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Chemical Applications (chemical + application)
Selected AbstractsSilica-Based Materials for Advanced Chemical Applications.ANGEWANDTE CHEMIE, Issue 45 2009Von Mario Pagliaro. Royal Society of Chemistry, Cambridge 2009. 192,pp., geb. £,70.00.,ISBN 978-1847558985 [source] An improved algorithm for analytical gradient evaluation in resolution-of-the-identity second-order Møller-Plesset perturbation theory: Application to alanine tetrapeptide conformational analysisJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 5 2007Robert A. Distasio JR. Abstract We present a new algorithm for analytical gradient evaluation in resolution-of-the-identity second-order Møller-Plesset perturbation theory (RI-MP2) and thoroughly assess its computational performance and chemical accuracy. This algorithm addresses the potential I/O bottlenecks associated with disk-based storage and access of the RI-MP2 t -amplitudes by utilizing a semi-direct batching approach and yields computational speed-ups of approximately 2,3 over the best conventional MP2 analytical gradient algorithms. In addition, we attempt to provide a straightforward guide to performing reliable and cost-efficient geometry optimizations at the RI-MP2 level of theory. By computing relative atomization energies for the G3/99 set and optimizing a test set of 136 equilibrium molecular structures, we demonstrate that satisfactory relative accuracy and significant computational savings can be obtained using Pople-style atomic orbital basis sets with the existing auxiliary basis expansions for RI-MP2 computations. We also show that RI-MP2 geometry optimizations reproduce molecular equilibrium structures with no significant deviations (>0.1 pm) from the predictions of conventional MP2 theory. As a chemical application, we computed the extended-globular conformational energy gap in alanine tetrapeptide at the extrapolated RI-MP2/cc-pV(TQ)Z level as 2.884, 4.414, and 4.994 kcal/mol for structures optimized using the HF, DFT (B3LYP), and RI-MP2 methodologies and the cc-pVTZ basis set, respectively. These marked energetic discrepancies originate from differential intramolecular hydrogen bonding present in the globular conformation optimized at these levels of theory and clearly demonstrate the importance of long-range correlation effects in polypeptide conformational analysis. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Molecular strategies to enhance the genetic resistance of grapevines to powdery mildewAUSTRALIAN JOURNAL OF GRAPE AND WINE RESEARCH, Issue 2010I.B. DRY Abstract The Eurasian winegrape Vitis vinifera has little or no genetic resistance to the major fungal pathogens, powdery mildew (Erysiphe necator) and downy mildew (Plasmopora viticola). These pathogens were first introduced into French vineyards from North America in the 1800s before spreading to all major grape producing regions of the world. As a result, grape production is highly dependent on the use of fungicides. With the increasing financial and environmental costs of chemical application and the emergence of fungicide-resistant strains, the introduction of natural genetic resistance against these fungal pathogens is a high priority for viticultural industries worldwide. We are utilising a number of different molecular approaches to increase our understanding of the basis of resistance to these important major fungal pathogens and to identify potential new sources of genetic resistance. This review will outline the progress and the potential of each of these different molecular strategies to the generation of fungal-resistant grapevine germplasm. [source] Spatial distribution of ants (Hymenoptera: Formicidae), vine mealybugs and mealybug parasitoids in vineyardsJOURNAL OF APPLIED ENTOMOLOGY, Issue 4 2010N. Mgocheki Abstract The mutualistic association between some ant species and honeydew-producing Hemiptera has been shown to influence the distribution patterns and abundance of these hemipterans and their natural enemies. We studied the spatial distribution patterns of three ant species, mealybugs and mealybug parasitoids for two consecutive growing seasons on three wine grape farms in the Western Cape, South Africa. During the study period, no ant or mealybug controls were applied. Ant and mealybug monitoring was conducted on a total of 21 ha using a presence/absence sampling system, while parasitoids were collected from infested mealybug females. Spatial analysis by distance indices was used to analyse spatial distribution of insects and ArcViewÔ was used to map the gap, patch and local association indices where significant association and disassociation occurred. Significant associations were found between some ants and parasitoids, while significant disassociations between the ants Crematogaster peringueyi and Linepithema humile; and also between Crematogaster peringueyi and Anoplolepis steingroeveri were found. Interspecific competition between ant species could play a role in the distribution of parasitoids and mealybugs. Our results stress the importance of monitoring for ants and mealybugs and further highlight the importance of restricted chemical applications against ants during the growing season. [source] Biology and control of Dicladispa gestroi Chapuis (Col., Chrysomelidae)JOURNAL OF APPLIED ENTOMOLOGY, Issue 9-10 2001V. Delucchi The beetle Dicladispa gestroi is known only from Madagascar, where it is considered to be a pest of rice. Research were carried out from 1885 to 1994 in the