共查询到20条相似文献,搜索用时 15 毫秒
1.
This study compares the thermal ecology of male bearded dragon lizards (Pogona barbata) from south-east Queensland across two seasons: summer (1994–1995) and autumn (1995). Seasonal patterns of body temperature
(T
b) were explored in terms of changes in the physical properties of the thermal environment and thermoregulatory effort. To
quantify thermoregulatory effort, we compared behavioral and physiological variables recorded for observed lizards with those
estimated for a thermoconforming lizard. The study lizards' field T
bs varied seasonally (summer: grand daily mean (GDM) 34.6 ± 0.6°C, autumn: GDM 27.5 ± 0.3°C) as did maximum and minimum available
operative temperatures (summer: GDM T
max 42.1 ± 1.7°C, T
min 32.2 ± 1.0°C, autumn: GDM T
max 31.7 ± 1.2°C, T
min 26.4 ± 0.5°C). Interestingly, the range of temperatures that lizards selected in a gradient (selected range) did not change
seasonally. However, P. barbata thermoregulated more extensively and more accurately in summer than in autumn; lizards generally displayed behaviors affecting
heat load nonrandomly in summer and randomly in autumn, leading to the GDM of the mean deviations of lizards' field T
bs from their selected ranges being only 2.1 ± 0.5°C in summer, compared to 4.4 ± 0.5°C in autumn. This seasonal difference
was not a consequence of different heat availability in the two seasons, because the seasonally available ranges of operative
temperatures rarely precluded lizards from attaining field T
bs within their selected range, should that have been the goal. Rather, thermal microhabitat distribution and social behavior
appear to have had an important influence on seasonal levels of thermoregulatory effort.
Received: 28 April 1997 / Accepted: 29 December 1997 相似文献
2.
Daisuke Sugimori 《Applied microbiology and biotechnology》2009,82(2):351-357
To develop a microbial treatment of edible oil-contaminated wastewater, microorganisms capable of rapidly degrading edible
oil were screened. The screening study yielded a yeast coculture comprising Rhodotorula pacifica strain ST3411 and Cryptococcus laurentii strain ST3412. The coculture was able to degrade efficiently even at low contents of nitrogen ([NH4–N] = 240 mg/L) and phosphorus sources ([PO4–P] = 90 mg/L). The 24-h degradation rate of 3,000 ppm mixed oils (salad oil/lard/beef tallow, 1:1 w/w) at 20°C was 39.8% ± 9.9% (means ± standard deviations of eight replicates). The highest degradation rate was observed at
20°C and pH 8. In a scaled-up experiment, the salad oil was rapidly degraded by the coculture from 671 ± 52.0 to 143 ± 96.7 ppm
in 24 h, and the degradation rate was 79.4% ± 13.8% (means ± standard deviations of three replicates). In addition, a repetitive
degradation was observed with the cell growth by only pH adjustment without addition of the cells. 相似文献
3.
A new cultivation technique for Kappaphycus alvarezii was used in the Brazilian southeastern coast (23°02′25″ S and 43°53′39″ W), the tubular netting on floating rafts. The tubular
net technique (TN) was compared with the current method of tie–tie (TT). After 47 days, the daily growth rate (mean ± SD of TN and TT = 3.4 ± 0.7% day−1), carrageenan yield (mean ± SD of TN and TT = 36 ± 1.3%), gel strength (mean ± SD of TN and TT = 730 ± 114.5 g cm2), and
viscosity (mean ± SD of TN and TT = 350 ± 60.4 cP) did not differ between the two techniques (p > 0.05). The amount of time used to plant (TT = 30.2 ± 2.3 min and TN = 13.3 ± 3.4 min) and to harvest the seedlings (TT = 36.2 ± 2.7 min
and TN = 17.8 ± 3.7 min) were lower in TN (p < 0.001). It is concluded that TN was more effective than TT, the cultivation management (time rates used to plant and harvest
the seedlings) was 53.6% faster, no seedlings were lost, the cost was lower, and an estimated return in 1 year of nearly 20%
more than that of the TT technique. 相似文献
4.
The use of thermoregulatory models for assessing physiological responses of workers in thermally stressful situations has
been increasing because of the risks and costs related to human studies. In a previous study (Yokota et al. Eur J Appl Physiol
104:297–302, 2008), the effects of anthropometric variability on predicted physiological responses to heat stress in U.S.
