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Humidity
Kinds of Humidity Terms modified by Humidity Selected AbstractsEFFECTS OF OVEN HUMIDITY ON FOODS BAKED IN GAS CONVECTION OVENS,JOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 3 2004J. XUE ABSTRACT Bread, cakes, and cookies were baked in direct- and indirect-gas fired, foodservice style convection ovens. Oven humidity was varied by including different numbers of perlite and water dummy loads during baking. Oven, product, and dummy temperatures were continuously recorded during baking, as was oven humidity. The properties of the finished baked foods were measured. Increased oven humidity resulted in products with higher yield, greater volume or spread, lighter color, and reduced firmness. [source] INFLUENCE OF TEMPERATURE AND RELATIVE HUMIDITY ON THE PHYSICAL STATES OF COTTON CANDYJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 4 2004THEODORE P. LABUZA ABSTRACT Cotton candy is made by melting crystalline sucrose above 210C in a bowl which shoots molten liquid sucrose into the air where it rapidly cools and dries into an amorphous glassy solid state. As such, it is highly hygroscopic, picking up moisture as %RH increases and becoming rubbery. The glass transition line (Tg vs. %RH) divides the two states. When rubbery, cotton candy should collapse forming crystalline sucrose becoming unsaleable. Cotton candy was stored at 25C and at %RH from ,0% to 75%. Moisture gain/loss, visual observations, and powder X-ray diffraction using a Seimens 5005-powder X-ray diffractometer were used to evaluate collapse and crystallization. At ,0% and 11% RH (below Tg), cotton candy maintained a stable structure for at least 12 months. At 33% RH (just at Tg), it collapsed and crystallized within 3 days while at 45, 54 and 75% RH, collapse and crystallization occurred in less than 1 day. [source] Impact of artificial photoperiodism on the colony development of the bumblebee Bombus terrestrisENTOMOLOGICAL SCIENCE, Issue 4 2007Md Ruhul AMIN Abstract This study investigated the effect of the photoperiodic regimes 0 h light : 24 h dark (LD 0:24), LD 8:16, LD 16:8 and LD 24:0 at 28°C and 50% Relative Humidity (RH) on the colony development of hibernated (2.0, 2.5, 3.0, 3.5 and 4.0 months) bumblebee queens. The queens which had hibernated for 3.0 months and which were reared in a LD 8:16 photoperiod showed the highest rate of colony initiation (88.2%), colony foundation (67.6%) and progeny queen production (38.2%). The photoperiod LD 8:16 also produced the shortest period of colony initiation and colony foundation. The highest number of sexual males (171.2 ± 12.2) and queens (91.2 ± 9.9) were produced in the colonies when 3.5 and 3.0 month hibernated queens were kept in an LD 8:16 photoperiod. The results show that light regime and hibernation duration affect colony characteristics of Bombus terrestris. [source] Bayesian analysis of dynamic factor models: an application to air pollution and mortality in São Paulo, BrazilENVIRONMETRICS, Issue 6 2008T. Sáfadi Abstract The Bayesian estimation of a dynamic factor model where the factors follow a multivariate autoregressive model is presented. We derive the posterior distributions for the parameters and the factors and use Monte Carlo methods to compute them. The model is applied to study the association between air pollution and mortality in the city of São Paulo, Brazil. Statistical analysis was performed through a Bayesian analysis of a dynamic factor model. The series considered were minimal temperature, relative humidity, air pollutant of PM10 and CO, mortality circulatory disease and mortality respiratory disease. We found a strong association between air pollutant (PM10), Humidity and mortality respiratory disease for the city of São Paulo. Copyright © 2007 John Wiley & Sons, Ltd. [source] Evolution of Permanent Deformations (or Memory) in Nafion 117 Membranes with Changes in Temperature, Relative Humidity and Time, and Its Importance in the Development of Medium Temperature PEMFCs,FUEL CELLS, Issue 4 2009G. Alberti Abstract An important problem for medium temperature polymer electrolyte fuel cells (MT PEMFCs) operating in the temperature range 90,140,°C is the short time-life of proton conducting membranes. To shed some light on the empirical annealing treatments used for increasing the membrane durability, a systematic research on the effects of thermal treatments of Nafion 117 membranes was undertaken with the hope that the information obtained could be useful for a better understanding of the real limits for MT PEMFCs. Kinetic experiments showed that, for each couple of T,RH values, the water taken up from the membrane reaches a constant value only after long times of equilibration (,200,h). Taking into account that the enlargements provoked by the water-uptake remain as permanent deformations when the samples are cooled, it was found that the evolution of the deformations provoked by changes in temperature and RH can be conveniently estimated at 20,°C by determining the water taken up after equilibration in liquid water. By relating the counter-elastic index of the matrix (nc(m)) to the extent of these deformations, a set of equations were obtained which allowed us to predict their evolution with changes of temperature and relative humidity. A good agreement with experimental values was