Love at What Price? Estimating the Value of Marriage

Using a law within Social Security that provides clear financial incentives to delay marriage, we estimate the financial value of a month of marriage. Specifically, the law provides that widows who are eligible for Social Security benefits on their deceased spouse\u27s earnings records are eligible for benefits at age 60, unless they remarry before that age. If they remarry before that age, they cannot claim widow benefits and must wait until at least age 62 to claim spousal benefits on their new husband\u27s record, which are typically less generous than widow benefits. To generate an estimate of what this behavior implies about the value of marriage, we use data from five panels of the Survey of Income and Program Participation linked to administrative data from Social Security. We estimate the cost of marrying before age 60 imposed by the Social Security program. We develop a model that reflects the institutional details of Social Security and generate a likelihood function that reflects that model. By taking advantage of the variation in these costs and when or whether widows remarry before age 60, we estimate the benefit of marriage to be $8000/month. These estimates appear to be reasonable in the context of the short length of time widows are willing to wait and the high value of Social Security benefits

Greedy permanent magnet optimization

A number of scientific fields rely on placing permanent magnets in order to produce a desired magnetic field. We have shown in recent work that the placement process can be formulated as sparse regression. However, binary, grid-aligned solutions are desired for realistic engineering designs. We now show that the binary permanent magnet problem can be formulated as a quadratic program with quadratic equality constraints (QPQC), the binary, grid-aligned problem is equivalent to the quadratic knapsack problem with multiple knapsack constraints (MdQKP), and the single-orientation-only problem is equivalent to the unconstrained quadratic binary problem (BQP). We then provide a set of simple greedy algorithms for solving variants of permanent magnet optimization, and demonstrate their capabilities by designing magnets for stellarator plasmas. The algorithms can a-priori produce sparse, grid-aligned, binary solutions. Despite its simple design and greedy nature, we provide an algorithm that outperforms the state-of-the-art algorithms while being substantially faster, more flexible, and easier-to-use

Heads or tails: L1 insertion-associated 5' homopolymeric sequences

<p>Abstract</p> <p>Background</p> <p>L1s are one of the most successful autonomous mobile elements in primate genomes. These elements comprise as much as 17% of primate genomes with the majority of insertions occurring via target primed reverse transcription (TPRT). Twin priming, a variant of TPRT, can result in unusual DNA sequence architecture. These insertions appear to be inverted, truncated L1s flanked by target site duplications.</p> <p>Results</p> <p>We report on loci with sequence architecture consistent with variants of the twin priming mechanism and introduce dual priming, a mechanism that could generate similar sequence characteristics. These insertions take the form of truncated L1s with hallmarks of classical TPRT insertions but having a poly(T) simple repeat at the 5' end of the insertion. We identified loci using computational analyses of the human, chimpanzee, orangutan, rhesus macaque and marmoset genomes. Insertion site characteristics for all putative loci were experimentally verified.</p> <p>Conclusions</p> <p>The 39 loci that passed our computational and experimental screens probably represent inversion-deletion events which resulted in a 5' inverted poly(A) tail. Based on our observations of these loci and their local sequence properties, we conclude that they most probably represent twin priming events with unusually short non-inverted portions. We postulate that dual priming could, theoretically, produce the same patterns. The resulting homopolymeric stretches associated with these insertion events may promote genomic instability and create potential target sites for future retrotransposition events.</p

Internal priming: An opportunistic pathway for L1 and Alu retrotransposition in hominins

Retrotransposons, specifically Alu and L1 elements, have been especially successful in their expansion throughout primate genomes. While most of these elements integrate through an endonuclease-mediated process termed target primed reverse transcription, a minority integrate using alternative methods. Here we present evidence for one such mechanism, which we term internal priming and demonstrate that loci integrating through this mechanism are qualitatively different from classical insertions. Previous examples of this mechanism are limited to cell culture assays, which show that reverse transcription can initiate upstream of the 3′ poly-A tail during retrotransposon integration. To detect whether this mechanism occurs in vivo as well as in cell culture, we have analyzed the human genome for internal priming events using recently integrated L1 and Alu elements. Our examination of the human genome resulted in the recovery of twenty events involving internal priming insertions, which are structurally distinct from both classical TPRT-mediated insertions and non-classical insertions. We suggest two possible mechanisms by which these internal priming loci are created and provide evidence supporting a role in staggered DNA double-strand break repair. Also, we demonstrate that the internal priming process is associated with inter-chromosomal duplications and the insertion of filler DNA. © 2009 Elsevier B.V. All rights reserved

In Situ Corrosion Studies on the Battleship USS Arizona

U.S. National Park Service Submerged Resources Center archaeologists and University of Nebraska-Lincoln metallurgists are assessing hull corrosion by drilling through accumulated concretions and measuring pH and corrosion potentials. Concretion samples are being analyzed to determine the role of microbes in the corrosion process, identify chemical species, and measure electrical and physical properties. The lowest values of pH and E corr occur at the metal/concretion interface. Analysis suggests a variable corrosion rate supported by hydrogen discharge and/or oxygen reduction inside the concretion