Army male soldiers were evaluated. Five somatotypes were identified in U.S. Army male multivariate anthropometric distribution.
The simulated heat responses, using a thermoregulatory model, were different between somatotypes. The present study further
extends this line of research to female soldiers. Anthropometric somatotypes were identified using multivariate analysis [height,
weight, percent body fat (%BF)] and the predicted physiological responses to simulated exercise and heat stress using a thermoregulatory
model were evaluated. The simulated conditions included walking at ~3 mph (4.8 km/h) for 300 min and wearing battle dress
uniform and body armor in a 30°C, 25% relative humidity (RH) environment without solar radiation. Five major somatotypes (tall-fat,
tall-lean, average, short-lean, and short-fat), identified through multivariate analysis of anthropometric distributions,
showed different tolerance levels to simulated heat stress: lean women were predicted to maintain their core temperatures
(Tc) lower than short-fat or tall-fat women. The measured Tc of female subjects obtained from two heat studies (data1: 30°C, 32% RH, protective garments, ~225 w·m−2 walk for 90 min; data2: 32°C, 75% RH, hot weather battle dress uniform, ~378 ± 32 w·m−2 for 30 min walk/30 min rest cycles for 120 min) were utilized for validation. Validation results agreed with the findings
in this study: fat subjects tended to have higher core temperatures than medium individuals (data2) and lean subjects maintained
lower core temperatures than medium subjects (data1). 相似文献
5.
PurposeIn 2010, approximately 14.9 million babies (11.1%) were born preterm. Because preterm infants suffer from an immature thermoregulatory system they have difficulty maintaining their core body temperature at a constant level. Therefore, it is essential to maintain their temperature at, ideally, around 37 °C. For this, mathematical models can provide detailed insight into heat transfer processes and body-environment interactions for clinical applications.MethodsA new multi-node mathematical model of the thermoregulatory system of newborn infants is presented. It comprises seven compartments, one spherical and six cylindrical, which represent the head, thorax, abdomen, arms and legs, respectively. The model is customizable, i.e. it meets individual characteristics of the neonate (e.g. gestational age, postnatal age, weight and length) which play an important role in heat transfer mechanisms. The model was validated during thermal neutrality and in a transient thermal environment.ResultsDuring thermal neutrality the model accurately predicted skin and core temperatures. The difference in mean core temperature between measurements and simulations averaged 0.25±0.21 °C and that of skin temperature averaged 0.36±0.36 °C. During transient thermal conditions, our approach simulated the thermoregulatory dynamics/responses. Here, for all infants, the mean absolute error between core temperatures averaged 0.12±0.11 °C and that of skin temperatures hovered around 0.30 °C.ConclusionsThe mathematical model appears able to predict core and skin temperatures during thermal neutrality and in case of a transient thermal conditions. 相似文献
6.
Fiala D Havenith G Bröde P Kampmann B Jendritzky G 《International journal of biometeorology》2012,56(3):429-441
The UTCI-Fiala mathematical model of human temperature regulation forms the basis of the new Universal Thermal Climate Index
(UTC). Following extensive validation tests, adaptations and extensions, such as the inclusion of an adaptive clothing model,
the model was used to predict human temperature and regulatory responses for combinations of the prevailing outdoor climate
conditions. This paper provides an overview of the underlying algorithms and methods that constitute the multi-node dynamic
UTCI-Fiala model of human thermal physiology and comfort. Treated topics include modelling heat and mass transfer within the
body, numerical techniques, modelling environmental heat exchanges, thermoregulatory reactions of the central nervous system,
and perceptual responses. Other contributions of this special issue describe the validation of the UTCI-Fiala model against
measured data and the development of the adaptive clothing model for outdoor climates. 相似文献
7.
