Hot-dry Environment Research Articles

Critical environmental core temperature limits and heart rate thresholds across the adult age span (PSU HEAT Project).

The frequency, duration, and severity of extreme heat events have increased and are projected to continue to increase throughout the next century. As a result, there is an increased risk of excessive heat- and cardiovascular-related morbidity and mortality during these extreme heat events. Therefore, the purposes of this investigation were to establish 1) critical environmental core temperature (Tc) limits for middle-aged adults (MA), 2) environmental thresholds that cause heart rate (HR) to progressively rise in MA and older (O) adults, and 3) examine critical environmental Tc limits and HR environmental thresholds across the adult age span. Thirty-three young (Y) (15 F; 23 ± 3 yr), 28 MA (17 F; 51 ± 6 yr), and 31 O (16 F; 70 ± 3 yr) subjects were exposed to progressive heat stress in an environmental chamber in a warm-humid (WH, 34-36°C, 50-90% rh) and a hot-dry (HD, 38°C-52°C, <30% rh) environment while exercising at a low metabolic rate reflecting activities of daily living (∼1.8 METs). In both environments, there was a main effect of age on the critical environmental Tc limit and environmental HR thresholds (main effect of age all P < 0.001). Across the lifespan, critical environmental Tc and HR thresholds decline linearly with age in HD environments (R2 ≥ 0.3) and curvilinearly in WH environments (R2 ≥ 0.4). These data support an age-associated shift in critical environmental Tc limits and HR thresholds toward lower environmental conditions and can be used to develop evidence-based safety guidelines to minimize future heat-related morbidity and mortality across the adult age span.NEW & NOTEWORTHY This study is the first to identify critical environmental core temperature and heart rate thresholds across the adult age spectrum. In addition, our data demonstrate that the rate of decline in Tc and HR limits with age is environmental-dependent. These findings provide strong empirical data for the development of safety guidelines and policy decisions to mitigate excessive heat- and cardiovascular-related morbidity and mortality for impending heat events.

Critical Environmental Limits for Middle-Aged Adults (PSU HEAT Project)

Critical environmental limits are the combinations of temperature and humidity above which heat balance cannot be maintained for a given metabolic heat production. Our lab has previously established critical environmental limits for young and older adults; however, these limits have yet to be established for middle-aged adults. The purpose of the present study was to (1) identify critical environmental limits for middle-aged adults, and (2) investigate age-related differences in critical environmental limits at a low metabolic rate reflecting activities of daily living across the adult age spectrum. Twenty-six older (71±5 yrs, 14F/12M), 36 middle aged (51±9 yrs, 26F/10M), and 27 young adults (23±3 yrs, 13F/14M) were exposed to progressive heat stress in a controlled environmental chamber during minimal activity. Progressive heat stress for the determination of critical environmental limits comprised either (1) constant dry-bulb (Tdb) temperature at 34°C with progressively increasing water vapor pressure (Pa) by 1 mmHg every 5 minutes (Pcrit trial), or (2) constant Pa at 12 mmHg with progressively increasing Tdb by 1°C every 5 minutes (Tcrit trial). Critical environmental limits in hot-dry environments were higher in young compared to middle aged (49.3±2.3 °C vs. 45.4±4.0 °C; p = 0.002) and older adults (49.3±2.3°C vs. 43.2±4.0°C; p &lt; 0.001), but were not different between middle aged and older adults (45.4±4.0 °C vs. 43.2±4.0°C; p = 0.125). Critical environmental limits in warm-humid conditions were lower in older adults compared to young (23.1±6.1 mmHg vs 31.7±1.5 mmHg, p &lt; 0.001) and middle aged (23.1±6.1 mmHg vs 29.0±5.1 mmHg, p = 0.004), but were not different between the young and middle aged (31.7±1.5 mmHg vs 29.0±5.1 mmHg, p = 0.220). Age was correlated with critical environmental limits in Tcrit (R2 = 0.34; p &lt; 0.001) and Pcrit (R2 = 0.51; p &lt; 0.001) trials based on linear and curvilinear regression, respectively. Critical environmental limits for middle aged adults performing minimal activity in warm-humid and hot-dry environments are intermediate to young and older adults. These data demonstrate an age-related decline in critical environmental limits that can be characterized by linear decline in hot-dry environments and by curvilinear decline in warm-humid environments. Supported by NIH Grant R01 AG067471. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Age-Related Differences in the Onset of Cardiovascular Drift during Progressive Heat Stress (PSU HEAT Project)

