MONEY ILLUSION, GORMAN AND LAU

Any demand equation satisfying Lau’s (1982) Fundamental Theorem of Exact Aggregation and 0° homogeneity in prices and income will have a Gorman (1981) functional form for each income term. This property does not depend on symmetry or adding up. The implications of this result are illustrated by an extensive example.Demand, exact aggregation, functional form, homogeneity

Spatial characterization, resolution, and volumetric change of coastal dunes using airborne LIDAR: Cape Hatteras

ABSTRACT The technological advancement in topographic mapping known as airborne Light Detection and Ranging (LIDAR) allows researchers to gather highly accurate and densely sampled coastal elevation data at a rapid rate. The problem is to determine the optimal resolutions at which to represent coastal dunes for volumetric change analysis. This study uses digital elevation models (DEM) generated from LIDAR data and spatial statistics to better understand dune characterization at a series of spatial resolutions. The LIDAR data were collected jointly by the National Aeronautics and Space Administration (NASA), the National Oceanic and Atmospheric Administration (NOAA), and the U.S. Geological Survey (USGS). DEMs of two study sites (100×200 m) located in Cape Hatteras National Seashore, North Carolina were generated using a raster-based geographic information system (GIS). Changes in the dune volume were calculated for a 1-year period of time (Fall 1996(Fall -1997 at grid cell resolutions ranging from 1×1 to 20×20 m. Directional statistics algorithms were used to calculate local variance and characterize topographic complexity. Data processing was described in detail in order to provide an introduction to working with LIDAR data in a GIS. Results from these study sites indicated that a 1-2 m resolution provided the most reliable representation of coastal dunes on Cape Hatteras and most accurate volumetric change measurements. Results may vary at other sites and at different spatial extents, but the methods developed here can be applied to other locations to determine the optimum resolutions at which to represent and characterize topography using common GIS and database software

Critical behaviour of the Rouse model for gelling polymers

It is shown that the traditionally accepted "Rouse values" for the critical exponents at the gelation transition do not arise from the Rouse model for gelling polymers. The true critical behaviour of the Rouse model for gelling polymers is obtained from spectral properties of the connectivity matrix of the fractal clusters that are formed by the molecules. The required spectral properties are related to the return probability of a "blind ant"-random walk on the critical percolating cluster. The resulting scaling relations express the critical exponents of the shear-stress-relaxation function, and hence those of the shear viscosity and of the first normal stress coefficient, in terms of the spectral dimension $d_{s}$ of the critical percolating cluster and the exponents $\sigma$ and $\tau$ of the cluster-size distribution.Comment: 9 pages, slightly extended version, to appear in J. Phys.

Development of an Additively Manufactured Capacitive Humidity Sensor for the International Space Station

The ability to measure humidity on the International Space Station and other long-duration spaceflight missions is a crucial part of the onboard systems. For example, the Environmental Control and Life Support System (ECLSS) needs to know the amount of humidity in the air to make decisions about whether it should spend power to run the dehumidifier systems to attempt to reclaim that water. Other issues can arise if the humidity reaches too high of levels and condensation builds up on electrical components. With that in mind, it is vital that the spacecraft keeps spare sensors on board or has the ability to manufacture new sensors on demand. An additively manufactured sensor would be additionally beneficial because it would save space onboard that would normally be taken up by spares, save money from costly resupply missions, and allow the sensor to be constantly updated with the most effective design. This Technical Memorandum outlines a development process carried out to design, manufacture, and test an additively manufactured humidity sensor

Elasticity of Semiflexible Biopolymer Networks

We develop a model for gels and entangled solutions of semiflexible biopolymers such as F-actin. Such networks play a crucial structural role in the cytoskeleton of cells. We show that the rheologic properties of these networks can result from nonclassical rubber elasticity. This model can explain a number of elastic properties of such networks {\em in vitro}, including the concentration dependence of the storage modulus and yield strain.Comment: Uses RevTeX, full postscript with figures available at http://www.umich.edu/~fcm/preprints/agel/agel.htm

A comparative analysis of marine mammal tracheas

Author Posting. © The Author(s), 2013. This is the author's version of the work. It is posted here by permission of Company of Biologists for personal use, not for redistribution. The definitive version was published in Journal of Experimental Biology 217 (2014): 1154-1166, doi:10.1242/​jeb.093146.In 1940, Scholander suggested that stiffened upper airways remained open and received air from highly compressible alveoli during marine mammal diving. There are little data available on the structural and functional adaptations of the marine mammal respiratory system. The aim of this research was to investigate the anatomical (gross) and structural (compliance) characteristics of excised marine mammal tracheas. Here we defined different types of tracheal structures, categorizing pinniped tracheas by varying degrees of continuity of cartilage (categories 1-4) and cetacean tracheas by varying compliance values (categories 5A and 5B). Some tracheas fell into more than one category, along their length, for example, the harbor seal (Phoca vitulina) demonstrated complete rings cranially, and as the trachea progressed caudally tracheal rings changed morphology. Dolphins and porpoises had less stiff, more compliant spiraling rings while beaked whales had very stiff, less compliant spiraling rings. The pressure-volume (P-V) relationships of isolated tracheas from different species were measured to assess structural differences between species. These findings lend evidence for pressure-induced collapse and re-inflation of lungs, perhaps influencing variability in dive depth or ventilation rates of the species investigated.This project was supported by a grant from the Office of Naval Research (award number N00014-10-1-0059).2014-12-0