Negative Effects Of Heat Research Articles

Higher performance carbon fiber reinforced thermoplastic composites from thermoplastic prepreg technique: Heat and moisture effect

In this study, higher performance unidirectional carbon fiber reinforced polyamide-6 composites were manufactured from prepreg by using hot compression methods with assistance of spread tow technology. UD CF/PA6 laminates with uniform fiber distribution and in good impregnation are achieved. Various mechanical properties of UD CF/PA6 laminates were evaluated by using tensile tests and three-point tests. The effects of heat and moisture on the flexural properties of UD CF/PA6 laminates were carried out through hot air exposure and hot water immersion process at different temperature for different time, respectively. The corresponding effects on the neat resin were also investigated to verify the role of matrix degradation by three-point bending tests and fourier transform infrared spectroscopy analysis. The optical microscopy and scanning electron microscopy observation were carried out to investigate the fracture behaviors and explain the fracture mechanism. Results indicated that no obvious negative effect of heat (<98°C) on the flexural properties of UD CF/PA6 laminates in one month. But serious negative effect of mixture action of heat and moisture on laminates has been verified owing to their matrix and interfacial bonding capability degradation after hot water immersion, which also led to the change of failure behavior.

Efficacy of starter culture application using immersion technique on the characteristics of cooked-curd cheeses: Kashar cheese sample

Kashar is a cooked-curd cheese and traditionally produced without using any starter cultures. Three different types of commercial starter cultures Choozit ™ MA 11 (MA), BT 01 (BT) and Feta A (Feta) applied to the Kashar cheeses after the cooking stage using an immersion technique to eliminate the negative effect of heat on the viability of starter cultures and their activities. Compositional, sensory and ripening characteristics including electrophoresis were determined. MA-culture showed the highest acid production capability while BT-culture possessed the highest proteolytic activity and sensory scores. The results suggest that the immersion technique has a potential use in the production of cooked-curd cheeses.

Thermodynamic Properties of Alloys of the Sn–Yb System

Thermochemical properties of liquid alloys of the Sn–Yb system are studied via calorimetry at 1110–1310 K over the ranges of concentrations 0 < x < 0.47 and 0.82 < x < 1. Considerable negative heat effects of the mixing of these alloys are identified. Activities of the components, the Gibbs energies and entropies of mixing, and the liquidus curve of the phase diagram of this system are calculated using the ideal associated solution (IAS) model and agree with data from the literature.

Thermodynamic properties of alloys of the binary Sb–Yb system

The thermochemical properties of melts of the binary In–Yb system were studied by the calorimetry method at 1160–1380 K over the whole concentration interval. It was shown that significant negative heat effects of mixing are characteristic features for these melts. Using the ideal associated solution (IAS) model, the activities of components, Gibbs energies and the entropies of mixing in the alloys, and the phase diagram of this system were calculated. They agree with the data from literature.

Temperature induced changes in wheat (Triticum aestivum) growth and yield under salt affected environment of Indo-Gangetic Plains

ABSTRACTAn attempt has been made in the field conditions to evaluate the effect of atmospheric temperature rise on yield, ionic ratio (Na:K), and accumulation of antioxidative pigments in wheat in different growth stages under different soils. Five planting windows (PW) were classified, based on date of wheat sowing where the average temperature difference between a particular PW and PW-I varied from 1.33–4.24°C. Plant leaf area and root length density showed decreasing trend with increasing temperature. A low flag leaf water potential (−1.14 MPa) in sodic soil and high solute potential (−1.34 MPa) in saline-sodic soil was observed under PW-V, where high temperature difference (4.24°C) was recorded. The Na:K ratio was found to be highest in both straw and grain which were 1.802 and 1.126%, respectively, under saline-sodic conditions in PW-V. Proline and malondialdehyde concentration was highest under sodic conditions which varied between 2.82–2.95 mg g−1 fresh weight (FW) and 18.38–30.18 nmol g−1 FW, respectively, under maximum temperature difference. An increase in temperature (>1°C) significantly reduced grain yield (>10%) that was negatively correlated with Na+ (r = −0.78) but positively with K+ (r = +0.62) concentrations under saline-sodic conditions, however under sodic conditions, it was positively correlated with K+ (r = +0.63) concentration. Therefore, looking in to the climate change scenario, shifting planting window of wheat sowing may be helpful in mitigating the negative effects of heat and salt stress on wheat crop.