As a result of the increasing duration, frequency, and severity of heat waves, older men and women are at greater risk for heat-related morbidity and mortality, with the majority of excess heat-related deaths attributed to increased cardiovascular strain associated with heat stress. PURPOSE: To (1) identify the environmental conditions (ambient temperature (Tdb) and humidity (rh)) at which heart rate (HR) begins to increase from equilibrium (i.e., the onset of cardiovascular drift), and (2) compare the environments in which cardiovascular drift begins relative to those at which a continuous rise in core temperature (Tc) is observed in young (Y), middle (MA), and older (O) adults. Methods: 26 Y (10 F; 19-29 yrs), 27 MA (21F; 40-64 yrs), and 19 O (7 F; 65-76 yrs) subjects were exposed to progressive heat stress in an environmental chamber at a low metabolic rate reflecting activities of daily living (159 ± 34 W) in a warm-humid (WH, 34-36°C, 50-80% rh) and a hot-dry (HD, 38°C-52°C, &lt;30% rh) environment. The environmental thresholds above which HR and Tc equilibrium could no longer be maintained were identified. Results: In WH environments, sustained increases in HR preceded the Tc inflection point in Y (73±5% rh vs. 81±5% rh; p&lt;0.001), MA (67±11% rh vs. 73±12% rh; p&lt;0.001), and O adults (53±11% rh vs. 57±12% rh; p=0.041). Similarly, in HD (15-20% rh) environments, the onset of cardiovascular drift preceded the Tc inflection point in Y (47±3°C vs. 49±3°C; p=0.004), MA (44±4°C vs. 46±4°C; p&lt;0.001), and O adults (42±5°C vs. 44±4°C; p=0.007). Additionally, in WH environments, cardiovascular drift began at lower combinations of Tdb and rh in O vs. Y subjects (34°C, 53±11% rh vs. 34°C, 73±5% rh; p&lt;0.001) and O vs. MA adults (34°C, 53±11% rh vs. 34°C, 67±11% rh; p=0.008). In HD environments, cardiovascular drift began at lower environments in MA vs. Y (44±4°C, 18% rh vs. 47±3°C, 15% rh; p=0.044) and O vs. Y (42±5°C, 20% rh vs. 47±3°C, 15% rh; p=0.006) CONCLUSION: These data suggest that cardiovascular drift, indicating increases in cardiovascular strain, occurs during compensable heat stress at metabolic rates reflecting activities of daily living in Y, MA, and O adults. Further, there is an age-associated shift in the onset of cardiovascular drift toward lower combinations of Tdb and rh. SIGNIFICANCE/NOVELTY: These results are the first to identify the specific environmental conditions at which increases in cardiovascular strain occur across the adult age spectrum. These findings provide concrete data for the development of safety guidelines and policy decisions to mitigate cardiovascular-related morbidity and mortality during impending heat events. Supported by NIA Grant T32 AG049676 (to R.M.C.) and NIH Grant R01 AG067471 (to W.L.K.). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Thermal effects of rayon and polyester hijabs in warm-humid and hot-dry environments

