Interannual variability in net accumulation on the Greenland Ice Sheet: Observations and implications for mass balance measurements

This is the published version, also available here: http://dx.doi.org/10.1029/1998JD200082.Nine 24-year accumulation records from the Summit region in central Greenland are analyzed to separate the effects of spatial noise and interannual fluctuations on the variability in each core. The study shows that both processes are equally important, with standard deviations of 25 mm water equivalent per year and 24 mm water equivalent per year, respectively. A comparison with estimates of surface roughness based on high-resolution laser altimetry of the surface indicates that in the studied region the spatial noise can be reliably estimated from surface roughness. The response of the ice-sheet surface to the interannual fluctuations can be estimated using a simple zero-dimensional ice-sheet response model. For the Summit region of central Greenland, a change in surface elevation of ∼20 mm water equivalent per year measured over a 5-year period, can be attributed with 95% confidence to a trend in climate. This probability decreases rapidly as the observation period is shortened. For intervals greater than ∼5 year, the probability depends only weakly on the measurement interval. This suggests an optimum spacing of ∼5 years between repeat elevation measurements

Are we overusing IVF?

Peer reviewedPublisher PD

Loop quantum gravity induced modifications to particle dynamics

The construction of effective Hamiltonians arising from Loop Quantum Gravity and incorporating Planck scale corrections to the dynamics of photons and spin 1/2 particles is summarized. The imposition of strict bounds upon some parameters of the model using already existing experimental data is also reviewed.Comment: 9 pages, 0 figures, talk presented at the X Mexican School of Particles and Fields, latex, aipproc style 6x

Superheating and solid-liquid phase coexistence in nanoparticles with non-melting surfaces

We present a phenomenological model of melting in nanoparticles with facets that are only partially wet by their liquid phase. We show that in this model, as the solid nanoparticle seeks to avoid coexistence with the liquid, the microcanonical melting temperature can exceed the bulk melting point, and that the onset of coexistence is a first-order transition. We show that these results are consistent with molecular dynamics simulations of aluminum nanoparticles which remain solid above the bulk melting temperature.Comment: 8 pages, 5 figure

Controls on advance of tidewater glaciers: results from numerical modeling applied to Columbia Glacier

This is the published version, also available here: http://dx.doi.org/10.1029/2006JF000551.A one-dimensional numerical ice flow model is used to study the advance of a tidewater glacier into deep water. Starting with ice-free conditions, the model simulates glacier growth at higher elevations followed by advance on land to the head of the fjord. Once the terminus reaches a bed below sea level, calving is initiated. A series of simulations was carried out with various boundary conditions and parameterizations of the annual mass balance. The results suggest that irrespective of the calving criterion and accumulation rate in the catchment area, it is impossible for the glacier terminus to advance into deeper water (>300 m water depth) unless sedimentation at the glacier front is included. The advance of Columbia Glacier, Alaska, is reproduced by the model by including “conveyor belt” recycling of subglacial sediment and the formation of a sediment bank at the glacier terminus. Results indicate slow advance through the deep fjord and faster advance in shallow waters approaching the terminal moraine shoal and the mouth of the fjord

Surface defreezing of glasses

A glass surface may still flow below the bulk glass transition temperature, where the underlying bulk is frozen. Assuming the existence at T=T* of a bulk thermodynamical glass transition, we show that the glass-vapor interface is generally wetted by a liquid layer of thickness ~ -ln(T*-T) when T--> T*. Contrary to standard surface melting of crystals however, the integrated value of the diffusivity across the interface remains finite for T-->T*. Difference in shape induced by bulk and by surface flow is discussed as a possible means of experimental detection of surface defreezing.Comment: five pages, three figure

Classification of Quantitative Light-Induced Fluorescence Images Using Convolutional Neural Network

Images are an important data source for diagnosis and treatment of oral diseases. The manual classification of images may lead to misdiagnosis or mistreatment due to subjective errors. In this paper an image classification model based on Convolutional Neural Network is applied to Quantitative Light-induced Fluorescence images. The deep neural network outperforms other state of the art shallow classification models in predicting labels derived from three different dental plaque assessment scores. The model directly benefits from multi-channel representation of the images resulting in improved performance when, besides the Red colour channel, additional Green and Blue colour channels are used.Comment: Full version of ICANN 2017 submissio

