Adaptations to tree-gouging in the anterior masticatory apparatus of marmosets (callithrix) [abstract]

Although all genera of Callitrichinae engage in exudativory to some degree, marmosets (Callithrix, Cebuella) take advantage of exudates to the greatest extent. To facilitate exudate feeding, marmosets use their anterior teeth to gouge holes in bark and actively stimulate gum flow. As such, their anterior mandibular teethpossess specialized adaptations such as thickened labial enamel. Marmosets alsoshow masticatory features that facilitate increased gape, but do not appear to generate relatively large bite forces during gouging. However, even without increased bite force the anterior teeth of gougers likely experience different loading patternscompared to non-gouging platyrrhines. Specifically, one might expect that theanterior teeth and symphysis of marmosets are adapted to accommodate relatively high stresses linked to dissipating forces from yield-resistant and tough tree barks. This study uses histological data from thin- sectioned teeth, microCT data of jaws and teeth, and macroscale tests of simulated symphyseal loads to compare the micro- and macro-architecture of the anterior masticatory apparatus in Callithrix and Saguinus (as well as the outgroup Saimiri). Callithrix differs from the other genera in that its canine enamel possesses a much higher degree of decussation, and its anterior tooth roots are larger relative to alveolar bone volume. However, simulated jaw loading suggests a reduced ability to withstand external forces in the marmoset symphysis. The contrast between increased load-resistance ability in the anterior dentition versus relatively reduced symphyseal strength suggests both a potentially complex loading environment during gouging and a mosaic pattern of dentofacial adaptations to this derived biting behavior

Coastal road asset management: Dealing with uncertainty using quantitative erosion monitoring and modelling

The A183 is an essential transportation link in the northeast UK that joins coastal areas from South Shields to Sunderland. The route runs through the hinterland of Marsden Bay and concerns have been raised about the proximity of the road to the eroding cliff line. The Shoreline Management Plan (Lane and Guthrie, 2007) sets out the overarching management policy in the area and, based on the analyses of historic map data, uses projected coastal cliff retreat rates of 0.1 – 0.2 m a-1, although more recent investigations have suggested the rates may be nearer 0.04 – 0.1 m a-1. Quantitative data on the true rates and nature of cliff erosion are scarce and asset management decisions typically use the higher rate of 0.2 m a-1 when considering the potential impact on road operations and lifespan in order to account for uncertainty and future sea-level rise; which is additionally used to accelerate the predicted rates of retreat. Consequently, an enhanced high order estimate of cliff erosion rates has restricted the serviceability of the A183 to within 20 – 50 years, and there are three areas (pinch points) of particular concern where the close proximity of the cliff line threatens the safe operation of the road. This approach and the data it uses suggest that significant and potentially costly decisions may soon be required to ensure the viability of this vital transport corridor. Set against the context of assumed high cliff erosion rates, and further predicted increases to this metric, this work presents the results of a re-evaluation of existing map and aerial imagery data that highlights the typically high uncertainty associated with historic map data. The errors often exceed the changes being detected in rock cliffs, producing contradictory results and variability in processing and interpretation that restricts the reliability of the data used in current policy decisions. Using a significance-based analysis, questions are raised about how appropriate it is to reduce a three-dimensional recession process down to a single linear retreat. To provide a more appropriate and accurate assessment of the erosion occurring here we present the results of a monitoring approach of the Marsden Bay site using three-dimensional survey analyses to improve understanding of cliff failures at the site and ultimately to aid policy decisions

Decoding Complex Erosion Responses for the Mitigation of Coastal Rockfall Hazards Using Repeat Terrestrial LiDAR

A key factor limiting our understanding of rock slope behavior and associated geohazards is the interaction between internal and external system controls on the nature, rates, and timing of rockfall activity. We use high-resolution, monthly terrestrial light detection and ranging (LiDAR) surveys over a 2 year monitoring period to quantify rockfall patterns across a 0.6 km-long (15.3 × 103 m2) section of a limestone rock cliff on the northeast coast of England, where uncertainty in rates of change threaten the effective planning and operational management of a key coastal cliff top road. Internal system controls, such as cliff material characteristics and foreshore geometry, dictate rockfall characteristics and background patterns of activity and demonstrate that layer-specific analyses of rockfall inventories and sequencing patterns are essential to better understand the timing and nature of rockfall risks. The influence of external environmental controls, notably storm activity, is also evaluated, and increased storminess corresponds to detectable rises in both total and mean rockfall volume and the volumetric contribution of large (>10 m3) rockfalls at the cliff top during these periods. Transient convergence of the cumulative magnitude–frequency power law scaling exponent (ɑ) during high magnitude events signals a uniform erosion response across the wider cliff system that applies to all lithologies. The tracking of rockfall distribution metrics from repeat terrestrial LiDAR in this way demonstrably improves the ability to identify, monitor, and forecast short-term variations in rockfall hazards, and, as such, provides a powerful new approach for mitigating the threats and impacts of coastal erosion

