Accounting for Obsolescence: An Evaluation of Current NIPA Practice

This work raises questions about what obsolescence is and whether it is properly accounted for in BEA's methodology

Problems Inherent in Multi-Service Delivery Units

Like Alice, the field of social work in general, and the social service delivery system in particular, seems to be going through a confusing state, lacking direction. Just as the Cat suggests to Alice that any direction would get her somewhere over time, so the diverse social service delivery systems(1) have, in recent years, moved off in a particular direction (methodologically) only to return to step one and then set off again. Various fads have seemed to provide the needed answers. In time, however, they served only to create a series of new questions with corresponding dilemmas. In the last few years both the literature and practice have suggested that the integration of the service function would provide the long-sought methodological break-through. The instrument to attain the goal of integration would be multi-service delivery units of one form or another. It is the purpose of this paper to trace these developments and to examine scme of the problems inherent in multi-service delivery units as a mode of integration of the service delivery task. The various approaches are presented here in a quasi historical and linear fashion, with one system following an another. In practice, the movement from one mode to another was neither as direct nor as rational. They are presented in this manner to try to underline the antecedinal relationship inherent in the search for an organization form which constitutes effective service delivery. Further, the models are by necessity generalizations of practice and my not fully describe any one setting. Still it is hoped one may derive a sense of the difficulties faced in the development of new operational types of service delivery

Denominators of Eisenstein cohomology classes for GL_2 over imaginary quadratic fields

We study the arithmetic of Eisenstein cohomology classes (in the sense of G. Harder) for symmetric spaces associated to GL_2 over imaginary quadratic fields. We prove in many cases a lower bound on their denominator in terms of a special L-value of a Hecke character providing evidence for a conjecture of Harder that the denominator is given by this L-value. We also prove under some additional assumptions that the restriction of the classes to the boundary of the Borel-Serre compactification of the spaces is integral. Such classes are interesting for their use in congruences with cuspidal classes to prove connections between the special L-value and the size of the Selmer group of the Hecke character.Comment: 37 pages; strengthened integrality result (Proposition 16), corrected statement of Theorem 3, and revised introductio

Differential Equations for Periods and Flat Coordinates in Two Dimensionsional Topological Matter Theories

We derive directly from the N=2 LG superpotential the differential equations that determine the flat coordinates of arbitrary topological CFT's.Comment: 34

Interval appendectomy in perforated appendicitis

The treatment of the perforated appendix remains controversial, with the optimal timing of surgical intervention unclear. Previous studies have documented an increase in both minor and major complication rates in patients undergoing appendectomy for perforated appendicitis. We sought to evaluate the nonoperative therapy of perforated appendicitis followed by interval appendectomy. The charts of all children undergoing admission for appendicitis during a 10-year period (n = 480) were reviewed. Data were abstracted regarding patient presentation, laboratory and radiologic findings, operative and pathology reports, and postoperative course in those patients with perforated appendicitis (n = 104). Comparisons were made between patients undergoing primary appendectomy for perforated appendicitis (n = 87) and those treated with IV antibiotics and hydration and then scheduled for interval appendectomy 4 to 6 weeks following the acute event (n = 17). Treatment assignment was determined by the attending pediatric surgeon in a non-randomized fashion. No significant differences were seen between these two groups in days of antibiotic treatment, nasogastric decompression, and IV hydration. Additionally, total hospital days and cost did not differ significantly between the two groups (primary = 10.3 days and $10,550; interval = 13.3 days and$13,221, P = 0.11 and 0.21, respectively). The overall complication rates, 12.6% in the primary group and 5.9% in the interval group, also did not differ significantly, while the major complication rate (wound dehiscence, abscess, and small-bowel obstruction), 10% versus 0%, was significantly higher in the primary group as compared with the interval group. Our data demonstrate no significant disadvantage, and possibly an improvement in the major complication rate, with nonoperative treatment of perforated appendicitis followed by interval appendectomy. We suggest that this treatment modality should be considered when evaluating the child with perforated appendicitis.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47148/1/383_2004_Article_BF00171160.pd

Numerical convergence of the block-maxima approach to the Generalized Extreme Value distribution

In this paper we perform an analytical and numerical study of Extreme Value distributions in discrete dynamical systems. In this setting, recent works have shown how to get a statistics of extremes in agreement with the classical Extreme Value Theory. We pursue these investigations by giving analytical expressions of Extreme Value distribution parameters for maps that have an absolutely continuous invariant measure. We compare these analytical results with numerical experiments in which we study the convergence to limiting distributions using the so called block-maxima approach, pointing out in which cases we obtain robust estimation of parameters. In regular maps for which mixing properties do not hold, we show that the fitting procedure to the classical Extreme Value Distribution fails, as expected. However, we obtain an empirical distribution that can be explained starting from a different observable function for which Nicolis et al. [2006] have found analytical results.Comment: 34 pages, 7 figures; Journal of Statistical Physics 201

Classification of phase transitions and ensemble inequivalence, in systems with long range interactions

Systems with long range interactions in general are not additive, which can lead to an inequivalence of the microcanonical and canonical ensembles. The microcanonical ensemble may show richer behavior than the canonical one, including negative specific heats and other non-common behaviors. We propose a classification of microcanonical phase transitions, of their link to canonical ones, and of the possible situations of ensemble inequivalence. We discuss previously observed phase transitions and inequivalence in self-gravitating, two-dimensional fluid dynamics and non-neutral plasmas. We note a number of generic situations that have not yet been observed in such systems.Comment: 42 pages, 11 figures. Accepted in Journal of Statistical Physics. Final versio

Mathematics of Gravitational Lensing: Multiple Imaging and Magnification

The mathematical theory of gravitational lensing has revealed many generic and global properties. Beginning with multiple imaging, we review Morse-theoretic image counting formulas and lower bound results, and complex-algebraic upper bounds in the case of single and multiple lens planes. We discuss recent advances in the mathematics of stochastic lensing, discussing a general formula for the global expected number of minimum lensed images as well as asymptotic formulas for the probability densities of the microlensing random time delay functions, random lensing maps, and random shear, and an asymptotic expression for the global expected number of micro-minima. Multiple imaging in optical geometry and a spacetime setting are treated. We review global magnification relation results for model-dependent scenarios and cover recent developments on universal local magnification relations for higher order caustics.Comment: 25 pages, 4 figures. Invited review submitted for special issue of General Relativity and Gravitatio