Chamber Relative Humidity Research Articles

A Study on the Reduction of Gossypol Levels by Mixed Culture Solid Substrate Fermentation of Cottonseed Meal

The objective of this work was to study the effect of mixed culture solid substrate fermentation of C. tropicalis ZD-3 with A. niger ZD-8 on detoxification of cottonseed meal (CSM), and to investigate the effect of fermentation period, proportion of CSM in substrate, sodium carbonate, minerals and heat treatment on the reduction of free gossypol levels during mixed culture solid substrate fermentation of CSM. Experiment 1: Three groups of disinfected CSM substrate were incubated for 48 h after inoculation with either of the fungi C. tropicalis ZD-3, A. niger ZD-8 or mixed culture (C. tropicalis ZD-3 with A. niger ZD-8). One non-inoculated group was used as the control. Levels of initial and final free gossypol (FG), CP and in vitro CP digestibility were assayed. The results indicated that mixed culture fermentation was far more effective than single strain fermentation, which not only had higher detoxification rate, but also had higher CP content and in vitro digestibility. Experiment 2: CSM substrates were treated according to experimental variables including fermentation period, proportion of CSM in substrate, sodium carbonate, minerals and heat treatment, Then, the treated CSM substrates were inoculated with mixed culture (C. tropicalis ZD-3 with A. niger ZD-8) and incubated at 30°C for 36 h in a 95% relative humidity chamber. After fermentation ended, FG and CP content of fermented CSM substrate was assayed. The results showed that the appropriate fermentation period was 36 h, and the optimal proportion of CSM in substrate was 70%. Addition of sodium carbonate to CSM substrate was beneficial for fermentative detoxification. Heat treatment could facilitate fermentative detoxification, and

Constant relative humidity chambers using phosphoric acid for controlled desiccation of small recalcitrant biological samples

For successful storage and cryopreservation of recalcitrant (short-lived or desiccation-sensitive) plant seeds, excised seed embryos or pollen, precise control of water content and/or slow drying rates are often crucial. To realize such controlled desiccation, we developed simple and safe constant relative humidity (RH) chambers using a single compound, phosphoric acid (PA). It consisted of a bowl of PA-water solution placed in a hermetically sealed box. With this apparatus, RH ranges of 4-88% were obtained from 100-10% PA solutions, respectively. Similar RH-PA concentration profiles were obtained at 24 and 7°C. Constant RH was ensured at a constant temperature as temperature fluctuations resulted in mirror-image RH oscillations within the chamber. When the temperature was greatly changed within 5-30°C ranges, the chamber regained the same equilibrium RH in 4-8 h. Using this system, typical recalcitrant winter rye pollen was successfully stored under RH50% at 7°C for 10 days. Alginate beads, irrespective of sucrose concentrations (0.7-1.2 M), were desiccated to equilibrium water contents of 11.5-32% (fresh weight basis) under constant RH of 27-78% at 24°C. This system is simple, economical and safer than conventional RH chamber systems using saturated solutions or sulfuric acid. It allows constant RH available at various temperatures and is useful for controlled desiccation of small recalcitrant genetic or in vitro resources for dry-cold or cryogenic storage.

Relative humidity is a key factor in the acclimation of the stomatal response to CO(2).

Previous work has shown that stomata of growth chamber-grown Vicia faba leaves have an enhanced CO2 response when compared with stomata of greenhouse-grown plants. This guard cell response to CO2 acclimatizes to the environmental conditions on the transfer of plants between the two environments. In the present study, air relative humidity is identified as a key environmental factor mediating the changes in stomatal sensitivity to CO2. In the greenhouse environment, elevation of relative humidity to growth chamber levels resulted in an enhanced CO2 response, whereas a reduction in the light level to that comparable to growth chamber conditions had no effect on stomatal CO2 sensitivity. The transfer of plants between humidified and normal greenhouse conditions resulted in an acclimation response with a time-course matching that previously obtained in transfers of plants between greenhouse and growth chamber environments. The high stomatal sensitivity to CO2 of growth chamber-grown plants could be reduced by lowering growth chamber relative humidity and then restored with its characteristic acclimation time-course by an elevation of relative humidity. Leaf temperature was unchanged during this restoration, eliminating it as a primary factor in the acclimation response. Humidity regulation of stomatal CO2 sensitivity could function as a signal for leaves inside dense foliage canopies, promoting stomatal opening under low light, low CO2 conditions.

