Heat stress is a well documented hazard across industries. The combination of environmental conditions, work demands, and clothing contribute to heat strain. Left unchecked, heat strain causes changes in an individual's physiological state that can lead to serious and fatal conditions with little warning. Although engineering and administrative controls are the first choice to abate this hazard, they frequently are not feasible. In these cases, personal cooling is often employed. There are three main types of personal cooling: liquid, air, and passive. Each has its own advantages and disadvantages. This study focuses on continuous cooling using a portable liquid cooling system (LCS). The LCS used a vest with tubes circulating water from an ice heat sink. The experiment consisted of five males each completing seven tests in random order. The subjects wore work clothes as the control then in conjunction with a firefighter, vapor barrier, and bomb suits. Each suit was tested with and without the benefit of the LCS. All of the tests took place at 35oC dry bulb and 50% relative humidity while attempting to walk 90 minutes on a treadmill at a 300 W metabolic rate. The study found continuous use of the LCS significantly reduced heat storage (S) and the rate of rise of heart rate (rrHR), core temperature (rrTre), and mean skin temperature (rrTsk) for the firefighter and vapor barrier suits as compared to no-cooling. Although the LCS didn't significantly affect the rate of rise for physiological responses with the bomb suit, it did however, significantly increase the endurance time. Interestingly, the study also found when wearing either the vapor barrier or firefighter suits in conjunction with the LCS that the rrHR and rrTre were not significantly different from only wearing work clothes.

Heat stress is one of many physical agents to which thousands of workers are under constant exposure. Oftentimes it is necessary to work above the WBGT-based heat stress exposure limits. It is therefore important to consider alternative measures that include an exposure time limit to manage the heat stress. Predicted Heat Strain (PHS) (ISO7933) is one of those alternatives. PHS uses both personal factors like height and weight and job factors of environment, metabolic rate and clothing. The purpose of this project is to determine whether the PHS is an adequate method to predict short term exposure limits. The project’s data were taken from a prior experimental study where twelve participants were exposed to five different heat stress levels while over three different clothing ensembles. A total of 15 combinations of clothing and environment were tried. The PHS process was adapted to an Excel function using Visual Basic for Applications (VBA) (called fPHSTre). fPHSTre predicted a rectal temperature (Tre) at the exposure limit using both personal and job factors and then using standard values for personal factors. Based on analysis of variance, the fPHSTre adequately accounted for clothing, specifically evaporative resistance, using either fixed or individual data for predicted Tre on the experimental trials. In general, the PHS model could be used to reliably assess time limiting safe exposures in occupational settings for workers in hot environments.

Workers are exposed to stressful thermal work environments in multiple industries every day. Methods for assessing heat stress often struggle to balance productivity without compromising the health of the workers. The Thermal Work Limit (TWL) is a method that has been adopted in areas outside of the United States as a viable method for heat assessment that combines health with productivity. TWL recommends a maximum metabolic rate for a given set of environmental conditions, clothing ensemble and acclimatization state. The purpose of this paper was to evaluate the validity of the TWL against a set of heat stress data known to be at the maximum sustainable level. A range of conditions were combined through environmental (20%, 50% and 70% relative humidity), clothing (woven clothing, WC; particle barrier coveralls, PB; water barrier coveralls, WB; and vapor barrier coveralls, VB), and workload factors (metabolic rates at low, L; moderate, M; and high, H) at the transition from sustainable to unsustainable exposure to ensure that the TWL method is thoroughly explored. Data from previous heat stress studies were used to compare the difference in predicted TWL with a calculated value. An analysis of variance (ANOVA) demonstrated that there were significant effects of the TWL due to clothing, metabolic rate level and relative humidity level. TWL provided similar results for WC, PB and WB, but had systematically lower values for VB. This suggested a more protective recommendation with high evaporative resistance. As the metabolic rate increased, the recommended limiting TWL also went up out of proportion to the metabolic rate, which provided greater protection at increasing metabolic rates. Under drier conditions (20% relative humidity), the TWL was systematically lower than for 50% and 70% relative humidity. While there were significant differences due to the main effects, the TWL was designed to be used without defined limits on environmental conditions, metabolic rate or clothing. Therefore, all of the conditions represented a comprehensive test of the TWL. Overall, the TWL was less protective than the current methods used by ACGIH Threshold Limit Values (TLV) and National Institute for Occupational Safety and Health (NIOSH) Recommended Exposure Limit (REL). At the threshold, the TWL had a 7% probability of being unsustainable compared to the threshold probability of 1% for the TLV and REL.

