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Thomas N Blanton - One of the best experts on this subject based on the ideXlab platform.
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crystal structure determination of the silver carboxylate dimer ag o2c22h43 2 silver Behenate using powder x ray diffraction methods
Powder Diffraction, 2011Co-Authors: Thomas N Blanton, David R. Whitcomb, Scott T Misture, Manju Rajeswaran, Peter W Stephens, James A KadukAbstract:High-resolution powder X-ray diffraction has been used to determine the crystal structure of silver Behenate, [Ag(O2C(CH2)20CH3]2. Using CASTEP density functional plane wave pseudopotential techniques to obtain an optimized structural model, Rietveld refinement of the structure gives Rwp = 8.66%. The unit cell is triclinic, space group P1, with cell dimensions of a = 4.1769(2) A, b = 4.7218(2) A, c = 58.3385(1) A, α = 89.440(3)°, β = 89.634(3)°, γ = 75.854(1)°. The structure is characterized by an 8-membered ring dimer of Ag atoms and carboxyl groups with a fully extended all-trans configuration of the alkyl side chains. The dimers are joined by four-membered Ag-O rings creating a polymeric network, giving rise to one-dimensional chains along the b-axis. This structure is supported by EXAFS measurements of the local structure around the silver atoms and IR measurements.
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in situ high temperature x ray diffraction study of phase transformations in silver Behenate
Powder Diffraction, 2005Co-Authors: Thomas N Blanton, Swavek Zdzieszynski, Michael Nicholas, Scott T MistureAbstract:In situ high-temperature X-ray diffraction (XRD) data have been collected for silver Behenate, CH3(CH2)20COOAg. In the absence of development chemistry silver Behenate exhibits four phase transformations when heated from room temperature to 200 oC. Combining XRD and differential scanning calorimetry (DSC) results, the phase transformation temperatures and phase types have been determined. Type I, II, and III forms of silver Behenate are found to be crystalline phases, whereas Type IV and V forms are liquid crystal phases.
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characterization of silver image formation in a silver Behenate photothermographic imaging element using x ray diffraction techniques
Journal of Imaging Science and Technology, 2005Co-Authors: Thomas N Blanton, Mark Lelental, C L BarnesAbstract:The quantitative assessment of silver development efficiency and covering power in silver based imaging elements requires an accurate determination of the coverage of silver metal (Ag(0)) formed as a result of post-exposure image development. The thermographic and photothermographic imaging processes do not incorporate a silver source removal-fixing step. Therefore, it has been necessary to develop an analytical technique capable of providing a quantitative determination of the Ag(0) coverage in the presence of silver salts and complexes. An X-ray diffraction method has been developed that is based on the correlation between silver metal diffraction peak area intensity and silver-metal coverage present in the final image area. It has been demonstrated that this methodology may be used for the assessment of the development efficiency, covering power, and quantum efficiency in photothermographic, silver Behenate based, imaging elements. The use of X-ray diffraction techniques has been extended to characterization of crystallinity, morphology, and crystallite size of micro- and nano-silver Behenate particulates.
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in situ high temperature study of silver Behenate reduction to silver metal using synchrotron radiation
2002Co-Authors: Thomas N Blanton, Swavek Zdzieszynski, Mark Lelental, Scott T MistureAbstract:Silver Behenate is utilized in commercially available photothermographic imaging elements. The silver metal (Ag°) image formation in these imaging elements is based on the heat-induced reduction of the silver Behenate. The completed reduction process has historically been studied by conventional X-ray diffraction techniques. To enhance the understanding of the kinetics of silver metal formation, equipment and methods were developed allowing for in situ hightemperature monitoring of the AgBehenate → Ag° reduction process. To perform the necessary measurements a high-temperature sample stage and position sensitive detector were mounted on the X3B1 beam line powder diffractometer at the National Synchrotron Light Source, Brookhaven National Laboratories. The fraction of AgBehenate reduced and Ag° developed was obtained from the synchrotron data and it was determined that the reaction rates for both processes followed a second order transformation. The activation energy was derived from the reaction rate data and was found to be 216 kJ/mol for AgBehenate reduction and 156 kJ/mol for Ag° development.
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preparation of silver Behenate coatings to provide low to mid angle diffraction calibration
Journal of Applied Crystallography, 2000Co-Authors: Thomas N Blanton, C L Barnes, Mark LelentalAbstract:A method for the preparation of a well aligned silver Behenate sample is described. Multiple (0 0 l) diffraction peaks, (0 0 1) to (0 0 48), are easily observed using a conventional laboratory X-ray diffraction instrument.