found. The importance of this discovery for the development of MT PEMFCs is discussed. [source] Ecophysiological Response of Plants to Combined Pollution from Heavy-duty Vehicles and Industrial Emissions in Higher HumidityJOURNAL OF INTEGRATIVE PLANT BIOLOGY, Issue 12 2006Hong-Xia Cui Abstract Pollution can be aggravated in industrial areas if traffic exhausts are mixed with industrial emissions under high humidity conditions. Plants growing in such environments may suffer from severe stress. The impact of vehicle emissions on urban vegetation in an industrial area in Qingdao, China, was investigated by studying seven plant species at visible, physiological and chemical levels. The traits of plant species in certain environmental conditions were compared between a clear area, Badaguan (BDG), and polluted area, Roadside (RS). We found that foliar sulfur uptake for all species was not significantly high at RS compared with BDG, although the sulfur content of atmosphere and surface soils at RS were much higher than those at BDG. For Ailanthus altissima Swingle, the content of foliar pigment and net photosynthesis rate (PN) decreased by 20%. Meanwhile, leaves became incrassate and no visible leaf damage was noted, suggesting this species could adapt well to pollution. A 50% decrease in PN occurred in Hibiscus syriacus L., but there was no statistical change in content of chlorophyll a and b and water uptake. Also, thickened leaves may prevent the pollutant from permeation. Foliar water content was still at a low level, although a water compensation mechanism was established for Fraxinus chinensis Rosb. reflected by low water potential and high water use efficiency. More adversely, a 65% decrease in PN happened inevitably with the significant decomposition of photosynthetic pigments, which exhibited visible damage. We also noted in one evergreen species (Magnolia grandiflora L.) that water absorption driven by low water potential should be helpful to supply water loss induced by strong stomatal transpiration and maintain normal growth. Furthermore, photosynthetic pigment content did not decline statistically, but supported a stable net assimilation. Two herbaceous species, Poa annua L. and Ophiopogon japonicus Ker-Gawl., were very tolerant to adverse stress compared to other woody species, especially in assimilation through a compensatory increase in leaf area. A more remarkable decline in PN (decrease 80%) was noted in the exotic but widespread species, Platanus orientalis L., with serious etiolation and withering being exhibited on the whole canopy. Our results suggested, special for woody species, that most native species are more tolerant to pollution and therefore should to be broadly used in a humid urban industrial environment with heavy-duty vehicle emissions. (Managing editor: Ya-Qin Han) [source] A Process Analytical Technology approach to near-infrared process control of pharmaceutical powder blending.JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 2 2006Part I: D-optimal design for characterization of powder mixing, preliminary spectral data evaluation Abstract Experimental design, multivariate data acquisition, and analysis in addition to real time monitoring and control through process analyzers, represent an integrated approach for implementation of Process Analytical Technology (PAT) in the pharmaceutical industry. This study, which is the first in a series of three parts, uses an experimental design approach to identify critical factors affecting powder blending. Powder mixtures composed of salicylic acid and lactose were mixed in an 8 qt. V-blender. D-optimal design was employed to characterize the blending process, by studying the effect of humidity, component concentration, and blender speed on mixing end point. Additionally, changes in particle size and density of powder mixtures were examined. A near-infrared (NIR) fiber-optic probe was used to monitor mixing, through multiple optical ports on the blender. Humidity, component concentration, and blender speed were shown to have a significant impact on the blending process. Furthermore, humidity and concentration had a significant effect on particle size and density of powder mixtures. NIRS was sensitive to changes in physicochemical properties of the mixtures, resulting from process variables. Proper selection of NIR spectral preprocessing is of ultimate importance for successful implementation of this technology in the monitoring and control of powder blending and is discussed. © 2005 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 95:392,406, 2006 [source] Effect of Atmospheric Humidity on the Fatigue Crack Propagation Behavior of Short Cracks in Silicon NitrideJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 3 2000Sotomi Ishihara The effect of the environment on crack-growth processes in silicon nitride was studied by investigating the static and fatigue crack-growth behavior of small surface cracks, as influenced by testing (i) in the ambient environment, (ii) in distilled water, (iii) under vacuum, and (iv) in toluene. A principal finding was that testing under cyclic conditions led to crack-growth rates that were much higher in air than in toluene, whereas testing under static conditions in air or toluene led to minor differences in the rate of static fatigue crack growth. This difference in sensitivity