Hijabs are predominantly worn in hot environments, but very rare studies on the thermo-physiological effects of wearing hijabs are found. We investigated the effects of wearing rayon and polyester hijabs on wearers’ physiological and subjective responses in warm-humid and hot-dry environments. Eight females (25.0 ± 2.3 y in age, 157.7 ± 4.1 cm in height, and 50.8 ± 7.5 kg in weight) participated in three conditions (No hijab, rayon hijab, and polyester hijab condition) during exercise in two thermal environments: a warm-humid (30 °C and 70%RH) and a hot-dry environment (36 °C and 30%RH), which generated an identical wet-bulb globe temperature at 27 °C. The results showed that no differences in rectal temperature were found among the three clothing conditions or the two environments, whereas auditory canal temperature was higher in the hot-dry than in the warm-humid environment (P < 0.05) with no differences between the polyester and rayon hijab conditions. Mean skin temperature and neck temperature were higher for the polyester condition than for the rayon condition in the warm-humid environment (P < 0.05). Sweat rate was greater for the polyester hijab condition than for the no hijab condition in the warm-humid environment (P = 0.049). Heart rate was greater for the polyester hijab condition than for the other two conditions in the warm-humid environment (P < 0.05). Subjects felt more thermally uncomfortable when wearing the polyester hijab than the rayon hijab in the warm-humid environment. Greater thermal burden of the polyester hijab when compared to the rayon hijab was marked in the warm-humid environment, not in the hot-dry environment.

The Mars as the Parent Body of CI Carbonaceous Chondrites Hypothesis Re-Examined in the Light of New Data

It had been proposed that the parent body for the CI carbonaceous was the planet Mars. New data strongly supports this hypothesis. The recovery of CI-like material from the asteroid Ryugu, which orbits near Mars has confirmed the importance of CI material as a source of water for the terrestrial planets. The oxygen isotope makeup of the CI is now seen to overlap the distribution of data from the aqueously altered portions of recognized MMs (Mars Meteorites).The CI consist of completely aqueous altered ferro-magnesian silicates, carbonates and sulfates. The physical conditions that produced these materials match conditions on Early Mars, as inferred from portions of recognized ancient Mars meteorites ALH84001and NWA 7533. Noble and Nitrogen gas isotopes match early Mars atmosphere, especially in N, Kr, Xe, and Ar isotopes with a Mars early atmosphere being composed of Chondritic Xe and Kr. The CI, despite early aqueous alteration, appear to have been, like Chassigny, preserved in a hot dry environment and have preserved entrapped Early Mars atmosphere. The CI can thus be considered to be aqueously altered remnants of a late accretion veneer that largely experienced no melt processing. Portions of this lithology have been thermally altered and formed the CY group. This Mars -CI hypothesis can be tested by chronologies of thermal alteration of the CYs .The CI are rich in organic matter, indicating that Early Mars was warm, wet, and rich in the chemical precursors of life and therefore emulated conditions that fostered life on Early Earth.

Relative influence of individual characteristics on critical WBGT limits in young adults (PSU HEAT Project)

Critical environmental limits are temperature-humidity thresholds above which heat balance cannot be maintained for a given metabolic heat production. This study examined the association between individual characteristics [sex, body surface area (A D ), aerobic capacity (V̇O 2max ; L∙min-1), and body mass (m b )] and critical environmental limits in young adults. Forty-four (20 M/24 F; 23±4 yr) subjects were exposed to progressive heat stress in an environmental chamber at two low net metabolic rates (M net ); minimal activity (MinAct; M net = 160±35 W) and light ambulation (LightAmb; M net = 259±54 W). In 2 hot-dry (HD; &lt;25% rh) environments, ambient water vapor pressure (P a = 12 or 16 mmHg) was held constant and dry-bulb temperature (T db ) was systematically increased. In 2 warm-humid (WH; &gt;50% rh) environments, T db was held constant at 34 or 36 °C and P a was systematically increased. The critical wet-bulb globe temperature (WBGT crit ) was determined for each condition. There were no sex differences in WBGT crit for any condition ( p ≥ 0.21). During MinAct, only m b was retained in a backward linear regression model explaining the variance in WBGT crit in WH (R 2adj = 0.08, p &lt; 0.001), whereas m b and V̇O 2max were retained for HD environments (R 2adj = 0.09, p &lt; 0.001). During LightAmb, m b and A D were retained in the model for both WH (R 2adj = 0.46, p &lt; 0.001) and HD environments (R 2adj = 0.22; p &lt; 0.001). These data demonstrate the relative importance of individual characteristics on WBGTcrit during low-intensity weight-bearing (LightAmb) and non-weight-bearing (MinAct) activity in extreme thermal environments. This work was supported by NIH R01 AG067471. This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Thermally induced fracturing in hot dry rock environments - Laboratory studies