Water spray cooling during handling of feedlot cattle 总被引:1,自引:0,他引:1
Tami M. Brown-Brandl Roger A. Eigenberg John A. Nienaber 《International journal of biometeorology》2010,54(6):609-616
Activities involved in receiving or working (e.g., sorting, dehorning, castration, weighing, implanting, etc.) of feedlot
cattle cause an increase in body temperature. During hot weather the increased body temperature may disrupt normal behaviors
including eating, which can be especially detrimental to the well-being and performance of the animals. Sprinkle cooling of
animals has been successfully employed within the pen; however, added moisture to the pens’ surface increases odor generation
from the pen. A study was conducted to investigate the effectiveness of a single instance of wetting an animal within the
working facility instead of in the pen, which could potentially provide extra evaporative cooling to offset the added heat
produced by activity. Sixty-four cross-bred heifers were assigned to one of eight pens on the basis of weight. On four separate
occasions during hot conditions (average temperature 28.2 ± 1.9°C, 29.1 ± 2.0°C, 28.9 ± 3.0°C, and 26.8 ± 1.6°C; with the
temperature ranging from 22.6 to 32.5°C during the trials), the heifers were moved from their pens to and from the working
facility (a building with a scale and squeeze chute located 160–200 m away). While in the squeeze chute, four of the pens
of heifers were sprinkle cooled and the remaining four pens were worked as normal. The heifers that were treated had a body
temperature that peaked sooner (31.9 ± 0.63 min compared to 37.6 ± 0.62) with a lower peak body temperature (39.55 ± 0.03°C
compared to 39.74 ± 0.03°C), and recovered sooner (70.5 ± 2.4 min compared to 83.2 ± 2.4 min). The treated animals also had
a lower panting score, a visual assessment of level of cattle heat stress (1.1 ± 0.2 compared to 1.16 ± 0.2). The behavior
measurements that were taken did not indicate a change in behavior. It was concluded that while a single instance of wetting
an animal within the working facility did not completely offset the increase in body temperature, it was beneficial to the
animals without needing to add water to the pen surface, thus reducing the potential for odor generation. 相似文献
8.
Bröde P Fiala D Błażejczyk K Holmér I Jendritzky G Kampmann B Tinz B Havenith G 《International journal of biometeorology》2012,56(3):481-494
The Universal Thermal Climate Index (UTCI) aimed for a one-dimensional quantity adequately reflecting the human physiological
reaction to the multi-dimensionally defined actual outdoor thermal environment. The human reaction was simulated by the UTCI-Fiala
multi-node model of human thermoregulation, which was integrated with an adaptive clothing model. Following the concept of
an equivalent temperature, UTCI for a given combination of wind speed, radiation, humidity and air temperature was defined
as the air temperature of the reference environment, which according to the model produces an equivalent dynamic physiological
response. Operationalising this concept involved (1) the definition of a reference environment with 50% relative humidity
(but vapour pressure capped at 20 hPa), with calm air and radiant temperature equalling air temperature and (2) the development
of a one-dimensional representation of the multivariate model output at different exposure times. The latter was achieved
by principal component analyses showing that the linear combination of 7 parameters of thermophysiological strain (core, mean
and facial skin temperatures, sweat production, skin wettedness, skin blood flow, shivering) after 30 and 120 min exposure
time accounted for two-thirds of the total variation in the multi-dimensional dynamic physiological response. The operational
procedure was completed by a scale categorising UTCI equivalent temperature values in terms of thermal stress, and by providing
simplified routines for fast but sufficiently accurate calculation, which included look-up tables of pre-calculated UTCI values
for a grid of all relevant combinations of climate parameters and polynomial regression equations predicting UTCI over the
same grid. The analyses of the sensitivity of UTCI to humidity, radiation and wind speed showed plausible reactions in the
heat as well as in the cold, and indicate that UTCI may in this regard be universally useable in the major areas of research
and application in human biometeorology. 相似文献
9.
We describe endorhizal fungi associated with Equisetum species collected from Ellesmere Island (82°N), Axel Heiberg Island (80°N), and from sites in Yukon Territory and the Prairie
Provinces (51–67°N). Fungal colonization was assessed using a multiple quantitation microintersect method for lactofuchsin-stained
roots examined with wide-field and confocal epifluorescence microscopy. Equisetum roots host abundant and diverse endorhizal fungal associates. For 85 specimens from 14 sites, total colonization averaged
30 ± 3%, range 0–97%. Colonization rates for wide aseptate hyphae characteristic of arbuscular mycorrhizae (5 ± 1%) was significantly
less than for fine endophytes (20 ± 3%) or septate endophytes (17 ± 2%). Equisetum spp. are abundant in tundra and an important understory plant in boreal forests, where they are particularly common on burned
or disturbed sites. Endorhizal fungi associated with Equisetum may have broad ecological relevance. 相似文献
10.