Alaotra lake region, the main rice-producing area of the country, characterized by a warm rainy season from October to April and a cool dry season from April to October. The adult beetles invade the rice nurseries and the first direct-seeded fields at the beginning of the rainy season; they have a gregarious behaviour and their feeding activity, together with the mines bored by the larvae, determines a change of colour from green to pale yellow in the damage areas, which resemble outbreak areas of rice leafhoppers. Oviposition takes place only on young rice plants in the tillering stage. Females emerging after the end of February enter a reproductive diapause and leave the rice fields to ,hibernate'. Temperature summations for the egg, larval, and pupal development, as well as for the preoviposition period have been calculated. There is no yield loss up to a larval density of 0.6 per leaf and this economic injury level is seldom exceeded in the Alaotra lake region. Life tables carried out under field conditions show that chalcid parasitoids are the main mortality factor and are responsible for the collapse of entire outbreak areas. Since the discovery of the rice yellow mottle virus in 1989 in the Alaotra lake region and the disease transmission by chrysomelids, the pest status of D. gestroi has changed and control measures have to be applied. However, to avoid interference with the action of the parasitoids, chemical applications should be limited to rice nurseries. [source] Microbial metagenomes: moving forward industrial biotechnologyJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 5 2007Manuel Ferrer Abstract Biotechnology, in terms of exploitation of catalytic activities for industrial applications, is increasingly recognized as one of the pillars of the knowledge-based economy that we are heading for. Comprehensive knowledge of enzymology should be of practical importance for effective intervention on whole cell processes and enzymatic networks. Over the last decade metagenome-based technologies have been developed to take us farther and deeper into the enzyme universe from uncultivable microbes. This sophisticated platform, which identifies new enzymes from vast genetic pools available, and assesses their potential for novel chemical applications, should be increasingly important in the discovery of advanced biotechnological resources. Copyright © 2007 Society of Chemical Industry [source] Experimental and statistical analysis methods for peptide detection using surface-enhanced Raman spectroscopyJOURNAL OF RAMAN SPECTROSCOPY, Issue 3 2008Breeana L. Mitchell Abstract Surface-enhanced Raman spectroscopy (SERS) has the potential to make a significant impact in biology research due to its ability to provide information orthogonal to that obtained by traditional techniques such as mass spectrometry (MS). While SERS has been well studied for its use in chemical applications, detailed investigations with biological molecules are less common. In addition, a clear understanding of how methodology and molecular characteristics impact the intensity, the number of peaks, and the signal-to-noise of SERS spectra is largely missing. By varying the concentration and order of addition of the SERS-enhancer salt (LiCl) with colloidal silver, we were able to evaluate the impact of these variables on peptide spectra using a quantitative measure of spectra quality based on the number of peaks and peak intensity. The LiCl concentration and order of addition that produced the best SERS spectra were applied to a panel of synthetic peptides with a range of charges and isoelectric points (pIs) where the pI was directly correlated with higher spectral quality. Those peptides with moderate to high pIs and spectra quality scores were differentiated from each other using the improved method and a hierarchical clustering algorithm. In addition, the same method and algorithm was applied to a set of highly similar phosphorylated peptides, and it was possible to successfully classify the majority of peptides on the basis of species-specific peak differences. Copyright © 2008 John Wiley & Sons, Ltd. [source] Silica Reinforced Organic,Inorganic Hybrid Polyurethane Nanocomposites From Sustainable ResourceMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 4 2010Deewan Akram Abstract Polyol/nanosilica organic,inorganic hybrids (Si/Lpol) were prepared through facile sol,gel chemistry. Tetraethoxyorthosilane (TEOS) and linseed polyol (Lpol) obtained by hydroxylation of linseed oil were used as inorganic and organic precursors, respectively. Si/Lpol was further treated with toluene-2,4-diisocyanate (TDI) to obtain silica embedded polyurethane (Si/LPU). The structure of the organic,inorganic hybrid was confirmed by FTIR, 1H NMR, and 13C NMR spectral analysis. The polyol/nanosilica network shows strong interaction with the remnant polyol backbone through hydrogen bonding, which also has bearing on Tg of polymers. Morphological studies of Si/LPU show the formation of uniform, spherical silica nanoparticles of 2,30,nm size embedded in the polymer matrix. Si/LPU was further reinforced with 2 and 5,wt.-% fumed silica (FS-Si/LPUs); their morphology revealed a carpet layer formation on top of Si/LPU. Thermogravimetric analysis showed improved thermal stability of Si/LPU and FS-Si/LPUs. The polymers exhibit mild to moderate antibacterial behavior against E. coli and S. aureus, respectively, and will pave way in plethora of biological and chemical applications as coating materials. [source] | ||||||||||