Albrecht Wiedenmann - One of the best experts on this subject based on the ideXlab platform.
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application of silver Behenate powder for wavelength calibration of a sans instrument a comprehensive study of experimental setup variations and data processing techniques
Journal of Applied Crystallography, 1999Co-Authors: U. Keiderling, Ralph Gilles, Albrecht WiedenmannAbstract:Silver Behenate powder [CH3(CH2)20COOAg] is one of the very few materials featuring cold neutron Bragg reflections in the angular range of 4–26° (2θ) accessible to small-angle neutron scattering (SANS) instruments. These reflections can be analysed with Bragg's law to determine the wavelength of the primary beam produced by the monochromator of the SANS instrument. Compared with the usual time-of-flight (TOF) method for wavelength calibration, this method does not require any additional time-resolving equipment for the instrument. An extensive study has been performed to determine the optimum parameters for the experimental setup and for the data processing procedure. The results of wavelength calibrations using silver Behenate and TOF measurements are compared.
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Silver Behenate powder as a possible low-angle calibration standard for small-angle neutron scattering
Journal of Applied Crystallography, 1998Co-Authors: Ralph Gilles, U. Keiderling, Albrecht WiedenmannAbstract:Small-angle neutron scattering (SANS) is a transmission method working in the angular range 0.4–6° (2θ). In this paper, silver Behenate powder [CH3(CH2)20COOAg] (referred to as `AgBE'), one of the very few materials featuring Bragg reflections in the angular range accessible to SANS instruments, is suggested as a possible new SANS wavelength calibration standard. In the past, this powder has been successfully tested as a calibration standard in low-angle X-ray diffraction. Results of new SANS wavelength calibration measurements performed with AgBE and with the traditional method of time-of-flight measurements are presented and compared with low-angle X-ray diffraction measurements.
Eliana B Souto - One of the best experts on this subject based on the ideXlab platform.
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lopinavir loaded solid lipid nanoparticles sln for intestinal lymphatic targeting
European Journal of Pharmaceutical Sciences, 2011Co-Authors: M Aji R Alex, Eliana B Souto, A J Chacko, S JoseAbstract:Abstract The poor orally available lopinavir was successfully encapsulated in glyceryl Behenate based solid lipid nanoparticles (Lo-SLN) for its ultimate use to target intestinal lymphatic vessels in combined chemotherapy—the so-called Highly Active Anti-Retroviral Therapy (HAART). SLN with mean particle size of 230 nm (polydispersity index, PDI
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potential use of nanostructured lipid carriers for topical delivery of flurbiprofen
Journal of Pharmaceutical Sciences, 2011Co-Authors: E Gonzalezmira, Eliana B Souto, S Nikolic, M L Garcia, M A Egea, Ana C CalpenaAbstract:ABSTRACT The potential use of nanostructured lipid carriers (NLC) composed of a fatty acid [stearic acid (SA)] or a triglyceride (glyceryl Behenate) as solid lipids, and a mixture of medium chain triglycerides and castor oil as liquid lipids, for skin administration of flurbiprofen (FB), has been explored. Two different optimized NLC formulations (FB-SANLC based on SA vs. FB-C888NLC based on glyceryl Behenate), with respect to the morphometrical properties (particle size and polydispersity index) and the entrapment efficiency, were used in this study. The ex vivo permeation profiles of FB-C888NLC, FB-SANLC and conventional FB solution were evaluated using human skin. An improved FB permeation was observed when the drug was delivered by skin application of FB-C888NLC, attributed to the particle size and matrix crystallinity. The differential scanning calorimetry and X-ray diffraction studies suggested major polymorphic transitions in the lipid matrix of FB-C888NLC. A good correlation between polymorphic transitions and increased drug permeation was observed. However, both NLC dispersions showed a penetration-enhancing ratio (ER) higher than conventional FB solution. The in vitro and in vivo irritancy and local tolerability were assessed by running, respectively, the SKINTEX™ and Draize test. Both FB-C888NLC and FB-SANLC were classified as nonirritant.