G. F. Birchard C. L. Reiber 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1996,166(8):461-466
Growth and development can occur over a wide range of physical conditions in reptiles. Cardiovascular function must be critical
to this ability. However, information on cardiovascular function in developing reptiles is lacking. Previous work indicated
that in reptiles the effects of temperature on growth and metabolism are largely restricted to early development. This study
examined whether the previously observed effects of temperature and different perinatal patterns of metabolism observed in
amniotic vertebrates are correlated with cardiovascular function. Embryonic and hatchling carcass mass, heart mass and heart
rate (HR) were compared for snapping turtle eggs (Chelydra serpentina) incubated at 24 ° and 29 °C. Incubation time was shorter at 29 °C (56.2 days) than at 24 °C (71.1 days). Carcass and heart
growth showed a sigmoidal pattern at both temperatures. However, cardiac growth showed a relative decrease as incubation proceeded.
Incubation temperature significantly affected the HR pattern during development. The HR of embryos incubated at 24 °C was
constant for most of incubation (51.8±4.8 min-1). A small decrease was observed just prior to and a large decrease immediately following hatching (posthatch, 22.3±4.1 min-1). At 29 °C embryonic HR was greater than at 24 °C early in development (72.3±3 min-1). The HR steadily decreased to values equivalent to those at 24 °C. The HRs of 24 °C and 29 °C hatchlings were not different.
Cardiac output (estimated as the product of heart mass and HR) increased rapidly during early development and then slowed
dramatically at both temperatures. These data are consistent with the suggestion that temperature exerts its effects primarily
early in development. Furthermore, the changes in cardiovascular function are correlated with metabolic changes in hatching
vertebrates.
Accepted:12 June 1996 相似文献
11.
Titis Wijayanto Hitoshi Wakabayashi Joo-Young Lee Nobuko Hashiguchi Mohamed Saat Yutaka Tochihara 《International journal of biometeorology》2011,55(4):491-500
The objective of this study was to investigate thermoregulatory responses to heat in tropical (Malaysian) and temperate (Japanese)
natives, during 60 min of passive heating. Ten Japanese (mean ages: 20.8 ± 0.9 years) and ten Malaysian males (mean ages:
22.3 ± 1.6 years) with matched morphological characteristics and physical fitness participated in this study. Passive heating
was induced through leg immersion in hot water (42°C) for 60 min under conditions of 28°C air temperature and 50% RH. Local
sweat rate on the forehead and thigh were significantly lower in Malaysians during leg immersion, but no significant differences
in total sweat rate were observed between Malaysians (86.3 ± 11.8 g m−2 h−1) and Japanese (83.2 ± 6.4 g m−2 h−1) after leg immersion. In addition, Malaysians displayed a smaller rise in rectal temperature (0.3 ± 0.1°C) than Japanese
(0.7 ± 0.1°C) during leg immersion, with a greater increase in hand skin temperature. Skin blood flow was significantly lower
on the forehead and forearm in Malaysians during leg immersion. No significant different in mean skin temperature during leg
immersion was observed between the two groups. These findings indicated that regional differences in body sweating distribution
might exist between Malaysians and Japanese during heat exposure, with more uniform distribution of local sweat rate over
the whole body among tropical Malaysians. Altogether, Malaysians appear to display enhanced efficiency of thermal sweating
and thermoregulatory responses in dissipating heat loss during heat loading. Thermoregulatory differences between tropical
and temperate natives in this study can be interpreted as a result of heat adaptations to physiological function. 相似文献
12.
Kawanami S Horie S Inoue J Yamashita M 《International journal of biometeorology》2012,56(6):1025-1031
Workers working in hot or cold environments are at risk for heat stroke and hypothermia. In Japan, 1718 people including 47 workers died of heat stroke in 2010 (Ministry of Health Labour and Welfare, Japan 2011). While the American Conference of Governmental Industrial Hygienists (ACGIH) recommendation lists the abnormal core temperature of workers as a criterion for halting work, no method has been established for reliably measuring core temperatures at workplaces. ISO 9886 (Ergonomics-evaluation of thermal strain by physiological measurements. ISO copyright office, Geneva, pp 3–14; 2004) recognizes urine temperature as an index of core temperature only at normal temperature. In this study we ascertained whether or not urine temperature could serve as an index for core temperature at temperatures above and below the ISO range. We measured urine temperature of 31 subjects (29.8 ± 11.9 years) using a thermocouple sensor placed in the toilet bowl at ambient temperature settings of 40, 20, and 5˚C, and compared them with rectal temperature. At all ambient temperature settings, urine temperature correlated closely with rectal temperature exhibiting small mean bias. Urine temperature changed in a synchronized manner with rectal temperature at 40˚C. A Bland and Altman analysis showed that the limits of agreement (mean bias ± 2SD) between rectal and urine temperatures were −0.39 to +0.15˚C at 40˚C (95%CI −0.44 to +0.20˚C) and −0.79 to +0.29˚C at 5˚C (−0.89 to +0.39˚C). Hence, urine temperature as measured by the present method is a practical surrogate index for rectal temperature and represents a highly reliable biological monitoring index for assessing hot and cold stresses of workers at actual workplaces. 相似文献
13.
