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Great Effect (great + effect)
Selected AbstractsFactors governing the formation and persistence of layers in a subalpine snowpackHYDROLOGICAL PROCESSES, Issue 7 2004David Gustafsson Abstract The layered structure of a snowpack has a great effect on several important physical processes, such as water movement, reflection of solar radiation or avalanche release. Our aim was to investigate what factors are most important with respect to the formation and persistence of distinct layers in a subalpine environment. We used a physically based numerical one-dimensional model to simulate the development of a snowpack on a subalpine meadow in central Switzerland during one winter season (1998,99). A thorough model validation was based on extensive measurement data including meteorological and snow physical parameters. The model simulated the snow water equivalent and the depth of the snowpack as well as the energy balance accurately. The observed strong layering of the snowpack, however, was not reproduced satisfactorily. In a sensitivity analysis, we tested different model options and parameter settings significant for the formation of snow layers. The neglection of effects of snow microstructure on the compaction rate, and the current description of the water redistribution inside the snowpack, which disregard capillary barrier effects, preferential flow and lateral water flow, were the major limitations for a more realistic simulation of the snowpack layering. Copyright © 2004 John Wiley & Sons, Ltd. [source] Hydrothermal Synthesis and Characterization of KxNa(1,x)NbO3 PowdersINTERNATIONAL JOURNAL OF APPLIED CERAMIC TECHNOLOGY, Issue 6 2007Jun-Hai Lv NaNbO3, KNbO3, and KxNa(1,x)NbO3 powders were successfully prepared by the hydrothermal method. The phase of the products was identified to be orthorhombic structure by X-ray diffraction (XRD) technique, and the XRD results revealed that the x value of the KxNa(1,x)NbO3 gradually increased with the increase in the ratio of K+ to Na+ in alkaline solution. The morphology and the microstructure were investigated by scanning electron microscopy, energy-dispersive spectroscopy, and transmission electron microscopy, and the results indicated that the ratio of K+ to Na+ in the solution had a great effect on the morphology and the size of products. Na0.5K0.5NbO3 with morphotropic phase boundary composition could be synthesized when the molar ratio of K+ to Na+ was between 4:1 and 6:1 in the solution. A possible formation mechanism of the KxNa(1,x)NbO3 crystal was also proposed based on the experimental results. [source] Influence of the monomer feeding sequence on the structure and properties of thermotropic liquid-crystalline poly(ester imide)sJOURNAL OF APPLIED POLYMER SCIENCE, Issue 5 2008Zhenguo Chi Abstract A series of poly(ester imide)s mainly derived from N,N,-hexane-1,6-diylbistrimellitimides, 4,4,-dihydroxybenzophenone, and p -hydroxybenzoic acid were synthesized by a direct polycondensation method in benzenesulfonyl chloride, N,N,-dimethylformamide, and pyridine with different monomer feeding sequences. The molecular structures and properties of the resultant poly(ester imide)s were characterized with NMR, IR spectrometry, polarized light microscopy, wide-angle X-ray diffraction, differential scanning calorimetry, and thermogravimetric analysis. The results showed that the monomer feeding sequences had a great effect on the sequential structure of the molecular chains of the copolymers and consequently on their liquid-crystalline (LC) properties, fiber-forming capability, and other properties. Thus, it is probable that one could obtain an LC poly(ester imide) with given properties by controlling the monomer feeding sequence during the polycondensation process. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Thermal oxidative degradation kinetics of PP and PP/mg (OH)2 flame-retardant compositesJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2007Xiaolang Chen Abstract The thermal stability and thermal oxidative degradation kinetics of polypropylene (PP) and flame-retardant PP composites filled with untreated and treated magnesium hydroxide (MH) in air were studied by thermogravimetric analysis (TGA). The effect of the heating rate in dynamic measurements (5°C,30°C/min) on kinetic parameters such as activation energy was also investigated. The Kissinger and Flynn,Wall,Ozawa methods were used to determine the apparent activation energy for the degradation of neat PP and flame-retardant PP composites. The results of TGA showed that the addition of untreated or treated MH improved the thermal oxidative stability of PP in air. The kinetic results showed that the apparent activation energy for degradation of flame-retardant PP composites was much higher than that of neat PP, suggesting that the flame retardant used in this work had a great effect on the mechanisms of pyrolysis and combustion of PP. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 103: 1978,1984, 2007 [source] Morphological variation of perch Perca fluviatilis in humic lakes: the effect of predator density, competition and prey abundanceJOURNAL OF FISH BIOLOGY, Issue 4 2010J. Kekäläinen Between and within-lake variations in morphology of perch Perca fluviatilis were studied in four humic lakes in eastern Finland. Perca fluviatilis were more streamlined and smaller headed in a lake with the highest abundance of cyprinids, but lowest abundance of predators (Lake Tuopanjärvi), indicating adaptation to planktivorous feeding and low predator density. Highest bodied fish were found from a lake with the lowest cyprinid but highest predator abundance (Lake Koppelojärvi), which conversely indicates adaptation to more effective predator avoidance. Furthermore, the length of the paired fins was longest in Lake Kinnasjärvi and Lake Tuopanjärvi, where the abundance of benthic macroinvertebrates was lowest, suggesting selection for more effective benthivory. Clear morphological differences of P. fluviatilis between habitats were found only in Lake Kinnasjärvi, whereas in Lake Koppelojärvi and Lake Tuopanjärvi only the length of the paired fins differed and in Lake Harkkojärvi no differences were found. Taken together, these results suggest that inter and intrapopulation morphological differences are probably highly dependent on different biotic factors (i.e. predation risk, resource availability and competition). Spatial and temporal variations in these factors may have a great effect on body morphology of P. fluviatilis. [source] THE EFFECT OF REFRIGERATED STORAGE ON SENSORY PROFILE AND PHYSICAL-CHEMICAL CHARACTERISTICS OF MINIMALLY PASTEURIZED ORANGE JUICEJOURNAL OF FOOD PROCESSING AND PRESERVATION, Issue 2009TATIANA BEATRIS TRIBESS ABSTRACT Minimal pasteurization of orange juice (OJ) consists of using minimum holding time and temperature to ensure partial inactivation of pectin methylesterase (PME). This process produces juice with preserved sensory attributes and has a better acceptance by consumers when compared with commercially pasteurized OJ. Sensory profile and physical-chemical characteristics of minimally processed OJ was determined, during refrigerated storage, for two OJ blends with different pH values and the same level of PME thermal inactivation. A selected and trained sensorial panel (n = 16) performed sensory analysis, based on a quantitative descriptive analysis, twice a week for 30 days, evaluating the attributes of appearance (suspended particles and color intensity), odor (natural orange and fermented orange) and flavor (orange characteristic, fermented orange, acid and bitter taste). Storage presented great effect on OJ sensory profile; however, it was not noticeable on physical-chemical characteristics. PRACTICAL APPLICATIONS Minimal pasteurization of orange juice (OJ) consists of using minimum holding time and temperature to ensure partial inactivation of pectin methylesterase. This process produces juice with longer shelf life than fresh squeezed orange juice, preserved sensory attributes and better acceptance by consumers when compared with commercially pasteurized OJ. This study can contribute for quality evaluation of minimally pasteurized OJ under refrigeration. [source] Implicit Family Process Rules in Eating-Disordered and Non-Eating-Disordered FamiliesJOURNAL OF MARITAL AND FAMILY THERAPY, Issue 2 2009Kyle S. Gillett Family environment has been shown to be one of the factors related to the presence of eating disorders among young-adult females. Clinical experience and theories about eating disorders postulate that implicit family rules are an intricate part of family process that may have a great effect on the creation and maintenance of such problems. This study compared implicit family process rules (specifically rules pertaining to kindness; expressiveness and connection; constraining thoughts, feelings, and self; inappropriate caretaking; and monitoring) in families with a young-adult female diagnosed with an eating disorder,either anorexia nervosa, bulimia nervosa, or eating disorder not otherwise specified,and families with a young-adult female without an eating disorder diagnosis. One hundred two families (51 eating disordered and 51 comparison) participated in the study. Mothers, fathers, young-adult female children, and siblings completed the Family Implicit Rules Profile (Harper, Stoll, & Larson, 2007). Results indicated that eating-disordered families are governed by a greater proportion of constraining family rules than are non-eating-disordered families. Additionally, eating-disordered youth reported a lower proportion of facilitative family rules and a higher proportion of constraining family rules than did parents and siblings. Theoretical, research, and clinical implications are discussed. [source] Effect of eluent on the ionization efficiency of flavonoids by ion spray, atmospheric pressure chemical ionization, and atmospheric pressure photoionization mass spectrometryJOURNAL OF MASS SPECTROMETRY (INCORP BIOLOGICAL MASS SPECTROMETRY), Issue 12 2001Jussi-Pekka Rauha Abstract The effect of nine different eluent compositions on the ionization efficiency of five flavonoids was studied using ion spray (IS), atmospheric pressure chemical ionization (APCI), and the novel atmospheric pressure photoionization (APPI), in positive and negative ion modes. The eluent composition had a great effect on the ionization efficiency, and the optimal ionization conditions were achieved in positive ion IS and APCI using 0.4% formic acid (pH 2.3) as a buffer, and in negative ion IS and APCI using ammonium acetate buffer adjusted to pH 4.0. For APPI work, the eluent of choice appeared to be a mixture of organic solvent and 5 mM aqueous ammonium acetate. The limits of detection (LODs) were determined in scan mode for the analytes by liquid chromatography/mass spectrometry using IS, APCI and APPI interfaces. The results show that negative ion IS with an eluent system consisting of acidic ammonium acetate buffer provides the best conditions for detection of flavonoids in mass spectrometry mode, their LODs being between 0.8 and 13 µM for an injection volume of 20 µl. Copyright © 2001 John Wiley & Sons, Ltd. [source] Photophysical and self-assembly behavior of poly(amidoamine) dendrons with chromophore as scaffold: The effect of dendritic architectureJOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 13 2008Bing-Bing Wang Abstract Two series of amphiphiles composed of hydrophilic poly(amidoamine) dendrons (from the first to the third generation) as the shell and hydrophobic aromatic chromophores (3,6-di(maleimidyl)-9-phenyl carbazole and 9-(4,-maleimidyl phenyl)-3-maleimidyl carbazole) as the central scaffold were synthesized. The effect of dendritic architecture on the photophysical properties and the self-assembly behavior of these amphiphiles were studied by UV,vis absorption spectroscopy, fluorescence spectroscopy, and transmission electron microscopy (TEM) measurements. Both the generation of dendritic shell and the location of dendrons at the chromophoric scaffold had great effect on the photophysical properties of these amphiphiles. In addition, different spherical aggregates were formed from these amphiphiles in the aqueous solution at different concentrations. Because of the combined effects of steric hindrance and architecture of dendritic shells, the amphiphiles from G2 dendron with central chromophore self-organized into ordered aggregates more readily than that from G1 and G3. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4584,4593, 2008 [source] Optimization of the separation conditions of tetracyclines on a preselected reversed-phase column with embedded urea groupJOURNAL OF SEPARATION SCIENCE, JSS, Issue 7 2006Leila Kallel Abstract The use of a C12 stationary phase with embedded polar group has been investigated for the separation of seven tetracyclines. The influence of pH, organic modifier, buffer, and temperature on the peak shape and analyte separation was discussed. It appears that all the chromatographic conditions had a great effect on both the resolution and peak shape whereas the elution order was not affected. The baseline separation with symmetrical peaks of the seven tetracyclines can be obtained with a mobile phase containing either 5 mM phosphate buffer pH 2.5/ACN (84 : 16 v/v) or 5 mM perchlorate buffer pH 2.5/ACN (75 : 25 v/v) at a temperature not exceeding 20°C. This study reveals that the retention mechanism is ion-pairing. [source] Neutron reflectivity of polymer-plasticiser diffusionMACROMOLECULAR SYMPOSIA, Issue 1 2002J.S. Higgins Neutron reflectivity (NR) has been widely exploited to look at polymer thin films and in many ways is an ideal technique for studying polymer interfaces and surfaces, providing high-resolution concentration - depth profiles across the film thickness. Most NR studies to date have concentrated on thin films of amorphous polymers which possess Tg values well above room temperature. These polymers are ideally suited to NR measurements, firstly because they form homogeneously flat films and, secondly, heat-quench cycles can be used to study time-dependent processes. This has been used to great effect in NR studies of the initial stages of polymer - polymer interdiffusion or the kinetics of surface segregated layers for instance. One of the biggest drawbacks to this approach is that in polymer systems where one or more of the components has a Tg close to or less than room temperature, the polymers can still move during the measurement time of an NR profile, which typically takes 1-2 h for a full profile. Therefore, in order to study such systems, we have developed an approach to NR measurements that allows us to investigate diffusion processes in situ. Our new approach allows us to take NR profiles in only 20 s. This paper describes the method of real-time NR measurements in detail and illustrates the capabilities of the technique with highlights from some of our recent work on the early stages of polymer-plasticiser interdiffusion. [source] Penn State joins the Big Ten and learns to benchmarkNEW DIRECTIONS FOR HIGHER EDUCATION, Issue 118 2002Robert Secor Joining the Big Ten wasn't just about football. Since it became part of the alliance, Penn State has learned to benchmark to great effect, particularly in regard to faculty and academic issues. [source] Influence of annealing temperature on the structural and optical properties of sol,gel prepared ZnO thin filmsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 10 2006Mingsong Wang Abstract Zinc oxide thin films have been prepared via a sol,gel process. The influence of annealing temperature on the structural and optical properties of the ZnO thin films has been investigated. The prepared ZnO thin films had a polycrystalline hexagonal wurtzite structure with no preferred orientation. The annealing temperature had a great effect on the optical properties of the ZnO thin films: the optical band gap became narrow due to the increase in crystallite size and the reduction in amorphous phase amount with increasing annealing temperature. Absorption or desorption of oxygen in the annealing process caused the observed yellow or green emission. (© 2006 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Low-temperature photopolymerization and post-cure characteristics of acrylatesPOLYMER INTERNATIONAL, Issue 6 2007Xia Gao Abstract Near-infrared spectroscopy was used to investigate the post-cure characteristics of acrylates polymerized from , 75 °C up to room temperature. The results obtained showed that the double bond conversion increased with increasing initiator concentration. Post-cure was much more striking for samples cured at lower temperatures. The chemical structure of monomer and photoinitiator had a great effect on the post-cure process. The greater the functionality, the lower the final double bond conversion and the more distinct the post-cure effect. Copyright © 2006 Society of Chemical Industry Society of Chemical Industry [source] | |||||||||||||