Study on effect of coupling agents on underfill material in flip chip packaging

Coupling agents are widely used in order to improve the adhesion property of underfill. In this study, three different silane coupling agents, two titanate coupling agents, and one zirconate coupling agent were added into an epoxy underfill material. Their effects on the flow behavior and curing profile of the epoxy underfill were studied with a rheometer and a differential scanning calorimeter, respectively. The thermal stability of the cured underfill material was studied with a thermogravimetric analyzer. A thermal mechanical analyzer and a dynamic mechanical analyzer were used to measure the coefficient of thermal expansion, the glass transition temperature (T/sub g/), and the storage modulus (E'). In addition, the adhesion of the underfill on benzocyclobutene passivated silicon die and polyimide passivated silicon die was measured through die shear test. The effects of aging in an 85/spl deg/C/85% relative humidity chamber were also studied through moisture absorption test and die shear test.

Pigment dispersion degree and its evolution in storage

The current size of individual particles in most pigments is usually below 1μm; this ensures powerful forces of attraction causing the particles to cling to one another forming aggregates. If pigment dispersion stability is not appropriate, particles join again and form flocculates. It is important to know the initial degree of dispersion, its evolution during coating storage and the influence on its dry film anticorrosive properties. Several anticorrosive coatings were formulated starting from an epoxy resin as binder, tin tannates as inhibitor and a red iron oxide‐micronised talc mixture as inert pigment. Variables studied were pigment dispersion time and coating ageing time in storage. The degree of dispersion was determined by optical photomicroscopy to establish the shape and size of associated particles present in the system. The flow properties of anticorrosive coatings due to the different dispersion degree were evaluated through rheological tests. Coating film behaviour was also assessed for several dispersion times and ageing periods in laboratory, employing a salt spray (fog) cabinet and a 100 per cent relative humidity chamber.

ACUTE INHALATION TOXICITY STUDIES OF n -BUTYL ACETATE

Aerosolized n -butyl acetate (n -BA) was reported to have an LC50 value of approximately 160 ppm in a study conducted by 3M at NOTOX. Six follow-up studies at three laboratories (BASF, BRRC, NOTOX) were conducted in an attempt to reproduce this value. Two other LC50 values for aerosolized n -BA were generated (390 and 1096 ppm). However, 4 studies did not result in any lethalities from aerosolized n -BA at concentrations of 415.5, 798, 1033.5, 1411, 1442, 1517, 1575, 4429.2, 5082, and 9312 ppm. Thus, no consistent LC50 value for aerosolized n -BA was determined. Statically saturated and dynamically evaporated n -BA studies were conducted to investigate whether the aerosolization process of n -BA had an impact on the toxicity. No deaths were observed from animals exposed to statically generated n -BA vapor at a concentration of 6867 ppm and dynamically evaporated n -BA vapor at concentrations of 2027, 3013, 4429.2, and 6335 ppm. Exposures of aerosolized n-BA from old and current productions of n -BA were monitored for small particles (minimum size 0.01 m) to determine any effect the presence of these particles might have on toxicity. No differences in the particle concentrations between the old and current productions of n -BA were noted, and particle size/concentration appeared unrelated to toxicity. Two other parameters were investigated: Relative humidity was elevated (100%), and different atomizers were used to investigate the particle effect on the toxicity of aerosolized n -BA. No lethalities were observed using the different productions of n -BA, elevated relative humidity, different atomizers, or different air sources for the aerosolization of n -BA. Findings in the 3M/NOTOX study not observed in any other studies were (1) low chamber relative humidity, (2) brief times to death of the animals, and (3) histopathological finding of vesicular emphysema. Occupational exposure to n BA does not result from the usage of aerosolized pure n -BA, but rather mixtures con- taining n -BA in which n -BA is released as a vapor. Aerosolized n -BA was not found at the workers' breathing zone in a furniture paint spray study. The animal vapor data suggest only low to moderate toxicity at high concentrations. Thus, this anomaly of low and variable LC50 values of aerosolized pure n -BA does not appear to be of great concern in occupational settings. Consequently, the American Conference of Governmental Industrial Hygienists (ACGIH) in 1996 maintained a threshold limit value (TLV) value of 150 ppm.