Broiler breeders experience a natural decline in fertility levels as a flock ages. A male management practice such as double interspiking could be applied to counteract this decline. Our objective was to investigate the effects of double interspiking on flock fertility, testosterone concentrations, stress responses, and behavioral responses of broiler breeders in heat stressed environments. Two hundred and eighty-eight broiler breeder pullets and thirty-six broiler breeder roosters (Ross 708) were assigned to three groups at 21 weeks of age (WOA). All three groups were housed in slatted floor pens in which room temperature cycled from 23.8 to 30 C to mimic heat stressed environments. Double interspiking was carried out between two pens at 42 and 52 WOA. Beginning at 32 WOA, eggs were set every two weeks, candled at day 12, and percent fertility calculated. Concentrations of the hormones testosterone and corticosterone (CS) were measured by radioimmunoassays at specific time points in the experiment. Lymphocytes and heterophils were counted in order to calculate heterophil:lymphocyte (H:L) ratios. Behavior was monitored with Panasonic video cameras which recorded video footage using the Noldus MPEG Recorder from 1900 hr to 2100 hr at specific time points. Recordings were analyzed, and frequency of specific behavioral responses of individual (preening, feather ruffling, wing flapping), male-to-male (fighting, pecking, retreating), and male-to-female (attempted and completed mating) behaviors were assessed. The introduction of unfamiliar roosters resulted in a fertility increase (P<0.01) between control and spiked birds after the first interspike and a sustainment of fertility levels after the second interspike. Testosterone concentrations declined (P<0.0001) from 1.95ng/mL to 0.11ng/mL as the birds aged. Corticosterone concentrations differed among bird groups and was elevated (P=.0333) for both groups that were interspiked. H:L ratios were also different among bird groups with all birds housed in the interspiked rooms showing higher ratios. Double interspiking increased the occurrence of male-to-male interactions, but there were no significant differences in male-to-female or individual behaviors. Regardless of treatment, there was a decrease in male-to-female behaviors as the birds aged. Double interspiking does show promise as a tool to increase fertility levels in a broiler breeder flock.

This thesis examined why NCAA Division 1 American football “linemen” experience greater heat strain than “backs” during summer training camps. In study #1, exercise at a heat production of 350 W/m2 in a hot environment (Tdb:32.4±1.0ºC; Twb:26.3±0.6ºC) resulted in greater local sweating on the upper body (head, arm, shoulder and chest; all <0.05) and a greater core temperature (P=0.033) in linemen despite a ~25% lower heat production per unit mass (L:6.0±0.5 W/kg; B:8.2±0.8 W/kg). In study #2, greater convective and evaporative heat transfer coefficients (P<0.05) were found in backs during live summer training camp drills, but these did not lead to a greater dry heat transfer or evaporative capacity. However, the maximum metabolic rate per unit mass was lower in linemen due to differences surface area-to-mass ratio. In conclusion, the greater heat strain previously reported in linemen likely arises, in part, from differences in sweating efficiency and body morphology.

This thesis examined why NCAA Division 1 American football “linemen” experience greater heat strain than “backs” during summer training camps. In study #1, exercise at a heat production of 350 W/m2 in a hot environment (Tdb:32.4±1.0ºC; Twb:26.3±0.6ºC) resulted in greater local sweating on the upper body (head, arm, shoulder and chest; all <0.05) and a greater core temperature (P=0.033) in linemen despite a ~25% lower heat production per unit mass (L:6.0±0.5 W/kg; B:8.2±0.8 W/kg). In study #2, greater convective and evaporative heat transfer coefficients (P<0.05) were found in backs during live summer training camp drills, but these did not lead to a greater dry heat transfer or evaporative capacity. However, the maximum metabolic rate per unit mass was lower in linemen due to differences surface area-to-mass ratio. In conclusion, the greater heat strain previously reported in linemen likely arises, in part, from differences in sweating efficiency and body morphology.

Seasonally high nighttime temperatures (HNT) along the United States Gulf Coast and in regions of similar climate, during the critical stages of development, could reduce rice yield and quality. To study the effects of HNT on plant physiology, a method for applying a controlled heating treatment to plant canopies was developed using overhead infrared heaters, which are relatively inexpensive and are accurate, precise and reliable in rapidly controlling the temperature. The apparatus successfully maintained air temperatures within the set points plus/minus 0.5 degrees C, and was used for all the experiments. Several experiments were conducted to determine the response of various physiological parameters during and following exposure of rice plants to HNT (32 degrees C) or ambient nighttime temperature (ANT) (27 degrees C) starting from 2000 h until 0600 h, and with or without plant growth regulator treatments. The plant growth regulator treatments included alpha-tocopherol (vitamin E), glycine betaine (GB), and salicylic acid (SA), which play different roles in inducing thermo-tolerance in plants. High nighttime temperature had no effect on plant height, number of tillers and panicles, or rice net leaf photosynthetic rates. However, HNT increased leaf respiration (dark respiration in the night) (21%) and decreased membrane thermo-stability (60%), pollen germination (20%), spikelet fertility (18% as a % of total spikelets), grain length (2%), and grain width (2%). The HNT also hastened plant development. The combinations of these effects decreased rice yield by 90%. Moreover, under HNT, there were decreases in leaf chlorophyll concentration (7%) and nitrogen concentration (18%). Application of GB and SA increased total antioxidant capacity of the rice plants by 17%, thereby decreasing the leaf respiration rates, increasing membrane thermo-stability, pollen germination, and spikelet fertility, thus increasing the yield. High nighttime temperature decreased leaf starch concentration (14%), grain total nonstructural carbohydrate (TNC) concentration (9%), and grain extractable invertase activity (20%). Vitamin E- or GB-treated plants had greater grain soluble-sugar concentrations, whereas SA-treated plants had greater leaf soluble-sugar concentrations and lower grain TNC concentrations. Invertase activity was shown to be not rate limiting or required for sucrose degradation for starch synthesis in grain of 'Cocodrie' rice under short-term high nighttime temperatures exposures during grain filling. In conclusion, HNT decreased rice yield by increasing plant respiration, rate of crop development, and decreasing membrane thermo-stability, pollen germination, spikelet fertility and grain dimensions. Exogenous application of GB and SA increased yields under HNT, possibly acting through increased antioxidant levels, which might have protected the membranes and enzymes against heat-induced ROS-mediated degradation.

