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Formation Process (formation + process)
Kinds of Formation Process Selected AbstractsFormation Process and Microwave Dielectric Properties of the R2V2O7 (R=Ba, Sr, and Ca) CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009Mi-Ri Joung Formation process and microwave dielectric properties of the R2V2O7 (R=Ba, Sr, and Ca) ceramics were investigated. Transient RV2O6 phases, which were formed at 300°,500°C by the reaction of RCO3 and V2O5, interacted with remnant RCO3 to form the homogeneous triclinic R2V2O7 phases at 600°,700°C. The Sr2V2O7 and Ca2V2O7 ceramics sintered at 1000° and 950°C, respectively, for 10 h showed a dense microstructure with the microwave dielectric properties of ,r=10.4,12.1, Q×f=15 200,19 520 GHz, and ,f=,30.9,34.8 ppm/°C. However, the Ba2V2O7 ceramic was well sintered at 900°C for 10 h and it showed the good microwave dielectric properties of ,r=10.1, Q×f=51 630 GHz, and ,f=,26.5 ppm/°C. [source] Explaining the 2005 Coalition Formation Process in Germany: A Comparison of Power Index and Median Legislator ApproachesPOLITICS, Issue 3 2006Charles Lees The article uses data from the 2005 German Bundestag elections to test the power index (PI) and median legislator (ML) models of coalition formation. The article finds that, while the PI approach is successful in predicting the real-world formation of a Grand Coalition after the election, neither model is sufficient to explain the outcome of the coalition formation process. Nevertheless, the article argues that such formal models are useful in identifying ,crucial cases' and in eliminating irrelevant data from explanations. The article concludes by suggesting some methodological routes through which formal models can be harnessed to culturally sensitive, inductive research. [source] Cultural Site Formation Processes in Maritime Archaeology: Disaster Response, Salvage and Muckelroy 30 Years onINTERNATIONAL JOURNAL OF NAUTICAL ARCHAEOLOGY, Issue 1 2006Martin Gibbs Thirty years after Muckelroy's seminal 1976 paper on shipwreck site formation, research on the cultural processes which contribute to the creation and modification of shipwrecks remains limited. It is proposed that by adopting a process-oriented framework, we can integrate and synthesize the documentary, oral and archaeological evidence of human response to shipwreck into a structure which parallels the physical progress of the disaster. Possible cultural responses to shipwreck are considered, from pre-voyage planning through to post-impact salvage, including physical correlations potentially visible in the archaeological record. © 2006 The Author [source] Positron Lifetime Study of the Crystal Evolution and Defect Formation Processes in a Scintillating GlassJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 10 2009Jiaxiang Nie The crystal evolution and defect formation in scintillating glasses as a consequence of thermal annealing were studied by annihilation lifetime spectroscopy and UV-Vis absorption spectroscopy. The annihilation lifetime spectra and UV-Vis spectra were recorded on glass 50SiO2,45ZnO,5BaF2 before and after annealing at 580°C for 16, 32, and 48 h, respectively. The results show that the three lifetime components (,1, ,2, and ,3) and the corresponding intensities (I1, I2, and I3) change systematically with increasing annealing time. This reflects the crystal evolution and defect formation in the glass matrix. The continued crystal evolution was also revealed by the UV-Vis spectra, as the absorption edge of the material shifted to a lower energy with prolonged annealing. [source] Experimental and Numerical Studies of Fe2O3 Particle Formation Processes in a Flat Flame BurnerCHEMICAL ENGINEERING & TECHNOLOGY (CET), Issue 6 2007M. Beck Abstract Particle formation processes are of interest for many industrial applications. This work focuses on investigating Fe2O3 particle formation. The particles form during thermal decomposition of an iron chloride solution in so-called spray roasting reactors. To analyze the reaction process, a laboratory reactor was designed which reproduces the conditions required for a systematic study of the particle formation process. Furthermore, a simplified particle conversion model was developed to simulate the realistic geometries and particle numbers on an industrial scale by CFD codes. [source] Formation process of three-dimensional arrays from silica spheresAICHE JOURNAL, Issue 5 2003Keiji Ishikawa Elucidating the formation process of 3-D arrays from submicrometer-sized particles is a key to creating an optimal fabrication process of photonic crystals. In this research, the spontaneous sedimentation of silica spheres is imaged by in situ confocal laser scanning microscopy, and the dynamics is studied. When the pH is 7.0 and 10, the rate of the formation process of a hexagonal structure is attributed to the transport of spheres in the early stage of precipitation, and can be reproduced by a simple equation for Langmuir-type adsorption, ignoring the desorption part. In a later stage, however, the rate becomes smaller. In the first layer, even after drying, the nearest two spheres are separated, while maintaining a hexagonal structure. From the results, the formation process of three-dimensional arrays from silica spheres is illustrated. [source] Formation Process and Microwave Dielectric Properties of the R2V2O7 (R=Ba, Sr, and Ca) CeramicsJOURNAL OF THE