Coding over Sets for DNA Storage

In this paper, we study error-correcting codes for the storage of data in synthetic deoxyribonucleic acid (DNA). We investigate a storage model where data is represented by an unordered set of $M$ sequences, each of length $L$. Errors within that model are losses of whole sequences and point errors inside the sequences, such as substitutions, insertions and deletions. We propose code constructions which can correct these errors with efficient encoders and decoders. By deriving upper bounds on the cardinalities of these codes using sphere packing arguments, we show that many of our codes are close to optimal.Comment: 5 page

Community Reinvestment and Credit Risk: Evidence from an Affordable-Home-Loan Program

This study examines the performance of home purchase loans originated by a major depository institution in Philadelphia under a flexible lending program between 1988 and 1994. We examine long-term delinquency in relation to neighborhood housing market conditions, borrower credit-history scores and other factors. We find that likelihood of delinquency declines with increasing neighborhood housing market activity. Also, likelihood of delinquency is greater for borrowers with low credit-history scores and those with high ratios of housing expense to income, and when the property is unusually expensive for the neighborhood where it is located

A new approach to classification of 40 years of Antarctic sea ice concentration data

In this paper, we present a characterization of Antarctic sea ice based on the classification of annual sea ice concentration (SIC) data from 1979 to 2018. A clustering algorithm was applied to provide a climatological description of significant annual cycles of SIC and their spatial distribution around the Southern Ocean. Based on these classification results, we investigate the variability of SIC cycles on decadal and inter‐annual time scales. First, we discuss significant spatial shifts of SIC cycles during 1979–1998 and 1999–2018. In the Weddell Sea and in large parts of the Ross Sea, we observed higher SIC during the summer season, and an extension of sea ice cover in winter compared to the long‐term average. Second, we introduce the Climatological Sea Ice Anomaly Index (CSIAI), which is an annual measure for year‐round sea ice anomalies of the Southern Ocean and its regional sub‐sectors. By relating selected years of significant sea ice conditions (1981, 2007 and 2014) with atmospheric influences, we demonstrate that the CSIAI is very useful for assessing inter‐annular Antarctic SIC variability. Positive and negative sea ice anomalies can be qualitatively explained by atmospheric circulation anomalies in the years 1981 and 2007. However, in 2014, the year with the largest observed sea ice extent in our time series, we found that this positive sea ice anomaly was surprisingly not associated with a stationary and inter‐seasonally persistent pattern of circulation anomaly. This suggests that sub‐seasonal to seasonal circulation anomalies and ocean‐related processes favoured the formation of the sea ice maximum in 2014. With this study we provide additional information on the long‐term annual SIC variability around Antarctica. Furthermore, our classification approach and its results have potential for application in the evaluation of sea ice model results

Borrowing Constraints During the Housing Bubble

The impact of borrowing constraints on homeownership has been well established in the literature. Wealth is most likely to restrict homeownership followed by credit and income. Using recent movers from the 1979 National Longitudinal Survey of Youth and borrowing constraint definitions commonly used in the literature, we examine the impact of these constraints on the probability of homeownership during the housing market boom between 2003 and 2007. We show that whereas the pool of financially constrained households expanded, the marginal impact of borrowing constraints associated with income and credit quality declined during this period. The constraint associated with wealth, however, continued to have a negative impact on homeownership status, all else equal. The fact that lending standards became less strict is accepted; however the impact of this on homeownership has not been previously studied. Here we find that less restrictive underwriting does appear to have reduced the impact of income and credit quality on homeownership but the impact of the wealth constraint persists

Borrowing Constraints and Homeownership

This paper identifies the impact of borrowing constraints on homeownership in the U.S. in the aftermath of the 2008 financial crisis. While homeownership declines and tightened credit are evident, the role the tightening of credit has had on the probability of individual households to become homeowners has not been previously identified. The homeownership rate in 2010-2013 is estimated to be 2.3 percentage points lower than if the constraints were set at the 2001 level