Multi-messenger observations of a binary neutron star merger

On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of ~1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg2 at a luminosity distance of 40+8-8 Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 Mo. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at ~40 Mpc) less than 11 hours after the merger by the One- Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over ~10 days. Following early non-detections, X-ray and radio emission were discovered at the transient’s position ~9 and ~16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta

Short-term variability in biogenic sulphur emissions from a florida spartina alterniflora marsh

Emissions of biogenic sulphur gases from a Florida Spartina alterniflora zone were measured over several tidal and diel cycles using a dynamic flow chamber technique, corroborating recently published information in the literature. The flux of hydrogen sulfide from individual measurements is shown to vary by over four orders of magnitude, and correlates primarily with the stage of the tidal cycle. In contrast, the fluxes of dimethyl sulphide, carbon disulphide and dimethyl disulphide vary by less than an order of magnitude and correlate primarily with the diurnal temperature changes in the sediment surface. These differences are discussed in terms of the various biological and physical parameters which may regulate the release of reduced sulphur compounds to the atmosphere. © 1987

Spatial and diel variability in the emissions of some biogenic sulfur compounds from a Florida Spartina alterniflora coastal zone

Emission rates of the biogenic reduced sulfur gases dimethyl sulfide, dimethyl disulfide, carbon disulfide and hydrogen sulfide were measured from several environments within a Florida Spartina alterniflora coastal zone. Spatial and diel variability was observed in the emission rates of all the sulfur gases. The speciation and magnitude of sulfur emissions can be related to site elevation and the spatial variability of vegetation coverage. Dimethyl sulfide appears to be a metabolic byproduct of S. alterniflora. © 1987

Electrofluorochromism in π-conjugated ionic liquid crystals

Materials in which photoluminescence is modulated by redox processes are known as electrofluorochromic. Intrinsically switchable fluorophores, incorporating both redox and fluorescent moieties, could be ideal electrofluorochromic materials if they possess high fluorescence quantum yields in at least one of their redox states. Fluorescent liquid crystals with redox active centres could combine the above requirements with the advantage to work in bulk anisotropic phases. However, electrofluorochromic liquid crystals have not been reported yet because their synthesis is challenging due to aggregation-caused fluorescent quenching. Here we show the first examples of electrofluorochromic π-conjugated ionic liquid crystals based on thienoviologens. These ordered materials, combining ionic and electronic functions, are highly fluorescence in the bulk state (quantum yield>60%). Their direct electrochemical reduction leads to fast and reversible bulk electrofluorochromic response in both columnar and smectic phases allowing for fluorescence intensity modulation and colour tuning

Study of wet precipitation and its chemical composition in South of Brazil

The purpose of this study is to analyze the chemical composition of wet precipitation in samples collected at three stations in the Candiota region in the Brazilian state of Rio Grande do Sul (RS). Samples were collected in 2004. Variables analyzed in wet precipitation were pH, conductivity, and concentration of Cl-, NO3-, SO4(2-) F-, Na+, Ca2+, Mg2+, K+, NH4+, Cu, Zn, Fe, Mn, Pb, Ni, Cd, Co, and Cr. SO2 and NO2 distribution over the time were also evaluated. Results have showed that pH < 5.6 are found mostly at Candiota airport (85%), followed by Aceguá (72%) and Três Lagoas (65%). Enrichment Factor of the studied ions in wet deposition revealed higher Ca2+ and SO4(2-) enrichment in Três Lagoas. Factor Analysis applied to metals and major ions allowed identifying the major sources. While Cl-, Na+, Mg2+ are of marine origin, SO4(2-), NO3-, NH4+ ,F- come from anthropogenic sources. Except for Fe and Mn originating from the soil dust, the metals studied showed to have anthropogenic influence The average SO2 and NO2 concentration, as well as SO4(2-) and NO3- in wet precipitation in the Candiota region showed higher concentrations during the warmer months.<br>O objetivo deste estudo é analisar a composição química da precipitação úmida em amostras coletadas em três estações na região de Candiota no Estado do Rio Grande do Sul (RS) Brasil. Amostras foram coletadas em 2004. Variáveis analisadas na precipitação úmida foram pH, condutividade e concentração de Cl-, NO3-, SO4(2-) F-, Na+, Ca2+, Mg2+, K+, NH4+, Cu, Zn, Fe, Mn, Pb, Ni, Cd, Co e Cr. Distribuição no tempo de SO2 e NO2 também foi avaliada. Resultados mostraram que pH < 5,6 são encontrados em sua maioria no aeroporto de Candiota (85%), seguidos pelo Aceguá (72%) e Três Lagoas (65%). Fator de Enriquecimento dos íons estudados na deposição úmida revelou maior enriquecimento de Ca2+ e SO4² em Três Lagoas. Análise Fatorial aplicada aos metais e íons maiores permitiu identificação de fontes maiores. Enquanto Cl-, Na+, Mg2+ são de origem marinha, SO4(2-), NO3-, NH4+, F- são provenientes de fontes antropogênicas. Exceto Fe e Mn originários de poeira do solo, os metais estudados mostraram ter influência antropogênica. A média da concentração de SO2 e NO2, bem como SO4(2-) e NO3- na precipitação úmida na região de Candiota mostrou maiores concentrações durante os meses mais quentes