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solid lipid nanoparticles sln effects of lipid composition on in vitro degradation and in vivo toxicity
Die Pharmazie, 2006Co-Authors: H Weyhers, S Ehlers, H Hahn, Eliana B Souto, Rainer H MullerAbstract:Solid lipid nanoparticles (SLN) composed of two different lipid matrices were produced to assess their in vivo toxicity in mice. Matrix substances were (i) Compritol (glycerol Behenate), a physiological lipid with GRAS status (generally recognized as safe [FDA]), and (ii) cetyl palmitate, a less physiological compound. Physicochemical data proved the suitability of SLN batches for intravenous administration. To assess the in vivo toxicity of produced batches, 400 microl SLN dispersion (lipid content 10% [m/m]) were administered to mice via a bolus injection for six times within a period of 20 days (high dose administration). Additionally, a multiple low dose administration was performed with Compritol-SLN as well (200 microl SLN dispersion, lipid content 2.5% [m/m]). Hepatic and splenic tissues were analysed histologically. In vivo results were dependent on the lipid matrix, as well as on the dose administered. For cetyl palmitate containing SLN no pathological results were obtained, while high dosed Compritol containing formulations led to accumulation of the lipid in liver and spleen and subsequently to pathological alterations. These alterations were found to be partially reversible within six weeks after completing intravenous administration. Liver architecture was nearly recovered. In contrast, low dosed Compritol SLN were well tolerated. Lipid accumulation and pathological alterations of high dosed Compritol SLN were attributed to the slow degradation of the Compritol matrix which could be shown by performing in vitro studies in human plasma.
Ralph Gilles - One of the best experts on this subject based on the ideXlab platform.
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application of silver Behenate powder for wavelength calibration of a sans instrument a comprehensive study of experimental setup variations and data processing techniques
Journal of Applied Crystallography, 1999Co-Authors: U. Keiderling, Ralph Gilles, Albrecht WiedenmannAbstract:Silver Behenate powder [CH3(CH2)20COOAg] is one of the very few materials featuring cold neutron Bragg reflections in the angular range of 4–26° (2θ) accessible to small-angle neutron scattering (SANS) instruments. These reflections can be analysed with Bragg's law to determine the wavelength of the primary beam produced by the monochromator of the SANS instrument. Compared with the usual time-of-flight (TOF) method for wavelength calibration, this method does not require any additional time-resolving equipment for the instrument. An extensive study has been performed to determine the optimum parameters for the experimental setup and for the data processing procedure. The results of wavelength calibrations using silver Behenate and TOF measurements are compared.
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Silver Behenate powder as a possible low-angle calibration standard for small-angle neutron scattering
Journal of Applied Crystallography, 1998Co-Authors: Ralph Gilles, U. Keiderling, Albrecht WiedenmannAbstract:Small-angle neutron scattering (SANS) is a transmission method working in the angular range 0.4–6° (2θ). In this paper, silver Behenate powder [CH3(CH2)20COOAg] (referred to as `AgBE'), one of the very few materials featuring Bragg reflections in the angular range accessible to SANS instruments, is suggested as a possible new SANS wavelength calibration standard. In the past, this powder has been successfully tested as a calibration standard in low-angle X-ray diffraction. Results of new SANS wavelength calibration measurements performed with AgBE and with the traditional method of time-of-flight measurements are presented and compared with low-angle X-ray diffraction measurements.
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jcpds international centre for diffraction data round robin study of silver Behenate a possible low angle x ray diffraction calibration standard
Powder Diffraction, 1995Co-Authors: Thomas N Blanton, Ralph Gilles, T C Huang, Hideo Toraya, Camden R Hubbard, S Robie, D Louer, H Gobel, G Will, T RafteryAbstract:A task group of the JCPDS—International Center for Diffraction Data (ICDD) was established with the charge of investigating the use of silver Behenate, CH 3 (CH 2 ) 20 COO·Ag, as a possible low-angle calibration standard for powder diffraction applications. Utilizing several data collection and analysis techniques, long-period spacing ( d 001 ) values with a range of 58.219–58.480 A were obtained. Using the same collected data and one data analysis refinement calculation method resulted in dm values with a range of 58.303–58.425 A. Data collected using a silicon internal standard and the same singular data analysis calculation method provided d 001 values with a range of 58.363–58.381 A.
