162 research outputs found
VU GeoNews 2006
No full textNewsletter of the Vanderbilt Department of Earth and Environmental Sciences 2006"Geology" to "Earth and Environmental Sciences" -- Professor William G. Siesser Retires after 25 Years of Service at Vanderbilt -- Letter from the Chair / David Jon Furbish -- Brendan Bream Joins EES Faculty -- Students walk, new graduates arrive -- Steven Goodbred Joins EES Faculty -- Faculty activities: Len Alberstadt, John Ayers, Brendan Bream, David Furbish, Jonathan Gilligan, Steven Goodbred, Calvin Miller, Molly Miller, Kinzly Moore, Art Reesman, Kaye Savage, Bill Siesser, Dick Stearns -- Alumni news (perhaps dated by a year or so!)-- Simon Mudd: scholar, athlete, artist, 1st PhD -- Renovation of Teaching Laboratories.http://authorities.loc.gov/Department of Earth and Environmental Science
VU GeoNews 2003
No full textNewsletter of the Vanderbilt Geology Department 2003Tribute to Leonard Alberstadt -- Kaye Savage brings Environmental Geochemistry expertise to Geology faculty -- Letter from the Chair / David Jon Furbish -- Thomas Kalakay, Jonathan Gilligan and Kinzly Moore: key additions to Geology faculty -- Students walk, new graduates arrive -- Antarctica provides clues to ancient freshwater ecosystems and polar climates -- Hot spots: moving or fixed? -- Demystifying the history of China's Dabie Mountains -- Students present research at GSA -- Under the volcano: probing magmatic plumbing systems -- Brett Beaulieu: news from Washington -- Staff changes -- New department facilities: analytical, computational and structural -- Vaughan Research Scholarship Program, NSF REU's and VUSRP provide Geology undergraduates with research experienceDepartment of Earth and Environmental Science
The Brickyard in 2020
No full textThe authors of this essay (David Furbish, Douglas Jerolmack and Rachel Glade) offer an updated view of the state of affairs in the brickyard described in B. K. Forscher’s popular 1963 allegorical letter to Science, “Chaos in the Brickyard.” It calls for a need to realign the research endeavor, institutions and incentives with changing values
Experimental censorship of bed load particle motions, and bias correction of the associated frequency distributions
No full textKnowledge of the statistical distributions of particle hop properties (distances, travel, and
rest times) enables a deeper understanding of bed load sediment transport. However, the measurement of
particle hops is prone to censorship: Since many hops cross the boundaries of a spatial-temporal
observation window, one knows that they exist but does not know how long they are. An option is to build
particle hop samples considering only the hops that are completely observed and excluding (censoring)
those observed only partially. Such a choice, however, biases the frequency distributions of the hop
properties. Moreover, censorship acts in both space and time, and a hop censored in time will also not
contribute to a sample of hop lengths, and vice versa. Time censorship similarly applies to particle rest
times. This paper presents a theoretical formulation of censorship that leads to nonparametric bias
corrections recovering estimates of values of the underlying distributions of hop distance, travel time,
and rest time up to sampling window dimensions. We illustrate the occurrence and consequences of
experimental censorship, and the benefit of applying the bias corrections, for both synthetic and laboratory
samples of particle hops. The corrections reasonably recover the relative proportions of frequency
distributions represented by the data up to the sampling dimensions and improve the estimates of the
first two moments of particle hop properties. Recommendations are given regarding how the size of an
observation window may be chosen to reduce the bias to below some prescribed value, if the forms of the
underlying distributions are known
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Maine tort law.
