Sustainability Transitions and the Nature of Technology

For more than 20?years, sustainable development has been advocated as a way of tackling growing global environmental and social problems. The sustainable development discourse has always had a strong technological component and the literature boasts an enormous amount of debate on which technologies should be developed and employed and how this can most efficiently be done. The mainstream discourse in sustainable development argues for an eco-efficiency approach in which a technology push strategy boosts efficiency levels by a factor 10 and more in industrialised and developing countries. A minority argues for a socio-cultural lifestyle switch, relying on new values, quality of life, sufficiency and redistribution strategies, with calls for appropriate and soft technologies. It is remarkable, however, that the articles, books and policy debates on sustainability seldom explicitly draw in a discussion of the nature of technology, how technology influences and is influenced by society, and what this implies for sustainable development. The mainstream interprets technology as neutral and instrumental: technology is no more than an instrument to reach a goal; it cannot be judged on its intrinsic characteristics, only on its use. The alternative view often builds on an autonomous and substantive interpretation of technology: technology is an autonomous, almost uncontrollable power that fundamentally reshapes our culture. A more balanced approach seems to be growing in the research on socio-technical sustainability transitions where the focus shifts to the co-evolution of technology and society, and to the networks, seamless webs and complex multi-actor processes that may carry a sustainability transition forward. This approach builds on insights from recent traditions in the philosophy and sociology of technology, in particular the social construction of technology (SCOT) and actor-network theory (ANT). While this provides for a better understanding of the nature and potential role of technology in sustainability policies, it remains to be seen whether it will actually influence the choice between technologies. This article investigates the different conceptualisations of technology in the sustainability debate. It first distinguishes between different approaches of sustainability and how these are related to differing views on technology. It then moves on to how the socio-technical transitions research incorporates insights from contemporary philosophy and sociology of technology. It reflects on the potential of transitions research to give guidance in technology choices, suggesting that the transition approach might be strengthened by drawing in insights from critical theory of technology and by taking a more political stance in defining sustainable development.     

Protein targeting and degradation are coupled for elimination of mislocalized proteins

A substantial proportion of the genome encodes membrane proteins that are delivered to the endoplasmic reticulum by dedicated targeting pathways. Membrane proteins that fail targeting must be rapidly degraded to avoid aggregation and disruption of cytosolic protein homeostasis. The mechanisms of mislocalized protein (MLP) degradation are unknown. Here we reconstitute MLP degradation in vitro to identify factors involved in this pathway. We find that nascent membrane proteins tethered to ribosomes are not substrates for ubiquitination unless they are released into the cytosol. Their inappropriate release results in capture by the Bag6 complex, a recently identified ribosome-associating chaperone. Bag6-complex-mediated capture depends on the presence of unprocessed or non-inserted hydrophobic domains that distinguish MLPs from potential cytosolic proteins. A subset of these Bag6 complex 'clients' are transferred to TRC40 for insertion into the membrane, whereas the remainder are rapidly ubiquitinated. Depletion of the Bag6 complex selectively impairs the efficient ubiquitination of MLPs. Thus, by its presence on ribosomes that are synthesizing nascent membrane proteins, the Bag6 complex links targeting and ubiquitination pathways. We propose that such coupling allows the fast tracking of MLPs for degradation without futile engagement of the cytosolic folding machinery.     

Neural network computation with DNA strand displacement cascades

The impressive capabilities of the mammalian brain--ranging from perception, pattern recognition and memory formation to decision making and motor activity control--have inspired their re-creation in a wide range of artificial intelligence systems for applications such as face recognition, anomaly detection, medical diagnosis and robotic vehicle control. Yet before neuron-based brains evolved, complex biomolecular circuits provided individual cells with the 'intelligent' behaviour required for survival. However, the study of how molecules can 'think' has not produced an equal variety of computational models and applications of artificial chemical systems. Although biomolecular systems have been hypothesized to carry out neural-network-like computations in vivo and the synthesis of artificial chemical analogues has been proposed theoretically, experimental work has so far fallen short of fully implementing even a single neuron. Here, building on the richness of DNA computing and strand displacement circuitry, we show how molecular systems can exhibit autonomous brain-like behaviours. Using a simple DNA gate architecture that allows experimental scale-up of multilayer digital circuits, we systematically transform arbitrary linear threshold circuits (an artificial neural network model) into DNA strand displacement cascades that function as small neural networks. Our approach even allows us to implement a Hopfield associative memory with four fully connected artificial neurons that, after training in silico, remembers four single-stranded DNA patterns and recalls the most similar one when presented with an incomplete pattern. Our results suggest that DNA strand displacement cascades could be used to endow autonomous chemical systems with the capability of recognizing patterns of molecular events, making decisions and responding to the environment.     

The Sagittarius impact as an architect of spirality and outer rings in the Milky Way

Like many galaxies of its size, the Milky Way is a disk with prominent spiral arms rooted in a central bar, although our knowledge of its structure and origin is incomplete. Traditional attempts to understand our Galaxy's morphology assume that it has been unperturbed by major external forces. Here we report simulations of the response of the Milky Way to the infall of the Sagittarius dwarf galaxy (Sgr), which results in the formation of spiral arms, influences the central bar and produces a flared outer disk. Two ring-like wrappings emerge towards the Galactic anti-Centre in our model that are reminiscent of the low-latitude arcs observed in the same area of the Milky Way. Previous models have focused on Sgr itself to reproduce the dwarf's orbital history and place associated constraints on the shape of the Milky Way gravitational potential, treating the Sgr impact event as a trivial influence on the Galactic disk. Our results show that the Milky Way's morphology is not purely secular in origin and that low-mass minor mergers predicted to be common throughout the Universe probably have a similarly important role in shaping galactic structure.     