to the environment under static and cyclic loading conditions was attributed, in part, to a much-greater extent of microcracking at the surface ahead of the main crack in air under cyclic conditions, in comparison to that in other environments. This propensity for microcracking at the surface in air under cyclic conditions also was reflected in the aspect ratios of the crack shapes that developed. [source] Influence of Normal Force and Humidity on the Friction and Wear of Unlubricated Reciprocating Sliding Steel/Steel CouplesLUBRICATION SCIENCE, Issue 4 2004D. Klaffke Abstract The friction and wear behaviour of different steel/steel couples was investigated in laboratory tests with unlubricated reciprocating sliding motion. Two different steel balls were tested against two different steel discs in dry, normal, and moist air at room tem-perature. The influence of normal force on friction and wear was studied in the range from 1 to 10 N for all three levels of relative humidity (RH). RH strongly influenced wear behaviour for all four couples, while the friction behaviour was less affected by RH. For all the couples, normal force was found to influence wear rate with a tendency for the wear rate to increase with decreasing normal force. The coefficient of friction also increased with decreasing normal force, but to a much lesser extent than that evaluated for the wear rate. [source] Influence of Temperature and Relative Humidity on the Friction and Wear of Unlubricated Reciprocating Sliding Steel/ Steel CouplesLUBRICATION SCIENCE, Issue 4 2004D. Klaffke Abstract Many tribosystems are subjected to different conditions with respect to temperature and humidity. Reciprocating sliding tests with steel/steel couples were performed using a laboratory test rig in air with varying relative humidity and temperature. During each test the friction force, the total linear wear, the electrical contact resistance, and the acoustic emission were recorded. Tests with self-mated couples of bearing steel (100r6) and of stainless steel (X10CrNiMoNb18-10/X5CrNi18-9) in a ball-on-disc arrangement revealed small effects of temperature and humidity on friction, but a strong effect of the water vapour content on the wear rate of the system. Attempts were made to correlate changes of wear behaviour with different wear mechanisms. [source] Productivity and energy partition of late lactation dairy cows during heat exposureANIMAL SCIENCE JOURNAL, Issue 1 2010Kyoung Hoon KIM ABSTRACT Three late-lactation Holstein cows were used to determine the effects of environmental temperature on performance and energy partitioning. Each cow was housed in a respiratory chamber for 30 consecutive days and exposed to three different conditions of environmental temperature: (i) 20°C and 20°C (20°C), (ii) 25°C and 20°C (25°C), (iii) 30°C and 25°C (30°C) during the day and night, respectively. The temperature was switched in an interval of 10 days. Humidity in the chamber was maintained at 55,65% through the entire experimental period. The daily mean as well as morning and evening rectal temperatures of Holstein cows increased linearly (P < 0.05) as chamber temperature increased. There was a significant linear reduction in dry matter (DM) intake (P < 0.05) and an increase in DM digestibility (P < 0.05). The response in milk yield, however, was not affected by heat stress. There were no significant differences among treatments for intake energy, heat production, net energy for lactation and net energy for gain. This results of this study disagreed with the assumption that late lactation cows gave priority to increasing body tissue at the expense of milk production under thermal stress. [source] Consensus between GCM climate change projections with empirical downscaling: precipitation downscaling over South AfricaINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2006B. C. Hewitson Abstract This paper discusses issues that surround the development of empirical downscaling techniques as context for presenting a new approach based on self-organizing maps (SOMs). The technique is applied to the downscaling of daily precipitation over South Africa. SOMs are used to characterize the state of the atmosphere on a localized domain surrounding each target location on the basis of NCEP 6-hourly reanalysis data from 1979 to 2002, and using surface and 700-hPa u and v wind vectors, specific and relative humidities, and surface temperature. Each unique atmospheric state is associated with an observed precipitation probability density function (PDF). Future climate states are derived from three global climate models (GCMs): HadAM3, ECHAM4.5, CSIRO Mk2. In each case, the GCM data are mapped to the NCEP SOMs for each target location and a precipitation value is drawn at random from the associated precipitation PDF. The downscaling approach combines the advantages of a direct transfer function and a stochastic weather generator, and provides an indication of the strength of the regional versus stochastic forcing, as well as a measure of stationarity in the atmosphere,precipitation relationship. The methodology is applied to South Africa. The downscaling reveals a similarity in the projected climate change between the models. Each GCM projects similar changes in atmospheric state and they converge on a downscaled solution that points to increased summer