Crystal and molecular structure of a root inhibitor fromEucalyptus grandis, 4-ethyl-1-hydroxy-4,8,8,10,10-pentamethyl-7,9-dioxo-2,3-dioxabicyclo [4.4.0]decene-5

The crystal structure of C₁₅H₂₂O₅, a root inhibitor isolated from adult leaves ofEucalyptus grandis, has been determined by direct methods with Cuk diffractometer data and refined by full-matrix least-squares calculations toR = 0·046 for 1829 statistically significant reflexions. The compound, a racemate, crystallizes in the monoclinic space groupP2₁/c, with unit cell dimensionsa = 11·767,b = 12·063,c = 10·906 Å, = 103·2° andZ = 4. The molecular skeleton consists of a 2,3-dioxabicyclo[4.4.0]decene system with one hydroxyl, two carbonyl, one ethyl and five methyl side groups. The dihedral angle at the peroxide bond is 76·8° and the O-O bond distance is 1·480 Å. The molecules are linked in the c direction by hydrogen bonds between the hydroxyl group and one of the carbonyl oxygen atoms.The author is grateful to Professor W. D. Crow for suggesting the problem and for crystals ofG1, to Dr A. McL. Mathieson (Division of Chemical Physics, C.S.I.R.O.), in whose laboratory the data were collected, and Mr J. Fridrichsons for their advice and continued interest, to Dr W. A. Denne (Division of Chemical Physics, C.S.I.R.O.) and Mr B. J. Poppleton (Division of Forest Products, C.S.I.R.O.) for help and advice in the data collection and for the use of data reduction programs and to Dr D. A. Wright (Chemical Physics Group, Department of Supply) for several computer programs used in this work.     

Comparison and improvement of commonly applied statistical approaches for identification of plant species from IR spectra

Fourier transform infrared spectroscopy (FTIR) has been studied many times in the context of identification of plant, fungal and bacterial species. Infrared spectra are commonly analyzed using multivariate statistical methods such as cluster analysis (CA), principal component analysis (PCA), partial least squares analysis (PLS) and discriminant analysis (DA). In this study, a univariate statistical method for analysis of variance (ANOVA) was used to reduce the number of variables before applying the multivariate methods. Analyzing variables using ANOVA or a combination of ANOVA with CA produced better results. Here, experiments were carried out by performing ANOVA using the first derivative of the spectra instead of the original spectra or its second derivative because using the first‐derivative variables led to improved distinction between species. Different results were obtained by applying different validation methods. The leave‐one‐out validation method gave higher results than the validation‐with‐training and validation sample sets, thus indicating the non‐objectivity of the leave‐one‐out validation method. Copyright © 2010 John Wiley & Sons, Ltd.     

The Effect of Hofmeister Salts on the LCST Transition of Poly(2‐oxazoline)s with Varying Hydrophilicity

The influence of Hofmeister salts was investigated on the cloud point of three poly(2‐oxazoline)s, namely poly(2‐ethyl‐2‐oxazoline) [PEtOx], poly(2‐n‐propyl‐2‐oxazoline) [PnPropOx], and poly(2‐isopropyl‐2‐oxazoline) [PiPropOx]. In addition, a comb polymer based on oligo‐2‐ethyl‐2‐oxazoline side chains and a methacrylate backbone (POEtOxMA) was included in this investigation. It was found that the ionic response of the poly(2‐oxazoline)s strongly depends on their hydrophilicity. The comb polymer POEtOxMA revealed a strikingly similar response to the salts as linear PEtOx even though the cloud points of the polymers in water differ. This indicates that the architecture does not significantly influence the effect of the Hofmeister ions, even though there is a difference in the absolute cloud point.

     

Fractionation in radiation treatment planning

Radiotherapy treatment is often delivered in a fractionated manner over a period of time. Emerging delivery devices are able to determine the actual dose that has been delivered at each stage facilitating the use of adaptive treatment plans that compensate for errors in delivery. We formulate a model of the day-to-day planning problem as a stochastic program and exhibit the gains that can be achieved by incorporating uncertainty about errors during treatment into the planning process. Due to size and time restrictions, the model becomes intractable for realistic instances. We show how heuristics and neuro-dynamic programming can be used to approximate the stochastic solution, and derive results from our models for realistic time periods. These results allow us to generate practical rules of thumb that can be immediately implemented in current planning technologies.     

Angular distributions of desorbing N2 in thermal N2O decomposition on Rh(1 0 0)

The angular distribution of desorbing N₂ was studied in the decomposition of N₂O(a) on Rh(1 0 0) at 60-140 K by means of angle-resolved temperature-programmed desorption. N₂ desorption shows two peaks at around 80 K and 110 K. At low N₂O coverage, the former collimates far from the surface normal toward the [0 0 1] direction, whereas at high coverage, the desorption sharply collimates along the surface normal. The adsorption form of N₂O and its dissociation were also examined by DFT-GGA calculations. Dissociating N₂O is proposed to be lying along the [0 0 1] direction at low coverage and to change to an upright form bonding through the terminal oxygen at high coverage.     

Addition of lithiated C-nucleophiles to 2,3-O-isopropylidene-D-erythronolactone: stereoselective formation of a furanose C-disaccharide

Addition of PhLi and lithiated dithianes to 2,3-O-isopropylidene-D-erythronolactone affords lactols, which are reduced with Et3SiH to the corresponding C-glycosides, the structures of two of which have been solved by X-ray diffraction. The use of a d-ribose-derived lithiated dithiane nucleophile in this chemistry allows for the convenient construction of a furanose C-disaccharide.     

Poly(cyclic imino ether)s Beyond 2‐Substituted‐2‐oxazolines

2‐Oxazolines (2‐OZO) are 5‐membered cyclic imino ethers whose cationic ring‐opening polymerization (CROP) mechanism and resulting polymer properties are extensively studied. However, also 6‐ and 7‐membered cyclic imino ethers can be polymerized via CROP. Together with the much less studied 4‐ and 5‐substituted main‐chain chiral poly(2‐oxazoline)s (P‐2‐OZO), these compounds are interesting monomers to enhance the versatility of (co)poly(cyclic imino ether)s. To emphasize the potential of such alternative cyclic imino ether monomers, we provide an overview on the polymerizations of 2‐oxazine (2‐OZI) and chiral 4‐ and 5‐substituted 2‐OZO as well as of selected properties of the resulting polymers. In addition, the hydrolysis of these polymers into the corresponding poly(alkylene imine)s will be addressed.

     

Triazole, benzotriazole, and naphthotriazole as copper corrosion inhibitors: I. Molecular electronic and adsorption properties

The gas-phase adsorption of 1,2,3-triazole, benzotriazole, and naphthotriazole-considered as corrosion inhibitors-on copper surfaces was studied and characterized using density functional theory (DFT) calculations. We find that the molecule-surface bond strength increases with increasing molecular size, thus following the sequence: triazole相似文献   

Characterization of laser droplet formation by reflected light

The subject of this experimental investigation is a novel laser droplet formation (LDF) process. During the LDF process, droplets are formed by melting the tip of a wire using a laser pulse. The goal of our research is to develop a non-contact method for characterization of the LDF process. For this purpose we employ the signals of the laser light that is reflected from the tip of the wire. The experiments were performed with nickel and tin-alloy wire. Results show that in-process characterization of various phases of the LDF process, like melting of the wire tip and formation of a molten pendant droplet is possible regardless of the wire material. In addition, a method for post-process detection of droplet detachment has been developed. Using the statistically defined threshold value, 99.2% and 97.8% detection reliability of droplet detachment was achieved in the case of nickel and tin-alloy wire, respectively.