Changes In Ambient Humidity Research Articles

β‐Glucocerebrosidase Activity in the Stratum Corneum of House Sparrows following Acclimation to High and Low Humidity

Skin is an important avenue of water loss in terrestrial birds, so environmental conditions that necessitate water conservation should favor physiological mechanisms that reduce cutaneous water loss (CWL). Skin resistance to CWL is conferred by a barrier of lipid molecules located in the stratum corneum (SC), the outer layer of the epidermis. In mammals, SC barrier function depends on the conversion of cerebrosides to ceramides by the enzyme beta -glucocerebrosidase ( beta -GlcCer'ase). Avian SC contains both cerebrosides and ceramides, suggesting that observed plasticity in CWL may be mediated by changes in beta -GlcCer'ase activity and resultant SC lipid composition. We tested the hypothesis that changes in ambient humidity would alter beta -GlcCer'ase activity by acclimating house sparrows (Passer domesticus) to either dry (6.5 g H(2)O m(-3) absolute humidity) or humid (31 g H(2)O m(-3)) conditions for 5 and 21 d at 30 degrees C and then measuring beta -GlcCer'ase activity from SC homogenates. Our results provide the first characterization of beta -GlcCer'ase activity in any nonmammalian vertebrate. Relative to nonacclimated controls, both dry- and humid-acclimated sparrows had significantly elevated beta -GlcCer'ase activity at 21 d postacclimation. Across individuals, we observed negative correlations between beta -GlcCer'ase activity and both CWL and SC ceramide content. Although dry- and humid-acclimated sparrows did not differ in beta -GlcCer'ase activity, these results are consistent with our findings that both humidity treatments caused a reduction in CWL and similar changes in SC lipid composition. Our results demonstrate physiological plasticity in CWL and provide tentative support for a role of beta -GlcCer'ase in mediating this response.

ZnO Thick Film Based Opto-electronic Humidity Sensor for a Wide Range of Humidity

Sensitivity of zinc oxide film to humidity is studied using prism based opto-electronic sensor configuration. Film is deposited on the base of the prism by screen printing. The film is crystalline in nature and has micropores on its surface which is suitable for humidity sensing. The sensing mechanism, here, is the modulation in emergent light intensity with change in ambient humidity. Response of the sensor configuration is repeatable and the configuration is found to be sensitive to relative humidity (RH%) ranging from 5 to 90 RH%.

Thin Films Composed of Multiwalled Carbon Nanotubes, Gold Nanoparticles and Myoglobin for Humidity Detection at Room Temperature

Optically transparent and electrically conductive nanocomposite thin films consisting of multiwalled carbon nanotubes (MWCNTs), gold nanoparticles (GNPs) and myoglobin molecules that glue GNPs and MWCNTs together are fabricated for the first time on glass substrates from aqueous solution. The nanocomposite thin film is capable of varying its resistance, impedance or optical transmittance at room temperature in response to changes in ambient humidity. The conductometric sensitivity to relative humidity (RH) of the nanocomposite thin film is compared with those of the pure and Mb-functionalized MWCNT layers. The pure MWCNT layer shows a small increase in its resistance with increasing RH due to the effect of p-type semiconducting nanotubes present in the film. In contrast, a four times higher sensitivity to RH is observed for both the nanocomposite and Mb-functionalized MWCNT thin films. The sensitivity enhancement is attributable to swelling of the thin films induced by water absorption in the presence of Mb molecules, which increases the inter-nanotube spacing and thereby causes a further increase of the film resistance. A humidity change as low as DeltaRH=0.3 % has been readily detected by conductometry using the nanocomposite thin film.