rainfall in the interior and the eastern part of the country, and a decrease in winter rainfall in the Western Cape. The actual GCM precipitation projections from the three models show large areas of intermodel disagreement, suggesting that the model differences may be due to their precipitation parameterization schemes, rather than to basic disagreements in their projections of the changing atmospheric state over South Africa. Copyright © 2006 Royal Meteorological Society. [source] Exergetic evaluation of drying of laurel leaves in a vertical ground-source heat pump drying cabinetINTERNATIONAL JOURNAL OF ENERGY RESEARCH, Issue 3 2007Ebru Hancioglu Kuzgunkaya Abstract This paper is concerned with the exergy analysis of the single layer drying process of laurel leaves in a ground-source heat pump drying cabinet, which was designed and constructed in the Solar Energy Institute, Ege University, Izmir, Turkey. The effects of drying air temperature on exergy losses, exergy efficiencies and exergetic improvement potential of the drying process are investigated. The results have indicated that exergy efficiencies of the dryer increase with rising the drying air temperature. Moreover, the laurel leaves are sufficiently dried at the temperatures ranging from 40 to 50°C with relative humidities varying from 16 to 19% and a drying air velocity of 0.5 m s,1 during the drying period of 9 h. The exergy efficiency values are obtained to range from 81.35 to 87.48% based on the inflow, outflow and loss of exergy, and 9.11 to 15.48% based on the product/fuel basis between the same drying air temperatures with a drying air mass flow rate of 0.12 kg s,1. Copyright © 2006 John Wiley & Sons, Ltd. [source] Gas permeation related to the moisture sorption in films of glassy hydrophilic polymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010F.L. Laksmana Abstract The purpose of this article is to elucidate the effect of integral sorption of moisture on gas permeation in glassy hydrophilic polymers. The oxygen and the simultaneous moisture sorption into various hydroxypropyl methylcellulose (HPMC) films were measured under a wide range of relative humidities using sorption analyzer equipment. Correspondingly, the oxygen permeability at different ambient conditions was measured using an oxygen detector. The solubility of oxygen in the HPMC film was found to be affected by the amount of water and therefore by the water state. At low moisture content, the water molecules are present as bound water, which promotes the sorption of oxygen in the HPMC films. At moisture content higher than 5%, water clusters are rapidly formed, which increase the affinity of HPMC polymer towards water rather than towards oxygen molecules, resulting in a decrease of oxygen solubility in the polymer. This was found to be the governing factor for the reduction in the oxygen permeability in glassy HPMC films at high water activity. This proposes a specific interaction between moisture sorption and oxygen transport in coating films like HPMC, which is of important aspect in the coating design and formulation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Refractive-index anisotropy and optical dispersion in films of deoxyribonucleic acid,JOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Anna Samoc Abstract We have determined the refractive indices in the directions parallel and perpendicular to the surface plane of films of deoxyribonucleic acid (DNA) and their wavelength dispersion. These parameters are fundamental for understanding the properties of waveguiding structures containing DNA-based photonic materials. The orientation of DNA molecules in films and their optical properties are sensitive to the film fabrication and environmental conditions influencing the structure. Prism coupling measurements show ambient-humidity-related changes in the refractive index, birefringence, and anisotropy of the alignment of the DNA molecules in the films studied. These films were 0.5,5 ,m thick, were prepared by both spin coating and casting from aqueous solutions containing 0.1,3 wt % DNA, and were measured in ambient air with relative humidities of 37,58%. The optical properties of the films and the orientation of the DNA molecules are discussed with respect to the mechanism for the formation of the polymer liquid-crystalline phases during film deposition. The dispersion of the refractive indices in films of native DNA has been derived from interference fringes in absorption and reflection spectra in the wavelength range of 350,2700 nm through the fitting of the positions of the fringes with the Sellmeier dispersion formula in combination with the prism coupling data. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 105: 236,245, 2007 [source] POSTHARVEST CHANGES IN FRESH SWISS CHARD (Beta vulgaris, type cycla) UNDER DIFFERENT STORAGE CONDITIONSJOURNAL OF FOOD QUALITY, Issue 2 2000SARA INÉS ROURA ABSTRACT The effects of storage temperature and relative humidity on the quality of Swiss chard (Beta vulgaris, type cycla) were investigated. Quality was assessed through determinations of water content, weight loss, chlorophyll content, pH, titratable acidity, soluble solids content and sensory evaluations. Storage conditions were 4 and 18C and 43, 86 and 98% relative humidities (RH). The quality of chard leaves was unacceptable after three days of storage at 18C, independent of the RH. Chard leaves kept at 4C and 86 and 98% RH remained acceptable for 9 days. The dehydration suffered by samples kept at 4C and 43% RH turned them unacceptable after 4 days of storage. [source] Effects of Water-Glycerol and Water-Sorbitol Interactions on the Physical Properties of Konjac Glucomannan FilmsJOURNAL OF FOOD SCIENCE, Issue 2 2006Lai Hoong Cheng ABSTRACT Konjac glucomannan (KGM)-edible films were prepared with different amounts of glycerol or sorbitol as a plasticizer. Films were characterized by moisture sorption isotherm, and following conditioning at different relative humidities, by differential scanning calorimetry and tensile tests. Moisture and polyols (sorbitol and glycerol) were found to plasticize KGM-based films with respect to their tensile properties. However, thermal properties and water sorption capacity (WSC) of polyolplasticized KGM films were found to vary with water activity (aw), namely at low aw (< 0.6), WSC and melting enthalpy were decreased with increasing in polyol content and the opposite was true at higher aw (>0.6). This was attributed to extensive interactions between plasticizer and KGM that reduced the available active site (-OH groups) for water adsorption. The presence of polyols at low aw appeared to suppress crystalline structures due probably to restricted molecular mobility. These effects were diminished when the moisture content was >20%. [source] Phase Behavior of a Meat-Starch Extrudate Illustrated on a State DiagramJOURNAL OF FOOD SCIENCE, Issue 8 2002C.I. Moraru ABSTRACT: The phase behavior of a meat-starch extruded system was illustrated on a state diagram. A mixture of meat and potato granules (1.48:1) was extruded with a twin-screw extruder. The extrudates were equilibrated at relative humidities between 0 to 88% and their glass transitions were determined. Starch and proteins were phase separated at macromolecular level and retained their own phase transitions. The state diagram of the system showed that proteins dictated the texture of the mixed system, with starch contributing to the high value of the mechanical properties. Water had a plasticizing effect on both biopolymers. At room temperature, the extrudates with aw < 0.32 were glassy, while those with aw > 0.57 were rubbery. [source] Combined application of extrusion-spheronization and hot-melt coating technologies for improving moisture-proofing of herbal extractsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2010Hao Chen Abstract The aim of this research was to investigate the moisture-proofing effect and its mechanism for herbal extracts using extrusion-spheronization combined with hot-melt coating. Guizhi Fuling (GF) compound herbal extract with high hygroscopicity was used as a model drug. In the process of extrusion-spheronization, pellets containing 100% GF were prepared, and then coated with hot-melt coating material using a traditional coating pan. The moisture sorption data for GF were determined by storage at a series of different relative humidities. When the pellets were coated with a 96:4 mixture of stearic acid and polyethylene glycol 6000, the cumulative drug release was over 90% at 45,min while the moisture content was 4.9% at 75% RH within 10 days. These pellets have better moisture-proofing than those coated with Opadry AMB at the same coating level due to a different moisture sorption mechanism. The moisture sorption behavior of the hot-melt coating can be attributed to water vapor diffusion via a porous matrix system, while the Opadry AMB coating system involved a swelling controlled system. The Higuchi model was the best fit for the moisture sorption of the hot-melt coating in all formulations whereas the Opadry AMB coating fitted the Nuttanan model. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99: 2444,2454, 2010 [source] Effect of molecular weight, temperature, and additives on the moisture sorption properties of polyethylene glycolJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2010Jared A. Baird Abstract Polyethylene glycol (PEG) is a hygroscopic polymer that undergoes the phenomenon of deliquescence once a critical relative humidity (RH0) is reached. The purpose of this study was to test the hypothesis that the deliquescence behavior of PEG will be affected by the polymer molecular weight, temperature, and the presence of additives. The deliquescence relative humidity for single component (RH0) and binary mixtures (RH0,mix) were measured using an automated gravimetric moisture analyzer at 25 and 40°C. Changes in PEG crystallinity after exposure to moisture were qualitatively assessed using powder X-ray diffraction (PXRD). Optical microscopy was used to visually observe the deliquescence phenomenon. For single component systems, decreasing PEG MW and elevating the temperature resulted in a decrease in the observed RH0. Physical mixtures of acetaminophen and anhydrous citric acid with both PEG 3350 and PEG 100,000 exhibited deliquescence (RH0,mix) at a relative humidity below that of either individual component. Qualitative changes in crystallinity were observed from the X-ray diffractograms for each PEG MW grade at high relative humidities, indicating that phase transformation (deliquescence) of the samples had occurred. In conclusion, it was found that the deliquescence behavior of PEG was affected by the polymer MW, temperature, and the presence of additives. This phenomenon may have important implications for the stability of PEG containing formulations. