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At least 217 records · Page 12Linked to original sources
PubMed2000

Remote query measurement of pressure, fluid-flow velocity, and humidity using magnetoelastic thick-film sensors.

Free-standing magnetoelastic thick-film sensors have a characteristic resonant frequency that can be determined by monitoring the magnetic flux emitted from the sensor in response to a time varying magnetic field. This property allows the sensors to be monitored remotely without the use of direct physical connections, such as wires, enabling measurement of environmental parameters from within sealed, opaque containers. In this work, we report on application of magnetoelastic sensors to measurement of atmospheric pressure, fluid-flow velocity, temperature, and mass load. Mass loading effects are demonstrated by fabrication of a remote query humidity sensor, made by coating the magnetoelastic thick film with a thin layer of solgel deposited Al2O3 that reversibly changes mass in response to humidity.

Atmospheric Pressure↗
PubMed2005

Experimental investigation on the role of water in the mechanical behavior of structural dentine.

Dentine is a porous hydrated composite structure that forms the major bulk of the human tooth. The aim of this study was to investigate the role of free water on the in-plane, mechanical strain response in dentine structure. A digital moire interferometry was used for this purpose. It was observed from this experiment that structural dentine demonstrated distinct strain gradients in the axial (perpendicular to the dentinal tubules) and lateral (parallel to the dentinal tubules) directions. The hydrated dentine displayed significant increase in strain with stress in the direction perpendicular to the dentinal tubules, and this response was characteristic of a tough material. On the contrary, the dehydrated dentine, which was dehydrated at 24 degrees C, 55% relative humidity for 72 h showed a strain response characteristic of a brittle material. The strains formed in the direction parallel to the dentinal tubules for hydrated dentine were consistent and did not vary much with increase in applied loads. Upon dehydration, the outer dentine experienced higher strains, and the difference between the outer and inner dentine became more conspicuous with increase in loads. This experiment highlights hydration-induced, distinct in-plane strain gradients in the directions perpendicular and parallel to the dentinal tubules in the dentine structure.

Dentin↗
PubMed2001

A humidity-sensitive Arabidopsis copine mutant exhibits precocious cell death and increased disease resistance.

The copines are a newly identified class of calcium-dependent, phospholipid binding proteins that are present in a wide range of organisms, including Paramecium, plants, Caenorhabditis elegans, mouse, and human. However, the biological functions of the copines are unknown. Here, we describe a humidity-sensitive copine mutant in Arabidopsis. Under nonpermissive, low-humidity conditions, the cpn1-1 mutant displayed aberrant regulation of cell death that included a lesion mimic phenotype and an accelerated hypersensitive response (HR). However, the HR in cpn1-1 showed no increase in sensitivity to low pathogen titers. Low-humidity-grown cpn1-1 mutants also exhibited morphological abnormalities, increased resistance to virulent strains of Pseudomonas syringae and Peronospora parasitica, and constitutive expression of pathogenesis-related (PR) genes. Growth of cpn1-1 under permissive, high-humidity conditions abolished the increased disease resistance, lesion mimic, and morphological mutant phenotypes but only partially alleviated the accelerated HR and constitutive PR gene expression phenotypes. The disease resistance phenotype of cpn1-1 suggests that the CPN1 gene regulates defense responses. Alternatively, the primary function of CPN1 may be the regulation of plant responses to low humidity, and the effect of the cpn1-1 mutation on disease resistance may be indirect.

Amino Acid Sequence↗
PubMed2001

Epidermal interleukin-1 alpha generation is amplified at low humidity: implications for the pathogenesis of inflammatory dermatoses.

BACKGROUND: We have previously reported that low humidity amplifies the hyperproliferative and inflammatory response to barrier disruption. Other reports suggest that epidermal interleukin (IL)-1 alpha is stimulated by various factors related to epidermal inflammation and that it may induce other proinflammatory molecules. OBJECTIVES: To evaluate the generation of IL-1 alpha in the skin of hairless mice kept under various conditions of environmental humidity. METHODS: We carried out an immunohistochemical study, and evaluated epidermal IL-1 alpha mRNA and protein levels, and release of IL-1 alpha from skin after tape stripping, in hairless mice kept under low or high humidity. RESULTS: The immunohistochemical study showed that the amount of IL-1 alpha in the epidermis was higher in animals kept in a low-humidity environment than in a high-humidity one. The epidermal IL-1 alpha mRNA and protein levels increased significantly when the animals were kept under low humidity. Moreover, the release of IL-1 alpha from skin immediately after tape stripping was significantly higher in animals kept in a low-humidity environment than in a high-humidity one. CONCLUSIONS: These results suggest that IL-1 alpha is an important factor in mediating the relationship between environmental humidity and epidermal pathology.

