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Molecular markers were used to assess polymorphism between and within the genetic bases of coffee (i.e. Typica and Bourbon) spread from Yemen since the early 18th century that have given rise to most arabica cultivars grown world-wide. Eleven Coffea arabica accessions derived from the disseminated bases were evaluated by amplified fragment length polymorphism (AFLP) using 37 primer combinations and simple-sequence repeats (SSRs) produced by six microsatellites. Four cultivars growing in Yemen and 11 subspontaneous accessions collected in the primary centre of diversity of the species were included in the study in order to define their relationship with the accessions derived from the genetic bases of cultivars. One hundred and seven AFLP markers were used to calculate genetic distances and construct a dendrogram. The accessions derived from the disseminated bases were grouped separately, according to their genetic origin, and were distinguished from the subspontaneous accessions. The Yemen cultivars were classified with the Typica-derived accessions. Except for one AFLP marker, all AFLP and SSR markers present in the cultivated accessions were also detected in the subspontaneous accessions. Polymorphism among the subspontaneous accessions was much higher than among the cultivated accessions. It was very low within the genetic bases, confirming the historical documentation on their dissemination. The results enabled a discussion of the genetic diversity reductions that successively occurred during the dissemination of C. arabica from its primary centre of diversity.

Since 9/11, the rise of Islamist extremism has taken hold of the national imagination as the greatest threat facing the USA. The 2013 Boston Marathon bombing seemed to add a new chapter to the War on Terror with the ‘introduction’of homegrown terrorists who wantonly kill innocent Americans, just as the 19 hijackers did. They are evil. Yet, the narrative of the Tsarnaevs that emerged shortly after the attack crafted a far more ambiguous relationship to these threatening bodies. What allows for such ambiguity, given the Tsarnaevs’murderous acts? In this article, I look at how identity demarcation was used directly after the bombing as a form of securitization, paying particular attention to the role of the stranger. Contributing to both identity and ontological security theory, I argue that analyzing the discursive (re) presentation of the liminal and its mediation between inclusion and exclusion best captures the multifaceted nature of security, which includes both ontological and material well-being. I show that the particular manner in which the stranger shows up in the portrayal of the Boston attack helps steer American identity practice (s) down specific paths of meaning-making that are not as clearcut as ‘righteous Self’versus ‘evil Other.’

The irreversible conversion of methane into higher hydrocarbons in Titan's stratosphere implies a surface or subsurface methane reservoir. Recent measurements from the cameras aboard the Cassini orbiter fail to see a global reservoir, but the methane and smog in Titan's atmosphere impedes the search for hydrocarbons on the surface. Here we report spectra and high-resolution images obtained by the Huygens Probe Descent Imager/Spectral Radiometer instrument in Titan's atmosphere. Although these images do not show liquid hydrocarbon pools on the surface, they do reveal the traces of once flowing liquid. Surprisingly like Earth, the brighter highland regions show complex systems draining into flat, dark lowlands. Images taken after landing are of a dry riverbed. The infrared reflectance spectrum measured for the surface is unlike any other in the Solar System; there is a red slope in the optical range that is consistent with an organic material such as tholins, and absorption from water ice is seen. However, a blue slope in the near-infrared suggests another, unknown constituent. The number density of haze particles increases by a factor of just a few from an altitude of 150 km to the surface, with no clear space below the tropopause. The methane relative humidity near the surface is 50 per cent. New views of Titan The Huygens probe landed on Titan on 14 January this year, and seven papers published in this issue record the encounter. They describe a world that resembles a primitive Earth, complete with weather systems and geological activity. The ‘Huygens on Titan’ section opens with an overview of the descent and landing and a News and Views piece. Tomasko et al . describe the dry riverbed and drainage channels seen during Huygens' descent, evidence that liquid methane falls as rain or erupts from cryovolcanoes, periodically flooding the surface. This paper includes the images used on the cover to the Huygens section. Niemann et al . measured the abundances of isotopes of argon, nitrogen and carbon in the atmosphere, and conclude that there is no evidence that Titan's methane comes from biological activity. Fulchignoni et al . obtained precise measurements of temperature and pressure from the upper atmosphere right down to the surface. On the way down Huygens recorded evidence for lightning. Zarnecki et al . report that the probe landed on a relatively smooth surface of icy grains with the consistency of wet clay or sand. Isräl et al . report that the aerosols in Titan's clouds have solid cores made from complex organic molecules containing carbon and nitrogen. And Bird et al . found that on average Titan's winds blow in the same direction as the moon rotates, and that close to the surface these winds are very weak, travelling at around walking speed.

