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Structural Aspects (structural + aspect)
Selected AbstractsOrganizing for Radical Innovation: An Exploratory Study of the Structural Aspects of RI Management Systems in Large Established FirmsTHE JOURNAL OF PRODUCT INNOVATION MANAGEMENT, Issue 6 2006Gina Colarelli O'Connor To escape the intense competition of today's global economy, large established organizations seek growth options beyond conventional new product development that leads to incremental changes in current product lines. Radical innovation (RI) is one such pathway, which results in organically driven growth through the creation of whole new lines of business that bring new to the world performance features to the market and may result in the creation of entirely new markets. Yet success is elusive, as many have experienced and scholars have documented. This article reports results of a three-year, longitudinal study of 12 large established firms that have declared a strategic intent to evolve their RI capabilities. In contrast to other academic research that has analyzed specific projects to understand management practices appropriate for RI, the present research reported explores the evolution of management systems for enabling radical innovation to occur repeatedly in large firms and reports on one aspect of this management system: organizational structures for enabling and nurturing RI. To consider organizational structure as a venue for capability development is new in the management of innovation and dynamic capabilities literatures. Conventional wisdom holds that RIs should be incubated outside the company and assimilated once they have gained traction in the marketplace. Numerous experiments with organizational structures were observed that instead work to manage the interfaces between the RI management system and the mother organization. These structures are described here, and insights are drawn out regarding radical innovation competency requirements, transition challenges, senior leadership mandates, and business-unit ambidexterity. The centerpiece of this research is the explication of the Discovery,Incubation,Acceleration framework, which details three sets of necessary, though not sufficient competencies, for building an RI capability. [source] Synthesis, Structural Aspects and Cytotoxicity of the Natural Cyclopeptides Yunnanins A, C and Phakellistatins 1, 10.CHEMINFORM, Issue 9 2004Assunta Napolitano No abstract is available for this article. [source] A Realist Theory of HegemonyJOURNAL FOR THE THEORY OF SOCIAL BEHAVIOUR, Issue 2 2000Jonathan Joseph A new approach to understanding hegemony is developed based on the method of critical realism. Breaking from the traditional interpretations that emphasise inter-subjective, superstructural and cultural aspects of hegemony, this article looks at hegemony's structural context and the conditions for its possibility. A realist conception of hegemony relates hegemonic projects to structural reproduction and transformation via Bhaskar's transformational model of social activity. In doing so this model is itself modified to incorporate hegemony as the political moment of social reproduction. A distinction is made between hegemony in its structural aspect, and specific hegemonic projects as emergent possibilities. [source] New Perspectives on the Correlation of SAT Scores, High School Grades, and Socioeconomic FactorsJOURNAL OF EDUCATIONAL MEASUREMENT, Issue 1 2007Rebecca Zwick In studies of the SAT, correlations of SAT scores, high school grades, and socioeconomic factors (SES) are usually obtained using a university as the unit of analysis. This approach obscures an important structural aspect of the data: The high school grades received by a given institution come from a large number of high schools, all of which have potentially different grading standards. SAT scores, on the other hand, can be assumed to have the same meaning across high schools. Our analyses of a large national sample show that, when pooled within-high-school analyses are applied, high school grades and class rank have larger correlations with family income and education than is evident in the results of typical analyses, and SAT scores have smaller associations with socioeconomic factors. SAT scores and high school grades, therefore, have more similar associations with SES than they do when only the usual across-high-school correlations are considered. [source] Impacts of a law fostering training development: Lessons from Quebec's experienceCANADIAN PUBLIC ADMINISTRATION/ADMINISTRATION PUBLIQUE DU CANADA, Issue 3 2007Jean Chrest In 1995, the Quebec government adopted a unique law in North America in this regard: An Act to Foster the Development of Manpower Training. The "1% Wage Bill Law" was intended to improve the qualifications, skills and performance of workers through training. This article investigates three impacts of this law: the level of investment by firms; the distributional aspect of the law in terms of its capacity to ensure a more equitable investment in training for the different categories of workers in firms; and, finally, the structural aspect in terms of establishing partnerships. From a theoretical perspective, the Quebec experience illustrates that, between the liberal approach and the institutionalist approach (market versus institutions), it is possible to observe a compromise being made by social actors with respect to the regulation process, which at the same time respects the decisional space of firms. Another observation relates to the complementary aspect of institutional forms in labour-market regulation and to the fundamental role of unions in partnershipbuilding. Sommaire: Depuis les années 