Modelling raindrop impact and splash erosion processes within a spatial cell: a stochastic approach

A new approach is proposed to simulate splash erosion on local soil surfaces. Without the effect of wind and other raindrops, the impact of free-falling raindrops was considered as an independent event from the stochastic viewpoint. The erosivity of a single raindrop depending on its kinetic energy was computed by an empirical relationship in which the kinetic energy was expressed as a power function of the equivalent diameter of the raindrop. An empirical linear function combining the kinetic energy and soil shear strength was used to estimate the impacted amount of soil particles by a single raindrop. Considering an ideal local soil surface with size of I m x I m, the expected number of received free-failing raindrops with different diameters per unit time was described by the combination of the raindrop size distribution function and the terminal velocity of raindrops. The total splash amount was seen as the sum of the impact amount by all raindrops in the rainfall event. The total splash amount per unit time was subdivided into three different components, including net splash amount, single impact amount and re-detachment amount. The re-detachment amount was obtained by a spatial geometric probability derived using the Poisson function in which overlapped impacted areas were considered. The net splash amount was defined as the mass of soil particles collected outside the splash dish. It was estimated by another spatial geometric probability in which the average splashed distance related to the median grain size of soil and effects of other impacted soil particles and other free-falling raindrops were considered. Splash experiments in artificial rainfall were carried out to validate the availability and accuracy of the model. Our simulated results suggested that the net splash amount and re-detachment amount were small parts of the total splash amount. Their proportions were 0.15% and 2.6%, respectively. The comparison of simulated data with measured data showed that this model could be applied to simulate the soil-splash process successfully and needed information of the rainfall intensity and original soil properties including initial bulk intensity, water content, median grain size and some empirical constants related to the soil surface shear strength, the raindrop size distribution function and the average splashed distance. Copyright (c) 2007 John Wiley & Sons, Ltd.

Wave breaking on turbulent energy budget in the ocean surface mixed layer

As an important physical process at the air-sea interface, wave movement and breaking have a significant effect on the ocean surface mixed layer (OSML). When breaking waves occur at the ocean surface, turbulent kinetic energy (TKE) is input downwards, and a sublayer is formed near the surface and turbulence vertical mixing is intensively enhanced. A one-dimensional ocean model including the Mellor-Yamada level 2.5 turbulence closure equations was employed in our research on variations in turbulent energy budget within OSML. The influence of wave breaking could be introduced into the model by modifying an existing surface boundary condition of the TKE equation and specifying its input. The vertical diffusion and dissipation of TKE were effectively enhanced in the sublayer when wave breaking was considered. Turbulent energy dissipated in the sublayer was about 92.0% of the total depth-integrated dissipated TKE, which is twice higher than that of non-wave breaking. The shear production of TKE decreased by 3.5% because the mean flow fields tended to be uniform due to wave-enhanced turbulent mixing. As a result, a new local equilibrium between diffusion and dissipation of TKE was reached in the wave-enhanced layer. Below the sublayer, the local equilibrium between shear production and dissipation of TKE agreed with the conclusion drawn from the classical law-of-the-wall (Craig and Banner, 1994).

Vertical structure and evolution of the Luzon Warm Eddy

Eddies are frequently observed in the northeastern South China Sea (SCS). However, there have been few studies on vertical structure and temporal-spatial evolution of these eddies. We analyzed the seasonal Luzon Warm Eddy (LWE) based on Argo float data and the merged data products of satellite altimeters of Topex/Poseidon, Jason-1 and European Research Satellites. The analysis shows that the LWE extends vertically to more than 500 m water depth, with a higher temperature anomaly of 5A degrees C and lower salinity anomaly of 0.5 near the thermocline. The current speeds of the LWE are stronger in its uppermost 200 m, with a maximum speed of 0.6 m/s. Sometimes the LWE incorporates mixed waters from the Kuroshio Current and the SCS, and thus has higher thermohaline characteristics than local marine waters. Time series of eddy kinematic parameters show that the radii and shape of the LWE vary during propagation, and its eddy kinetic energy follows a normal distribution. In addition, we used the empirical orthogonal function (EOF) here to analyze seasonal characteristics of the LWE. The results suggest that the LWE generally forms in July, intensifies in August and September, separates from the coast of Luzon in October and propagates westward, and weakens in December and disappears in February. The LWE's westward migration is approximately along 19A degrees N latitude from northwest of Luzon to southeast of Hainan, with a mean speed of 6.6 cm/s.

