Urban informality and confinement: toward a relational framework

In the 21st century, a growing number of people live ‘informal’ lives within fissures between legality and informality. Concomitantly, power relations are increasingly expressed through devices of confinement. While urban informality and confinement are on the rise often occurring simultaneously, scholars have so far studied them separately. By contrast, this article proposes a new framework for analysing urban informality and confinement relationally. It generates new insights into the role of informality in the (re)production of confinement and, vice versa, the role of confinement in shaping informal practices. While these insights are valuable for urban studies in general, the article charts new lines of research on urban marginality. It also discusses how the six articles included in this special issue signal the heuristic potential of this relational framework by empirically examining distinct urban configurations of ‘confined informalities’ and ‘informal confinements’ across the Global North and the Global South

Spin photocurrents and circular photon drag effect in (110)-grown quantum well structures

We report on the study of spin photocurrents in (110)-grown quantum well structures. Investigated effects comprise the circular photogalvanic effect and so far not observed circular photon drag effect. The experimental data can be described by an analytical expression derived from a phenomenological theory. A microscopic model of the circular photon drag effect is developed demonstrating that the generated current has spin dependent origin.Comment: 6 pages, 3 figure

Consequences of moderate ~25,000 yr lasting emission of light CO₂ into the mid-Cretaceous ocean

Future warming is predicted to shift the Earth system into a mode with progressive increase and vigour of extreme climate events possibly stimulating other mechanisms that invigorate global warming. This study provides new data and modelling investigating climatic consequences and biogeochemical feedbacks that happened in a warmer world not, vert, similar 112 Myr ago. Our study focuses on the Cretaceous Oceanic Anoxic Event (OAE) 1b and explores how the Earth system responded to a moderate not, vert, similar 25,000 yr lasting climate perturbation that is modelled to be less than 1 °C in global average temperature. Using a new chronological model for OAE 1b we present high-resolution elemental and bulk carbon isotope records from DSDP Site 545 from Mazagan Plateau off NW Africa and combine this information with a coupled atmosphere–land–ocean model. The simulations suggest that a perturbation at the onset of OAE 1b caused almost instantaneous warming of the atmosphere on the order of 0.3 °C followed by a longer (not, vert, similar 45,000 yr) period of not, vert, similar 0.8 °C cooling. The marine records from DSDP Site 545 support that these moderate swings in global climate had immediate consequences for African continental supply of mineral matter and nutrients (phosphorous), subsequent oxygen availability, and organic carbon burial in the eastern subtropical Atlantic, however, without turning the ocean anoxic. The match between modelling results and stratigraphic isotopic data support previous studies [summarized in Jenkyns, H.C., 2003. Evidence for rapid climate change in the Mesozoic–Palaeogene greenhouse world. The Royal Society, 361: 1885–1916.] in that methane emission from marine hydrates, albeit moderate in dimension, may have been the trigger for OAE 1b, though we can not finally rule out alternative mechanisms. Following the hydrate mechanism a total of 1.15 × 1018 g methane carbon (δ13C = − 60 ‰), equivalent to about 10% to the total modern gas hydrate inventory, generated the δ13Ccarb profile recorded in the section. Modelling suggests a combination of moderate-scale methane pulses supplemented by continuous methane emission at elevated levels over not, vert, similar 25,000 yr. The proposed mechanism, though difficult to finally confirm in the geological past, is arguably more likely to occur in a warmer world and apparently perturbs global climate and ocean chemistry almost instantaneously. This study shows that, once set-off, this mechanism can maintain Earth's climate in a perturbed mode over geological time leading to pronounced changes in regional climate

A refined model of Early Cretaceous South Atlantic-Southern Ocean gateway evolution based on high-resolution data from DSDP Site 511 (Falkland Plateau)

The Falkland Plateau is a key region for Early Cretaceous oceanography and climate, as its bathymetry controlled water mass and sediment exchange between the emerging South Atlantic and Southern Ocean basins. Changes in large-scale deep water circulation, induced by the evolution of marine gateways in the Falkland Plateau region, in turn, affected regional organic carbon burial dynamics with wide implications for the global carbon cycle and the formation of petroleum source rocks. In this study, we reconstruct the Early Cretaceous depositional environment on the Falkland Plateau based on new high-resolution sedimentological and geochemical data from DSDP Site 511. These proxy records are used to refine temporal constraints on the gateway opening. The record from Site 511 documents a long-term transition from a restricted outer shelf basin in the Neocomian (i.e. Berriasian-Hauterivian) to an open marine environment in the Albian. Pronounced changes in sediment source and flux, redox conditions, organic carbon burial, and ecology occurred in the Late Aptian and Early Albian, related to the opening of the shallow Falkland Plateau Gateway and the deep Georgia Basin Gateway, respectively. In both cases, the opening was preceded by a succession of paleoenvironmetal changes, which are interpreted to reflect partial opening and progressive widening/deepening of both gateways. These early stages of gateway evolution commenced in the Early Aptian and Late Aptian, respectively, several million years before a full intermediate/deep water connection between the South Atlantic and Southern Ocean basins was established