In enhanced geothermal system (EGS) wells, where strong thermal gradients exist, hydraulic fracturing is the apparent driver for creating permeability in the reservoirs. Thermal effects, however, have been observed to accompany hydraulic loading and may further enhance the permeability of the reservoir. The mechanism of thermal fracturing in downhole conditions, however, is not well understood, limiting the efficient engineering of thermal effects on EGS stimulation. This laboratory study examines the behavior of thermal shock stimulation and temperature propagation by flowing room-temperature water through a borehole of a hot specimen block without confining stresses or borehole hydraulic loading. This condition isolates the effect of thermal shock from hydraulic pressure and confining stress. We monitored temperatures across the inside of the specimens and assessed fractures by visual inspection, bubble leakage, pressure decay, and acoustics. Thermal loading resulted in an enhancement of permeability by induced macro/microcracks. The profiles of borehole pressure decay obtained before and after each stage of stimulation show increased permeability of the treated specimens. The acoustic measurements indicate the extent of fractures, and the bubble leakage tests on the specimen surface visually indicate localized permeation paths created by newly created cracks. The maximum thermal gradient was achieved near the borehole surface at the start of the water flow. As the flow continued, the magnitude of the thermal gradient near the borehole decreased while that of the thermal gradient away from the borehole increased. Thermally driven fractures, initiated from the borehole walls, propagated perpendicular to the borehole surfaces. These “seed” fractures created during thermal stimulation, although they might be suppressed under very high stress, help reduce the levels of breakdown pressure in concurrent or subsequent pressure-based fracturing methods.

Core temperature responses to compensable versus uncompensable heat stress in young adults (PSU HEAT Project).

With global warming, much attention has been paid to the upper limits of human adaptability. However, the time to reach a generally accepted core temperature criterion (40.2°C) associated with heat-related illness above (uncompensable heat stress) and just below (compensable heat stress) the upper limits for heat balance remains unclear. Forty-eight (22 men/26 women; 23 ± 4 yr) subjects were exposed to progressive heat stress in an environmental chamber during minimal activity (MinAct, 159 ± 34 W) and light ambulation (LightAmb, 260 ± 55 W) in warm-humid (WH; ∼35°C, >60% RH) and hot-dry (HD; 43°C-48°C, <25% RH) environments until heat stress became uncompensable. For each condition, we compared heat storage (S) and the change in gastrointestinal temperature (ΔTgi) over time during compensable and uncompensable heat stress. In addition, we examined whether individual characteristics or seasonality were associated with the rate of increase in Tgi. During compensable heat stress, S was higher in HD than in WH environments (P < 0.05) resulting in a greater but more variable ΔTgi (P ≥ 0.06) for both metabolic rates. There were no differences among conditions during uncompensable heat stress (all P > 0.05). There was no influence of sex, aerobic fitness, or seasonality, but a larger body size was associated with a greater ΔTgi during LightAmb in WH (P = 0.003). The slopes of the Tgi response during compensable (WH: MinAct, 0.06, LightAmb, 0.09; HD: MinAct, 0.12, LightAmb, 0.15°C/h) and uncompensable (WH: MinAct, 0.74, LightAmb, 0.87; HD: MinAct, 0.71, LightAmb, 0.93°C/h) heat stress can be used to estimate the time to reach a target core temperature from any given starting value.NEW & NOTEWORTHY This study is the first to examine heat storage and the rate of change in core temperature above (uncompensable heat stress) and just below (compensable heat stress) critical environmental limits to human heat balance. Furthermore, we examine the influence of individual subject characteristics and seasonality on the change in core temperature in warm-humid versus hot-dry environments. We provide the rate of change in core temperature, enabling projections to be made to and from any hypothetical core temperature.

