Different Relative Humidities (different + relative_humidity)

Distribution by Scientific Domains


Selected Abstracts


Effects of Water-Glycerol and Water-Sorbitol Interactions on the Physical Properties of Konjac Glucomannan Films

JOURNAL OF FOOD SCIENCE, Issue 2 2006
Lai 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]


Combined application of extrusion-spheronization and hot-melt coating technologies for improving moisture-proofing of herbal extracts

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2010
Hao 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]


Characteristics of hydrogen bond formation between sugar and polymer in freeze-dried mixtures under different rehumidification conditions and its impact on the glass transition temperature

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2008
Koreyoshi 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 naproxen

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 1 2007
Piera 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]


Influence of relative gas humidity on the inactivation efficiency of a low temperature gas plasma

JOURNAL OF APPLIED MICROBIOLOGY, Issue 6 2008
P. Muranyi
Abstract Aims:, To investigate the effect of relative gas humidity on the inactivation efficiency of a cascaded dielectric barrier discharge (CDBD) in air against Aspergillus niger and Bacillus subtilis spores on PET foils. Methods and Results:, The inactivation kinetics as a function of treatment time were determined using synthetic air with different relative humidity as the process gas. Spores of A. niger and B. subtilis respectively were evenly sprayed on PET foils for use as bioindicators. In the case of A. niger, increased spore mortality was found at a high relative gas humidity of 70% (approx. 2 log10). This effect was more evident at prolonged treatment times. In contrast, B. subtilis showed slightly poorer inactivation at high gas humidity. Conclusions:, Water molecules in the process gas significantly affect the inactivation efficiency of CDBD in air. Significance and Impact of the Study:, Modifying simple process parameters such as the relative gas humidity can be used to optimize plasma treatment to improve inactivation of resistant micro-organisms such as conidiospores of A. niger. [source]


The influence of species and growing conditions on the 18-O enrichment of leaf water and its impact on ,effective path length'

NEW PHYTOLOGIST, Issue 3 2009
Ansgar Kahmen
Summary ,,The stable oxygen isotope ratio (,18O) of plant material has been shown to contain essential information on water and carbon fluxes at the plant and ecosystem scales. However, the effective path length (Lm), a parameter introduced to leaf-water models still requires a comprehensive biological characterization to allow interpretation of ,18O values in plant material with confidence. ,,Here, we tested the variability of Lm across and within three species that developed leaves in environments with different relative humidity. We also tested whether the Lm of fully developed leaves is affected by short-term fluctuations in relative humidity. ,,We determined that significant differences in Lm exist among Phaseolus vulgaris, Rizinus communis and Helianthus annuus. Within a given species, however, Lm values did not differ significantly among individuals. ,,These findings indicate that Lm is species specific and a relatively constant parameter and that Lm will not obscure the interpretation of ,18O values in plant material of a given species. We urge caution, however, because values for Lm are derived from fitting leaf-water models to measured values of ,18O, so care must be taken in assigning a ,cause' to values of Lm as they likely capture a combination of different biological leaf properties [source]