			Home About us Contact

Size Dependency (size + dependency)

Distribution by Scientific Domains

Chemistry	50%

Selected Abstracts

Environmental and developmental controls on specific leaf area are little modified by leaf allometry

FUNCTIONAL ECOLOGY, Issue 4 2008
R. Milla
Summary 1Recent work shows that large leaves tend to require higher biomass investments per unit leaf area than small leaves. As a consequence, specific leaf area (SLA), which is a focus trait for a bulk of physiological and ecological research programs, is dependent on leaf size variation. Here, we address whether size dependency alters the outcome of research dealing with SLA responses to environmental or developmental change. 2We compiled lamina mass (M) and surface area (A) data for 2158 leaves of 26 species, coming from studies investigating the reaction of SLA to variation in rainfall, growth,season length, light intensity, atmospheric CO2, fire frequency, type of branch and leaf and plant age. We fitted the function M = a Ab to the data of each experimental situation separately, and implemented a method to split SLA response as measured in the original study (SLADm) into response due to leaf size dependency (SLADa), and response due to treatment effects, after controlling for leaf size dependency (SLADt). 3The sign of the reaction did not differ between SLADm and SLADt. However, the magnitude of that response changed for most contrasts, though in variable ways. 4Conclusions of past experiments hold, for the most part, after re-analysis including size dependency. However, given the large heterogeneity found here, we advise that future work investigating SLA be prepared to account for leaf size dependency when the factors under focus are suspected to alter leaf size. [source]

Impact of Grain Size on the Cerchar Abrasiveness Test

GEOMECHANICS AND TUNNELLING, Issue 1 2008
Klaus Lassnig Mag.
The Cerchar abrasiveness test is a common testing procedure for the prediction of tool wear but consistent and detailed recommendations of the testing procedure are inexistent until now. One point of disagreement is the required number of scratch tests per sample to obtain reliable results depending on the grain size of the samples. The focus of this work was to verify the influence of grain size on the number of required single examinations per sample. Grain size analyses were performed to get sum-curves of each tested rock sample. From the grain size data the median and the interquartile range of the grain sizes were calculated. CAI values after 5 and after 10 scratch tests were compared with the median and the interquartile-range of the grain size. No grain size dependency of the CAI deviation between 5 and 10 tests in the analysed range was observed. Einfluss der Korngröße auf den Cerchar Abrasivitätstest Der Cerchar-Abrasivitätstest ist ein häufig verwendeter Indextest zur Ermittlung der Abrasivität von Gesteinen gegenüber Bohrwerkzeugen. Bis jetzt existieren keine einheitlichen und detaillierten Empfehlungen für die Durchführung des Tests. Insbesondere gilt das für die Anzahl der durchzuführenden Tests in Abhängigkeit von der Korngröße der Gesteine. Es existiert lediglich ein Empfehlung, wonach bei grobkörnigen Gesteinen zehn anstatt der sonst üblichen fünf Tests durchzuführen seien. In dieser Arbeit wird der Einfluss der Korngröße auf das Testergebnis in Abhängigkeit von der Anzahl der Tests untersucht. Dazu wurden an den getesteten Proben die Korngrößen bestimmt. Von den Korngrößendaten wurden die statistische Parameter Median und Interquartile-range, berechnet. Die CAI Ergebnisse nach fünf Ritztests und nach zehn Ritztest wurden dann mit dem Median und dem Interquartile-range der Korngrößen verglichen. Im untersuchten Korngrößenbereich wurde kein Einfluss der Korngröße auf die Differenzwerte von fünf und zehn Tests beobachtet. Daraus kann abgeleitet werden, dass im untersuchten Korngrößenbereich die Korngröße , entgegen den bisherigen Annahmen , keinen messbaren Einfluss auf das Ergebnis des CAI-Tests hat. [source]

NMR spectroscopic characterization of metoprolol/cyclodextrin complexes in aqueous solution: Cavity size dependency