Aims/hypothesis Our goal was to identify a set of human adipose tissue macrophage (ATM)-specific markers and investigate whether their gene expression in subcutaneous adipose tissue (SAT) as well as in visceral adipose tissue (VAT) is related to obesity and to the occurrence of the metabolic syndrome. Methods ATM-specific markers were identified by DNA microarray analysis of adipose tissue cell types isolated from SAT of lean and obese individuals. We then analysed gene expression of these markers by reverse transcription quantitative PCR in paired samples of SAT and VAT from 53 women stratified into four groups (lean, overweight, obese and obese with the metabolic syndrome). Anthropometric measurements, euglycaemic-hyperinsulinaemic clamp, blood analysis and computed tomography scans were performed. Results A panel of 24 genes was selected as ATM-specific markers based on overexpression in ATM compared with other adipose tissue cell types. In SAT and VAT, gene expression of ATM markers was lowest in lean and highest in the metabolic syndrome group. mRNA levels in the two fat depots were negatively correlated with glucose disposal rate and positively associated with indices of adiposity and the metabolic syndrome. Conclusions/interpretation In humans, expression of ATM-specific genes increases with the degree of adiposity and correlates with markers of insulin resistance and the metabolic syndrome to a similar degree in SAT and in VAT.

Observations of Saturn's satellite Enceladus using Cassini's Visual and Infrared Mapping Spectrometer instrument were obtained during three flybys of Enceladus in 2005. Enceladus' surface is composed mostly of nearly pure water ice except near its south pole, where there are light organics, CO₂, and amorphous and crystalline water ice, particularly in the region dubbed the \"tiger stripes.\" An upper limit of 5 precipitable nanometers is derived for CO in the atmospheric column above Enceladus, and 2% for NH₃ in global surface deposits. Upper limits of 140 kelvin (for a filled pixel) are derived for the temperatures in the tiger stripes.

Nineteen arabica coffee introgression lines ([BC.sub.1][F.sub.4]) and two accessions derived from a spontaneous interspecific cross (i.e. Timor Hybrid) between Coffea arabica (2n = 4x = 44) and C. canephora (2n = 2x = 22) were analysed for the introgression of C. canephora genetic material. The Timor Hybrid-derived genotypes were evaluated by AFLP, using 42 different primer combinations, and compared to 23 accessions of C. arabica and 8 accessions of C. canephora. A total of 1062 polymorphic fragments were scored among the 52 accessions analysed. One hundred and seventy-eight markers consisting of 109 additional bands (i.e. introgressed markers) and 69 missing bands distinguished the group composed of the Timor Hybrid-derived genotypes from the accessions of C. arabica. AFLP therefore seemed to be an extremely efficient technique for DNA marker generation in coffee as well as for the detection of introgression in C. arabica. The genetic diversity observed in the Timor Hybrid-derived genotypes appeared to be approximately double that in C. arabica. Although representing only a small proportion of the genetic diversity available in C. canephora, the Timor Hybrid obviously constitutes a considerable source of genetic diversity for arabica breeding. Analysis of genetic relationships among the Timor Hybrid-derived genotypes suggested that introgression was not restricted to chromosome substitution but also involved chromosome recombinations. Furthermore, the Timor Hybrid-derived genotypes varied considerably in the number of AFLP markers attributable to introgression. In this way, the introgressed markers identified in the analysed arabica coffee introgressed genotypes were estimated to represent from 9% to 29% of the C. canephora genome. Nevertheless, the amount of alien genetic material in the introgression arabica lines remains substantial and should justify the development of adapted breeding strategies.