Multiple Sclerosis Functional Composite as a Measure of the Effects of Heat in Multiple Sclerosis

Background: Heat sensitivity is a common feature of multiple sclerosis (MS), and heat has been found to impair MS patients’ physical and cognitive functioning. There is, however, no simple and specific measurement tool to evaluate the possible effects of heat on these functions. Objectives: The aim of this study was to evaluate the compatibility of the multiple sclerosis functional composite (MSFC) to demonstrate the effects of heat on functioning in patients with MS. Patients and Methods: A total of 22 heat-sensitive MS patients and 19 healthy controls (HCs) were considered for the analysis. Moderate heat exposure took place in a Finnish sauna. Functioning was measured with the MSFC, which consists of two physical (the Nine Hole Peg test and the 25-foot timed walk test) and one cognitive (the PASAT-3) measure, before, during and one hour after the heat exposure. Results: In the MS group the average MSFC scores were -0.48 (SD 0.79) at baseline, -0.99 (SD 1.97) during heat exposure and -0.68 (SD 1.58) after a one-hour delay. The average MSFC scores of the HC group were 0.58 (SD 0.42) at baseline, 0.66 (SD 0.43) during heat exposure and 0.68 (SD 0.41) after a one-hour delay. The MS group had significantly lower MSFC scores than the HC group (P = 0.01). The MS patients’ score deteriorated during the heat exposure, whereas that of the controls did not (P = 0.00). Conclusions: The results suggest that the MSFC could be used as a simple tool to detect the negative effects of heat in patients with MS.

Effect of heat stress and oil formulation on conidial germination of Metarhizium anisopliae s.s. on tick cuticle and artificial medium

The effect of heat stress (45°C) versus non-heat stress (27°C) on germination of Metarhizium anisopliae sensu stricto (s.s.) isolate IP 119 was examined with conidia formulated (suspended) in pure mineral oil or in water (Tween 80, 0.01%), and then applied onto the cuticle of Rhipicephalus sanguineus sensu lato (s.l.) engorged females or onto culture medium (PDAY). In addition, bioassays were performed to investigate the effect of conidia heated while formulated in oil, then applied to blood-engorged adult R. sanguineus females. Conidia suspended in water then exposed to 45°C, in comparison to conidia formulated in mineral oil and exposed to the same temperature, germinated less and more slowly when incubated on either PDAY medium or tick cuticle. Also, conidial germination on tick cuticle was delayed in comparison to germination on artificial culture medium; for example, germination was 13% on tick cuticle 72h after inoculation, in contrast to 61.5% on PDAY medium. Unheated (27°C) conidia suspended in either water or oil and applied to tick cuticle developed appressoria 36h after treatment; whereas only heat-stressed conidia formulated in oil developed appressoria on tick cuticle. In comparison to conidia heated in mineral oil, there was a strong negative effect of heat on germination of conidia heated in water before being applied to arthropod cuticle. Nevertheless, bioassays [based primarily on egg production (quantity) and egg hatchability] exhibited high percentages of tick control regardless of the type of conidial suspension; i.e., water- or oil-formulated conidia, and whether or not conidia were previously exposed to heat. In comparison to aqueous conidial preparations, however, conidia formulated in oil reduced egg hatchability irrespective of heat or no-heat exposure. In conclusion, mineral-oil formulation protected conidia against heat-induced delay of both germination and appressorium production when applied to the cuticle of R. sanguineus.

Influência do sistema silvipastoril na puberdade de novilhas

As a result of current concern with the depletion of natural resources, combined with a larger quest for better reproductive rates, the Brazilian cattle industry has been taking measures giving priority to sexual precocity of his flock. In Brazil, a tropical country, which has a production system basically livestock grazing, heat stress factor is becoming a limiting factor in the sustainability of cattle breeding. High temperatures can negatively influence the main reproductive characteristic indicator of sexual precocity in cattle is age puberty. This negative effect of heat (stress) implies physiological adjustments in the animal in search of maintaining homeothermy, among them are alterations in blood flow, behavior, food intake and hormonal factors influencing the onset of puberty. Livestock keepers, high precocity increase production anticipates the recovery of investments, increase the productive life of animals allowing for greater profitability. In search of sustainability and competitiveness of dairy farming, the research has been pointing the silvopastoral systems involving the cultivation of woody perennials, grasses and animals as a good option. This is explained by the formation of a thermally comfortable microclimate, mitigating the harmful effects of heat stress on reproduction, besides improving the soil and pasture.