Animals↗
PubMed2000

Magnetoelastic sensors in combination with nanometer-scale honeycombed thin film ceramic TiO2 for remote query measurement of humidity.

Ribbonlike magnetoelastic sensors can be considered the magnetic analog of an acoustic bell; in response to an externally applied magnetic field impulse the sensors emit magnetic flux with a characteristic resonant frequency. The magnetic flux can be detected external to the test area using a pick-up coil, enabling query remote monitoring of the sensor. The characteristic resonant frequency of a magnetoelastic sensor changes in response to mass loads. [L.D. Landau and E. M. Lifshitz, Theory of Elasticity, 3rd ed. (Pergamon, New York, 1986). p. 100].Therefore, remote query chemical sensors can be fabricated by combining the magnetoelastic sensors with a mass changing, chemically responsive layer. In this work magnetoelastic sensors are coated with humidity-sensitive thin films of ceramic, nanodimensionally porous TiO2 to make remote query humidity sensors.

Biosensing Techniques↗
PubMed1996

Suppression of gravitropic response of primary roots by submergence.

Primary roots of six plant species were placed horizontally either in humid air or under water, and their growth and gravitropic responses were examined. In air, all the roots showed a normal gravitropic curvature. Under water without aeration, roots of rice (Oryza sativa L.), oat (Avena sativa L.), azuki bean (Vigna angularis Ohwi et Ohashi), and cress (Lepidium sativum L.) curved downward at almost same rate as in air, whereas the curvature of roots of maize (Zea mays L.) and pea (Pisum sativum L.) was strongly suppressed. Submergence did not cause a decrease in growth rate of these roots. When roots of maize and pea were placed horizontally under water without aeration and then rotated in three dimensions on a clinostat in air, they showed a significant curvature, suggesting that the step suppressed by submergence is not graviperception but the subsequent signal transmission or differential growth process. Constant bubbling of air through the water partly restored the gravitropic curvature of maize roots and completely restored that of pea roots. The curvature of pea roots was also partly restored by the addition of an inhibitor of ethylene biosynthesis, aminooxyacetic acid. In air, ethylene suppressed the gravitropic curvature of roots of maize and pea. Furthermore, the level of ethylene in the intercellular space of the roots was increased by submergence. These results suggest that the accumulation of ethylene in the tissue is at least partly involved in suppression of transmission of the gravity signal or of differential growth in maize and pea roots under conditions of submergence.

Aminooxyacetic Acid↗
PubMed2005

Optochemical sensor for determining ozone based on novel soluble indigo dyes immobilised in a highly permeable polymeric film.

An optochemical ozone sensor is described that has been manufactured by immobilisation of novel soluble indigo derivatives in permeable transparent polymeric films of polydimethylsiloxane-polycarbonate copolymer. From a number of investigated indigo derivatives, 4,4',7,7'-tetraalkoxyindigo 9 has been selected for optimal sensitivity and specificity of ozone detection. A linear calibration for ozone can be obtained in the range between 0.01 and 0.5 ppm. The limit of quantitation is 0.03 ppm, and the accuracy exceeds 8%. It takes about 134 s to measure the relatively low occupational exposure concentration of 0.1 ppm. A reduction of the sensor response time could be achieved through application of double-sided coated sensors instead of single-sided variants. The stability of the sensors and the effect of external parameters like relative humidity (RH), temperature and gas flow on the sensor response have been investigated. The sensor response is affected by varying the gas flow or temperature; however, humidity in the range between 0 and 90% RH does not affect sensor response. The indigo derivative 9 remained stable inside the polymeric film and no chemical reaction, crystallisation or leaching occurred during 10 months of observation. Proper choice of indicator dye and polymeric material and successful application of kinetic evaluation method for the exposure experiments determine the desired features of the sensor.

Air Pollutants↗
PubMed2002

Responses of photosynthetic electron transport in stomatal guard cells and mesophyll cells in intact leaves to light, CO2, and humidity.

