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Letteratura scientifica selezionata sul tema "Testis Effect of heat on"

Autore: Grafiati

Pubblicato: 4 giugno 2021

Ultima modifica: 28 gennaio 2023

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Articoli di riviste sul tema "Testis Effect of heat on"

Hamilton, Thais Rose dos Santos, Adriano Felipe Perez Siqueira, Letícia Signori de Castro, Camilla Mota Mendes, Juliana de Carvalho Delgado, Patrícia Monken de Assis, Leonardo Pereira Mesquita et al. "Effect of Heat Stress on Sperm DNA: Protamine Assessment in Ram Spermatozoa and Testicle". Oxidative Medicine and Cellular Longevity 2018 (2018): 1–14. http://dx.doi.org/10.1155/2018/5413056.

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Sperm DNA fragmentation is considered one of the main causes of male infertility. The most accepted causes of sperm DNA damage are deleterious actions of reactive oxygen species (ROS), defects in protamination, and apoptosis. Ram sperm are highly prone to those damages due to the high susceptibility to ROS and to oxidative stress caused by heat stress. We aimed to evaluate the effects of heat stress on the chromatin of ejaculated and epididymal sperm and the activation of apoptotic pathways in different cell types in ram testis. We observed higher percentages of ejaculated sperm with increased chromatin fragmentation in the heat stress group; a fact that was unexpectedly not observed in epididymal sperm. Heat stress group presented a higher percentage of spermatozoa with DNA fragmentation and increased number of mRNA copies of transitional protein 1. Epididymal sperm presented greater gene expression of protamine 1 on the 30th day of the spermatic cycle; however, no differences in protamine protein levels were observed in ejaculated sperm and testis. Localization of proapoptotic protein BAX or BCL2 in testis was not different. In conclusion, testicular heat stress increases ram sperm DNA fragmentation without changes in protamination and apoptotic patterns.

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Hu, Suqin, Dianlong Liu, Sijia Liu, Chunrui Li e Jian Guo. "Lycium barbarum Polysaccharide Ameliorates Heat-Stress-Induced Impairment of Primary Sertoli Cells and the Blood-Testis Barrier in Rat via Androgen Receptor and Akt Phosphorylation". Evidence-Based Complementary and Alternative Medicine 2021 (3 maggio 2021): 1–10. http://dx.doi.org/10.1155/2021/5574202.

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Male infertility induced by heat stress has been attracting more and more attention. Heat stress not only causes apoptosis of spermatocytes but also has adverse effects on Sertoli cells, further damaging spermatogenesis. Lycium barbarum polysaccharide (LBP) is the main bioactive component of Lycium barbarum, which has a protective effect on male reproduction, but its mechanism is still unclear. In this study, our results proved that LBP blocked the inhibitory effect on the proliferation activity of Sertoli cells after heat stress, reversed the dedifferentiation of Sertoli cells induced by heat stress, and ameliorated the structural integrity of the blood-testis barrier. In addition, it increased the expression of the androgen receptor and activated Akt signaling pathway to resist heat-stress-induced injury of Sertoli cells.

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Setchell, B. P., A. Locatelli, C. Perreau, C. Pisselet, I. Fontaine, C. Kuntz, J. Saumande, J. Fontaine e M. T. Hochereau-de Reviers. "The form and function of the Leydig cells in hypophysectomized rams treated with pituitary extract when spermatogenesis is disrupted by heating the testes". Journal of Endocrinology 131, n. 1 (ottobre 1991): 101–12. http://dx.doi.org/10.1677/joe.0.1310101.

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ABSTRACT The morphology and in-vivo function of the Leydig cells were studied in rams when spermatogenesis had been disrupted by a single exposure of the testes 20 days earlier to a temperature of about 42 °C for 45 min. To avoid complications due to changed negative feedback from the testes to the pituitary with consequent changes in the degree of gonadotrophic stimulation, ten of the animals (five heated and five unheated) were surgically hypophysectomized when the testes were heated and then treated twice daily with pituitary extract. Six intact rams (three heated and three unheated) were also studied. The heat-affected testes were about half the size of the unheated testes, and blood plasma flow was closely related to testis weight. There were no differences in the testosterone concentrations in spermatic venous blood, testicular lymph or rete testis fluid, or in oestradiol in spermatic venous plasma from heated or unheated testes. Consequently, testosterone secretion by the heat-affected testes was markedly reduced, and the concentrations in jugular blood were also lower in the heat-affected rams than in controls. The volume of the interstitial tissue was less in absolute terms in the heat-affected rams, but it made up a greater fraction of the testes. The absolute volume of the blood plus lymph vessels, and their fraction of the interstitial tissue were lower in the heat-affected testes, although there was no effect on their volume as a fraction of the whole testis. The heat-affected testes of the hormone-treated rams had fewer Leydig cells, but each cell was larger; no equivalent difference was found in the intact rams. However, the dose of pituitary extract chosen was somewhat excessive, as there were higher than normal concentrations of FSH, LH and testosterone in jugular blood plasma, of testosterone and oestradiol in testicular venous blood plasma and of testosterone in rete testis fluid in the hormone-treated hypophysectomized rams. The testes of the unheated hypophysectomized rams increased in size by about 20% during treatment with pituitary extract, although testicular blood plasma flow was lower per unit weight of testis. The absolute volume of each Leydig cell and the total volume in absolute terms and as a fraction of the interstitial tissue was greater in the hormone-treated than in the untreated rams, but not the volume as a fraction of the whole testis. The total number of Leydig cells was higher in the hormone-treated unheated rams than in all the other rams taken together. It would therefore appear that when spermatogenesis was disrupted following heating of the testes and the gonadotrophic stimulation was kept constant, the Leydig cells underwent hypertrophy, presumably because of a change in the secretion of paracrine factor(s) by the tubules. However, there was also a decrease in testosterone secretion, which was closely related to decreases in blood plasma flow through the testes, and bore little or no relation to the number, total volume or size of the Leydig cells, or the concentration of testosterone in the testicular venous blood. Journal of Endocrinology (1991) 131, 101–112

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Kheradmand, Arash, Omid Dezfoulian e Mohammad Javad Tarrahi. "Ghrelin attenuates heat-induced degenerative effects in the rat testis". Regulatory Peptides 167, n. 1 (febbraio 2011): 97–104. http://dx.doi.org/10.1016/j.regpep.2010.12.002.

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Guo, Jian, Shi-Xin Tao, Min Chen, Yu-Qiang Shi, Zhu-Qiang Zhang, Yin-Chuan Li, Xue-Sen Zhang, Zhao-Yuan Hu e Yi-Xun Liu. "Heat Treatment Induces Liver Receptor Homolog-1 Expression in Monkey and Rat Sertoli Cells". Endocrinology 148, n. 3 (1 marzo 2007): 1255–65. http://dx.doi.org/10.1210/en.2006-1004.

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We demonstrated in this study that liver receptor homolog-1 (LRH-1) was expressed in the round spermatids in normal monkey testis, and no LRH-1 signal was observed in the Sertoli cells. After local warming (43 C) the monkey testis, however, LRH-1 expression was induced in the Sertoli cells in coincidence with activation of cytokeratin 18 (CK-18), a Sertoli cell dedifferentiated marker. Furthermore, we isolated rat primary Sertoli cells from testes at various stages of development and treated with 43 C water in vitro. The changes in LRH-1 as well as CK-18 expression were analyzed by confocal immunohistochemistry and Western blot. The results showed that LRH-1 was stage-dependently expressed in the Sertoli cells; no LRH-1-positive signal was detected in the cells obtained from the testes of adult rat on d 60 after birth when mature spermatozoa in the testis was completed. However, the mature Sertoli cells were warmed at the 43 C water bath for 15 min, and the LRH-1 signal was remarkably induced in a time-dependent manner, just like the changes of CK-18 expression in the Sertoli cells, suggesting that the heat-induced dedifferentiation of the mature Sertoli cells might be related to LRH-1 regulation. LRH-1 expression induced by the heat treatment was completely inhibited by the addition of ERK inhibitor U0126 in the culture, indicating that the heat-induced LRH-1 expression in the Sertoli cells may be regulated via ERK1/2 activation pathway. Testosterone was found to have no such effect on LRH-1 expression in the monkey and rat Sertoli cells.