1980, de nombreuses etudes au Canada ont révélé un faible degré de participation des entreprises à la formation et ont ainsi soulevé la question du rôle de la politique gouvemementale. En 1995, le gouvemement du Québec a adoptéà cet égard une loi unique en son genre en Amérique du Nord: une Loi fauorisant le de'veloppement de la formation de la main-d,,uvre. La G loi du 1 % de la masse salariale "visait à améliorer les qualifications, les competences et la performance des travailleuses et travailleurs grâce 5 la formation. Le présent article examine trois impacts de cette loi: le niveau d'investissement des entreprises; l'aspect répartition de la loi en termes de sa capacitéà s' assurer que des investissements plus équitables soient consacrés à la formation pour différentes catégories de travailleuses et travailleurs dans les entreprises; et enfin, l'aspect structurel pour ce qui est de l'établissement de partenariats. D'un point de vue théorique, l'expérience du Québec illustre qu'entre l'approche libérale et l'approche institutionnelle (marché contre institutions), il est possible d'observer un compromis de la part des acteurs sociaux en ce qui concerne le processus de réglementation, qui respecte en même temps l'espace décisionnel des entreprises. Une autre observation porte sur l'aspect complémentaire des formes institutionnelles dans la réglementation du marché du travail et sur le rôle fondamental des syndicats dans l,établissement de partenariats. [source] MMP-2 contributes to the development of the mouse ventral prostate by impacting epithelial growth and morphogenesisDEVELOPMENTAL DYNAMICS, Issue 9 2010Alexandre Bruni-Cardoso Abstract Epithelial growth, branching, and canalization are important morphogenetic events of the rodent ventral prostate (VP) that take place during the first postnatal week. In this study, we evaluated the effect of knocking out MMP-2 (MMP-2,/,), by examining developmental and structural aspects of the VP in MMP-2,/, mice. Neonate (day 6) MMP-2,/, mice showed fewer epithelial tips, a lower epithelial cell proliferation rate, and also reticulin fiber accumulation. The VP of adult MMP-2,/, mice showed lower relative weight, smaller epithelial and smooth-muscle cell volume, and a larger amount of thicker reticulin fibers. No differences in cell proliferation or apoptotic index were noted between adult MMP-2,/, and wild-type mice. MMP-9 was found in the adult MMP-2,/,, but not in the wild-type. In conclusion, MMP-2 function is essential for the epithelial morphogenesis of the mouse VP, and expression of MMP-9 is not sufficient for acquisition of the normal adult histology. Developmental Dynamics 239:2386,2392, 2010. © 2010 Wiley-Liss, Inc. [source] The Work-Family Interface: Differentiating Balance and FitFAMILY & CONSUMER SCIENCES RESEARCH JOURNAL, Issue 2 2004Maribeth C. Clarke Work-family fit has recently emerged in work and family literature, comparable to work-family balance in that it represents interactions between work and family and yet distinct because it precedes balance and other outcomes. This study explores the relationship between, predictive factors of, and interactive moderating effects of work-family fit and work-family balance. Data are from a survey of business graduate school alumni (n = 387). Findings indicate that fit and balance are two separate constructs. Fit is uniquely predicted by work hours, age, family income, and household labor satisfaction. Balance is uniquely predicted by frequency of family activities. Job satisfaction and marital satisfaction predicted both fit and balance. Analyses suggest that fit is based more on the structural aspects of work-family interactions, whereas balance appears to be based more on the psychological factors. Job satisfaction, marital satisfaction, and frequency of family activities moderated the relationship between fit and balance. [source] Isolation and X-Ray Structures of Reactive Intermediates of Organocatalysis with Diphenylprolinol Ethers and with ImidazolidinonesHELVETICA CHIMICA ACTA, Issue 11 20085-Repulsion, A Survey, Comparison with Computed Structures, the Geminal-Diaryl Effect at Work, with 1-Acyl-imidazolidinones: The Abstract Reaction of 2-phenylacetaldehyde with the Me3Si ether of diphenyl-prolinol, with removal of H2O, gives a crystalline enamine (1). The HBF4 salts of the MePh2Si ether of diphenyl-prolinol and of 2-(tert -butyl)-3-methyl- and 5-benzyl-2,2,3-trimethyl-1,3-imidazolidin-4-one react with cinnamaldehyde to give crystalline iminium salts 2, 3, and 4. Single crystals of the enamine and of two iminium salts, 2 and 3, were subjected to X-ray structure analysis (Figs.,1, 2, and 6), and a 2D-NMR spectrum of the third iminium salt was recorded (Fig.,7). The crystal and NMR structures confirm the commonly accepted, general structures of the two types of reactive intermediates in organocatalysis with the five-membered heterocycles, i.e., D, E (Scheme,2). Fine details of the crystal structures are discussed in view of the observed stereoselectivities of the corresponding reactions with electrophiles and nucleophiles. The structures 1 and 2 are compared with those of other diphenyl-prolinol derivatives (from the Cambridge File CSD; Table,1) and discussed in connection with other reagents and ligands, containing geminal diaryl groups and being used in enantioselective synthesis (Fig.,4). The iminium ions 3 and 4 are compared with N -acylated imidazolidinones F and G (Figs.,9, 12, and 13, and Table,3), and common structural aspects such as minimalization of 1,5-repulsion (the ,A1,3 -effect'), are discussed. The crystal structures of the simple diphenyl-prolinol,HBF4 salt (Fig.,3) and of Boc- and benzoyl-(tert -butyl)methyl-imidazolidinone (Boc-BMI and