AMERICAN CERAMIC SOCIETY, Issue 12 2009Mi-Ri Joung Formation process and microwave dielectric properties of the R2V2O7 (R=Ba, Sr, and Ca) ceramics were investigated. Transient RV2O6 phases, which were formed at 300°,500°C by the reaction of RCO3 and V2O5, interacted with remnant RCO3 to form the homogeneous triclinic R2V2O7 phases at 600°,700°C. The Sr2V2O7 and Ca2V2O7 ceramics sintered at 1000° and 950°C, respectively, for 10 h showed a dense microstructure with the microwave dielectric properties of ,r=10.4,12.1, Q×f=15 200,19 520 GHz, and ,f=,30.9,34.8 ppm/°C. However, the Ba2V2O7 ceramic was well sintered at 900°C for 10 h and it showed the good microwave dielectric properties of ,r=10.1, Q×f=51 630 GHz, and ,f=,26.5 ppm/°C. [source] Formation process and preservation of a natural electronic archivePROCEEDINGS OF THE AMERICAN SOCIETY FOR INFORMATION SCIENCE & TECHNOLOGY (ELECTRONIC), Issue 1 2008Maria Esteva This paper presents a case of formation process study and preservation of the digital archive of a private organization. The archive was created in the late 1980's and maintained until 2005. The study was prompted by the archive's creators concerns about the resources involved, and the need to preserve their electronic records and systems vis-à-vis the presence of the signed and sealed paper documents. The approach used to study the digital archive was to consider it akin to an archaeological site. A formation process study of the archive's components was conducted using interview methods; primary and secondary sources; and metadata extraction, file viewers, and file transformation software. The study revealed information about the technical and social contexts involved in the archives' formation, and how its creators used it and valued it over time. The results informed the design of a preservation strategy aimed at maintaining the archives' integrity and authenticity and continuing documentation of its evolution. The attributes characterizing the archive led to the development of the concept of natural electronic archive. [source] Formation processes at the Ohalo II submerged prehistoric campsite, Israel, inferred from soil micromorphology and magnetic susceptibility studiesGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 4 2003Alexander Tsatskin Soil-geomorphic analysis coupled with micromorphology, SEM/EDS, magnetic susceptibility, and conventional sedimentological studies allowed us to reconstruct the site formation history and validate the archaeologically observed variability of human activities in the prehistoric camp of Ohalo II (19.5 ka B.P.), Sea of Galilee, Israel. The cultural layers rest upon the Late Pleistocene Lake Lisan deposits that accumulated under conditions of changing water supply and increasing rate of sedimentation from deep-water varvelike deposits to basalt-derived, near-shore sandy lacustrine deposits. Intermittent occupation is recorded in some localities, indicating short-term inundation episodes, which led to partial truncation and deformation of the sediments, primarily in the eastern lakeward part of the site. On the elevated, landward positions, incipient soils with strongly bioturbated profiles formed. Micromorphology demonstrates that intentional flooring was applied within the remains of brush huts, where millimeter-sized, horizontally organized burnt and unheated vegetal tissues were likely to have been placed upon the compacted ground. In fireplaces, the cultural deposits in thin sections are composed of strongly mixed, abundant wood charcoal, ashes, and fishbone remains. Post-depositional alterations were controlled by intermittent inundation of the site and salinization, which induced gypsum and pyrite deposition, primarily along decayed roots, and eventual pyrite oxidation. Accumulation of sodium and chlorine in the post-occupation deposits is likely to have occurred because of discharge of saline groundwater. Although only suggestive at this stage of research, the conclusions drawn from magnetic susceptibility parameters of archaeologically related deposits at Ohalo II fit well with the micromorphological reconstructions and provide new information on the Late Pleistocene evolution of the Lake Lisan/Sea of Galilee fluctuating system. © 2003 Wiley Periodicals, Inc. [source] Void formation in the Cu layer during thermal treatment of SiNx/Cu/Ta73Si27/SiO2/Si systemsCRYSTAL RESEARCH AND TECHNOLOGY, Issue 1-2 2005R. Hübner Abstract The thermal stability of a SiNx passivation layer and its influence on the annealing behavior of an amorphous Ta73Si27 diffusion barrier deposited between copper and SiO2 were analyzed by X-ray diffraction, glow discharge optical emission spectroscopy, Auger electron spectroscopy, scanning electron microscopy, and transmission electron microscopy. During heat treatment at a temperature Tan = 500 °C, diffusion of Cu atoms out of the Cu metallization into the SiNx passivation occurs. The Cu diffusion intensifies with increasing annealing temperature and annealing time and seems to be a necessary precondition for a defect formation process observed within the Cu metallization. Depending on the chemical composition of the SiNx/Cu interface, voids in the ,m-range can be formed within the Cu film. Compared to an unpassivated sample, heat treatment leads to a reduced diffusion of Ta atoms from the barrier through the copper into the SiNx/Cu interface. The barrier crystallization process into Ta5Si3 occurring during