Constrained optimization with stochastic feasibility regions applied to vehicle path planning

In real-time trajectory planning for unmanned vehicles, on-board sensors, radars and other instruments are used to collect information on possible obstacles to be avoided and pathways to be followed. Since, in practice, observations of the sensors have measurement errors, the stochasticity of the data has to be incorporated into the models. In this paper, we consider using a genetic algorithm for the constrained optimization problem of finding the trajectory with minimum length between two locations, avoiding the obstacles on the way. To incorporate the variability of the sensor readings, we propose a modified genetic algorithm, addressing the stochasticity of the feasible regions. In this way, the probability that a possible solution in the search space, say x, is feasible can be derived from the random observations of obstacles and pathways, creating a real-time data learning algorithm. By building a confidence region from the observed data such that its border intersects with the solution point x, the level of the confidence region defines the probability that x is feasible. We propose using a smooth penalty function based on the Gaussian distribution, facilitating the borders of the feasible regions to be reached by the algorithm.     

Nucleophilic addition of potassium alkynyltrifluoroborates to D-glucal mediated by BF3 x OEt2: highly stereoselective synthesis of alpha-C-glycosides

A convenient, mild and highly stereoselective method for C-glycosidation (alkynylation) of D-glucal with various potassium alkynyltrifluoroborates, mediated by BF3x OEt2 and involving oxonium intermediates, preferentially provides the alpha-acetylene glycoside products with good yields.     

Structural basis for selective inhibition of trypanosomatid glyceraldehyde-3-phosphate dehydrogenase: molecular docking and 3D QSAR studies

The glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is as an attractive target for the development of novel antitrypanosomatid agents. In the present work, comparative molecular field analysis and comparative molecular similarity index analysis were conducted on a large series of selective inhibitors of trypanosomatid GAPDH. Four statistically significant models were obtained ( r2 > 0.90 and q2 > 0.70), indicating their predictive ability for untested compounds. The models were then used to predict the potency of an external test set, and the predicted values were in good agreement with the experimental results. Molecular modeling studies provided further insight into the structural basis for selective inhibition of trypanosomatid GAPDH.     

High-energy X-ray absorption spectroscopy: a new tool for structural investigations of lanthanoids and third-row transition elements

This is the first systematic study exploring the potential of high-energy EXAFS as a structural tool for lanthanoids and third-row transition elements. The K-edge X-ray absorption spectra of the hydrated lanthanoid(III) ions both in aqueous solution and in solid trifluoromethanesulfonate salts have been studied. The K-edges of lanthanoids cover the energy range from 38 (La) to 65 keV (Lu), while the corresponding energy range for the L(3)-edges is 5.5 (La) to 9.2 keV (Lu). We show that the large widths of the core-hole states do not appreciably reduce the potential structural information in the high-energy K-edge EXAFS data. Moreover, for lanthanoid compounds, more accurate structural parameters are obtained from analysis of K-edge than from L(3)-edge EXAFS data. The main reasons are the much wider k range available and the absence of double-electron transitions, especially for the lighter lanthanoids. A comparative K- and L(3)-edge EXAFS data analysis of nonahydrated crystalline neodymium(III) trifluoromethanesulfonate demonstrates the clear advantages of K-edge analysis over conventionally performed studies at the L(3)-absorption edge for structural investigations of lanthanoid and third-row transition metal compounds. The coordination chemistry of the hydrated lanthanoid(III) ions in aqueous solution and solid trifluoromethanesulfonate salts, based on the results of both the K- and L(3)-edge EXAFS data, is thoroughly discussed in the next paper in this series (I. Persson, P. D'Angelo, S. De Panfilis, M. Sandstr?m, L. Eriksson, Chem. Eur. J. 2008, 14, DOI: 10.1002/chem.200701281).     

Regioselective monohydrolysis of per-O-acetylated-1-substituted-β-glucopyranosides catalyzed by immobilized lipases

The regioselective monohydrolysis of different peracetylated-β-glucopyranosides in aqueous media using immobilized preparations of three different lipases—those from Aspergillus niger (ANL), Candida rugose (CRL) and Candida antarctica B (CAL-B)—has been studied. Three very different immobilization strategies—covalent attachment, anionic exchange and interfacial activation on a hydrophobic support—were employed for each lipase. The role of the immobilization strategy and the effect of the presence of different moieties in the anomeric position of the substrate on the hydrolytic activities, specificities and regioselectivities of the lipases were investigated. For example, the PEI-ANL preparation exhibited 800 times higher activity than the octyl-ANL in the hydrolysis of 2-acetamido-2-deoxy-1-(4-nitrophenyl)-3,4,6-tri-O-acetyl-β-d-glucopyranoside—producing 4-OH derivative in 18% yield—whereas the octyl-ANL was five times more active than the PEI-ANL in the hydrolysis of 1-(4-nitrophenyl)-2,3,4-tri-O-acetyl-β-d-xylopyranoside, producing 4-OH monohydroxy product in >99% yield.The octyl-CRL preparation hydrolyzed regioselectively 3,4,6-tri-O-acetyl-glucal in position 6 in 68% yield while the PEI-CRL produced the 3-OH product in 11% yield, although with moderate specificity. The CNBr-CAL-B hydrolyzed specifically and regioselectively the glucal producing the 3-OH product in >99% yield.     