High-resolution images of the chlorophyll fluorescence parameter Fq'/Fm' from attached leaves of commelina (Commelina communis) and tradescantia (Tradescantia albiflora) were used to compare the responses of photosynthetic electron transport in stomatal guard cell chloroplasts and underlying mesophyll cells to key environmental variables. Fq'/Fm' estimates the quantum efficiency of photosystem II photochemistry and provides a relative measure of the quantum efficiency of non-cyclic photosynthetic electron transport. Over a range of light intensities, values of Fq'/Fm' were 20% to 30% lower in guard cell chloroplasts than in mesophyll cells, and there was a close linear relationship between the values for the two cell types. The responses of Fq'/Fm' of guard and mesophyll cells to changes of CO2 and O2 concentration were very similar. There were similar reductions of Fq'/Fm' of guard and mesophyll cells over a wide range of CO2 concentrations when the ambient oxygen concentration was decreased from 21% to 2%, suggesting that both cell types have similar proportions of photosynthetic electron transport used by Rubisco activity. When stomata closed after a pulse of dry air, Fq'/Fm' of both guard cell and mesophyll showed the same response; with a marked decline when ambient CO2 was low, but no change when ambient CO2 was high. This indicates that photosynthetic electron transport in guard cell chloroplasts responds to internal, not ambient, CO2 concentration.

Algorithms↗
PubMed1983

Bronchoconstriction stimulated by airway cooling. Better protection with combined inhalation of terbutaline sulphate and cromolyn sodium than with either alone.

We compared the effect of inhaled terbutaline sulphate (1,000 micrograms), cromolyn sodium (20 mg), terbutaline plus cromolyn, and placebo on the response to respiratory heat loss (RHL) in 10 asthmatics in whom terbutaline alone did not completely inhibit the response to RHL. The medications were taken double-blind in random order 20 min before voluntary isocapnic hyperventilation of subfreezing air (-14 degrees C, 0% humidity) in twofold-increasing amounts. The response was expressed as the provocative dose of RHL to cause a 10 and 20% fall in forced expiratory volume in one second (FEV1). When compared with placebo, terbutaline produced bronchodilation and inhibition of the response to RHL. The degree of bronchodilation was small (mean delta FEV1, 3.9%) and did not correlate with the degree of protection. Cromolyn produced no bronchodilation and similar inhibition. The effect of terbutaline and cromolyn together was additive. We conclude that when bronchoconstriction stimulated by airway cooling is not prevented by a beta agonist or cromolyn given individually, that it will be more effectively inhibited by the 2 drugs given in combination.

Adult↗
PubMed2002

Sweating response in physically trained men to sustained handgrip exercise in mildly hyperthermic conditions.

To investigate the effects of physical training on heat loss response to sustained handgrip exercise (non-thermal factors), we compared the sweating response during isometric handgrip exercise to mild hyperthermia in physically trained and untrained subjects. Seven trained and untrained male subjects (maximal oxygen uptake 62.7 +/- 2.4 and 42.7 +/- 1.6 mL kg-1 min-1, respectively, P < 0.05) performed isometric handgrip exercises at 20, 35 and 50% maximal voluntary contraction (MVC) for 60 s. The study was conducted in a climatic chamber with a regulated ambient temperature of 35 degrees C and relative humidity of 50% to induce sweating response at rest by rising skin temperature without a marked change in internal temperature. Sublingual and mean skin temperatures (thermal factors) in both trained and untrained groups were essentially constant throughout all exercise intensities. Changes in heart rate, mean arterial blood pressure, and rating of perceived exertion with increased exercise intensity were similar in both groups. Sweating rate (SR) on the limbs (mean value of forearm and thigh) was significantly greater in the trained group than in the untrained group at 50% MVC (P < 0.05). In addition, the slopes of the relationship between increased SR and exercise intensity (% MVC) on the trunk (chest) and limbs were significantly greater in the trained group than in the untrained group (P < 0.05). Our results suggest that the sweating response caused by non-thermal factors against a background of changing thermal factors was enhanced by physical training. It is also thought that the enhanced sweating response may be especially evident on the limbs than on the trunk, such as improvement of sweating response associated with thermal factors.

Adult↗
PubMed1980

Reduced seizure control due to spoiled phenytoin capsules.