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Hou, Ying, Peipei Yuan, Yang Fu, Qi Zhang, Yaxin Wei, Liyuan Gao, Li Liu, Xiaolan Wang, Xiaoke Zheng e Weisheng Feng. "Duzhong Butiansu Prescription Improves Heat Stress-Induced Spermatogenic Dysfunction by Regulating Sperm Formation and Heat Stress Pathway". Evidence-Based Complementary and Alternative Medicine 2020 (27 febbraio 2020): 1–11. http://dx.doi.org/10.1155/2020/6723204.

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Background. Duzhong Butiansu (DZBTS) prescription contains many traditional Chinese medicines and has been shown to have a curative effect on male fertility. However, the efficacy and mechanism of DZBTS in the treatment of male infertility induced by heat stress have not been reported. The aim of the present study is to elucidate the effect and mechanism of DZBTS on spermatogenic function of a heat stress model in rats. Methods. Male Wistar rats (280–320 g) were given different doses of DZBTS (0.4853 g/kg/d or 0.9707 g/kg/d), Shengjing capsule (0.56 g/kg/d), or double distilled water for 15 days. A 43°C hot water bath for 30 minutes was used to stimulate the testis of rats. Sperm count, sperm motility, the organ index of kidney and gonadal organs, serum sex hormone levels, and serum oxidising reaction index were measured. Haematoxylin and eosin (HE) staining was used to observe the morphology of the testis and kidney. The expression of Hsp70 in testes was observed by immunofluorescence. The changes in heat stress, reproductive-related protein, and mRNA were measured by western blot assay and RT-qPCR. Results. Heat stress downregulated the levels of sex hormone (P<0.05 or P<0.01) and its receptor androgen receptor (AR) protein expression and mRNA (P<0.01) in rats. Meanwhile, heat stress downregulated the levels of CAMP-responsive element-binding (CREB1) protein and mRNA (P<0.01), which are involved with spermatogenesis. Heat stress also decreased the oxidative damage index. Furthermore, Hsp70 and the heat shock transcription factor 1 (HSF1) protein pathway and mRNA level were overactivated (P<0.05 or P<0.01). Finally, the organ coefficients of the kidney and gonadal organs of rats were decreased. The sperm concentration and motility also decreased significantly (P<0.01). DZBTS could recover these changes induced by heat stress. Conclusions. Our results for the first time have found that DZBTS can improve spermatogenesis disorder in a heat stress model in rats, which may be mainly by regulating AR, sperm regulatory protein CREB1, and the HSF/Hsp70 signaling pathway to decrease oxidative stress.

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Mohajeri, D., e R. Kaffashi Elahi. "Effects of Nigella sativa on heat-induced testis damage in mouse". Bratislava Medical Journal 116, n. 04 (2015): 264–69. http://dx.doi.org/10.4149/bll_2015_051.

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Rahman, A., MM Hossain, M. Khan, MT Kamal e MA Hashem. "Effect of Heat Stress on Bucks Adaptability and Semen Characteristics". Journal of Environmental Science and Natural Resources 9, n. 1 (8 novembre 2016): 151–56. http://dx.doi.org/10.3329/jesnr.v9i1.30309.

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The experiment was conducted to investigate the effect of heat stress on adaptability and semen quality of buck. Almost similar 10 Black Bengal bucks were selected for the study at Artificial Insemination Centre, Bangladesh Agricultural University, Bangladesh. Prerequisite biological data were collected from each animal before keeping them sun heat and after 1 hour sun exposure. Different semen characteristics of each animal were measured. Temperature humidity index (THI) was 19.95 in the morning which indicate all the animals were in absence of heat stress and THI was 25.54 in the noon which indicate all the animals were in severe heat stress at noon. Buck 1 and buck 5 were more heat resistant (p<0.01), because their thermolysis capacity (TC) values were less than the others. There were no differences in tunica dartos index and semen characteristics among different bucks (p>0.05). Positive correlation between sperm motility and testis length (p<0.05), and negative correlation between sperm concentration and scrotal skin temperature (p<0.05) were found. From the study it can be concluded that all the bucks were in severe heat stress at noon time and TC can be used as an indicator for selection of buck for heat tolerance.J. Environ. Sci. & Natural Resources, 9(1): 151-156 2016

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Yaeram, J., B. P. Setchell e S. Maddocks. "Effect of heat stress on the fertility of male mice in vivo and in vitro". Reproduction, Fertility and Development 18, n. 6 (2006): 647. http://dx.doi.org/10.1071/rd05022.

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A study was conducted to determine whether following exposure of male mice to high temperatures, the ability of their spermatozoa to fertilise ova was reduced, especially during the period before the males became completely infertile. Male mice placed in a microclimate chamber at 36°C for two periods, each of 12 h on successive days, were less able to fertilise control females in vivo when mated and, even in those females that became pregnant, litter size was reduced. However, these effects were associated with falls in testis weight and numbers of spermatozoa in the testis and epididymis. To determine whether the effect on fertility was a result of the decreased spermatozoa numbers, spermatozoa were collected from the epididymides of heated and control males. Equal numbers of motile spermatozoa from an unselected sample or those subjected to a swim-up procedure to separate those that were motile from the immotile ones in the sample were then mixed in vitro with oocytes from superovulated normal females. Similar numbers of spermatozoa from both control and heated males bound to the zona pellucida but smaller percentages of the oocytes were fertilised by spermatozoa from the heated males and fewer of these spermatozoa penetrated the ova. The effects were first seen 7 days after the heat exposure and became more obvious after 10 or 14 days.

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Koide, Y., T. Ono, C. Ishinami e K. Yamashita. "Alterations in activities of calmodulin and heat-stable calmodulin-binding protein in rat testis". American Journal of Physiology-Cell Physiology 250, n. 2 (1 febbraio 1986): C299—C305. http://dx.doi.org/10.1152/ajpcell.1986.250.2.c299.

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Effects of postnatal development, surgical cryptorchidism, and hypophysectomy on the activity of calmodulin and of a 32,000-molecular weight (32) calmodulin-binding protein (Ono et al., J. Biol. Chem. 259: 9011-9016, 1984) were examined in rat testis. In adult rats, approximately 95% of their activities distributed in seminiferous tubule preparation, and most of them were in the 105,000-g supernatant. Both activities were low early in the development, but the calmodulin activity increased between 25 and 45 days of age, and the 32 K calmodulin-binding protein activity increased between 35 and 45 days of age. In contrast, surgical cryptorchidism caused a rapid decline in their activities in the abdominal testis, whereas their activities in a scrotal testis did not decline. Hypophysectomy similarly resulted in a gradual decline in their activities. Replacement of follicle-stimulating hormone or testosterone for 7 days from 30 days after hypophysectomy did not quantitatively restore either the testes weight or the activities of the proteins. The results indicate a primary distribution of both proteins in mature germ cells.

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Tesi sul tema "Testis Effect of heat on"

Gao, Jing, e 高晶. "Effect of acupuncture on the spermatogenesis of heat-treated rodent testis". Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B41291001.

