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Structural Breakdown (structural + breakdown)
Selected AbstractsElementary processes of soil,water interaction and thresholds in soil surface dynamics: a reviewEARTH SURFACE PROCESSES AND LANDFORMS, Issue 9 2004Richard S. B. Greene Abstract Elementary processes of soil,water interaction and the thresholds to these processes are important to understand as they control a range of phenomena that occur at the soil surface. In particular processes involved with wetting by rainfall that lead to particle breakdown are critical. This breakdown causes soil detachment and crust formation, which are both key elements in erosion. This paper reviews the range of approaches that have been taken in describing the processes associated with the wetting of a soil surface by rainfall. It assembles the studies that emphasize soil physics, soil chemistry, and erosion mechanics in a framework to enable a balanced consideration of important processes and management strategies to control erosion for a particular situation. In particular it discusses the factors associated with the two basic processes of soil structural breakdown, i.e. slaking and dispersion, and how these processes are critical in particle detachment, transport and surface crust formation. Besides the balance between the exchangeable cation composition and electrolyte concentration (measured as the sodium adsorption ratio (SAR) and total cation concentration (TCC) respectively) of the soil, the importance of energy input and soil organic matter content in controlling clay dispersion is emphasized. Based on the balance between these factors, the soil can be in one of three different regions, i.e. a dispersed region, a ,occulated region and one where the resilience of the soil is variable. The implications of each of these regions to soil erosion management are brie,y outlined, as are the critical roles that soil cover levels and organic matter have in controlling erosion. Finally, the relationship between various laboratory measures of aggregate stability, and corresponding ,eld erosion characteristics, is discussed. Copyright © 2004 John Wiley & Sons, Ltd. [source] Release mechanisms from gentamicin loaded poly(lactic- co -glycolic acid) (PLGA) microparticlesJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 3 2002Wolfgang Friess Abstract To provide local gentamicin delivery for 1 week based on a biodegradable system, poly(lactic- co -glycolic acid) (PLGA) microparticles were developed utilizing a 50/50 blend of Resomer® RG 502H, an uncapped variety of 13.5 kD, and Resomer® RG 503, an endcapped polymer of 36.2 kD. The liberation mechanism was investigated by analysis of morphological changes and thermal analysis focusing on the polymer glass transition temperature (Tg) and the mechanical properties. The release of gentamicin was related to a structural breakdown of the particles reaching a critical molecular weight. A Tg of <,37°C in the hydrated state was not indicative of collapse and agglomeration of the particles because the mechanical strength of the polymer structures in the rubbery state may still render sufficient support. As the gap between incubation temperature and Tg widened, the mechanical stability of the PLGA microparticles decreased and became decisive. Particles prepared with RG 502H show a lower ability to bear mechanical stress than RG 503 and 50/50 RG 502H/RG 503 microparticles. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91: 845,855, 2002 [source] INSTRUMENTAL TEXTURE OF SET AND STIRRED FERMENTED MILK.JOURNAL OF TEXTURE STUDIES, Issue 3 2001EFFECT OF A ROPY STRAIN OF LACTOBACILLUS DELBRUECKII SUBSP. Texture profile analysis (TPA) of stirred and set cultured milk were evaluated, using an exopolysaccharide producing strain of Lactobacillus delbrueckii subsp. bulgaricus (NCFB 2772) and a protein enriched substrate (retentate). In both cases, samples were compared respectively with a nonropy strain (NCFB 1489) and reconstituted skim milk substrate. The retentate fermented products were firmer in comparison with skim milk products, both at 10% of total solids. A loss of structure occurred when the retentate products were stirred causing a nine-fold decrease in hardness, whereas in cultured milk products the loss was of around three-fold. The main differences were found in adhesiveness and fracture characteristics. Set retentate ropy product was five times more adhesive than the nonropy one, whereas in stirred retentate and set skim milk products the difference was two-fold. No differences in adhesiveness were detected when skim milk products were stirred using either strain. The fracture force on ropy retentate samples increased after fracture while the nonropy ones showed a decrease, implying more structural breakdown in the latter. On set products, cohesiveness increased slightly due to the ropy strain. Changes in texture observed between ropy and nonropy strains can be attributed to exopolysaccharide attachment to the casein matrix being increased when the protein content is higher. [source] Testing the Time-Variancy of Explanatory Factors of Strategic Change,BRITISH JOURNAL OF MANAGEMENT, Issue 2 2006José David Vicente-Lorente The article proposes an empirical framework able to: (1) assess the relative validity of both adaptive and inertial views of strategic change and (2) verify the potential time- or context-dependency by testing the structural stability of the empirical model, in Spanish banks, 1983,1997. Results offer inconclusive findings regarding (1) but strong evidence to answer (2). The assumption of structural stability is rejected and the effect of many explanatory factors considered in the empirical model varies over time as some factors show different effects and/or significance levels depending on the period considered. These findings suggest that explanatory models of strategic change should be viewed as ,time-' or ,context-dependent'. The article provides a conceptual model in which alternative explanations operate in a sequential way. The results highlight, first, that inconclusive past findings about adaptive versus inertial views should be reviewed under this new evidence, and future empirical research must assure that its methods and interpretations are robust to potential structural breakdowns; and second, the limitations raised by the static approach offered by the available theories/models when approaching the dynamic and complex nature of strategic change. Theoretical developments and implications for managerial practice are suggested. [source] | ||||||||||