Bz-BMI, resp.; Figs.,10 and 11) are also reported. Finally, the crystal structures are compared with previously published theoretical structures, which were obtained from high-level-of-theory DFT calculations (Figs.,5 and 8, and Table,2). Delicate details including pyramidalization of trigonal N-atoms, distortions around iminium CN bonds, shielding of diastereotopic faces, and the , -interaction between a benzene ring and a Me group match so well with, and were actually predicting the experimental results that the question may seem appropriate, whether one will soon start considering to carry out such calculations before going to the laboratory for experimental optimizations. [source] Structure,Property Relation of SrTiO3/LaAlO3 InterfacesADVANCED MATERIALS, Issue 17 2009Mark Huijben Abstract A large variety of transport properties have been observed at the interface between the insulating oxides SrTiO3 and LaAlO3 such as insulation, 2D interface metallicity, 3D bulk metallicity, magnetic scattering, and superconductivity. The relation between the structure and the properties of the SrTiO3/LaAlO3 interface can be explained in a meaningful way by taking into account the relative contribution of three structural aspects: oxygen vacancies, structural deformations (including cation disorder), and electronic interface reconstruction. The emerging phase diagram is much richer than for related bulk oxides due to the occurrence of interface electronic reconstruction. The observation of this interface phenomenon is a display of recent advances in thin film deposition and characterization techniques, and provides an extension to the range of exceptional electronic properties of complex oxides. [source] The restoration of ecological interactions: plant,pollinator networks on ancient and restored heathlandsJOURNAL OF APPLIED ECOLOGY, Issue 3 2008Mikael Lytzau Forup Summary 1Attempts to restore damaged ecosystems usually emphasize structural aspects of biodiversity, such as species richness and abundance. An alternative is to emphasize functional aspects, such as patterns of interaction between species. Pollination is a ubiquitous interaction between plants and animals. Patterns in plant,pollinator interactions can be analysed with a food web or complex-systems approach and comparing pollination webs between restored and reference sites can be used to test whether ecological restoration has taken place. 2Using an ecological network approach, we compared plant,pollinator interactions on four pairs of restored and ancient heathlands 11 and 14 years following initiation of restoration management. We used the network data to test whether visitation by pollinators had been restored and we calculated pollinator importance indices for each insect species on the eight sites. Finally, we compared the robustness of the restored and ancient networks to species loss. 3Plant and pollinator communities were established successfully on the restored sites. There was little evidence of movement of pollinators from ancient sites onto adjacent restored sites, although paired sites correlated in pollinator species richness in both years. There was little insect species overlap within each heathland between 2001 and 2004. 4A few widespread insect species dominated the communities and were the main pollinators. The most important pollinators were typically honeybees (Apis mellifera), species of bumblebee (Bombus spp.) and one hoverfly species (Episyrphus balteatus). The interaction networks were significantly less complex on restored heathlands, in terms of connectance values, although in 2004 the low values might reflect the negative relationship between connectance and species richness. Finally, there was a trend of restored networks being more susceptible to perturbation than ancient networks, although this needs to be interpreted with caution. 5Synthesis and applications. Ecological networks provide a powerful tool for assessing the outcome of restoration programmes. Our results indicate that heathland restoration does not have to occur immediately adjacent to ancient heathland for functional pollinator communities to be established. Moreover, in terms of restoring pollinator interactions, heathland managers need only be concerned with the most common insect species. Our focus on pollination demonstrates how a key ecological service can serve as a yardstick for judging restoration success. [source] A study in the uranyl ions uptake on acrylic acid and acrylamide copolymeric hydrogelsJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2008Ghanshyam S. Chauhan Abstract A series of copolymeric hydrogels comprising of acrylic acid and acrylamide and crosslinked with trimethylolpropane triacrylate (TMPTA) were prepared using ammonium persulfate (APS) as initiator. The hydrogels were functionalized further by partial hydrolysis and were characterized by SEM, FTIR, nitrogen analysis, and also by water uptake studies as a function of time, temperature, pH, NaCl, and concentration of sodium dodecyl sulfate (SDS). These hydrogels were used as sorbents for the uranyl ions uptake in the presence of 5% NaCl, which was studied as function of time, temperature, pH, and ion strength. The uranyl uptake was found to be affected both by the structural aspects of the hydrogels as well as by the external environmental factors. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] The Perceived Fairness of Layoff Practices,JOURNAL OF APPLIED SOCIAL PSYCHOLOGY, Issue 8 2003Monica A. Hemingway Policy capturing was used to identify layoff practices having the greatest impact on the perceived fairness of layoffs. Full-time employees (N = 23) rated the fairness of 100 hypothetical layoffs incorporating each of 12 layoff practices reflecting different approaches to organizational justice. Managerial consistency in implementing layoffs, an unbiased layoff policy, and the size of severance packages had the strongest influence on fairness judgments. These results suggest that practices reflecting structural aspects of justice play the greatest role in layoff fairness perceptions, whereas practices consistent with social aspects of justice may be relatively less important. [source] Combining a polarizable force-field and a coarse-grained polarizable solvent model: Application to long dynamics simulations of bovine pancreatic trypsin inhibitorJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 11 2008Michel Masella Abstract The dynamic coupling between a polarizable protein force field and a particle-based implicit solvent model is described. The polarizable force field, TCPEp, developed recently to simulate protein systems, is characterized by a reduced number of polarizable sites, with a substantial gain in efficiency for an equal chemical accuracy. The Polarizable Pseudo-Particle (PPP) solvent model represents the macroscopic solvent polarization by induced dipoles placed on mobile Lennard-Jones pseudo-particles. The solvent-induced dipoles are sensitive to the solute electric field, but not to each other, so that the computational cost of solvent,solvent interactions is basically negligible. The solute and solvent induced dipoles are determined self-consistently and the equations of motion are solved using an efficient iterative multiple time step procedure. The solvation cost with respect to vacuum simulations is shown to decrease with solute size: the estimated multiplicative factor is 2.5 for a protein containing about 1000 atoms, and as low as 1.15 for 8000 atoms. The model is tested for six 20 ns molecular dynamics trajectories of a traditional benchmark system: the hydrated Bovine Pancreatic Trypsin Inhibitor (BPTI). Even though the TCPEp parameters have not been refined to be used with the solvent PPP model, we observe a good conservation of the BPTI structure along the trajectories. Moreover, our approach is able to provide a description of the protein solvation thermodynamic at the same accuracy as the standard Poisson-Boltzman continuum methods. It provides in addition a good description of the microscopic structural aspects concerning the solute/solvent interaction. © 2008 Wiley Periodicals, Inc. J Comput Chem, 2008 [source] Thermodynamic and structural aspects of sulfonamide crystals and solutionsJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2009German L. Perlovich Abstract The crystal structures of three sulfonamides with the general structure 4-NH2 -C6H4 -SO2NH-C6H4/3 -R (R,=,4-Et; 4-OMe; 5-Cl-2-Me) have been determined by X-ray diffraction. On the basis of our previous data and the results obtained a comparative analysis of crystal properties was performed: molecular conformational states, packing architecture, and hydrogen bond networks using graph set notations. The thermodynamic aspects of the sulfonamide sublimation process have been studied by investigating the temperature dependence of vapor pressure using the transpiration method. A regression equation was derived describing the correlation between sublimation entropy terms and crystal density data calculated from X-ray diffraction results. Also correlations between sublimation Gibbs energies and melting points, on the one hand, and between sublimation enthalpies and fusion enthalpies at 298 K, on the other hand, were found. These dependencies give the opportunity to predict sublimation thermodynamic parameters by simple thermo-physical experiments (fusion characteristics). Solubility processes of the compounds in water, n -hexane, and n -octanol (as phases modeling various drug delivery pathways and different types of membranes) were investigated and corresponding thermodynamic functions were calculated as well. Thermodynamic characteristics of sulfonamide solvation were evaluated. For compounds with similar structures processes of transfer from one solvent to another one were studied by a diagram method combined with analysis of enthalpic and entropic terms. Distinguishing between enthalpy and entropy, as is possible through the present approach, leads to the insight that the contribution of these terms is different for different molecules (entropy- or enthalpy-determined). Thus, in contrast to interpretation of only the Gibbs energy of transfer, being extensively used for pharmaceuticals in the form of the partition coefficient (log,P), the analysis of thermodynamic functions of the transfer process provides additional mechanistic information. This may be important for further evaluation of the physiological distribution of drug molecules and may provide a better understanding of biopharmaceutical properties of drugs. © 2009 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:4738,4755, 2009 [source] Soil organic matter beyond molecular structure Part I: Macromolecular and supramolecular characteristicsJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 2 2006Gabriele E. Schaumann Abstract This contribution reviews and discusses structural aspects of soil organic matter (SOM) and humic substances (HS) with special respect to the macromolecular and the supramolecular view. It can be concluded that (1) dissolved humic acids behave as supramolecular associations of relatively small molecules with an enormous flexibility of reaction of environmental conditions, (2) multivalent cations may increase the apparent molecular weight by the formation of coordinative crosslinks in dissolved and undissolved natural organic matter (NOM), (3) sorption nonlinearity in solid humic acids and SOM may be due to polymer properties