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Gao, Jing. "Effect of acupuncture on the spermatogenesis of heat-treated rodent testis". Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B41291001.

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Yaeram, Jakrit. "The effect of whole body heating on testis morphology and fertility of male mice". Title page, table of contents and summary only, 2002. http://web4.library.adelaide.edu.au/theses/09PH/09phj259.pdf.

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Narang, Vikas A. "Heat Transfer Analysis In Steel Structures". Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-050405-133533/.

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Choi, Keum-Ran. "3D thermal mapping of cone calorimeter specimen and development of a heat flux mapping procedure utilizing an infrared camera". Link to electronic thesis, 2005. http://www.wpi.edu/Pubs/ETD/Available/etd-020205-215634/.

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Dissertation (Ph.D.)-- Worcester Polytechnic Institute.
Keywords: temperature measurement; heat flux maps; Cone Calorimeter; three-dimensional heat conduction; fire growth models; retainer frame; ceramic fiberboard; edge effect; one-dimensional heat conduction; heat flux mapping procedure; infrared camera; specimen preparation; edge frame; one-dimensional heat conduction model; thermal properties. Includes bibliographical references (p.202-204).

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Newton, Thomas Russell. "Investigation of the effect of process parameters on the formation of recast layer in wire-EDM of Inconel 718". Thesis, Atlanta, Ga. : Georgia Institute of Technology, 2008. http://hdl.handle.net/1853/22580.

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Zabida, Omer Saleh. "The effect of methamphetamine on the blood-testis barrier". University of the Western Cape, 2018. http://hdl.handle.net/11394/6775.

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>Magister Scientiae - MSc
Introduction The blood-testis barrier (BTB) is formed by tight junctions between adjacent Sertoli cells. The barrier formed by these tight junction helps to create a specialized environment for spermatogenesis and provide an immunological barrier to protect developing germ cells. Methamphetamine (Meth) is known as neurotoxin however, its effects on the male reproductive system, especially on Sertoli cells and, the BTB are not well established. Therefore, this study aimed to determine the effects of Meth on the TM4 mouse testis Sertoli cell line and on the integrity of the BTB permeability. Materials and Methods This study investigated the effect of selected concentrations of Meth (0.1 μM, 1 μM, 10 μM, 20 μM and 100 μM) on TM4 mouse testis Sertoli cell line for 24 until 96 hours, using two treatments: an “acute” study (24 hrs exposure) and a “chronic” study, where treatment occurred on a daily basis over 96 hrs. The following parameters were investigated: viability, cell proliferation, mitochondrial activity, monolayer permeability.

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Berny, Myriam. "High-temperature tests for ceramic matrix composites : from full-field regularised measurements to thermomechanical parameter identification". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPAST028.

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Cette thèse a pour objectif de développer une méthode de mesure de champs par corrélation d’images numériques (CIN) à haute température couplée à des mesures thermiques sur une éprouvette technologique en CMC sollicitée dans des conditions thermiques représentatives d’un environnement moteur et de mettre en place une méthodologie d’identification des propriétés thermiques et thermomécaniques du matériau, en quantifiant à chaque étape de la chaîne les incertitudes associées aux quantités d’intérêt et en les réduisant. Il a pour cela été nécessaire de traiter les défis inhérents à la CIN à chaud, que ce soit au niveau de l’acquisition des images (saturation, perte du contraste) ou de la mesure (artefacts dus à l’effet mirage, aussi appelé "brume de chaleur").Ces travaux ont ainsi donné lieu au développement d’un protocole d’étalonnage d’un banc multi-instrumenté par l’utilisation soit d’une mire in-situ, soit par auto-étalonnage en utilisant l’éprouvette elle-même et son environnement. Les mesures de déplacements 3D surfaciques (approches de stéréocorrélation globales) et les mesures thermiques ont permis de mettre en évidence ce phénomène de brume de chaleur. Des stratégies de régularisation spatiotemporelles des déplacements mesurés ont été proposées et ont permis d’obtenir des résultats satisfaisants (réduction significative des incertitudes de mesure). De même, des approches par réduction de modèles (POD) ont permis de traiter les données thermiques et de quantifier les incertitudes associées aux phénomènes convectifs. Enfin, un algorithme de recalage de modèle éléments finis pondéré sur les données de températures et de déplacements a été implémenté en vue d’identifier un ensemble de propriétés thermiques et thermomécaniques, en tenant compte de la sensibilité de chaque paramètre par rapport aux incertitudes de mesures
The aim of this thesis is firstly to develop procedures of full-field measurements with Digital Image Correlation (DIC), coupled to thermal measurements, suitable for high-temperature experiments on CMC specimens under thermal conditions representative of an engine environment. Secondly, a methodology is proposed for identifying the thermal and thermomechanical properties of the material, quantifying at each stage of the chain the uncertainties associated with the quantities of interest and strategies to reduce them. It was necessary to deal with the challenges due to high temperatures, especially for DIC, either in terms of acquisition (saturation, loss of contrast) or measurement (artefacts due to the mirage effect, also called "heat haze effect").This work has led to the development of a calibration protocol for a multi-instrumented bench using either an in-situ calibration target or by self-calibration using the specimen itself and its environment. 3D surface displacement measurements (with global stereocorrelation approaches) and thermal measurements have made it possible to highlight the heat haze effect phenomenon. Spatiotemporal regularisation strategies of the measured displacements were proposed and allowed satisfactory results to be obtained (significant reduction of measurement uncertainties). Similarly, model reduction approaches (POD) have been used to process thermal data and quantify the uncertainties associated with convective phenomena. Finally, a weighted Finite-Element Model Updating (FEMU) algorithm on both temperature and displacement data was implemented in order to identify a set of thermal and thermomechanical properties, taking into account the sensitivity of each parameter with regard to measurement uncertainties

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MIYAKE, KOJI, HATSUKI HIBI, KEISUKE YOKOI, SATOSHI KATSUNO e MASANORI YAMAMOTO. "THE EFFECT OF VARICOCELECTOMY ON TESTICULAR VOLUME IN INFERTILE PATIENTS WITH VARICOCELES". Nagoya University School of Medicine, 1995. http://hdl.handle.net/2237/16083.

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Reed, Daniel Kelvin. "THE EFFECT OF HYPEROXIC GAS MIXTURES ON RECOVERY FROM SHORT-TERM MAXIMAL EXERCISE (VENTILATION, HEART RATE, PH)". Thesis, The University of Arizona, 1986. http://hdl.handle.net/10150/276382.

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Medicine), Conference on Temperature and Environmental Factors and the Testis (1989 New York University School of. Temperature and environmental effects on the testis. New York: Plenum Press, 1991.

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Greenleaf, J. E. Effect of heat acclimation on sitting orthostatic tolerance in the heat after 48 and 96 hour bed rest in men. Moffett Field, Calif: National Aeronautics and Space Administration, Ames Research Center, 1995.

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Nelson, James B. Effect of long-term thermal aging on coated celion/LARC-160 composites. Hampton, Va: National Aeronautics and Space Administration, Langley Research Center, 1987.

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Conference on Characterization and NDE of Heat Damage in Graphite Epoxy Composites (1993 Orlando, Fla.). Conference on Characterization and NDE of Heat Damage in Graphite Epoxy Composites: Proceedings, April 27-28, 1993, Orlando, Florida. Austin, Tex: Nondestructive Testing Information Analysis Center (NTIAC), Texas Research Institute Austin, 1993.