Subtherapeutic phenytoin serum levels and loss of seizure control occurred in a 31-year-old man due to decreased bioavailability of oral drug. During storage at extreme temperatures, physical changes of the phenytoin capsule resulted in altered dissolution characteristics so that only 50% dissolution occurred at 180 minutes compared with 95% in 120 minutes for control capsules. Similar changes were produced in fresh capsules within seven days at high temperature and humidity. The affected patient has metabolic responses to phenytoin that produce marked fluctuations in serum levels with changes in dose. Altered phenytoin serum concentrations may occur with minor dose changes in such patients despite good compliance.

Adult↗
PubMed1975

Avoidance response, house response, and wind responses of the sporangiophore of Phycomyces.

Avoidance response: An object placed 1 mm from the growing zone of a Phycomyces sporangiophore elicits a tropic response away from the object. The dependence of this response on the size of the object and its distance from the specimen is described, as well as measurements which exclude electric fields, electromagnetic radiation, temperature, and humidity as avoidance-mediating signals. This response is independent of the composition and surface properties of the object and of ambient light. House Response: A house of 0.5- to 10-cm diameter put over a sporangiophore elicits a transient growth response. Avoidance responses inside closed houses are slightly smaller than those in the open. Wind responses: A transverse wind elicits a tropic response into the wind, increasing with wind speed. A longitudinal wind, up or down, elicits a transient negative growth response to a step-up in wind speed, and vice versa. It is proposed that all of the effects listed involve wind sensing. This proposal is supported by measurements of aerodynamic effects of barriers and houses on random winds. The wind sensing is discussed in terms of the hypothesis that a gas is emitted by the growing zone (not water or any normal constituent of air), the concentration of which is modified by the winds and monitored by a chemical sensor. This model puts severe constraints on the physical properties of the gas.

Fungi↗
PubMed2005

Effects of two cooling strategies on thermoregulatory responses of tetraplegic athletes during repeated intermittent exercise in the heat.

Athletes with spinal cord injury (SCI), and in particular tetraplegia, have an increased risk of heat strain and consequently heat illness relative to able-bodied individuals. Strategies that reduce the heat strain during exercise in a hot environment may reduce the risk of heat illness. To test the hypotheses that precooling or cooling during intermittent sprint exercise in a heated environment would attenuate the rise in core temperature in tetraplegic athletes, eight male subjects with SCI (lesions C(5)-C(7); 2 incomplete lesions) undertook four heat stress trials (32.0 +/- 0.1 degrees C, 50 +/- 0.1% relative humidity). After assessment of baseline thermoregulatory responses at rest for 80 min, subjects performed three intermittent sprint protocols for 28 min. All trials were undertaken on an arm crank ergometer and involved a no-cooling control (Con), 20 min of precooling (Pre), or cooling during exercise (Dur). Trials were administered in a randomized order. After the intermittent sprint protocols, mean core temperature was higher during Con (37.3 +/- 0.3 degrees C) compared with Pre and Dur (36.5 +/- 0.6 degrees C and 37.0 +/- 0.5 degrees C, respectively; P < 0.01). Moreover, perceived exertion was lower during Pre (13 +/- 2; P < 0.01) and Dur (12 +/- 1; P < 0.01) compared with Con (14 +/- 2). These results suggest that both precooling and cooling during intermittent sprint exercise in the heat reduces thermal strain in tetraplegic athletes. The cooling strategies also appear to show reduced perceived exertion at equivalent time points, which may translate into improved functional capacity.

Adaptation, Physiological↗
PubMed1996

Physiological responses in nonheat acclimated horses performing treadmill exercise in cool (20 degrees C/40% RH), hot dry (30 degrees C/40% RH) and hot humid (30 degrees C/80% RH) conditions.