No full textThis comprehensive treatise on Maine tort law is the ultimate source for civil litigators in Maine. The treatise summarizes the legal requirements of virtually every cause of action based in tort in Maine and provides a uniquely valuable reference for the practitioner seeking to prosecute or defend every type of tort claim recognized in Maine. by Jack H. Simmons (Author), Donald N. Zillman (Author), Robert H. Furbish (Author)
Influence of chemical denudation on hillslope morphology
No full text[1] Models of hillslope evolution involving diffusion-like sediment transport are conventionally presented as an equation in which the changes in land-surface elevation or soil thickness are balanced by the divergence of soil transport and tectonic uplift, soil production, or both. These models typically do not include the loss or gain of mass in hillslope soils due to processes of chemical weathering and deposition. We formulate a more general depth-integrated equation for the conservation of soil mass on a hillslope that includes a term representing chemical deposition or denudation. This general depth-integrated equation is then simplified to determine the one-dimensional form of a steady state hillslope which experiences both mechanical and chemical denudation. The differences in morphology between hillslopes only experiencing diffusion-like mechanical sediment transport and hillslopes experiencing both diffusion-like mechanical sediment transport and chemical denudation are explored. Under the conditions of a downslope increase in local soil lowering rate due to chemical weathering the hillslope profile will depart from the parabolic shape predicted by models that incorporate only linear diffusion-like mechanical sediment transport. In addition, hillslopes that experience both chemica
Particle energy partitioning and transverse diffusion during rarefied travel on an experimental hillslope
No full textRecent theoretical and experimental work (Furbish et al., 2020a, 2020b) indicates that rarefied particle motions on rough hillslope surfaces are controlled by the balance between gravitational heating of particles due to conversion of potential to kinetic energy and frictional cooling of the particles due to collisions with the surface. Here we elaborate how particle energy is partitioned between kinetic, rotational, and frictional forms during downslope travel using measurements of particle travel distances on a laboratory-scale hillslope, supplemented with high-speed imaging of drop-impact-rebound experiments. The drop-impact-rebound experiments indicate that particle shape has a dominant role in energy conversion during impact with a surface. Relative to spherical and natural rounded particles, angular particles give greater variability in rebound behavior resulting in more effective conversion of translational to rotational energy. The effects of particle shape on energy conversion are especially pronounced on a sloping sand-roughened surface. Angular particles travel shorter distances downslope than rounded particles though travel distance data for both groups are well fit by generalized Pareto distributions. Moreover, particle-surface collisions during downslope motion lead to a transverse random-walk behavior and transverse particle dispersion. Transverse spreading increases with surface slope as there is more available energy to be partitioned into the downslope or transverse directions during collision due to increased gravitational heating. Rounded particles exhibit greater transverse dispersion than angular particles, as less energy is lost during collision with the surface. Because the experimental surface is relatively smooth, this random-walk behavior represents a top-down control on the randomization of particle trajectories due to particle shape, which is in contrast to a bottom-up control on randomization of particle trajectories associated with motions over rough surfaces. Importantly, transverse particle diffusion during downslope motion may contribute to a cross-slope particle flux, and likely contributes to topographic smoothing of irregular hillslope surfaces such as scree slopes
On experimental censorship of particle hops in bed-load transport
No full textObservation of incomplete particle hops in imaging-based experiments with bed-load transport does not just occur with hops that are longer than an area of observation. Even short hops can be in fact incompletely measured if they cross the boundaries of the focus area. Experimental censorship biases the statistical distribution and moments of bed-load particle hops. This paper presents: a theoretical quantification of an expected effect of experimental censorship; based on this quantification, a method to correct the statistical distribution of hop lengths; an application of the method to experimental data. Applying the correction leads to significantly different values of the mean hop length, compensating the biasing effect of censorship. By contrast, nothing can be done for experimental truncation that is associated with hops longer than an applied area of observation. Experimental truncation must be avoided a priori, by appropriate design of the measurement method
A Probabilistic, Biologically Informed Model of Desert Shrub Population Dynamics with the Granularity Appropriate for Geomorphic Simulations (Matlab Code)
No full textThis Matlab code simulates the spatiotemporal dynamics of a desert shrub population. The development of the code was motivated by the need to link rain-splash induced mound building at the shrub scale with the unfolding 'biological play' occurring on a hillside. The code therefore was designed for subsequent coupling with physics based models of sediment transport. Its spatial scale (~10s-100s m) spans many individual shrubs (~10-100 cm) and its temporal scale (~100s-1000s years) spans multiple shrub lifetimes (~10s-100s years). In addition to featuring a strong biophysical foundation (e.g., basic aspects of desert soil-water hydrology and population ecology such as shrub recruitment, growth, and mortality), the code mimics well-documented aspects of how desert shrub populations respond to changes in precipitation (e.g., productivity decreases with increasingly arid conditions and areal density declines during prolonged periods of drought). For supporting information about the conceptual and mathematical framework of the model as well as a description of its behaviors and potential use cases, please see Worman, 2010 and Worman and Furbish (2018)
Rainsplash induced mound development beneath desert shrubs: Modulations of sediment transport and storage, with implications for hillslope evolution
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