Modulation of NF-κB and Nrf2 pathways by lycopene supplementation in heat-stressed poultry

Heat stress is characterised by reduced antioxidant status, and is one of the physiological alterations in response to exposure to higher temperatures in birds, which results in increased oxidative stress and immune suppression. The transcription entity nuclear factor-kappa light chain enhancer of B cells (NF-κB) controls the expression of genes involved in a number of physiological responses, including immune inflammatory responses, acute-phase inflammatory responses, oxidative stress responses, cell adhesion, differentiation, and apoptosis. The nuclear factor-2 erythroid related factor-2 (Nrf2), the redox-sensitive transcription factor, plays a key role in regulating induction of phase II detoxifying or antioxidant enzymes. Thus, activation of Nrf2 is considered to be an important molecular target of many anti-stressor agents. However, during heat stress conditions this regulation is disturbed offering an opportunity for therapeutic intervention. Heat stress is a condition in which the expression pattern of NF-κB and Nrf2 changes. To reduce the negative effects of heat, antioxidants are used in poultry diets for their anti-stress effects, associated with improved nutrient utilisation. For instance, lycopene, a powerful antioxidant, is particularly important because of its ability to quench reactive oxygen. This review focuses on the role of the NF-κB and Nrf2 in heat stress condition and summarises the therapeutic outcomes of lycopene in feed, targeted at the NF-κB and Nrf2 pathways in heat-stressed poultry.

Thermodynamic properties of alloys of the Co-Sc and Co-Y systems

The thermochemical properties of melts of the Co-Sc(Y) systems were studied by the calorimetry method at 1873 K over the wide concentration intervals. It was shown that moderate negative heat effects of mixing are characteristic for these melts. Using the ideal associated solution (IAS) model, the activities of components, mixing Gibbs energies and entropies in the alloys of these systems, and their phase diagrams were calculated, and they agree well with the data from literature and undergo the general dependences for the Fe(Co, Ni, Cu)-d-metal systems.

The impact of evaporative cooling on the thermoregulation and sensible heat loss of sows during farrowing

Pigs are more sensitive to high environmental temperatures explained by the inability of sweating and panting properly when compared to other species of farmed livestock. The evaporative cooling system might favor the thermal comfort of animals during exposure to extreme environmental heat and reduce the harmful effects of heat stress. The purpose of this study was to assess the sensible heat loss and thermoregulation parameters from lactating sows during summer submitted to two different acclimatization systems: natural and evaporative cooling. The experiment was carried out in a commercial farm with 72 lactating sows. The ambient variables (temperature, relative humidity and air velocity) and sows physiological parameters (rectal temperature, surface temperature and respiratory rate) were monitored and then the sensible heat loss at 21days lactation was calculated. The results of rectal temperature did not differ between treatments. However, the evaporative cooling led to a significant reduction in surface temperature and respiratory rate and a significant increase in the sow's sensible heat loss. It was concluded that the use of evaporative cooling system was essential to increase sensible heat loss; thus, it should reduce the negative effects of heat on the sows' thermoregulation during summer.

Featherless and feathered broilers under control versus hot conditions. 1. Breast meat yield and quality

