HFR Code: A Flexible Replication Scheme for Cloud Storage Systems

Fractional repetition (FR) codes are a family of repair-efficient storage codes that provide exact and uncoded node repair at the minimum bandwidth regenerating point. The advantageous repair properties are achieved by a tailor-made two-layer encoding scheme which concatenates an outer maximum-distance-separable (MDS) code and an inner repetition code. In this paper, we generalize the application of FR codes and propose heterogeneous fractional repetition (HFR) code, which is adaptable to the scenario where the repetition degrees of coded packets are different. We provide explicit code constructions by utilizing group divisible designs, which allow the design of HFR codes over a large range of parameters. The constructed codes achieve the system storage capacity under random access repair and have multiple repair alternatives for node failures. Further, we take advantage of the systematic feature of MDS codes and present a novel design framework of HFR codes, in which storage nodes can be wisely partitioned into clusters such that data reconstruction time can be reduced when contacting nodes in the same cluster.Comment: Accepted for publication in IET Communications, Jul. 201

Firm Entry, Firm Exit, And Urban-Biased Growth

We introduce a taxonomy that classifies industries using three criteria: net growth in the number of firms; the interrelationship between firm entry and firm exit; and the degree of urban-bias in industry growth. We show that in 9 of 15 two-digit NAICS industries investigated, there is evidence of urban bias consistent with a comparative advantage to starting a business in urban markets. The urban advantage is due primarily to faster firm entry rates. Urban and rural firms have similar firm exit rates, consistent with a presumption that there are equal expected profit rates conditional on entry across markets. Urban areas grow faster because they induce faster firm entry and not because urban firms are more likely to succeed.Entry – Exit Pattern; Taxonomy; Urban-Bias; Expansion; Churning; Entrepreneurship; Economic Development

Firm Entry and Exit in Iowa, 1992 - 2004

This paper uses the pattern of firm entry and exit to develop a classification system for industries. The classifications include urban-rural bias; long-term growth; and firm survival patterns. The first captures the fact that sector-specific economic growth may be favored in urban areas for some industries and may benefit from low population density for others. Some industries have experienced long-term expansion in firm numbers while others have experienced a decline. Finally, some industries are characterized by high rates of both entry and exit while others have low rates of both. A taxonomy classifying industries according to those three criteria is developed in this paper. The taxonomy is applied to the Iowa subset of the National Establishment Time-Series (NETS) database over the period from 1992 to 2004. County level entry and exit rates are shown to be positively correlated across nearly all 2 digit NAICS code industries. Industry growth is found to be biased against rural areas. Not all of the industries experienced expansion or have a positive net entry rate. Entry of new firms replaces old incumbent firms in each industry but to different degrees. Understanding firm entry - exit pattern can help design customized policies of fostering expansion of specific industries in Iowa according to their location bias, industry growth patterns and development dynamics.Taxonomy; Expansion; Churning; Entrepreneurship; Economic Development; entry-exit pattern; location bias

Stopping Start-Ups: How The Business Cycle Affects Entrepreneurship

This study analyzes whether economic conditions at the time of labor market entry affect entrepreneurship, using difference in business start-ups between cohorts of college students graduating in boom or bust economic conditions. Those graduating during an economic bust tend to delay their business start-ups relative to boom period graduates by about two years. Our results are consistent with additional findings that higher unemployment rates at time of graduation significantly delay the first business start-up across all college graduation cohorts over the 1982-2004 period. The adverse effect of a bust is temporary, delaying but not preventing self-employment over the life-cycle.Entrepreneurship; boom; bust; occupatiopnal choice; survivor analysis; business cycle; cohort

After They Graduate: An Overview of the Iowa State University Alumni Survey

This report provides a descriptive overview of the Iowa State University Alumni Survey. In late 2007, 25,000 Iowa State University alumni who received bachelor's degree between 1982 and 2006 were surveyed to obtain information on their career paths, employment status, further education, entrepreneurial activities, community engagement and current income. The on-line and written survey resulted in approximately 5,500 valid returns.human capital; career path; bachelor's degree recipients; land-grant university; Entrepreneurship; personal income; community engagement.

Butyrate induces profound changes in gene expression related to multiple signal pathways in bovine kidney epithelial cells

BACKGROUND: Global gene expression profiles of bovine kidney epithelial cells regulated by sodium butyrate were investigated with high-density oligonucleotide microarrays. The bovine microarray with 86,191 distinct 60mer oligonucleotides, each with 4 replicates, was designed and produced with Maskless Array Synthesizer technology. These oligonucleotides represent approximately 45,383 unique cattle sequences. RESULTS: 450 genes significantly regulated by butyrate with a median False Discovery Rate (FDR) = 0 % were identified. The majority of these genes were repressed by butyrate and associated with cell cycle control. The expression levels of 30 selected genes identified by the microarray were confirmed using real-time PCR. The results from real-time PCR positively correlated (R = 0.867) with the results from the microarray. CONCLUSION: This study presented the genes related to multiple signal pathways such as cell cycle control and apoptosis. The profound changes in gene expression elucidate the molecular basis for the pleiotropic effects of butyrate on biological processes. These findings enable better recognition of the full range of beneficial roles butyrate may play during cattle energy metabolism, cell growth and proliferation, and possibly in fighting gastrointestinal pathogens

Social Entrepreneurship: An Overview Of a Public University Alumni Survey

This report presents an overview of social entrepreneurship activities of public university graduates obtained from a survey. Almost 3 percent of respondents had created at least one nonprofit organization. The primary focus of the organizations founded by social entrepreneur respondents was education and youth related causes, with services geared heavily toward local needs. The nonprofit organizations founded to meet these needs were typically small, with one or two paid employees and 5 to 15 volunteers.social entrepreneurship; non-profit enterprises; alumni

Entrepreneurship and Higher Education: An Overview of the Iowa State University Alumni Survey

�Entrepreneurship is a hot topic both in academic and policy circles.There is a growing recognition that entrepreneurship is a driving force in economic growth development in both�established and emerging economies. There is also an increasing body of evidence suggesting entrepreneurship that stems from a high level of human capital and creativity is the most likely to produce the goods, services and ultimately the jobs that fuel economic growth development and competitiveness. If human capital and innovation are important for growth entrepreneurship, then higher education should have a significant role to play in fostering entrepreneurship.In this report we present a descriptive overview of the entrepreneurial activities of graduates from Iowa State University – a medium-sized public university in the United States. The data were obtained from a random sample of 25,000 Iowa State University bachelor's degree recipients between 1982 and 2006. The survey requested information on graduates' employment history, further education, income, entrepreneurial activity and community involvement. The on-line survey was conducted in 2008 and produced 5,416 usable responses – a response rate of 21.6 percent. Survey details are presented in Appendix I. �