Imaging of Titan from the Cassini spacecraft

Titan, the largest moon of Saturn, is the only satellite in the Solar System with a substantial atmosphere. The atmosphere is poorly understood and obscures the surface, leading to intense speculation about Titan's nature. Here we present observations of Titan from the imaging science experiment onboard the Cassini spacecraft that address some of these issues. The images reveal intricate surface albedo features that suggest aeolian, tectonic and fluvial processes; they also show a few circular features that could be impact structures. These observations imply that substantial surface modification has occurred over Titan's history. We have not directly detected liquids on the surface to date. Convective clouds are found to be common near the south pole, and the motion of mid-latitude clouds consistently indicates eastward winds, from which we infer that the troposphere is rotating faster than the surface. A detached haze at an altitude of 500 km is 150-200 km higher than that observed by Voyager, and more tenuous haze layers are also resolved.     

Structural insight into antibiotic fosfomycin biosynthesis by a mononuclear iron enzyme

The biosynthetic pathway of the clinically important antibiotic fosfomycin uses enzymes that catalyse reactions without precedent in biology. Among these is hydroxypropylphosphonic acid epoxidase, which represents a new subfamily of non-haem mononuclear iron enzymes. Here we present six X-ray structures of this enzyme: the apoenzyme at 2.0 A resolution; a native Fe(II)-bound form at 2.4 A resolution; a tris(hydroxymethyl)aminomethane-Co(II)-enzyme complex structure at 1.8 A resolution; a substrate-Co(II)-enzyme complex structure at 2.5 A resolution; and two substrate-Fe(II)-enzyme complexes at 2.1 and 2.3 A resolution. These structural data lead us to suggest how this enzyme is able to recognize and respond to its substrate with a conformational change that protects the radical-based intermediates formed during catalysis. Comparisons with other family members suggest why substrate binding is able to prime iron for dioxygen binding in the absence of alpha-ketoglutarate (a co-substrate required by many mononuclear iron enzymes), and how the unique epoxidation reaction of hydroxypropylphosphonic acid epoxidase may occur.     

Admixture mapping for hypertension loci with genome-scan markers

Identification of genetic variants that contribute to risk of hypertension is challenging. As a complement to linkage and candidate gene association studies, we carried out admixture mapping using genome-scan microsatellite markers among the African American participants in the US National Heart, Lung, and Blood Institute's Family Blood Pressure Program. This population was assumed to have experienced recent admixture from ancestral groups originating in Africa and Europe. We used a set of unrelated individuals from Nigeria to represent the African ancestral population and used the European Americans in the Family Blood Pressure Program to provide estimates of allele frequencies for the European ancestors. We genotyped a common set of 269 microsatellite markers in the three groups at the same laboratory. The distribution of marker location-specific African ancestry, based on multipoint analysis, was shifted upward in hypertensive cases versus normotensive controls, consistent with linkage to genes conferring susceptibility. This shift was largely due to a small number of loci, including five adjacent markers on chromosome 6q and two on chromosome 21q. These results suggest that chromosome 6q24 and 21q21 may contain genes influencing risk of hypertension in African Americans.     

The Engagement Approach to Real-World Problem Solving: Toward a Coherent Soft-Systems-Based Theoretical Platform for Real-World Problem Solving

This paper presents an approach to understanding problem solving and innovation from the perspective of engagement. The approach is derived primarily from two research projects undertaken over the last 5 years. The first one into the apparent Comparison Parado in Soft Systems Methodology, and the second an 18-month research program into the social reality implied by Soft Systems Methodology. Engagement is argued to be the innovation of a framework of ideas within a social context. In this sense engagement is an extension of the nature in which humans take ideas and place them inside a social context and use this as a platform to make sense of their environment and take action in such surroundings with an eye to understanding, learning, meaning, adaptation, innovation, and interpretation of such situations. Therefore, this paper presents a conjectured model of Engagement that is argued to be useful in helping to manage social complexity and real-world problem-solving activity. The paper positions engagement as a purely theoretical approach with multidisciplinary applications for whoever would like to use it.     

Systemic Cognition During the Sub-Prime Crisis: Lessons and Research Implications

This paper uses the example of the global financial crisis (GFC) of 2008?C2009 to demonstrate how patterns of systemic cognition influenced outcomes during the crisis. This paper focuses on systemic patterns that emerged during the sub-prime crisis. By reviewing systemic patterns and reflecting on the assumptions of actors it is believed that further insight for research potential could be revealed. I argue that patterns of systemic ??cognition?? that emerge during complex social events can be captured and reflected on. This provides useful insight into the interpretative structures of messy problems that in turn reveals previously undiscovered systemic thinking. The paper uses this illustration of the GFC to structure a debate about future research possibilities.     