Humidity sensor based on localized surface plasmon resonance of multilayer thin films of gold nanoparticles linked with myoglobin

Layer-by-layer self-assembled multilayer thin films of gold nanoparticles (GNPs) linked with myoglobin (Mb) show substantial sensitivity to humidity at room temperature according to measurements of localized surface plasmon resonance (LSPR) absorption that relies on the interparticle interaction present in the film. The sensor response is reversible, with response and recovery times as low as 5 s. The sensing mechanism is as follows: as the ambient humidity changes, Mb molecules change their size, making the GNP-to-GNP spacing and thereby the interparticle interaction change; the change in the interparticle interaction causes a change in the LSPR absorption of the multilayer thin film. We found that the LSPR band of the multilayer thin film was almost insensitive to both the surrounding refractive index and the adlayer thickness, rendering the multilayer-film-based humidity sensor highly immune to ambient disturbances.

Porous Nanostructured Optical Filters Rendered Insensitive to Humidity by Vapor-Phase Functionalization

Water adsorption in many porous optical coatings can cause a detrimental red-shift in the optical properties. In this study, a porous nanostructured rugate filter is fabricated using the glancing-angle deposition (GLAD) technique, and rendered insensitive to large changes in ambient humidity by post-deposition vapor-phase functionalization. A central defect mode is added to the stop band of the filter by integrating a phase shift into the sinusoidal refractive-index profile of the film. By monitoring the wavelength of the defect mode under variable humidity conditions, a six-times reduction in sensitivity to water vapor is observed upon functionalization with 3,3,3-trifluoropropyltrichlorosilane. Electrical characterization and advancing aqueous contact-angle measurements are used to verify the hydrophobic properties of the functionalized thin films.

Humidity-Sensing Inverse Opal Hydrogels

Soft material hydrogel sensors have seen increased interest recently. Most of these sensors are used in an aqueous environment. In this study, we depart from this trend and analyze the ability of a periodic hydrogel structure to respond to variations in ambient humidity through an optical change. First, a polyacrylamide inverse opal hydrogel structure was created from a colloidal crystal template. Next, this material was tested under various humidity conditions and responded to these changes by shifting its optical reflection peak noticeably within the visible wavelength range. This effect opens the doors for these materials as humidity sensors. The kinetics of the peak shifts was also observed, showing a rapid response to ambient humidity changes. Finally, the structural dimension change is compared through peak shifts, Fabry-Perot fringes of the optical cavity, and scanning electron microscopy observations.

Adaptation and Evaluation of a Personal Electronic Nose for Selective Multivapor Analysis

The evaluation of a commercial, belt-mountable “electronic nose” modified for the rapid recognition and quantification of individual solvent vapors and simple vapor mixtures at low ppm concentrations is described. Marketed under the name VaporLab® this direct-reading instrument was designed for qualitative determinations of the presence or absence of selected individual vapors and was adapted in this study for quantitative determinations of vapors and vapor-mixture components. Vapor samples are concentrated on a small adsorbent bed and then thermally desorbed for analysis by an array of four polymer-coated surface acoustic wave sensors. Tests were performed with 13 organic solvent vapors individually and in selected binary, ternary, and quaternary mixtures at concentrations ranging from 0.1 to 12 times the respective American Conference of Governmental Industrial Hygienists' (ACGIH®) threshold limit value (TLV®). Pattern recognition analyses yielded a library of response patterns to which subsequent actual and virtual (i.e., Monte-Carlo simulated) samples were compared to assess performance. Limits of detection < 0.025 × TLV are achieved (based on the most sensitive sensors) for 0.25 L of preconcentrated air samples collected over a 2-min period. Individual vapors from different functional group classes can be recognized, quantified, and discriminated from other vapors with little error, and discrimination of the components of binary mixtures is possible where the component vapor response patterns are sufficiently different. Within-class individual vapor and binary-mixture discriminations are more difficult and most ternary and higher-order mixtures could not be analyzed with acceptable accuracy. Changes in ambient humidity have no effect on responses and changes in temperature lead to well-behaved and compensable changes in responses. Tests of fluctuating concentrations demonstrate the capability for accurately tracking short-term variations in exposure. Overall, results suggest that this instrument could serve effectively as a personal exposure monitor in previously characterized occupational environments with proper revisions in design.