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:154,168, 2010 [source] Characteristics of hydrogen bond formation between sugar and polymer in freeze-dried mixtures under different rehumidification conditions and its impact on the glass transition temperatureJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2008Koreyoshi Imamura Abstract The characteristics of hydrogen bond formation between trehalose and polyvinylpyrrolidone (PVP) in amorphous mixtures at different hydration states were quantitatively investigated. Amorphous trehalose,PVP mixtures were prepared by freeze-drying and equilibrated at different relative humidities (RH). Infrared (IR) spectra of the trehalose,PVP mixtures were obtained by Fourier transform IR spectroscopy,(FTIR) and the IR band corresponding to CO groups of PVP was deconvolved into the component bands responsible for CO groups that were free and restricted by hydrogen bonds, to estimate the degree of the trehalose,PVP interactions. The FTIR analysis indicated that approximately 80% of the CO groups of PVP formed hydrogen bonds with trehalose in the presence of more than 3 g of trehalose per gramme of PVP, independent of the RH. IR analysis of the OH stretching vibration of the sugar demonstrated that the presence of PVP lead to an increase in the free hydroxyl groups of trehalose that did not form hydrogen bonds at RH 0%. On the other hand, the water sorption behavior of the trehalose,PVP mixtures suggested that rehumidification diminished the effect of PVP on increasing the free OH groups. Thus a peculiar relationship may exist between Tg, RH and the composition of the mixture: The presence of PVP increased Tg at RHs 0 and above 23% but decreased Tg at 11%. © 2007 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 97:1301,1312, 2008 [source] A new tetrahydrated form of sodium naproxenJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2007Piera Di Martino Abstract The anhydrous sodium naproxen (ASN) can form several hydrated phases if maintained at different relative humidities (RH). The water uptake can promote crystallographic modifications, according to the amount of water. In a previous work, the authors showed that a dihydrated form could be obtained either by crystallization in water or by exposure of the anhydrous form to a RH of 55%. In the present work, the authors report about the formation and characterization of a new tetrahydrated form, obtained by exposing the ASN to RH,,,75%. All the hydrated compounds were characterized by the combined use of several spectroscopic, thermal, and crystallographic techniques. The thermal stability of both the dihydrated and tetrahydrated compounds was also tested. © 2006 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 96:156,167, 2007 [source] Stress Development Due to Capillary Condensation in Powder Compacts: A Two-Dimensional Model StudyJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 6 2000Stefan Lampenscherf A model experiment is presented to investigate the relationship between the humidity-dependent liquid distribution and the macroscopic stress in a partially wet powder compact. Therefore, films of monosized spherical particles were cast on silicon substrates. Using environmental SEM the geometry of the liquid necks trapped between particles was imaged as a function of relative humidity. Simultaneously the macroscopic stress in the substrate adhered particle film was measured by capacitive deflection measurement. The experimentally found humidity dependence of the liquid neck size and the macroscopic film stress are compared with model predictions. The circle,circle approximation is used to predict the size of the liquid necks between touching particles as a function of the capillary pressure. Using the modified Kelvin relation between capillary pressure and relative humidity, we consider the effect of an additional solute which may be present in the capillary liquid. The results of the stress measurement are compared with the model predictions for a film of touching particles in hexagonal symmetry. The contribution of the capillary interaction to the adhesion force between neighboring particles is calculated using the integrated Laplace equation. The resulting film stress can be approximated relating this capillary force to an effective cross section per particle. The experimentally found humidity dependence of the liquid neck size is in good agreement with the model predictions for finite solute concentration. The film stress corresponds to the model predictions only for large relative humidities and shows an unexpected increase at small values. As is shown with an atomic force microscope, the real structure of the particle,particle contact area changes during the wet/dry cycle. A solution/reprecipitation process causes surface heterogeneities and solid bridging between the particles. It is claimed that the existence of a finite contact zone between the particles gives rise to the unexpected increase of the stress at small relative humidities. [source] Humidity-Responsive Starch-Poly(methyl acrylate) FilmsMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 7 2008Julious L. Willett Abstract Blown films prepared