Growth evaluation of fungi ( Penicillium and Aspergillus spp.) on ceiling tiles

The potential for fungal ( Penicillium and Aspergillus spp.) growth on four different types of ceiling tiles was evaluated in static chambers. It was found that even new ceiling tiles could support fungal growth when at equilibrium with a relative humidity (RH) as low as 85% and corresponding moisture content (MC) greater than 2.2%. Used ceiling tiles appeared to be more susceptible to fungal growth than new ones. In the 70% RH chamber with wetted tiles under slow-drying, non-equilibrium conditions, fungi could still proliferate as long as the moisture level in the ceiling tiles was adequate. Fungal growth could be limited if the wetted ceiling tiles were dried quickly and thoroughly.

Automated Temperature and Relative Humidity Calibrations for the Oklahoma Mesonetwork

A low-cost (under $12,000), fully automated, relative humidity calibration chamber capable of testing up to six probes simultaneously over a range of humidifies from 5% to approximately 95% is designed, constructed, and tested for use by the Oklahoma mesonetwork. In addition, a low-cost (under $4,000) temperature calibration chamber is developed that can test seven probes over the entire meteorological range of interest.(≈ −30° to +50°C). These procedures were designed and developed for the Vaisala HMP 35C temperature and relative humidity probe but are applicable to any similar instrument. The initial implementation results are presented. The relative humidity calibration uses an optical condensation dewpoint hygrometer as the laboratory reference. Two precision resistance temperature detectors are used in the temperature calibration. It should be noted that commercial temperature and relative humidity chambers are available that would have been sufficiently accurate. However, the systems developed here lend themselves to automation and can calibrate multiple probes simultaneously. The facilities developed herein are capable of producing probes with an uncertainty of ±3% for relative humidifies from 5% to approximately 90%, and an error of ±3.5% for humidifies from 90% to 95%. An uncertainty of ±0.2°C can be attained using the temperature calibration.

Effects of sodium chloride and relative humidity on growth and sporulation of moulds isolated from cured fish

A total of 14 moulds were isolated from 84 samples of cured fish obtained from several processing centres and retail shops in Lagos, Ogun and Oyo States, Nigeria. Aspergillus niger, A. flavus and A. chevalieri were the most prevalent. With the exception of Basipetospora sp., slight inhibition of mycelial growth and/or sporulation was recorded when isolates were cultured in basal medium containing 5% sodium chloride. The extent of inhibition increased with increasing salt concentrations, and at 25% level all the species had their growth completely inhibited. When fish substrates inoculated with test fungi were kept inside 65% relative humidity (RH) chambers for 21 days, no detectable utilization of the substrates was recorded for any of the fungal species. Whereas only A. chevalieri and A. restrictus utilized the substrates when placed inside 70% RH chambers, all the test moulds recorded detectable utilization (though at varying extents) of same at 80% and 90% RH levels. The latter RH was the most conductive and under it A. niger, Penicillium sp. and the two isolated Scopulariopsis sp. brought about the greatest loss in weight of the substrates.