Influence of relative humidity on the electrical field strength to promote coalescence between two water drops

This paper describes a determination of the necessary field strengths to induce coalescence between two closely spaced water drops for a range of relative humidities. G.I. Taylor derived an expression for this, but did not consider any effect arising from changes in ambient humidity. Evaporative and other considerations restrict the results to relative humidities of 50% and above. The experimental conditions and apparatus are described together with a discussion of the resulting data. An empirical relationship describing the critical potential difference for coalescence for humidities over 50% for the experimental geometry is presented in the form of correction and scaling factors applicable to Taylor's expression.

High resolution imaging of photosynthetic activities of tissues, cells and chloroplasts in leaves

Through imaging of chlorophyll fluorescence, it is possible to produce parameterized fluorescence images that estimate the operating quantum efficiency of photosystem II (PSII) photochemistry and which can be used to reveal heterogeneous patterns of photosynthetic performance within leaves. The operating quantum efficiency of PSII photochemistry is dependent upon the effective absorption cross-section of the light-harvesting system of PSII and the photochemical capacity of PSII. The effective absorption cross-section is decreased by the process of down-regulation, which is widely thought to operate within the pigment matrices of PSII and which results in non-photochemical quenching of chlorophyll fluorescence. The photochemical capacity is non-linearly related to the proportion of PSII centres in the 'open' state and results in photochemical quenching of chlorophyll fluorescence. Examples of heterogeneity of the operating quantum efficiency of PSII photochemistry during the induction of photosynthesis in maize leaves and in the chloroplast populations of stomatal guard cells of a leaf of Tradescantia albifora are presented, together with analyses of the factors determining this heterogeneity. A comparison of the operating quantum efficiency of PSII photochemistry within guard cells and adjacent mesophyll cells of Commelina communis is also made, before and after stomatal closure through a change in ambient humidity.

Preparation of a nanostructured organoceramic and its reversible interlayer expansion

We described previously the liquid phase synthesis and characterization of a nanostructured composite from an aqueous solution containing organic polymer and inorganic ions [J. Mater. Res. 7, 2599 (1992)]. The nanocomposite, termed an organoceramic, consisted of poly(vinyl alcohol) chains intercalated between the principal layers of a hydrated calcium aluminate ceramic. A key structural feature of the organoceramic is the polymer-induced expansion of the interlayer spacing by approximately 10 Å compared to the unmodified ceramic. In this paper, we describe the synthetic scheme that favors organoceramic formation and prove the existence of intercalated polymer by observation of reversible interlayer expansion and contraction in response to changes in ambient humidity. This property is unique to the organoceramic and is not observed in the unmodified calcium aluminate ceramic.

Musical instrument strings

A string for a musical instrument comprises a thermoplastic aromatic polyetherketone and has a value of E/ρ2 which is not greater than 5×103, where E is Young's modulus of the string material measured in N/m2 and ρ is the density of the string material measured in kg/m3. Such a musical instrument string may have significantly lower internal damping than previously available strings, may show low inharmonicity, and may be unaffected by ambient humidity changes.

Properties and structure of never‐dried cotton fibers. III. Cotton fibers from bolls in early stages of growth

AbstractLike other kinds of cotton fibers already studied, American cotton fibers taken from cotton bolls immediately before and after opening show high angles of torsional rotation during ambient humidity changes. Cotton fibers taken from cotton bolls at 19 and 24 days postanthesis show remarkably higher angles of rotation and much lower dry and wet tensile strengths than the fibers taken from cotton bolls immediately before and after opening. The wet tensile strength of cotton fibers at 24 days postanthesis is higher than the dry strength like the fibers taken from bolls immediately before and after opening, but fibers at 19 days postanthesis show almost the same tensile strength in the never‐dried, dried, and rewetted states. CP/MAS 13C NMR spectroscopy reveals that the never‐dried cotton fibers at 19 days or longer postanthesis have high crystallinities. It seems that the degree of crystallinity is somewhat decreased in the dry state and restored by rewetting. The crystallinity increases with the age of growth.

