A genetic algorithm with neural network fitness function evaluation for IMRT beam angle optimization

Intensity Modulated Radiotherapy Treatment (IMRT) is a technique used in the treatment of cancer, where the radiation beams are modulated by a multileaf collimator allowing the irradiation of the patient using non-uniform radiation fields from selected angles. Beam angle optimization consists in trying to find the best set of angles that should be used in IMRT planning. The choice of this set of angles is patient and pathology dependent and, in clinical practice, most of the times it is made using a trial and error procedure or simply using equidistantly distributed angles. In this paper we propose a genetic algorithm that aims at calculating good sets of angles in an automated way, given a predetermined number of angles. We consider the discretization of all possible angles in the interval [0 \(^{\circ }\) , 360 \(^{\circ }\) ], and each individual is represented by a chromosome with 360 binary genes. As the calculation of a given individual’s fitness is very expensive in terms of computational time, the genetic algorithm uses a neural network as a surrogate model to calculate the fitness of most of the individuals in the population. To explicitly consider the estimation error that can result from the use of this surrogate model, the fitness of each individual is represented by an interval of values and not by a single crisp value. The genetic algorithm is capable of finding improved solutions, when compared to the usual equidistant solution applied in clinical practice. The genetic algorithm will be described and computational results will be shown.     

Finite-time blowup for a complex Ginzburg–Landau equation with linear driving

In this paper, we consider the complex Ginzburg–Landau equation ${u_t = e^{i\theta} [\Delta u + |u|^\alpha u] + \gamma u}$ on ${\mathbb{R}^N}$ , where ${\alpha > 0,\,\gamma \in \mathbb{R}}$ and ${-\pi /2 < \theta < \pi /2}$ . By convexity arguments, we prove that, under certain conditions on ${\alpha,\theta,\gamma}$ , a class of solutions with negative initial energy blows up in finite time.     

The Lattice of Synchrony Subspaces of a Coupled Cell Network: Characterization and Computation Algorithm

Coupled cell systems are networks of dynamical systems (the cells), where the links between the cells are described through the network structure, the coupled cell network. Synchrony subspaces are spaces defined in terms of equalities of certain cell coordinates that are flow-invariant for all coupled cell systems associated with a given network structure. The intersection of synchrony subspaces of a network is also a synchrony subspace of the network. It follows, then, that, given a coupled cell network, its set of synchrony subspaces, taking the inclusion partial order relation, forms a lattice. In this paper we show how to obtain the lattice of synchrony subspaces for a general network and present an algorithm that generates that lattice. We prove that this problem is reduced to obtain the lattice of synchrony subspaces for regular networks. For a regular network we obtain the lattice of synchrony subspaces based on the eigenvalue structure of the network adjacency matrix.     

Direct patterning of polysilanes and polygermanes using interference lithography

The direct patterning of poly(p‐methoxyphenylmethylsilane) (PMPMS) and poly(p‐methoxyphenylmethylgermane) (PMPMG) by interference lithography is reported. Copyright © 2011 John Wiley & Sons, Ltd.     

Thermal analysis of hair treated with oxidative hair dye under influence of conditioners agents

This research aimed the effect on Caucasian hair tresses treated with oxidative hair dye, either incorporated or not with conditioners agents, analyzed by Differential Scanning Calorimetry (DSC) and Thermogravimetric analysis (TG). The formulations of hair dyes were emulsions oil-in-water with light blond color containing or not the conditioners agents: silanetriol and panthenol; PEG-12 dimethicone; hydrolyzed silk, hydrolyzed milk protein, and lactose. Each dye (1.5 g) was applied in the hair tress (2.0 g/20.0 cm of length of Caucasian light-brown), previously treated, more 1.5 g of hydrogen peroxide 20 vol during 40 min. Evaluation of mass loss of the different hair sample demonstrates that these chemical hair treatments impair the hair fibers, reduced their moisture content with respect to the untreated hair. The incorporation of conditioners agents (silanetriol and panthenol; PEG-12 dimethicone; hydrolyzed silk, hydrolyzed milk protein, and lactose) in oxidative hair dyes types did not decrease the damage caused on the tresses by the coloring process quantified by TG/DTG. However, the DSC curves demonstrated those conditioners agents (silanetriol and panthenol; PEG-12 dimethicone) dislocated the beginning of the third event in 20 °C and they inhibited the presence of the fourth event, having characterized thermal protection to the hair.     