from starch-poly(methyl acrylate) graft copolymers plasticized with urea and water display shrinkage at relative humidities greater than 50%. Shrinkage at relative humidities below approximately 75% is strongly correlated with the urea/starch weight ratio, which controls the equilibrium moisture content (MC) in the films. Above 75% relative humidity, film shrinkage is essentially independent of composition. At relative humidities below 90%, films plasticized with urea and water exhibited greater shrinkage than films plasticized with water only. A master curve can be constructed by shifting shrinkage data with respect to a reference relative humidity, indicating that relaxation processes in the starch phase control film shrinkage. This conclusion is confirmed by the fact that shrinkage data for a wide range of compositions and relative humidities fall on a single curve when plotted against MC. Polarized Fourier transform infrared spectroscopy indicated some loss of orientation in the starch phase during shrinkage. These results demonstrate that the hydrophilic nature of starch can be exploited to develop responsive polymers which display controllable shrinkages activated by increases in relative humidities. [source] Moisture sorption in moulded fibre trays and effect on static compression strengthPACKAGING TECHNOLOGY AND SCIENCE, Issue 4 2003Gitte Sørensen Abstract This study provides a basic understanding of moisture sorption in moulded fibre packaging for food at varying environmental temperatures and humidities, and the resultant effects on static compression strength. The Guggenheim,Anderson,de Boer (GAB) model is used successfully to construct moisture sorption isotherms in the range 2,25°C and 33,98% relative humidity (% r.h.) (R2 = 0.949,0.999), in which moisture content varies from 5.4 to 28.3,g/100,g dry fibre. Static compression strength (SCS) is substantially affected by changes in moisture content of moulded fibre and decreases exponentially with increasing moisture content. The results indicate a minor hysteresis effect on static compression strength. For adsorption of moisture, a relative strength measure, % SCS (experimental SCS in kg divided by a standard SCS in kg), is given by % SCS = 13.83 + 166.50,·,e,0.0978,m (m is moisture content). The temperature dependence of moisture adsorption is incorporated in the GAB model by relating GAB coefficients, m0 and C, exponentially to temperature, T. By combining this with the exponential model for % SCS, static compression strength can be predicted directly from the surrounding temperature and humidity. Illustrated in a response surface plot the effects of changes in the surroundings are simple and readily accessible, e.g. for packaging designers and sales people. It is noted that an increase in humidity from 50% r.h. to 95% r.h. at constant temperature results in a drastic reduction in % SCS from 100% to 40%, whereas the temperature effect is typically less than 10% SCS when reducing temperature from 25°C to 2°C. Copyright © 2003 John Wiley & Sons, Ltd. [source] Water and Carboxyl Group Environments in the Dehydration Blueshift of Bacteriorhodopsin,PHOTOCHEMISTRY & PHOTOBIOLOGY, Issue 5 2000Robert Renthal ABSTRACT The proton channels of the bacteriorhodopsin (BR) proton pump contain bound water molecules. The channels connect the purple membrane surfaces with the protonated retinal Schiff base at the membrane center. Films of purple membrane equilibrated at low relative humidity display a shift of the 570 nm retinal absorbance maximum to 528 nm, with most of the change occurring below 15% relative humidity. Purple membrane films were dehydrated to defined humidities between about 50 and 4.5% and examined by Fourier transform infrared difference spectroscopy. In spectra of dehydrated-minus-hydrated purple membrane, troughs are observed at 3645 and 3550 cm,1, and peaks are observed at 3665 and 3500 cm,1. We attribute these changes to water dissociation from the proton uptake channel and the resulting changes in hydrogen bonding of water that remains bound. Also, in the carboxylic acid spectral region, a trough was observed at 1742 cm,1 and a peak at 1737 cm,1. The magnitude of the trough to peak difference between 1737 and 1742 cm,1 correlates linearly with the extent of the 528 nm pigment. This suggests that a carboxylic acid group or groups is undergoing a change in environment as a result of dehydration, and that this change is linked to the appearance of the 528 nm pigment. Dehydration difference spectra with BR mutants D96N and D115N show that the 1737,1742 cm,1 change is due to Asp 96 and Asp 115. A possible mechanism is suggested that links dissociation of water in the proton uptake channel to the environmental change at the Schiff base site. [source] Hygroreception in olfactometer studiesPHYSIOLOGICAL ENTOMOLOGY, Issue 3 2009ANDRÉS S. MARTÍNEZ Abstract In olfactometric studies, a technique used to measure insect behavioural bias towards airborne chemicals, many of the factors that could affect the bioassay outcome other than the volatiles themselves are carefully controlled (e.g. lighting conditions, temperature, spatial position, physiological state of the insects, time of day when the bioassay is performed) but one factor, namely humidity, is overlooked frequently when studying responses to plant volatiles. Many insect species