On a problem in eigenvalue perturbation theory

We consider additive perturbations of the type $K_t=K_0+tW$, $t\in [0,1]$, where $K_0$ and $W$ are self-adjoint operators in a separable Hilbert space $\mathcal{H}$ and $W$ is bounded. In addition, we assume that the range of $W$ is a generating (i.e., cyclic) subspace for $K_0$. If $\lambda_0$ is an eigenvalue of $K_0$, then under the additional assumption that $W$ is nonnegative, the Lebesgue measure of the set of all $t\in [0,1]$ for which $\lambda_0$ is an eigenvalue of $K_t$ is known to be zero. We recall this result with its proof and show by explicit counterexample that the nonnegativity assumption $W\geq 0$ cannot be removed.Comment: 10 pages; added Lemma 2.4, typos removed; to appear in J. Math. Anal. App

A competitive environment for exploratory query expansion

Most information workers query digital libraries many times a day. Yet people have little opportunity to hone their skills in a controlled environment, or compare their performance with others in an objective way. Conversely, although search engine logs record how users evolve queries, they lack crucial information about the user's intent. This paper describes an environment for exploratory query expansion that pits users against each other and lets them compete, and practice, in their own time and on their own workstation. The system captures query evolution behavior on predetermined information-seeking tasks. It is publicly available, and the code is open source so that others can set up their own competitive environments

Theory of liquid film growth and wetting instabilities on graphene

We investigate wetting phenomena near graphene within the Dzyaloshinskii-Lifshitz-Pitaevskii theory for light gases composed of hydrogen, helium and nitrogen in three different geometries where graphene is either affixed to an insulating substrate, submerged or suspended. We find that the presence of graphene has a significant effect in all configurations. In a suspended geometry where graphene is able to wet on only one side, liquid film growth becomes arrested at a critical thickness which may trigger surface instabilities and pattern formation analogous to spinodal dewetting. These phenomena are also universally present in other two-dimensional materials.Comment: 13 pages, includes expanded supplemental material with doping dependenc

International Ultraviolet Explorer Atlas of O-typespectra from 1200 to 1900 Angstrom

The IUE archives provide an unprecedented sample of uniform, high-quality ultraviolet stellar spectra. In particular, they contain high-resolution SWP data for nearly 200 different O stars. We have undertaken a survey of the 1200-1900 A region in about 120 of them having homogeneous optical spectral classifications to investigate systematically the behavior of the ultraviolet features, incuding the prominent stellar wind profiles and the degree to which they correlate with the optical types. The standard extracted spectrograms have been rebinned to a constant wavelength resolution of 0.25A and uniformly normalized (not dereddened) at the GSFC RDAF. They are then plotted at 10A/cm, with reseau, photometric quality and echelle order junction flags available. This atlas contains such plots for about 100 stars, arranged in spectral-type, luminosity and peculiar object sequences. The results show a high degree of correlation between the ultraviolet features, both photospheric and stellar-wind, and the optical classifications for the majority of the O-type stars

Optimizing Guideline-Recommended Antibiotic Doses for Pediatric Infective Endocarditis

The American Heart Association recently published an updated scientific statement on the management of infective endocarditis in childhood. The recommendations included for vancomycin, aminoglycoside, and β-lactam dosing and monitoring are based primarily on expert opinion and do not consider available evidence for dose optimization based on pharmacokinetic and pharmacodynamic principles in pediatric patients. This is concerning because even when clinically necessary, some practitioners may be hesitant to deviate from guideline-recommended doses. In this perspective, we highlight potential areas for improvement in the statement-recommended doses and summarize evidence supporting antibiotic dosing optimization. The addition of a pediatric clinical pharmacist with expertise in antibiotic dosing to the panel would be beneficial for future updates

Analyzing library collections with starfield visualizations

This paper presents a qualitative and formative study of the uses of a starfield-based visualization interface for analysis of library collections. The evaluation process has produced feedback that suggests ways to significantly improve starfield interfaces and the interaction process to improve their learnability and usability. The study also gave us clear indication of additional potential uses of starfield visualizations that can be exploited by further functionality and interface development. We report on resulting implications for the design and use of starfield visualizations that will impact their graphical interface features, their use for managing data quality and their potential for various forms of visual data mining. Although the current implementation and analysis focuses on the collection of a physical library, the most important contributions of our work will be in digital libraries, in which volume, complexity and dynamism of collections are increasing dramatically and tools are needed for visualization and analysis

Extracting corpus specific knowledge bases from Wikipedia

Thesauri are useful knowledge structures for assisting information retrieval. Yet their production is labor-intensive, and few domains have comprehensive thesauri that cover domain-specific concepts and contemporary usage. One approach, which has been attempted without much success for decades, is to seek statistical natural language processing algorithms that work on free text. Instead, we propose to replace costly professional indexers with thousands of dedicated amateur volunteers--namely, those that are producing Wikipedia. This vast, open encyclopedia represents a rich tapestry of topics and semantics and a huge investment of human effort and judgment. We show how this can be directly exploited to provide WikiSauri: manually-defined yet inexpensive thesaurus structures that are specifically tailored to expose the topics, terminology and semantics of individual document collections. We also offer concrete evidence of the effectiveness of WikiSauri for assisting information retrieval