Nitrous Acid Formation in an Experimental Exposure Chamber

Reactive indoor chemistry has seldom been considered in investigations of the health effects of exposure to indoor contaminants although improved understanding may help to reduce exposure misclassification as well as identify previously unknown exposures. Nitrous acid (HONO), formed from the heterogeneous reaction of NO2 with water on indoor surfaces, may be a neglected and important confounder in studies of nitrogen dioxide (NO2) health effects. The understanding of HONO – NO2 relationships is important since conventional measurements of NO2 actually measure a number of nitrogen oxides including HONO. Accordingly, we examined the effects of relative humidity, chamber residence time, the presence of carpeted sufaces and the presence of human subjects on the production of HONO following the injection of NO2 into a chamber. Increasing chamber relative humidity led to greater HONO concentrations at a given NO2 level. At 80% relative humidity, HONO concentrations were 11% of the NO2 concentration. Increased residence time in the chamber increased HONO levels, with a five-fold increase in HONO levels between 20 minute and 120 minute residence times. The presence of wool carpets in the chamber was not found to affect significantly the HONO production rates, although NO2 decay rates were increased. When human subjects were present in the chamber, HONO concentrations decreased by as much as 50% of the levels present under similar conditions with no subjects in the chamber. In light of our results we argue that future investigations of NO2 health effects and indoor air quality must recognize the importance of indoor chemistry, and in particular, the likelihood of elevated concentrations of HONO which will interfere with NO2 measurements and potentially confound the investigation of concentration-effect relationships. Similarly, previous studies demonstrating a relationship between health endpoints and NO2 exposure should be viewed with caution until the presence and importance of other potentially toxic nitrogenous compounds in the exposure environment are evaluated.

Effect of time, temperature and humidity on biodeterioration of corn cake snack.

Food spoilage microorganisms representing 5, 6 and 10 genera of moulds, yeasts and bacteria, respectively were isolated from corn cake snack. Each of the samples analysed had initial pH value favourable to microbial growth and activities while only 28% had spoilage-enhancing moisture contents (> 13%). The effect of temperature and relative humidity (RH) on biodeterioration during a 24-day storage period was determined by monitoring changes in the pH and total microbial colony counts. Whereas very little or no deterioration was recorded for samples contained in 51% and 71% RH chambers at 30 and 45 degrees C, substantial deterioration was obtained at the same temperatures under 89.5% and 100% RH. At 15 degrees C, very little or no deterioration was detected except under 79.5%, 89.5% and 100% RH when slight spoilage changes were recorded as from the 12th or 18th day. The overall results show that the obtained colony counts and pH values monitor spoilage equally.

Regional differences in the sweating responses of older and younger men

Ten older (60-71 yr) and nine younger (20-25 yr) active healthy men were exposed to passive heating [by placing the lower legs and feet in a 43 degrees C water bath for 60 min while sitting in a warm (35 degrees C, 45% relative humidity) chamber] in summer and winter. The increase in rectal temperature (Tre) was significantly (P less than 0.05) greater, and mean skin temperature and forearm blood flow were lower, for the older men in both seasons. Total sweating rate was lower in the older men, but significantly (P less than 0.05) so only in the summer. The Tre threshold for sweating was unaffected by either age or site (back vs. thigh). The local sweating rate (msw) on the thigh was significantly lower (P less than 0.05) for the older men throughout the exposure, whereas there were no significant age-related differences for the average or peak values of back msw, although lesser sweating on the back occurred during the first 30 min of exposure. The decreased msw on the thigh was due to a lower sweat output per heat-activated sweat gland rather than from recruitment of fewer glands. It was concluded that regional differences exist in the age-related decrement in sweat gland function. Furthermore, these findings suggest that aging leads to a decreased ability to maintain body temperature with passive heating of the extremities, which may be attributed in part to decreased regional sweat gland function.