The improved genetic potential of contemporary commercial broilers cannot be fully expressed under hot conditions that depress growth rate, decrease breast meat yield, and reduce meat quality. The negative heat effects are attributed to the insulating feather coverage, which, under high ambient temperatures (AT), hinders dissipation of the excessive internally produced heat. Accordingly, featherless broilers (sc/sc), their feathered sibs (+/sc), and contemporary broilers (+/+) were subjected to control AT (26°C) and hot AT (32°C) to test the hypothesis that lack of feathers contributes to higher breast muscle yield and better meat quality, especially under hot conditions, and that differences related to lack of feathers are related to cardiovascular capacity. In 2 similar trials, the superior genetic background of the contemporary broilers was manifested under control conditions; their mean BW was about 15% higher than the means of the featherless broilers and their feathered sibs. The hot conditions depressed BW of the 2 feathered groups by approximately 25%, with hardly any effect on featherless broiler BW. Breast meat yield (% of BW) in the featherless broilers was higher than in those with feathers, especially under the hot AT. Furthermore, the featherless broilers were characterized by superior meat quality as indicated by lower drip loss, lower lightness, and higher redness. The superior meat quality of the featherless broilers could be explained by their larger hearts and higher hematocrit values, suggesting superior cardiovascular capacity to supply oxygen and nutrients to the breast muscles. On the practical side, the results clearly indicate that modern featherless broilers can reach normal BW, as well as yield and quality of breast meat, under hot conditions as well. It appears that broiler meat production in hot regions and climates can be substantially improved by introducing the featherless gene into contemporary commercial broiler stocks. This has become more feasible since the recent development of a simple DNA test to identify carriers of the recessive sc mutation.

Approach to assess a fast welding simulation in an industrial environment — Application for an automotive welded part

Fusion welding processes are widely used for joining metal structures, such as pipes, ships, and cars. In general, these joining processes offer a very good compromise between reliability, safety, cost and maintenance which are important issues in the current economical context. The negative heat effects of welding, i.e. distortions and residual stresses of the welded parts, are well known and many researches in this field have already been done in the last decades in order to minimize them. On the experimental side, many sophisticated procedures have become state of the art to deal with this problem. On the computational side, the improvement of the simulation algorithms and the computing power enables the simulations of many physical phenomena occurring during the welding process. The implementation of welding simulation techniques is nevertheless not an easy task and often associated with expert knowledge which hinders their global application in an industrial environment. This paper is focused on the industrial requirements of a welding simulation software with special respect to the needs of the automotive industry. The necessary information to run a welding simulation and the expectations of a weld specialist without deep knowledge in numerical methods are investigated. These expectations are tested on an automotive welded assembly with a commercially available welding simulation software designed especially for the needs of the automotive industry. A welding experiment is done and the measured temperature distributions and distortions serve as reference to validate the simulation results. The result quality of the simulations of temperature fields and distortions is in best agreement with experimental data. The workflow is well adapted for the considered industrial requirements and the time-tosolution as well as the computational costs are acceptable, whereas the efficient calibration of the heat input model is still a point which will be further investigated in current and future research works.

Case Study for Welding Simulation in the Automotive Industry

Welding is one of the most widely used joining processes in structural applications, like in car body production in the automotive industry. It is well-known that distortions and residual stresses occur during and after the welding process. Many procedures exist to decrease these negative heat effects of welding, but are often coupled with highly cost intensive experiments. For several decades, simulation models have been developed to understand and predict the heat effects of welding and to reduce experimental effort. In the production planning of various Original Equipment Manufacturers (OEM), some simulation tools are already well established, e. g. for crash test, forming or casting simulations. For welding, the demand is high but the implementation of welding simulation software is still not yet established. Welding is a complex process and the development of a flexible simulation tool, which produces good simulation results without expert knowledge in simulation, is not an easy task. In this paper, a welded assembly from the automotive industry has been simulated and compared to experimental data. Temperature fields and transient distortion distributions have been measured with thermocouples and with an optical 3D deformations analysis tool, respectively. The simulation has been run with a commercially available welding simulation software. The simulated temperature fields match the numerical ones perfectly. The simulated distortions are also qualitatively in best agreement with the experimental ones. Quantitatively, a difference of approximately 20 % between the simulated and the measured distortions is visible; this is acceptable considering the simplifications and assumptions of the simulation model. The global time to solution to get these results without expert knowledge in welding simulation was between 4 and 6 weeks, which is a reasonable time frame for an industrial application of welding simulation.

