Coupling between a glacier and a soft bed: I. A relation between effective pressure and local shear stress determined from till elasticity

To predict the distribution of motion beneath glaciers on soft beds, the strength of the coupling between the ice and the bed and its variation with effective pressure must be known. A record of shear strain, acquired with a tiltmeter emplaced in till beneath Storglaciären, Sweden, indicates that fluctuations in water pressure cause variations in the local shear stress on the bed and that the bed deforms elastically in response to these variations. To estimate the shear stress from the elastic component of the total shear strain, the shear modulus of the till was measured in relaxation tests conducted in the laboratory with a ring-shear device. After accounting for the elastic compliance of the device, these tests yielded shear moduli of about 1000 and 1800 kPa at confining pressures of 85 and 280 kPa, respectively. These values are comparable to those of other granular materials undergoing recoverable shear strains of the same magnitude. The local shear stress on the till, calculated by applying the measured shear moduli to the tilt record, scales with ? e 1.7, where P e is the effective pressure. This relation implies that as P e decreases at the ice/till interface, shear stresses on the till are reduced and concentrated elsewhere on the bed, perhaps where the till is absent or the glacier is frozen to the bed. When compared with the strength of the till determined from ring-shear tests, this relation also accounts for the lack of permanent deformation at depth in the bed during periods of low P e and indicates that most basal motion was by sliding or ploughing

Note: Thermal analog to atomic force microscopy force-displacement measurements for nanoscale interfacial contact resistance

Thermal diffusion measurements on polymethylmethacrylate-coated Si substrates using heated atomic force microscopy tips were performed to determine the contact resistance between an organic thin film and Si. The measurement methodology presented demonstrates how the thermal contrast signal obtained during a force-displacement ramp is used to quantify the resistance to heat transfer through an internal interface. The results also delineate the interrogation thickness beyond which thermal diffusion in the organic thin film is not affected appreciably by the underlying substrate

Current Collection to and Plasma Interaction with Femtosatellite- and CubeSat-Scale Electrodynamic Tether Subsystems

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97119/1/AIAA2012-5295.pd

Stratigraphy of Devonian-Mississippian rocks, northern Pinon Range, southwestern Elko County, Nevada

Online access for this thesis was created in part with support from the Institute of Museum and Library Services (IMLS) administered by the Nevada State Library, Archives and Public Records through the Library Services and Technology Act (LSTA). To obtain a high quality image or document please contact the DeLaMare Library at https://unr.libanswers.com/ or call: 775-784-6945.The stratigraphy of Devonian and Mississippian rocks found in the Northern Piñon Range of Elko County, Nevada, was studied. This study clarifies the differences in the Upper Devonian and Mississippian siliciclastics in the northern Piñon Range

Measuring Condensation Heat Transfer on Superhydrophobic Surfaces

Condensation heat transfer is significant in many applications such as desalination, energy conversion, atmospheric water harvesting, electronics cooling, and other high heat flux applications. However, condensate on the surface adds a thermal resistance that limits condensation rates. The rate of condensation heat transfer is inversely proportional to the diameter of the condensate drops. In industrial condensing systems, the resistance is minimized by removing the condensate via gravity or a vapor shear, but the minimum size of droplet removal is typically on the order of the capillary length of the condensate, about 2.7 mm for water

An Optical-based Aggregate Approach to Measuring Condensation Heat Transfer

Condensation heat transfer is significant in many applications such as such as desalination, energy conversion [1], atmospheric water harvesting [2, 3], electronics cooling, and other high heat flux applications [4]. However, condensate on the surface adds a thermal resistance that limits condensation rates. The rate of condensation heat transfer is inversely proportional to the diameter of the condensate drops [5]. In industrial condensing systems, the resistance is minimized by removing the condensate via gravity or a vapor shear, but the minimum size of droplet removal is typically on the order of the capillary length of the condensate, about 2.7 mm for water

Investigating Miniature Electrodynamic Tethers and Interaction with the Low Earth Orbit Plasma

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106509/1/AIAA2013-5391.pd

Investigating Miniaturized Electrodynamic Tethers for Picosatellites and Femtosatellites

Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/143110/1/1.A33629.pd

Electrochemical Glucose Sensors Enhanced by Methyl Viologen and Vertically Aligned Carbon Nanotube Channels

Free-standing, vertically aligned carbon nanotubes (VACNTs) were patterned into 16 µm diameter microchannel arrays for flow-through electrochemical glucose sensing. Non-enzymatic sensing of glucose was achieved by the chemical reaction of glucose with methyl viologen (MV) at an elevated temperature and pH (0.1 M NaOH), followed by the electrochemical reaction of reduced-MV with the VACNT surface. The MV sensor required no functionalization (including no metal) and was able to produce on average 3.4 electrons per glucose molecule. The current density of the MV sensor was linear with both flow rate and glucose concentration. Challenges with interference chemicals were mitigated by operating at a low potential of -0.2 V vs. Ag/AgCl. As a comparison, enzymatic VACNT sensors with platinum nano-urchins were functionalized with glucose oxidase by covalent binding (EDC/NHS) or by polymer entrapment (PEDOT) and operated in phosphate buffered saline (PBS). With normalization by the overall cross-sectional area of the flow (0.713 cm2), the sensitivity of the MV, enzyme-in-solution, and covalent sensors were 45.93, 18.77, and 1.815 mA cm-2 mM-1, respectively. Corresponding limits of detection were 100, 194, and 311 nM glucose. The linear sensing ranges for the sensors were: 250 nM – 200 µM glucose for the MV sensor, 500 nM – 200 µM glucose for the enzyme-in-solution sensor, and 1 µM – 6 mM glucose for the covalent sensor. The flow cell and sensor cross-sectional area were scaled down (0.020 cm2) to enable detection from 200 µL of glucose with MV by flow injection analysis (FIA). The sensitivity of the small MV sensor was 5.002 mA cm-2 mM-1, with a limit of detection of 360 nM glucose and a linear range up to at least 150 µM glucose. The small MV sensor has the potential to measure glucose levels found in 200 µL of saliva