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Hawthorne, J. R. Influence of fluence rate on radiation-induced mechanical property changes in reactor pressure vessel steels: Final report on exploratory experiments. Washington, DC: Division of Engineering, Office of Nuclear Regulatory Research, U.S. Nuclear Regulatory Commission, 1990.

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Lee, B. T. Effect of wall and room surfaces on the rates of heat, smoke, and carbon monoxide production in a park lodging bedroom fire. [Washington, D.C.]: U.S. Dept. of Commerce, National Bureau of Standards, 1985.

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Nover, Lutz. Heat shock response. Boca Raton, Fla: CRC Press, 1990.

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Josipovic, Stanislas. Heat stress: Causes, treatment and prevention. Hauppauge, N.Y: Nova Science Publishers, 2012.

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Workshop on Saving Energy and Reducing Atmospheric Pollution by Controlling Summer Heat Islands (1989 Berkley, Calif.). Controlling summer heat islands. Washington, D.C: U.S. Dept. of Energy, Building Systems Division, Office of Building and Community Systems, 1989.

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Sevilla, Law Torres, e Jovana Radulovic. "Exploring the Relationship Between Heat Absorption and Material Thermal Parameters for Thermal Energy Storage". In Springer Proceedings in Energy, 27–32. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-63916-7_4.

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AbstractUsing thermal energy storage alongside renewables is a way of diminishing the energy lack that exists when renewable energies are unable to run. An in-depth understanding of the specific effect of material properties is needed to enhance the performance of thermal energy storage systems. In this paper, we used fitting models and regression analysis to quantify the effect that latent heat of melting and material density have on the overall heat absorption. A single tank system, with encapsulated phase change materials is analysed with materials properties tested in the range of values commonly found in the literature. These materials are, therefore, hypothetically constructed ones based on materials such as paraffin. The software used for the numerical analysis is COMSOL Mulitphysics. Results show that the relationship between the latent heat and density regarding heat absorbed is a positive linear function for this system.

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Gooch, Jan W. "Heat Effect". In Encyclopedic Dictionary of Polymers, 360. New York, NY: Springer New York, 2011. http://dx.doi.org/10.1007/978-1-4419-6247-8_5837.

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Schultz, Richard M., Kimberly D. Tremblay, Adam S. Doherty e Marisa S. Bartolomei. "Effect of Embryo Culture on Imprinted Gene Expression in the Preimplantation Mouse Embryo". In The Testis, 245–55. New York, NY: Springer New York, 2000. http://dx.doi.org/10.1007/978-1-4612-2106-7_22.

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Rokade, Pramod Baburao. "Effect of Tannery Operations on Testis". In Impacts of Tannery Operations on Guppy, Poecilia reticulata, 33–36. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-57654-1_7.

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Saxena, Ajit Kumar, e Amit Kumar. "Effect of Cyclophosphamide on Testis—Protein Profile Study". In Fish Analysis for Drug and Chemicals Mediated Cellular Toxicity, 25–42. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-4700-3_3.

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Saxena, Ajit Kumar, e Amit Kumar. "Effect of Cyclophosphamide on Testis—A Histological Study". In Fish Analysis for Drug and Chemicals Mediated Cellular Toxicity, 43–58. Singapore: Springer Singapore, 2020. http://dx.doi.org/10.1007/978-981-15-4700-3_4.

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Kakaç, Sadik. "The Effect of Augmented Surfaces on Two-Phase Flow Instabilities". In Heat Transfer Enhancement of Heat Exchangers, 447–65. Dordrecht: Springer Netherlands, 1999. http://dx.doi.org/10.1007/978-94-015-9159-1_25.

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Zappoli, Bernard, Daniel Beysens e Yves Garrabos. "Thermovibrational Effect". In Heat Transfers and Related Effects in Supercritical Fluids, 345–64. Dordrecht: Springer Netherlands, 2014. http://dx.doi.org/10.1007/978-94-017-9187-8_17.

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Yu, Kuo-Tsong, e Xigang Yuan. "Simulation of Interfacial Effect on Mass Transfer". In Heat and Mass Transfer, 235–99. Berlin, Heidelberg: Springer Berlin Heidelberg, 2014. http://dx.doi.org/10.1007/978-3-642-53911-4_8.

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Yu, Kuo-Tsung, e Xigang Yuan. "Simulation of Interfacial Effect on Mass Transfer". In Heat and Mass Transfer, 311–78. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-2498-6_9.

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Atti di convegni sul tema "Testis Effect of heat on"

Del Col, Davide, Stefano Bortolin, Alberto Cavallini e Marko Matkovic. "Effect of Minichannel Cross Sectional Shape in Condensation". In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22847.

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The objective of this work is to present new condensation heat transfer coefficients measured inside a single square cross section minichannel, having a 1.18 m side length, and compare them to the ones measured in a circular minichannel. This subject is particularly interesting since most of the mini and microchannels used in practical applications have non circular cross sections. The test section used in the present work is obtained from a thick wall copper tube which is machined to draw a complex passage for the coolant. This experimental technique allows to measure directly the temperature in the tube wall and in the water channel. The heat flux is determined from the temperature profile of the coolant in the measuring sector. The experimental technique is checked in single phase runs which represent a severe testing condition due to the low values of heat flux. Tests have been performed with R134a at 40°C saturation temperature, at mass velocities ranging between 200 and 800 kg m−2s−1. As compared to the heat transfer coefficients measured in a circular minichannel, in the square minichannel the authors find that heat transfer is enhanced at the lowest values of mass velocity; this must be due to the effect of the surface tension. No heat transfer coefficient increase has been found at the highest values of the mass velocity where condensation seems to be shear stress dominated.

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Mogaji, T. S., O. A. Sogbesan e Tien-Chien Jen. "Effect of Heat Flux on Pool Boiling Heat Transfer Enhancement (Numerical Investigation Approach)". In ASME 2020 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/imece2020-23432.

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Abstract This study presents numerical investigation results of heat flux effect on pool boiling heat transfer enhancement during nucleate boiling heat transfer of water. The simulation was performed for five different heated surfaces such as: brass, copper, mild steel, stainless steel and aluminum using ANSYS simulation software at 1 atmospheric pressure. The samples were heated in a domain developed for bubble growth during nucleate boiling process under the same operational condition of applied heat flux ranged from 100 to 1000 kW/m2 and their corresponding heat transfer coefficient was obtained numerically. Obtained experimental data of other authors from the open literature result is in close agreement with the simulated data, thus confirming the validity of the CFD simulation method used in this study. It is found that heat transfer coefficient increases with increasing heat flux. The results revealed that in comparison to other materials tested, better heat transfer performance up to 38.5% and 7.11% is observed for aluminum and brass at lower superheated temperature difference conditions of 6.96K and 14.01K respectively. This behavior indicates better bubble development and detachment capability of these heating surface materials and could be used in improving the performance of thermal devices toward producing compact and miniaturized equipment.

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Kim, Moo Hwan. "The Effect of Nanoscale Surface Modification on Boiling Heat Transfer and Critical Heat Flux". In ASME 2010 8th International Conference on Nanochannels, Microchannels, and Minichannels collocated with 3rd Joint US-European Fluids Engineering Summer Meeting. ASMEDC, 2010. http://dx.doi.org/10.1115/fedsm-icnmm2010-31276.

