Influence of aviation fuel composition on the formation and lifetime of contrails — a literature review

The question of how aviation fuel composition affects the formation and lifetime of contrails is a complex one. Although the theory regarding initial contrail formation is well-founded in thermodynamics and proven to be correct by measurements, there remain large uncertainties in terms of persistent contrails forming contrail cirrus. These originate both from processes which are not yet fully understood and from the complexity of quantifying the many factors of influence on their effect on climate. There is an extended cause-effect chain from fuel composition through its combustion and consequential emissions, to contrail formation and their spreading in the atmosphere, and microphysical and optical properties. These properties affect the lifetime and radiative effect of single contrails to the global and multi-annual average of the radiative effects of all contrails, and thus eventually to their climate impact. This problem extends over 17 orders of magnitude in space and time, from the scales of single molecules (about 0.1 nm) and their elementary interactions (say, 1 ns) to the global scales of climate (say, 10,000 km and 10-30 years). It is not possible to cover such a vast range with a single numerical model or with relatively few measurements

CerS6-dependent ceramide synthesis in hypothalamic neurons promotes ER/mitochondrial stress and impairs glucose homeostasis in obese mice

Dysregulation of hypothalamic ceramides has been associated with disrupted neuronal pathways in control of energy and glucose homeostasis. However, the specific ceramide species promoting neuronal lipotoxicity in obesity have remained obscure. Here, we find increased expression of the C$_{16:0}$ ceramide-producing ceramide synthase (CerS)6 in cultured hypothalamic neurons exposed to palmitate in vitro and in the hypothalamus of obese mice. Conditional deletion of CerS6 in hypothalamic neurons attenuates high-fat diet (HFD)-dependent weight gain and improves glucose metabolism. Specifically, CerS6 deficiency in neurons expressing pro-opiomelanocortin (POMC) or steroidogenic factor 1 (SF-1) alters feeding behavior and alleviates the adverse metabolic effects of HFD feeding on insulin sensitivity and glucose tolerance. POMC-expressing cell-selective deletion of CerS6 prevents the diet-induced alterations of mitochondrial morphology and improves cellular leptin sensitivity. Our experiments reveal functions of CerS6-derived ceramides in hypothalamic lipotoxicity, altered mitochondrial dynamics, and ER/mitochondrial stress in the deregulation of food intake and glucose metabolism in obesity

Plant communities as a tool in temporary ponds conservation in SW Portugal

Pond conservationTemporary ponds are seasonal wetlands annually subjected to extreme and unstable ecological conditions, neither truly aquatic nor truly terrestrial. This habitat and its flora have been poorly studied and documented because of the ephemeral character of the flora, the changeable annual weather that has a great effect on the small, herbaceous taxa and the declining abundance of temporary ponds. The objectives of this study are: (a) to define plant community diversity in terms of floristic composition of ephemeral wetlands in SW Portugal, (b) to identify temporary pond types according to their vegetation composition and (c) to identify those ponds that configure the European community priority habitat (3170* – Mediterranean temporary ponds). Vegetation sampling was conducted in 29 ponds, identifying 168 species grouped among 15 plant communities. Soil texture, pH, organic C and N content were measured, but only N and percent of clay appear to be related with the distribution of each community type. The results showed that ephemeral wetlands could be classified into four type: vernal pools, marshlands, deep ponds and disturbed wetlands. Vernal pools correspond to the Mediterranean temporary ponds (3170*), protected as priority habitat under the EU Habitats Directive. Submersed Isoetes species (Isoetes setaceum and Isoetes velatum) represents, together with Eryngium corniculatum, the indicator species for vernal pools. We identify also indicator plant communities of this priority habitat, namely I. setaceum and E. corniculatum– Baldellia ranunculoides plant communities. In this region, the conservation of temporary ponds has so far been compatible with traditional agricultural activities, but today these ponds are endangered by the intensification of agriculture and the loss of traditional land use practices and by the development of touris

Academic mobility, transnational identity capital, and stratification under conditions of academic capitalism

Academic mobility has existed since ancient times. Recently, however, academic mobility—the crossing of international borders by academics who then work ‘overseas’—has increased. Academics and the careers of academics have been affected by governments and institutions that have an interest in coordinating and accelerating knowledge production. This article reflects on the relations between academic mobility and knowledge and identity capital and their mutual entanglement as academics move, internationally. It argues that the contemporary movement of academics takes place within old hierarchies among nation states, but such old hierarchies intersect with new academic stratifications which will be described and analysed. These analytical themes in the article are supplemented by excerpts from interviews of mobile academics in the UK, USA, New Zealand, Korea and Hong Kong as selected examples of different locales of academic capitalism

Internationalisation and migrant academics: the hidden narratives of mobility

Internationalisation is a dominant policy discourse in higher education today. It is invariably presented as an ideologically neutral, coherent, disembodied, knowledgedriven policy intervention - an unconditional good. Yet it is a complex assemblage of values linked not only to economic growth and prosperity, but also to global citizenship, transnational identity capital, social cohesion, intercultural competencies and soft power (Clifford and Montgomery 2014; De Wit et al. 2015; Kim 2017; Lomer 2016; Stier 2004). Mobility is the sine qua non of the global academy (Sheller 2014). International movements, flows and networks are perceived as valuable transnational and transferable identity capital and as counterpoints to intellectual parochialism. Fluidity metaphors abound as an antidote to stasis e.g. flows, flux and circulations (Urry 2007). For some, internationalisation is conceptually linked to the political economy of neoliberalism and the spatial extension of the market, risking commodification and commercialisation (Matus and Talburt 2009). Others raise questions about what/whose knowledge is circulating and whether internationalisation is a form of re-colonisation and convergence that seeks to homogenise higher education systems (Stromquist 2007). Internationalisation policies and practices, it seems, are complex entanglements of economic, political, social and affective domains. They are mechanisms for driving the global knowledge 2 economy and the fulfilment of personal aspirations (Hoffman 2009). Academic geographical mobility is often conflated with social mobility and career advancement (Leung 2017). However, Robertson (2010: 646) suggested that ‘the romance of movement and mobility ought to be the first clue that this is something we ought to be particularly curious about.

the overlapping uncertainties of film professionals

Returning to an interpersonal micro-perspective, this chapter centers on the development of ties between the three film professionals Hushang, Kian, and Milad and examines the way they try to generate capital in German and Iranian local and transnational professional social fields. Building on previous research on social capital and the film business, the analysis brings the difficulties of interdependence in internal relations to the forefront. Furthermore, I highlight how systems of value prevailing in different social fields may both intersect and overlap, thus accounting for the fact that agency in different social fields is interconnected. The ways the three men deal with uncertainties deriving from migration and the job market illustrates that people with similar resources may still find very different ways of dealing with barriers to inclusion