Potassium Nutrition and Moisture Stress Tolerance of Salvia

Elevated K fertilization during bedding plant production may reduce irrigation demand and moisture stress during marketing and landscape establishment. Lindhauer (1985) indicated increasing K fertilizer concentration reduced transpirational water loss and decreased the influence of moisture stress on gas exchange for sunflower. The objective of this study was to determine the influence of K nutrition level on gas exchange of salvia (Salvia splendens F. Sellow ‘Bonfire’) during the onset of moisture stress. Seed of salvia were sown on 11 Jan. 1988 and transplanted 14 days later into 500-ml plastic pots containing a 1 peat : 1 perlite (v/ v) medium amended with 1 kg of Micromax (Sierra Chemical Co., Milpitas, Calif.) and 3 kg dolomitic limestone/m. Plants were grown in a glasshouse under long-day conditions [night interruption from 2200 to 0200 HR using incandescent lights providing ≈4 μmol·s ·m photosynthetic photon flux (PPF) at the top of the plant canopies] to extend vegetative growth. Potassium was applied with each watering at 75, 300, or 600 mg K/liter from KCl. Each K solution also contained (in mg·liter) 200 N from NH4NO3 and 25 P from phosphoric acid. Solutions were applied at the rate of 250 ml at each watering to maintain constant root-zone concentrations of nutrients. Treatments were arranged in a randomized complete block design with eight single-plant (eight pots) replicates for each treatment. Plants were irrigated at 0545 HR and placed under supplemental lighting provided with 1000-W high-pressure sodium lamps. Levels of PPF ranged from 605 to 745 μmol·s ·m during gas exchange measurements. Net photosynthesis (Pn), transpiration (E), leaf conductance (gL), and internal CO2 concentration (CI) were obtained using the LI-COR Model 6200 portable photosynthesis system (LI-COR, Lincoln, Neb.). Mean gas analyzer leaf chamber relative humidity, temperature, and CO2 concentration during measurements were 38% ± 7% 27 ± 2C, and 360 ± 27 mg·liter, respectively. Mes-

129Xe NMR proof for the distribution of platinum species during Pt/NaY preparation by H 2PtCl 6 impregnation and Pt(NH 3) 42+ cation exchange methods

129Xe NMR spectroscopy was used to measure the distribution of platinum species during the preparation of Pt/NaY catalysts by the impregnation of H 2PtC l6 or the cation exchange of Pt(NH 3) 4 2+ into a NaY zeolite. The location of platinum species during the impregnation was found to be affected by the impregnation time and the drying mode. More uniform distributions of platinum species in the impregnation were achieved by longer thermal treatments in a 100% relative humidity chamber before calcination. However, the cation exchange method gave uniform distribution of Pt species in the zeolite channel throughout the ion exchange, calcination, and reduction. This result was consistent with the rate of H 2PtCl 6 adsorption on the NaY zeolite in aqueous solution and the platinum metal dispersion of the Pt/NaY samples.

Evaluation of a Rapidly Disintegrating, Moisture Resistant Lacquer Film Coating

AbstractSimplex optimization was used during the development of a rapidly disintegrating, moisture resistant lacquer film coating. A hygroscopic aniomic exchange resin with the capability of adsorbing four to five times its weight in water was used as the model drug. The coating variables investigated included levels of magenesium stearate, talc, hydroxypropylmethylcelluslose (5 cps), polyethylene glycol 8000, Opaspray, and Eudragit E30D. Response parameters monitored included disintegration time, percent weight gain after 48 hours in a 30 deg C 75% relative humidity chamber and physical appearance. The effect of the core tablet on the performance of the coated tablet was also investigated. This study illustrates the use of the simplex design in the development of a film coating formula. It also examines the interaction between the core tablet and the film coating.

Processing Conditions Affecting the Hygroscopic Behavior of Freeze‐Dried Passion Fruit Juice

ABSTRACTThe effect of freezing rate, freeze drying temperature, added sucrose and anticaking agents, on the water sorption kinetics and hygroscopic equilibrium of freeze‐dried passion fruit juice was investigated. Slow frozen samples (‐45°C) were prepared in a Harris freezer and fast frozen ones were prepared in liquid nitrogen (‐ 195.8°C) and a dropping technique. A freeze‐drier 12F Pilot Stokes was used to freeze‐dry the samples, and the studies of hygroscopicity were conducted in an automatically controlled temperature and relative humidity chamber. The results show the significant influence of the rate of freezing and added sucrose on reducing product hygroscopicity.