The reactions of diaminomaleonitrile with isocyanates and either aldehydes or ketones revisited.

A reinvestigation of the reactions of urea derivatives of diaminomaleonitrile 2 with aldehydes or ketones in the presence of triethylamine has established that the products of these reactions are not pyrimidino[5,4-d]pyrimidines 9 as previously reported, but 8-oxo-6-carboxamido-1,2-dihydropurines 12, which are oxidized rapidly in air to the corresponding 6-carboxamidopurines 13. Similarly, the reaction of Schiff base derivatives of DAMN 5 with isocyanates in the presence of triethylamine gives the substituted 2-oxoimidazoles 20 and not the pyrimidine derivatives 8 as previously claimed. The compounds 20 cyclize in solution and are easily oxidized to 8-oxopurine-6-carbonitriles 22, which give the same 8-oxopurine-6-carboxamides 13 upon further hydrolysis.     

Ethylene and propylene polymerization with bis(indenyl)zirconium/Mao catalytic systems modified by sterically demanding alcohols

Ethylene and propylene polymerization using Ind₂ZrCl₂ and Ind₂Zr(CH₃)₂/MAO catalytic systems modified by the sterically demanding bridged alicyclic alcohols, adamantan‐1‐ol, adamantan‐2‐ol, 2‐methyladamantan‐2‐ol, and fenchyl alcohol, was investigated. Lower alcohols like isopropanol completely deactivate the system, whereas in the case of catalysts modified by these voluminous alcohols only a slight decrease in the catalytic activity proportional to alcohol/metallocene molar ratio was observed. The addition of the modifiers gives rise to polymers with higher molecular weights than the nonmodified systems, but no structural changes in the polyethylenes were observed. The addition of the sterically demanding alcohols to the reaction medium changes the regioregularity of polypropylenes, but does not significantly influence their stereoregularity, at 30 °C. Propylene–ethylene copolymers containing up to 8.6% of ethylene units derived from 1,3‐insertion and significant amount of rr‐centered pentads were obtained by single‐monomer polymerization of propylene with Ind₂ZrCl₂/MMAO/adamantan‐1‐ol, at 70 °C. © 2005 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 43: 4248–4259, 2005     

High-sensitivity methods for sequential injection determination of the main constituents of alloys

A sequential injection system with spectrophotometric detection was proposed for the determination of copper, zinc and lead in brass. In view of the high analyte concentrations and the sensitivity of the involved catalytic methods, optimization of the flow system was carried out aiming mild reaction conditions. Copper and lead determinations were based on the catalytic effects of Cu²⁺ and Pb²⁺ on the oxidation rates of resorcinol and pyrogallol red by H₂O₂, respectively, and zinc determination involved precipitate formation after oxidation of 1-nafthylethylenediamine by K₃Fe(CN)₆. The analytical procedures were designed with some common parameters such as pH=9.0 (borate system), λ=530 nm, and H₂O₂ as oxidizing agent; system geometry was maintained.The proposed system is rugged, and base line drift is not observed during 4 h operation periods. Twenty samples are run per hour (60 determinations) and reagent consumption is minimal, thus avoiding drawbacks related to waste management. Precise results (R.S.D.<1.0%; n=7) are obtained and a detection limit of 1% (w/w) was estimated for the three analytes. Results were in agreement with flame atomic absorption spectrometry.