The epicuticular wax layer prevents excessive loss of body water in most insects. The innermost layer of the wax is an oriented monolayer, offering the greatest resistance to the movement of water molecules across the cuticle. Several workers have shown that this oriented monolayer undergoes phase transition at a certain temperature and that the loss of water increases rapidly above this temperature which is now known as transition temperature. Other researchers deny a sharply defined transition point and claim that loss of water increases exponentially with temperature. The controversy includes Corixids. This work was carried out in an attempt to study the water relations of Cenocorixa expleta (Hungerford) in dry air. An apparatus was built to pass dry air over a single insect at constant speed and temperature. Measurements were made of the evaporation rate and the temperature of the cuticle, using copper-constantan thermo-couples made from 47 s.w.g. wires. In one series of experiments, the insects were pre-treated by immersion in water or surfactant solutions of various temperatures before their evaporation rates were measured in dry air of 20 G. Adult C. expleta have a transition point which lies near 30 C but composite evaporation/temperature curves do not show it. The evaporation rates in dry air are slightly temperature-dependent below, and highly temperature-dependent above transition. When caused by high temperature air, transition appears to be reversible: the insects regain waterproofness at approximately 25 C. To prove or disprove the existence of a transition point it is necessary to measure the evaporation rates of an individual insect over the entire temperature range. Phase transition and loss of waterproofness can also be caused by water of 30 C to 35 C. In this case the effect is irreversible. Detergent solutions of sub-transition temperatures remove a small fraction of waterproofing agent, possibly the non-oriented portion of the wax layer. The presence of the transition phenomenon in G. expleta, i. e., the fact that these insects lose their waterproofing, suddenly at approximately 30 G, and the fact that they lose this waterproofing permanently if it is caused by high temperature water, may limit their successful survival in small water bodies and thus their distribution. / Land and Food Systems, Faculty of / Graduate

The purpose of this study was to determine the: 1) knowledge, attitudes, and behaviors toward hydration and fluid replacement among collegiate football players at an NCAA Division I University, overall , and the relationship, if any, by position on the team, number of seasons played, and previous nutrition education; 2) relationship between the athletes’ hydration knowledge, attitudes and behaviors; 3) current sources of nutrition information likely to be used by the football players; and 4) players’ perception of the adequacy of, and barriers to, their fluid intake before, during, and after exercise. The players’ mean Hydration Knowledge Score was 14.2 ± 1.4 out of 17 (83.5%). Common misconceptions included: 60% thought water, rather than sports drinks, should be consumed when exercising for more than one hour; 54% did not believe sports drinks are better at restoring muscle glycogen than water; 47% believed salt tablets kept players from getting dehydrated; and 42% indicated thirst is the best indicator of dehydration. No differences were detected by number of seasons, position or previous nutrition education. / Department of Family and Consumer Sciences

Thesis (M.S.)--University of Alabama at Birmingham, 2008. / Additional advisors: Louis B. Nabors, James M. Markert, Donald B. Twieg. Description based on contents viewed July 8, 2009; title from PDF t.p. Includes bibliographical references (p. 73-79).

Thesis (M. Sc.)--Brock University, 2006. / Includes bibliographical references.

Thesis (M.S.)--Brock University, 2006. / Includes bibliographical references (leaves 88-111). Also available online (PDF file) by a subscription to the set or by purchasing the individual file.

The actual fluid intake of forty (40) residents of a nursing home was determined by an analysis of detailed three-day food and fluid intake records obtained by direct observation. Intake was compared to an established standard to determine the adequacy of fluid intake for this population. Subjects were grouped in two groups according to age (<85 years and >85 years) to determine whether age influenced fluid intake. In addition, data such as number and frequency of medications and dependency factors, such as ability to feed self, ability to communicate, ability to move and ability to make decisions, were collected and correlated.There was no significant difference between actual fluid intake and required fluid intake for the population a whole and for the two age groups. However, there were individuals who had very low fluid intakes suggesting other factors which influence fluid intake. There were positive correlations between fluid obtained from non meal feedings and frequency of medication delivery and number of medications delivered during a 24 hour period. In addition, there were positive correlations among the dependency factors. There was no correlation among any of the dependency factors and fluid intake for the group as a whole or for the two age groups.It was concluded from this study that this population of elderly nursing home residents obtained adequate fluid. Medication frequency and number appeared to influence the amount of fluid that a resident might obtain during non meal feedings. However, as a subject became more dependent, this factor did not affect the fluid intake of this population. / Department of Home Economics

Thesis (M. Sc.)--Carleton University, 2003. / Includes bibliographical references (p. 90-98). Also available in electronic format on the Internet.