of NOM, (4) sorbates affect sorbent characteristics of SOM, and (5) hysteresis and conditioning effects in SOM can up to now best be explained with the polymer analogy. A distinct polydispersivity of SOM over a wide range of molecular masses is to be assumed. The supramolecular and the macromolecular models were derived from humic acids with different composition and on the basis of different sample states. Although the supramolecular model has not explicitely been shown for unfractionated DOM, the combination of all discussed studies suggests supramolecular as well as macromolecular characteristics of NOM. Neither macromolecules nor small molecules can be fully excluded in solid and dissolved SOM. Microregions with different properties provide different types of sorption sites. SOM is suggested to be regarded as amorphous material. This point of view is not restricted to high molecular masses and may supplement our understanding of SOM by the model of physical aging. [source] Engineering functional materials by halogen bondingJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 1 2007Pierangelo Metrangolo Abstract Engineering functional materials endowed with unprecedented properties require the exploitation of new intermolecular interactions, which can determine the characteristics of the bulk materials. The great potential of Halogen Bonding (XB), namely any noncovalent interaction involving halogens as electron acceptors, in the design of new and high-value functional materials is now emerging clearly. This Highlight will give a detailed overview on the energetic and geometric features of XB, showing how some of them are quite constant in most of the formed supramolecular complexes (e.g., the angle formed by the covalent and the noncovalent bonds around the halogen atom), while some others depend strictly on the nature of the interacting partners. Then, several specific examples of halogen-bonded supramolecular architectures, whose structural aspects as well as applications in fields as diverse as enantiomers' separation, crystal engineering, liquid crystals, natural, and synthetic receptors, will be fully described. © 2006 Wiley Periodicals, Inc. J Polym Sci Part A: PolymChem 45: 1,15, 2007 [source] Photoinitiated polymerization of methacrylic monomers in a polybutadiene matrix (PB): Kinetic, mechanistic, and structural aspectsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 14 2001J. L. Mateo Abstract The kinetics and mechanism of the photoinitiated polymerization of tetrafunctional and difunctional methacrylic monomers [1,6-hexanediol dimethacylate (HDDMA) and 2-ethylhexyl methacrylate (EHMA)] in a polybutadiene matrix (PB) have been studied. The maximum double-bond conversion, the maximum polymerization rate, the intrinsic reactivity, and the kinetic constants for propagation and termination have been calculated. Unlike the behavior followed by the SBS-HDDMA and PS-HDDMA systems, where a reaction-diffusion mechanism occurs from the start of the polymerization at low monomer concentrations (<30,40%), in the PB-HDDMA system the reaction diffusion controls the termination process only after approximately 10% conversion is reached, as for the bulk polymerization of polyfunctional methacrylic monomers. Before reaching 10% conversion the behavior observed can be better explained by a combination of segmental diffusion-controlled (autoaccelerated) and reaction-diffusion mechanisms. This is probably a consequence of the lower force of attraction between the monomer and the matrix and between the growing macroradical and the matrix than those corresponding to the other systems mentioned. For the PB-EHMA system, the termination mechanism is principally diffusion-controlled from the beginning of the polymerization for monomer concentrations below 30,40%, and for higher monomer concentrations, a standard termination mechanism takes place (kt , 106) at low double-bond conversions, which is diffusion-controlled for high conversions (>40%). For PB-HDDMA and PB-EHMA systems, crosslinked polymerized products are obtained as a result of the participation of the double bonds of the matrix in the polymerization process. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2444,2453, 2001 [source] Photoinitiated polymerization of methacrylic monomers in a polystyrene matrix: Kinetic, mechanistic, and structural aspectsJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 12 2001J. L. Mateo Abstract The kinetics and mechanism of the photoinitiated polymerization of tetrafunctional and difunctional methacrylic monomers [1,6-hexanediol dimethacrylate (HDDMA) and 2-ethylhexyl methacrylate (EHMA)] in a polystyrene (PS) matrix were studied. The aggregation state, vitreous or rubbery, of the monomer/matrix system and the intermolecular strength of attraction in the monomer/matrix and growing macroradical/matrix systems are the principal factors influencing the kinetics and mechanism. For the PS/HDDMA system, where a relatively high intermolecular force of attraction between monomer and matrix and between growing macroradical and matrix occurs, a reaction-diffusion mechanism takes place at low monomer concentrations (<30,40%) from the beginning of the polymerization. For the PS/EHMA system, which presents low intermolecular attraction between monomer and matrix and between growing macroradical and matrix, the reaction-diffusion termination is not clear, and a combination of reaction-diffusion and diffusion-controlled mechanisms explains better the polymerization for monomer concentrations below 30,40%. For both systems, for which a change from a vitreous state to a rubbery state occurs when the monomer concentration changes from 10 to 20%, the intrinsic reactivity and kp/kt1/2 ratio (where kp is the propagation kinetic constant and kt is the termination kinetic constant) increase as a result of a greater mobility of the monomer in the matrix (a greater kp value). The PS matrix participates in the polymerization process through the formation of benzylic radical, which is bonded to some extent by radical,radical coupling with the growing methacrylic radica, producing grafting on the PS matrix. