1H and 13C NMR assignments for two new cordiaquinones from roots of Cordia leucocephala

From the roots of Cordia leucocephala (Boraginaceae), two new meroterpenoid naphthoquinones, 6‐[10‐(12,12‐dimethyl‐13α‐hydroxy‐16‐methenyl‐cyclohexyl)ethyl]‐1,4‐naphthalenedione (cordiaquinone L) and 5‐methyl‐6‐[10‐(12,12‐dimethyl‐13β‐hydroxy‐16‐methenyl‐cyclohexyl)methyl‐1,4‐naphthalenedione (cordiaquinone M) were isolated. Their structures were elucidated after detailed 1D and 2D NMR (COSY, HSQC, HMBC and NOESY) data analyses and comparison with literature data for analogous compounds. Copyright © 2008 John Wiley & Sons, Ltd.     

Optical studies of carbon nanotubes and nanographites

Resonance Raman and photoluminescence excitation (PLE) spectroscopies are used to study the optical properties of different types of carbon nanostructures such as carbon nanotube, nanoribbons, nanographites and graphite edges. In the resonance Raman experiments of carbon nanotubes, the (n,m) assignment is obtained by comparing the experimental and theoretical diameter and chirality dependence of the optical transitions. The influence of the environment on the optical transitions of the nanotubes is also obtained in the Raman experiments. The PLE measurements in different samples of carbon nanotubes show both direct and phonon-assisted optical transitions, and the results give new evidences that the optical transitions in nanotubes have an excitonic character, which is very strong for the low energy transitions. We also analyze the Raman spectra of nanoribbons and nanographites, showing that this technique is an important tool for defect characterization in graphitic materials, and can be used to distinguish the atomic structure of the graphite edges.     

Optical properties of Er doped GeO2-PbO glass: Effect of doping with Bi2O3

The optical properties of binary and ternary germanate glasses 40.3GeO₂-59.7PbO, 31.3GeO₂-26.8PbO-41.9Bi₂O₃ and 31.5GeO₂-40.4PbO-28.1Bi₂O₃ (wt%) doped with Er³⁺ were investigated. The Judd-Ofelt intensity parameters were calculated and the near-infrared luminescence as well as the upconversion efficiency was analyzed. We observed that the ternary germanate glass containing the highest concentration of Bi₂O₃ presented the largest emission bandwidth for ⁴I_13/2 → ⁴I_15/2 transition and the highest infrared-to-visible upconversion efficiency among the samples studied. These results demonstrate that not only the presence of Bi₂O₃ but also the careful choice of its molecular weight plays a key role in optimizing parameters for using germanate glasses for photonics applications.     

Experimental detection of relaxation phenomena in Rb2HfF6 by perturbed angular correlations

The differential perturbed angular correlation spectrum of ¹⁸¹Ta in Rb₂HfF₆ was studied as a function of temperature. The results indicate the existence of a temperature dependent mixture of pure static quadrupole interactions and pure multipole relaxation due to fluctuating electric quadrupole interactions.     

Solid-state 29Si, 113Cd, 119Sn, and 31P NMR studies of II-IV-P2 semiconductors

Solid-state ²⁹Si, ¹¹³Cd, ¹¹⁹Sn, and ³¹P MAS NMR spectra are reported on a series of II-IV-P₂ compounds. In favorable cases (e.g., high degree of crystallinity, low concentration of unpaired electrons), well-defined spectra, with sharp lines for each specific nearest-neighbor configuration, are observed; in such cases, expected J coupling patterns are also seen. High-resolution solid-state NMR studies of this type provide useful information on structure (disorder), doping, and electron-mediated coupling in semiconductor systems.     

An improved scheme for accelerating the convergence of the simulated annealing algorithm applied to real world problems

When formulated in mathematical terms, the problem of zoning a protected natural area subject to both box and spatial constraints results in a large combinatorial optimization problem belonging to the NP-hard class. These facts suggest the need to apply a heuristic approach. In this contribution a new proposal to decrease the control parameter, known as temperature, in the simulated annealing algorithm is presented. The strategy is based on that proposed by Lundy and Mees [4], and developed in order to decrease the running time of the algorithm applied to large scale problems. When applied to solving small-size simulated problems, results were indistinguishable from those obtained via an exact, enumerative method. A coarse-scale zoning of Talampaya National Park (Argentina) rendered maps remarkably similar to those produced by subject area experts using a non-quantitative consensus-seeking approach. Results are encouraging and show particular potential for the periodical update of zoning of protected natural areas. Such a capability is crucial for application in developing countries where both human and financial resources are usually scarce but still critical for updating zoning and management plans. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Preface: artificial intelligence in operations management

Annals of Operations Research -     

Determination of nutrients and potentially toxic elements in Jatropha curcas seeds, oil and biodiesel using inductively coupled plasma mass spectrometry

Biodiesel is a renewable and biodegradable fuel that can be used in diesel engines as a replacement for fossil diesel. A suitable alternative is to produce it from Jatropha curcas, which has high quality oil concentration. Nevertheless, the presence of particular chemical elements above certain limits can affect the product quality, leading to vehicle engine problems and acting as air pollution source. The objective of this work is to develop a method for the simultaneous determination of B, Na, Mg, P, S, K, Ca, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Ba, and Pb in J. curcas seeds, oil and biodiesel using the inductively coupled plasma mass spectrometry (ICP-MS) technique. This material was evaluated because has been successfully employed in India for biodiesel production as well as in other places where there is an incentive to family farming, without affect the food chain. The oil was obtained from seeds via mechanical extraction and the biodiesel was achieved by oil transesterification. After optimization of the microwave digestion method for the different sample types, the samples were analyzed by ICP-MS. The certified reference material NIST SRM 1515 (apple leaves) and the recovery tests were carried out to ensure the accuracy of the proposed method, which made possible the quantification of several nutrients and potentially toxic elements in J. curcas seeds, oil and biodiesel, especially Na, K, Ca, Mg, P and S in biodiesel which are mandatory analyzed by Petroleum, Natural Gas and Biofuel National Agency (ANP). This work highlights the findings of the first study of potentially toxic and nutrient elements in the production chain steps seed–oil–biodiesel from J. curcas.