30 research outputs found
Intra-annual height growth dynamics of Scots and lodgepole pines and its relationship with meteorological parameters in central Latvia
The Scots pine (Pinus sylvestris L.) is the second-most widely used tree species in
forestry in Latvia and is the only species used for afforestation on nutrient poor soils that cover
considerable forest land in Latvia. Several studies have shown that, in such conditions, the
lodgepole pine (Pinus contorta var. latifolia) may be more productive in terms of biomass and
yield. It is important to consider climate change studies to assess the potential for a larger-scale
use of the lodgepole pine in forestry. The aim was to assess the intra-annual height growth
patterns of both species, the differences between them, and the influence of meteorological
parameters on their height growth. Their height growth was monitored on a weekly basis in two
sampling sites in central Latvia, and the height increment curves were described by Gompertzâs
model. The height growth dynamics of individual trees and species differed notably, indicating
the potential for the selection of the best-adapted genotypes. Our results indicate that the early
onset of the active growth phase might be the most important factor determining the total height
increment for both species. Temperature-related meteorological parameters were the only ones
with a statistically significant influence on pines height growth and only when at least one of the
variables were standardised prior to the analysis. A temperature increase had a slightly stronger
positive effect on the growth of the lodgepole pine, indicating that it might be suitable for more
intensive use in forestry under the climate change scenarios for Latvia
Polyhedral oligomeric silsesquioxane bound fulleropyrrolidines
The first reported examples of polyhedral oligomeric silsesquioxane (POSS) cages containing a fulleropyrrolidine species are reported herein. Monosubstituted POSS-dioxalane species were synthesized through the hydrosilylation of a silyl-dioxalane with mono-vinyl substituted POSS. Subsequent deprotection yielded the desired aldehyde functionality. An alternative synthetic pathway, involving the nucleophilic substitution of mono-benzyl chloride POSS with 4-hydroxybenzaldehyde yielded the desired aldehyde functionality. Each mono-aldehyde POSS was then reacted with N-methylglycine and C60 to yield the desired POSS fulleropyrrolidines. The prepared compounds were characterized by multinuclear NMR, electrospray mass spectrometry, elemental analysis, UV-vis, fluorescence and optical power limiting measurements
Polyhedral oligomeric silsesquioxane-bound iminofullerene
Polyhedral oligomeric silsesquioxane (POSS) cages containing an iminofullerene species are reported herein.Monosubstituted benzyl chloride POSS was synthesized, and subsequently reactedwith sodium azide to form mono benzyl azide POSS. The azide was subsequently reacted with C60 in anhydrous, degassed toluene to yield the desired POSS iminofullerene compound. The prepared compounds were characterized by multinuclear NMR, electrospray mass spectrometry, elemental analysis, UV-vis, fluorescence and optical power limitingmeasurements
POSS Fulleropyrrolidines
The first reported examples of polyhedral oligomeric silsesquioxane (POSS) cages containing a fulleropyrrolidine species are reported herein. Monosubstituted POSS-dioxalane species were synthesized through the hydrosilylation of a silyl-dioxalane with mono-vinyl substituted POSS. Subsequent deprotection yielded the desired aldehyde functionality. An alternative synthetic pathway, involving the nucleophilic substitution of mono-benzyl chloride POSS with 4-hydroxybenzaldehyde yielded the desired aldehyde functionality. Each mono-aldehyde POSS was then reacted with N-methylglycine and C60 to yield the desired POSS fulleropyrrolidines. The prepared compounds were characterized by multinuclear NMR, electrospray mass spectrometry, UV-VIS, fluorescence and optical power limiting measurements
Ethynylbenzene Monolayers on Gold: A Metal-Molecule Binding Motif Derived from a Hydrocarbon
Exposure of a Au(111) surface to ethynylbenzene in solution leads to the formation of a bound monolayer. A chemisorption process occurs to give a stable layer consisting of oxygen-containing hydrocarbon species. Ethynylbenzene itself does not oxidize under the deposition conditions indicating that the gold surface facilitates the oxidation process. Calculations show that ethynylbenzene and its oxidation products phenylacetic acid and phenyloxirane have positive binding energies to the gold surface. 1,4-Diethynylbenzene also binds to Au(111) and anchors gold nanoparticles deposited from solution to form dense, semiregular arrays. © 2007 American Chemical Society