M. Giurfa G. Zaccardi M. Vorobyev 《Journal of comparative physiology. A, Neuroethology, sensory, neural, and behavioral physiology》1999,185(6):591-600
Honeybees Apis mellifera detect coloured targets presented to the frontal region of their compound eyes using their colour vision system at larger
visual angles (α > 15°), and an achromatic visual system based on the long-wave photoreceptor type at smaller visual angles
(5° < α < 15°). Here we examine the capability of the dorsal, ventral and frontal regions of the eye for colour detection.
The minimum visual angle αmin at which the bees detect a stimulus providing both chromatic contrast and receptor-specific contrasts to the three receptor
types varies for the different regions of the eye: 7.1 ± 0.5° for the ventral region, 8.2 ± 0.6° for the dorsal region and
4.0 ± 0.5° for the frontal region. Flight trajectories show that when the target was presented in the horizontal plane, bees
used only the ventral region of their eyes to make their choices. When the targets appeared dorsally, bees used the frontodorsal
region. This finding suggests that pure dorsal detection of coloured targets is difficult in this context. Furthermore, αmin in the ventral plane depends on receptor-specific contrasts. The absence of S-receptor contrast does not affect the performance
(αmin = 5.9 ± 0.5°), whilst the absence of M- and L-receptor contrast significantly impairs the detection task. Minimal visual
angles of 10.3 ± 0.9° and 17.6 ± 3°, respectively, are obtained in these cases. Thus, as for many visual tasks, the compound
eye of the honeybee shows a regionalisation of colour detection that might be related to peripheral or central specialisations.
Accepted: 28 September 1999 相似文献
14.
People adapt to thermal environments, such as the changing seasons, predominantly by controlling the amount of clothing insulation, usually in the form of the clothing that they wear. The aim of this study was to determine the actual daily clothing insulation on sedentary human subjects across the seasons. Thirteen females and seven males participated in experiments from January to December in a thermal chamber. Adjacent months were grouped in pairs to give six environmental conditions: (1) January/February = 5°C; (2) March/April = 14°C; (3) May/June = 25°C; (4) July/August = 29°C; (5) September/October = 23°C; (6) November/December = 8°C. Humidity(45 ± 5%) and air velocity(0.14 ± 0.01 m/s) were constant across all six experimental conditions. Participants put on their own clothing that allowed them to achieve thermal comfort for each air temperature, and sat for 60 min (1Met). The clothing insulation (clo) required by these participants had a significant relationship with air temperature: insulation was reduced as air temperature increased. The range of clothing insulation for each condition was 1.87–3.14 clo at 5°C(Jan/Feb), 1.62–2.63 clo at 14°C(Mar/Apr), 0.87–1.59 clo at 25°C(May/Jun), 0.4–1.01 clo at 29°C(Jul/Aug), 0.92–1.81 clo at 23°C (Sept/Oct), and 2.12–3.09 clo at 8°C(Nov/Dec) for females, and 1.84–2.90 clo at 5°C, 1.52–1.98 clo at 14°C, 1.04–1.23 clo at 25°C, 0.51–1.30 clo at 29°C, 0.82–1.45 clo at 23°C and 1.96–3.53 clo at 8°C for males. The hypothesis was that thermal insulation of free living clothing worn by sedentary Korean people would vary across seasons. For Korean people, a comfortable air temperature with clothing insulation of 1 clo was approximately 27°C. This is greater than the typical comfort temperature for 1 clo. It was also found that women clearly increased their clothing insulation level of their clothing as winter approached but did not decrease it by the same amount when spring came. 相似文献
15.
