Publications by authors named "Seco J"

Eight new complexes containing the versatile multidentate ligand 5-pyrimidyl-tetrazolate (pmtz), namely [Cu(mu(3)-pmtz)](n) (1), [Pd(2)(mu-pmtz)(2)Cl(2)] (2), [Ni(pmtz)(en)(2)]Cl x 2 H(2)O (3), [Cu(tren)(pmtz)(ClO(4))] (4), [Co(2)(tren)(2)(mu-pmtz)(mu-O(2))](ClO(4))(3) x 3 H(2)O (5), [Fe(2)(pmtz)(4)(H(2)O)(2)(mu-O)] x 5 H(2)O (6), [(UO(2))(4)(mu-pmtz)(2)(mu-OH)(2)(mu(3)-O)(2)(H(2)O)(4)] x 6 H(2)O (7) and [Dy(2)(pmtz)(4)(mu-pmtz)(H(2)O)(6)](pmtz) x 6 H(2)O (8), have been prepared by either conventional solution or hydrothermal techniques and characterised by single-crystal X-ray diffraction. Those compounds prepared under hydrothermal conditions ((1), (2), (7) and (8)) exhibit chelating/bridging coordination modes that connect two or three metal ions generating polynuclear species. Thus, compound is a 2D polymer where the ligand exhibits a new chelating/bridging kappa(2)N(1),N(7):kappaN(2):kappaN(3) coordination mode, whereas complexes (2) and (7) are dinuclear and tetranuclear species, respectively, in which the ligand displays a kappa(2)N(1),N(7):kappaN(2) coordination mode.

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Treatment delivery with active beam scanning in proton radiation therapy introduces the problem of interplay effects when pencil beam motion occurs on a similar time scale as intra-fractional tumor motion. In situations where fractionation may not provide enough repetition to blur the effects of interplay, repeated delivery or 'repainting' of each field several times within a fraction has been suggested. The purpose of this work was to investigate the effectiveness of different repainting strategies in proton beam scanning.

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All radiation therapy treatment planning relies on accurate dose calculation. Uncertainties in dosimetric prediction can significantly degrade an otherwise optimal plan. In this work, we introduce a robust optimization method which handles dosimetric errors and warrants for high-quality IMRT plans.

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In drug discovery, it is essential to identify binding sites on protein surfaces that drug-like molecules could exploit to exert a biological effect. Both X-ray crystallography and NMR experiments have demonstrated that organic solvents bind precisely at these locations. We show that this effect is reproduced using molecular dynamics with a binary solvent.

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The absolute configuration of ketone cyanohydrins can be assigned from analysis of the 1H NMR spectra of the corresponding (R)- and (S)-MPA ester derivatives and use of delta delta(RS) signs. This is an application of the NMR methodology for stereochemical assignment to tertiary alcohols possessing polar groups as substituents.

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We have designed a simulation framework for motion studies in radiation therapy by integrating the anthropomorphic NCAT phantom into a 4D Monte Carlo dose calculation engine based on DPM. Representing an artifact-free environment, the system can be used to identify class solutions as a function of geometric and dosimetric parameters. A pilot dynamic conformal study for three lesions ( approximately 2.

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Experimental and Monte Carlo simulations were conducted for an Elekta Ltd Precise Treatment System linac fitted with a low Z insert of sufficient thickness to remove all primary electrons. A variety of amorphous silicon based panels employing different scintillators were modelled to determine their response to a variety of x-ray spectra and produce an optimized portal imaging system. This study has shown that in a low Z configuration the vast majority of x-rays are produced in the nickel electron window, and with a combination of a carbon insert and caesium iodide based XVI-panel, significant improvement in the object contrast was achieved.

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We tested whether growth and maintenance costs of plant organs vary with environmental stress. Quercus ilex L. seedlings from acorns collected from natural populations in the northern Iberian Peninsula and in a lower elevation and putatively less stressful habitat in the southern Iberian Peninsula were grown in pots under the same conditions.

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A general methodology for assigning the configuration of chiral mono- and polyfunctional compounds by NMR is presented. The approach is based on the use of polystyrene-bound chiral derivatizing agents (CDA-resins) specifically designed to achieve the high-yield formation of the covalent linkages (amide or ester bonds) between the substrate and the chiral auxiliary within the NMR tube, without the need for other manipulations, on a microscale level and in a short time. The deuterated NMR solvents (CDCl3, CD3CN, CS2/CD2Cl2) are also the reaction solvents and separations, purifications or workups of any kind are not necessary prior to recording the spectra.

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The chirality of sec/prim- and prim/sec-1,2-amino alcohols can be determined by (1)H NMR of just one MPA derivative--either (R) or (S)--by comparison of two spectra at different temperatures and analysis of the evolution of the easily observable singles of the CalphaH signals.

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The absolute configuration of sec/prim- and prim/sec-1,2-amino alcohols is determined by comparison of the (1)H NMR chemical shifts of the auxiliary OMe or CalphaH groups at the corresponding bis-( R) and bis-( S)-MPA derivatives. This is the first NMR method that allows the assignment of absolute configuration without resorting to the shifts of hydrogens at the substrate and is based on the cross anisotropic interactions between auxiliaries.

