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Chain Number (chain + number)
Selected AbstractsIntegration of lakes and streams in a landscape perspective: the importance of material processing on spatial patterns and temporal coherenceFRESHWATER BIOLOGY, Issue 3 2000George W. Kling 1. We studied the spatial and temporal patterns of change in a suite of twenty-one chemical and biological variables in a lake district in arctic Alaska, U.S.A. The study included fourteen stream sites and ten lake sites, nine of which were in a direct series of surface drainage. All twenty-four sites were sampled between one and five times a year from 1991 to 1997. 2. Stream sites tended to have higher values of major anions and cations than the lake sites, while the lake sites had higher values of particulate carbon, nitrogen, phosphorous and chlorophyll a. There were consistent and statistically significant differences in concentrations of variables measured at the inlet versus the outlet of lakes, and in variables measured at upstream versus downstream sites in the stream reaches which connect the lakes. In-lake processing tended to consume alkalinity, conductivity, H+, DIC, Ca2+, Mg2+, CO2, CH4, and NO3,, and produce K+ and dissolved organic carbon (DOC). In-stream processing resulted in the opposite trends (e.g. consumption of K+ and DOC), and the magnitudes of change were often similar to those measured in the lakes but with the opposite sign. 3. Observed spatial patterns in the study lakes included mean concentrations of variables which increased, decreased or were constant along the lake chain from high to low altitude in the catchment (stream sites showed no spatial patterns with any variables). The strongest spatial patterns were of increasing conductivity, Ca2+, Mg2+, alkalinity, dissolved inorganic carbon and pH with lake chain number (high to low altitude in the basin). These patterns were partly determined by the effect of increasing catchment area feeding into lakes further downslope, and partly by the systematic processing of materials in lakes and in the stream segments between lakes. 4. Synchrony (the temporal coherence or correlation of response) of variables across all lakes ranged from 0.18 for particulate phosphorus to 0.90 for Mg2+ the average synchrony for all twenty-one variables was 0.50. The synchronous behaviour of lake pairs was primarily related to the spatial location or proximity of the lakes for all variables taken together and for many individual variables, and secondarily, to the catchment to lake area ratio and the water residence time. 5. These results illustrate that, over small geographic areas, and somewhat independent of lake or stream morphometry, the consistent and directional (downslope) processing of materials helps produce spatial patterns which are coherent over time for many limnological variables. We combine concepts from stream, lake and landscape ecology, and develop a conceptual view of landscape mass balance. This view highlights that the integration of material processing in both lakes and rivers is critical for understanding the structure and function of surface waters, especially from a landscape perspective. [source] Multisensitive polymers based on 2-vinylpyridine and N -isopropylacrylamide ,JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 21 2001Sebastian Wohlrab Abstract Poly(2-vinylpyridine) (P2VP) containing functionalized end groups was synthesized using nitroxyl-mediated radical polymerization with a hydroxy-functionalized stable free radical. It was shown that P2VP could be synthesized with variable molar masses and low polydispersities. The transformation of the hydroxy groups to an acrylic ester led to the formation of macromonomers. A free-radical copolymerization of these macromonomers with N -isopropylacrylamide gave a graft copolymer with a poly(N -ispopropylacrylamide) backbone and P2VP side chains. Polymers containing different amounts of the monomers were synthesized. It was possible to vary both the amount of P2VP side chains at a constant chain length of the macromonomer and the chain length at a nearly constant chain number. The behavior of the multifunctional macromolecules at different temperatures and pH values was investigated using dynamic light scattering and DSC. The macromolecules were found to retain the specific properties of the homopolymers. The hydrodynamic radii of the synthesized graft copolymers were both dependent on the temperature and pH value. © 2001 John Wiley & Sons, Inc. J Polym Sci Part A: Polym Chem 39: 3797,3804, 2001 [source] Evaluation of model compounds,polypropylene film interactions by Fourier transformed infrared spectroscopy (FTIR) methodPACKAGING TECHNOLOGY AND SCIENCE, Issue 3 2008Laurent Safa Abstract The interactions of methyl esters, methyl ketones and aldehyde compounds with polypropylene (PP) film were investigated. PP film, placed on a glass vial, was immersed in aqueous solution containing a model flavour compound. After a determined time at 45°C, the PP film was analysed by Fourier transform infrared spectroscopy (FTIR), allowing us to follow the speed of sorption and to quantify its relative rate. ,,For PP films, we observed that the sorption strongly depended on the structure of sorbed molecules. For each functional group of flavour compounds, the sorption increased as the carbon chain number increased. A linear chain of 12,14 carbons favours the sorption more than a linear chain of eight carbons. ,,Concerning functions, the rate of sorption usually decreases from esters to ketones and to aldehydes. ,,High sorption was observed for flavour compounds with a low difference of solubility parameter (SP) value between the film and flavour [(,polymer , ,flavour)2 value]. Furthermore, by using the proposed thermodynamic affinity concept, represented as the contribution of three interactive molecular forces [dispersion (dd), polar (dp) and hydrogen bonding (dh)] between two SP values of film and flavour, packaging materials with high flavour preservation against sorption can be designed. ,,We have a good correlation between the kinetic sorption by FTIR and the SP concept. Copyright © 2007 John Wiley & Sons, Ltd. [source] Nucleating agent for poly(L -lactic acid),An optimization of chemical structure of hydrazide compound for advanced nucleation abilityJOURNAL OF APPLIED POLYMER SCIENCE, Issue 1 2007N. Kawamoto Abstract A series of compounds having hydrazide groups was prepared and evaluated as nucleating agent for poly(L -lactic acid) by differential scanning calorimetry. Hydrazide compounds derived from benzoic acid, 2-hydroxybenzoic acid, 3- tert -butylbenzoic acid, and 2-aminobenzoic acid, where two of hydrazide compounds connected by four methylene chain were evaluated in series. Benzoylhydrazide type was found to be more effective on the enhancement of crystallization of poly(L -lactic acid). Effects of connecting length of methylene chain numbers between two of benzoylhydrazide on the nucleation ability were also evaluated. Benzoylhydrazide-type compound having 10 methylenes, that is, decamethylenedicarboxylic dibenzoylhydrazide demonstrated excellent nucleation ability, and the resulted crystallization temperature and enthalpy of PLA with the compound of 1 wt % loading were 131°C and 46 J g,1. The achieved crystallization temperature and enthalpy were over 10°C and over 10 J g,1 higher than PLA with conventional nucleating agents, such as talc and ethylenebis (12-hydroxystearylamide). Thus, the improvement in processability, productivity, and heat resistance of PLA is suggested to be achieved by using decamethylenedicarboxylic dibenzoylhydrazide as a nucleating agent. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 198,203, 2007 [source] | ||||||||||