Maple sap, an abundant natural product especially in Canada, is rich in sucrose and thus may represent an ideal renewable
feedstock for the production of a wide variety of value-added products. In the present study, maple sap or sucrose was employed
as a carbon source to Alcaligenes latus for the production of poly-β-hydroxybutyrate (PHB). In shake flasks, the biomass obtained from both the sap and sucrose were
4.4 ± 0.5 and 2.9 ± 0.3 g/L, and the PHB contents were 77.6 ± 1.5 and 74.1 ± 2.0%, respectively. Subsequent batch fermentation
(10 L sap) resulted in the formation of 4.2 ± 0.3 g/L biomass and a PHB content of 77.0 ± 2.6%. The number average molecular
weights of the PHB produced by A. latus from maple sap and pure sucrose media were 300 ± 66 × 103 and 313 ± 104 × 103 g/mol, respectively. Near-infrared, 1H magnetic resonance imaging (MRI), and 13C-MRI spectra of the microbially produced PHB completely matched those obtained with a reference material of poly[(R)-3-hydroxybutyric
acid]. The polymer was found to be optically active with [α]25
D equaled to −7.87 in chloroform. The melting point (177.0°C) and enthalpy of fusion (77.2 J/g) of the polymer were also in
line with those reported, i.e., 177°C and 81 J/g, respectively. 相似文献
16.
C. E. Crocker J. J. Cech Jr. 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》1998,168(1):50-60
The effect of environmental hypercapnia on respiratory and acid-base variables was studied in white sturgeon, Acipenser transmontanus. Blood PCO2, PO2, pH, hemoglobin concentration, and plasma lactate, glucose, catecholamines and cortisol were measured first under normocapnia
(water PCO2 < 0.5 Torr, 1 Torr = 133.32 Pa), then under hypercapnia (25–35 Torr) and a final return to normocapnia at 19 ± 0.5 °C. Acute
(≤ 2h) hypercapnia significantly increased arterial PCO2 (8-fold increase), ventilation frequency (2-fold increase), plasma HCO3
− (2.3-fold) and decreased arterial pH (to 7.15 ± 0.02). After 24 h, norepinephrine, epinephrine and cortisol, were significantly
increased, and arterial pH reached its nadir (7.10 ± 0.03). During the 72- and 96-h-periods, arterial PCO2 (24 ± 4.4 Torr) and ventilatory frequency (105 ± 5 breaths min−1) stabilized, HCO3
− reached its apparent maximum (23.6 ± 0.0 mmol−1), glucose decreased by 32%, and pH increased significantly to 7.31 + 0.03. The return to normocapnia completely restored
arterial PCO2 (2.5 ± 0.14 Torr), HCO3
− (7.4 ± 0.59 mmol · l−1), ventilation frequency (71 ± 7 breaths · min−1), and pH (7.75 ± 0.04). Overall, hypercapnia produced a respiratory acidosis, hyperventilation, a transient norepinephrine
“spike”, and increased plasma catecholamines, cortisol, and arterial PO2. The respiratory acidosis was only partially compensated (35% pH restoration) 96 h after the onset of hypercapnia and resulted
in a significantly decreased blood-O2 affinity (Bohr effect), as determined by construction of in vitro blood O2 equilibrium curves at 15 °C and 20 °C. Prolonged exposure to hypercapnia may lead to acid-base disturbances and negatively
affect growth of white sturgeon.
Accepted: 17 August 1997 相似文献
17.
Reed JZ Chambers C Hunter CJ Lockyer C Kastelein R Fedak MA Boutilier RG 《Journal of comparative physiology. B, Biochemical, systemic, and environmental physiology》2000,170(1):1-10
The respiratory physiology, heart rates and metabolic rates of two captive juvenile male harbour porpoises (both 28 kg) were
measured using a rapid-response respiratory gas analysis system in the laboratory. Breath-hold durations in the laboratory
(12 ± 0.3 s, mean ± SEM) were shorter than field observations, although a few breath-holds of over 40 s were recorded. The
mean percentage time spent submerged was 89 ± 0.4%. Relative to similarly-sized terrestrial mammals, the respiratory frequency
was low (4.9 ± 0.19 breaths · min−1) but with high tidal volumes (1.1 ± 0.01 l), enabling a comparatively high minute rate of gas exchange. Oxygen consumption
under these experimental conditions (247 ± 13.8 ml O2 · min−1) was 1.9-fold higher than predicted by standard scaling relations. These data together with an estimate of the total oxygen
stores predicted an aerobic dive limit of 5.4 min. The peak end-tidal O2 values were related to the length of the previous breath-hold, demonstrating the increased oxygen uptake from the lung for
the longer dives. Blood oxygen capacity was 23.5 ± 1.0 ml · 100 ml−1, and the oxygen affinity was high, enabling rapid oxygen loading during ventilation.