annealing at Tan = 600 °C is principally not affected by the presence of a SiNx passivation. (© 2005 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Probabilities as Similarity-Weighted FrequenciesECONOMETRICA, Issue 4 2005Antoine Billot A decision maker is asked to express her beliefs by assigning probabilities to certain possible states. We focus on the relationship between her database and her beliefs. We show that if beliefs given a union of two databases are a convex combination of beliefs given each of the databases, the belief formation process follows a simple formula: beliefs are a similarity-weighted average of the beliefs induced by each past case. [source] A Structural Model of Government FormationECONOMETRICA, Issue 1 2003Daniel Diermeier In this paper we estimate a bargaining model of government formation in parliamentary democracies. We use the estimated structural model to conduct constitutional experiments aimed at evaluating the impact of institutional features of the political environment on the duration of the government formation process, the type of coalitions that form, and their relative stability. [source] Small Molecule-Controlled Spontaneous Growth of Rose-Like Se Crystals at Room TemperatureEUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 7 2008Da-Wei Deng Abstract The spontaneous growth of rose-like Se crystals in aqueous solutions at room temperature is reported. The formation of rose-like Se crystals is based on the oxidation of Na2Se in the presence of thioglycerol solution at pH = 11 in a dark ambient atmosphere. In alkaline solutions, the growth evolution of rose-like Se crystals with aging time was followed by scanning electron microscopy (SEM), and an interesting formation process from initial Se monomers to amorphous Se (a-Se) spheres, and to the final rose-like complex structures of Se crystals was observed. Seven kinds of small molecules with different structures, including 1-thioglycerol (TG), mercaptamine (MA), L -cysteine (L -cys), 3-mercaptopropionic acid (MPA), thioglycolic acid (TGA), glycerol (GLY), and L -serine (L -ser), were used to manipulate the growth of Se crystals. The experimental results show that the structures of the small molecules play a key role in the growth of the Se crystals. The presence of thiols in the structure of the small molecules is favorable for the formation of the aggregates of Se crystals, and other termini, such as ,NH2, ,OH, or ,COO,, will determine whether the aggregates of Se crystals are made up of Se slices or Se prisms. These observations suggest that the ligand molecules have a crucial effect on the nucleation, monomers, and growth of nanocrystals. The selection of ligands can be extended to other important materials for further preparation of nanocrystals with desired shapes. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2008) [source] Spent media from cultures of environmental isolates of Escherichia coli can suppress the deficiency of biofilm formation under anoxic conditions of laboratory E. coli strainsFEMS MICROBIOLOGY ECOLOGY, Issue 3 2006Tecilli Cabellos-Avelar Abstract The prevailing lifestyle of bacteria is sessile and they attach to surfaces in structures known as biofilms. In Escherichia coli, as in many other bacteria, biofilms are formed at the air-liquid interface, suggesting that oxygen has a critical role in the biofilm formation process. It has been reported that anaerobically growing E. coli laboratory strains are unable to form biofilms even after 96 h of incubation on Luria Bertani (LB) medium. After analyzing 22 000 transposon-induced and 26 000 chemically-induced mutants we failed to isolate an E. coli laboratory strain with the ability to form biofilm under anaerobic growth conditions. Notably, seven strains from a collection of E. coli isolated from different hosts and the environment had the ability to form biofilm in the absence of oxygen. Interestingly, spent medium from cultures of one strain, Souza298, can promote biofilm formation of E. coli laboratory strains growing under anaerobic conditions. Our results led us to propose that laboratory E. coli strains do not release (or synthesize) a molecule needed for biofilm formation under anoxic conditions but that they bear all the required machinery needed for this process. [source] Polyphenylene Dendrimer-Templated In Situ Construction of Inorganic,Organic Hybrid Rice-Shaped ArchitecturesADVANCED FUNCTIONAL MATERIALS, Issue 1 2010Xiaoying Qi Abstract A novel dendrimer-templating method for the synthesis of CuO nanoparticles and the in situ construction of ordered inorganic,organic CuO,G2Td(COOH)16rice-shaped architectures (RSAs) with analogous monocrystalline structures are reported. The primary CuO nanoparticles are linked by the G2Td(COOH)16 dendrimer. This method provides a way to preserve the original properties of primary CuO nanoparticles in the ordered hybrid nanomaterials by using the 3D rigid polyphenylene dendrimer (G2Td(COOH)16) as a space isolation. The primary CuO nanoparticles with diameter of (6.3,±,0.4) nm are synthesized via four successive reaction steps starting from the rapid reduction of Cu(NO3)2 by using NaBH4 as reducer and G2Td(COOH)16 as surfactant. The obtained hybrid CuO,G2Td(COOH)16 RSA, formed in the last reaction step, possesses a crystal structure analogous to a monocrystal as observed by transmission electron microscopy(TEM). In particular, the formation process of the RSA