Manufacture of Shoe Upper Leathers from Sudanese Camel Hides

Sudan is one of the African countries with higher livestock population. The total livestock population of the country is estimated at 31.78 millions of cattle, 41 millions of sheep, 32.22 millions of goats and 4.92 millions of camels. This huge population of livestock provides many opportunities for the development of the leather sector in the country. The main source of raw material for the Sudan tanning sector comes from sheep, goat and cattle. Camel (Camelus dromedarius) is one of the most important livestock uniquely adapted to hot dry environments. Sudan holds the second largest camel population in the world (about 4.92 million). Camels in Sudan and elsewhere are classified as pack (heavy) and riding (light) types according to their function. Recent studies have been made to classify the camels according to their performance (dairy camels, meat camels, dual purpose camels and racing camels). In the present study, camel hides were used for manufacture of upper crust leathers and compare with conventional cow hides. Histological analysis of the camel hide and cow hide has been carried out at soaking operation. The physical and chemical analysis indicates that the experimental camel leathers are comparable to control cow leathers in terms of all the properties. The bulk properties for the experimental leathers are better than control leathers. Scanning electron microscopic analysis for both control and experimental leather samples show good separation of fiber bundles. The chemical and physical characteristics of the experimental camel leather revealed that the camel hide raw material was suitable for making of shoe upper leather. In Sudan camel was considered as best alternative animal to conventional raw materials such as sheep, goat and cattle due to its higher off take rate.

Improvement of Mechanical Properties and Microstructure of Cementitious Materials in a Hot-Dry Environment

The hot-dry environment in high geothermal tunnels negatively affects the development of properties of cementitious materials. In order to improve the mechanical properties of cementitious materials in such environments, a proper curing system was developed, the material compositions were taken into account, and the related mechanism was analyzed by microscopic tests. The results showed that the mechanical properties and microstructure of cementitious materials can be improved effectively by adopting film curing and an adequate dosage of fly ash in a hot-dry environment. Compared with standard curing, a hot-dry environment accelerates the evaporation of water in fresh cementitious materials and the early hydration rate of cementitious materials, resulting in lots of unhydrated cement particles and an uneven distribution of hydration products, seriously decreasing the properties of the cementitious materials. Film curing keeps the water from evaporating and ensures enough water is available for hydration at an early age. The addition of FA reduces the amount of cement clinker and decreases hydration reaction rate in high temperature environments at an early stage, avoiding the unevenness of hydration products. High temperatures stimulate the pozzolanic activity of fly ash and promote the degree of secondary hydration reaction, producing more hydration products, as well as contributing to the improvement of the mechanical properties and microstructure of cementitious materials. In this study, in a hot-dry environment, the mechanical properties of mortar with 25% fly ash and 2–3 d film curing are better than those of other experimental groups, including those of standard curing.

Different scenarios to enhance thermal comfort by renewable-ecological techniques in hot dry environment

Recently, building thermal studies have focused more and more on providing the right living conditions inside buildings, houses, schools, hospitals, etc., especially in hot-dry regions to defeat energy consumption dilemmas generally coming from fossil fuels source by renewable energy. In this paper, a field of experiments in actual conditions is conducted to investigate the influence of external parameters on the occupant's thermal comfort inside a typical dry region house. The obtained results are projected directly on the psychometric chart to position the real thermal comfort current situation. The results confirm the direct influence and indirect influence of external climatic conditions (temperature and humidity, respectively) on internal comfort. Two scenarios with renewable techniques are investigated experimentally based on the obtained results. An earth-to-air heat exchanger (EAHE) and solar chimney (SC) are connected separately to a similar building, and parameters affecting thermal comfort are discussed. The results show that both techniques improve thermal comfort inside the structure with efficiently saving energy. Renewable energy can enhance thermal comfort with significant power- and cost-saving in hot-dry regions.

Mitigation of heat strain by wearing a long-sleeve fan-attached jacket in a hot or humid environment.

