Life without the Beach: Projected Sea Level Rise and its Impact on Barrier Islands Along the East Coast, USA

As climate change is becoming a global issue, the impact of sea level rise is increasingly becoming a threat to humans, wildlife, infrastructure, and ecosystems. To evaluate the effects of sea level rise on barrier islands and coastal regions, we studied future projections of sea level rise at Ocean City and Assateague Island, Maryland. We hypothesize that the sea levels at Assateague and Ocean City will have different beach profiles, and will show different levels of flooding through the Representative Concentration Pathways (RCP) simulations. We measured beach profiles at four locations, two at Ocean City and two at Assateague Island, to view the current beach profiles and found that Ocean City reveals a smaller average change in elevation compared to Assateague. We also used a LiDAR Digital Elevation Model (DEM) of Ocean City and Assateague Island to run RCP 2.6, RCP 4.5, and RCP 8.5 simulations using GIS to represent the Intergovernmental Panel on Climate Change (IPCC) projected sea level rise for the year 2100. We found that Ocean City has higher predicted percentages of flooded land but smaller areas of flooded land compared to Assateague. These results indicate that significant areas of both Ocean City and Assateague Island will be flooded by 2100 regardless of which RCP simulation might be true. However, it is projected that the RCP 2.6 simulation is an underestimation of potential flooding and the future will more closely resemble the RCP 8.5 simulation if drastic precautions are not taken now. This will severely impact ecosystems, economies, and human life

Dynamical cluster disruption and its implications for multiple population models in the E-MOSAICS simulations

© 2018 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. Several models have been advanced to explain the multiple stellar populations observed in globular clusters (GCs). Most models necessitate a large initial population of unenriched stars that provide the pollution for an enriched population, and which are subsequently lost from the cluster. This scenario generally requires clusters to lose > 90 per cent of their birth mass. We use a suite of 25 cosmological zoom-in simulations of present-day Milky Way mass galaxies from the E-MOSAICS project to study whether dynamical disruption by evaporation and tidal shocking provides the necessary mass-loss. We find that GCs with present-day masses M > 105M⊙were only 2-4 times more massive at birth, in conflict with the requirements of the proposed models. This factor correlates weakly with metallicity, gas pressure at birth, or galactocentric radius, but increases towards lower GC masses. To reconcile our results with observational data, either an unphysically steep cluster mass-size relation must be assumed, or the initial enriched fractions must be similar to their present values. We provide the required relation between the initial enriched fraction and cluster mass. Dynamical cluster mass-loss cannot reproduce the high observed enriched fractions nor their trend with cluster mass

The E-MOSAICS project: simulating the formation and co-evolution of galaxies and their star cluster populations

We introduce the MOdelling Star cluster population Assembly In Cosmological Simulations within EAGLE (E-MOSAICS) project. E-MOSAICS incorporates models describing the formation, evolution, and disruption of star clusters into the EAGLE galaxy formation simulations, enabling the examination of the co-evolution of star clusters and their host galaxies in a fully cosmological context. A fraction of the star formation rate of dense gas is assumed to yield a cluster population; this fraction and the population’s initial properties are governed by the physical properties of the natal gas. The subsequent evolution and disruption of the entire cluster population are followed accounting for two-body relaxation, stellar evolution, and gravitational shocks induced by the local tidal field. This introductory paper presents a detailed description of the model and initial results from a suite of 10 simulations of ∼L galaxies with disc-like morphologies atz = 0. The simulations broadly reproduce key observed characteristics of young star clusters and globular clusters (GCs), without invoking separate formation mechanisms for each population. The simulated GCs are the surviving population of massive clusters formed at early epochs (z 1–2), when the characteristic pressures and surface densities of star-forming gas were significantly higher than observed in local galaxies. We examine the influence of the star formation and assembly histories of galaxies on their cluster populations, finding that (at similar present-day mass) earlier-forming galaxies foster a more massive and disruption-resilient cluster population, while galaxies with late mergers are capable of forming massive clusters even at late cosmic epochs. We find that the phenomenological treatment of interstellar gas in EAGLE precludes the accurate modelling of cluster disruption in low-density environments, but infer that simulations incorporating an explicitly modelled cold interstellar gas phase will overcome this shortcoming

Vibrational resonance, allostery, and activation in rhodopsin-like G protein-coupled receptors

G protein-coupled receptors are a large family of membrane proteins activated by a variety of structurally diverse ligands making them highly adaptable signaling molecules. Despite recent advances in the structural biology of this protein family, the mechanism by which ligands induce allosteric changes in protein structure and dynamics for its signaling function remains a mystery. Here, we propose the use of terahertz spectroscopy combined with molecular dynamics simulation and protein evolutionary network modeling to address the mechanism of activation by directly probing the concerted fluctuations of retinal ligand and transmembrane helices in rhodopsin. This approach allows us to examine the role of conformational heterogeneity in the selection and stabilization of specific signaling pathways in the photo-activation of the receptor. We demonstrate that ligand-induced shifts in the conformational equilibrium prompt vibrational resonances in the protein structure that link the dynamics of conserved interactions with fluctuations of the active-state ligand. The connection of vibrational modes creates an allosteric association of coupled fluctuations that forms a coherent signaling pathway from the receptor ligand-binding pocket to the G-protein activation region. Our evolutionary analysis of rhodopsin-like GPCRs suggest that specific allosteric sites play a pivotal role in activating structural fluctuations that allosterically modulate functional signals