Mass-luminosity relation and pulsational properties of Wolf-Rayet stars

Evolution of Population I stars with initial masses from 70M_\odot to 130M_\odot is considered under various assumptions on the mass loss rate \dot M. The mass-luminosity relation of W-R stars is shown to be most sensitive to the mass loss rate during the helium burning phase \dot M_{3\alpha}. Together with the mass-luminosity relation obtained for all evolutionary sequences several more exact relations are determined for the constant ratio f_{3\alpha}=\dot M/\dot M_{3\alpha} with 0.5 \le f_{3\alpha} \le 3. Evolutionary models of W-R stars were used as initial conditions in hydrodynamic computations of radial nonlinear stellar oscillations. The oscillation amplitude is larger in W-R stars with smaller initial mass or with lower mass loss rate due to higher surface abundances of carbon and oxygen. In the evolving W-R star the oscillation amplitude decreases with decreasing stellar mass M and for M < 10M_\odot the sufficiently small nonlinear effects allow us to calculate the integral of the mechanical work W done over the pulsation cycle in each mass zone of the hydrodynamical model. The only positive maximum on the radial dependence of W is in the layers with temperature of T\sim 2e5K where oscillations are excited by the iron Z--bump kappa-mechanism. Radial oscillations of W-R stars with mass of M > 10M_\odot are shown to be also excited by the kappa-mechanism but the instability driving zone is at the bottom of the envelope and pulsation motions exist in the form of nonlinear running waves propagating outward from the inner layers of the envelope.Comment: 15 pages, 10 figures, submitted to Astronomy Letter

Surface roughness on the Greenland Ice Sheet from airborne laser altimetry

This is the published version, also available here: http://dx.doi.org/10.1029/1998GL900041.High resolution airborne laser altimetry is used to determine the small-scale surface relief in central Greenland and estimate the contribution from spatial noise to stratigraphic records. The standard deviation of the surface roughness is 1.6 cm water equivalent, corresponding to a standard deviation of annual layer thickness of 2.3 cm we. This estimate agrees with an independent assessment of the spatial variability (2.5 cm we) based on nine shallow ice cores. The agreement suggests that the statistical nature of the surface in central Greenland remains unchanged throughout the year. By conducting airborne altimetry around proposed drilling sites, the expected noise level in the core can be evaluated and sites selected where this level is lowest

Developing an Intervention and Evaluation Model of Outdoor Therapy for Employee Burnout: Unraveling the Interplay Between Context, Processes, and Outcomes

BACKGROUND Burnout is a major societal issue adversely affecting employees' health and performance, which over time results in high sick leave costs for organizations. Traditional rehabilitation therapies show suboptimal effects on reducing burnout and the return-to-work process. Based on the health-promoting effects of nature, taking clients outdoors into nature is increasingly being used as a complementary approach to traditional therapies, and evidence of their effectiveness is growing. Theories explaining how the combination of general psychological support and outdoor-specific elements can trigger the rehabilitation process in outdoor therapy are often lacking, however, impeding its systematic research. AIM The study aims to develop an intervention and evaluation model for outdoor therapy to understand and empirically evaluate whether and how such an outdoor intervention may work for rehabilitation after burnout. METHODOLOGICAL APPROACH We build on the exemplary case of an outdoor intervention for rehabilitation after burnout, developed by outdoor clinical psychologists in Netherlands. We combined the generic context, process, and outcome evaluation model and the burnout recovery model as an overarching deductive frame. We then inductively specified the intervention and evaluation model of outdoor therapy, building on the following qualitative data: semi-structured interviews with outdoor clinical psychologists and former clients; a content analysis of the intervention protocol; and reflective meetings with the intervention developers and health promotion experts. RESULTS We identified six key outdoor intervention elements: (1) physical activity; (2) reconnecting body and mind; (3) nature metaphors; (4) creating relationships; (5) observing natural interactions; and (6) experiential learning. The results further showed that the implementation of these elements may facilitate the rehabilitation process after burnout in which proximal, intermediate, and distal outcomes emerge. Finally, the results suggested that this implementation process depends on the context of the therapist (e.g., number of clients per day), therapy (e.g., privacy issues), and of the clients (e.g., affinity to nature). CONCLUSION The intervention and evaluation model for outdoor therapy shows how key outdoor intervention elements may contribute to the rehabilitation process after burnout. However, our model needs to be further tested among a larger group of clients to empirically evaluate whether and how outdoor therapy can support rehabilitation