Properties and Structure of Never-Dried Cotton Fibers

Field-opened cotton fibers show remarkable torsional rotation during ambient hu midity changes between about 30% and 100%. If the never-dried cotton fibers are freeze-dried or treated with NaOH (-urea) and acrylonitrile, the resulting fibers have fewer convolutions, lower torsional rotation during humidity changes, and lower spe cific gravity and higher moisture regain than air-dried fibers. There is no definite correlation between number or direction of fiber convolutions and maximum angle or direction of torsional rotation during humidity changes. The tensile strength of never-dried wet fibers is low and increases when dried; it does not decrease with rewet ting, but increases further.

A simple thermoregulated enclosure for standard cells

Four new thermoregulated enclosures, each containing four high-quality standard cells, have been built and placed in service at the BIPM. The mechanical and electrical design, and the inclusion of many practical features, make these enclosures particularly well adapted for standard cell maintenance. The largest observed day-to-day fluctuation in temperature has been 0.06 mK: the long-term stability, at present apparently limited by the sensitivity of the electronic components to changes in ambient humidity, can be better than +or-1 mK per year. After a period of stabilisation, the standard deviation of the value of the EMF of a cell about its linear drift, is no more than 10 nV. A novel feature of the mechanical design makes these enclosures particularly attractive for transfer standards of voltage.

A note on barometric pressure and behavior in Drosophila pseudoobscura.

During a study ofDrosophila mating behavior we observed unexpected changes in performance under ostensibly identical experimental conditions. We related the behavior during the 17 days of the experiment to changes in ambient humidity and barometric pressure. Humidity had no significant effect, but reduced barometric pressure was found to be associated with reduced mating activity (R2=0.29,P<0.025), accounting for close to 30% of the variation in total number of matings.

Nectar production of Epilobium angustifolium L. at different air humidities; nectar sugar in individual flowers and the optimal foraging theory.

The nectar production of Epilobium angustifolium L. was investigated at 20°C and 50%, 78% and 94% ambient humidity in the climatic test chamber. By means of permanent pipettes, freshly produced nectar was sucked off immediately after secretion, and nectar samples were also taken at 10-h and 48-h intervals to investigate the postsecretory influence of ambient humidity. Volume and sugar concentration of samples from individual flowers were measured and the sugar contained was calculated. The rate of sugar production remains constant for all ambient humidities and extraction intervals investigated; the mean value for all 180 samples is 1.55 mg sucrose equivalents/24h. Sugar concentration of secretion nectar is linearly dependent on ambient humidity over the range investigated, and nectar volume and sugar concentration change according to the theoretically expected curve for solutions with a sugar content of 1.55 mg sucrose. The response of secretion nectar to steplike changes in ambient humidity was investigated and the transient function described. The nectaries respond immediately to changes in ambient humidity. The consequences of the results for nectar production and nectar reward of individual flowers in the field and for the optimal foraging of pollinators are discussed. Discussion concentrates particularly on the following questions: what influence the variability of nectar reward in individual flowers may have on flower-visiting bumble-bees; whether these animals have the sensory capabilities to measure sugar exactly; and whether the water relations of pollinators may also influence foraging behaviour.

Nest Microclimate, Water-Vapor Conductance, and Water Loss in Heron and Tern Eggs

Abstract Rates of water loss (ṀH2O) were measured in eggs of seven species of tree-nesting Ciconiiformes and three species of ground-nesting Charadriiformes during natural incubation. Measurements of egg temperature, conductance of the egg shell to water vapor, and nest and ambient humidity allow one to calculate the difference in water-vapor pressure (ΔP) between egg and nest and between nest and ambient air. ΔP between egg and nest was significantly lower in ground-nesting species (23 torr) than in tree-nesting species (31 torr). We suggest that low ΔP in ground-nesting species was due to relatively high humidity (ca. 27 torr) in nests built on the ground compared to the humidity in loose stick nests of tree-nesting species (ca. 14 torr). Water-vapor conductance of eggs from more humid nests is relatively higher than that of eggs from less humid nests (107% and 78% of predicted values, respectively), resulting in similar fractional losses in mass for the whole incubation period in both groups of birds. (ṀH2O) was not always constant throughout incubation. We suggest that changes in (ṀH2O) may be due to changes in ambient humidity and/or egg temperature.

