Updated F(T) gravity constraints from high redshift cosmography

In the last dozen years a wide and variegated mass of observational data revealed that the universe is now expanding at an accelerated rate. In the absence of a well-based theory to interpret the observations, cosmography provides information about the evolution of the Universe from measured distances, only assuming that the geometry of the can be described by the Friedmann-Lemaitre-Robertson -Walker metric. We perform a high-redshift analysis allows us to put constraints on the cosmographic parameters up to the 5fth order, thus inducing indirect constraints on any gravity theory. Here we are interested in the so called teleparallel gravity theory, f(T). Actually we use the analytical expressions of the present day values of f(T) and its derivatives as functions of the cosmographic parameters to map the cosmography region of confidences into confidence ranges for f(T) and its derivative. Moreover, we show how these can be used to test some teleparallel gravity models without solving the dynamical equations. Our analysis is based on the Union2 Type Ia Supernovae (SNIa) data set, a set of 28 measurements of the Hubble parameter, the Hubble diagram constructed from some Gamma Ray Bursts (GRB) luminosity distance indicators, and gaussian priors on the distance from the Baryon Acoustic Oscillations (BAO), and the Hubble constant h. To perform our statistical analysis and to explore the probability distributions of the cosmographic parameters we use the Markov Chain Monte Carlo Method (MCMC).Comment: International Journal of Modern Physics D, 20 pages, 5 figure

Solid-liquid equilibria for the dimethyl ether plus carbon dioxide binary system

A recently built experimental setup was employed for the estimation of the solid-liquid equilibria of alternative refrigerants systems. The behavior of dimethyl ether (DME) + carbon dioxide was measured down to temperatures of 131.6 K. To confirm the reliability of the apparatus, the triple point of the DME was measured. The triple point data measured revealed a good consistency with the literature. The results obtained for the mixtures were corrected by the Rossini method and interpreted by means of the Schröder equation. © 2010 Akadémiai Kiadó, Budapest, Hungary

Carbon Dioxide + Fluoromethane and Nitrous Oxide + Fluoromethane: Solid−Liquid Equilibria Measurements

A recently built experimental setup was employed for the estimation of the solid-liquid equilibria (SLE) of alternative refrigerant systems. The behavior of two binaries, that is, carbon dioxide + fluoromethane (CO2 + R41) and nitrous oxide + fluoromethane (N2O + R41), was measured down to temperatures of 126.5 K. To confirm the reliability of the apparatus, the triple points of the pure fluids constituent of the binary systems were measured. All triple-point data measured revealed a generally good consistency with the literature. The results obtained for the mixtures were corrected by the Rossini method and interpreted by means of the Schröder equation. © 2010 American Chemical Society

Copper Nanoparticles in Click Chemistry

Conspectus: The challenges of the 21st century demand scientific and technological achievements that must be developed under sustainable and environmentally benign practices. In this vein, click chemistry and green chemistry walk hand in hand on a pathway of rigorous principles that help to safeguard the health of our planet against negligent and uncontrolled production. Copper-catalyzed azide–alkyne cycloaddition (CuAAC), the paradigm of a click reaction, is one of the most reliable and widespread synthetic transformations in organic chemistry, with multidisciplinary applications. Nanocatalysis is a green chemistry tool that can increase the inherent effectiveness of CuAAC because of the enhanced catalytic activity of nanostructured metals and their plausible reutilization capability as heterogeneous catalysts. This Account describes our contribution to click chemistry using unsupported and supported copper nanoparticles (CuNPs) as catalysts prepared by chemical reduction. Cu(0)NPs (3.0 ± 1.5 nm) in tetrahydrofuran were found to catalyze the reaction of terminal alkynes and organic azides in the presence of triethylamine at rates comparable to those achieved under microwave heating (10–30 min in most cases). Unfortunately, the CuNPs underwent dissolution under the reaction conditions and consequently could not be recovered. Compelling experimental evidence on the in situ generation of highly reactive copper(I) chloride and the participation of copper(I) acetylides was provided. The supported CuNPs were found to be more robust and efficient catalyst than the unsupported counterpart in the following terms: (a) the multicomponent variant of CuAAC could be applied; (b) the metal loading could be substantially decreased; (c) reactions could be conducted in neat water; and (d) the catalyst could be recovered easily and reutilized. In particular, the catalyst composed of oxidized CuNPs (Cu2O/CuO, 6.0 ± 2.0 nm) supported on carbon (CuNPs/C) was shown to be highly versatile and very effective in the multicomponent and regioselective synthesis of 1,4-disubstituted 1,2,3-triazoles in water from organic halides as azido precursors; magnetically recoverable CuNPs (3.0 ± 0.8 nm) supported on MagSilica could be alternatively used for the same purpose under similar conditions. Incorporation of an aromatic substituent at the 1-position of the triazole could be accomplished using the same CuNPs/C catalytic system starting from aryldiazonium salts or anilines as azido precursors. CuNPs/C in water also catalyzed the regioselective double-click synthesis of β-hydroxy-1,2,3-triazoles from epoxides. Furthermore, alkenes could be also used as azido precursors through a one-pot CuNPs/C-catalyzed azidosulfenylation–CuAAC sequential protocol, providing β-methylsulfanyl-1,2,3-triazoles in a stereo- and regioselective manner. In all types of reaction studied, CuNPs/C exhibited better behavior than some commercial copper catalysts with regard to the metal loading, reaction time, yield, and recyclability. Therefore, the results of this study also highlight the utility of nanosized copper in click chemistry compared with bulk copper sources.This work was supported by the Spanish Ministerio de Economía y Competitividad, the Generalitat Valenciana, Fondo Europeo de Desarrollo Regional, the Argentinian Consejo Nacional de Investigaciones Científicas y Técnicas and Agencia Nacional de Promoción Científica Tecnológica, and the Instituto de Síntesis Orgánica (Universidad de Alicante)