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jcpds international centre for diffraction data low angle powder diffraction study of silver Behenate
Advances in x-ray analysis, 1994Co-Authors: T Blanton, Ralph Gilles, T C Huang, Hideo Toraya, Camden R Hubbard, S Robie, D Louer, H Gobel, G Will, T RafteryAbstract:As a result of interest in the characterization of materials with large d-spacings and layer periodicities, it has become necessary to develop a low-angle diffraction material which has well-defined diffraction peaks down to very small 2{theta} angles. The use of silver Behenate, CH{sub 3}(CH{sub 2}){sub 20}COO-Ag, was introduced by one of the authors (TB) at the 1991 International Center for Diffraction Data (ICDD) Annual Meeting and was shown to have a set of well-defined (00l) diffraction peaks down to 1.5{degrees} 2{theta} when using CuK{alpha} radiation. The silver Behenate diffraction peaks were observed to be slightly asymmetric with relatively long tails at the low angle side of the peaks. The average crystallite size along the c-axis was estimated using the Scherrer equation and was found to be 900 {Angstrom}. A task group of the JCPDS-ICDD Data Collection and Analysis Subcommittee was established with the charge of investigating the use of silver Behenate as a possible low-angle calibration material for diffraction applications. Utilizing several data collection and data analysis techniques, d{sub 001} long-period spacings in the range of 58.219-58.480 {Angstrom} were obtained. Using the same collected data and one data analysis, refinement calculation method resulted in long-period spacings with a range ofmore » 58.303-58.425 {Angstrom}. Data collected using a silicon internal standard and the same singular data analysis calculation method provided d{sub 001} values with a range of 58.363-58.381 {Angstrom}. The formation of a full-range 2{theta} diffraction sample was also investigated. Silver Behenate and inorganic powders were mixed with an epoxy binder to form a permanent sample which provides diffraction peaks over the entire 2{theta} range of a powder diffractometer. 8 refs., 3 figs., 1 tab.« less
Jordan G Petrov - One of the best experts on this subject based on the ideXlab platform.
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langmuir monolayers with fluorinated groups in the hydrophilic head 2 morphology and molecular structure of trifluoroethyl Behenate and ethyl Behenate monolayers
Langmuir, 2001Co-Authors: Jordan G Petrov, Gerald Brezesinski, Nadejda Krasteva, H MohwaldAbstract:Morphology and molecular structure of Langmuir monolayers of trifluoroethyl Behenate (TFEB) and ethyl Behenate (EB) were investigated via Brewster angle microscopy and grazing incidence X-ray diffraction (GIXD) at the air−water interface. When spread at 60 A2/molecule, both substances form islands of a condensed phase. At smaller areas, they organize in “archipelago structures” with compact sections and 2D suspensions of microcrystals floating in streams on the free water surface. The microcrystals that are close to the “coastlines” adhere to the compact monolayer. The latter contains dark areas (“lakes”) that are being closed under compression. At expansion, the compact monolayers disintegrate to the same archipelagos but the microcrystals are now located mainly along the coastlines. Such mechanism of growth and disintegration of the apparently compact TFEB and EB films suggests a polycrystalline structure. Different friction at the microcrystal boundaries could be responsible for different compressional...
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langmuir monolayers with fluorinated groups in the hydrophilic head 1 comparison of trifluoroethyl Behenate and ethyl Behenate monolayers molecular models mechanical properties stability
Langmuir, 2000Co-Authors: Jordan G Petrov, E E Polymeropoulos, H MohwaldAbstract:In a series of three related papers we compare mechanical properties and stability, morphology and structure, and electrostatic potential and ellipsometric thickness of trifluoroethyl Behenate (TFEB) and ethyl Behenate (EB) Langmuir monolayers. The aim of these papers is to study the effect of fluorination of a methyl group in the hydrophilic head on monolayer properties and structure. In the present Part 1 we show that trifluoroethyl ester forms significantly more unstable films with higher compressibility (lower compressional modulus) than the unsubstituted ethyl ester. Both TFEB and EB surface pressure−area isotherms show compression−expansion hysteresis, but this hysteresis is larger for the fluorinated ester. The surface pressure−area loop of TFEB is shifted to larger molecular areas as compared to EB and gives larger limiting molecular areas at zero compression. This points to different volumes and/or conformations of the fluorinated and nonsubstituted hydrophilic heads. Maps of molecular lipophilic...
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langmuir monolayers with a cf group in the hydrophilic head monolayers of trifluoroethyl ester of behenic acid
The Journal of Physical Chemistry, 1996Co-Authors: Jordan G Petrov, Helmuth MohwaldAbstract:Insoluble monolayers of the trifluoroethyl ester of behenic acid possessing a terminal CF3 group of the ester radical of the hydrophilic head are studied at the air−water interface. The surface pressure−area isotherms show a formation of condensed monolayer. The relatively low collapse pressure and significant reduction with time of the molecular area at constant surface pressure illustrate considerable decrease of the monolayer stability when compared to the one of the ethyl Behenate monolayers. The CF3 terminal of the ester radical reverses the sign of the surface potential and the vertical dipole moment component; negative values of ΔV and μ⊥ are obtained for the trifluoroethyl Behenate monolayer, while positive values of ΔV and μ⊥ are characteristic for other neutral behenyl chain derivatives such as methyl and ethyl Behenate, behenyl alcohol, undissociated behenic acid, and behenyl amine. This fact demonstrates the determining role of the hydrophilic head for these electrostatic properties. The new r...