Self-similar and charged spheres in the diffusion approximation

We study spherical, charged and self--similar distributions of matter in the diffusion approximation. We propose a simple, dynamic but physically meaningful solution. For such a solution we obtain a model in which the distribution becomes static and changes to dust. The collapse is halted with damped mass oscillations about the absolute value of the total charge.Comment: 15 pages, 7 figure

Orbital free ab initio molecular dynamics study of liquid Al near melting

Producción CientíficaThe orbital free ab initio molecular dynamics method is applied to study the static and dynamic structure of liquid Al near the triple point. The method uses a new kinetic energy functional, along with a local pseudopotential constructed within the same kinetic energy functional. The results obtained for the dynamic structure factor are compared with recent experimental data

A search for late-type supergiants in the inner regions of the Milky Way

We present the results of a narrow-band infrared imaging survey of a narrow strip (12' wide) around the galactic equator between 6 deg and 21 deg of galactic longitude aimed at detecting field stars with strong CO absorption, mainly late-type giants and supergiants. Our observations include follow-up low resolution spectroscopy (R = 980) of 191 selected candidates in the H and K bands. Most of these objects have photometric and spectroscopic characteristics consistent with them being red giants, and some display broad, strong absorption wings due to water vapor absorption between the H and K bands. We also identify in our sample 18 good supergiant candidates characterized by their lack of noticeable water absorption, strong CO bands in the H and K windows, and HK_S photometry suggestive of high intrinsic luminosity and extinctions reaching up to A_V ~40 mag. Another 9 additional candidates share the same features except for weak H2O absorption, which is also observed among some M supergiants in the solar neighbourhood. Interesting differences are noticed when comparing our stars to a local sample of late-type giants and supergiants, as well as to a sample of red giants in globular clusters of moderately subsolar metallicity and to a sample of bulge stars. (...) We propose that the systematic spectroscopic differences of our inner Galaxy stars are due to their higher metallicities that cause deeper mixing in their mantles, resulting in lower surface abundances of C and O and higher abundances of CN, which contribute to the strength of the CaI and NaI features at low resolution. Our results stress the limitations of using local stars as templates for the study of composite cool stellar populations such as central starbursts in galaxies (Abridged).Comment: 21 pages (including figures), A&A accepte

The solvation and dissociation of 4-benzylaniline hydrochloride in chlorobenzene

A reaction scheme is proposed to account for the liberation of 4-benzylaniline from 4-benzylaniline hydrochloride, using chlorobenzene as a solvent at a temperature of 373 K. Two operational regimes are explored: “closed” reaction conditions correspond to the retention of evolved hydrogen chloride gas within the reaction medium, whereas an “open” system permits gaseous hydrogen chloride to be released from the reaction medium. The solution phase chemistry is analyzed by 1H NMR spectroscopy. Complete liberation of solvated 4-benzylaniline from solid 4-benzylaniline hydrochloride is possible under “open” conditions, with the entropically favored conversion of solvated hydrogen chloride to the gaseous phase thought to be the thermodynamic driver that effectively controls a series of interconnecting equilibria. A kinetic model is proposed to account for the observations of the open system

Focus on environmental risks and migration: causes and consequences

Environmental change poses risks to societies, including disrupting social and economic systems such as migration. At the same time, migration is an effective adaptation to environmental and other risks. We review novel science on interactions between migration, environmental risks and climate change. We highlight emergent findings, including how dominant flows of rural to urban migration mean that populations are exposed to new risks within destination areas and the requirement for urban sustainability. We highlight the issue of lack of mobility as a major issue limiting the effectiveness of migration as an adaptation strategy and leading to potentially trapped populations. The paper presents scenarios of future migration that show both displacement and trapped populations over the incoming decades. Papers in the special issue bring new insights from demography, human geography, political science and environmental science to this emerging field

Vulnerable marine ecosystems and biological features of Gazul mud volcano (Gulf of Cádiz): A contribution towards a potential "Gulf of Cádiz" EBSA

