Integrating nonlinear branch-and-bound and outer approximation for convex Mixed Integer Nonlinear Programming

In this paper, we present a new hybrid algorithm for convex Mixed Integer Nonlinear Programming (MINLP). The proposed hybrid algorithm is an improved version of the classical nonlinear branch-and-bound (BB) procedure, where the enhancements are obtained with the application of the outer approximation algorithm on some nodes of the enumeration tree. The two methods are combined in such a way that each one collaborates to the convergence of the other. Computational experiments with benchmark instances of the MINLP problem show the good performance of the proposed algorithm, which is compared to the outer approximation algorithm, the nonlinear BB algorithm and the hybrid algorithm implemented in the solver Bonmin.     

Testing optimality for quadratic 0-1 problems

Received June 4, 1996 / Revised version received November 19, 1997 Published online November 24, 1998     

On complete graphs with negative r-mean curvature

We generalize Efimov's Theorem for graphs in Euclidean space using the scalar curvature, with an additional hypothesis on the second fundamental form.     

Luminescence quantum yield determination for molecules adsorbed onto solid powdered particles.

A new methodology for the determination of the fluorescence quantum yield of dyes adsorbed onto microcrystalline cellulose is presented and applied to rhodamine 101, cresyl violet and auramine O. It is based on a previously reported method by Ruetten and Thomas (J. Phys. Chem., 1998, 102, 598-606), which is not applicable to the dyes used in the present study. It uses ground-state diffuse reflectance spectra obtained with and without filters, which prevents the luminescence of the dye from reaching the integrating sphere and the photodetector. New equations are presented here, correcting for the fluorescence emission of the dye, which depends on the detector sensitivity. Cut-on filters, which have a transmittance close to unity in the absorption region, and close to zero in the emission region, of the dye are used to obtain corrected reflectance spectra. The influence of the substrate was also taken into account. This methodology may be applied to other probes and surfaces or emissions of a different nature (i.e., phosphorescence or delayed fluorescence), and constitutes a very simple and general procedure to solve the important problem of luminescence quantum yield determination of probes adsorbed onto solid powdered surfaces.     

On the Michelson-Morley experiment

A rigorous wave-theoretic approach to the Michelson-Morley (M-M) experiment is presented, with special emphasis on the Huygens' principle derivation of the laws of reflection by a moving mirror. A detailed discussion of the Lorentz-Fitzgerald contraction hypothesis (CH) is included. Several mistakes appearing in the standard textbook treatments of these issues are pointed out, and a number of related historical questions are considered.     

When every multilinear mapping is multiple summing

In this paper we give a systematized treatment to some coincidence situations for multiple summing multilinear mappings which extend, generalize and simplify the methods and results obtained thus far. The application of our general results to the pertinent particular cases gives several new coincidences as well as easier proofs of some known results (© 2009 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)     

Volatile components of vine leaves from two Portuguese grape varieties (Vitis vinifera L.), Touriga Nacional and Tinta Roriz,analysed by solid-phase microextraction

The purpose of this work was to study the volatile composition of vine leaves and vine leaf infusion prepared from vine leaves collected at 30 and 60 days after grape harvest of two Vitis vinifera L. species. Eighteen volatile compounds were identified by gas chromatography–mass spectrometry in vine leaves and in vine leaf infusions. It was observed that the volatile compounds present in vine leaves are dependent on the time of harvest, with benzaldehyde being the major volatile present in vine leaves collected at 30 days after harvesting. There are significant differences in the volatile composition of the leaves from the two grape cultivars, especially in the sample collected at 60 days after grape harvest. This is not reflected in the volatile composition of the vine leaf infusion made from this two cultivars, the more important being the harvesting date for the volatile profile of vine leaf infusion than the vine leaves grape cultivar.     

Effects of Ultraviolet Radiation (UVA+UVB) and Copper on the Morphology,Ultrastructural Organization and Physiological Responses of the Red Alga Pterocladiella capillacea

The effect of ultraviolet (UV) radiation and copper (Cu) on apical segments of Pterocladiella capillacea was examined under two different conditions of radiation, PAR (control) and PAR+UVA+UVB (PAR+UVAB), and three copper concentrations, ranging from 0 (control) to 0.62, 1.25 and 2.50 μm . Algae were exposed in vitro to photosynthetically active radiation (PAR) at 70 μmol photons m^?2 s^?1, PAR + UVB at 0.35 W m^?2 and PAR +UVA at 0.70 W m^?2 during a 12‐h photocycle for 3 h each day for 7 days. The effects of radiation and copper on growth rates, content of photosynthetic pigments and photosynthetic performance were analyzed. In addition, samples were processed for light and transmission electron microscopy. The content of photosynthetic pigments decreased after exposure to radiation and Cu. Compared with PAR radiation and copper treatments modified the kinetics patterns of the photosynthesis/irradiance curve. The treatments also caused changes in the ultrastructure of cortical and subcortical cells, including increased cell wall thickness and accumulation of plastoglobuli, as well as changes in the organization of chloroplasts. The results indicate that the synergistic interaction between UV radiation and Cu in P. capillacea, led to the failure of protective mechanisms and causing more drastic changes and cellular imbalances.     

Calibration transfer employing univariate correction and robust regression

This paper proposes a new method for calibration transfer, which was specifically designed to work with isolated variables, rather than the full spectrum or spectral windows. For this purpose, a univariate procedure is initially employed to correct the spectral measurements of the secondary instrument, given a set of transfer samples. A robust regression technique is then used to obtain a model with low sensitivity with respect to the univariate correction residuals. The proposed method is employed in two case studies involving near infrared spectrometric determination of specific mass, research octane number and naphthenes in gasoline, and moisture and oil in corn. In both cases, better calibration transfer results were obtained in comparison with piecewise direct standardization (PDS). The proposed method should be of a particular value for use with application-targeted instruments that monitor only a small set of spectral variables.     

Strong Direct Magnetic Coupling in a Dinuclear CoII Tetrazine Radical Single‐Molecule Magnet

The ligand‐centered radical complex [(CoTPMA)₂‐μ‐bmtz^.?](O₃SCF₃)₃ ? CH₃CN (bmtz=3,6‐bis(2′‐pyrimidyl)‐1,2,4,5‐tetrazine, TPMA=tris‐(2‐pyridylmethyl)amine) has been synthesized from the neutral bmtz precursor. Single‐crystal X‐ray diffraction studies have confirmed the presence of the ligand‐centered radical. The Co^II complex exhibits slow paramagnetic relaxation in an applied DC field with a barrier to spin reversal of 39 K. This behavior is a result of strong antiferromagnetic metal–radical coupling combined with positive axial and strong rhombic anisotropic contributions from the Co^II ions.