The aim of this study was to identify QTLs associated with the maintenance of grain quality following post-anthesis heat stress. A population of 64 F6Halberd X Cutter recombinant inbred lines (RILs) was exposed to either heat stress or control conditions in the greenhouse, starting ten days after anthesis. Grain quality was determined using the sodium dodecyl sulfate (SDS) sedimentation test, a significant predictor of bread baking quality. The percent change in SDS sedimentation test scores between the heat and control populations was used to identify QTLs associated with quality stability. Four QTLs were identified, located one each on chromosomes 1B, 1D, 4A, and 7A. Three of the QTLs, those on 1B, 1D, and 4A, were associated with variations in SDS sedimentation level. The QTL on chromosome 7A was associated with the percent change in SDS sedimentation scores between heat-stressed and control conditions. This indicated a relationship between the identified QTL and quality stability. To confirm the detected QTLs, eighty advanced lines grown at three Texas nurseries were genotyped and tested for relationships between QTL-associated markers, quality traits, and stability of the quality traits. Quality trait stability was estimated using the coefficient of variability (CV%) of quality traits between growing sites. Quality characters analyzed in the advanced lines included kernel hardness, mixograph peak time, kernel weight, flour yield, SDS sedimentation, and grain yield. The analysis showed support for the effect of the QTLs on chromosomes 1B, 1D, and 4A. Further analysis will be needed to confirm the QTL on 7A, in particular. The mapping of additional markers will be necessary. However, the potential importance of this QTL and the abundance of other QTLs detected in this region make it worth investigating.

Heat stress adversely affects wheat production in many regions of the world and is particularly detrimental during reproductive development. The objective of this study was to identify quantitative trait loci (QTL) associated with improved heat tolerance in hexaploid bread wheat (Triticum aestivum). To accomplish this objective, an analysis of both the phenotypic and genetic responses of two recombinant inbred line (RIL) populations was conducted. RIL populations Halberd x Cutter and Halberd x Karl 92 (H/K) both derive heat tolerance from Halberd and segregate in their response to heat stress. A heat susceptibility index (HSI) was calculated from the reduction of three yield components; kernel number, kernel weight, and single kernel weight, following a three-day 38 degrees C heat stress treatment during early grain-filling. The HSI, as well as temperature depression of the main spike and flag leaf were used as measurements of heat tolerance. Genetic linkage maps were constructed for both populations and were used in combination with phenotypic data and statistical software to detect QTL for heat tolerance. In a comparison across the two across populations, seven common QTL regions were identified for HSI, located on chromosomes 1B, 3B, 4A, 5A, 5B, and 6D. Subsequent analysis of temperature depression in the H/K population identified seven QTL that co-localized for both cooler organ temperature and improved HSI. Four of the beneficial alleles at these loci were contributed Halberd. The genetic effect of combining QTL, including QHkw.tam-1B, QHkwm.tam-5A.1, and QHskm.tam-6D showed the potential benefit of selection for multiple heat tolerant alleles simultaneously. Analysis of the H/K population in the field under abiotic stress detected QTL on chromosome 3B and 5A, which were in agreement with results from the greenhouse study. The locus QYld.tam-3B was pleiotropic for both temperature depression and HSI in both experiments and was associated with higher biomass and yield under field conditions. The results presented here represent a comprehensive analysis of both the phenotypic response of wheat to high temperature stress and the genetic loci associated with improved heat tolerance and will be valuable for future understanding and improvement of heat stress tolerance in wheat.

Rhodobacter capsulatus DSM1710 is a purple non-sulfur bacterium capable of hydrogen production via photofermentation. Biohydrogen is a clean and renewable way of hydrogen production, which can be achieved by PNS bacteria in outdoor large scale photobioreactors using sun light. In outdoor conditions bacteria can be exposed to heat and cold stress. In this study in order to understand the effects of heat and cold stress on photofermentative hydrogen production and gene expression profile of R.capsulatus on acetate as the carbon source, microarray analysis was carried out. Since there is no commercially available microarray chip for R.capsulatus, an Affymetrix GeneChip&reg / was designed and it was manufactured by Affymetrix.The experiments were conducted at 30