Ruthenium-Catalyzed Mono-Selective C–H Methylation and d₃-Methylation of Arenes

[Image: see text] Site-selective installation of C–Me bonds remains a powerful and sought-after tool to alter the chemical and pharmacological properties of a molecule. Direct C–H functionalization provides an attractive means of achieving this transformation. Such protocols, however, typically utilize harsh conditions and hazardous methylating agents with poor applicability toward late-stage functionalization. Furthermore, highly monoselective methylation protocols remain scarce. Herein, we report an efficient monoselective, directed ortho-methylation of arenes using N,N,N-trimethylanilinium salts as noncarcinogenic, bench-stable methylating agents. We extend this protocol to d(3)-methylation in addition to the late-stage functionalization of pharmaceutically active compounds. Detailed kinetic studies indicate the rate-limiting in situ formation of MeI is integral to the observed reactivity

Episodic Antarctic Shelf Intrusions of Circumpolar Deep Water via Canyons

The structure of the Antarctic Slope Current at the continental shelf is crucial in governing the poleward transport of warm water. Canyons on the continental slope may provide a pathway for warm water to cross the slope current and intrude onto the continental shelf underneath ice shelves, which can increase rates of ice shelf melting, leading to reduced buttressing of ice shelves, accelerating glacial flow and hence increased sea level rise. Observations and modelling studies of the Antarctic Slope Current and cross-shelf warm water intrusions are limited, particularly in the East Antarctica region. To explore this topic, an idealised configuration of the Antarctic Slope Current is developed, using an eddy-resolving isopycnal model that emulates the dynamics and topography of the East Antarctic sector. Warm water intrusions via canyons are found to occur in discrete episodes, with large onshore flow induced by eddies. The episodic nature of cross-shelf warm water transport is demonstrated, with canyon width playing a key role in modulating cross-shelf exchanges; warm water transport through narrower canyons is more irregular than transport through wider canyons. The episodic cross-shelf transport is driven by a cycle of rising and falling rates of eddy generation in the Antarctic Slope Current, a variability intrinsic to the slope current that can be explained without any temporal variability in external forcings. Improved understanding of the intrinsic variability of warm water intrusions can help guide future observational and modelling studies in the analysis of eddy impacts on Antarctic shelf circulation

Chemical tagging can work: Identification of stellar phase-space structures purely by chemical-abundance similarity

Chemical tagging promises to use detailed abundance measurements to identify spatially separated stars that were in fact born together (in the same molecular cloud), long ago. This idea has not yielded much practical success, presumably because of the noise and incompleteness in chemical-abundance measurements. We have succeeded in substantially improving spectroscopic measurements with The Cannon, which has now delivered 15 individual abundances for ~100,000 stars observed as part of the APOGEE spectroscopic survey, with precisions around 0.04 dex. We test the chemical-tagging hypothesis by looking at clusters in abundance space and confirming that they are clustered in phase space. We identify (by the k-means algorithm) overdensities of stars in the 15-dimensional chemical-abundance space delivered by The Cannon, and plot the associated stars in phase space. We use only abundance-space information (no positional information) to identify stellar groups. We find that clusters in abundance space are indeed clusters in phase space. We recover some known phase-space clusters and find other interesting structures. This is the first-ever project to identify phase-space structures at survey-scale by blind search purely in abundance space; it verifies the precision of the abundance measurements delivered by The Cannon; the prospects for future data sets appear very good.Comment: accepted for publication in the Ap

Response of the Southern Ocean Overturning Circulation to Extreme Southern Annular Mode Conditions

The positive trend of the Southern Annular Mode (SAM) will impact the Southern Ocean's role in Earth's climate; however, the details of the Southern Ocean's response remain uncertain. We introduce a methodology to examine the influence of SAM on the Southern Ocean and apply this method to a global ocean-sea ice model run at three resolutions (1◦, (1/4)◦, and (1/10)◦). Our methodology drives perturbation simulations with realistic atmospheric forcing of extreme SAM conditions. The thermal response agrees with previous studies; positive SAM perturbations warm the upper ocean north of the wind speed maximum and cool it to the south, with the opposite response for negative SAM. The overturning circulation exhibits a rapid response that increases/decreases for positive/negative SAM perturbations and is insensitive to model resolution. The longer-term adjustment of the overturning circulation, however, depends on the representation of eddies, and is faster at higher resolutions.Department of Education and Training | Australian Research Council (ARC). Grant Number: LP16010007

Resonant exciton excitation photoluminescence and dynamics in a GaAs/AlAs multiple quantum well with internal electric field

The stability of excitons with large oscillator strengths at room temperature has been of great significance in device applications. In this paper, we report the effects of the ultrafast dissociation of excitons confined in a quantum well on optical characteristics. The photoluminescence spectra show components of higher energy than the excitation energy and a nonlinear increment of the intensity. Furthermore, the spectrally resolved pump–probe signals at the exciton energies elucidate the change in the exciton position. These results indicate the importance of the exciton stability in optical devices, in particular emission type, including terahertz wave, based on excitons