Optimal Body Size and Energy Expenditure during Winter: Why are voles smaller in declining populations?

Winter is energetically challenging for small herbivores because of greater energy requirements for thermogenesis at a time when little energy is available. We formulated a model predicting optimal wintering body size, accounting for the scaling of both energy expenditure and assimilation to body size, and the trade-off between survival benefits of a large size and avoiding survival costs of foraging. The model predicts that if the energy cost of maintaining a given body mass differs between environments, animals should be smaller in the more demanding environments, and there should be a negative correlation between body mass and daily energy expenditure (DEE) across environments. In contrast, if animals adjust their energy intake according to variation in survival costs of foraging, there should be a positive correlation between body mass and DEE. Decreasing temperature always increases equilibrium DEE, but optimal body mass may either increase or decrease in colder climates depending on the exact effects of temperature on mass-specific survival and energy demands. Measuring DEE with doubly labeled water on wintering Microtus agrestis at four field sites, we found that DEE was highest at the sites where voles were smallest despite a positive correlation between DEE and body mass within sites. This suggests that variation in wintering body mass between sites was due to variation in food quality/availability and not adjustments in foraging activity to varying risks of predation.

Fragmentation of metastable SF6−* ions with microsecond lifetimes in competition with autodetachment

Fragmentation of metastable SF6-* ions formed in low energy electron attachment to SF₆has been investigated. The dissociation reaction SF6-*?SF5-+F has been observed ~ 1.5–3.4 µs and ~ 17–32 µs after electron attachment in a time-of-flight and a double focusing two sector field mass spectrometer, respectively. Metastable dissociation is observed with maximum intensity at ~ 0.3 eV between the SF6-* peak at zero and theSF5- peak at ~ 0.4 eV. The kinetic energy released in dissociation is low, with a most probable value of 18 meV. The lifetime of SF6-* decreases as the electron energy increases, but it is not possible to fit this decrease with statistical Rice–Ramsperger–Kassel/quasiequilibrium theory. Metastable dissociation of SF6-* appears to compete with autodetachment of the electron at all electron energies.

A spectroscopically normal type Ic supernova from a very massive progenitor

We present observations of the Type Ic supernova (SN Ic) 2011bm spanning a period of about one year. The data establish that SN 2011bm is a spectroscopically normal SN Ic with moderately low ejecta velocities and with a very slow spectroscopic and photometric evolution (more than twice as slow as SN 1998bw). The Pan-STARRS1 retrospective detection shows that the rise time from explosion to peak was 40 days in the R band. Through an analysis of the light curve and the spectral sequence, we estimate a kinetic energy of 7-17 foe and a total ejected mass of 7-17 Mo, 5-10 Mo of which is oxygen and 0.6-0.7 Mo is 56Ni. The physical parameters obtained for SN 2011bm suggest that its progenitor was a massive star of initial mass 30-50 Mo. The profile of the forbidden oxygen lines in the nebular spectra show no evidence of a bi-polar geometry in the ejected material.

Planning, Devolution and the Territorialisation of Wind Energy in the UK

The decarbonisation of energy systems draw a new set of stakeholders into debates over energy generation, engage a complex set of social, political, economic and environmental processes and impact at a wide range of geographical scales, including local landscape changes, national energy markets and regional infrastructure investment. This paper focusses on a particular geographic scale, that of the regions/nations of the UK (Scotland, Wales, Northern Ireland), who have been operating under devolved arrangements since the late 1990s, coinciding with the mass deployment of wind energy. The devolved administrations of the UK possess an asymmetrical set of competencies over energy policy, yet also host the majority of the UK wind resource. This context provides a useful way to consider the different ways in which geographies of "territory" are reflected in energy governance, such through techno-rational assessments of demand or infrastructure investment, but also through new spatially-defined institutions that seek to develop their own energy future, using limited regulatory competencies. By focussing on the way the devolved administrations have used their responsibilities for planning over the last decade this paper will assess the way in which the spatial politics of wind energy is giving rise to renewed forms of territorialisation of natural resources. In so doing, we aim to contribute to clarifying the questions raised by Hodson and Marvin (2013) on whether low carbon futures will reinforce or challenge dominant ways of organising relationships between the nation-state, regions, energy systems and the environment.

