949 research outputs found

    An Unsaturated Four-Coordinate Dimethyl Dimolybdenum Complex with a Molybdenum–Molybdenum Quadruple Bond

    Get PDF
    We describe the synthesis and the molecular and electronic structures of the complex [Mo2Me2{μ‐HC(NDipp)2}2] (2; Dipp=2,6‐iPr2C6H3), which contains a dimetallic core with an Mo–Mo quadruple bond and features uncommon four‐coordinate geometry and has a fourteen‐electron count for each molybdenum atom. The coordination polyhedron approaches a square pyramid, with one of the molybdenum atoms nearly co‐planar with the basal square plane, in which the trans coordination position with respect to the Mo−Me bond is vacant. The other three sites are occupied by two trans nitrogen atoms of different amidinate ligands and the methyl group. The second Mo atom occupies the apex of the pyramid and forms an Mo–Mo bond of length 2.080(1) Å, consistent with a quadruple bond. Compound 2 reacts with tetrahydrofuran (THF) and trimethylphosphine to yield the mono‐adducts [Mo2Me(μ‐Me){μ‐HC(NDipp)2}2(L)] (3⋅THF and 3⋅PMe3, respectively) with one terminal and one bridging methyl group. In contrast, 4‐dimethylaminopyridine (dmap) forms the bis‐adduct [Mo2Me2{μ‐HC(NDipp)2}2(dmap)2] (4), with terminally coordinated methyl groups. Hydrogenolysis of complex 2 leads to the bis(hydride) [Mo2H2{μ‐HC(NDipp)2}2(thf)2] (5⋅THF) with elimination of CH4. Computational, kinetic, and mechanistic studies, which included the use of D2 and of complex 2 labelled with 13C (99 %) at the Mo–CH3 sites, supported the intermediacy of a methyl‐hydride reactive species. A computational DFT analysis of the terminal and bridging coordination of the methyl groups to the Mo≣Mo core is also reported.Ministerio de Ciencia e Innovación CTQ2010-15833, CTQ2013-42501-P, CTQ2014-52769-C3-3-R, CTQ2015-64579-C3-1-P, Consolider-Ingenio 2010 CSD2007-00006Junta de Andalucía FQM-119, P09-FQM-5117Ministerio de Educación AP-4193Ministerio de Ciencia e Innovación BES-2011-04764

    Morphometric Comparison of Blue Catfish Ictalurus furcatus (Lesueur, 1840) from Northern and Southern Atlantic Drainages of Me´xico

    Get PDF
    A morphometric comparison was performed on specimens of blue catfish (Ictalurus furcatus) from northern (Lower Rı´o Bravo) and southern (Chiapas) Me´xico in order to identify diagnostic characters that allow their discrimination. The discriminant function analysis determined three characters to be highly diagnostic to separate the two groups of specimens: the southern group [SG] has a shorter anal base (mean 5 3.4 times in standard length [SL], range 5 3.1 to 3.7) vs northern group [NG] (mean 5 2.9 times in SL, range 5 2.7 to 3.1), a lesser head width (mean 5 6.0 times in SL, range 5.1 to 6.8) vs NG (mean 5 5.6 times, range 5 5.3 to 6.0), and a lower number of anal rays (mean 5 26, range 5 24 to 28) vs NG (mean 5 31, range 5 29 to 34). Additionally, 14 other characters were also different (P , 0.01) between both groups. All these characters support the taxonomic validation of Ictalurus meridionalis (Gu¨ nther 1864) for the individuals of SG that are currently included in I. furcatus Lesueur. Studies on comparative osteology and molecular genetics of both forms are needed for the clarification of their taxonomic status

