Dry Friction due to Adsorbed Molecules

Using an adiabatic approximation method, which searches for Tomlinson model-like instabilities for a simple but still realistic model for two crystalline surfaces in the extremely light contact limit, with mobile molecules present at the interface, sliding relative to each other, we are able to account for the virtually universal occurrence of "dry friction." The model makes important predictions for the dependence of friction on the strength of the interaction of each surface with the mobile molecules.Comment: four pages of latex, figure provide

A review of the design and assessment model of the Skills Challenge Certificate, and its place within the Welsh Baccalaureate

In January 2017, Wavehill, in collaboration with the University College London (UCL) Institute of Education (IOE), was commissioned by Qualifications Wales to undertake a review of the Skills Challenge Certificate (SCC) qualification and its place within the Welsh Baccalaureate (Welsh Bacc). Dr Caroline Daly (Reader in Education, IOE and Honorary Visiting Professor Cardiff University) undertook a detailed analysis of the SCC design by reviewing programme specifications, delivery handbooks, design principles, the administration handbook, the code of practice and Qualifications Wales’ (2016) Review of the implementation of the new Welsh Baccalaureate from September 2015. Dr Caroline Daly is the lead author on the desk-based review of the SCC. The review of documents was supplemented by interviews with key stakeholders, including the authors of the Qualifications Wales’ initial review (2016) of the Welsh Bacc and senior managers at the awarding body, WJEC. These interviews were used for reference to seek clarification about the SCC design and assessment model to inform the ongoing review of the documentation and refine questions for the focus groups. To enrich the evidence base, a programme of fieldwork was developed to sample a number of schools and Further Education (FE) colleges across Wales. The fieldwork engaged with learners and teachers through focus groups (learners) and interviews (teachers). The sample was constructed in discussion with Qualifications Wales and was designed to include the voices of learners and teachers from a variety of centres across Wales that deliver the Welsh Bacc (the methodology is discussed in section 3). The findings from the desk-based review, the learner focus groups and the teacher interviews are brought together in the Conclusions and Recommendations at the end of the report

Nitric oxide affects short-term olfactory memory in the antennal lobe of Manduca sexta

Nitric oxide (NO) is thought to play an important neuromodulatory role in olfaction. We are using the hawkmoth Manduca sexta to investigate the function of NO signaling in the antennal lobe (AL; the primary olfactory network in invertebrates). We have found previously that NO is present at baseline levels, dramatically increases in response to odor stimulation, and alters the electrophysiology of AL neurons. It is unclear, however, how these effects contribute to common features of olfactory systems such as olfactory learning and memory, odor detection and odor discrimination. In this study, we used chemical detection and a behavioral approach to further examine the function of NO in the AL. We found that basal levels of NO fluctuate with the daily light cycle, being higher during the nocturnal active period. NO also appears to be necessary for short-term olfactory memory. NO does not appear to affect odor detection, odor discrimination between dissimilar odorants, or learning acquisition. These findings suggest a modulatory role for NO in the timing of olfactory-guided behaviors

Hurricane Matthew in 2100: effects of extreme sea level rise scenarios on a highly valued coastal area (Palm Beach, FL, USA)

Sea-level rise represents a severe hazard for populations living within low-elevation coastal zones and is already largely affecting coastal communities worldwide. As sea level continues to rise following unabated greenhouse gas emissions, the exposure of coastal communities to inundation and erosion will increase exponentially. These impacts will be further magnified under extreme storm conditions. In this paper, we focus on one of the most valuable coastal real estate markets globally (Palm Beach, FL). We use XBeach, an open-source hydro and morphodynamic model, to assess the impact of a major tropical cyclone (Hurricane Matthew, 2016) under three different sea-level scenarios. The first scenario (modern sea level) serves as a baseline against which other model runs are evaluated. The other two runs use different 2100 sea-level projections, localized to the study site: (i) IPCC RCP 8.5 (0.83 m by 2100) and (ii) same as (i), but including enhanced Antarctic ice loss (1.62 m by 2100). Our results show that the effective doubling of future sea level under heightened Antarctic ice loss amplifies flow velocity and wave height, leading to a 46% increase in eroded beach volume and the overtopping of coastal protection structures. This further exacerbates the vulnerability of coastal properties on the island, leading to significant increases in parcel inundation

Improved Constraints on the Acceleration History of the Universe and the Properties of the Dark Energy