The Gulf of Cádiz (GoC) represents an area of socioeconomic and scientific importance for oceanographic, geological and biological processes. An interesting feature of the GoC is the presence of a large amount of mud volcanoes (MVs) and diapirs that display different seepage, seabed types, oceanographic settings and biological communities. Detailed exploration of some MVs is still needed for detecting Vulnerable Marine ecosystems (VMEs) that seem to be rare in other areas of the GoC, improving the current knowledge on its biodiversity and ecological attributes. During different expeditions (MEDWAVES-ATLAS, INDEMARES-CHICA 0610 & 0412 and ISUNEPCA 0616) carried out in different years, biological samples and videos were obtained in Gazul MV (Spanish Margin of the GoC). The study of those samples and videos has revealed the presence of several ecologically important VMEs (e.g. 3 species of reef framework-forming corals, coral gardens including solitary scleractinians, gorgonians and antipatharians, as well as deep-sea sponge aggregations and chemosynthesis-related structures) and a large number of species occurring in this MV, including new records for the European margin, threatened species and non-previously described species. The combination of different environmental and anthropogenic factors allowed the present-day persistence of these VMEs in the GoC. Some of Gazul MV biological and ecological attributes fit several criteria of the Convention on Biological Diversity for EBSA description (e.g. 1,3,4,6) that, together with those of other areas of the GoC, may contribute to the future potential nomination of an EBSA in this area of the NE Atlantic

Pursuing climate resilient coffee in Ethiopia – a critical review

This paper provides a multi-scalar examination of the Ethiopian coffee sector and its pursuit of climate resilience. Concern is growing about the potential impact of climate change on Arabica coffee in Ethiopia and the 25 million livelihoods it supports. Arabica coffee has a relatively narrow envelope of climatic suitability and recent studies suggest that the area of bioclimatically suitable space for the species in its native Ethiopia could decline dra- matically in the coming decades. We adopt a critical perspective on resilience that reflects on the situated nature of the ecology/science of coffee and climate change and the operation of social, economic, and discursive power across scales, paying particular attention to the differentiated impacts of climate change and associated resi- lience strategies. This analysis begins by reviewing Ethiopia’s Climate Resilient Green Economy strategy and argues that the current lack of attention to coffee is inappropriate considering the coffee sector’s vulnerability to climate change, economic importance and association with forests. The paper then examines the contemporary coffee sector which provides the context for reflecting on three potential responses to the threat climate change poses; a spatial response from farmers, adaptive farm management responses such as changing shade levels and the development of the country’s genetic resources to cultivate improved varieties. The analysis explores the disconnect between the interventions emerging from national and international institutions and the local con- text. The multi-scale approach highlights the presence of complex normative trade-offs associated with pursing climate resilience strategies and reinforces the importance of appreciating the dynamics which influence deci- sion-making in the country

Rural-to-Urban Labor Migration, Household Livelihoods, and the Rural Environment in Chongqing Municipality, Southwest China

Rural migration and its relationship to the rural environment have attracted increasing research interest in recent decades. Rural migration constitutes a key component of human population movement, while rural areas contain most of the world’s natural resources such as land and forests. This study empirically evaluates a conceptual framework incorporating rural household livelihoods as an integrative mediating factor between rural migration and the rural environment in the context of rural-to-urban labor migration in Chongqing Municipality, Southwest China. The analysis draws on data collected through household surveys and key informant interviews from four villages. Results confirm the hypothesis that labor-migrant and non-labor-migrant households differ significantly in livelihood activities including agricultural production, agricultural technology use, income and consumption, and resource use and management. Implications for the subsequent environmental outcomes of rural labor out-migration and corresponding natural resource management and policy in rural origin areas are discussed

Breeding systems in Tolpis (Asteraceae) in the Macaronesian islands: the Azores, Madeira and the Canaries

Plants on oceanic islands often originate from self-compatible (SC) colonizers capable of seed set by self fertilization. This fact is supported by empirical studies, and is rooted in the hypothesis that one (or few) individuals could find a sexual population, whereas two or more would be required if the colonizers were self-incompatible (SI). However, a SC colonizer would have lower heterozygosity than SI colonizers, which could limit radiation and diver sification of lineages following establishment. Limited evidence suggests that several species-rich island lineages in the family Asteraceae originated from SI colonizers with some ‘‘leakiness’’ (pseudo-self-compatibility, PSC) such that some self-seed could be produced. This study of Tolpis (Asteraceae) in Macaronesia provides first reports of the breeding system in species from the Azores and Madeira, and additional insights into variation in Canary Islands. Tolpis from the Azores and Madeira are predominately SI but with PSC. This study suggests that the breeding sys tems of the ancestors were either PSC, possibly from a single colonizer, or from SI colonizers by multiple dis seminules either from a single or multiple dispersals. Long distance colonists capable of PSC combine the advantages of reproductive assurance (via selfing) in the establishment of sexual populations from even a single colonizer with the higher heterozygosity resulting from its origin from an outcrossed source population. Evolution of Tolpis on the Canaries and Madeira has generated diversity in breeding systems, including the origin of SC. Macaronesian Tolpis is an excellent system for studying breeding system evolution in a small, diverse lineage.info:eu-repo/semantics/publishedVersio