Synthesis and Characterization of bis[(2-ethyl-5-methyl-imidazo-4-yl)methyl]Sulfide and Its Coordination Behavior toward Cu(II) as a Possible Approach of a Copper Site Type I

The synthesis and characterization of a novel ligand, bis[(2-ethyl-5-methyl-imidazo-4-yl)methyl]sulfide (bemims), as well as a bemims-containing copper(II) coordination complex are described. In this complex, [Cu(bemims)X2] with X = NO3−, bemims acts as a tridentate ligand and two monodentate nitrate ions complete the coordination sphere. Both imidazole N atoms and the thioether S atom of bemims participate in coordination. The Cu(II) ion is five-coordinated with a slightly distorted square-pyramidal geometry (τ = .09). Electrochemical studies and spectroscopic data for this complex are compared with some blue copper proteins in order to assess its ability to mimic the copper center of type I copper proteins

Unbiased Global Optimization of Lennard-Jones Clusters for N <= 201 by Conformational Space Annealing Method

We apply the conformational space annealing (CSA) method to the Lennard-Jones clusters and find all known lowest energy configurations up to 201 atoms, without using extra information of the problem such as the structures of the known global energy minima. In addition, the robustness of the algorithm with respect to the randomness of initial conditions of the problem is demonstrated by ten successful independent runs up to 183 atoms. Our results indicate that the CSA method is a general and yet efficient global optimization algorithm applicable to many systems.Comment: revtex, 4 pages, 2 figures. Physical Review Letters, in pres

New Tetrahedral Global Minimum for the 98-atom Lennard-Jones Cluster

A new atomic cluster structure corresponding to the global minimum of the 98-atom Lennard-Jones cluster has been found using a variant of the basin-hopping global optimization algorithm. The new structure has an unusual tetrahedral symmetry with an energy of -543.665361, which is 0.022404 lower than the previous putative global minimum. The new LJ_98 structure is of particular interest because its tetrahedral symmetry establishes it as one of only three types of exceptions to the general pattern of icosahedral structural motifs for optimal LJ microclusters. Similar to the other exceptions the global minimum is difficult to find because it is at the bottom of a narrow funnel which only becomes thermodynamically most stable at low temperature.Comment: 3 pages, 2 figures, revte

[16] Sostenibilización curricular en las universidades españolas. ¿ha llegado la hora de actuar?

Desde la Educación Superior se contempla la necesidad de incluir contenidos ambientales (económicos-sociales-naturales) en los curricula de las diferentes titulaciones para formar profesionales capaces de actuar críticamente en pos de la sostenibilidad. La CRUE viene trabajando en este sentido desde 2002, en 2005 aprobó unas directrices para la sostenibilización curricular en las universidades españolas. En la actualidad, desde la Comisión Sectorial para la Calidad Ambiental el Desarrollo Sostenible y la Prevención de Riesgos (CADEP) de la CRUE, se han detectado dificultades para su implantación y se trabaja en el estudio de estrategias para su mejor aplicación.Palabras clave: sostenibilización curricular; desarrollo sostenible; educación superior; educación ambiental; formación para la sostenibilidad.Sustainability in the curricula of Spanish universities. Has the time of acting come?From the sector of Higher Education the inclusion of environmental (economic-socialnatural) contents in the curricula in the different degrees is getting more attention, in order to educate critical professionals who are capable of acting towards sustainability. The CRUE has been working in this sense since 2002, having approved in 2005 the “guidelines” for embedding sustainability in the curricula of Spanish universities. Currently, the work carried from the Comisión Sectorial para la Calidad Ambiental el Desarrollo Sostenible y la Prevención de Riesgos (CADEP) of CRUE aims to overcome difficulties and barriers and study strategies for their introduction.Keywords: sustainability in the curriculum; sustainable development; higher education; environmental education; education for sustainability

The point spread function of electrons in a magnetic field, and the decay of the free neutron

Experiments in nuclear and particle physics often use magnetic fields to guide charged reaction products to a detector. Due to their gyration in the guide field, the particles hit the detector within an area that can be considerably larger than the diameter of the source where the particles are produced. This blurring of the image of the particle source on the detector surface is described by a suitable point spread function (PSF), which is defined as the image of a point source. We derive simple analytical expressions for such magnetic PSFs, valid for any angular distribution of the emitted particles that can be developed in Legendre polynomials. We investigate this rather general problem in the context of neutron beta decay spectrometers and study the effect of limited detector size on measured neutron decay correlation parameters. To our surprise, insufficient detector size does not affect much the accuracy of such measurements, even for rather large radii of gyration. This finding can considerably simplify the layout of the respective spectrometers.Comment: 24 pages, 12 figure

New measurement of the scattering cross section of slow neutrons on liquid parahydrogen from neutron transmission

Liquid hydrogen is a dense Bose fluid whose equilibrium properties are both calculable from first principles using various theoretical approaches and of interest for the understanding of a wide range of questions in many body physics. Unfortunately, the pair correlation function $g(r)$ inferred from neutron scattering measurements of the differential cross section $d\sigma \over d\Omega$ from different measurements reported in the literature are inconsistent. We have measured the energy dependence of the total cross section and the scattering cross section for slow neutrons with energies between 0.43~meV and 16.1~meV on liquid hydrogen at 15.6~K (which is dominated by the parahydrogen component) using neutron transmission measurements on the hydrogen target of the NPDGamma collaboration at the Spallation Neutron Source at Oak Ridge National Laboratory. The relationship between the neutron transmission measurement we perform and the total cross section is unambiguous, and the energy range accesses length scales where the pair correlation function is rapidly varying. At 1~meV our measurement is a factor of 3 below the data from previous work. We present evidence that these previous measurements of the hydrogen cross section, which assumed that the equilibrium value for the ratio of orthohydrogen and parahydrogen has been reached in the target liquid, were in fact contaminated with an extra non-equilibrium component of orthohydrogen. Liquid parahydrogen is also a widely-used neutron moderator medium, and an accurate knowledge of its slow neutron cross section is essential for the design and optimization of intense slow neutron sources. We describe our measurements and compare them with previous work.Comment: Edited for submission to Physical Review

Neutron Beta Decay Studies with Nab

Precision measurements in neutron beta decay serve to determine the coupling constants of beta decay and allow for several stringent tests of the standard model. This paper discusses the design and the expected performance of the Nab spectrometer.Comment: Submitted to Proceedings of the Conference CIPANP12, St.Petersburg, Florida, May 201

Invarianza factorial del Cuestionario de Autoconcepto Físico Modificado (CAF-M) en universitarios mexicanos deportistas y no deportistas

El objetivo principal del presente estudio fue examinar la invarianza factorial del Cuestionario de Autoconcepto Físico Modicado (CAF- M) en universitarios mexicanos deportistas y no deportistas. La muestra total fue de 1.528 universitarios mexicanos, 651 deportistas y 877 no deportistas, con una edad media de 20,78 años (DE = 2,45). Los análisis factoriales conrmatorios mostraron que una estructura de dos factores es viable y adecuada para ambas poblaciones. Atendiendo a criterios estadísticos y sustantivos, la estructura de dos factores (competencia motora y atractivo físico) ha mostrado adecuados indicadores de ajuste de abilidad y validez. Además, la estructura factorial, las cargas factoriales y los interceptos se consideran invariantes en las dos poblaciones estudiadas. Se encontraron diferencias entre los universitarios deportistas y no deportistas para las medias de ambos factores. Por último, el presente estudio también conrma la validez del modelo bidimensional del autoconcepto físico. Futuras investigaciones deberían replicar estos hallazgos en poblaciones con diferentes factores culturales y personales.