Quantifying Volume Changing Perturbations in a Wave Chaotic System

A sensor was developed to quantitatively measure perturbations which change the volume of a wave chaotic cavity while leaving its shape intact. The sensors work in the time domain by using either scattering fidelity of the transmitted signals or time reversal mirrors. The sensors were tested experimentally by inducing volume changing perturbations to a one cubic meter mixed chaotic and regular billiard system. Perturbations which caused a volume change that is as small as 54 parts in a million were quantitatively measured. These results were obtained by using electromagnetic waves with a wavelength of about 5cm, therefore, the sensor is sensitive to extreme sub-wavelength changes of the boundaries of a cavity. The experimental results were compared with Finite Difference Time Domain (FDTD) simulation results, and good agreement was found. Furthermore, the sensor was tested using a frequency domain approach on a numerical model of the star graph, which is a representative wave chaotic system. These results open up interesting applications such as: monitoring the spatial uniformity of the temperature of a homogeneous cavity during heating up / cooling down procedures, verifying the uniform displacement of a fluid inside a wave chaotic cavity by another fluid, etc.Comment: 13 pages, 13 figure

Trust and fertility in uncertain times

Recent studies have shown higher uncertainty to be associated with fertility decline. This study considers the role of social trust as a coping mechanism when general uncertainty increases. We analyse the fertility data of Italian provinces from 2004 to 2013, thereby incorporating the period of economic recession, which unexpectedly and exogenously increased uncertainty across the population. We find a robust and significantly positive impact of social trust on fertility, which is stronger among younger age groups. Moreover, we find that the buffer effect of trust decreases with the level of public childcare provision, suggesting that low trust endowments may be counterbalanced through public policy

Cross-Dehydrogenative Coupling of Tertiary Amines and Terminal Alkynes Catalyzed by Copper Nanoparticles on Zeolite

A wide range of catalysts based on supported copper nanoparticles have been prepared and tested in the cross-dehydrogenative coupling of tertiary amines and terminal alkynes. Copper nanoparticles on zeolite Y were found to be the most effective catalyst in the presence of tert-butyl hydroperoxide as the oxidant. Contrary to the previously reported methodologies involving copper catalysts, reactions have been accomplished without the need of an inert atmosphere and in the absence of solvent, using 1.5 mol% catalyst. A variety of tertiary amines, including aromatic, benzylic and aliphatic ones, have been coupled with both aromatic and aliphatic alkynes to furnish the corresponding propargylamines in moderate-to-excellent yields. The procedure has been successfully scaled-up to 12 mmol with a high conversion (93%). Moreover, the catalyst has been reused in seven cycles maintaining a good performance. Its catalytic activity has been compared with that of an array of commercial copper catalysts, being superior as regards the conversion and minimizing the alkyne homocoupling as a side reaction. The negative filtration test points to a heterogeneous nature of the process. Based on compelling experimental evidence, a novel reaction mechanism has been delineated which outlines the essential role of free radicals and the couple copper(I)/copper(II).This work was generously supported by the Spanish Ministerio de Economía y Competitividad (MINECO: CTQ2011-24151). Y. M. acknowledges the Instituto de Síntesis Orgánica (ISO) of the Universidad de Alicante for a grant