is monitored by UV,vis, TEM, and X-ray diffraction. Small angle X-ray scattering and Fourier transform infrared spectroscopy are used to investigate the role of the dendrimer in the RSA formation process. The obtained results illuminate that Cu2+COO, coordination bonds play an indispensable role in bridging and dispersing the primary CuO nanoparticles to induce and maintain the hybrid RSA. More importantly, the RSA is retained through the Cu2+COO,coordination bonds even with HCl treatment, suggesting that the dendrimers and Cu2+ ions may form rice-shaped polymeric complexes which could template the assembly of CuO nanoparticles towards RSAs. This study highlights the feasibility and flexibility of employing the peculiar dendrimers to in-situ build up hybrid architectures which could further serve as templates, containers or nanoreactors for the synthesis of other nanomaterials. [source] Rewritable Holographic Structures Formed in Organic,Inorganic Hybrid Materials by Photothermal ProcessingADVANCED FUNCTIONAL MATERIALS, Issue 16 2009Hiroshi Kakiuchida Abstract Holographic and direct-written structures are fabricated in tin-doped silicophosphite thin plates containing rhodamine 6G dye by a photothermal process based on the principle of glass softening/frozen-in behavior. To be highly processable by photothermal treatment and stable at room temperature after processing, the intrinsic viscoelastic property is improved by increasing the crosslinking density of the network structure, and the photothermal conditions for efficient transfer of the irradiated photons to thermal phonons are explored. Then, the excellent rewritability and reliability of the fine processed structure are found by examining the writing/erasing repetition. Furthermore, the origins of the changes in refractive index due to photothermal treatment are classified into density change and photobleaching, and the dynamics of the formation process of holographic gratings are studied by measuring refractive index changes as functions of irradiation time and wavelength. As a result, it is found that the holographic structure consists of spatial modulation of the refractive index and the refractive index change results primarily from the change in the frozen structure, although there is a slight influence by photobleaching. [source] Archaeofacies analysis: Using depositional attributes to identify anthropic processes of deposition in a monumental shell mound of Santa Catarina State, southern BrazilGEOARCHAEOLOGY: AN INTERNATIONAL JOURNAL, Issue 3 2009Ximena S. Villagran In the coast of Santa Catarina State (southern Brazil), a large population of monumental shell mounds characterizes a highly dynamic coastal setting. In this paper, sedimentary facies analysis was adapted for description, sampling, and interpretation of shell mound complex and repetitive archaeostratigraphic successions. Archaeofacies identification in the field, according to depositional attributes, is tested by contrasting field description with multi-element chemical analyses, total carbon and nitrogen determinations, and micromorphological descriptions. Two vertical sequences at the black deposit of Jabuticabeira II shell mound were studied and preliminary results showed that: (1) depositional attributes are a reliable base for archaeofacies identification in the field, (2) the formation process of this site involved a sequence of anthropic depositional processes, where burned refuse was redeposited over the shell mound following a ritual construction pattern, and (3) the black deposit includes a double palimpsest that refers to provenance and meaning of mound construction material. © 2009 Wiley Periodicals, Inc. [source] Harvesting Excitons Via Two Parallel Channels for Efficient White Organic LEDs with Nearly 100% Internal Quantum Efficiency: Fabrication and Emission-Mechanism AnalysisADVANCED FUNCTIONAL MATERIALS, Issue 1 2009Qi Wang Abstract By incorporating two phosphorescent dyes, namely, iridium(III)[bis(4,6-difluorophenyl)-pyridinato-N,C2,]picolinate (FIrpic) for blue emission and bis(2-(9,9-diethyl-9H -fluoren-2-yl)-1-phenyl-1H -benzoimidazol-N,C3)iridium(acetylacetonate) ((fbi)2Ir(acac)) for orange emission, into a single-energy well-like emissive layer, an extremely high-efficiency white organic light-emitting diode (WOLED) with excellent color stability is demonstrated. This device can achieve a peak forward-viewing power efficiency of 42.5,lm,W,1, corresponding to an external quantum efficiency (EQE) of 19.3% and a current efficiency of 52.8,cd,A,1. Systematic studies of the dopants, host and dopant-doped host films in terms of photophysical properties (including absorption, photoluminescence, and excitation spectra), transient photoluminescence, current density,voltage characteristics, and temperature-dependent electroluminescence spectra are subsequently performed, from which it is concluded that the emission natures of FIrpic and (fbi)2Ir(acac) are, respectively, host,guest energy transfer and a direct exciton formation process. These two parallel pathways serve to channel the overall excitons to both dopants, greatly reducing unfavorable energy losses. It is noteworthy that the introduction of the multifunctional orange dopant (fbi)2Ir(acac) (serving as either hole-trapping site or electron-transporting channel) is essential to this concept as it can make an improved charge balance and broaden the recombination zone. Based on this unique