Quantifying the Fragility of Galactic Disks in Minor Mergers

We perform fully self-consistent stellar dynamical simulations of the accretion of a companion ("satellite") galaxy by a large disk galaxy to investigate the interaction between the disk, halo, and satellite components of the system during a merger. Our fiducial encounter begins with a satellite in a prograde, circular orbit inclined thirty degrees with respect to the disk plane at a galactocentric distance of six disk scalelengths. The satellite's mass is 10% of the disk's mass and its half-mass radius is about 1.3 kpc. The system is modelled with 500 000 particles, sufficient to mitigate numerical relaxation noise over the merging time. The satellite sinks in only ~1 Gyr and a core containing ~45% of its initial mass reaches the centre of the disk. With so much of the satellite's mass remaining intact, the disk sustains significant damage as the satellite passes through. At the solar circle we find that the disk thickens ~60%, the velocity dispersions increase by \Delta\mbox{\boldmath\sigma} \simeq (10,8,8) km/s to $(\sigma_R, \sigma_\phi, \sigma_z) \simeq (48, 42, 38)$ km/s, and the asymmetric drift is unchanged at ~18 km/s. Although the disk is not destroyed by these events (hence "minor" mergers), its final state resembles a disk galaxy of earlier Hubble type than its initial state, thicker and hotter, with the satellite's core enhancing the bulge. Thus minor mergers continue to be a promising mechanism for driving galaxy evolution.Comment: LaTeX with AASTeX macros; text only. For PostScript with figures embedded, go to http://www.ucolick.org/~iwalker/ss

Secondary flow deflection in the lee of transverse dunes with implications for dune morphodynamics and migration

Measurements of lee-side airflow response from an extensive array of meteorological instruments combined with smoke and flow streamer visualization is used to examine the development and morphodynamic significance of the lee-side separation vortex over closely spaced transverse dune ridges. A differential deflection mechanism is presented that explains the three-dimensional pattern of lee-side airflow structure for a variety of incident flow angles. These flow patterns produce reversed, along-dune, and deflected surface flow vectors in the lee that are inferred to result in net ‘lateral diversion’ of sand transport over one dune wavelength for incident angles as small as 10° from crest-transverse (i.e. 80° from the crest line). This lateral displacement increases markedly with incident flow angle when expressed as the absolute value of the total deflection in degrees. Reversed and multi-directional flow occurs for incident angles between 90° and 50°. These results document the three-dimensional nature of flow and sand transport over transverse dunes and provide empirical evidence for an oblique migration model. Copyright © 2013 John Wiley & Sons, Ltd

Summary Data for Cross-Shore Transects (Winter 2016-Summer 2020) - Humboldt Coastal Resiliency Project and Climate Ready Project

Sea level rise and/or extreme events are capable of causing excessive erosion on the beaches and foredunes that line the outer edges of the barriers enclosing Humboldt Bay and the Eel River delta within the Eureka littoral cell. Erosion of these protective barriers threatens the natural and cultural resources and infrastructure behind them in two significant estuaries. A major goal of the Climate Ready Project and the Humboldt Coastal Resilience Project was to quantify present day beach-dune morphodynamics, which could then be used to model the impacts of sea level rise and extreme events. For this purpose, a total of 73 cross-shore transects were established along the littoral cell. Elevation and vegetation data collected on transects will be used in a quantitative model to predict beach, dune and barrier responses to sea level rise and extreme events. The purpose of this report is to present raw data in the form of graphs of elevation change along transects as the basis of qualitative observations of response during the period of data collection, 2016-2020. The primary audience is property owners within the study site. Conclusions of this report are based on qualitative analysis and may change when modeling is complete

The economic cost of weeds in dryland cotton production systems of Australia

Economic losses and costs associated with weeds in dryland cotton production are important, both for growers and for industry bodies when making decisions about research priorities and research and development funding. A survey was conducted to provide information on weed types, control strategies and estimated costs to growers. We used information from the survey to estimate conventional financial losses due to weeds, and as a basis for evaluating aggregate economic (society) impacts. An economic surplus model was used to estimate the aggregate societal impact of weeds for three production regions in north-eastern Australia. The annual economic costs associated with weeds were estimated to be $41 million, and the on-farm financial costs were$25 million. While these are past (sunk) costs, and based on a total removal of weeds, the approach outlined here can be used to begin evaluating likely future returns from technologies or management improvements for different agricultural problems.Weeds, Dryland Cotton, and Economics, Crop Production/Industries, Environmental Economics and Policy,

Wearing a Bicycle Helmet Can Increase Risk Taking and Sensation Seeking in Adults.