respond positively and negatively to changes in humidity and, during bioassays, differences arising from odour choices with different water vapour release rates might have confounding effects versus the original intent of the behavioural study. The present study aims to assess the effect of different substrates on the water vapour content of air in an olfactometer-like set-up. The results show that airflow humidity is affected by the odour source used in the olfactometer air flow. In addition, the response of the aphid parasitoid Aphidius colemani Viereck (Hymenoptera: Aphidiidae) is studied towards different humidities and plant material in an olfactometer. The present study suggests that humidity needs to be controlled in olfactometric studies. [source] Environmental conditions influencing Sclerotinia sclerotiorum infection and disease development in lettucePLANT PATHOLOGY, Issue 4 2004C. S. Young The environmental factors that influence infection of lettuce by ascospores of Sclerotinia sclerotiorum, and subsequent disease development, were investigated in controlled environment and field conditions. When lettuce plants were inoculated with a suspension of ascospores in water or with dry ascospores and exposed to a range of wetness durations or relative humidities at different temperatures, all plants developed disease but there was no relationship between leaf wetness duration or humidity and percentage of diseased plants. Ascospores started to germinate on lettuce leaves after 2,4 h of continuous leaf wetness at optimum temperatures of 15,25°C. The rate of development of sclerotinia disease and the final percentage of plants affected after 50 days were greatest at 16,27°C, with disease symptoms first observed 7,9 days after inoculation, and maximum final disease levels of 96%. At lower temperatures, 8,11°C, disease was first observed 20,26 days after inoculation, with maximum final disease levels of 10%. Disease symptoms were always observed first at the stem base. In field-grown lettuce in Norfolk, 2000 and 2001, inoculated with ascospore suspensions, disease occurred only in lettuce planted in May and June, with a range of 20,49% of plants with disease by 8 weeks after inoculation. In naturally infected field-grown lettuce in Cheshire, 2000, disease occurred mainly in lettuce planted throughout May, with a maximum of 31% lettuce diseased within one planting, but subsequent plantings had little (, 4%) or no disease. Lack of disease in the later plantings in both Norfolk and Cheshire could not be attributed to differences in weather factors. [source] Seed moisture content affects afterripening and smoke responsiveness in three sympatric Australian native species from fire-prone environmentsAUSTRAL ECOLOGY, Issue 8 2009SHANE R. TURNER Abstract Germination of freshly collected seeds of three sympatric herbaceous species native to fire-prone environments in south-western Australia was significantly improved through the application of novel combinations of dry heat, gibberellic acid, smoke water and dry afterripening. For fresh seeds, combinations of dry heat, gibberellic acid and/or smoke water resulted in >80% germination in Austrostipa elegantissima (Poaceae) and Stylidium affine (Stylidaceae) seeds and >60% germination in Conostylis candicans (Haemodoraceae) seeds, compared with <10% germination of control seeds. For fresh seeds, two broad germination patterns were observed in response to smoke water: nil , low germination for both control and smoke water-treated seeds (A. elegantissima and S. affine); and a significant smoke response (35%) compared with control seeds (1%) (C. candicans). During afterripening, high germination for A. elegantissima seeds was achieved following 3 months storage of seeds at equilibrium relative humidities of 23,75%, but seeds stored at 5,13% equilibrium relative humidities took 6,36 months to achieve similar levels of germination. Germination of C. candicans seeds also increased after 3 months storage, to >60% at each equilibrium relative humidity and further increases over time were slight. For S. affine seeds >60% germination was achieved only after 36 months storage at 50% equilibrium relative humidity. Seeds from all three species were smoke-responsive at some point, but the interaction/effects of afterripening on the smoke response varied significantly between species. This study highlights an apparent effect of seed dormancy status on response to smoke and a surprisingly high level of ecological variation in pre-germination requirements (cues) for these co-occurring species that may relate to variation(s) in microsite selection forces operating on the soil seed bank of the different species. [source] Exclusively breastfed, low birthweight term infants do not need supplemental waterACTA PAEDIATRICA, Issue 5 2000RJ Cohen Breast milk intake, urine volume and urine-specific gravity (USG) of exclusively breastfed, low birthweight (LBW) term male infants in Honduras were measured during 8-h periods at 2 (n= 59) and 8 (n = 68) wk of age. Ambient temperature was 22,36°C and relative humidity was 37,86%. Maximum USG ranged from 1.001 to 1.012, all within normal limits. Conclusions: We conclude that supplemental water is not required for exclusively breastfed, LBW term infants, even in hot conditions. [source] | ||||||||||||||||||||||||||||||||||||||||||||||