We extend and apply a model-independent analysis method developed earlier by Daly & Djorgovski to new samples of supernova standard candles, radio galaxy and cluster standard rulers, and use it to constrain physical properties of the dark energy as functions of redshift. Similar results are obtained for the radio galaxy and supernova data sets. The first and second derivatives of the distance are compared directly with predictions in a standard model based on General Relativity. The good agreement indicates that General Relativity provides an accurate description of the data on look-back time scales of about ten billion years. The first and second derivatives are combined to obtain the acceleration parameter, assuming only the validity of the Robertson-Walker metric, independent of a theory of gravity and of the physical nature of the dark energy. The acceleration of the universe at the current epoch is indicated by the analysis. The effect of non-zero space curvature on q(z) is explored. We solve for the pressure, energy density, equation of state, and potential and kinetic energy of the dark energy as functions of redshift assuming that General Relativity is the correct theory of gravity, and the results indicate that a cosmological constant in a spatially flat universe provides a good description of each of these quantities over the redshift range from zero to about one. We define a new function, the dark energy indicator, in terms of the first and second derivatives of the coordinate distance and show how this can be used to measure deviations of w from -1 and to obtain a new and independent measure of Omega.Comment: 46 pages, submitted for publicatio

Cosmological Studies with Radio Galaxies and Supernovae

Physical sizes of extended radio galaxies can be employed as a cosmological "standard ruler", using a previously developed method. Eleven new radio galaxies are added to our previous sample of nineteen sources, forming a sample of thirty objects with redshifts between 0 and 1.8. This sample of radio galaxies are used to obtain the best fit cosmological parameters in a quintessence model in a spatially flat universe, a cosmological constant model that allows for non-zero space curvature, and a rolling scalar field model in a spatially flat universe. Results obtained with radio galaxies are compared with those obtained with different supernova samples, and with combined radio galaxy and supernova samples. Results obtained with different samples are consistent, suggesting that neither method is seriously affected by systematic errors. Best fit radio galaxy and supernovae model parameters determined in the different cosmological models are nearly identical, and are used to determine dimensionless coordinate distances to supernovae and radio galaxies, and distance moduli to the radio galaxies. The distance moduli to the radio galaxies can be combined with supernovae samples to increase the number of sources, particularly high-redshift sources, in the samples. The constraints obtained here with the combined radio galaxy plus supernovae data set in the rolling scalar field model are quite strong. The best fit parameter values suggest a value of omega is less than about 0.35, and the model parameter alpha is close to zero; that is, a cosmological constant provides a good description of the data. We also obtain new constraints on the physics of engines that power the large-scale radio emission.Comment: 32 pages. Accepted for publication in the Astrophysical Journa

Contextualizing Professional Responsibility: A New Curriculum for a New Century

Daly et al assert that professional responsibility has matured as a subject matter to the point where a new genre of courses should join the pervasive method and the traditional survey course. The new age of professaional responsibility will reflect intellectual maturity through the introduction of contextual course that are designed to nurture the development of reflective ethical judgment

Crater Morphometry and Scaling in Coarse, Rubble-Like Targets: Insights from Impact Experiments

Spacecraft images reveal that the asteroids Itokawa, Ryugu, and Bennu are covered with coarse, boulder-rich material [13]. Impactors that collide with these bodies encounter a target with extreme physical heterogeneity. Other bodies can also possess significant physical heterogeneity (e.g., megaregolith, layering, etc.). Such heterogeneities establish free surfaces and impedance contrasts that can affect shock propagation and attenuation. Therefore, such heterogeneities may also affect crater formation and excavation [4], melt generation [57] and crater scaling [4]. As described by [8,9], the extent to which target heterogeneity affects crater formation likely depends on how the length scale, d, of the heterogeneity (e.g., boulder size on a rubble-pile asteroid) compares to the width of the shock, w, generated by impact. Here we further test this hypothesis using impact experiments across a broad range of impact velocities and target grain sizes to systematically vary the ratio between the width of the shock and the diameter of target grains

Temperature, Salinity, Turbidity, and Light Attenuation in the Great Bay Estuary System 1974-1978

The purpose of this study was to evaluate the temperature, salinity, turbidity, and light attenuation characteristics throughout the Great Bay Estuary System during 1974-1978. In contrast to previous studies within the Estuary (Norall and Mathieson, 1976, Daly and Mathieson, in preparation) only physical parameters were measured and they were measured at more frequent (1 meter) vertical intervals. Such information is important to future coastal zone management and to ultimate understanding of the estuarine ecosystem. The Great Bay Estuary System is a dynamic habitat with pronounced spatial and temporal variations of hydrographic factors. Accordingly, locations furthest from the coast experience the most freshwater influence and the least oceanic influence. In some sites there are salt wedges resulting in physical variability with depth. Seasonality is apparent in the amount of freshwater input, detrital input, and temperature variation. The volume of freshwater entering the Estuary is greatest during spring runoff when precipitation is low and evaporation high. As the volume of water in the Estuary changes tidal currents, the amount of fresh water input may affect turbidity and light attenuation, as well as salinity. The present study evaluates three sources of physical variation in the Estuary: 1) location, 2) season, and 3) depth. Data collected between July, 1974 and June, 1978, along with some simple statistical interpretations, are presented herein