MEASUREMENT OF THE KINETICS OF SOLUTION DROPLETS IN A CONTINUOUSLY MIXED CHAMBER

ABSTRACT An experimental system is designed for the measurement of the evaporation and growth kinetics of individual solution droplets. Electrostatically charged droplets, nominally tens of micrometers in diameter, are suspended in a hyperboloidal electrodynamic chamber by balancing the droplet ueight against a uniform electrostatic field. By controlling the mixing dynamics in the chamber with specific flow configurations, a continuously mixed chamber is achieved. Consequently the Instantaneous chamber relative humidity is predicted from an exponential law with o characteristic relaxation time which is given by the ratio of the chamber volume and the gas volumetric flow rate. The evaporation and growth kinetics of phosphoric acid droplets is measured for relative humidity changes between 30 and 80%. Comparison between experimental and theoretical instantaneous droplet masses reveals less than a 5% deviation.The present system is employed to analyze the effect of adsorbed hexadecanol surfactant molecules on the evaporation and growth kinetics of phosphoric acid droplets. It is found a critical coverage exists which will result in a dramatic reduction in the evaporation kinetics of solution droplets. ConcomiCantly, the condensation coefficient is reduced from unity to 4.0 x 10-5 as droplet kinetics occur in the presence of a complete monolayer of hexadecanol.

An instrument for measuring the average stomatal conductance of conifer seedlings

A ventilated, transient-type porometer was designed to nondestructively measure the average stomatal conductance of conifer seedlings. The porometer consists of a low-power microprocessor unit and a stainless steel chamber which encloses the seedling. Conductance is calculated from the measured rate of increase in chamber relative humidity above the ambient level. Consequently, chamber air does not have to be dried prior to measurement. Direct readout of stomatal conductance is provided by means of a liquid crystal display and a serial (RS232) port. Porometer calibration over a range of humidities showed that the effective chamber volume was consistently 25% larger than the actual chamber volume. Stomatal conductance measurements made on Douglas-fir (Pseudotsugamenziesii (Mirb.) Franco) seedlings using the porometer agreed well with average values obtained with a ventilated diffusion porometer using four needle samples. The porometer proved to be very convenient to use in a forest clearcut environment, with the measurement procedure taking about 1 min. Measurements can be made on a seedling over the growing season because the use of the instrument causes no injury to stem, branches, and needles.

Moisture Sorption Kinetics for Water-Soluble Substances I: Theoretical Considerations of Heat Transport Control

A model based on heat transport control was developed to describe the uptake of water on a deliquescent solid in an atmosphere of pure water vapor. The model assumes the presence of a saturated liquid film on the surface of the solid. The decrease in the vapor pressure of water over the surface, brought about by the colligative effect of solid dissolved in the liquid film, is effectively offset by the increase in temperature of the film (and the solid) caused by the heat released on condensation of the water vapor. The thermal transients die out quickly and a steady-state analysis is valid. At steady state the temperature of the liquid film (and solid) is that temperature at which the vapor pressure of water above the saturated solution is equal to the chamber pressure. Consequently, water uptake occurs at a rate that depends on the heat flux away from the surface. The water uptake rate, Wʹh, is constant at a given relative humidity and is described by an equation of the form Wʹh=(C+F) ln (RHi/RHo), where C and F are conductive and radiative coefficients, RHi the chamber relative humidity, and RHo the relative humidity at and above which continuous water uptake (deliquescence) occurs. The model contains no adjustable parameters and can thus be directly tested against experimental results.

Survival of Salmonella montevideo on Wheat Stored at Constant Relative Humidity

Eleven samples of Ottawa variety hard red winter wheat were inoculated with a standardized suspension of Salmonella montevideo . The contaminated wheat samples were placed in constant relative humidity (RH) chambers held at 25 C. Relative humidities were 7, 11, 22, 33, 43, 53, 62, 75, 84, 92, and 98%. Constant RH at 25 C was maintained with different saturated salt solutions in the sealed chambers. Periodic counts of viable S. montevideo cells per gram of wheat were made over a 28-week sampling period. Viable counts of S. montevideo on wheat held at 7, 11, and 22% RH decreased from an initial 10 6 cells/g of wheat to a final count of 10 4 cells/g in each sample. Samples stored at 33, 43, 53, and 62% RH decreased from 10 6 viable cells/g to 3.6 × 10 3 , 10 3 , 10 2 , and 20 viable cells/g, respectively. No viable S. montevideo cells were detected in the samples held at 75, 84, 92, and 98% RH after 22, 16, 26, and 16 weeks, respectively.