Index of Skylab data available at Colorado School of Mines

There are no author-identified significant results in this report

Geologic and mineral and water resources investigations in western Colorado, using Skylab EREP data

The author has identified the following significant results. Skylab photographs are superior to ERTS images for photogeologic interpretation, primarily because of improved resolution. Lithologic contacts can be detected consistently better on Skylab S190A photos than on ERTS images. Color photos are best; red and green band photos are somewhat better than color-infrared photos; infrared band photos are worst. All major geologic structures can be recognized on Skylab imagery. Large folds, even those with very gentle flexures, can be mapped accurately and with confidence. Bedding attitudes of only a few degrees are recognized; vertical exaggeration factor is about 2.5X. Mineral deposits in central Colorado may be indicated on Skylab photos by lineaments and color anomalies, but positive identification of these features is not possible. S190A stereo color photography is adequate for defining drainage divides that in turn define the boundaries and distribution of ground water recharge and discharge areas within a basin

Polarity patterns of stress fibers

Stress fibers are contractile actomyosin bundles commonly observed in the cytoskeleton of metazoan cells. The spatial profile of the polarity of actin filaments inside contractile actomyosin bundles is either monotonic (graded) or periodic (alternating). In the framework of linear irreversible thermodynamics, we write the constitutive equations for a polar, active, elastic one-dimensional medium. An analysis of the resulting equations for the dynamics of polarity shows that the transition from graded to alternating polarity patterns is a nonequilibrium Lifshitz point. Active contractility is a necessary condition for the emergence of sarcomeric, alternating polarity patterns.Comment: 5 pages, 3 figure

Mechanical Instabilities of Biological Tubes

We study theoretically the shapes of biological tubes affected by various pathologies. When epithelial cells grow at an uncontrolled rate, the negative tension produced by their division provokes a buckling instability. Several shapes are investigated : varicose, enlarged, sinusoidal or sausage-like, all of which are found in pathologies of tracheal, renal tubes or arteries. The final shape depends crucially on the mechanical parameters of the tissues : Young modulus, wall-to-lumen ratio, homeostatic pressure. We argue that since tissues must be in quasistatic mechanical equilibrium, abnormal shapes convey information as to what causes the pathology. We calculate a phase diagram of tubular instabilities which could be a helpful guide for investigating the underlying genetic regulation

Feasibility of a Clutchless Dual-Shaft Hybrid Transmission System for Performance Applications

A novel hybrid-electric transmission concept was sought that yields higher acceleration and smoother gear-shifts compared to existing dual-clutch systems while improving the energy efficiency of the vehicle. After evaluating a range of strategies, the elimination of the clutch was identified as a viable method for reducing the vehicle's effective inertia and viscous losses. The proposed architecture implements a single electric motor, and two separate shafts for odd and even gears, to replace the functions of a clutch. High acceleration rates can be achieved using the electric motor when launching the vehicle. Furthermore, the torque from the electric motor (EM) and internal combustion engine (ICE) can be simultaneously delivered through the two shafts to sustain this high acceleration. A 0 to 100 km/hr time of 3.18 s was simulated for a 1600 kg vehicle using a 180 kW EM and 425 kW ICE. In addition, the EM can be used to match the speeds of consecutive gears on the two shafts to reduce jerk while shifting. Shift durations were found to vary between 0.2 and 0.9 s using this strategy. Other benefits include regenerative braking and the removal of the reverse gear since the EM can rotate in either direction. It was also found that the vehicle can be operated on only electric power in urban settings - represented by the NEDC driving cycle - if the battery is recharged through regenerative braking, and by the ICE the vehicle is stopped.Massachusetts Institute of Technology. Tata Center for Technology and Desig

Deppining of a Superfluid Vortex Inside a Circular Defect

In this work we study the process of depinning of a quantum of circulation trapped inside a disk by an applied two dimensional superflow. We use the Gross-Pitaevskii model to describe the neutral superfluid. The collective coordinate dynamics is derived directly from the condensate equation of motion, the nonlinear Schroedinger equation, and it is used to obtain an expression for the critical velocity as a function of the defect radius. This expression is compared with a numerical result obtained from the time independent nonlinear Schroedinger equation. Below the critical velocity, we obtain the dependence of the semiclassical nucleation rate with the flow velocity at infinity. Above the critical velocity, the classical vortex depinning is illustrated with a numerical simulation of the time dependent nonlinear Schroedinger equation.Comment: 8 pages, 5 figures, uses revtex and epsf.st

Active Membrane Fluctuations Studied by Micropipet Aspiration

We present a detailed analysis of the micropipet experiments recently reported in J-B. Manneville et al., Phys. Rev. Lett. 82, 4356--4359 (1999), including a derivation of the expected behaviour of the membrane tension as a function of the areal strain in the case of an active membrane, i.e., containing a nonequilibrium noise source. We give a general expression, which takes into account the effect of active centers both directly on the membrane, and on the embedding fluid dynamics, keeping track of the coupling between the density of active centers and the membrane curvature. The data of the micropipet experiments are well reproduced by the new expressions. In particular, we show that a natural choice of the parameters quantifying the strength of the active noise explains both the large amplitude of the observed effects and its remarkable insensitivity to the active-center density in the investigated range. [Submitted to Phys Rev E, 22 March 2001]Comment: 14 pages, 5 encapsulated Postscript figure