Thermal analysis and gas chromatography coupled mass spectrometry analyses of hydroxypropyl-β-cyclodextrin inclusion complex containing Lippia gracilis essential oil

Inclusion complexation with cyclodextrins is an effective way to improve stability and turn liquid materials into re-dispersible and easy-to-handle powders. In the present work, the complexation of L. gracilis essential oil, already recognized as a potent larvicide material, with hydroxylpropyl-β-cyclodextrin was performed using slurry and paste procedures and the complexes obtained were evaluated. The gas chromatography coupled to mass spectrometry (GC/MS) analysis showed a total volatile content of 99.24% in the L. gracilis oil. The characterization of the complex involved the analysis of the original essential oil, the surface, and the total extracted oils. The major components in L. gracilis essential oil were identified as carvacrol (23.52%), p-cymene (15.82%), γ-terpinene (14.17%), and thymol (7.27%). GC/MS results showed significant differences between the original oil, the slurry, and paste complexation. Thermal characterization indicates the occurrence of complexation, mainly in paste complexes, which presents a TG–DTA peak at 230–275 °C, probably related to oil loss.     

Cashew tree wood flour activated with cashew nut shell liquid for the production of functionalized composites

This work is aimed at the one-step chemical modification of the surface of cashew wood flour particles using the technical grade cashew nut shell liquid (CNSL). The goal is to develop an alternative way to introduce chemically active sites on the surface of the particles, which allows the addition of new functionalities to such particles. The influence of time and temperature and catalyst on the substitution of lignocellulosic hydroxyls with cardanol/cardol urethane derivatives was evaluated by thermogravimetric analysis, scanning electron microscopy, Fourier-transform infrared spectroscopy (FTIR), and contact angle measurements. The mechanical behavior of the modified particles in polypropylene composites was also evaluated by mechanical testing and dynamic mechanical thermal analysis. The FTIR, thermogravimetry, and contact angle results indicated changes on the particle surface, and the mechanical and thermomechanical behavior of the mercerized and modified particles in the composites was found to be similar. These results point that the CNSL approach is a viable way to chemically modify cashew wood flour particle surfaces, while maintaining their properties.     

Interior-point methods applied to the AC active-reactive optimal power-flow problem using cartesian coordinates

The primal dual interior point methods are developed to the AC active and reactive optimal power flow problem. The representation of the tensions through cartesian coordinates is adopted, once the Hessian is constant and the Taylor expansion is accurate for the second order term. The advantage of working with polar coordinates, that easily model the tension magnitudes, lose importance due to the efficient treatment of inequalities proportionated by the interior point methods. Before the application of the method, the number of variables of the problem is reduced through the elimination of free dual variables. This elimination does not modify the sparse pattern of the problem. The linear system obtained can be further reduced to the dimension of twice the number of buses also with minor changes in the sparse structure of the matrices involved. Moreover, the final matrix is symmetric in structure. This feature can be exploited reducing the computational effort per iteration. Computational experiments for IEEE system problems are presented for several starting point strategies showing the advantages of the proposed approach. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

A Robust Flow-Based System for the Spectrophotometric Determination of Cr(VI) in Recreational Waters

A flow-based method for the spectrophotometric determination of chromium (VI) in recreational waters with different salinities was developed. Chromium can occur in the environment in different oxidation states with different related physiological properties. With regard to chromium, the speciation is particularly important, as the hexavalent chromium is considered to be carcinogenic. To achieve that purpose, the use of the diphenylcarbazide (DPC) selective colored reaction with the hexavalent chromium was the chosen strategy. The main objective was to develop a direct and simple spectrophotometric method that could cope with the analysis of different types of environmental waters, within different salinity ranges (fresh to marine waters). The potential interference of metal ions, that can usually be present in environmental waters, was assessed and no significant interferences were observed (<10%). For a complete Cr(VI) determination (three replicas) cycle, the corresponding reagents consumption was 75 µg of DPC, 9 mg of ethanol and 54 mg of sulfuric acid. Each cycle takes about 5 min, including the system clean-up. The limit of detection was 6.9 and 12.2 µg L⁻¹ for waters with low and high salt content, respectively. The method was applied for the quantification of chromium (VI) in both fresh and marine water, and the results were in agreement with the reference procedure.     

Haloacetylated enol ethers. 11. Synthesis of 1-methyl- and 1-phenyl pyrazole-3(5)-ethyl esters. A one-pot procedure

A one-pot synthesis of 1-methyl- and 1-phenylpyrazole-3(5)-ethyl esters 2,3a-e by the cyclocondensation of β-alkoxyvinyl trichloromethyl ketones 1a-e with methyl and phenyl hydrazine hydrochloride under mild conditions, is reported. A study using compounds 1a-e with different substituents proved that these are versatile building blocks for the synthesis of pyrazole derivatives, having a 3(5)-ethoxycarbonyl substituent in good yields (60–89%). The hydrazine and β-alkoxyvinyl trichloromethyl ketone substituent effects on the reaction regiochemistry on the formation of the 1,3- and 1,5-isomer were observed.