| 1. |
- Bardage, Stig, et al.
(författare)
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The effect of natural product treatment of southern yellow pine on fungi causing blue stain and mold
- 2014
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Ingår i: International Biodeterioration & Biodegradation. - : Elsevier BV. - 0964-8305 .- 1879-0208. ; 86:B, s. 54-59
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Tidskriftsartikel (refereegranskat)abstract
- Blue stain and mold growth on wood can be aesthetically unappealing, but mold growth can also potentially trigger health related issues. In this study, a screening of the effect of selected natural products and derivatives of natural products including essential oils, plant based monomers, and shellfish exoskeleton compounds on the inhibition of blue stain fungi and mold fungi in southern yellow pine veneers and cellulose filter paper. The treatment of the substrates, the weight percent gain of the natural products, and the inhibition effect is presented. The natural products have been investigated previously, but most have not been applied to wood or investigated with regards to blue stain or mold growth. The specimens were treated by dipping, wrapping in foil, and then heating at 105°C for 24h in order to encourage reaction or grafting of the natural products to the wood. A selection of seven additives each exhibited significant protection against blue stain colonization in Petri dish tests and these were studied more in-depth. These included tea tree oil, propyl gallate, hydrogenated gum oil, salicylic acid, cinnamon bark oil, butylene oxide, and furfural. The salicylic acid, tea tree oil, and cinnamon bark oil had the least amount of mold growth after four weeks in the mold chamber test, and have been previously reported to have a mechanism of antifungal activity resulting from their ability to disrupt the fungal cell wall. Propyl gallate veneer was the only specimen that had a lower pH and that would be considered unfavorable to mold growth. While furfural, salicylic acid, and cinnamon bark oil treated veneers all had more hydrophobic surfaces when compared to untreated wood.
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| 2. |
- Fogarty, Heather A., et al.
(författare)
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Calculation of relative energies of permethylated oligosilane conformers in vapor and in alkane solution
- 2006
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Ingår i: Journal of Physical Chemistry B. - : American Chemical Society (ACS). - 1520-6106 .- 1520-5207. ; 110:50, s. 25485-25495
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Tidskriftsartikel (refereegranskat)abstract
- The geometries of 35 conformers of Me(SiMe2) nMe (n= 4, 1; n = 5, 2; n = 6, 3; n = 7, 4) were optimized at the MP2/VTDZ level, and CCSD(T) single-point calculations were done at three MP2/VTDZ conformer geometries of 1. The relative ground-state energies of the conformers of 1-4 in the gas phase were obtained from the MP2/VTDZ electronic energy, zero- point vibrational energy, and thermal corrections at 0, 77, and 298 K. Relative energies in an alkane solvent at 77 and 298 K were obtained by the addition of solvation energies, obtained from the SM5.42R model. The calculated energies of 26 of the conformers (n = 4-6) have been least-squares fitted to a set of 15 additive increments associated with each Si-Si bond conformation and each pair of adjacent bond conformations, with mean deviations of 0.06-0.20 kcal/mol. An even better fit for the energies of 24 conformers (mean deviations, 0.01-0.09 kcal/mol) has been obtained with a larger set of 19 increments, which also contained contributions from selected combinations of conformations of three adjacent bonds. The utility of the additive increments for the prediction of relative conformer energies in the gas phase and in solution has been tested on the remaining nine conformers (n = 6, 7). With the improved increment set, the average deviation from the SM5.42R//MP2 results for solvated conformers at 298 K was 0.18 kcal/mol, and the maximum error was 0.98 kcal/mol.
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| 3. |
- Villaume, Sebastien, et al.
(författare)
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Triplet-state aromaticity of 4n pi-electron monocycles : Analysis of bifurcation in the pi contribution to the electron localization function
- 2008
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Ingår i: ChemPhysChem. - : Wiley. - 1439-4235 .- 1439-7641. ; 9:2, s. 257-264
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Tidskriftsartikel (refereegranskat)abstract
- The pi contribution to the electron localization function (ELF) is used to compare 4n pi- and (4n+2)pi-electron annulenes, with particular focus on the aromaticity of 4n pi-electron annulenes in their lowest triplet state. The analysis is performed on the electron density obtained at the level of OLYP density functional theory, as well as at the CCSD and CASSCF ob initio levels. Two criteria for aromaticity of all-carbon annulenes ore set up: the span in the bifurcation values Delta BV(ELE pi) should be small, ideally zero, and the bifurcation value for ring closure of the pi basin RCBV(ELF pi) should be high (>= 0.7). On the basis of these criteria, nearly all 4n pi-electron annulenes are aromatic in their lowest triplet states, similar to (4n+2)pi-electron annulenes in their singlet ground states. For singlet biradical cyclobutadiene and cyclo-octatetraene constrained to D-4h and D-8h symmetry, respectively, the RCBV(ELF pi) at the CASSCF level is lower (0.531 and 0.745) than for benzene (0.853), even though they have equal proportions of alpha- and beta-electrons.
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| 4. |
- Zhu, Jun, et al.
(författare)
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Aromaticity Effects on the Profiles of the Lowest Triplet-State Potential-Energy Surfaces for Rotation about the CC Bonds of Olefins with Five-Membered Ring Substituents : An Example of the Impact of Baird's Rule
- 2013
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Ingår i: Chemistry - A European Journal. - : Wiley. - 0947-6539 .- 1521-3765. ; 19:32, s. 10698-10707
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Tidskriftsartikel (refereegranskat)abstract
- A density functional theory study on olefins with five-membered monocyclic 4n and 4n+2 -electron substituents (C4H3X; X=CH+, SiH+, BH, AlH, CH2, SiH2, O, S, NH, and CH-) was performed to assess the connection between the degree of substituent (anti)aromaticity and the profile of the lowest triplet-state ( (1)) potential-energy surface (PES) for twisting about olefinic CC bonds. It exploited both Huckel's rule on aromaticity in the closed-shell singlet ground state (S-0) and Baird's rule on aromaticity in the lowest * excited triplet state. 2CH(C4H3X) were categorized as set A and set B olefins depending on which carbon atom (C2 or C3) of the C4H3X ring is bonded to the olefin. (0)-antiaromatic/ (1)-aromatic (C5H4+) to strongly S-0-aromatic/ (1)- antiaromatic (C5H4-). Our hypothesis is that the shapes of the (1) PESs, as given by the energy differences between planar and perpendicularly twisted olefin structures in (1) [E( (1))], smoothly follow the changes in substituent (anti)aromaticity. Indeed, correlations between E( (1)) and the (anti)aromaticity changes of the C4H3X groups, as measured by the zz-tensor component of the nucleus-independent chemical shift NICS( (1);1)(zz), are found both for sets A and B separately (linear fits; r(2)=0.949 and 0.851, respectively) and for the two sets combined (linear fit; r(2)=0.851). For sets A and B combined, strong correlations are also found between E( (1)) and the degree of S-0 (anti)aromaticity as determined by NICS(S-0,1)(zz) (sigmoidal fit; r(2)=0.963), as well as between the (1) energies of the planar olefins and NICS(S-0,1)(zz) (linear fit; r(2)=0.939). (1) PESs suitable for adiabatic Z/E photoisomerization.
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