Humans adapt their risk-taking behavior on the basis of perceptions of safety; this risk-compensation phenomenon is typified by people taking increased risks when using protective equipment. Existing studies have looked at people who know they are using safety equipment and have specifically focused on changes in behaviors for which that equipment might reduce risk. Here, we demonstrated that risk taking increases in people who are not explicitly aware they are wearing protective equipment; furthermore, this happens for behaviors that could not be made safer by that equipment. In a controlled study in which a helmet, compared with a baseball cap, was used as the head mount for an eye tracker, participants scored significantly higher on laboratory measures of both risk taking and sensation seeking. This happened despite there being no risk for the helmet to ameliorate and despite it being introduced purely as an eye tracker. The results suggest that unconscious activation of safety-related concepts primes globally increased risk propensity

Comparison of dimethyl sulfoxide treated highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) electrodes for use in indium tin oxide-free organic electronic photovoltaic devices

Indium tin oxide (ITO)-free organic photovoltaic (OPV) devices were fabricated using highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) as the transparent conductive electrode (TCE). The intrinsic conductivity of the PEDOT:PSS films was improved by two different dimethyl sulfoxide (DMSO) treatments – (i) DMSO was added directly to the PEDOT:PSS solution (PEDOT:PSSADD) and (ii) a pre-formed PEDOT:PSS film was immersed in DMSO (PEDOT:PSSIMM). X-ray photoelectron spectroscopy (XPS) and conductive atomic force microscopy (CAFM) studies showed a large amount of PSS was removed from the PEDOT:PSSIMM electrode surface. OPV devices based on a poly(3-hexylthiophene):[6,6]-phenyl-C61-butyric acid methyl ester (P3HT:PCBM) bulk hetrojunction showed that the PEDOT:PSSIMM electrode out-performed the PEDOT:PSSADD electrode, primarily due to an increase in short circuit current density from 6.62 mA cm−2 to 7.15 mA cm−2. The results highlight the importance of optimising the treatment of PEDOT:PSS electrodes and demonstrate their potential as an alternative TCE for rapid processing and low-cost OPV and other organic electronic devices

Dynamic restoration and the impact of native versus invasive vegetation on coastal foredune morphodynamics, Lanphere Dunes, California, USA

The Lanphere Dunes, part of the Humboldt Bay National Wildlife Refuge, has been the focus of foredune restoration efforts since the 1980s. Efforts have centred around removal of an invasive European beach grass species, Ammophila arenaria, introduced in the early 1900s to stabilize the dunes to protect landward communities from coastal flooding and storm surges. Despite effectively stabilizing the foredune, A. arenaria forms monotypic vegetation stands, with highly dense roots, rhizomes, and above-ground biomass that can lead to pronounced scarping of the seaward slope, alongshore steering of wind and sediment, a lack of landward transfer of sand, and a steeper, more peaked profile. Effective foredune restoration must consider the coupled interactions between dominant plant type and the geomorphic processes that influence dune form. A 5 ha reach of recently restored foredune was monitored biannually with terrestrial laser scanner and uncrewed aerial systems platforms between 2015 and 2021 to characterize the impacts of dynamic restoration on foredune form and resiliency. This reach included two control plots: (1) native, non-restored and (2) invasive, and three restored plots revegetated with native species: (3) a native grass (Elymus mollis), (4) a low-lying herb and subshrub assemblage, and (5) a mixture of the native grass, herbs, and subshrubs. After five growing seasons, restored plots exhibited distinct geomorphic and sediment budget differences. Natively vegetated plots recovered from extensive scarping 2 years faster than the invasive plot. Restored plots saw foredune height (0.5–0.7 m) and width increase, landward extension (1 m) while maintaining a similar seaward position, and positive lee-slope sediment budgets that exceeded both control plots. These results suggest that the native vegetation plots allowed increased landward sand transport across the foredune, and increased the capacity of the foredune to recover more quickly following dune scarping

The Electronic and Superconducting Properties of Oxygen-Ordered MgB2 compounds of the form Mg2B3Ox

Possible candidates for the Mg2B3Ox nanostructures observed in bulk of polycrystalline MgB2 (Ref.1) have been studied using a combination of Z-contrast imaging, electron energy loss spectroscopy (EELS) and first-principles calculations. The electronic structures, phonon modes, and electron phonon coupling parameters are calculated for two oxygen-ordered MgB2 compounds of composition Mg2B3O and Mg2B3O2, and compared with those of MgB2. We find that the density of states for both Mg2B3Ox structures show very good agreement with EELS, indicating that they are excellent candidates to explain the observed coherent oxygen precipitates. Incorporation of oxygen reduces the transition temperature and gives calculated TC values of 18.3 K and 1.6 K for Mg2B3O and Mg2B3O2, respectively.Comment: Submitted to PR

Adolescent moral judgement: A study of UK secondary school pupils

Despite a recent world-wide upsurge of academic interest in moral and character education, little is known about pupils’ character development in schools, especially in the UK context. The authors used a version of the Intermediate Concept Measure for Adolescents, involving dilemmas, to assess an important component of character—moral judgement—among 4053 pupils aged 14–15. Data were generated in 33 UK schools of varying types between February 2013 and June 2014. Results showed that compared with US samples, the pupils’ scores were, on average, low, suggestive of tendencies towards ‘self-interest’, ‘not getting involved’ and ‘conformity/loyalty to friends’. Judgements varied by subscales assessing ‘action’ and ‘justification’ choices; pupils more successfully identified good actions than good justifications, but generally struggled more to successfully identify poor actions and poor justifications. Highest scores were for a dilemma emphasising ‘self-discipline’ and lowest for ‘honesty’, with ‘courage’ in between. Overall average results were significantly and positively associated with being female, having (and practising) a religion and doing specific extra-curricular activities. Differences in schools were also noted, although the kinds of school (e.g. public/private, religious/secular) were unrelated to student scores