Correlation of welded ignimbrites on Pantelleria (Strait of Sicily) using paleomagnetism

Although the oldest volcanic rocks exposed at Pantelleria (Strait of Sicily) are older than 300 ka, most of the island is covered by the 45–50 ka Green Tuff ignimbrite, thought to be related to the Cinque Denti caldera, and younger lavas and scoria cones. Pre-50 ka rocks (predominantly rheomorphic ignimbrites) are exposed at isolated sea cliffs, and their stratigraphy and chronology are not completely resolved. Based on volcanic stratigraphy and K/Ar dating, it has been proposed that the older La Vecchia caldera is related to ignimbrite Q (114 ka), and that ignimbrites F, D, and Z (106, 94, and 79 ka, respectively) were erupted after caldera formation. We report here the paleomagnetic directions obtained from 23 sites in ignimbrite P (133 ka) and four younger ignimbrites, and from an uncorrelated (and loosely dated) welded lithic breccia thought to record a caldera-forming eruption. The paleosecular variation of the geomagnetic field recorded by ignimbrites is used as correlative tool, with an estimated time resolution in the order of 100 years. We find that ignimbrites D and Z correspond, in good agreement with recent Ar/Ar ages constraining the D/Z eruption to 87 ka. The welded lithic breccia correlates with a thinner breccia lying just below ignimbrite P at another locality, implying that collapse of the La Vecchia caldera took place at ~130–160 ka. This caldera was subsequently buried by ignimbrites P, Q, F, and D/Z. Paleomagnetic data also show that the northern caldera margin underwent a ~10° west–northwest (outwards) tilting after emplacement of ignimbrite P, possibly recording magma resurgence in the crust.     

Morphological colour change in the American lobster (Homarus americanus) in response to background colour and UV light

American lobster (Homarus americanus) have a thick calcified cuticle, and do not exhibit rapid colour changes characteristic of other crustaceans. Thus, the plasticity of their coloration has been largely overlooked. Colour in lobsters is determined by the amount, location, and form of the carotenoid pigment astaxanthin, and it is possible for lobsters to alter colour by changing one of these characteristics of astaxanthin deposition. Here, short‐term colour variation in American lobster in response to environmental cues (background colour and ultraviolet (UV) light) was investigated in a laboratory experiment. Lobsters were reared in conditions controlling background colour (white, black) and UV light (present, absent). Digital photographic analysis was used to determine how these conditions influenced the luminescence (light or dark) of lobster colour, as well as the ratio of red to blue hues. Of the environmental variables considered within this experiment, UV light was the predominant factor, and caused lobsters to become darker in colour. In the absence of UV light, lobsters matched background colour, and turned darker in response to the darker background. Environmental matching has practical implications both for wild lobsters as they settle to the benthic habitat, and for enhancement programmes, to grow lobsters that are best suited for local habitats.     

Gamma rays from colliding winds of massive stars

Colliding winds of massive binaries have long been considered as potential sites of non-thermal high-energy photon production. This is motivated by the detection of non-thermal spectra in the radio band, as well as by correlation studies of yet unidentified EGRET γ-ray sources with source populations appearing in star formation regions. This work re-considers the basic radiative processes and its properties that lead to high energy photon production in long-period massive star systems. We show that Klein–Nishina effects as well as the anisotropic nature of the inverse Compton scattering, the dominating leptonic emission process, likely yield spectral and variability signatures in the γ-ray domain at or above the sensitivity of current or upcoming gamma ray instruments like GLAST-LAT. In addition to all relevant radiative losses, we include propagation (such as convection in the stellar wind) as well as photon absorption effects, which a priori can not be neglected. The calculations are applied to WR 140 and WR 147, and predictions for their detectability in the γ-ray regime are provided. Physically similar specimen of their kind like WR 146, WR 137, WR 138, WR 112 and WR 125 may be regarded as candidate sources at GeV energies for near-future γ-ray experiments. Finally, we discuss several aspects relevant for eventually identifying this source class as a γ-ray emitting population. Thereby we utilize our findings on the expected radiative behavior of typical colliding wind binaries in the γ-ray regime as well as its expected spatial distribution on the γ-ray sky.     

Diagnostics of solar ions: Ne VI,Mg VI,Si VIII and Mg VIII observed by SERTS

Diagnostics of solar ions Nevi, Mgvi, Siviii, and Mgviii in an active region observed by SERTS have been presented. Density, temperature, and electron pressure in the emitting source have been derived from theoretical line-ratio curves and its EUV spectrum obtained by SERTS. The variation of neon-to-magnesium and silicon-to-magnesium abundances has been discussed in the interpretation of the active region spectrum obtained by SERTS.     