The importance of introgressive hybridization in plant evolution has long been recognized. Nevertheless, information on gene flow between allopolyploids and their diploid relatives is very limited, even though gene flow could play a major role in polyploid establishment and evolution. Here, we investigated the processes governing hybrid formation and introgression between the allotetraploid Coffea arabica and one of its ancestral diploid progenitors, C. canephora, in a sympatric zone of New Caledonia. The occurrence of a large assortment of hybridization events between the 2 coffee species is clearly established. First-generation hybrids (F1) and post-F1 hybrids were characterized. The involvement of unreduced gametes of C. canephora is suggested, because tetraploid F1 hybrid plants were detected. Moreover, although bidirectional mating was observed, only unidirectional gene flow from C. canephora to C. arabica was noted in post-F1 hybrids. Most of the collected post-F1 hybrid plants exhibited a high level of introgression, and the frequency of introgression observed among the different analyzed loci was homogeneous, suggesting no significant counterselection against introgressions from C. canephora. Overall, the New Caledonian central mountains appear to be a highly favourable environment for introgressive hybridization and a genetic diversity center for C. arabica.

In order to promote genome research on coffee trees, one of the most important tropical crops, a bacterial artificial chromosome (BAC) library of the coffee allotetraploid species, Coffea arabica, was constructed. The variety IAPAR 59, which is widely distributed in Latin America and exhibits a fair level of resistance to several pathogens, was chosen. High-efficiency BAC cloning of the high molecular weight genomic DNA partially digested by HindIII was achieved. In total, the library contains 88,813 clones with an average insert size of 130 kb, and represents approximately eight C. arabica dihaploid genome equivalents. One original feature of this library is that it can be divided into four sublibraries with mean insert sizes of 96, 130, 183 and 210 kb. Characterisation of the library showed that less than 4.5% of the clones contained organelle DNA. Furthermore, this library is representative and shows good genome coverage, as established by hybridisation screening of high-density filters using a number of nuclear probes distributed across the allotetraploid genome. This Arabica BAC library, the first large-insert DNA library so far constructed for the genus Coffea, is well-suited for many applications in genome research, including physical mapping, map-based cloning, functional and comparative genomics as well as polyploid genome analyses.

Cassini's Titan flyby The surface of Saturn's largest moon, Titan, is coated in a dense methane-rich atmosphere that prevents high-resolution imaging at visible wavelengths. During its first Titan flyby last October, the Cassini spacecraft's visual and infrared mapping spectrometer (VIMS) was able to reveal detailed surface structures, as reported in this issue. Notable features include a circular structure 30 km in diameter, thought to be a cryogenic dome. This may be volcanic, which could explain how the methane in Titan's atmosphere is replenished. Titan is the only satellite in our Solar System with a dense atmosphere. The surface pressure is 1.5 bar (ref. 1 ) and, similar to the Earth, N 2 is the main component of the atmosphere. Methane is the second most important component 2 , but it is photodissociated on a timescale of 10 7  years (ref. 3 ). This short timescale has led to the suggestion that Titan may possess a surface or subsurface reservoir of hydrocarbons 4 , 5 to replenish the atmosphere. Here we report near-infrared images of Titan obtained on 26 October 2004 by the Cassini spacecraft. The images show that a widespread methane ocean does not exist; subtle albedo variations instead suggest topographical variations, as would be expected for a more solid (perhaps icy) surface. We also find a circular structure ∼30 km in diameter that does not resemble any features seen on other icy satellites. We propose that the structure is a dome formed by upwelling icy plumes that release methane into Titan's atmosphere.

Spectra from Cassini's Visual and Infrared Mapping Spectrometer reveal that the horizontal structure, height, and optical depth of Titan's clouds are highly dynamic. Vigorous cloud centers are seen to rise from the middle to the upper troposphere within 30 minutes and dissipate within the next hour. Their development indicates that Titan's clouds evolve convectively; dissipate through rain; and, over the next several hours, waft downwind to achieve their great longitude extents. These and other characteristics suggest that temperate clouds originate from circulation-induced convergence, in addition to a forcing at the surface associated with Saturn's tides, geology, and/or surface composition.