatest exposure to heat for 82 out of 199 countries. By temperature zone, the hypertropical zone inverted the order such that population densities increased with decreasing maximum monthly temperature, indicating that concentrated populations generally did not develop at high maximum monthly temperatures ≥ 36 °C. The 36 °C maximum monthly temperature threshold corresponds to heat wave warnings, which typically consist of a few consecutive days. Therefore, 36 °C maximum monthly temperature may indicate the start of an inhospitable tipping point beyond which human civilization may not flourish. Most land area will exceed 36 °C maximum monthly temperature under the CanESM5 ssp5-8.5 scenario by 2081–2100. Adaptation is not sufficient to moderate sustained unrelenting heat and migration of human populations would be less feasible than mitigation to reduce carbon emissions.

Heatsinks to Cool Batteries for Unmanned Aerial Vehicles

This study aims to develop several different models of heatsinks, designed to cool a vertical take-off and landing unmanned aerial vehicle (UAV) battery, through topology optimization, aimed at being manufactured through selective laser melting (SLM) technology. A battery’s temperature must be properly managed for a safe and efficient operation. The methodology developed was with the support of software to carry out several simulations which, starting from several scenarios and restrictions imposed by the small space available to accommodate these small batteries in this type of aircraft. The conception resulted in several battery thermal management systems (BTMS) models, with different applications and efficiency degrees. A relevant aspect is the topology optimization being coupled to computational thermal analysis to reduce the mass of the heatsink whilst ensuring a maximum battery temperature threshold. Together with the use of topology optimization, the SLM process was selected to manufacture the heat sinks, under conditions of geometric freedom, using several high thermal conductivity metal alloys, such as, aluminium and copper to obtain the designed models.

Determination of temperature thresholds for the parasitoid Diachasmimorpha longicaudata (Hymenoptera: Braconidae), using life cycle simulation modeling: Implications for effective field releases in classical biological control of fruit flies

The braconid parasitoid Diachasmimorpha longicaudata (Ashmead) (Hymenoptera: Braconidae) is one of the most important natural enemies in classical biological control programs against tephritid fruit flies worldwide. In light of the spread of the invasive fruit fly species, Bactrocera dorsalis in Africa and beyond, there is a need to implement classical biological control. The current study aimed to determine temperature thresholds for D. longicaudata reared on B. dorsalis, using life cycle simulation modeling to guide informed parasitoid releases in Africa. Simulated parameters included thermal requirements, population growth parameters at different temperature requirements, suitable areas for the establishment, and the number of generations per year under projected climatic conditions. The lower thermal threshold for the development was estimated at 10.0°C, with a thermal constant (k) of 333.3-degree days, while the maximum temperature threshold was estimated at 33.69°C. Fecundity was highest at 25°C, with 177.3 eggs per female. Temperature significantly affected the population growth parameters of D. longicaudata, and the maximum value of the intrinsic rate of increase (rm) was 0.145 at 27°C. Results indicate that D. longicaudata could successfully establish in tropical and sub-tropical regions under current and future climatic conditions. However, a slight change in the suitable areas is expected by the year 2050 due to a slight and gradual rise in temperature. Our findings provide important information for further release of this parasitoid in Africa as well as designing pest management strategies to limit the spread and reduce the impact of fruit flies sustainably.