Visible and near-infrared spectrophotometry of the Deep Impact ejecta of Comet 9P/Tempel 1

We have obtained optical spectrophotometry of the evolution of Comet 9P/Tempel 1 after the impact of the Deep Impact probe, using the Supernova Integral Field Spectrograph (SNIFS) at the UH 2.2-m telescope, as well as simultaneous optical and infrared spectra using the Lick Visible-to-Near-Infrared Imaging Spectrograph (VNIRIS). The spatial distribution and temporal evolution of the “violet band” CN (0-0) emission and of the 630 nm [OI] emission was studied. We found that CN emission centered on the nucleus increased in the 2 h after impact, but that this CN emission was delayed compared to the light curve of dust-scattered sunlight. The CN emission also expanded faster than the cloud of scattering dust. The emission of [OI] at 630 nm rose similarly to the scattered light, but then remained nearly constant for several hours after impact. On the day following the impact, both CN and [OI] emission concentrated on the comet nucleus had returned nearly to pre-impact levels. We have also searched for differences in the scattering properties of the dust ejected by the impact compared to the dust released under normal conditions. Compared to the pre-impact state of the comet, we find evidence that the color of the comet was slightly bluer during the post-impact rise in brightness. Long after the impact, in the following nights, the comet colors returned to their pre-impact values. This can be explained by postulating a change to a smaller particle size distribution in the ejecta cloud, in agreement with the findings from mid-infrared observations, or by postulating a large fraction of clean ice particles, or by a combination of these two.     

Two-stage contamination during crustal assimilation: isotopic evidence from volcanic rocks in eastern Nevada

Thousands of cubic kilometers of dominantly intermediate composition, metaluminous magma erupted at approximately 35 Ma in eastern Nevada. Two stages of crustal contamination are inferred from detailed study of the earliest vocanic rocks. Fine-grained mafic rocks and rocks with mixed textures, ranging from basalt to rhyolite, were contaminated with a crustal component rich in Nd but poor in Sr. Overlying plagioclaserich andesites and dacites have greater Sr and ⁸⁷Sr/⁸⁶Sr, but less Nd and lower _Nd and are interpreted to have been contaminated by a crustal component with the opposite elemental signature (i.e., poor in Nd but rich in Sr). The first contaminant represents a partial melt of the crust with plagioclase as a residual phase and the second contaminant is the residue of the partial melting event, or bulk crust. The net effect is bulk crustal assimilation, but in two bites. The separation of the crustal souree into two elementally distinct contaminants causes divergent trends with respect to the variation of ⁸⁷Sr/ ⁸⁶Sr versus _Nd that could be misinterpreted to indicate the existence of isotopically distinct crustal reservoirs. Comparison of the calculated contaminants to melting relationships in pelites is consistent with the two contammants representing melt and residue at about 30% melting. The model age of the bulk crust is approximately 2.2 Ga, consistent with an early Proterozoic crustal province inferred by other workers.     

Accumulation of hexavalent chromium by an exopolysaccharide producing marine Enterobacter cloaceae

An exopolysaccharide producing Enterobacter cloaceae (AK-I-MB-71a) was tested for its Cr (VI) tolerance. This isolate was not only resistant to this heavy metal but also showed enhanced growth and exopolysaccharide production in the presence of Cr (VI) at 25, 50 and 100 ppm concentrations. XRF analysis of both the biomass as well as the exopolysaccharide revealed that a sum total of about 60-70% chromium was accumulated by this bacterium. This indicated that this organism could prove to be a potential candidate in the field of bioremediation with respect to chromium removal.     

Conceptualization and implementation of ecosystems-based adaptation

While ecosystems-based adaptation (EbA) has been received with great interest, the requirements for EbA implementation and its precise benefits under future climate change are unclear. Furthermore, EbA’s overlap with environmental, and development policy agendas leads to ambiguity regarding what actions fall under the rubric of EbA. We analyze the projects identified by the UNFCCC as examples of EbA to understand how EbA is conceptualized and promoted by the international community. Addressing climate change is the primary objective of 58% of the EbA projects; the other 42% of projects provide adaptation benefits yet are not primarily driven by climate change. A project’s adaptation targeting is tied to its information needs. Projects whose primary objective is to address climate change are more likely to use detailed climate projections than projects whose primary objective is to address natural hazards, development or ecosystems degradation. A majority of projects do not address uncertainty in future climate change or in adaptation benefits, nor do they track adaptation outcomes. This prevalent lack of monitoring highlights the possibility of a gap between expected and realized adaptation outcomes. It also represents a lost opportunity for improving knowledge of the thresholds of effectiveness of EbA and of factors influencing EbA efficacy.