Nonconservative dynamics in long atomic wires

The effect of nonconservative current-induced forces on the ions in a defect-free metallic nanowire is investigated using both steady-state calculations and dynamical simulations. Nonconservative forces were found to have a major influence on the ion dynamics in these systems, but their role in increasing the kinetic energy of the ions decreases with increasing system length. The results illustrate the importance of nonconservative effects in short nanowires and the scaling of these effects with system size. The dependence on bias and ion mass can be understood with the help of a simple pen and paper model. This material highlights the benefit of simple preliminary steady-state calculations in anticipating aspects of brute-force dynamical simulations, and provides rule of thumb criteria for the design of stable quantum wires.

Early ultraviolet emission in the Type Ia supernova LSQ12gdj: No evidence for ongoing shock interaction

We present photospheric-phase observations of LSQ12gdj, a slowly declining, UV-bright Type Ia supernova. Classified well before maximum light, LSQ12gdj has extinction-corrected absolute magnitude MB = -19.8, and pre-maximum spectroscopic evolution similar to SN 1991T and the super-Chandrasekhar-mass SN 2007if. We use ultraviolet photometry from Swift, ground-based optical photometry, and corrections from a near-infrared photometric template to construct the bolometric (1600-23 800 Å) light curve out to 45 d past B-band maximum light. We estimate that LSQ12gdj produced 0.96 ± 0.07 M· of 56Ni, with an ejected mass near or slightly above the Chandrasekhar mass. As much as 27 per cent of the flux at the earliest observed phases, and 17 per cent at maximum light, is emitted bluewards of 3300 Å. The absence of excess luminosity at late times, the cutoff of the spectral energy distribution bluewards of 3000 Å and the absence of narrow line emission and strong Na I D absorption all argue against a significant contribution from ongoing shock interaction. However, ~10 per cent of LSQ12gdj's luminosity near maximum light could be produced by the release of trapped radiation, including kinetic energy thermalized during a brief interaction with a compact, hydrogen-poor envelope (radius <1013 cm) shortly after explosion; such an envelope arises generically in double-degenerate merger scenarios.

SN 2010ay is a Luminous and Broad-lined Type Ic Supernova within a Low-metallicity Host Galaxy

We report on our serendipitous pre-discovery detection and follow-up observations of the broad-lined Type Ic supernova (SN Ic) 2010ay at z = 0.067 imaged by the Pan-STARRS1 3π survey just ~4 days after explosion. The supernova (SN) had a peak luminosity, MR ≈ -20.2 mag, significantly more luminous than known GRB-SNe and one of the most luminous SNe Ib/c ever discovered. The absorption velocity of SN 2010ay is v Si ≈ 19 × 103 km s-1 at ~40 days after explosion, 2-5 times higher than other broad-lined SNe and similar to the GRB-SN 2010bh at comparable epochs. Moreover, the velocity declines ~2 times slower than other SNe Ic-BL and GRB-SNe. Assuming that the optical emission is powered by radioactive decay, the peak magnitude implies the synthesis of an unusually large mass of 56Ni, M Ni = 0.9 M ⊙. Applying scaling relations to the light curve, we estimate a total ejecta mass, M ej ≈ 4.7 M ⊙, and total kinetic energy, EK ≈ 11 × 1051 erg. The ratio of M Ni to M ej is ~2 times as large for SN 2010ay as typical GRB-SNe and may suggest an additional energy reservoir. The metallicity (log (O/H)PP04 + 12 = 8.19) of the explosion site within the host galaxy places SN 2010ay in the low-metallicity regime populated by GRB-SNe, and ~0.5(0.2) dex lower than that typically measured for the host environments of normal (broad-lined) SNe Ic. We constrain any gamma-ray emission with E γ ~ 1048 erg. We therefore rule out the association of a relativistic outflow like those that accompanied SN 1998bw and traditional long-duration gamma-ray bursts (GRBs), but we place less-stringent constraints on a weak afterglow like that seen from XRF 060218. If this SN did not harbor a GRB, these observations challenge the importance of progenitor metallicity for the production of relativistic ejecta and suggest that other parameters also play a key role.

Fragmentation of CD+ induced by intense ultrashort laser pulses

The fragmentation of CD+ in intense ultrashort laser pulses was investigated using a coincidence three-dimensional momentum imaging technique improved by employing both transverse and longitudinal electric fields. This allowed clear separation of all fragmentation channels and the determination of the kinetic energy release down to nearly zero, for a molecule with significant mass asymmetry. The most probable dissociation pathways for the two lowest dissociation limits, C+ + D and C+ D+, were identified for both 22-fs, 798-nm and 50-fs, 392-nm pulses. Curiously, the charge asymmetric dissociation of CD2+ was not observed for 392-nm photons, even though it was clearly visible for the fundamental 798 nm at the same peak intensity.