ObjectivesThis study examined whether a fan‐attached jacket (FAJ) may mitigate the heat strain in hot or humid environment.MethodsNine healthy men engaged in 60‐min sessions on a bicycle ergometer (4 metabolic equivalents [METs] workload) in hot‐dry (40°C and 30% relative humidity) and warm‐humid (30°C and 85% relative humidity) environments. Both are equivalent to an approximately 29°C wet‐bulb globe temperature. The experiment was repeated—once wearing an ordinal jacket (control condition) and once wearing a long‐sleeve FAJ that transfers ambient air at a flow rate of 12 L/s (FAJ condition)—in both environments.ResultsIncreases in core temperatures in hot‐dry environment were not statistically different between control and FAJ; however, that in the warm‐humid environment were significantly different between control and FAJ (0.96 ± 0.10°C and 0.71 ± 0.11°C in rectal temperature, P < .0001; and 0.94 ± 0.09°C and 0.61 ± 0.09°C in esophageal temperature, P < .0001). Changes in heart rate were different between control and FAJ in both environments (62 ± 3 bpm and 47 ± 7 bpm, P < .0001 in hot‐dry environment; and 61 ± 3 bpm and 46 ± 5 bpm, P < .0001 in the warm‐humid environment) and decrease of %weight change was different in hot‐dry environment (1.59 ± 0.12% and 1.25 ± 0.05%, P = .0039), but not in the warm‐humid environment.ConclusionsWearing a FAJ may mitigate heat strain both in hot or humid environments.

Risk assessment of COVID infection by respiratory droplets from cough for various ventilation scenarios inside an elevator: An OpenFOAM-based computational fluid dynamics analysis.

Respiratory droplets—which may contain disease spreading virus—exhaled during speaking, coughing, or sneezing are one of the significant causes for the spread of the ongoing COVID-19 pandemic. The droplet dispersion depends on the surrounding air velocity, ambient temperature, and relative humidity. In a confined space like an elevator, the risk of transmission becomes higher when there is an infected person inside the elevator with other individuals. In this work, a numerical investigation is carried out in a three-dimensional domain resembling an elevator using OpenFoam. Three different modes of air ventilation, viz., quiescent, axial exhaust draft, and exhaust fan, have been considered to investigate the effect of ventilation on droplet transmission for two different climatic conditions (30 , 50% relative humidity and 10 , 90% relative humidity). The risk assessment is quantified using a risk factor based on the time-averaged droplet count present near the passenger's hand to head region (risky height zone). The risk factor drops from 40% in a quiescent scenario to 0% in an exhaust fan ventilation condition in a hot dry environment. In general, cold humid conditions are safer than hot dry conditions as the droplets settle down quickly below the risky height zone owing to their larger masses maintained by negligible evaporation. However, an exhaust fan renders the domain in a hot dry ambience completely safe (risk factor, 0%) in 5.5 s whereas it takes 7.48 s for a cold humid ambience.

The Applicability of Utci Index as a Substitute Index for the Assessment of Heat Stress in Hot-Humid and Hot-Dry Environments

The Applicability of Utci Index as a Substitute Index for the Assessment of Heat Stress in Hot-Humid and Hot-Dry Environments

Dietary supplementation of Solanum aethiopicum and Solanecio biafrae leaves alters stress and immune responses, antioxidant status, and meat quality in broilers raised in a hot-dry environment