working model, detailed studies of the slight color-shift in this WOLED are performed. It is quantitatively proven that the competition between hole trapping on orange-dopant sites and undisturbed hole transport across the emissive layer is the actual reason. Furthermore, a calculation of the fraction of trapped holes on (fbi)2Ir(acac) sites with voltage shows that the hole-trapping effect of the orange dopant is decreased with increasing drive voltage, leading to a reduction of orange emission. [source] Surfactant-Assisted Preparation of Novel Layered Silver Bromide-Based Inorganic/Organic Nanosheets by Pulsed Laser Ablation in Aqueous Media,ADVANCED FUNCTIONAL MATERIALS, Issue 17 2007C. He Abstract A novel layered AgBr-based inorganic/organic nanocomposite was prepared by pulsed laser ablation (PLA) of Ag in aqueous media in the presence of cetyltrimethylammonium bromide (CTAB), and the formation mechanism of two-dimensional nanosheet was discussed. TEM observations indicate that the obtained AgBr-based inorganic/organic nanocomposite possesses a well-defined two-dimensional shape and that the size of the nanosheet can be changed with the surfactant concentration in the solution. X-ray diffraction (XRD) pattern was composed of a series of peaks that could be indexed to (00l) reflections of a layered structure, and the basal spacing of 20.0,Å indicated that the surfactant was included between the AgBr interlayers in an interdigitated bilayer arrangement. In contrast, a layered inorganic/organic nanocomposite cannot be formed at a CTAB concentration lower than the critical micelle concentration (CMC). Based on our detailed investigation, we proposed the nanocomposite formation process, that is, that negatively charged inorganic AgBr was produced by a strong reaction between the ablated Ag species and the bromide ions, which are concurrently assembling with cationic surfactant molecules controlled by the charge-matching mechanism. [source] Observations of initiation stage of spontaneous vapor explosions for droplet scaleHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 1 2008Takeo Takashima Abstract In this study, the initiation stage of spontaneous vapor explosions generated by single droplets of molten tin submerged in water was investigated using a high- speed video camera operated with a reflected light system. Photographs of the formation process of vapor film, the process of vapor film disturbance, and the initiation process of the vapor explosions for different masses of molten tin and different nozzle diameters were obtained. The results demonstrate that partial thermal interaction between tin and water does not cause a vapor explosion with fragmentation. The vapor film disappears locally during the formation of the vapor film around the hot liquid droplet. Direct contact between the hot molten tin surface and water is thereby generated. However, the local disappearance of the vapor film does not progress and the vapor film is reconstructed. A vapor explosion occurs when the vapor film collapses at the local area of the bottom or edge of the disk-shaped droplet. © 2007 Wiley Periodicals, Inc. Heat Trans Asian Res, 37(1): 41,55, 2008; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.20185 [source] Molecular dynamics in the formation process of single-walled carbon nanotubesHEAT TRANSFER - ASIAN RESEARCH (FORMERLY HEAT TRANSFER-JAPANESE RESEARCH), Issue 8 2003Yasushi Shibuta Abstract The mechanism of the nucleation and formation of single-walled carbon nanotubes (SWNTs) was investigated using molecular dynamics simulations. When the initial state was chosen so that carbon and nickel atoms were randomly distributed in a simulation domain, the formation of a random cage structure made up of carbon atoms, which had a few nickel atoms inside it, was observed by 6 ns. The nickel atoms, which move inside or on the surface of the cage, were seen to be preventing the complete closure of the cage and its anneal into the fullerene structure. Further, in order to observe a longer time-scale growth process, the simulation cell was artificially shrunk by the progress of simulation so that collisions between precursor clusters were promoted to comply with the limitation in the calculation time. Collisions of the imperfect random-cage clusters led to an elongated tubular cage structure, which could be regarded as an initiation of SWNTs. The simulation results were compared with FT-ICR mass spectra of the positive clusters generated by a laser-vaporization supersonic-expansion cluster beam source. © 2003 Wiley Periodicals, Inc. Heat Trans Asian Res, 32(8): 690,699, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/htj.10123 [source] Microencapsulation of rosmarinic acid using polycaprolactone and various surfactantsINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 3 2010H.