Accepted: 11 August 1999 相似文献
18.
Physical properties (roughness, gloss, mechanical, surface topography and adhesive) of a bioadhesive film for the transdermal
delivery of drugs and its interactions with a skin model surface were studied. Roughness is a measurement of the small-scale
variations in the height of a physical surface. No significant differences in Ra between the “x” and “y” dimensions for both the skin model and patch were detected, due to uniformity in their production. Scanning electron microscope
pictures showed small particles projected from the film. Those particles resulted in increasing roughness and surface area.
For the patch, gloss values measured at 20° were 6.0 ± 0.9 and at 60°, 32.2 ± 2.2 gloss units, respectively, indicating a
semi-gloss material. Concerning the mechanical properties, the tensile strength of the film resulted four- to sevenfold greater
than the peel force from the model skin used, indicating the suitability of the film for skin application. The adhesion to
skin model depended on the amount of water used for film application and on the elapsed time between film application and
removal. Finally, the model skin that was invented by Charkoudian can be used as an alternative to costly and highly variable
human skin substrates since it possesses human topography. 相似文献
19.
This paper proposed a multi-node human thermal model to predict human thermal responses in hot environments. The model was extended based on the Tanabe's work by considering the effects of high temperature on heat production, blood flow rate, and heat exchange coefficients. Five healthy men dressed in shorts were exposed in thermal neutral (29 °C) and high temperature (45 °C) environments. The rectal temperatures and skin temperatures of seven human body segments were continuously measured during the experiment. Validation of this model was conducted with experimental data. The results showed that the current model could accurately predict the skin and core temperatures in terms of the tendency and absolute values. In the human body segments expect calf and trunk, the temperature differences between the experimental data and the predicted results in high temperature environment were smaller than those in the thermally neutral environment conditions. The extended model was proved to be capable of predicting accurately human physiological responses in hot environments. 相似文献
20.
Stem respiration of ponderosa pines grown in contrasting climates: implications for global climate change 总被引:7,自引:0,他引:7
We examined the effects of climate and allocation patterns on stem respiration in ponderosa pine (Pinus ponderosa) growing on identical substrate in the cool, moist Sierra Nevada mountains and the warm, dry, Great Basin Desert. These environments
are representative of current climatic conditions and those predicted to accompany a doubling of atmospheric CO2, respectively, throughout the range of many western north American conifers. A previous study found that trees growing in
the desert allocate proportionally more biomass to sapwood and less to leaf area than montane trees. We tested the hypothesis
that respiration rates of sapwood are lower in desert trees than in montane trees due to reduced stem maintenance respiration
(physiological acclimation) or reduced construction cost of stem tissue (structural acclimation). Maintenance respiration
per unit sapwood volume at 15°C did not differ between populations (desert: 6.39 ± 1.14 SE μmol m−3 s−1, montane: 6.54 ± 1.13 SE μmol m−3 s−1, P = 0.71) and declined with increasing stem diameter (P = 0.001). The temperature coefficient of respiration (Q
10) varied seasonally within both environments (P = 0.05). Construction cost of stem sapwood was the same in both environments (desert: 1.46 ± 0.009 SE g glucose g−1 sapwood, montane: 1.48 ± 0.009 SE glucose g−1 sapwood, P = 0.14). Annual construction respiration calculated from construction cost, percent carbon and relative growth rate was greater
in montane populations due to higher growth rates. These data provide no evidence of respiratory acclimation by desert trees.
Estimated yearly stem maintenance respiration was greater in large desert trees than in large montane trees because of higher
temperatures in the desert and because of increased allocation of biomass to sapwood. By analogy, these data suggest that
under predicted increases in temperature and aridity, potential increases in aboveground carbon gain due to enhanced photosynthetic
rates may be partially offset by increases in maintenance respiration in large trees growing in CO2-enriched atmospheres.
Received: 4 November 1996 / Accepted: 23 January 1997 相似文献