Temperature dependence of the electron spin g factor in GaAs

The temperature dependence of the electron spin $g$ factor in GaAs is investigated experimentally and theoretically. Experimentally, the $g$ factor was measured using time-resolved Faraday rotation due to Larmor precession of electron spins in the temperature range between 4.5 K and 190 K. The experiment shows an almost linear increase of the $g$ value with the temperature. This result is in good agreement with other measurements based on photoluminescence quantum beats and time-resolved Kerr rotation up to room temperature. The experimental data are described theoretically taking into account a diminishing fundamental energy gap in GaAs due to lattice thermal dilatation and nonparabolicity of the conduction band calculated using a five-level kp model. At higher temperatures electrons populate higher Landau levels and the average $g$ factor is obtained from a summation over many levels. A very good description of the experimental data is obtained indicating that the observed increase of the spin $g$ factor with the temperature is predominantly due to band's nonparabolicity.Comment: 6 pages 4 figure

Can a connectionist model explain the processing of regularly and irregularly inflected words in German as L1 and L2?

The connectionist model is a prevailing model of the structure and functioning of the cognitive system of the processing of morphology. According to this model, the morphology of regularly and irregularly inflected words (e.g., verb participles and noun plurals) is processed in the same cognitive network. A validation of the connectionist model of the processing of morphology in German as L2 has yet to be achieved. To investigate L2-specific aspects, we compared a group of L1 speakers of German with speakers of German as L2. L2 and L1 speakers of German were assigned to their respective group by their reaction times in picture naming prior to the central task. The reaction times in the lexical decision task of verb participles and noun plurals were largely consistent with the assumption of the connectionist model. Interestingly, speakers of German as L2 showed a specific advantage for irregular compared with regular verb participles

Revisiting Politics in Political CSR: How coercive and deliberative dynamics operate through institutional work in a Colombian company

This article analyses the political dynamics taking place within a Colombian supplier company during the implementation of a client’s global Corporate Social Responsibility (CSR) programme, which radically transformed the local understandings of the supplier’s social responsibilities. We distinguish two forms of politics in political CSR – coercive and deliberative politics – and examine how they unfold through lower-level managers’ institutional work. Our longitudinal case study identifies four types of institutional work, which combine into three political configurations – irreconcilable politics, complementary politics and aligned deliberative politics – resulting in the hybridization of explicit and implicit CSR. By analysing how local managers from emerging countries and at the bottom of the supply chain cope with the new political role of MNCs, we expand the political microfoundations of CSR and highlight the interactive and political nature of institutional work aimed at addressing major societal challenges

The origin of the 'blue tilt' of globular cluster populations in the E-MOSAICS simulations

The metal-poor sub-population of globular cluster (GC) systems exhibits a correlation between the GC average colour and luminosity, especially in those systems associated with massive elliptical galaxies. More luminous (more massive) GCs are typically redder and hence more metal-rich. This 'blue tilt' is often interpreted as a mass-metallicity relation stemming from GC self-enrichment, whereby more massive GCs retain a greater fraction of the enriched gas ejected by their evolving stars, fostering the formation of more metal-rich secondary generations. We examine the E-MOSAICS simulations of the formation and evolution of galaxies and their GC populations, and find that their GCs exhibit a colour-luminosity relation similar to that observed in local galaxies, without the need to invoke mass-dependent self-enrichment. We find that the blue tilt is most appropriately interpreted as a dearth of massive, metal-poor GCs: the formation of massive GCs requires high interstellar gas surface densities, conditions that are most commonly fostered by the most massive, and hence most metal rich, galaxies, at the peak epoch of GC formation. The blue tilt is therefore a consequence of the intimate coupling between the small-scale physics of GC formation and the evolving properties of interstellar gas hosted by hierarchically-assembling galaxies

Spin-orbit terms in multi-subband electron systems: A bridge between bulk and two-dimensional Hamiltonians

We analyze the spin-orbit terms in multi-subband quasi-two-dimensional electron systems, and how they descend from the bulk Hamiltonian of the conduction band. Measurements of spin-orbit terms in one subband alone are shown to give incomplete information on the spin-orbit Hamiltonian of the system. They should be complemented by measurements of inter-subband spin-orbit matrix elements. Tuning electron energy levels with a quantizing magnetic field is proposed as an experimental approach to this problem.Comment: Typos noticed in the published version have been corrected and several references added. Published in the special issue of Semiconductors in memory of V.I. Pere