-J. Kim Synopsis Rosmarinic acid (RA) has a number of interesting biological activities, e.g. anti-viral, anti-bacterial, anti-inflammatory and antioxidant. The antioxidant activity of RA is stronger than that of vitamin E. Despite its strong antioxidant activity, it was limited to use in cosmetics because of the low water solubility, discolouration and chemical instability. The purpose of this study was to prepare RA-loaded polycaprolactone (PCL) microspheres using emulsion solvent evaporation method and characterize them with different surfactants used in the formation process. Finally, long-term stability of RA was evaluated in the cosmetic formulation. As a result, PCL microspheres were found to be spherical in shape, with zwitterionic surfactant-PCL particles being the smallest size distribution and highest entrapment efficiency of RA. Emulsions containing RA-loaded PCL microspheres showed a better long-term stability of the RA compared with those containing only RA. These results suggest that RA may be stably and efficiently encapsulated into polycaprolactone microspheres. Résumé Micro encapsulation d'acide rosmarinique utilisant la polycaprolactone et divers surfactants L'acide rosmarinique a un certain nombre d'activités biologiques intéressantes, par exemple antivirales, antibactériennes, anti-inflammatoires et antioxydantes. L'activité antioxydante de l'acide rosmarinique est plus puissante que celle de la vitamine E. Malgré sa forte activité antioxydante, son usage en cosmétique est limité en raison de sa faible solubilité dans l'eau, sa décoloration et son instabilité chimique. Le but de cette étude était de préparer des microsphères de PCL chargées d'acide rosmarinique par la méthode d'émulsification par d'évaporation de solvant et de les caractériser selon les différents surfactants utilisés dans le processus de fabrication. Enfin, la stabilitéà long terme de l'acide rosmarinique a étéévaluée dans la formulation cosmétique. Les microsphères PCL ont été trouvé de forme sphérique, avec les surfactants zwitterioniques, les particules PCL offrent une distribution de petites tailles et une efficacité de piégeage en acide rosmarinique la plus élevée. Les émulsions contenant des microsphères PCL chargées d'acide rosmarinique ont montréà long terme une meilleure stabilité en acide rosmarinique que celles contenant l'acide seul. Ces résultats suggèrent que l'acide rosmarinique peut être encapsulé de façon efficace et stable dans des microsphères de polycaprolactone. [source] Stratum corneum keratin structure, function and formation , a comprehensive reviewINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 6 2006L. Norlén Synopsis A comprehensive review on stratum corneum keratin organization, largely based on the recently published cubic rod-packing and membrane templating model [J. Invest. Dermatol., 123, 2004, 715], is presented. Keratin is the major non-aqueous component (wt/wt) of stratum corneum. As 90,100% of the stratum corneum water is thought to be located intracellularly one may presume that keratin also is a major factor (together with filaggrin-derived free amino acids) determining stratum corneum hydration level and water holding capacity. This water holding capacity depends in turn on the structural organization of the corneocyte keratin intermediate filament network. The cubic rod-packing model for the structure and function of the stratum corneum cell matrix postulates that corneocyte keratin filaments are arranged according to a cubic-like rod-packing symmetry. It is in accordance with the cryo-electron density pattern of the native corneocyte keratin matrix and could account for the swelling behaviour and the mechanical properties of mammalian stratum corneum. The membrane templating model for keratin dynamics and for the formation of the stratum corneum cell matrix postulates the presence in viable epidermal cellular space of a highly dynamic small lattice parameter (<30 nm) membrane structure with cubic-like symmetry, to which keratin is associated. It further proposes that membrane templating, rather than spontaneous self-assembly, is responsible for keratin intermediate filament formation and dynamics. It is in accordance with the cryo-electron density patterns of the native keratinocyte cytoplasmic space and could account for the characteristic features of the keratin network formation process, the dynamic properties of keratin intermediate filaments, the close lipid association of keratin, the insolubility in non-denaturating buffers and pronounced polymorphism of keratin assembled in vitro, and the measured reduction in cell-volume and hydration level between stratum granulosum and stratum corneum. Résumé, La kératine est le composant majeur anhydre de la couche cornée. Etant donné que l'on considère que 90 à 100% de l'eau de la couche cornée est localisée à l'intérieur des cellules, on peut penser que la kératine joue également un rôle important (en association avec les acides aminés libres dérivés de la filagrine) dans le niveau d'hydratation de la couche cornée et sa capacité de rétention de l'eau. Cette capacité de rétention de l'eau dépend elle-même de l'organization structurelle du réseau de filaments intermédiaires de la kératine des cornéocytes. Le modèle de cylindre en réseau cubique appliquéà la structure et aux fonctions de la matrice des cellules de la couche cornée stipule que les filaments de la kératine des cornéocytes sont disposés symétriquement, les paquets de fibrilles formant une structure cubique. Ceci est conforme au modèle de densité cryo-électronique de la matrice kératinique des cornéocytes natifs et pourrait expliquer le comportement de gonflement et les propriétés mécaniques de la couche cornée des mammifères. Le modèle d'assemblage membranaire appliquéà la dynamique de la kératine et à la formation de la matrice cellulaire du stratum cornéum postule la présence dans l'espace cellulaire viable de l'épiderme d'une structure membranaire hautement dynamique présentant un petit paramètre de maille (<30 nm) et une organization en