139 research outputs found
Constraining the astrophysics of the Cosmic Dawn and the Epoch of Reionization with the SKA
The Square Kilometre Array (SKA) will offer an unprecedented view onto the early Universe, using interferometric observations of the redshifted 21cm line. The 21cm line probes the thermal and ionization state of the cosmic gas, which is governed by the birth and evolution of the first structures in our Universe. Here we show how the evolution of the 21cm signal will allow us to study when the first generations of galaxies appeared, what were their properties, and what was the structure of the intergalactic medium. We highlight qualitative trends which will offer robust insights into the early Universe
Characterizing Olefin Selectivity and Stability of Silver Salts in Ionic Liquids Using Inverse Gas Chromatography
Separation systems utilizing silver(I) ion-olefin complexation have limitations since silver(I) ions can be poisoned or reduced to metallic silver. Ionic liquids (ILs) are used as solvents for silver(I) ions to facilitate separations since their physico-chemical properties can be easily tuned. To develop separation systems with sustainable olefin selectivity, factors that affect silver(I) ion stability need to be understood. In this study, a total of 13 silver salt/IL mixtures were examined by inverse gas chromatography to identify the effects of silver salt anion and IL cation/anion combination on silver(I) ion stability. The effects of temperature and three different exposure gases on silver(I) ion stability were systematically studied. Exposing silver salt/IL mixtures to hydrogen at high temperatures had a greater effect on decreasing silver(I) ion-olefin complexation. Silver(I) ions from the silver bis[(trifluoromethyl)sulfonyl]imide ([NTf2–]) salt were more stable in [NTf2–]-containing ILs than in [BF4–]-containing ILs. Optimum mixtures exhibited high olefin selectivity and were stable beyond 90 h when exposed to hydrogen gas
Local structure study of the orbital order/disorder transition in LaMnO3
We use a combination of neutron and X-ray total scattering measurements
together with pair distribution function (PDF) analysis to characterise the
variation in local structure across the orbital order--disorder transition in
LaMnO. Our experimental data are inconsistent with a conventional
order--disorder description of the transition, and reflect instead the
existence of a discontinuous change in local structure between ordered and
disordered states. Within the orbital-ordered regime, the neutron and X-ray
PDFs are best described by a local structure model with the same local orbital
arrangements as those observed in the average (long-range) crystal structure.
We show that a variety of meaningfully-different local orbital arrangement
models can give fits of comparable quality to the experimental PDFs collected
within the disordered regime; nevertheless, our data show a subtle but
consistent preference for the anisotropic Potts model proposed in \emph{Phys
Rev.\ B} {\bf 79}, 174106 (2009). The key implications of this model are
electronic and magnetic isotropy together with the loss of local inversion
symmetry at the Mn site. We conclude with a critical assessment of the
interpretation of PDF measurements when characterising local symmetry breaking
in functional materials.Comment: 14 pages, 8 figures, 3 table
Efficient synthesis of pyrene-1-carbothioamides and carboxamides. Tunable solid-state fluorescence of pyrene-1-carboxamides
Pyrene reacts with potassium thiocyanate and organic isothiocyanates in the presence of
trifluoromethanesulfonic acid to afford primary and secondary pyrene-1-carbothioamides in high yields.
These compounds were efficiently oxidatively desulfurized with Oxone® to the corresponding
carboxamides. The amides display solid-state fluorescence with quantum efficiencies up to 62%,
originating from monomers, aggregates (such as preformed dimers), and/or excimers, depending on the
substituent at the nitrogen atom. Single crystal X-ray diffraction characterization of one highly emissive
compound supports this assumption.Publikacja w ramach programu Royal Society of Chemistry "Gold for Gold" 2014 finansowanego przez Uniwersytet Łódzki
Evolution of Chagas’ disease in Brazil. Epidemiological perspective and challenges for the future: a critical review
Aims: This paper aimed to provide a critical review of the evolution of Chagas’ disease in Brazil, its magnitude, historical development and management, and challenges for the future.
Methods: A literature search was performed using PubMed, SciELO and Google Scholar and throughout collected articles’ references. Narrative analysis was structured around five main themes identified: vector transmission, control program, and transfusion, oral and congenital transmission.
Results: In Brazil, the Chagas’ disease Control Program was fully implemented in the 1980s, when it reached practically all the endemic areas, and in 1991, the Southern Cone Initiative was created, aiming to eliminate the disease transmission through eliminating the Triatoma infestans and controlling blood banks. As a result, the prevalence of chagasic donors in blood banks reduced from 4.4% in the 80s to 0.2% in 2005. In 2006, PAHO certified the interruption of transmission of Chagas’ disease through this vector in Brazil. However, there are still challenges, such as the domiciliation of new vector species, the need for medical care of the infected individuals, the prevention of alternative mechanisms of transmission, the loss of political concern regarding the disease and, the weakening of the control program.
Conclusion: Despite the progress towards control, there are still many challenges ahead to maintain and expand such control and minimise the risk of re-emergence
Monitoring the domiciliary and peridomiciliary invasion process of Triatoma rubrovaria in the State of Rio Grande do Sul, Brazil
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