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 2049,2057, 2001 [source] RHEOLOGICAL CHARACTERIZATION OF WET FOOD FOAMSJOURNAL OF TEXTURE STUDIES, Issue 2 2007B. EDGAR CHÁVEZ-MONTES ABSTRACT Incorporating air bubbles into foods is a technical challenge, and in all cases, the fabrication of a foam goes through a "wet foam" stage, where bubbles are diluted in the food matrix and require stabilization. Sometimes, the end product is itself a wet foam, and a popular example is ice cream. This article describes a study of structural aspects of wet foams, where the continuous phase is a fluid, by means of dynamic rheological tests. The effects of formulation and processing conditions on aerated food foams are studied, and an example is presented for ice cream mix. The incorporation of gas bubbles at volume fractions of 50% or less modifies moderately the bulk rheological properties, and their effect can be predicted by the foam limit case. The continuous phase dominates to a great part the bulk's rheological behavior, and in the case of food systems, it stems from the presence of polysaccharide thickeners. PRACTICAL APPLICATIONS This work presents an alternative approach to study the rheological properties of short life and difficult-to-sample products, such as wet food foams, in a rheo-reactor. Through the analysis of mechanical properties in oscillatory regime, the structure and stability of wet food foams can be characterized immediately after being fabricated in situ. This work presents new insights on the foaming step of ice cream mix (decoupled from the freezing step), and shows how the mechanical properties are affected by the incorporation ofbubbles, by process conditions and by the presence of thickeners and emulsifiers. This work can be a valuable guide to decide on optimal process and formulation to fabricate wet food foams (e.g., ice cream, aerated desserts) with specific mechanical properties and stability. [source] Controlled free-radical polymerization of vinyl chlorideJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 3 2005Dietrich Braun Owing to the importance of poly(vinyl chloride) (PVC) as the second-largest plastic in volume after the polyolefins and above styrene polymers, the control of the free-radical polymerization of vinyl chloride (VC) is of high industrial and academic interest. But still the term "controlled" polymerization is not yet clearly defined. Often it is used for quasi-living polymerizations with equilibrium reactions in the initiation and/or termination step or for the control of the molecular weight distribution (MWD), but it can also be applied to several structural aspects such as stereochemistry, branching, or special technical properties. In the present article, the control of chain growth and chain transfer is discussed. It has been well known for many years that the propagation step in the VC polymerization is terminated to a large degree by the rather frequent and temperature-dependent chain transfer of the growing macromolecules to the monomer. Therefore, the degree of polymerization is strongly governed by the polymerization temperature. However, this transfer step does not result in a controlled or a narrow MWD. By means of free-radical nitroxide-mediated polymerization of VC in suspension, PVC with a narrower MWD can be obtained also at higher polymerization temperatures. The resulting PVC with nitroxide end groups can act as a macro-initiator for various monomers, resulting in two-block copolymers, which are, e.g., interesting compatibilizers in blends with PVC. J. VINYL ADDIT. TECHNOL., 11:86,90, 2005. © 2005 Society of Plastics Engineers [source] Influence of Internal Donors on the Performance and Structure of MgCl2 Supported Titanium Catalysts for Propylene PolymerizationMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 1 2009Gurmeet Singh Abstract An insight on the influence of ethyl benzoate (EB) and diisobutyl phthalate (DIBP) as internal donors, differing in coordination nature on the structural aspects of MgCl2 matrix in high-performance MgCl2 -supported titanium catalysts was developed using FTIR spectroscopy and WAXD studies. The analysis of the >CO stretching IR band of internal donors showed their coordination to (104) and (110) lateral cuts of MgCl2 matrix. Transformation of magnesium ethoxide {Mg(OEt)2} to MgCl2 during catalyst preparation resulted in different MgCl2 phases, namely the , -form, , -form, and the disordered , -form, which were analyzed by WAXD studies. The results from WAXD showed the relative preference of , -form over , -form in case of DIBP-based catalysts, which might be due to interlayer bridging between adjacent layers due to the bidendate nature of DIBP. This can be one of the reasons for the high productivity of dialkyl-phthalate-based catalysts in comparison to ethyl-benzoate-based catalyst systems. [source] A comparative study of multimodal vs. bimodal polyethylene pipe resins for PE-100 applications,POLYMER ENGINEERING & SCIENCE, Issue 9 2005Paul J. DesLauriers In this paper several high density polyethylene pipe resins are compared to polyethylene resins made in the Phillips Loop-Slurry Process (single-reactor), using a catalyst of chromium on modified aluminophosphate (Cr/AlPO4). A brief description of the Cr/AlPO4 system is presented along with polymer chain