A genome-wide association study identifies KIAA0350 as a type 1 diabetes gene

Type 1 diabetes (T1D) in children results from autoimmune destruction of pancreatic beta cells, leading to insufficient production of insulin. A number of genetic determinants of T1D have already been established through candidate gene studies, primarily within the major histocompatibility complex but also within other loci. To identify new genetic factors that increase the risk of T1D, we performed a genome-wide association study in a large paediatric cohort of European descent. In addition to confirming previously identified loci, we found that T1D was significantly associated with variation within a 233-kb linkage disequilibrium block on chromosome 16p13. This region contains KIAA0350, the gene product of which is predicted to be a sugar-binding, C-type lectin. Three common non-coding variants of the gene (rs2903692, rs725613 and rs17673553) in strong linkage disequilibrium reached genome-wide significance for association with T1D. A subsequent transmission disequilibrium test replication study in an independent cohort confirmed the association. These results indicate that KIAA0350 might be involved in the pathogenesis of T1D and demonstrate the utility of the genome-wide association approach in the identification of previously unsuspected genetic determinants of complex traits.     

The conserved protein DCN-1/Dcn1p is required for cullin neddylation in C. elegans and S. cerevisiae

SCF-type E3 ubiquitin ligases are multi-protein complexes required for polyubiquitination and subsequent degradation of target proteins by the 26S proteasome. Cullins, together with the RING-finger protein Rbx1, form the catalytic core of the ligase, and recruit the substrate-recognition module. Cycles of covalent modification of cullins by the ubiquitin-like molecule Nedd8 (neddylation) and removal of Nedd8 by the COP9 signalosome (deneddylation) positively regulate E3 ligase activity. Here we report the identification and analysis of a widely conserved protein that is required for cullin neddylation in the nematode Caenorhabditis elegans and the yeast Saccharomyces cerevisiae. C. elegans DCN-1 and S. cerevisiae Dcn1p (defective in cullin neddylation) are characterized by a novel UBA-like ubiquitin-binding domain and a DUF298 domain of unknown function. Consistent with their requirements for neddylation, DCN-1 and Dcn1p directly bind Nedd8 and physically associate with cullins in both species. Moreover, overexpression of Dcn1p in yeast results in the accumulation of Nedd8-modified cullin Cdc53p. Both in vivo and in vitro experiments indicate that Dcn1p does not inhibit deneddylation of Cdc53p by the COP9 signalosome, but greatly increases the kinetics of the neddylation reaction.     

Primary forests are irreplaceable for sustaining tropical biodiversity

Human-driven land-use changes increasingly threaten biodiversity, particularly in tropical forests where both species diversity and human pressures on natural environments are high. The rapid conversion of tropical forests for agriculture, timber production and other uses has generated vast, human-dominated landscapes with potentially dire consequences for tropical biodiversity. Today, few truly undisturbed tropical forests exist, whereas those degraded by repeated logging and fires, as well as secondary and plantation forests, are rapidly expanding. Here we provide a global assessment of the impact of disturbance and land conversion on biodiversity in tropical forests using a meta-analysis of 138 studies. We analysed 2,220 pairwise comparisons of biodiversity values in primary forests (with little or no human disturbance) and disturbed forests. We found that biodiversity values were substantially lower in degraded forests, but that this varied considerably by geographic region, taxonomic group, ecological metric and disturbance type. Even after partly accounting for confounding colonization and succession effects due to the composition of surrounding habitats, isolation and time since disturbance, we find that most forms of forest degradation have an overwhelmingly detrimental effect on tropical biodiversity. Our results clearly indicate that when it comes to maintaining tropical biodiversity, there is no substitute for primary forests.     

The recent breakup of an asteroid in the main-belt region

The present population of asteroids in the main belt is largely the result of many past collisions. Ideally, the asteroid fragments resulting from each impact event could help us understand the large-scale collisions that shaped the planets during early epochs. Most known asteroid fragment families, however, are very old and have therefore undergone significant collisional and dynamical evolution since their formation. This evolution has masked the properties of the original collisions. Here we report the discovery of a family of asteroids that formed in a disruption event only 5.8 +/- 0.2 million years ago, and which has subsequently undergone little dynamical and collisional evolution. We identified 39 fragments, two of which are large and comparable in size (diameters of approximately 19 and approximately 14 km), with the remainder exhibiting a continuum of sizes in the range 2-7 km. The low measured ejection velocities suggest that gravitational re-accumulation after a collision may be a common feature of asteroid evolution. Moreover, these data can be used to check numerical models of larger-scale collisions.