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Surface Area Values (surface + area_value)
Selected AbstractsMeasuring masticatory performance using a new device and ,-carotene in test gummy jellyJOURNAL OF ORAL REHABILITATION, Issue 11 2010T. NOKUBI Summary, Objective methods for evaluating masticatory performance are invaluable for quantitative comparisons between various dental treatments as well as diagnosing masticatory disorder. The purpose of this study was to develop an accurate method for automatically measuring masticatory performance using a new measuring device consisting of light-emitting diodes and a photodiode and test gummy jelly. First, the relationship between six known ,-carotene concentrations in aqueous solution and the voltage values exhibited on a photodiode was investigated. Mean voltage obtained by red light incident on the photodiode indicated a significantly high correlation (r = 0·999 in a cubic function, P < 0·01) with ,-carotene concentration in the aqueous solution. Second, to establish the optimal measuring conditions for evaluating masticatory performance, factors influencing mean voltage were investigated, such as water temperature and times for rinsing the gummy jelly and dissolving ,-carotene from the jelly. A stable mean voltage was obtained by measuring under the following conditions: rinsing water temperature, 35 °C; rinsing time, 30 s; water dissolving temperature, 35 °C; dissolving time, 10 s. Finally, the relationship between seven surface area values of divided gummy jelly and ,-carotene concentrations dissolved from the divided jellies was investigated. The increase in surface area of divided test gummy jelly particles was accurately calculated (r = 0·992, P < 0·001) from mean voltage on the photodiode to change with ,-carotene concentration dissolved from the jelly surface. This new method using test gummy jelly and an automatic measuring device appears useful for precisely evaluating masticatory performance. [source] Measuring the surface area of aluminum hydroxide adjuvantJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2002Cliff T. Johnston Abstract The traditional method of determining surface area, nitrogen gas sorption, requires complete drying of the sample prior to analysis. This technique is not suitable for aluminum hydroxide adjuvant because it is composed of submicron, fibrous particles that agglomerate irreversibly upon complete removal of water. In this study, the surface area of a commercial aluminum hydroxide adjuvant was determined by a gravimetric/FTIR method that measures the water adsorption capacity. This technique does not require complete drying of the adjuvant. Five replicate determinations gave a mean surface area of 514 m2/g and a 95% confidence interval of 36 m2/g for a commercial aluminum hydroxide adjuvant. The X-ray diffraction pattern and the Scherrer equation were used to calculate the dimensions of the primary crystallites. The average calculated dimensions were 4.5,×,2.2,×,10 nm. Based on these dimensions, the mean calculated surface area of the commercial aluminum hydroxide adjuvant was 509 m2/g, and the 95% confidential interval was 30 m2/g. The close agreement between the two surface area values indicates that either method may be used to determine the surface area of aluminum hydroxide adjuvant. The high surface area, which was determined by two methods, is an important property of aluminum hydroxide adjuvants, and is the basis for the intrinsically high protein adsorption capacity. © 2002 Wiley-Liss Inc. and the American Pharmaceutical Association J Pharm Sci 91:1702,1706, 2002 [source] Triboelectrification of Spray-dried Lactose Prepared from Different Feedstock ConcentrationsJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 1 2000ORLA E. CASSIDY Powder systems may acquire electrostatic charge during various pharmaceutical processing operations and may give rise to difficulties in handling and powder flow, mainly due to adhesion/cohesion effects. We have investigated the electrostatic charging of spray-dried lactose prepared from different feedstock concentrations using a laboratory spray-dryer. Triboelectrification of the spray-dried lactose samples was effected through contact with the stainless steel surface of either a mixing vessel or a cyclone separator. Results from both techniques showed differences in charge accumulation and particle-steel adhesion between the spray-dried lactose samples. As the feedstock concentration used to produce the spray-dried lactose was increased in the range 10,50% w/v, the mean charge on the lactose decreased from ,20.8 to ,1.3 nC g,1 and ,54.9 to ,4.1 nC g,1 for the mixing vessel and cyclone separator, respectively, with a corresponding decrease in adhesion. In addition, as the feedstock concentration was increased from 10 to 50% w/v, decreases were obtained in surface area values (1.06 to 0.56 m2 g,1), pore diameter (198.7 to 83.5 ,m) and pore volume (1.09 to 0.75 cm3 g,1), and together with differences in crystal form correlated with the charge and adhesion results. The results suggested that the feedstock concentration could have a considerable influence on the charging and adhesional properties of spray-dried lactose. This may have relevance during pharmaceutical processing and manufacturing operations. [source] Surface Enthalpy, Enthalpy of Water Adsorption, and Phase Stability in Nanocrystalline Monoclinic ZirconiaJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 1 2009A. V. Radha A fundamental issue that remains to be solved when approaching the nanoscale is how the size induces transformation among different polymorphic structures. Understanding the size-induced transformation among the different polymorphic structures is essential for widespread use of nanostructured materials in technological applications. Herein, we report water adsorption and high-temperature solution calorimetry experiments on a set of samples of single-phase monoclinic zirconia with different surface areas. Essential to the success of the study has been the use of a new ternary water-in-oil/water liquid solvothermal method that allows the preparation of monoclinic zirconia nanoparticles with a broad range of (BET) Brunauer,Emmett,Teller surface area values. Thus, the surface enthalpy for anhydrous monoclinic zirconia is reported for the first time, while that for the hydrous surface is a significant improvement over the previously reported value. Combining these data with previously published surface enthalpy for nanocrystalline tetragonal zirconia, we have calculated the stability crossovers between monoclinic and tetragonal phases to take place at a particle size of 28 ± 6 nm for hydrous zirconia and 34 ± 5 nm for anhydrous zirconia. Below these particle sizes, tetragonal hydrous and anhydrous phases of zirconia become thermodynamically stable. These results are within the margin of the theoretical estimation and confirm the importance of the presence of water vapor on the transformation of nanostructured materials. [source] Synthesis, Characterization, and In Vitro Bioactivity of Sol-Gel-Derived Zn, Mg, and Zn-Mg Co-Doped Bioactive GlassesCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 7 2010M. Erol Abstract Bioactive glasses in the systems CaO-SiO2 -P2O5 -ZnO, CaO-SiO2 -P2O5 -MgO, and CaO-SiO2 -P2O5 -MgO-ZnO were prepared and characterized. Bioactive glass powders were produced by the sol-gel method. The prepared bioactive glass powders were immersed in a simulated body fluid (SBF) for periods of up to 28,days at 310,K to investigate the bioactivity of the produced samples. Inductively coupled plasma (ICP) and ultraviolet (UV) spectroscopic techniques were used to detect changes in the SBF composition. X-Ray diffraction (XRD) was utilized to recognize and confirm the formation of a hydroxyapatite (HA) layer on the bioactive glass powders. Microstructural characterizations of the bioactive glass samples were investigated by scanning electron microscopy (SEM) techniques. Density, porosity, and surface area values of bioactive glass powders were also determined in order to characterize the textural properties of the samples. The results revealed the growth of an HA layer on the surface of the bioactive glass samples. MgO in the glass sample increases the rate of formation of an HA layer while ZnO in the glass slows it down. [source] | |||||||||||||