High hydrostatic pressure treatment of beer and wine: A review

Abstract High hydrostatic pressure (HHP) technology has become a reality in the food industry. Commercial use of HHP has been accepted in many countries and it is possible to find and buy products treated by HHP such as meat products, sea foods and fruit juices. Nevertheless, no HHP-treated beer and wine are introduced in the market throughout the world although rice wine is one of the earliest HHP-treated commercial products that appeared on the Japanese market. This contribution compiles the studies about HHP on beer and wine: in addition to microbial destruction, it has been reported that HHP improves some organoleptic properties of beer and wine without detrimental effects on important quality characteristics, such as color, pH and turbidity. Although more studies should be carried out on the sensory properties and consumer attitudes to HHP-treated beer and wine, HHP could be an alternative to the existing stabilization methods used in beer and wine industries. Industrial Relevance Studies have shown that HHP treatment not only inactivates the undesirable microorganisms but also improves the organoleptic properties of beer and wine. The pressure levels used to treat beer and wine were similar to the commercial applications used in fruit juice industry i.e., 400-600 MPa. Therefore, HHP has a huge potential to eliminate the negative effect of heat on the aroma and flavor beer and also to reduce the SO2 levels used in wine.

Heat stress effects around flowering on kernel set of temperate and tropical maize hybrids

Final kernel number in the uppermost ear of temperate maize ( Zea mays L.) hybrids is smaller than the potential represented by the number of florets differentiated in this ear, and than the number of silks exposed from it (i.e., kernel set <1). This trend increases when stressful conditions affect plant growth immediately before (GS 1) or during (GS 2) silking, but the magnitude of change has not been documented for heat stress effects and hybrids of tropical background. In this work we evaluated mentioned traits in field experiments (Exp 1 and Exp 2), including (i) two temperature regimes, control and heated during daytime hours (ca. 33–40 °C at ear level), (ii) two 15-d periods during GS 1 and GS 2, and (iii) three hybrids (Te: temperate; Tr: tropical; TeTr: Te × Tr). We also measured crop anthesis and silking dynamics, silk exposure of individual plants, and the anthesis–silking interval (ASI). Three sources of kernel loss were identified: decreased floret differentiation, pollination failure, and kernel abortion. Heating affected all surveyed traits, but negative effects on flowering dynamics were larger (i) for anthesis than for silking with the concomitant decrease in ASI, and (ii) for GS 1 than for GS 2. Heat also caused a decrease in the number of (i) florets only when performed during GS 1 (−15.5% in Exp 1 and −9.1% in Exp 2), and only among Te and TeTr hybrids, (ii) exposed silks of all GS × Hybrid combinations, and (iii) harvestable kernels (mean of −51.8% in GS 1 and −74.5% in GS 2). Kernel abortion explained 95% of the variation in final kernel numbers ( P < 0.001), and negative heat effects were larger on this loss (38.6%) than on other losses (≤11.3%). The tropical genetic background conferred an enhanced capacity for enduring most negative effects of heating.

Air-conditioned deployable force infrastructure as a strategy to combat sleep deprivation among troops in hot countries

High-tech peacekeeping and humanitarian interventions form an increasing part of the range of duties of the military, dispatching troops to all parts of the world, with emphasis on hot climate areas. These missions call for fewer soldiers but with a more thorough, detailed and timely awareness level to reach predetermined goals. High ambient temperatures in the operational environment have a deleterious effect on performance, which is aggravated by poor sleep. Current deployable force infrastructure is often unable to support the restoration of body and brain sufficiently, while troop fitness is essential to the success of the mission. Supplying the peacekeepers with air-conditioned housing is becoming an increasingly important non-pharmacological strategy to counter the negative effects of heat. This paper investigates the influence of the military field environment, and high temperatures in particular, on sleep, comfort and performance of personnel and equipment, and looks at the benefits of installing air-conditioning systems and future trends in deployable force infrastructure. Practical application: Results of this study can be used for innovations in designing comfortable mission housing and accompanying building services that do not only offer comfort to military personnel in field settings, but also provide better conditions for sleep. Improved comfort and sleep can in turn benefit operational performance. The results can also be used for a large range of civilian purposes, for instance, the creation of comfortable bedrooms and hotel rooms.