architecture (i.e., topology) and other structural aspects of polymers made from these catalysts. The physical properties of these resins and their fabricated pipe processing/performance properties were compared to both PE80 and conventional bimodal type PE-100 resins. Results from this study show that high-density polyethylene resins made from Cr/AlPO4 catalysts possess primary structural attributes that are truly unique for chromium-catalyzed resins. These multimodal resins have very high molecular weights (MW; Mw > 400 kg/mol) and exceptionally broad MW distributions (MWD; Mw/Mn > 50). Topologically, these resins were found to have uniform short chain branching distributions across the MWD; as in polymers made from single site metallocene catalysts) and significantly reduced levels (10 times less) of long chain branching when compared to resins made using chromium catalysts on conventional supports. Furthermore, results from rheological, fabricated pipe processing, and performance studies suggest that these resins should be especially well suited for high performance pipe applications. Pipe samples made from these resins were found to meet PE-100 requirements including low temperature impact properties. POLYM. ENG. SCI., 45:1203,1213, 2005. © 2005 Society of Plastics Engineers [source] Gas-phase ion chemistry of Glu/Met systems,RAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 1 2002H. Wincel A combined chemical ionisation and tandem mass spectrometry (MS/MS) approach has been used for investigation of the gas-phase ion chemistry of systems containing the amino acids Glu and Met, and the dipeptides ,-Glu-Met and Met-Glu. The metastable fragmentation of the protonated dimer, (Glu)2H+, reveals an intracluster reaction leading to the elimination of the Glu residue. The main features of the ion-molecule reactions observed in the systems containing Glu and Glu,+,Met can be described in terms of sequential adduct formation. The results obtained for the thermal dehydration of Glu were used to rationalise the formation of the proton-bound structures (Glu,,,H2O)···H+··· (Glu,,,H2O) and (Glu,,,H2O)3·H+. The adduct ions, [(Glu,,,H2O),+,H,+,Glu]+ and [(Glu,,,H2O),+ H,+,Met]+, and further association products were also observed. The results lead to a reconsideration of the structural aspects proposed earlier for these species in the sense that they suggest that the systems correspond to a mixture of isomeric covalent and proton-bound structures. The thermal effects on the decomposition of the neutral (,-Glu-Met) and its protonated form, (,-Glu-Met)H+, at m/z 279 were investigated, and dramatic changes in the MI spectra of the m/z 279 ion with temperature were found. A mechanistic explanation for the observed evolution of higher mass ion peaks in the mass spectra is developed. Copyright © 2001 John Wiley & Sons, Ltd. [source] Human neural stem cell grafts in the spinal cord of SOD1 transgenic rats: Differentiation and structural integration into the segmental motor circuitryTHE JOURNAL OF COMPARATIVE NEUROLOGY, Issue 4 2009Leyan Xu Abstract Cell replacement strategies for degenerative and traumatic diseases of the nervous system depend on the functional integration of grafted cells into host neural circuitry, a condition necessary for the propagation of physiological signals and, perhaps, targeting of trophic support to injured neurons. We have recently shown that human neural stem cell (NSC) grafts ameliorate motor neuron disease in SOD1 transgenic rodents. Here we study structural aspects of integration of neuronally differentiated human NSCs in the motor circuitry of SOD1 G93A rats. Human NSCs were grafted into the lumbar protuberance of 8-week-old SOD1 G93A rats; the results were compared to those on control Sprague-Dawley rats. Using pre-embedding immuno-electron microscopy, we found human synaptophysin (+) terminals contacting the perikarya and proximal dendrites of host , motor neurons. Synaptophysin (+) terminals had well-formed synaptic vesicles and were associated with membrane specializations primarily in the form of symmetrical synapses. To analyze the anatomy of motor circuits engaging differentiated NSCs, we injected the retrograde transneuronal tracer Bartha-pseudorabies virus (PRV) or the retrograde marker cholera toxin B (CTB) into the gastrocnemius muscle/sciatic nerve of SOD1 rats before disease onset and also into control rats. With this tracing, NSC-derived neurons were labeled with PRV but not CTB, a pattern suggesting that PRV entered NSC-derived neurons via transneuronal transfer from host motor neurons but not via direct transport from the host musculature. Our results indicate an advanced degree of structural integration, via functional synapses, of differentiated human NSCs into the segmental motor circuitry of SOD1-G93A rats. J. Comp. Neurol. 514:297,309, 2009. © 2009 Wiley-Liss, Inc. [source] New Powder Diffraction File (PDF-4) in relational database format: advantages and data-mining capabilitiesACTA CRYSTALLOGRAPHICA SECTION B, Issue 3-1 2002Soorya N. Kabekkodu The International Centre for Diffraction Data (ICDD) is responding to the changing needs in powder diffraction and materials analysis by developing the Powder Diffraction File (PDF) in a very flexible relational database (RDB) format. The PDF now contains 136,895 powder diffraction patterns. In this paper, an attempt is made to give an overview of the PDF-4, search/match methods and the advantages of having the PDF-4 in RDB format. Some case studies have been carried out to search for crystallization trends, properties, frequencies of space groups and prototype structures. These studies give a good understanding of the basic structural aspects of classes of compounds present in the