JOURNAL OF PHARMACEUTICAL SCIENCES, Issue 7 2004
Yoichi Ikeda
Abstract The inclusion complex formation of a water-soluble ,1 -selective adrenoreceptor antagonist Metoprolol (Met) with ,-cyclodextrin (,-CyD), ,-cyclodextrin (,-CyD), ,-cyclodextrin (,-CyD), and 2-hydroxypropyl-,-cyclodextrin (HP-,-CyD) in aqueous solution was studied by ultraviolet (UV), circular dichroism (CD), and nuclear magnetic resonance (NMR) spectroscopies and the modes of interaction were assessed. Continuous variation plots revealed that Met forms the inclusion complexes with ,-CyD, ,-CyD, and HP-,-CyD in a stoichiometry of 1:1, whereas ,-CyD forms the 2:1 complex where two Met molecules are included in one ,-CyD cavity. NMR spectroscopic studies, including ROESY and GROESY techniques, clearly indicated that ,-CyD with the small cavity includes the methoxyethylbenzene moiety of Met molecule shallowly in the cavity, depositing the benzene and the methoxy moieties around the secondary and primary sides, respectively, of the cavity. In the case of the ,-CyD complex, the methoxyethylbenzene moiety is more deeply included in the cavity, and it is feasible that Met may be able to enter from both primary and secondary hydroxyl sides of the cavity, forming the 1:1 complex. On the other hand, two Met molecules are included probably in an antiparallel orientation in the large ,-CyD cavity, and the benzene moieties of Met are in contact with each other. © 2004 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 93:1659,1671, 2004 [source]

NMR spectroscopic characterization of inclusion complexes comprising cyclodextrins and gallated catechins in aqueous solution: cavity size dependency

MAGNETIC RESONANCE IN CHEMISTRY, Issue 4 2009
Takashi Ishizu
Abstract The structure of inclusion complexes of ,-cyclodextrin (,-CD), (,)-gallocatechin gallate (GCg), and (,)-epigallocatechin gallate (EGCg) in D2O was investigated using several NMR techniques. GCg formed a 1:1 inclusion complex with ,-CD in which the A and C rings of GCg were inserted deep at the head of the A ring into the ,-CD cavity from the wide secondary hydroxyl group side. In the 1:1 inclusion complex with GCg and ,-CD, the GCg moiety maintained a conformation in which the B and B, rings of GCg took both pseudoequatorial positions with respect to the C ring. The structure of the inclusion complex of GCg and ,-CD obtained from NMR experiments supported well that determined from PM6 semiempirical SCF MO calculations. However, 1H NMR experiments suggested that EGCg did not form any inclusion complex with ,-CD in D2O. The marked difference between GCg and EGCg in inclusion behavior toward ,-CD may be explained in terms of the stabilization energy calculated with the PM6 method. Copyright © 2008 John Wiley & Sons, Ltd. [source]

CO Combustion on Supported Gold Clusters

CHEMPHYSCHEM, Issue 9 2006
Matthias Arenz Dr.
Abstract Recent progress in the understanding of the fascinating catalysis of CO combustion by supported gold particles is summarized. Focusing on size-selected gold clusters consisting of only a few atoms, that is, the size regime with properties nonscalable from the bulk properties, we discuss the current knowledge of the different factors controlling the reactivity at the molecular level. These factors include the role of the oxide support, its defects, cluster charging as well as the structural fluxionality of clusters, the cluster size dependency, and the promotional effect of water. By combining experimental results with quantum mechanical ab initio calculations, a detailed picture of the reaction mechanism emerges. While similar mechanisms might be active for gold nanoparticles in the scalable size regime, it is shown that for different systems (defined by the cluster size, the support, experimental conditions, etc.) the reaction mechanism differs and, hence, no generalized explanation for the catalytic driving force of small gold particles can be given. [source]