Standards for Library Services to People in Institutions

published or submitted for publicatio

Computational astrophysics

Astronomy is an area of applied physics in which unusually beautiful objects challenge the imagination to explain observed phenomena in terms of known laws of physics. It is a field that has stimulated the development of physical laws and of mathematical and computational methods. Current computational applications are discussed in terms of stellar and galactic evolution, galactic dynamics, and particle motions

Capitalism With Capital: A Suggested Remedy for the Absence of Investment Decision Making in Basic Microeconomics Teaching

'[U]nder competition, the rate of return on investment tends toward equality in all industries.' Introductory and intermediate microeconomics textbooks are sketchy in explaining how capital is allocated by financial markets. Capital budgeting techniques, primarily net present value, deserve a more prominent role. This article suggests ways in which financial economics can be integrated into undergraduate courses to illuminate entry into (and exit from) industries in response to profit opportunities, as an essential part of economists' narration of resource allocation in a capitalistic and dynamic market economy.

Insect Pests of Christmas Trees

PDF pages: 2

A nearly-mlogn time solver for SDD linear systems

We present an improved algorithm for solving symmetrically diagonally dominant linear systems. On input of an $n\times n$ symmetric diagonally dominant matrix $A$ with $m$ non-zero entries and a vector $b$ such that $A\bar{x} = b$ for some (unknown) vector $\bar{x}$, our algorithm computes a vector $x$ such that $||{x}-\bar{x}||_A < \epsilon ||\bar{x}||_A$ {$||\cdot||_A$ denotes the A-norm} in time $${\tilde O}(m\log n \log (1/\epsilon)).$$ The solver utilizes in a standard way a `preconditioning' chain of progressively sparser graphs. To claim the faster running time we make a two-fold improvement in the algorithm for constructing the chain. The new chain exploits previously unknown properties of the graph sparsification algorithm given in [Koutis,Miller,Peng, FOCS 2010], allowing for stronger preconditioning properties. We also present an algorithm of independent interest that constructs nearly-tight low-stretch spanning trees in time $\tilde{O}(m\log{n})$, a factor of $O(\log{n})$ faster than the algorithm in [Abraham,Bartal,Neiman, FOCS 2008]. This speedup directly reflects on the construction time of the preconditioning chain.Comment: to appear in FOCS1

Range Extensions for Species of Sphecidae (Hymenoptera) in the Northeastern United States

The ranges of 10 Nearctic species of Sphecidae, Spilomena pusilla, Tachytes parvus, Solierella plenoculoides, Pison agile, Entomognathus lenapeorum, Rhopalum clavipes, Crabro hilaris, C. tenuis, Alysson conicus and Lestiphorus cockerelli, are extended in the northeastern U.S. based upon collections made in Pennsylvania and New York. The first prey record for a North American species of Lestiphorus, cockerelli, is included

The "backdoor pathway" of androgen synthesis in human male sexual development.

Mammalian sex determination (male versus female) is largely controlled by genes, whereas sex differentiation (development of reproductive structures) is largely controlled by hormones. Work in the 20th century indicated that female external anatomy was a "default" pathway of development not requiring steroids, whereas male genital development required testicular testosterone plus dihydrotestosterone (DHT) made in genital skin according to a "classic" pathway. Recent work added the description of an alternative "backdoor" pathway of androgen synthesis discovered in marsupials. Unique "backdoor steroids" are found in human hyperandrogenic disorders, and genetic disruption of the pathway causes disordered male sexual development, suggesting it plays an essential role. O'Shaughnessy and colleagues now show that the principal human backdoor androgen is androsterone and provide strong evidence that it derives from placental progesterone that is metabolized to androsterone in nontesticular tissues. These studies are essential to understanding human sexual development and its disorders