database. The present paper also reports data-mining techniques and demonstrates the power of a relational database over the traditional (flat-file) database structures. [source] Phosphate tungsten bronze series: crystallographic and structural properties of low-dimensional conductorsACTA CRYSTALLOGRAPHICA SECTION B, Issue 5 2001P. Roussel Phosphate tungsten bronzes have been shown to be conductors of low dimensionality. A review of the crystallographic and structural properties of this huge series of compounds is given here, corresponding to the present knowledge of the different X-ray studies and electron microscopy investigations. Three main families are described, monophosphate tungsten bronzes, Ax(PO2)4(WO3)2m, either with pentagonal tunnels (MPTBp) or with hexagonal tunnels (MPTBh), and diphosphate tungsten bronzes, Ax(P2O4)2(WO3)2m, mainly with hexagonal tunnels (DPTBh). The general aspect of these crystal structures may be described as a building of polyhedra sharing oxygen corners made of regular stacking of WO3 -type slabs with a thickness function of m, joined by slices of tetrahedral PO4 phosphate or P2O7 diphosphate groups. The relations of the different slabs with respect to the basic perovskite structure are mentioned. The structural description is focused on the tilt phenomenon of the WO6 octahedra inside a slab of WO3 -type. In this respect, a comparison with the different phases of the WO3 crystal structures is established. The various modes of tilting and the different possible connections between two adjacent WO3 -type slabs involve a great variety of structures with different symmetries, as well as the existence of numerous twins in MPTBp's. Several phase transitions, with the appearance of diffuse scattering and modulation phenomena, were analysed by X-ray scattering measurements and through the temperature dependence of various physical properties for the MPTBp's. The role of the W displacements within the WO3 -type slabs, in two modulated structures (m = 4 and m = 10), already solved, is discussed. Finally, the complexity of the structural aspects of DPTBh's is explained on the basis of the average structures which are the only ones solved. [source] Atomic resolution structure of pseudoazurin from the methylotrophic denitrifying bacterium Hyphomicrobium denitrificans: structural insights into its spectroscopic propertiesACTA CRYSTALLOGRAPHICA SECTION D, Issue 1 2009Daisuke Hira The crystal structure of native pseudoazurin (HdPAz) from the methylotrophic denitrifying bacterium Hyphomicrobium denitrificans has been determined at a resolution of 1.18,Å. After refinement with SHELX employing anisotropic displacement parameters and riding H atoms, Rwork and Rfree were 0.135 and 0.169, respectively. Visualization of the anisotropic displacement parameters as thermal ellipsoids provided insight into the atomic motion within the perturbed type 1 Cu site. The asymmetric unit includes three HdPAz molecules which are tightly packed by head-to-head cupredoxin dimer formation. The shape of the Cu-atom ellipsoid implies significant vibrational motion diagonal to the equatorial xy plane defined by the three ligands (two His and one Cys). The geometric parameters of the type 1 Cu site in the HdPAz structure differ unambiguously from those of other pseudoazurins. It is demonstrated that their structural aspects are consistent with the unique visible absorption spectrum. [source] The first structure of a cold-active catalase from Vibrio salmonicida at 1.96,Å reveals structural aspects of cold adaptationACTA CRYSTALLOGRAPHICA SECTION D, Issue 2 2007Ellen Kristin Riise The cold-adapted catalase from the fish-pathogenic bacterium Vibrio salmonicida (VSC) has recently been characterized and shown to be two times more catalytically efficient compared with catalase from the mesophilic human pathogen Proteus mirabilis [PMC; Lorentzen et al. (2006), Extremophiles, 10, 427,440]. VSC is also less temperature-stable, with a half-life of 5,min at 333,K compared with 50,min for PMC. This was the background for solving the crystal structure of the cold-adapted VSC to 1.96,Å and performing an extensive structural comparison of VSC and PMC. The comparison revealed that the entrance (the major channel) leading to the catalytically essential haem group, is locally more flexible and slightly wider in VSC. This might explain the enhanced catalytic efficiency of the nearly diffusion-controlled degradation of hydrogen peroxide into water and molecular oxygen in VSC. The reduced thermal stability of the cold-adapted VSC may be explained by a reduced number of ion-pair networks. The four C-terminal ,-helices are displaced in the structures, probably owing to missing ionic interactions in VSC compared with PMC, and this is postulated as an initiation site for unfolding the cold-adapted enzyme. VSC is the first crystal structure reported of a cold-adapted monofunctional haem-containing catalase. [source] Porous Metal Oxides as Gas SensorsCHEMISTRY - A EUROPEAN JOURNAL, Issue 30 2007Michael Tiemann Dr. Abstract Semiconducting metal oxides are frequently used as gas-sensing materials. Apart from large surface-to-volume ratios, well-defined and uniform pore structures are particularly desired for improved sensing performance. This article addresses the role of some key structural aspects in porous gas sensors, such as grain size and agglomeration, pore size or crack-free film morphology. New synthesis concepts, for example, the utilisation of rigid matrices for structure replication, allow to control these parameters independently, providing the opportunity to create self-diagnostic sensors with enhanced sensitivity and reproducible selectivity. [source] | |||||||||||||||||||||||||||||||||||||