Optimal paths on the road network as directed polymers

We analyze the statistics of the shortest and fastest paths on the road network between randomly sampled end points. To a good approximation, these optimal paths are found to be directed in that their lengths (at large scales) are linearly proportional to the absolute distance between them. This motivates comparisons to universal features of directed polymers in random media. There are similarities in scalings of fluctuations in length/time and transverse wanderings, but also important distinctions in the scaling exponents, likely due to long-range correlations in geographic and man-made features. At short scales the optimal paths are not directed due to circuitous excursions governed by a fat-tailed (power-law) probability distribution.Comment: 5 pages, 7 figure

Measuring What Employers Really Do about Entry Wages over the Business Cycle

In models recently published by several influential macroeconomic theorists, rigidity in the real wages that firms pay newly hired workers plays a crucial role in generating realistically large cyclical fluctuations in unemployment. There is remarkably little evidence, however, on whether employers' hiring wages really are invariant to business cycle conditions. We review the small empirical literature and show that the methods used thus far are poorly suited for identifying employers’ wage practices. We propose a simpler and more relevant approach – use matched employer/employee longitudinal data to identify entry jobs and then directly track the cyclical variation in the real wages paid to workers newly hired into those jobs. We illustrate the methodology by applying it to data from an annual census of employers in Portugal over the period 1982-2007. We find that real entry wages in Portugal over this period tend to be about 1.8 percent higher when the unemployment rate is one percentage point lower. Like most recent evidence on other aspects of wage cyclicality, our results suggest that the cyclical elasticity of wages is similar to that of employment.real wage cyclicality, entry wages, matched employer-employee data

Linear-Time Superbubble Identification Algorithm for Genome Assembly

DNA sequencing is the process of determining the exact order of the nucleotide bases of an individual's genome in order to catalogue sequence variation and understand its biological implications. Whole-genome sequencing techniques produce masses of data in the form of short sequences known as reads. Assembling these reads into a whole genome constitutes a major algorithmic challenge. Most assembly algorithms utilize de Bruijn graphs constructed from reads for this purpose. A critical step of these algorithms is to detect typical motif structures in the graph caused by sequencing errors and genome repeats, and filter them out; one such complex subgraph class is a so-called superbubble. In this paper, we propose an O(n+m)-time algorithm to detect all superbubbles in a directed acyclic graph with n nodes and m (directed) edges, improving the best-known O(m log m)-time algorithm by Sung et al

Sub-Adviser Fee Litigation: Will Section 36(b) Acquire Teeth?

(Excerpt) Section 36(b) of the Investment Company Act establishes a private breach of fiduciary duty cause of action for shareholders in an investment company, or mutual fund, to challenge the fees charged by the mutual fund’s investment adviser, in recognition of the fact that the adviser or one of its affiliates customarily creates the mutual fund and has a great deal of influence over the composition of the mutual fund’s board of directors or trustees, which negotiates the fees paid to the investment adviser. Under the Gartenberg standard, which was substantially adopted by the Supreme Court in Jones v. Harris Associates, succeeding on an excessive fee claim is difficult, however, because Section 36(b) is violated only when the adviser charges a “fee that is so disproportionately large that it bears no reasonable relationship to the services rendered and could not have been the product of arm’s-length bargaining.” In the last several years, creative plaintiffs have looked to the fees paid by mutual funds to advisers and sub-advisers of mutual funds as a measuring tool to argue that fees are excessive. The plaintiffs have focused on the services provided to a mutual fund by the adviser and sub-advisers and have argued that the services are largely duplicative. If this is so, the logic goes, then why is the adviser paid such a large fee

Efficient Computation of Sequence Mappability

Sequence mappability is an important task in genome re-sequencing. In the $(k,m)$-mappability problem, for a given sequence $T$ of length $n$, our goal is to compute a table whose $i$th entry is the number of indices $j \ne i$ such that length-$m$ substrings of $T$ starting at positions $i$ and $j$ have at most $k$ mismatches. Previous works on this problem focused on heuristic approaches to compute a rough approximation of the result or on the case of $k=1$. We present several efficient algorithms for the general case of the problem. Our main result is an algorithm that works in $\mathcal{O}(n \min\{m^k,\log^{k+1} n\})$ time and $\mathcal{O}(n)$ space for $k=\mathcal{O}(1)$. It requires a carefu l adaptation of the technique of Cole et al.~[STOC 2004] to avoid multiple counting of pairs of substrings. We also show $\mathcal{O}(n^2)$-time algorithms to compute all results for a fixed $m$ and all $k=0,\ldots,m$ or a fixed $k$ and all $m=k,\ldots,n-1$. Finally we show that the $(k,m)$-mappability problem cannot be solved in strongly subquadratic time for $k,m = \Theta(\log n)$ unless the Strong Exponential Time Hypothesis fails.Comment: Accepted to SPIRE 201

Measuring What Employers Really Do about Entry Wages over the Business Cycle

In models recently published by several influential macroeconomic theorists, rigidity in the real wages that firms pay newly hired workers plays a crucial role in generating realistically large cyclical fluctuations in unemployment. There is remarkably little evidence, however, on whether employers’ hiring wages really are invariant to business cycle conditions. We review the small empirical literature and show that the methods used thus far are poorly suited for identifying employers’ wage practices. We propose a simpler and more relevant approach – use matched employer/employee longitudinal data to identify entry jobs and then directly track the cyclical variation in the real wages paid to workers newly hired into those jobs. We illustrate the methodology by applying it to data from an annual census of employers in Portugal over the period 1982-2007. We find that real entry wages in Portugal over this period tend to be about 1.8 percent higher when the unemployment rate is one percentage point lower. Like most recent evidence on other aspects of wage cyclicality, our results suggest that the cyclical elasticity of wages is similar to that of employment

The Association Between Dental Coverage and Self-reported Health in Older Adults jGPHA

Background: For the older population of the United States, lack of dental insurance coverage is a substantial health problem. The purpose of the present study was to examine the longitudinal relationship between dental coverage and self-reported health among older adults. Methods: The Health and Retirement Study (HRS), a nationally representative biennial cohort study of community-dwelling individuals, includes 19,595 adults (aged 50 and older) living in the United States. For the 2010, 2012, and 2014 waves, the independent variable of dental coverage and the outcome of self-reported health were examined. Results: At each time point, dental coverage for older adults had a positive association with self-reported health (parameter estimate, β=0.340, standard error (SE)=0.039, p\u3c0.0001), controlling for sociodemographic variables of age, sex, race/ethnicity, education, and the status of edentulism. There were no significant longitudinal effects for dental coverage associated with selfreported health. Conclusions: At each time point, the results show a positive association between having dental coverage and better self-reported health of older adults. This is relevant, because, in the United States, there is an increasing population of older people

Production of belite calcium sulfoaluminate cement using sulfur as a fuel and as a source of clinker sulfur trioxide : pilot kiln trial

The authors gratefully acknowledge the financial support provided by the Gulf Organization for Research and Development (GORD), Qatar, through research grant number ENG016RGG11757. The authors would also like to acknowledge Thomas Matschei and Guanshu Li for the stimulating and fruitful discussions concerning the development of this work. The continuous support prior to, during and after the pilot kiln trial from Vadym Kuznietsov and the entire team at IBU-tec is also greatly appreciated.Peer reviewedPublisher PD