Surface micromachined membranes for tunnel transducers

We have developed low-temperature surface micromachining procedures for the fabrication of suspended SiO2/Si3N4 membranes. This fabrication method was integrated with electron beam lithography, anisotropic ion etching, and electroplating to construct electrostatically deflectable tunnel transducers. We show the structures and some preliminary measurements on the performance of these monolithic devices

The Disappearing Gender Gap: The Impact of Divorce, Wages, and Preferences on Education Choices and Women's Work

Women born in 1935 went to college significantly less than their male counterparts and married women's labor force participation (LFP) averaged 40% between the ages of thirty and forty. The cohort born twenty years later behaved very differently. The education gender gap was eliminated and married women's LFP averaged 70% over the same ages. In order to evaluate the quantitative contributions of the many significant changes in the economic environment, family structure, and social norms that occurred over this period, this paper develops a dynamic life-cycle model calibrated to data relevant to the 1935 cohort. We find that the higher probability of divorce and the changes in wage structure faced by the 1955 cohort are each able to explain, in isolation, a large proportion (about 60%) of the observed changes in female LFP. After combining all economic and family structure changes, we find that a simple change in preferences towards work can account for the remaining change in LFP. To eliminate the education gender gap requires, on the other hand, for the psychic cost of obtaining higher education to change asymmetrically for women versus men.divorce, labor force participation, gender gap, education and skill premium

Recording processes in perpendicular patterned media using longitudinal magnetic recording heads

An experimental study of the recording processes in patterned magnetic media is presented. The reading of patterned media using spin-valve elements is compared to the signal levels from magneto-resistive sensors. Writing and reading of patterned columnar media at high areal densities is demonstrated. A new experimental technique has been developed that allows precise determination of the location of the write gap poles with respect to the patterned media column during the write process. Implications for patterned media write synchronization and the write head field requirements are discussed

Writing and reading of single magnetic domain per bit perpendicular patterned media

By fabricating patterned media with a large number of nanoscale single domain magnetic particles embedded in a nonmagnetic substrate, and by writing the magnetization for each of these particles in a desired direction, nonvolatile magnetic storage of information could reach densities much higher than what is currently thought possible for longitudinal continuous media. We have fabricated high aspect ratio perpendicular nickel columnar nanoparticles embedded in a hard Al2O3/GaAs substrate. We show that the magnetization states of the individual magnets can be controlled by demonstrating that prototype patterned "single magnetic domain per bit" data tracks can be written and read back using current magnetic information storage technology

The University Micro/Nanosatellite as a Micropropulsion Testbed

Using reconfigurable and adaptable networks of micro/nanosatellites to support cost-effective space missions is a popular new direction in the space community. Since the overall resources of micro/nanosatellites are more restricted than those of a single large satellite, the micropropulsion system needs to be lightweight, low-cost, and practical. This paper describes the collaboration between the Arizona State University Student Satellite Lab and the Air Force Research Laboratory Propulsion Directorate to flight test a micropropulsion system on a nanosatellite, ASUSat2. The motivation behind this conjuncture is to employ university satellites as an inexpensive testbed for unconventional new technologies. This paper first provides background on the needs of a micropropulsion system on a micro/nanosatellite cluster, and outlines the issues concerning its development. Then it addresses the experience of the ASU group in designing and building nanosatellites, and describes the design and mission of ASUSat2, which is part of a three-satellite constellation. Next, it examines two micropropulsion systems, the free molecule micro-resistojet and the cold-gas micronozzle, for the ASUSat2 mission. The preliminary study shows that the free molecule micro-resistojet would be an attractive micropropulsion system for ASUSat2

How to collect high quality segmentations: use human or computer drawn object boundaries?

High quality segmentations must be captured consistently for applications such as biomedical image analysis. While human drawn segmentations are often collected because they provide a consistent level of quality, computer drawn segmentations can be collected efficiently and inexpensively. In this paper, we examine how to leverage available human and computer resources to consistently create high quality segmentations. We propose a quality control methodology. We demonstrate how to apply this approach using crowdsourced and domain expert votes for the "best" segmentation from a collection of human and computer drawn segmentations for 70 objects from a public dataset and 274 objects from biomedical images. We publicly share the library of biomedical images which includes 1,879 manual annotations of the boundaries of 274 objects. We found for the 344 objects that no single segmentation source was preferred and that human annotations are not always preferred over computer annotations. These results motivated us to examine the traditional approach to evaluate segmentation algorithms, which involves comparing the segmentations produced by the algorithms to manual annotations on benchmark datasets. We found that algorithm benchmarking results change when the comparison is made to consensus-voted segmentations. Our results led us to suggest a new segmentation approach that uses machine learning to predict the optimal segmentation source and a modified segmentation evaluation approach.National Science Foundation (IIS-0910908

Silk-fibronectin protein alloy fibres support cell adhesion and viability as a high strength, matrix fibre analogue

Silk is a natural polymer with broad utility in biomedical applications because it exhibits general biocompatibility and high tensile material properties. While mechanical integrity is important for most biomaterial applications, proper function and integration also requires biomaterial incorporation into complex surrounding tissues for many physiologically relevant processes such as wound healing. In this study, we spin silk fibroin into a protein alloy fibre with whole fibronectin using wet spinning approaches in order to synergize their respective strength and cell interaction capabilities. Results demonstrate that silk fibroin alone is a poor adhesive surface for fibroblasts, endothelial cells, and vascular smooth muscle cells in the absence of serum. However, significantly improved cell attachment is observed to silk-fibronectin alloy fibres without serum present while not compromising the fibres' mechanical integrity. Additionally, cell viability is improved up to six fold on alloy fibres when serum is present while migration and spreading generally increase as well. These findings demonstrate the utility of composite protein alloys as inexpensive and effective means to create durable, biologically active biomaterials.T32 EB006359 - NIBIB NIH HH

The Disappearing Gender Gap: The Impact of Divorce, Wages, and Preferences on Education Choices and Women's Work

Women born in 1935 went to college significantly less than their male counterparts and married women’s labor force participation (LFP) averaged 40% between the ages of thirty and forty. The cohort born twenty years later behaved very differently. The education gender gap was eliminated and married women’s LFP averaged 70% over the same ages. In order to evaluate the quantitative contributions of the many significant changes in the economic environment, family structure, and social norms that occurred over this period, this paper develops a dynamic life-cycle model calibrated to data relevant to the 1935 cohort. We find that the higher probability of divorce and the changes in wage structure faced by the 1955 cohort are each able to explain, in isolation, a large proportion (about 60%) of the observed changes in female LFP. After combining all economic and family structure changes, we find that a simple change in preferences towards work can account for the remaining change in LFP. To eliminate the education gender gap requires, on the other hand, for the psychic cost of obtaining higher education to change asymmetrically for women versus men.