    Decision Tree Classifiers for Star/Galaxy Separation

    Full text link
    We study the star/galaxy classification efficiency of 13 different decision tree algorithms applied to photometric objects in the Sloan Digital Sky Survey Data Release Seven (SDSS DR7). Each algorithm is defined by a set of parameters which, when varied, produce different final classification trees. We extensively explore the parameter space of each algorithm, using the set of 884,126884,126 SDSS objects with spectroscopic data as the training set. The efficiency of star-galaxy separation is measured using the completeness function. We find that the Functional Tree algorithm (FT) yields the best results as measured by the mean completeness in two magnitude intervals: 14r2114\le r\le21 (85.285.2%) and r19r\ge19 (82.182.1%). We compare the performance of the tree generated with the optimal FT configuration to the classifications provided by the SDSS parametric classifier, 2DPHOT and Ball et al. (2006). We find that our FT classifier is comparable or better in completeness over the full magnitude range 15r2115\le r\le21, with much lower contamination than all but the Ball et al. classifier. At the faintest magnitudes (r>19r>19), our classifier is the only one able to maintain high completeness (>>80%) while still achieving low contamination (2.5\sim2.5%). Finally, we apply our FT classifier to separate stars from galaxies in the full set of 69,545,32669,545,326 SDSS photometric objects in the magnitude range 14r2114\le r\le21.Comment: Submitted to A

    Hidrogeles multicomponentes basados en vinilpirrolidona y su aplicación en ingeniería de tejidos y/o medicina regenerativa

    Get PDF
    Hidrogel con estructura de red polimérica multicomponente entrecruzada, caracterizado porque comprende: a) unidades derivadas de vinilpirrolidona (V) y unidades derivadas de un monómero alquénico aniónico o anionizable (A), donde las relaciones de reactividad en copolimerización radical binaria de (V) y (A) tienen valores máximo y mínimo de 0.5 respectivamente; y b) unidades derivadas de al menos un entrecruzante; siempre que el o los entrecruzantes sean i) dos entrecruzantes E1 y E2, donde E1 presenta homología al menos parcial respecto a (A) y E2 presenta homología al menos parcial respecto a (V); o ii) un entrecruzante E3 que presenta homología respecto a (A) y (V). Procedimiento de obtención del mencionado hidrogel que comprende poner en contacto los monómeros (A) y (V) con los entrecruzantes E1 y E2, o el entrecruzante E3, en condiciones de polimerización radicalaria. Uso del hidrogel en aplicaciones biológicas, biomédicas o biotecnológicas que requieran una interacción no tóxica hidrogel-célula.Peer reviewedConsejo Superior de investigaciones Científicas, Universidad Complutense de MadridB1 Patente sin examen previ

    Ianus: an Adpative FPGA Computer

    Full text link
    Dedicated machines designed for specific computational algorithms can outperform conventional computers by several orders of magnitude. In this note we describe {\it Ianus}, a new generation FPGA based machine and its basic features: hardware integration and wide reprogrammability. Our goal is to build a machine that can fully exploit the performance potential of new generation FPGA devices. We also plan a software platform which simplifies its programming, in order to extend its intended range of application to a wide class of interesting and computationally demanding problems. The decision to develop a dedicated processor is a complex one, involving careful assessment of its performance lead, during its expected lifetime, over traditional computers, taking into account their performance increase, as predicted by Moore's law. We discuss this point in detail

    Renormalization Group Analysis of Boundary Conditions in Potential Scattering

    Full text link
    We analyze how a short distance boundary condition for the Schrodinger equation must change as a function of the boundary radius by imposing the physical requirement of phase shift independence on the boundary condition. The resulting equation can be interpreted as a variable phase equation of a complementary boundary value problem. We discuss the corresponding infrared fixed points and the perturbative expansion around them generating a short distance modified effective range theory. We also discuss ultraviolet fixed points, limit cycles and attractors with a given fractality which take place for singular attractive potentials at the origin. The scaling behaviour of scattering observables can analytically be determined and is studied with some emphasis on the low energy nucleon-nucleon interaction via singular pion exchange potentials. The generalization to coupled channels is also studied.Comment: 31 pages, 8 figure