Surface modification of a granite building stone in central Rio de Janeiro

In order to evaluate environmental controls on the soiling formation and decay of building stones a set of mapping and physical and chemical analyses were carried out on granite from a historical church in the polluted centre of Rio de Janeiro. These techniques highlight the increasing of threatening damage on generally perceived as a durable building material, caused by granular disaggregation and contour scaling in areas close to ground level. Mapping also indicated the formation of black crusts over entire building façades, concentrated on areas sheltered from rain-wash. Analyses demonstrated the influence of marine aerosols, rock and mortar composition and mostly of the atmospheric pollutants on the decay and soiling of the granite. Much of the decay is associated specifically with the presence of halite (NaCl) and gypsum (CaS04.2H2O). The fact that black, gypsum crusts are able to develop over entire façades in a humid subtropical environment is testimony to the high levels of local pollution, especially particulate deposition. Reduced rainwash, in sheltered micro-environments of narrow, canyon-like streets, overcomes the gypsum tendency to bewashed away from buildings façades. These observations further highlight that decay processes are primarily controlled by microclimatic conditions.<br>Com o objetivo de se avaliar os controles ambientais na formação de crostas e deterioração de rochas ornamentais em fachadas de prédios históricos, uma série de mapeamentos e análises fisicas e químicas foram realizados em granitos da fachada de uma igreja histórica numa área poluída no centro da cidade do Rio de Janeiro. Estas técnicas destacam a ameaça crescente dos danos causados pela desagregação granular e esfoliação da rocha que é fortemente percebido por se tratar de um material de alta durabilidade usado na fachada do prédio em áreaslocalizadas ao nível do chão. O exercício de mapeamento possibilitou a demarcação e observação das áreas afetadas pela formação de crosta negra sobre toda a fachada do prédio, principalmente concentradas em áreas abrigadas da ação da chuva. As análises demonstraram a influência de aerosóis marinhos, composição das rochas e argamassas e dos poluentes atmosféricos na deterioração e formação de crostas no granito. Muito da deterioração é associado especificamente a presença de sais, tais como halita (NaCl) e gipsita (CaS0(4).2H2O). O fato da crosta negra de gipsita ser capaz de se desenvolver sobre toda a fachada do prédio, em um ambiente sub-tropical úmido é testemunha da eficácia dos altos níveis de poluição local, especialmente da deposição de particulados, e da reduzida lavagem pela chuva em um micro-ambiente protegido,em ruas estreitas, que funcionam como corredores de poluição, impedindo a tendência da gipsita ser lavada das fachadas dos prédios históricos. Essa observação destaca que os processos de intemperismo operante, são principalmente controlados por condições microclimáticas