forme de cube, à laquelle la kératine est associée. D'autre part, ce modèle suggère qu'un assemblage membranaire plutôt qu'un auto-assemblage spontané puisse être à l'origine de la formation des filaments intermédiaires de kératine et de leur dynamique. Ceci concorde avec les modèles de densité cryo-électronique du cytoplasme des kératinocytes natifs et pourrait expliquer les caractéristiques du processus de formation du réseau kératinique, les propriétés dynamiques des filaments intermédiaires de kératine, l'association de la kératine avec les lipides, l'insolubilité dans les tampons non dénaturants, le polymorphisme caractéristique de la kératine assemblée in vitro, ainsi que la diminution mesurée du volume cellulaire et du niveau d'hydratation entre le stratum granulosum et le stratum corneum. [source] Towards A Framework For The Comparative Analysis Of National Systems Of Skill FormationINTERNATIONAL JOURNAL OF TRAINING AND DEVELOPMENT, Issue 1 2000Johnny Sung This article builds on earlier attempts to develop a conceptual framework for the comparative analysis of training and skill formation systems. Following a critical review of previous approaches, the article identifies the main underlying relationships which shape national systems of skill formation. We identify four such ,models' of the skill formation process. These models show how such a framework can help us understand why societies have different approaches to the provision of education, training and skill formation and why there are significant differences in government policies towards training as they at tempt to respond to the challenges of globalisation. [source] Effect of the carboxylic acid monomer type on the emulsifier-free emulsion copolymerization of styrene and butadieneJOURNAL OF APPLIED POLYMER SCIENCE, Issue 2 2007Mahdi Abdollahi Abstract Carboxylated styrene,butadiene rubber latexes were prepared through the emulsifier-free emulsion copolymerization of styrene and butadiene with various carboxylic acid monomers. The effects of various carboxylic acid monomers on the particle formation process were investigated. The type of carboxylic acid monomer strongly affected the particle nucleation. The number of particles and thus the polymerization rate increased with the increasing hydrophobicity of the carboxylic acid monomers. There was a significant difference in the polymerization rate per particle. The results showed that particle nucleation and growth were dependent on the hydrophilic nature of the carboxylic acid monomers. The average particle diameter of the carboxylated styrene,butadiene rubber latexes in the dry state was obtained through some calculations using direct measurements of the average particle diameter in the monomer-swollen state by a dynamic light scattering technique. Several parameters, such as the polymerization rate, number of latex particles per unit of volume of the aqueous phase, and polymerization rate per particle, were calculated. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2007 [source] Characteristic modeling of the wear particle formation process from a tribological testing of polyethylene with controlled surface asperitiesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007Hsu-Wei Fang Abstract To study the ultra-high molecular weight polyethylene (UHMWPE) wear particles-induced osteolysis which leads to the failure of artificial joints, microfabricated surfaces with controlled asperities have been applied to generate narrowly distributed UHMWPE wear particles with various sizes and shapes. Our previous study further facilitated single wedge sliding tests to investigate the mechanism of the UHMWPE particle generation. In this study, the attempt was made to characterize the particle generation process into a mathematical model to predict particle volume with a given surface-texture dimensions and mechanical loading conditions. The particle-generation process is decomposed into two steps: (1) penetration of the cutting edge, and (2) lateral sliding of the cutting edge. By combining the indentation experimental data, the viscoelastic responses of UHMWPE was incorporated in the model. The effects of normal load, feature height, and cutting edge angle on the wear particle volume were illustrated from model predictions. Both experimental results and model predictions indicate the same trend of effects of surface-texture geometry and mechanical conditions on the volume of particles. The results of the model predictions are close to the experimental results of the particle generation. However, the particle volume predicted by the model is larger than the experimental results. It is believed that the reprocessing of the generated particles and viscoelastic recovery of UHMWPE in the experiments account for this difference. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 587,594, 2007 [source] Optimising the policy cost of market stabilisation: Which commodity matters most in Ethiopia?JOURNAL OF INTERNATIONAL DEVELOPMENT, Issue 3 2009Kindie Getnet Abstract Unprecedented food crop price spikes in recent years prompted the Ethiopian government to impose grain export ban and to distribute grain stocks as price stabilization strategies. Successful price stabilization and size of public spending for such programs depend, to a large extent, on the choice and targeting of stabilization strategies. In a situation where a single commodity plays a leadership role in the price dynamics of other crops, targeting intervention at such a commodity would provide a useful mechanism to reduce policy cost of price stabilization while achieving commodity-wide stabilization objectives. Using multiple cointegration analysis techniques to generate knowledge useful in targeting price stabilization intervention, this study investigates whether there is a single food crop in Ethiopia, among the three major ones (teff, wheat, and maize), with an exclusive price leadership role in the price formation process of the rest. The results show that maize price plays a leadership role in the dynamics of teff and wheat prices at all markets studied, except that of Addis Ababa teff market. Given the major evidence of a price leadership role of maize, it might be possible to achieve commodity-wide price stabilization objectives through targeting intervention on maize. Such targeted intervention may also prove efficiency in terms of reducing policy cost and public spending. Copyright © 2008 John Wiley & Sons, Ltd. [source] Physico-chemical characterisation of 99mTc-tin fluoride colloid agent used for labelling white cellsJOURNAL OF LABELLED COMPOUNDS AND RADIOPHARMACEUTICALS, Issue 6 2006Chris Tsopelas Abstract 99mTc,tin fluoride colloid is an agent used to label leucocytes, for the imaging and diagnosis of inflammatory conditions including Crohn's disease. Despite previous investigations, this radiolabelling agent is still poorly characterised. The aim of this work was to examine the process of formation and stability of 99mTc,tin fluoride colloid using mass spectrometry, membrane filtration and atomic absorption spectrophotometric techniques. Tin-oxide bonds in tin clusters were identified in the stannous fluoride reagent vial by mass spectrometry. From radioactive particle size distribution experiments, the facile disruption of radiocolloid particles with excess oxygen gas contrasted to the partial hydrolysis of Sn(II) during the formation process. Under the standard conditions, 10% of particles were determined as 1,3 µm, and this population coordinated 96% of the 99mTc added. Colloid particle formation and the reduction of 99mTc-pertechnetate is discussed. Sodium fluoride may optimise 1,3 µm radioactive particle size, by regulating particle growth. 99mTc,tin fluoride colloid is affected by positive or negative charge, as either Al, Mo ions or solid membranes, resulting in either coagulation and/or deflocculation of the particles. Copyright © 2006 John Wiley & Sons, Ltd. [source] Flocculation analysis and control system by laser diffractometry at industrial scaleAICHE JOURNAL, Issue 1 2008Mohamed Bizi Abstract The flocculant injection control system efficiency was evaluated on-site in an aggregate quarry, by means of laser diffraction and analysis of the size and texture of flocs. The configuration of the feed tank and the laser particle size measurement cell installed at the facility (280,000 t/year of aggregates) allowed characterization of flocs with particle size between 4.2 and 3473 ,m under hydrodynamic conditions that were highly favorable for the examination of large and very fragile flocs. Two days of analysis of the floc formation process along the path followed by the slurry showed that flocculation was optimal during standard operation of the facility when the flow rate of waste fines and concentrations of solids were close to those used to calibrate the flocculant injection control system. Conversely, when the concentration of solids in the flocculator feed slurry dropped by 57.3%, the flocculant dosing fluctuated during stabilization of the mechanism, the kinetics of flocculation slowed, the mean size of flocs arriving at the settling tank dropped by 69%, and the mode of smaller flocs shifted from 77.8 to 10.4 ,m in relation to normal operation. On-site analyses confirmed that the measurements made with laser diffraction (using a methodology developed in the laboratory) allow determination of the effects of conditioning on the characteristics of flocs in terms of particle size, porosity, density, and volume fraction in the slurry. Evolution of these characteristics according to the local parameters of conditioning (mean detention time, mean slurry velocity, and mean velocity gradient) provides a significant part of basic information necessary to a diagnosis of the operation of an industrial circuit of flocculation. © 2007 American Institute of Chemical Engineers AIChE J, 2008 [source] Formation process of three-dimensional arrays from silica spheresAICHE JOURNAL, Issue 5 2003Keiji Ishikawa Elucidating the formation process of 3-D arrays from submicrometer-sized particles is a key to creating an optimal fabrication process of photonic crystals. In this research, the spontaneous sedimentation of silica spheres is imaged by in situ confocal laser scanning microscopy, and the dynamics is studied. When the pH is 7.0 and 10, the rate of the formation process of a hexagonal structure is attributed to the transport of spheres in the early stage of precipitation, and can be reproduced by a simple equation for Langmuir-type adsorption, ignoring the desorption part. In a later stage, however, the rate becomes smaller. In the first layer, even after drying, the nearest two spheres are separated, while maintaining a hexagonal structure. From the results, the formation process of three-dimensional arrays from silica spheres is illustrated. [source] | ||||||||||||||||||||||||||||||||||