Monitoring and Analysis of Frozen Debris Lobes, Phase I

INE/AUTC 12.2

MIXING IT UP: THE IMPACT OF EPISODIC INTROGRESSION ON THE EVOLUTION OF HIGH-LATITUDE MESOCARNIVORES

At high latitudes, climatic oscillations have triggered repeated episodes of organismal divergence by geographically isolating populations. For terrestrial species, extended isolation in glacial refugia – ice-free regions that enable terrestrial species persistence through glacial maxima – is hypothesized to stimulate allopatric divergence. Alternatively, upon glacial recession, divergent populations expanded from independent glacial refugia and often contacted other diverging populations. In the absence of reproductive isolating mechanisms, this biogeographic process may trigger hybridization and ultimately, gene flow between divergent taxa. My dissertation research aims to understand how these episodic periods of isolation and contact have impacted the evolution of high latitude species. To understand the role of episodic isolation and gene flow on the evolution and diversification of high-latitude species, my dissertation integrates genetic, genomic, and morphometric characters across multiple high-latitude mesocarnivore mammals within the hyper-diverse Mustelidae family. Overall, I identified substantial cryptic diversity in the Arctic and highlight the complementary roles of glacial and interglacial cycles in the evolution and structuring of high latitude biota

Identification of burning and extinguishing behaviour in spray flames with spark ignition

The Gaussian Mixture Model (GMM) is used to analyse Direct Numerical Simulation results for sprays which are ignited using spark ignition. The variables considered in the GMM are the reaction progress variable and its dissipation. It is found that a case which sustained a self-propagating flame produces a burning branch, where a strong flame front is developed, and an extinguishing branch, which contains droplets which are offset from the main spark energy. These branches are distinctly observed through the various clusters that are formed by the GMM. In contrast, cases which ignite but subsequently undergo global extinction do not produce clusters that are distinctly from the burning branch or extinguishing branch near the flame kernel. However, the clustering does display a strong extinguishing branch near the leading edge of the flame front

L1551NE - Discovery of a Binary Companion

L1551NE is a very young (class 0 or I) low-mass protostar located close to the well-studied L1551 IRS5. We present here evidence, from 1.3mm continuum interferometric observations at ~1'' resolution, for a binary companion to L1551NE. The companion, whose 1.3mm flux density is ~1/3 that of the primary component, is located 1.43'' (~230 A.U. at 160pc) to the southeast. The millimeterwave emission from the primary component may have been just barely resolved, with deconvolved size ~0.82"x0.70" (~131x112 A.U.). The companion emission was unresolved (<100 A.U.). The pair is embedded within a flattened circum-binary envelope of size ~5.4'' x 2.3'' (~860 x 370 A.U.). The masses of the three components (i.e. from the cicumstellar material of the primary star and its companion, and the envelope) are approximately 0.044, 0.014 and 0.023 Mo respectively.Comment: 8 pages, 1 figur

7. Habitat Use and Home Range of Eastern Box Turtle (Terrapene carolina carolina) in North Georgia Piedmont

The Eastern Box Turtle (Terrapene carolina carolina) is a terrestrial species native to the eastern United States. Eastern Box Turtles are experiencing range-wide population decline and are classified as vulnerable by the International Union for the Conservation of Nature. Despite this, little research has been conducted regarding home range and habitat use in the Southeastern US. Therefore, since May 2013, we have conducted a radiotelemetry study to investigate factors that influence Box Turtle movement, habitat use, and survival in the Northeastern Piedmont region of Georgia. The study site is composed of mixed hardwood-pine uplands primarily comprised of oaks and maples, mesic and upland areas dominated by Chinese privet (Ligustrum sinense), beaver-created wetland, and maintained utility line areas. Our research includes 21 radio-transmitted turtles that are tracked on foot by homing 1-2 times a week. From spring 2013 to winter 2017, an average of 74 radiolocations (range: 6 to 166) per turtle were collected. Home ranges (100% minimum convex polygon) varied from less than 1 to over 6 ha. Radiotracked turtles primarily used mixed-upland areas and areas dominated by Chinese privet. The assessment of habitat use and home ranges will continue throughout 2017 with tracking and further data analysis. Keywords: Terrapene carolina carolina, radiotelemetry, home range, habitat use, Ligustrum sinens

Branching principles of animal and plant networks identified by combining extensive data, machine learning, and modeling

Branching in vascular networks and in overall organismic form is one of the most common and ancient features of multicellular plants, fungi, and animals. By combining machine-learning techniques with new theory that relates vascular form to metabolic function, we enable novel classification of diverse branching networks--mouse lung, human head and torso, angiosperm and gymnosperm plants. We find that ratios of limb radii--which dictate essential biologic functions related to resource transport and supply--are best at distinguishing branching networks. We also show how variation in vascular and branching geometry persists despite observing a convergent relationship across organisms for how metabolic rate depends on body mass.Comment: 55 pages, 8 figures, 8 table

Robust energy harvesting from walking vibrations by means of nonlinear cantilever beams

In the present work we examine how mechanical nonlinearity can be appropriately utilized to achieve strong robustness of performance in an energy harvesting setting. More specifically, for energy harvesting applications, a great challenge is the uncertain character of the excitation. The combination of this uncertainty with the narrow range of good performance for linear oscillators creates the need for more robust designs that adapt to a wider range of excitation signals. A typical application of this kind is energy harvesting from walking vibrations. Depending on the particular characteristics of the person that walks as well as on the pace of walking, the excitation signal obtains completely different forms. In the present work we study a nonlinear spring mechanism that is composed of a cantilever wrapping around a curved surface as it deflects. While for the free cantilever, the force acting on the free tip depends linearly on the tip displacement, the utilization of a contact surface with the appropriate distribution of curvature leads to essentially nonlinear dependence between the tip displacement and the acting force. The studied nonlinear mechanism has favorable mechanical properties such as low frictional losses, minimal moving parts, and a rugged design that can withstand excessive loads. Through numerical simulations we illustrate that by utilizing this essentially nonlinear element in a 2 degrees-of-freedom (DOF) system, we obtain strongly nonlinear energy transfers between the modes of the system. We illustrate that this nonlinear behavior is associated with strong robustness over three radically different excitation signals that correspond to different walking paces. To validate the strong robustness properties of the 2DOF nonlinear system, we perform a direct parameter optimization for 1DOF and 2DOF linear systems as well as for a class of 1DOF and 2DOF systems with nonlinear springs similar to that of the cubic spring that are physically realized by the cantilever–surface mechanism. The optimization results show that the 2DOF nonlinear system presents the best average performance when the excitation signals have three possible forms. Moreover, we observe that while for the linear systems the optimal performance is obtained for small values of the electromagnetic damping, for the 2DOF nonlinear system optimal performance is achieved for large values of damping. This feature is of particular importance for the system׳s robustness to parasitic damping.Massachusetts Institute of Technology. Naval Engineering Education Center. (Grant 3002883706)National Science Foundation (U.S.). Graduate Research Fellowship Program (Grant 1122374)MIT Energy Initiativ