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Background: The NDI, COM and NPQ are evaluation instruments for disability due to NP. There was no Spanish version of NDI or COM for which psychometric characteristics were known. The objectives of this study were to translate and culturally adapt the Spanish version of the Neck Disability Index Questionnaire (NDI), and the Core Outcome Measure (COM), to validate its use in Spanish speaking patients with non-specific neck pain (NP), and to compare their psychometric characteristics with those of the Spanish version of the Northwick Pain Questionnaire (NPQ).

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The purpose of this study was to investigate if interfraction and intrafraction motion in free-breathing and gated lung IMRT can lead to systematic dose differences between 3DCT and 4DCT. Dosimetric effects were studied considering the breathing pattern of three patients monitored during the course of their treatment and an in-house developed 4D Monte Carlo framework. Imaging data were taken in free-breathing and in cine mode for both 3D and 4D acquisition.

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A general NMR spectroscopy protocol for determination of absolute configuration of thiols, that includes the introduction of new aryl-tert-butoxyacetic acids as chiral derivatizing agents (CDAs), is described.

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For EPID dosimetry, the calibration should ensure that all pixels have a similar response to a given irradiation. A calibration method (MC), using an analytical fit of a Monte Carlo simulated flood field EPID image to correct for the flood field image pixel intensity shape, was proposed. It was compared with the standard flood field calibration (FF), with the use of a water slab placed in the beam to flatten the flood field (WS) and with a multiple field calibration where the EPID was irradiated with a fixed 10x10 field for 16 different positions (MF).

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Knowledge of the accuracy of dose calculations in intensity-modulated radiotherapy of the head and neck is essential for clinical confidence in these highly conformal treatments. High dose gradients are frequently placed very close to critical structures, such as the spinal cord, and good coverage of complex shaped nodal target volumes is important for long term-local control. A phantom study is presented comparing the performance of standard clinical pencil-beam and collapsed-cone dose algorithms to Monte Carlo calculation and three-dimensional gel dosimetry measurement.

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The Monte Carlo method provides the most accurate dose calculations on a patient computed tomography (CT) geometry. The increase in accuracy is, at least in part, due to the fact that instead of treating human tissues as water of various densities as in analytical algorithms, the Monte Carlo method allows human tissues to be characterized by elemental composition and mass density, and hence allows the accurate consideration of all relevant electromagnetic and nuclear interactions. On the other hand, the algorithm to convert CT Hounsfield numbers to tissue materials for Monte Carlo dose calculation introduces uncertainties.

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Interplay between organ (breathing) motion and leaf motion has been shown in the literature to have a small dosimetric impact for clinical conditions (over a 30 fraction treatment). However, previous studies did not consider the case of treatment beams made up of many few-monitor-unit (MU) segments, where the segment delivery time (1-2 s) is of the order of the breathing period (3-5 s). In this study we assess if breathing compromises the radiotherapy treatment with IMRT segments of low number of MUs.

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The absolute configuration of beta-chiral primary alcohols devoid of observable hydrogens on one of the beta-substituents at the asymmetric carbon (L(1)/L(2)) can be determined by comparison of the (1)H NMR of their (R)- and (S)-9-AMA ester derivatives and analysis of the Deltadelta(RS) for the L substituent and the Cbeta-H.

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Comparison of the room- and low-temperature 1H NMR spectra of the bis-(R)- or bis-(S)-MPA ester derivative of an open chain sec,sec-1,2-diol allows the easy determination of its relative stereochemistry and in some cases absolute configuration. If the diol is anti, its absolute configuration can be directly deduced from the signs of DeltadeltaT1T2 for substituents R1/R2, but if the relative stereochemistry of the diol is syn, the assignment of its absolute configuration requires the preparation of two derivatives (both the bis-(R)- and bis-(S)-MPA esters), comparison of their room-temperature 1H NMR spectra, and calculation of the DeltadeltaRS signs for the methines Halpha(R1) and Halpha(R2) and R1/R2 protons. The reliability of these correlations is validated with 17 diols of known absolute configuration used as model compounds.

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Shaping electron fields through the use of lead cut-outs may result in there being acute angles in part of the field. Using both experimental techniques and EGSnrc Monte Carlo simulations an investigation was carried out to determine the dosimetric consequences of this. Measurements were made to investigate how the field dose was related to the angle between adjacent sides in the cut-outs.

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This study focused on predicting the electronic portal imaging device (EPID) image of intensity modulated radiation treatment (IMRT) fields in the absence of attenuation material in the beam with Monte Carlo methods. As IMRT treatments consist of a series of segments of various sizes that are not always delivered on the central axis, large spectral variations may be observed between the segments. The effect of these spectral variations on the EPID response was studied with fields of various sizes and off-axis positions.

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The conversion of computed tomography (CT) numbers into material composition and mass density data influences the accuracy of patient dose calculations in Monte Carlo treatment planning (MCTP). The aim of our work was to develop a CT conversion scheme by performing a stoichiometric CT calibration. Fourteen dosimetrically equivalent tissue subsets (bins), of which ten bone bins, were created.

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In intensity modulated radiation treatments (IMRT), the position of the field edges and the modulation within the beam are often achieved with a multileaf collimator (MLC). During the MLC calibration process, due to the finite accuracy of leaf position measurements, a systematic error may be introduced to leaf positions. Thereafter leaf positions of the MLC depend on the systematic error introduced on each leaf during MLC calibration and on the accuracy of the leaf position control system (random errors).

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