Sea-Fog

DARKNESS was thick over the water as the destroyer 374 turned up its broad wake into the fog. The water was dark, broken only by an occasional white-cap as the wind and currents tormented it. The bridge chronometer showed half-an-hour past midnight when a mechanical voice broke from the squawk-box

A Change in Macroeconomic Thinking

Left to its own devices, Keynes felt that there was no way a free market system, even with downwardly flexible wages and prices, could guarantee full employment

MANAGING THE USER RELATIONSHIP IM INFORMATION SYSTEMS DEVELOPMENT PROJECTS: A TRANSACTION GOVERNANCE APPROACH

This paper compares the effectiveness of two mechanisms for governing the relationship between an information systems development team and the new system\u27s users. This relationship is traditionally governed using phased commitments and user involvement. Drawing on the organizational economics literature, the paper proposes a new view in which a project is characterized as a transaction, or an exchange, between IS and the users. Two alternatives for governing this exchange, one based on explicit, classical contracting and the other relying more on implicit, social contracting, are hypothesized to be differentially effective in governing exchanges of low or high difficulty, respectively. The model is explored in a field study at a single site and found to be supported, indicating that more rigorous tests of the model are warranted

Pseudo-monoenergetic x-ray diffraction measurements using balanced filters for coherent-scatter computed tomography

In the treatment of kidney stones, knowing stone composition has been established as an important aid to the understanding of stone formation and in preventing recurrences, particularly the composition of the initial “core” of the stone. Traditionally, stone composition has come from laboratory techniques such as infrared spectroscopy and x-ray diffraction. These methods require taking multiple samples of excised stone fragments and powdering them - losing structural information in the process, and therefore the specific core composition. Coherent-scatter computed tomography (CSCT) is a method of non-destructive “composition” imaging based on measurements of diffraction patterns from tissues. Use of an x-ray tube degrades scatter-pattern angular resolution due to the x-ray spectral width, making it difficult to uniquely identify some materials. The use of two transmission filters with similar atomic numbers (balanced “Ross filters”) to generate pseudo-monoenergetic scatter patterns of common kidney stone components is described as it applies to CSCT. We show that an analysis of angular-blur mechanisms reveals that focal spot size and beam width are the most important factors determining Bragg-peak width when erbium and thulium balanced filters are used. A Bragg-peak RMS angular width of approximately 0.14° (relative width of 3% at 5° scatter angle) can be achieved, reducing peak-overlap in the scatter functions of common kidney stone constituents. CSCT is capable of producing 3-D material-distribution maps. In previous studies, such maps were of relative material density. We describe a theoretical method to generate absolute (g/cm3) mass-density distributions. Balanced-filter CSCT improves scatter-function angular resolution and allows for the measurement of common kidney-stone constituents with non-overlapping peaks

randomLCA: An R Package for Latent Class with Random Effects Analysis

Latent class is a method for classifying subjects, originally based on binary outcome data but now extended to other data types. A major difficulty with the use of latent class models is the presence of heterogeneity of the outcome probabilities within the true classes, which violates the assumption of conditional independence, and will require a large number of classes to model the association in the data resulting in difficulties in interpretation. A solution is to include a normally distributed subject level random effect in the model so that the outcomes are now conditionally independent given both the class and random effect. A further extension is to incorporate an additional period level random effect when subjects are observed over time. The use of the randomLCA R package is demonstrated on three latent class examples: classification of subjects based on myocardial infarction symptoms, a diagnostic testing approach to comparing dentists in the diagnosis of dental caries and classification of infants based on respiratory and allergy symptoms over time