10,043 research outputs found
The plasma radiation shield - Concept, and applications to space vehicles
Plasma radiation shield - concept and applications to space vehicle
Ultra-fast mission analysis routine for Apollo Block 2 environmental control system radiators Final report
Computer program for rapid mission analysis of Apollo Block 2 environmental control system radiator
Dwarf Mistletoe Parasite in Spruce
Locations of all known major infection centers of dwarf mistletoe (Arceuthobium pusillum) in Minnesota are presented and compared to botanical ranges of important hosts. A brief summary of disease symptoms and identification of the parasite are included
Mechanism of Salivary Amylase Action
The action of salivary amylase on amylo-type compounds is interpreted by most investigators as a random hydrolysis of the a-1, 4-glucosidic linkages. By this mode of action, intermediate reaction products which would have physical and chemical properties characteristic of the reaction mixture may be formed. The nature of these intermediates has been deduced from measurements of osmotic pressure, viscosity, iodine coloration, reducing power, etc. generally on crude enzymic digests. Investigations of this type which form the basis of the concept of random action are excellently reviewed by Hanes (9)
Scaling properties of a low-actuation pressure microfluidic valve
Using basic physical arguments, we present a design and method for the fabrication of microfluidic valves using multilayer soft lithography. These on-off valves have extremely low actuation pressures and can be used to fabricate active functions, such as pumps and mixers in integrated microfluidic chips. We characterized the performance of the valves by measuring both the actuation pressure and flow resistance over a wide range of design parameters, and compared them to both finite element simulations and alternative valve geometries
Drying and cracking mechanisms in a starch slurry
Starch-water slurries are commonly used to study fracture dynamics. Drying
starch-cakes benefit from being simple, economical, and reproducible systems,
and have been used to model desiccation fracture in soils, thin film fracture
in paint, and columnar joints in lava. In this paper, the physical properties
of starch-water mixtures are studied, and used to interpret and develop a
multiphase transport model of drying. Starch-cakes are observed to have a
nonlinear elastic modulus, and a desiccation strain that is comparable to that
generated by their maximum achievable capillary pressure. It is shown that a
large material porosity is divided between pore spaces between starch grains,
and pores within starch grains. This division of pore space leads to two
distinct drying regimes, controlled by liquid and vapor transport of water,
respectively. The relatively unique ability for drying starch to generate
columnar fracture patterns is shown to be linked to the unusually strong
separation of these two transport mechanisms.Comment: 9 pages, 8 figures [revised in response to reviewer comments
Drying and cracking mechanisms in a starch slurry
Starch-water slurries are commonly used to study fracture dynamics. Drying
starch-cakes benefit from being simple, economical, and reproducible systems,
and have been used to model desiccation fracture in soils, thin film fracture
in paint, and columnar joints in lava. In this paper, the physical properties
of starch-water mixtures are studied, and used to interpret and develop a
multiphase transport model of drying. Starch-cakes are observed to have a
nonlinear elastic modulus, and a desiccation strain that is comparable to that
generated by their maximum achievable capillary pressure. It is shown that a
large material porosity is divided between pore spaces between starch grains,
and pores within starch grains. This division of pore space leads to two
distinct drying regimes, controlled by liquid and vapor transport of water,
respectively. The relatively unique ability for drying starch to generate
columnar fracture patterns is shown to be linked to the unusually strong
separation of these two transport mechanisms.Comment: 9 pages, 8 figures [revised in response to reviewer comments
An Experimental Investigation of the Scaling of Columnar Joints
Columnar jointing is a fracture pattern common in igneous rocks in which
cracks self-organize into a roughly hexagonal arrangement, leaving behind an
ordered colonnade. We report observations of columnar jointing in a laboratory
analog system, desiccated corn starch slurries. Using measurements of moisture
density, evaporation rates, and fracture advance rates as evidence, we suggest
an advective-diffusive system is responsible for the rough scaling behavior of
columnar joints. This theory explains the order of magnitude difference in
scales between jointing in lavas and in starches. We investigated the scaling
of average columnar cross-sectional areas due to the evaporation rate, the
analog of the cooling rate of igneous columnar joints. We measured column areas
in experiments where the evaporation rate depended on lamp height and time, in
experiments where the evaporation rate was fixed using feedback methods, and in
experiments where gelatin was added to vary the rheology of the starch. Our
results suggest that the column area at a particular depth is related to both
the current conditions, and hysteretically to the geometry of the pattern at
previous depths. We argue that there exists a range of stable column scales
allowed for any particular evaporation rate.Comment: 12 pages, 11 figures, for supporting online movies, go to
http://www.physics.utoronto.ca/nonlinear/movies/starch_movies.htm
Experimental material handling device Final report
Design, fabrication and test of materials handling device for spacecraft us
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