    Surgical management of enchondroma with joint transfer: a case report

    Get PDF
    The enchondromas are the most common benign bone tumor in the hands, mainly in young patients and its treatment is surgical in most cases due to its possible complications avoided through different procedures such as joint transfer, which allows to maintain a good quality of life for the patient. We present the case of a 42-year-old woman who came to the clinic for blunt trauma in the right hand where she was incidentally diagnosed with enchondroma on the third finger of the proximal interphalangeal joint of the right hand. Articular transfer of the proximal interphalangeal joint was performed. Second toe on the right, at 6 weeks corroborates correct evolution with bone consolidation of the articular transfer grade III and donor zone grade II, without infection complications, the correct recovery of the extensor movement range of this joint improving so their state of life should be the main objective of these procedures

    Prepubertal Children With Metabolically Healthy Obesity or Overweight Are More Active Than Their Metabolically Unhealthy Peers Irrespective of Weight Status: GENOBOX Study

    Get PDF
    Background and Aim: The association of a metabolically healthy status with the practice of physical activity (PA) remains unclear. Sedentarism and low PA have been linked to increased cardiometabolic risk. The aim of this study was to evaluate the PA levels in metabolically healthy (MH) or unhealthy (MU) prepubertal children with or without overweight/obesity. Methods: A total 275 children (144 boys) with 9 ± 2 years old were selected for the GENOBOX study. PA times and intensities were evaluated by accelerometry, and anthropometry, blood pressure, and blood biochemical markers were analyzed. Children were considered to have normal weight or obesity, and further classified as MH or MU upon fulfillment of the considered metabolic criteria. Results: Classification resulted in 119 MH children (21% with overweight/obesity, referred to as MHO) and 156 MU children (47% with overweight/obesity, referred to as MUO). Regarding metabolic profile, MHO showed lower blood pressure levels, both systolic and diastolic and biochemical markers levels, such as glucose, Homeostatic Model Assessment of Insulin Resistance, triglycerides and higher HDL-c levels than MUO (P < 0.001). In addition, MHO children spent more time in PA of moderate intensity compared with MUO children. In relation to vigorous PA, MH normal weight (MHN) children showed higher levels than MUO children. Considering sex, boys spent more time engaged in moderate, vigorous, and moderate–vigorous (MV) PA than girls, and the number of boys in the MH group was also higher. Conclusion: Prepubertal MHO children are less sedentary, more active, and have better metabolic profiles than their MUO peers. However, all children, especially girls, should increase their PA engagement, both in terms of time and intensity because PA appears to be beneficial for metabolic health status itself. Copyright © 2022 Llorente-Cantarero, Leis, Rupérez, Anguita-Ruiz, Vázquez-Cobela, Flores-Rojas, González-Gil, Aguilera, Moreno, Gil-Campos and Bueno

    Quality indicators in radiation oncology: proposal of the Spanish Society of Radiation Oncology (SEOR) for a continuous improvement of the quality of care in oncology.

    Get PDF
    Purpose Current cancer treatment options include surgical intervention, radiotherapy, and chemotherapy. The quality of the provision of each of them and their effective coordination determines the results in terms of benefit/risk. Regarding the radiation oncology treatments, there are not stabilised quality indicators to be used to perform control and continuous improvement processes for healthcare services. Therefore, the Spanish Society of Radiation Oncology has undertaken a comprehensive project to establish quality indicators for use with the information systems available in most Spanish healthcare services. Methods A two-round Delphi study examines consensus of several possible quality indicators (n = 28) in daily practice. These indicators were defined after a bibliographic search and the assessment by radiation oncology specialists (n = 8). They included aspects regarding treatment equipment, patient preparation, treatment, and follow-up processes and were divided in structure, process, and outcome indicators. Results After the evaluation of the defined quality indicators (n = 28) by an expert panel (38 radiation oncologist), 26 indicators achieved consensus in terms of agreement with the statement. Two quality indicators did not achieve consensus. Conclusions There is a high degree of consensus in Spanish Radiation Oncology specialists on which indicators in routine clinical practice can best measure quality. These indicators can be used to classify services based on several parameters (patients, equipments, complexity of the techniques used, and scientific research). Furthermore, these indicators allow assess our current situation and set improvements’ objectives.pre-print241 K
    corecore