Lower resting energy expenditure and fat oxidation in Native American and Hispanic infants born to mothers with diabetes

OBJECTIVE: To determine whether exposure to diabetes in utero affects resting energy expenditure (REE) and fuel oxidation in infants.

STUDY DESIGN: At 35 ± 5 days after birth, body composition and REE were measured in full-term offspring of Native American and Hispanic women with either well-controlled diabetes (13 girls, 11 boys) or normal healthy pregnancies (18 girls, 17 boys).

RESULTS: Control of dysglycemia during gestation in the women with diabetes mellitus met current clinical standards, shown by average glycated hemoglobin (5.9 ± 0.2%; 40.6 ± 2.3 mmol/mol). Infant body mass (offspring of women with diabetes: 4.78 ± 0.13, control offspring: 4.56 ± 0.08 kg) and body fatness (offspring of women with diabetes: 25.2 ± 0.6, control offspring: 24.2 ± 0.5 %) did not differ between groups. REE, adjusted for lean body mass, was 14% lower in offspring of women with diabetes (41.7 ± 2.3 kJ/h) than control offspring (48.6 ± 2.0, P = .025). Fat oxidation was 26% lower in offspring of women with diabetes (0.54 ± 0.05 g/h) than control offspring (0.76 ± 0.04, P < .01) but carbohydrate oxidation did not differ. Thus, fat oxidation accounted for a lower fraction of REE in the offspring of women with diabetes (49 ± 4%) than control offspring (60 ± 3%, P = .022). Mothers with diabetes were older and had higher prepregnancy body mass index than control mothers.

CONCLUSIONS: Well-controlled maternal diabetes did not significantly affect body mass or composition of offspring at 1-month old. However, infants with mothers with diabetes had reduced REE and fat oxidation, which could contribute to adiposity and future disease risk. Further studies are needed to assess the impact differences in age and higher prepregnancy body mass index.

SN 2011fu: a type IIb supernova with a luminous double-peaked light curve

We present optical and near-infrared observations of the type IIb supernova (SN) 2011fu from a few days to similar to 300 d after explosion. The SN presents a double-peaked light curve (LC) similar to that of SN 1993J, although more luminous and with a longer cooling phase after the primary peak. The spectral evolution is also similar to SN 1993J's, with hydrogen dominating the spectra to similar to 40 d, then helium gaining strength, and nebular emission lines appearing from similar to 60 d post-explosion. The velocities derived from the P-Cygni absorptions are overall similar to those of other type IIb SNe. We have found a strong similarity between the oxygen and magnesium line profiles at late times, which suggests that these lines are forming at the same location within the ejecta. The hydrodynamical modelling of the pseudo-bolometric LC and the observed photospheric velocities suggest that SN 2011fu was the explosion of an extended star (R similar to 450 R-circle dot), in which 1.3 x 10(51) erg of kinetic energy were released and 0.15 M-circle dot of Ni-56 were synthesized. In addition, a better reproduction of the observed early pseudo-bolometric LC is achieved if a more massive H-rich envelope than for other type IIb SNe is considered (0.3 M-circle dot). The hydrodynamical modelling of the LC and the comparison of our late-time spectra with nebular spectral models for type IIb SNe, point to a progenitor for SN 2011fu with a Zero Age Main Sequence (ZAMS) mass of 13-18 M-circle dot.

Length matters:Keeping atomic wires in check

Dynamical effects of non-conservative forces in long, defect free atomic wires are investigated. Current flow through these wires is simulated and we find that during the initial transient, the kinetic energies of the ions are contained in a small number of phonon modes, closely clustered in frequency. These phonon modes correspond to the waterwheel modes determined from preliminary static calculations. The static calculations allow one to predict the appearance of non-conservative effects in advance of the more expensive real-time simulations. The ion kinetic energy redistributes across the band as non-conservative forces reach a steady state with electronic factional forces. The typical ion kinetic energy is found to decrease with system length, increase with atomic mass, and its dependence on bias, mass and length is supported with a pen and paper model. This paper highlights the importance of non-conservative forces in current carrying devices and provides criteria for the design of stable atomic wires.

Tidal Energy Resource Characterization in Alberni Inlet, B.C.

Senior thesis written for Oceanography 444