ABSTRACT 1. This study investigated the influence of dietary supplementation of Solanum aethiopicum and Solanecio biafrae leaves, which have nutraceutical properties, on stress response, cytokine expression, antioxidant status, blood chemistry, abdominal fat and meat quality in broilers reared in a hot, dry environment. 2. One day old, Ross 308 chicks (n = 350) were randomly allotted to basal diets containing either no supplement (D1); 2.5 g/kg Solanum aethiopicum leaf (SAL; D2); 5 g/kg SAL (D3); 2.5 g/kg Solanecio biafrae leaf (SBL; D4); or 5 g/kg SBL (D5) for 42 d. Birds were reared at 34 ± 2°C and 40–50% relative humidity for 6 h/d from 22–42 d. Each dietary group was replicated in seven pens containing 10 chicks. 3. In the period 1–21 d, body weight gain, feed efficiency and feed intake were not influenced by diet. At 22–42 and 1–42 d, birds supplemented with SAL and SBL had higher (P < 0.05) body weight gain and feed efficiency than the D1 birds. Cloaca temperature, carcase cuts and relative organ weight did not differ between diets. The D3 birds had higher (P < 0.05) erythrocytes and haemoglobin compared with other birds. Dietary supplements reduced (P < 0.05) mortality, abdominal fat, serum total cholesterol, corticosterone, glucose and blood aspartate aminotransferase levels. 4. The treatments up-regulated (P < 0.05) splenic intelukin-10, and down-regulated (P < 0.05) tumour necrosis factor-α and interleukin-1β genes. A dose-dependent improvement (P < 0.05) in antioxidant enzyme activities and total antioxidant capacity of serum and breast muscle were found in the supplemented birds. The breast meat of the supplemented birds had lower (P < 0.05) carbonyl and malondialdehyde contents, and higher (P < 0.05) water holding capacity and redness compared with the non-supplemented meat. 5. These results illustrated that supplementation with either 5 g/kg SAL or 5 g/kg SBL attenuated the deleterious effects of heat stress in broiler chickens.

Influence of surrounding rock temperature on fracture parameters of concrete for shotcrete use in the hot-dry tunnel environments

The objective of this study was to explore the influence of the surrounding rock temperature on fracture parameters of concrete. Four different surrounding rock temperatures were adopted and the three-point bending test on notched beams was conducted in this paper. Based on this test, the fracture energy, initial fracture toughness, unstable fracture toughness, and crack extension resistance of concrete were calculated via the double-K fracture model the KR curve crack propagation criterion. The results are summarized as follows: (1) The fracture energy of concrete beams increased first then decreased with the increment of the hot-dry environment temperature, and reached the peak at 60 °C. (2) The initial fracture toughness, unstable fracture toughness, and crack extension resistance of concrete decreased with the increment of the hot-dry temperature. (3) The length of the fracture process zone increased first then decreased with the increment of the effective crack length.

Susceptibility of several cotton varieties to the cotton flea beetle, Podagrica puncticollis Weise (Coleoptera: Chrysomelidae), in a hot dry tropical environment of Ethiopia

Field trials were conducted to determine the reaction of cotton varieties to cotton flea beetle infestation. The experiment was laid out in a Randomized Complete Block Design with three replications comprising twelve cotton varieties. The results showed significant (P &lt; 0.01) differences among varieties in the populations of adult beetle they hosted and the injury they sustained at 15, 22, 29, 36 and 43 days after sowing (DAS). At 15 DAS, the highest numbers of adult beetle per plant (6.3), percent leaf area damaged (60.32 %) and number of shot-holes per attacked leaf (53.4) was recorded in Cucurova variety, whereas the lowest in Bulk-202 (2.05 beetles, 26.15% leaf area damaged and 23.16 shot-holes). The rate of incidence and damages decreased with the increase of the age of the cotton plants. Significant differences were also observed among cotton varieties in some agronomic characteristics i.e. in number of plants counted per plot at harvest and seed cotton yield in terms of kilogram per hectare. Seed cotton yield obtained from all cotton varieties varied from 602.36 to 1644.71 kilogram per hectare and the highest was obtained from Bulk-202, while the lowest from Local variety. Based on these findings, Cucurova, Local, Ionia and Acala SJ-2 varieties showed highly susceptible response, while Candia, Sille-91 and Deltapine-90 were moderately susceptible to cotton flea beetle. However, Bulk-202, Delcero and Claudia were relatively more tolerant varieties followed by CCRI-12 and Cuokra. These results will be important for the most proper management of cotton flea beetle.