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Recently, there were lots of researches about enormous CHF enhancement with the nanofluid in pool boiling and flow boiling. It is supposed the deposition of nanoparticles on the heated surface is one of main reasons. In a real application, nanofluid has a lot of problems to be used as the working fluid because of sedimentation and aggregation. The artificial surfaces on silicon and metal were developed to have the similar effect with nanoparticles deposited on the surface. The modified surface showed the enormous ability to increase CHF in pool boiling. Furthermore, under flow boiling, it had also good results to increase CHF. In these studies, we concluded that wetting ability of surface; e.g. wettability and liquid spreading ability (hydrophilic property of surface) was a key parameter to increase CHF under both pool and flow boiling. In addition, using wettability difference of surface; e.g. hydrophilic and hydrophobic, we conducted some tests of BHT (boiling heat transfer) enhancement using the oxide silicon which have micro-sized hydrophobic islands on hydrophilic surface. By using both of these techniques, we propose an optimized surface to increase both CHF and BHT. Also, the fuel surface of nuclear power plants is modified to have same effect and the results shows a good enhancement of CHF, too.

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Kandlikar, Satish G., e Paul H. Spiesman. "Effect of Surface Finish on Flow Boiling Heat Transfer". In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0592.

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Abstract It is well known that the surface structure affects the pool boiling heat transfer from a heater surface. The number and size distribution of cavities present on a heater surface affect the nucleation characteristics. This fact is utilized in developing structured and sintered surfaces for enhanced boiling performance. The nucleate boiling component in flow boiling is also expected to exhibit a somewhat similar dependence. The present study investigates the flow boiling heat transfer of subcooled water over heater surfaces prepared with different roughness characteristics. The setup consists of a 9.5 mm diameter circular heater placed on the lower wall of a 3 mm × 40 mm horizontal channel. Four different surface finishes are tested on the same heater unit. Each surface is observed under a microscope, and analyzed with an image processing software to obtain the cavity size distribution. Relationships between the cavity size distribution and the heat transfer are then compared for the four surfaces. The results indicate that the wall superheats for the four surfaces tested were within 0–30 percent of each other for a given heat flux. Although the roughest surface generally performed the best, no definite trend could be observed. It is also noted that the cavity size distribution of a surface is not significantly affected by simple polishing techniques. A commercially prepared sintered surface is also tested. Its performance was markedly above the four roughened surfaces. However, the sintered surface exhibited a large hysteresis effect, while the four roughened surfaces showed little hysteresis under the test conditions.

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Fitzgerald, Claire L., Adrian Briggs, Huasheng Wang e John W. Rose. "Effect of Vapour Velocity on Condensation of Ethylene Glycol on Horizontal Integral Fin Tubes: Heat Transfer and Retention Angle Measurements". In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22254.

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Heat-transfer data are reported for forced-convection filmwise condensation of ethylene glycol flowing vertically downward over two single, horizontal instrumented integral-fin tubes and one plain tube. Vapor-side, heat-transfer coefficients were obtained by direct measurement of the tube wall temperature using two specially manufactured, instrumented tubes with thermocouples embedded in the tube walls. Both tubes have fin height of 1.6 mm and fin root diameter and 12.7 mm, with fin thickness and spacings of 0.3 mm and 0.6 mm, respectively for one of the tubes and 0.5 mm and 1 mm, respectively for the other. Tests were performed at low pressures; 5.59kPa, 8.15kPa and 11.23kPa, at nominal vapour velocities from 13m/s to 82 m/s. All the data show that both of the finned tubes provided an increase in heat flux at the same vapour-side temperature difference with increasing vapour velocity. Visual observations were made and photographs obtained of the fluid retention angle φf at each combination of vapor velocity and pressure tested. It was observed that the curvature of the meniscus was distorted by the increase in vapor velocity and in many cases, the extent of condensate flooding decreased compared to its value in the quiescent vapor case.

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Rodriguez, Luis Rafael Miranda, Neel Shah, Aisha S. Haynes, Calvin Lim, Christopher G. Stout, Stephen S. Recchia e Assimina A. Pelegri. "Effect of Heat Stabilization and Solid Lubricants on High Strain Rate Response of Polyamide 6". In ASME 2021 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2021. http://dx.doi.org/10.1115/imece2021-73354.

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Abstract In this research, high strain rate impact testing of polyamide 6 composites (PA6) with different inclusions and processes is performed to assess the material response to increasing impact loads. Testing groups are divided into four categories depending on their inclusions and process: no inclusions, heat stabilized with no inclusions, oil & Molybdenum disulfide (MoS2), and glass fiber solid lubricant. Computational analysis is performed to obtain material properties such as dynamic modulus and stress-strain behavior from Split Hopkinson Pressure Bar (SHPB) tests. Out of the four groups, it was concluded that oil & MoS2 and glass fiber solid lubricant were more capable of maintaining dynamic modulus. In contrast, PA6 without any inclusions experienced a rapid decrease in dynamic modulus with increasing strain rate. Microscopic imagery is taken to evaluate crack formation in samples and sample deformation. Multiple side and edge cracks were developed from the specimens starting from a strain rate of 1900s−1; however, shattering of specimens was not experienced until above 2300s−1 strain rates were achieved. It is concluded that tested specimens experienced hardening trends at higher testing pressures and strain rates. A computational analysis is underway to establish the effect of heat stabilization and lubricant inclusions in PA6 strain rate-dependent mechanical response.

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Jahangirian, S., M. Abarham, A. Ghafourian e M. H. Saidi. "Effect of Vortex Flow on Heat Transfer to Combustion Chamber Wall". In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-59550.

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A new experimental facility was designed, fabricated and tested to model and study the effect of bidirectional swirl flow on the rate of heat transfer to combustion chamber walls in many applications. Heat transfer to combustion chamber walls is an unwanted phenomenon. Reduction of this heat transfer can result in time and cost saving methods in design and fabrication of combustion chambers. The experimental study was performed by using propane and air with oxygen as fuel and oxidizer respectively. The location of injection ports and geometry of combustion chamber are flexible and could be varied. Tests were performed with different mass flow rates of fuel and oxidizer. For the same flow rates and with the presence of bidirectional flow, a wall temperature reduction of up to 50% was observed. In cases where only some of the oxidizer was injected from the chamber end to generate the bidirectional swirl flow, highest efficiency and lowest wall temperature existed. This can be due to better mixing of fuel and oxidizer and absence of hot spots in the combusting core. Further development of this technique enables combustion chamber manufacturers in a wide spectrum of industries such as gas turbine manufacturers to use less expensive and more available material in their production of combustors.

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Lee, Suvit, Dazhong Yuan e Bangxian Wu. "Experimental Study on Counter-Gravity Effect of Non-Phase Change Heat Pipes". In 2010 14th International Heat Transfer Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ihtc14-22555.

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An innovative concept of Non-Phase Change Heat Pipe (NPC-HP) was recently proposed by the present authors. Different shapes of NPC-HP with different structures have been successfully developed in our laboratory. The heat transfer in NPC-HP is not dependent on phase change, but on pressure response to temperature change. With the external heat source as the driving force, the remarkable pressure rise of the working medium inside NPC-HP resulting from the heat input precedes the rise of the saturated vapor pressure, thus effectively restrains the phase change in the loop pipe and finally results in a special heat transfer mode with phase change suppressed. NPC-HP has much higher heat flux (as high as 104 W/cm2) and much higher heat transfer rate compared to traditional heat transfer components. Besides, NPC-HP overcomes the deficiencies or limitations of conventional heat pipes, such as the dry-up phenomenon, the difficulty of heat transfer in counter-gravitational direction, etc. It is, in fact, a new generation of heat transfer components with a completely new mechanism. In order to testify the counter-gravity effect of NPC-HP, an experiment for downward heat transmission in NPC-HP is arranged. The test result demonstrates the superior capability of downward heat transfer of NPC-HP. For heating power of 275W, heat effectively transmits downwards to the cooling end of the pipe at the vertical distance of 1.68m from the heating position. The temperature difference is about 7°C from the top to the bottom of the pipe. This result is hardly realizable in conventional heat pipes. A preliminary analysis on the mechanism of downward heat transfer is then made. For an effective downward heat transfer, it is essential for NPC-HP to keep phase change effectively and opportunely suppressed in the loop pipe as well as to further keep natural convection restrained. Because of its superior performance, NPC-HP will undoubtedly become a new generation of heat transfer components, and have wide applications in different industries.