Response surfaces for the combined effects of heat shock and smoke on germination of 16 species forming soil seed banks in south‐east Australia

Abstract There is limited understanding of how fire‐related cues such as heat shock and smoke can combine to affect the germination response of seeds from fire‐prone vegetation because combinations of multiple levels of both cues have rarely been investigated. Germination response surfaces were determined for the combination of heat shock and smoke by applying factorial combinations of temperature (up to 100°C) and aerosol smoke (0–20 min) to 16 species that form soil seed banks in the Sydney region of south‐eastern Australia. Duplicate populations of three species were also examined to assess the constancy of a species response surface. Of the 19 populations examined, 16 showed a germination response to both the fire cues, which combined interactively in 14 populations, and independently in two. No population responded only to a single cue; however, seeds of 11 populations responded to heat in the absence of smoke, and nine responded to smoke in the absence of heat. Heat applied in the absence of smoke negatively affected germination in seven populations, either progressively as temperature increased, or above a set temperature. Negative germination responses over part of the temperature range were fully reversed at higher temperatures for unsmoked seeds of four populations (curvilinear heat response). Smoke effects were most frequently positive over all or part of the range of durations used, and when combined with heat frequently fully or partially reversed negative heat effects. Three populations required the obligatory combination of smoke and heat. A novel response to the cues was observed for three species, with smoke reversing negative heat effects at 75°C, being supplanted by a positive heat response of unsmoked seed at 100°C. The response surface for duplicate populations of two of the three species examined was variable. Heat shock and smoke frequently combined to affect germination, in both positive and negative ways. Consequently, to gain an accurate assessment of the response of seeds to fires, an experimental design that samples within the potential response zones of germination cues is essential.

Effect of Potassium Chloride and Sodium Bicarbonate Supplementation on Thermotolerance of Broilers Exposed to Heat Stress

A t otal of 100-day-old broiler chicken were randomly divided into five groups and kept under elevated temperature (95-98.6 F) to observe the effect of potassium chloride and sodium bicarbonate on the o weight gain, feed conversion ratio (FCR), serum potassium and serum bicarbonate level. Thermostress lead to significant in decrease (P<0.05) weight gain, serum potassium and serum bicarbonate level, while FCR was increased. During heat stress, KCl and NaHCO at levels of 1.5% and 0.5% respectively, improved 3 weight gain, and FCR and significantly increased (P<0.05) serum potassium and bicarbonate level. The results showed that combination of KCl and NaHCO supplementation alleviated the negative effects of heat 3 stress in broilers.

Shade and water misting effects on behavior, physiology, performance, and carcass traits of heat-stressed feedlot cattle.

One hundred twelve crossbred feedlot heifers were used in two experiments to assess the impact of heat stress and its relief by shade and(or) water misting on behavior, physiology, performance, and carcass traits. Treatments were 1) no shading or misting (CONT); 2) only misting (MIST); 3) only shading (SHADE); and 4) shading plus misting (SHMI). Head in the feed bunk, head in or above the waterer, walking, standing, and lying behaviors were observed. Rectal temperature, respiration rate, and carcass traits were measured, as well as DMI, ADG, and feed:gain. Dietary NEm and NEg concentrations were calculated from performance data. In Exp. 1, (32 heifers; average BW 288 kg) the CONT heifers spent more time lying down than all others (P < 0.01). In addition, CONT heifers spent less time (P < 0.01) standing than SHADE and MIST heifers. Misting decreased (P < 0.01) rectal temperature and MIST as well as SHADE lowered (P < 0.05) respiration rates. In Exp. 2 (80 heifers; average BW = 336 kg), lying and walking behaviors did not differ among treatments, but shade increased (P < 0.01) standing behavior in heifers. The MIST cattle performed less (P < 0.05) head-above-water behavior than unmisted cattle. Rectal temperatures did not differ among treatments, but respiration rate was lower in shaded than in unshaded heifers (P < 0.05). Shaded compared with unshaded heifers had greater DMI (9.46 vs 8.80 +/- 0.14 kg/d, P < 0.01) and ADG (1.6 vs 1.41 +/- 0.1 kg/d, P < 0.01). Heifers provided with shade reached their target BW 20 d earlier than the unshaded heifers and differed in final BW (547 vs 520 +/- 6 kg, P < 0.01). Feed:gain and calculated NEg and NEm concentrations did not differ among treatments, and carcass traits were generally similar among treatments. In conclusion, cattle without shade had a physiological and behavioral stress response to heat that negatively affected productivity. Providing shade for beef cattle was a suitable solution to decrease heat stress and to lower the negative effects of heat on performance, whereas misting was largely ineffective.