Attentional processes and performance in hot humid or dry environments: review, applied recommendation and new research directions

Many important sporting events are organized in hot ambient conditions. In addition, given the global warming around the world, and because heat also concerns millions of people living in hot-dry and/or hot-humid environments, individuals often perform cognitive and/or cognitivo-motor tasks under heat stress conditions. Hot environment can negatively affect aerobic and high intensity performances and can also negatively influence mental performances and cognitive function as executive functions and attention. This review was realized in order to provide a better understanding of the influence of the heat on cognition as attentional processes. In addition, applied recommendations and strategies (e.g., acclimation, cooling, mental technics), that individuals can use during learning, training or competitions performed in hot environments, are discussed. Finally, new directions in research are proposed.

Host Range of Cotton Flea Beetle (Podagrica puncticollis) in a Hot Dry Tropical Environment of Ethiopia

Cotton flea beetle, Podagrica puncticollis is the most destructive insect pest of cotton in north-western part of Ethiopia. This study was conducted to identify and determine the host range of cotton flea beetle in Metema area. The field survey was undertaken from June 27, 2015 to January 9, 2016 in ten kebele administrations of the district. At least three fields were prospected after every 15 days, in each kebele for host plants as well as to determine population density and percent leaf damage by adult cotton flea beetle, at different growth stages of cotton plant. The composition of plant species with damaged symptom or infested by flea beetle was analysed using quantitative means and identified by comparing specimens with description of identification manuals. A total of 11 host plant species of cotton flea beetle were identified in the cotton growing areas of Metema throughout a season. Indigofera longibarbata (Fabaceae), Hibiscus articulatus, H. cannabinus, H. vitifolius, Abutilon figarianum, Sida alba and S. urens (Malvaceae), Bidens pilosa and B. setigera (Asteraceae), Corchorus olitorius and C. trilocularis (Tiliaceae) found to be common host plants of cotton flea beetle. Thus, among the host plants, H. vitifolius, H. cannabinus, H. articulatus, C. olitorius and C. trilocularis were the most suitable hosts for adult cotton flea beetle in respect of the number of adults per plant and percent foliage damage they sustained. These findings could aid in developing longterm management strategies for this important insect pest existing in a hot dry tropical environment of north-western Ethiopia.

Water quality and human health: A simple monitoring model of toxic cyanobacteria growth in highly variable Mediterranean hot dry environments

Due to population growth, urbanization and economic development, demand for freshwater in urban areas is increasing throughout Europe. At the same time, climate change, eutrophication and pollution are affecting the availability of water supplies. Sicily, a big island in southern Italy, suffers from an increasing drought and consequently water shortage. In the last decades, in Sicilian freshwater reservoirs several Microcystis aeruginosa and more recently Planktothrix rubescens blooms were reported.The aims of the study were: (1) identify and quantify the occurring species of cyanobacteria (CB), (2) identify which parameters, among those investigated in the waters, could favor their growth, (3) set up a model to identify reservoirs that need continuous monitoring due to the presences, current or prospected, of cyanobacterial blooms and of microcystins, relevant for environmental and, consequentially, for human health.Fifteen artificial reservoirs among the large set of Sicilian artificial water bodies were selected and examined for physicochemical and microbiological characterization. Additional parameters were assessed, including the presence, identification and count of the cyanobacterial occurring species, the measurement of microcystins (MCs) levels and the search for the genes responsible for the toxins production. Principal Component Analysis (PCA) was used to relate environmental condition to cyanobacterial growth.Water quality was poor for very few parameters, suggesting common anthropic pressures, and PCA highlighted clusters of reservoirs vulnerable to hydrological conditions, related to semi-arid Mediterranean climate and to the use of the reservoir. In summer, bloom was detected in only one reservoir and different species was highlighted among the Cyanobacteria community. The only toxins detected were microcystins, although always well below the WHO reference value for drinking waters (1.0 μg/L). However, molecular analysis could not show the presence of potential cyanotoxins producers since a few numbers of cells among total could be sufficient to produce these low MCs levels but not enough high to be proved by the traditional molecular method applied. A simple environmental risk-based model, which accounts for the high variability of both cyanobacteria growth and cyanotoxins producing, is proposed as a cost-effective tool to evaluate the need for monitoring activities in reservoirs aimed to guarantee supplying waters safety.