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Kedzierski, Mark A. "Effect of Diamond Nanolubricant on R134a Pool Boiling Heat Transfer". In ASME 2009 Second International Conference on Micro/Nanoscale Heat and Mass Transfer. ASMEDC, 2009. http://dx.doi.org/10.1115/mnhmt2009-18032.

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This paper quantifies the influence of diamond nanoparticles on the pool boiling performance of R134a/polyolester mixtures on a roughened, horizontal, flat surface. Nanofluids are liquids that contain dispersed nano-size particles. A lubricant based nanofluid (nanolubricant) was made by suspending 10 nm diameter diamond particles in a synthetic ester to roughly a 2.6% volume fraction. For the 0.5% nanolubricant mass fraction, the nanoparticles caused a heat transfer enhancement relative to the heat transfer of pure R134a/polyolester (99.5/0.5) as large as 129% for the best performing tests. A similar enhancement was observed for the R134a/nanolubricant (99/1) mixture, which had a heat flux that was on average 91% larger than that of the R134a/polyolester (99/1) mixture. Further increase in the nanolubricant mass fraction to 2% resulted in boiling heat transfer degradation of approximately 19% for the best performing tests. It was speculated that the poor quality of the nanolubricant suspension caused the performance of the (99.5/0.5), and the (98/2) nanolubricant mixtures to decay over time to, on average, 36% and 76% of the of pure R134a/polyolester performance, respectively. Thermal conductivity and viscosity measurements and a refrigerant\lubricant mixture pool-boiling model were used to suggest that increases in thermal conductivity and lubricant viscosity are mainly responsible for the heat transfer enhancement due to nanoparticles. Particle size measurements were used to suggest that particle agglomeration induced a lack of performance repeatability for the (99.5/0.5) and the (98/2) mixtures. From the results of the present study, it is speculated that if a good dispersion of nanoparticles in the lubricant is not obtained, then the agglomerated nanoparticles will not provide interaction with bubbles, which is favorable for heat transfer. Further research with nanolubricants and refrigerants are required to establish a fundamental understanding of the mechanisms that control nanofluid heat transfer.

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Guan, Ning, Zhigang Liu e Chengwu Zhang. "Viscous Dissipation Effect of Liquid Flow in Microtubes". In ASME 2008 First International Conference on Micro/Nanoscale Heat Transfer. ASMEDC, 2008. http://dx.doi.org/10.1115/mnht2008-52136.

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Viscous dissipation effects on de-ionized ultra pure water flow through smooth quartz glass microtubes with different inner diameters are investigated numerically and experimentally as the Reynolds number varies in the range from 0 to 700. In present study, a 2-D model adapted to microtube is presented to analyze the viscous dissipation characteristic in microtube considering EDL effect. According to the numerical simulation results, a new criterion Vc demonstrating the law of the viscous dissipation in microtube is summed up in this paper. Based on the micro-area thermal-imaging technology and a series of correction tests, the viscous heating temperature rise in microtube can be exactly measured by an IR camera with a special magnifying lens. Moreover, the temperature rise of the working fluid resulted from the heat generated by the pump is also considered in present experiments. The experimental results are compared with predictions of the numerical simulation and the theoretical Vc correlation. The comparisons indicate that the experimental data are in accordance with numerical and theoretical results.

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Rapporti di organizzazioni sul tema "Testis Effect of heat on"

Hansen, Peter J., e Zvi Roth. Use of Oocyte and Embryo Survival Factors to Enhance Fertility of Heat-stressed Dairy Cattle. United States Department of Agriculture, agosto 2011. http://dx.doi.org/10.32747/2011.7697105.bard.

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The overall goal was to identify survival factors that can improve pregnancy success following insemination or embryo transfer in lactating dairy cows exposed to heat stress. First, we demonstrated that oocytes are actually damaged by elevated temperature in the summer. Then we tested two thermoprotective molecules for their effect on oocyte damage caused by heat shock. One molecule, ceramide was not thermoprptective. Another, insulin-like growth factor-1 (IGF) reduced the effects of heat shock on oocyte apoptosis and oocyte cleavage when added during maturation. We also used lactating cows exposed to heat stress to determine whether bovine somatotropin (bST), which increases IGF1 levels in vivo, would improve fertility in summer. Cows treated with bST received a single injection at 3 days before insemination. Controls received no additional treatment. Treatment with bST did not significantly increase the proportion of inseminated cows diagnosed pregnant although it was numerically greater for the bST group (24.2% vs 17.8%, 124–132 cows per group). There was a tendency (p =0.10) for a smaller percent of control cows to have high plasma progesterone concentrations (≥ 1 ng/ml) at Day 7 after insemination than for bST-treated cows (72.6 vs 81.1%). When only cows that were successfully synchronized were considered, the magnitude of the absolute difference in the percentage of inseminated cows that were diagnosed pregnant between bST and control cows was reduced (24.8 vs 22.4% pregnant for bST and control). Results failed to indicate a beneficial effect of bST treatment on fertility of lactating dairy cows. In another experiment, we found a tendency for addition of IGF1 to embryo culture medium to improve embryonic survival after embryo transfer when the experiment was done during heat stress but not when the experiment was done in the absence of heat stress. Another molecule tested, granulocyte-macrophage colony-stimulating factor (GM-CSF; also called colony-stimulating factor-2), improved embryonic survival in the absence of heat stress. We also examined whether heat shock affects the sperm cell. There was no effect of heat shock on sperm apoptosis (programmed cell death) or on sperm fertilizing ability. Therefore, effects of heat shock on sperm function after ejaculation if minimal. However, there were seasonal changes in sperm characteristics that indicates that some of the decrease in dairy cow fertility during the summer in Israel is due to using semen of inferior quality. Semen was collected from five representative bulls throughout the summer (August and September) and winter (December and January). There were seasonal differences in ion concentration in seminal plasma and in the mRNA for various ion channels known to be involved in acrosome reactions. Furthermore, the proportion of sperm cells with damaged acrosomes was higher in post-thaw semen collected in the summer than in its counterpart collected in winter (54.2 ± 3.5% vs. 51.4 ± 1.9%, respectively; P < 0.08Further examination is required to determine whether such alterations are involved in the low summer fertility of dairy cows.

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Johra, Hicham. Performance overview of caloric heat pumps: magnetocaloric, elastocaloric, electrocaloric and barocaloric systems. Department of the Built Environment, Aalborg University, gennaio 2022. http://dx.doi.org/10.54337/aau467469997.