Thesis (doctoral)--University of Jyväskylä, 1994. / Thesis is based on six separately published papers which are reprinted at end. Includes bibliographical references.

Thesis (doctoral)--University of Jyväskylä, 1994. / Thesis is based on six separately published papers which are reprinted at end. Includes bibliographical references.

South African forestry workers are predisposed to dehydration due to the heavy physical activity they perform in impermeable regulation safety clothing in hot and often humid environments where the availability of a variety of suitable fluids at reasonable temperatures is limited. As dehydration reduces both physical and mental capacity the potential consequences include decreased productivity and an increased risk for injury. The aim of this cross sectional observational study was to determine the prevalence and severity of dehydration in rural forestry workers in both winter (minimum and maximum daily temperatures 3-22°C) and autumn (minimum and maximum daily temperatures 14-27°C). The convenience sample included 103 workers in autumn (Nelspruit, n=64 males, n=39 females, mean age 37.32 years, mean BMI 22.3 kg/m2) and 79 in winter (Richmond, n=68 males, n=11 females, mean age 25.85 years, mean BMI 22.2 kg/m2). The sample included chainsaw operators, chainsaw operator assistants, debarkers and stackers. The risk of heat illness was moderate in Nelspruit (average daily temperature 21.1°C 67% rh) and low in Richmond (average daily temperature 17.0°C 39% rh). The prevalence of dehydration was determined by urine specific gravity (USG) measurements. Percent loss of body weight in the course of the shift was used to determine the severity of dehydration. In Nelspruit 43% (n=43) and in Richmond 47% (n=37) of the forestry workers arrived at work dehydrated (USG>1.020 g/ml). Pre break this had increased to 49% (n=49) in Nelspruit and 55% (n=33) in Richmond. By the end of shift the number of dehydrated forestry workers had significantly increased to 64% (n=64, p≤0.001) in Nelspruit and 63% (n=42, p=0.043) in Richmond. A minimum of 21% (n=2) in Nelspruit and 23% (n=15) in Richmond of the forestry workers had lost more than 2% of their body weight which could significantly decrease work capacity and work output as well as mental and cognitive ability. Dehydration was not related to season (winter/autumn), gender or job category. In Nelspruit 23% (n=23) and in Richmond 13% (n=10) arrived at work overhydrated (USG<1.013 g/ml). Pre break this had decreased to 14% (n=14) in Nelspruit and 10% (n=6) in Richmond. By the end of shift 4% (n=4) in Nelspruit and 2% (n=1) in Richmond had remained overhydrated and without correcting for fluid and food intake, 5% (n=5) had gained over 2% of their body weight in Nelspruit while none had gained weight in Richmond. Overhydration was not related to season (winter/autumn), gender or job category. Physical symptoms at the end of shift included tiredness (24%), toothache (13%) and headaches (10%) although these did not correlate to end of shift USG readings (p=0.221). The fluid requirements for male workers (n=8) who did not eat or drink across the shift was 439 ml per hour. The contractors were unaware of how much fluid should be supplied to workers and how much fluid they actually supplied. The only fluid provided by the contractors was water at the ambient air temperature which was the main source of fluid for the majority. Some forestry workers brought a limited variety of other fluids including amahewu, tea and cold drinks to work. At least 40% of the work force investigated, started their shift already compromised to work to capacity (USG>1.020 g/ml). The prevalence of dehydration had increased by the break emphasizing the need to begin drinking early on in the shift. The majority of forestry workers were dehydrated at the end of the shift. A significant proportion was dehydrated to the extent (>2%) that both work capacity and mental ability would be significantly compromised. A select group of forestry workers were drinking excessive amounts of fluid and were therefore susceptible to potentially fatal dilutional hyponatremia especially as water was the primary source of fluid. Dehydration in both autumn and winter was identified as being a significant but preventable risk. As a consequence of overhydration, a small group of forestry workers may be susceptible to dilutional hyponatremia. Fluid intake guidelines for males of 450 ml per hour appeared to be safe and were within the recommendations of the American College of Sports Medicine. Fluid guidelines for females need investigation. / Thesis (M.Sc.)-University of KwaZulu-Natal, Pietermaritzburg, 2008.