The Dimensional Stability of Carpets in Installations

Dimensional stability of floor coverings to.forces encountered under end-use conditions has not been investigated extensively, although problems of wrinkling and puckering of carpets in stretch installations arise frequently. Changes in ambient humidity occur over broad ranges in most buildings; consequently, carpets which are not stable to changes in ambient humidity may be susceptible to puckering. A test procedure based on a method adopted by the British Standards Institution was used to characterize a large number of carpets for dimensional stability to changes in ambient humidity. Several carpet construction characteristics—total weight, pile yarn type, gage, and stitch density—were found to have little relationship to stability to humidity change. Large differences in stability were observed among manufacturers. Tufted carpets having jute backings were found to be less stable than carpets manufactured with synthetic backings.

Variation of Stomatal Diffusive Resistance With Ambient Humidity in Sunflower (Helianthus annuus)

Experiments with sunflower were set up to supply quantitative information on the relationship between transpiration diffusive resistance and evaporative demand as affected by changes in ambient humidity. The experiments were run on whole plants with the roots in nutrient solution to ensure an adequate supply of water. Particular attention was paid to relating calculated diffusive resistance values with measured diffusion values and visual observations of the stomata. The transpiration diffusive resistance of the stomata was found to increase in a linear manner as the water vapour concentration difference between leaf and surrounding air increased. Changes in calculated diffusive resistance were paralleled by changes in the diffusion of nitrous oxide through the stomata. Visual observation showed that the stomata closed as resistance increased and vice versa. Stomata from both adaxial and abaxial surfaces of the leaf demonstrated increases in diffusive resistance with increasing evaporative demand but the response of the adaxial surface change was not always concurrent with that of the abaxial surface. Leaf water content did not change as evaporative demand was changed, reflecting the observation that uptake of water through the roots equalled the amount lost by transpiration. It was concluded that changes in diffusive resistance were directly related to the stomatal aperture and that the primary response was at the level of the stomatal apparatus. There was no evidence of stomatal control resulting from lowered tissue water content. Anomalous results may be obtained in gas exchange experiments where a constant area of leaf is sealed into a cuvette. Tests indicate that errors arise where the leaf is held too firmly.

The thermodynamics of volume change and creep

1 With some exceptions, early observers of creep of concrete assumed that time-dependent strain is due to plastic flow or viscous flow. It is now becoming understood that creep, like shrinkage, is a phenomenon depending on adsorption and desorption of water and related phenomena. Understanding shrinking and swelling is prerequisite to understanding creep. An analysis of these phenomena based on thermodynamics is especially instructive and reliable because in general it does not depend on the correctness of the model of structure adopted for the discussion. 2 Spontaneous volume change is due to a change in the balance of forces and counterforces within the specimen. It cannot be due to the removal or addition, per se, of water molecules. 3 The volume of a porous body will vary with the density of the material of which it is made. Material density will vary with hydrostatic pressure, with temperature, or with change in surface tension of the material. 4 Change of surface tension presumably affects both the inner part and the outer tension shell of particulate material, and oppositely. 5 Surface tension, which is the same as surface free energy, varies with the amount of water adsorbed, and that is a function of ambient vapor pressure at constant temperature. The change in solid surface tension can be calculated from the concomitant change in ambient humidity. 6 The volume change of the body corresponding to a given change in surface tension is the resultant of the change of the inner and outer parts, is at present indeterminate, and is in any case a small fraction of the amount of volume change to be accounted for. 7 Data on paste structure show that adsorbed water must produce disjoining pressure in the narrowest places between solid bodies, where adsorption is hindered.