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Heat pumps are an excellent solution to supply heating and cooling for indoor space conditioning and domestic hot water production. Conventional heat pumps are typically electrically driven and operate with a vapour-compression thermodynamic cycle of refrigerant fluid to transfer heat from a cold source to a warmer sink. This mature technology is cost-effective and achieves appreciable coefficients of performance (COP). The heat pump market demand is driven up by the urge to improve the energy efficiency of building heating systems coupled with the increase of global cooling needs for air-conditioning. Unfortunately, the refrigerants used in current conventional heat pumps can have a large greenhouse or ozone-depletion effect. Alternative gaseous refrigerants have been identified but they present some issues regarding toxicity, flammability, explosivity, low energy efficiency or high cost. However, several non-vapour-compression heat pump technologies have been invented and could be promising alternatives to conventional systems, with potential for higher COP and without the aforementioned refrigerant drawbacks. Among those, the systems based on the so-called “caloric effects” of solid-state refrigerants are gaining large attention. These caloric effects are characterized by a phase transition varying entropy in the material, resulting in a large adiabatic temperature change. This phase transition is induced by a variation of a specific external field applied to the solid refrigerant. Therefore, the magnetocaloric, elastocaloric, electrocaloric and barocaloric effects are adiabatic temperature changes in specific materials when varying the magnetic field, uniaxial mechanical stress, electrical field or hydrostatic pressure, respectively. Heat pump cycle can be built from these caloric effects and several heating/cooling prototypes were developed and tested over the last few decades. Although not a mature technology yet, some of these caloric systems are well suited to become new efficient and sustainable solutions for indoor space conditioning and domestic hot water production. This technical report (and the paper to which this report is supplementary materials) aims to raise awareness in the building community about these innovative caloric systems. It sheds some light on the recent progress in that field and compares the performance of caloric systems with that of conventional vapour-compression heat pumps for building applications.

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Hansen, Peter J., Zvi Roth e Jeremy J. Block. Improving oocyte competence in dairy cows exposed to heat stress. United States Department of Agriculture, gennaio 2014. http://dx.doi.org/10.32747/2014.7598163.bard.

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Original Objectives. The overall goal is to develop methods to increase pregnancy rate in lactating dairy cows exposed to heat stress through methods that minimize damage to the oocyte and embryo caused by heat stress. Objectives were as follows: (1) examine the protective effects of melatonin on developmental competence of oocytes exposed to elevated temperature in vitro; (2) test whether melatonin feeding can improve developmental competence of oocytes in vivo and, if so, whether effects are limited to the summer or also occur in the absence of heat stress; and (3) evaluate the effectiveness of improving fertility by facilitating follicular turnover in the summer and winter. Revised Objectives. (1) Examine protective effects of melatonin and follicular fluid on developmental competence of oocytes exposed to elevated temperature in vitro; (2) examine the protective effects of melatonin on developmental competence of embryos exposed to elevated temperature in vitro; (3) evaluate effectiveness of improving fertility by administering human chorionicgonadotropin (hCG) to increase circulating concentrations of progesterone and evaluate whether response to hCG depends upon genotype for four mutations reported to be related to cow fertility; and (4) identify genes with allelic variants that increase resistance of embryos to heat shock. Background. The overall hypothesis is that pregnancy success is reduced by heat stress because of damage to the oocyte and cleavage-stage embryo mediated by reactive oxygen species (ROS), and that fertility can be improved by provision of antioxidants or by removing follicles containing oocytes damaged by heat stress. During the study, additional evidence from the literature indicated the potential importance of treatment with chorionicgonadotropin to increase fertility of heat- stressed cows and results from other studies in our laboratories implicated genotype as an important determinant of cow fertility. Thus, the project was expanded to evaluate hCG treatment and to identify whether fertility response to hCG depended upon single nucleotide polymorphisms (SNP) in genes implicated as important for cow fertility. We also evaluated whether a SNP in a gene important for cellular resistance to heat stress (HSPA1L, a member of the heat shock protein 70 family) is important for embryonic resistance to elevated temperature. Major conclusions, solutions & achievements. Results confirmed that elevated temperature increases ROS production by the oocyte and embryo and that melatonin decreases ROS. Melatonin reduced, but did not completely block, damaging effects of heat shock on the oocyte and had no effect on development of the embryo. Melatonin was protective to the oocyte at 0.1-1 μM, a concentration too high to be achieved in cows. It was concluded that melatonin is unlikely to be a useful molecule for increasing fertility of heat-stressed cows. Treatment with hCG at day 5 after breeding increased first-service pregnancy rate for primiparous cows but not for multiparous cows. Thus, hCG could be useful for increasing fertility in first-parity cows. The effectiveness of hCG depended upon genotype for a SNP in COQ9, a gene encoding for a mitochondrial-function protein. This result points the way to future efforts to use genetic information to identify populations of cows for which hormone treatments will be effective or ineffective. The SNP in HSPA1L was related to embryonic survival after heat shock. Perhaps, genetic selection for mutations that increase cellular resistance to heat shock could be employed to reduce effects of heat stress on fertility. Implications, both scientific and agricultural. This project has resulted in abandonment of one possible approach to improve fertility of the heat-stressed cow (melatonin therapy) while also leading to a method for improving fertility of primiparous cows exposed to heat stress (hCG treatment) that can be implemented on farms today. Genetic studies have pointed the way to using genetic information to 1) tailor hormonal treatments to cow populations likely to respond favorably and 2) select animals whose embryos have superior resistance to elevated body temperatures.

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Lee, K. H., e Tzou-Shin Ueng. Air-injection field tests to determine the effect of a heat cycle on the permeability of welded tuff. Office of Scientific and Technical Information (OSTI), ottobre 1991. http://dx.doi.org/10.2172/138216.

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Berry, Terri-Ann, Jordan H. D. Chiswell, Shannon L. Wallis e Roger Birchmore. The Effect of Airtightness on Indoor Air Quality in Timber Houses in New Zealand. Unitec ePress, dicembre 2017. http://dx.doi.org/10.34074/ocds.92017.

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This two-part study considers the impact of airtightness based on volatile organic compounds (VOCs) only. Two identical buildings (test and control) were constructed in Auckland, New Zealand. The test building contained an Intello vapour check membrane to reduce air-flow and subsequent heat loss. Air change rates (air changes per hour, or ACH) were calculated from air-leakage rates in each of the buildings. Data analysis demonstrated that the VOC levels in the test house were consistently higher than those established in the control house.

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Wolfenson, David, William W. Thatcher, Rina Meidan, Charles R. Staples e Israel Flamenbaum. Hormonal and Nutritional Stretegies to Optimize Reproductive Function and Improve Fertility of Dairy Cattle during Heat Stress in Summer. United States Department of Agriculture, agosto 1994. http://dx.doi.org/10.32747/1994.7568773.bard.

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The BARD program includes two main parts. In the first, experiments were conducted to complete our understanding of the mechanisms responsible for the impairment of reproductive functions under heat stress. Experiments focused on follicular development and function, since results obtained in our previous BARD project indicate that the preovulatory follicle is susceptible to heat stress. The theca cells, sensitive to thermal stress, produced less androgen during the summer, as well as during the autumn. Similarly, luteinized theca cells obtained from cows in summer produced much less progesterone than in winter. Granulosa cells and luteinized granulosa cells were less susceptible to heat stress. A delayed effect of heat stress on follicular development, on suppression of dominance and on steroid production by theca and granulosa cells was noted. This may be related to the low fertility of cows during the cool months of autumn. In the second part, experiments were conducted aiming to improve fertility in summer. The timed AI program was developed using two injections of GnRH coupled with PGF2a. It was found effective in improving reproductive performance in lactating cows. Limitations induced by heat stress on estrus detection were eliminated with the timed AI management program. Replacing the second injection of GnRH with hCG instead of GnRH agonist increased plasma progesterone levels post ovulation but did not improve fertility. Use of the timed AI program in summer, shortened days open and increased the net revenue per cow, however, it did not protect the embryo fiom temperature-induced embryonic mortality. Incorporation of a GnRH-agonist implant into the timed AJ program was examined. The implant increased plasma progesterone and LH concentrations and altered follicular dynamics. The use of a GnRH-implant enhanced pregnancy rate in cows with low body conditions. In a timed embryo transfer experiment, the use of fresh or frozen in vitro produced embryos was compared in the summer to improve fertility. The use of flesh embryos (but not frozen ones) improved pregnancy rate, however, substantial embryonic death occurred between 21 and 45 days. The timed AI program, which is now being used commercially, shortened days open, and increased pregnancy rate during summer. Other approaches which were found to improve fertility in small-scale studies, need to be tested again in large-scale field trials.