The aim of the present study was to determine the effect of different environmental conditions on physiological response to exercise. Four winter acclimatised, nonheat acclimated horses of different breeds were exercised at 20 degrees C/40% RH (CD), 30 degrees C/40% RH (HD) and 30 degrees C/80% RH (HH). The exercise test was designed to represent the structure and intensity of a One star Speed and Endurance test (competition exercise test [CET]). All 4 horses were able to complete the full CET (60 min + 30 min active recovery) in CD and HD, but only one horse completed the CET in HH. Two horses were stopped because of pronounced general fatigue and one because of a right atrial temperature (TRA) of 43 degrees C. Oxygen uptake on each phase was not different between CD and HD, but was higher during Phases B, C and D in HH. Mean peak TRA at the end of Phase D was 40.3 +/- 0.2, 41.6 +/- 0.4 and 42 +/- 0.3 degrees C for CD, HD and HH, respectively. Corresponding, mean peak rectal temperatures (TREC) following Phase D were 39.5 +/- 0.1, 40.6 +/- 0.1 and 41.5 +/- 0.1 degree C for CD, HD and HH, respectively. Mean time to peak TREC was 9.3 +/- 1.1 (CD), 7.3 +/- 1.8 (HD) and 10.8 +/- 2.3 (HH) min and was not significantly different between conditions (P > 0.05). Heat dissipation amounted to 83 +/- 1, 73 +/- 2 and 70 +/- 1% of heat production in CD, HD and HH, respectively. Weight loss was significantly correlated with both body surface area (CD r = 0.85; HD r = 0.87; HH r = 0.81) and bodyweight (CD r = 0.97; HD r = 0.93; HH r = 0.94). The greatest weight loss recorded was 4.6% bodyweight in one horse in HD. The mean increase in exercise intensity over the whole CET (in terms of VO2) of HD and HH and HH compared with CD was 5 +/- 3 and 14 +/- 3% higher, respectively. The exercise induced hyperthermia and the reduced capacity for heat dissipation produced partial compensatory responses in minute ventilation (VE), particularly during Phase C, when the horses were trotting. In HD, the increase in VE was achieved mainly through an increase in frequency, whilst in HH it was achieved through an increase in tidal volume (VT). The horses demonstrated a high degree of tolerance to environmental heat load, suggesting a high thermoregulatory capacity. However, for unacclimatised animals exercising in severely hot and humid conditions, performance may be limited.

Acclimatization↗
PubMed1972

Flowering and Growth Response of Peanut Plants (Arachis hypogaea L. var. Starr) at Two Levels of Relative Humidity.

Peanut plants (Arachis hypogaea L. var. Starr) grown under two different relative humidities were used in all experiments. All plants were germinated and grown to flowering in the greenhouse. At this time, one group was moved to a growth room under 95% relative humidity. After 50 days the humidity of the growth room was lowered to 50%. The second group was moved into a growth room at 50% relative humidity and after 50 days the humidity was raised to 95%.Flowering rates of plants under high humidity were greater than rates of those plants under low humidity. Flowering was stimulated by transfer from low to high humidity, and these plants set the largest percentage of pegs, maintained a high rate of ethylene production by 2-centimeter peg sections, a high growth rate of intact pegs, and they had a higher mean content of gibberellins than plants transferred from a high to a low humidity. The plants in the high to low transfer had the least number of flowers, formed the lowest percentage of pegs, had about 50% less ethylene production by 2-centimeter peg sections, and the peg growth rate declined about 50%.Maximum ethylene production occurred during initial stages of peg growth (1- to 5-millimeter sections), and gibberellin content was generally higher in these peg sections. Thus, high humidity enhanced flowering, peg formation, and peg growth rate. A causal relationship between these effects of high humidity and the growth regulator status of the developing fruit is indicated.

Journal Article↗
PubMed1990

Temporal synergism of neurotransmitter affecting drugs and seasonal reproductive responses of Indian Palm Squirrel, Funambulus pennanti.

Daily injections of L-dihydroxyphenylalanine (L-DOPA, dopamine precursor) given 12 hour after 5-hydroxytryptophan (5-HTP, serotonin precursor) eliminated annual testicular regression in seasonally breeding sub-tropical Palm Squirrel that undergoes seasonal changes in responsiveness to day-length and humidity. Other temporal relations (L-DOPA given 0, 4, 8, 16 and 20 hours after 5-HTP administration) decreased/delayed the rate of regression and maintained the reproductive system at intermediate level. 12-hour-relation maintained full breeding condition (maximum gonad and accessory sex organs) unlike control, which exhibited complete atrophy of primary and accessory sex organs. It seems likely that these injections entrained the circadian serotonergic and dopaminergic oscillations and the interaction/phase relation of these two systems through their many circadian expressions (neural/hormonal) accounts for the seasonal interpretation of environmental factors. It is suggested that response in the present study is not a pharmacological effect of drugs but temporal synergism of neural activities affected the seasonality of reproduction as only 12-hour-relation of 5-HTP and L-DOPA maintained breeding activity during post reproductive phase of annual gonad cycle in Palm Squirrel.

Animals↗