The earliest evidence for anatomically modern humans in northwestern Europe

The earliest anatomically modern humans in Europe are thought to have appeared around 43,000-42,000 calendar years before present (43-42 kyr cal BP), by association with Aurignacian sites and lithic assemblages assumed to have been made by modern humans rather than by Neanderthals. However, the actual physical evidence for modern humans is extremely rare, and direct dates reach no farther back than about 41-39 kyr cal BP, leaving a gap. Here we show, using stratigraphic, chronological and archaeological data, that a fragment of human maxilla from the Kent's Cavern site, UK, dates to the earlier period. The maxilla (KC4), which was excavated in 1927, was initially diagnosed as Upper Palaeolithic modern human. In 1989, it was directly radiocarbon dated by accelerator mass spectrometry to 36.4-34.7 kyr cal BP. Using a Bayesian analysis of new ultrafiltered bone collagen dates in an ordered stratigraphic sequence at the site, we show that this date is a considerable underestimate. Instead, KC4 dates to 44.2-41.5 kyr cal BP. This makes it older than any other equivalently dated modern human specimen and directly contemporary with the latest European Neanderthals, thus making its taxonomic attribution crucial. We also show that in 13 dental traits KC4 possesses modern human rather than Neanderthal characteristics; three other traits show Neanderthal affinities and a further seven are ambiguous. KC4 therefore represents the oldest known anatomically modern human fossil in northwestern Europe, fills a key gap between the earliest dated Aurignacian remains and the earliest human skeletal remains, and demonstrates the wide and rapid dispersal of early modern humans across Europe more than 40 kyr ago.     

Monitoring temporal change in riparian vegetation of Great Basin National Park

Disturbance in riparian areas of semiarid ecosystems involves complex interactions of pulsed hydrologic flows, herbivory, fire, climatic effects, and anthropogenic influences. We resampled riparian vegetation within ten 10-m × 100-m plots that were initially sampled in 1992 in 4 watersheds of the Snake Range, east central Nevada. Our finding of significantly lower coverage of grasses, forbs, and shrubs within plots in 2001 compared with 1992 was not consistent with the management decision to remove livestock grazing from the watersheds in 1999. Change over time in cover of life-forms or bare ground was not predicted by scat counts within plots in 2001. Cover results were also not well explained by variability between the 2 sampling periods in either density of native herbivores or annual precipitation. In contrast, Engelmann spruce ( Picea engelmannii ) exhibited reduced abundance at all but the highest-elevation plot in which it occurred in 1992, and the magnitude of change in abundance was strongly predicted by plot elevation. Abundance of white fir ( Abies concolor ) individuals increased while aspen ( Populus tremuloides ) individuals decreased at 4 of 5 sites where they were sympatric, and changes in abundance in the 2 species were negatively correlated across those sites. Utility of monitoring data to detect change over time and contribute to adaptive management will vary with sample size, observer bias, use of repeatable or published methods, and precision of measurements, among other factors.     

Arizona distribution of three Sonoran Desert anurans: Bufo retiformis, Gastrophryne olivacea , and Pternohyla fodiens

We surveyed historic collecting localities in south central Arizona during July, August, and September 1993-94 to determine the presence of 3 little-known Sonoran Desert anurans, Bufo retiformis, Gastrophryne olivacea, and Pternohyla fodiens . All 3 species were present at most historic localities visited under appropriate conditions (following rainfall in July and August). Pternohyla fodiens was restricted to San Simon Wash and associated tributaries in south central Pima County. Gastrophryne olivacea ranged from Vekol Valley in extreme southern Maricopa County south to the Mexican border, and southeast near Tucson and Nogales in Pima and Santa Cruz counties. Bufo retiformis occurred over the widest area, from southern Rainbow Valley in Maricopa County southwest to the vicinity of Organ Pipe Cactus National Monument, and southeast to the vicinity of Tucson and Sasabe in Pima County.     

Intrusion triggering of the 2010 Eyjafjallajökull explosive eruption

Gradual inflation of magma chambers often precedes eruptions at highly active volcanoes. During such eruptions, rapid deflation occurs as magma flows out and pressure is reduced. Less is known about the deformation style at moderately active volcanoes, such as Eyjafjallaj?kull, Iceland, where an explosive summit eruption of trachyandesite beginning on 14 April 2010 caused exceptional disruption to air traffic, closing airspace over much of Europe for days. This eruption was preceded by an effusive flank eruption of basalt from 20 March to 12 April 2010. The 2010 eruptions are the culmination of 18?years of intermittent volcanic unrest. Here we show that deformation associated with the eruptions was unusual because it did not relate to pressure changes within a single magma chamber. Deformation was rapid before the first eruption (>5?mm per day after 4 March), but negligible during it. Lack of distinct co-eruptive deflation indicates that the net volume of magma drained from shallow depth during this eruption was small; rather, magma flowed from considerable depth. Before the eruption, a ～0.05?km(3) magmatic intrusion grew over a period of three months, in a temporally and spatially complex manner, as revealed by GPS (Global Positioning System) geodetic measurements and interferometric analysis of satellite radar images. The second eruption occurred within the ice-capped caldera of the volcano, with explosivity amplified by magma-ice interaction. Gradual contraction of a source, distinct from the pre-eruptive inflation sources, is evident from geodetic data. Eyjafjallaj?kull's behaviour can be attributed to its off-rift setting with a 'cold' subsurface structure and limited magma at shallow depth, as may be typical for moderately active volcanoes. Clear signs of volcanic unrest signals over years to weeks may indicate reawakening of such volcanoes, whereas immediate short-term eruption precursors may be subtle and difficult to detect.