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Dahl, Geoffrey E., Sameer Mabjeesh, Thomas B. McFadden e Avi Shamay. Environmental manipulation during the dry period of ruminants: strategies to enhance subsequent lactation. United States Department of Agriculture, febbraio 2006. http://dx.doi.org/10.32747/2006.7586544.bard.

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The project resulted from earlier observations that environmental factors, especially photoperiod and temperature, had profound effects on milk yield in dairy cattle during lactation. More recently we had determined that photoperiod manipulation during the dry period altered milk yield in the next lactation, and this was associated with shifts in circulating concentrations of prolactin; specifically exposure to short days during the dry period decreases prolactin but increases milk yield. Because prolactin is also affected by temperature, with heat stress causing an increase in prolactin similar to that of long day exposure, we focused our efforts on determining prolactin signaling provides a common pathway for generation of environmental effects on mammary growth, development and subsequent function during the dry period of dairy ruminants. Over the project period we made significant progress toward testing our hypotheses that (I): In cows, there is a discrete duration of time during the dry period in which exposure to short days will result in optimal enhancement of mammary development and milk yield in the following lactation, and that this effect is mediated through demonstrable changes in mammary gland development, prolactin signaling, and mammary gene expression; and (II): Modulation of photoperiod and temperature during the dry period will affect milk yield in goats in the subsequent lactation via shifts in nutrient and endocrine partitioning, and mammary gene expression, during the dry period and into lactation. Cows exposed to short days for only the final 21 days of the dry period did not produce more milk that those on long day or natural photoperiod when dry. However, cows on short days for the entire 60 days dry did produce more milk than the other 3 groups. This indicates that there is a duration effect of short day exposure on subsequent milk yield. Results of the second study in cows indicate that mammary growth increases differentially during the dry period under long vs. short days, and that short days drive more extensive growth which is associated with altered prolactin signaling via decreases in an suppressors of cytokine signaling that represent an inhibitory pathway to mammary growth. Evidence from the studies in Israel confirms that goats respond to short days during the dry period in a similar manner to cows. In addition, heat stress effects on during the dry period can be limited by exposure to short days. Here again, shifts in prolactin signaling, along with changes in IGF-I secretion, are associated with the observed changes in mammary function in goats. These results have a number of biological and practical implications. For dairy producers, it is clear that we can recommend that cows and goats should be on reduced light exposure during the dry period, and further, cows and goats should be cooled to avoid heat stress during that time. Environmental influences on mammary growth are apparent during the dry period, and those effects have persistent impact in the subsequent lactation. Prolactin signaling is a consistent mechanism whereby extended light exposure and heat stress may depress mammary growth and development during the dry period. Thus, the prolactin signaling system offers an opportunity for further manipulation to improve production efficiency in dairy ruminants.

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El Halawani, Mohamed, e Israel Rozenboim. Environmental factors affecting the decline in reproductive efficiency of turkey hens: Mediation by vasoactive intestinal peptide. United States Department of Agriculture, gennaio 2007. http://dx.doi.org/10.32747/2007.7696508.bard.

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Reproductive failure associated with heat stress is a well known phenomenon in avian species. Increased prolactin (PRL) levels in response to heat stress have been suggested as a mechanism involved in this reproductive malfunction. To test this hypothesis, laying female turkeys were subjected to 40°C for 12 h during the photo-phase daily or maintained at 24–26°C. Birds in each group received oral treatment with parachlorophenyalanine (PCPA; 50 mg/kg BW/day for 3 days), an inhibitor of serotonin (5-HT) biosynthesis; or immunized against vasoactive intestinal peptide (VIP). Both treatments are known to reduce circulating PRL levels. Non treated birds were included as controls. In the control group, high ambient temperature terminated egg laying, induced ovarian regression, reduced plasma luteinizing hormone (LH) and ovarian steroids (progesterone, testosterone, estradiol) levels, and increased plasma PRL levels and the incidence of incubation behavior. Pretreatment with PCPA reduced (P< 0.05) heat stress-induced decline in egg production, increase in PRL levels, and expression of incubation behavior. Plasma LH and ovarian steroid levels of heat stressed birds were restored to that of controls by PCPA treatment. As in PCPA-treated birds, VIP immunoneutralization of heat-stressed turkeys reduced (P< 0.05) circulating PRL levels and prevented the expression of incubation behavior. But it did not restore the decline in LH, ovarian steroids, and egg production (P> 0.05). The present findings indicate that the detrimental effect of high temperature on reproductive performance may not be related to the elevated PRL levels in heat-stressed birds but to mechanism(s) that involve 5-HT neurotransmission and the induction of hyperthermia.

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Seginer, Ido, Daniel H. Willits, Michael Raviv e Mary M. Peet. Transpirational Cooling of Greenhouse Crops. United States Department of Agriculture, marzo 2000. http://dx.doi.org/10.32747/2000.7573072.bard.

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Background Transplanting vegetable seedlings to final spacing in the greenhouse is common practice. At the time of transplanting, the transpiring leaf area is a small fraction of the ground area and its cooling effect is rather limited. A preliminary modeling study suggested that if water supply from root to canopy is not limiting, a sparse crop could maintain about the same canopy temperature as a mature crop, at the expense of a considerably higher transpiration flux per leaf (and root) area. The objectives of this project were (1) to test the predictions of the model, (2) to select suitable cooling methods, and (3) to compare the drought resistance of differently prepared seedlings. Procedure Plants were grown in several configurations in high heat load environments, which were moderated by various environmental control methods. The difference between the three experimental locations was mainly in terms of scale, age of plants, and environmental control. Young potted plants were tested for a few days in small growth chambers at Technion and Newe Ya'ar. At NCSU, tomato plants of different ages and planting densities were compared over a whole growing season under conditions similar to commercial greenhouses. Results Effect of spacing: Densely spaced plants transpired less per plant and more per unit ground area than sparsely spaced plants. The canopy temperature of the densely spaced plants was lower. Air temperature was lower and humidity higher in the compartments with the densely spaced plants. The difference between species is mainly in the canopy-to-air Bowen ratio, which is positive for pepper and negative for tomato. Effect of cooling methods: Ventilation and evaporative pad cooling were found to be effective and synergitic. Air mixing turned out to be very ineffective, indicating that the canopy-to-air transfer coefficient is not the limiting factor in the ventilation process. Shading and misting, both affecting the leaf temperature directly, proved to be very effective canopy cooling methods. However, in view of their side effects, they should only be considered as emergency measures. On-line measures of stress: Chlorophyll fluorescence was shown to accurately predict photosynthesis. This is potentially useful as a rapid, non-contact way of assessing canopy heat stress. Normalized canopy temperature and transpiration rate were shown to correlate with water stress. Drought resistance of seedlings: Comparison between normal seedlings and partially defoliated ones, all subjected to prolonged drought, indicated that removing about half of the lowermost leaves prior to transplanting, may facilitate adjustment to the more stressful conditions in the greenhouse. Implications The results of this experimental study may lead to: (1) An improved model for a sparse canopy in a greenhouse. (2) A better ventilation design procedure utilizing improved estimates of the evaporation coefficient for different species and plant configurations. (3) A test for the stress resistance of transplants.

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Joseph, M. Heat pipe effect in porous medium. Office of Scientific and Technical Information (OSTI), dicembre 1992. http://dx.doi.org/10.2172/138712.

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