Tracking Vector Magnetograms with the Magnetic Induction Equation

The differential affine velocity estimator (DAVE) developed in Schuck (2006) for estimating velocities from line-of-sight magnetograms is modified to directly incorporate horizontal magnetic fields to produce a differential affine velocity estimator for vector magnetograms (DAVE4VM). The DAVE4VM's performance is demonstrated on the synthetic data from the anelastic pseudospectral ANMHD simulations that were used in the recent comparison of velocity inversion techniques by Welsch (2007). The DAVE4VM predicts roughly 95% of the helicity rate and 75% of the power transmitted through the simulation slice. Inter-comparison between DAVE4VM and DAVE and further analysis of the DAVE method demonstrates that line-of-sight tracking methods capture the shearing motion of magnetic footpoints but are insensitive to flux emergence -- the velocities determined from line-of-sight methods are more consistent with horizontal plasma velocities than with flux transport velocities. These results suggest that previous studies that rely on velocities determined from line-of-sight methods such as the DAVE or local correlation tracking may substantially misrepresent the total helicity rates and power through the photosphere.Comment: 30 pages, 13 figure

PRODUCTIVITY AND THE ENACTMENT OF A MACRO CULTURE

This paper reports the puzzling results of a study which examined IT capital investment and productivity at three of the largest IT user sites in the U.S. for the period 1970-1990: Social Security Administration (SSA), Internal Revenue Service (IRS), and the Federal Bureau of Investigation (FBI). Based on detailed IT investment, employment, and output data over twenty years, we found that only one agency had achieved significant productivity benefits, a second agency had modest results, and a third agency achieved no results whatever. These results cannot be explained by traditional theories of productivity of how productivity is produced. We argue that IT-induced productivity results not simply from strategic choice, nor the operation of the invisible hand in the market place, nor simply from keen managers adjusting their organizations to an "objective" environment. Instead we propose instead a new theory in which productivity benefits derive from a larger macro-culture enacted by powerful institutions in an organizational field. We extend this analysis to the larger economy and examine how this new theory helps us understand recent claims that IT is finally having positive productivity benefits at the sector level, and also helps us understand how the current fascination with reengineering and downsizing may be a self-fulfilling prophecy.Information Systems Working Papers Serie

Managing the patient with osteogenesis imperfecta: a multidisciplinary approach

Osteogenesis imperfecta (OI) is a heterogeneous heritable connective tissue disorder characterized by low bone density. The type and severity of OI are variable. The primary manifestations are fractures, bone deformity, and bone pain, resulting in reduced mobility and function to complete everyday tasks. OI affects not only the physical but also the social and emotional well-being of children, young people, and their families. As such, medical, surgical, and allied health professionals' assessments all play a role in the management of these children. The multidisciplinary approach to the treatment of children and young people living with OI seeks to provide well-coordinated, comprehensive assessments, and interventions that place the child and family at the very center of their care. The coordinated efforts of a multidisciplinary team can support children with OI to fulfill their potential, maximizing function, independence, and well-being

Information Technology and Occupational Structure

A central tenet of much popular and scholarly literature is that computers -and more broadly speaking "information systems"- bring about significant change in organizations. Some scholars focus on changes in organizational structure- the division of labor and its coordination through authority and power (Blau, 1976; Danziger, et. d., 1982; Laudon, 1976; 1986; Keen 1981; Kling and Iacono, 1984; Orlikowski and Robey, 1991; Robey, 1981; Walton, 1989; Barley 1986; 1990) . Others focus on IT induced changes in the design of work (Zuboff, 1984; Bikson, et. al., 1985: Kraut, et. al., 1987; Sproull and Kiesler, 199 1; Turner, 1984; Iacono and Kling, 1987). Still others have argued that IT significantly alters occupational structure in organizations--the distribution of employment among occupations and skill classes of workers (Braverman, 1984; Kling and Turner, 1987; Berndt, et. al., 1992; Howell and W e , 1993; Cyert and Mowry, 1988; 1989). In general, the impact of IT on occupational structure of firms and organizations is a neglected area of empirical research despite the fact that scholars have strong opinions, and convincing theories, about such occupational shifts. In this paper we report the results of a twenty year longitudinal study of occupational structure in three of the largest and most intensive organizational users of IT in the United States. For benchmarking purposes we also examine occupational change at the aggregate society level and in the federal government sector over a twenty year period. The results of our research question the claim that IT brings about significant change in occupational structure. While the organizations we examine did experience significant change in occupational structure during periods of intense computerization, these changes did not conform to theoretical predictions and they were inconsistent from one organization to another. We conc1ude that organizational occupational structures are quite stable in the face of massive IT change and claims that IT brings about "revo1utionaryâ changes in organizational structure have little empirical foundation even though there may be isolated cases where such rapid and drastic changes do occur.Information Systems Working Papers Serie

The Regularizing Capacity of Metabolic Networks

Despite their topological complexity almost all functional properties of metabolic networks can be derived from steady-state dynamics. Indeed, many theoretical investigations (like flux-balance analysis) rely on extracting function from steady states. This leads to the interesting question, how metabolic networks avoid complex dynamics and maintain a steady-state behavior. Here, we expose metabolic network topologies to binary dynamics generated by simple local rules. We find that the networks' response is highly specific: Complex dynamics are systematically reduced on metabolic networks compared to randomized networks with identical degree sequences. Already small topological modifications substantially enhance the capacity of a network to host complex dynamic behavior and thus reduce its regularizing potential. This exceptionally pronounced regularization of dynamics encoded in the topology may explain, why steady-state behavior is ubiquitous in metabolism.Comment: 6 pages, 4 figure

Speeding up gate operations through dissipation

It is commonly believed that decoherence is the main obstacle to quantum information processing. In contrast to this, we show how decoherence in the form of dissipation can improve the performance of certain quantum gates. As an example we consider the realisations of a controlled phase gate and a two-qubit SWAP operation with the help of a single laser pulse in atom-cavity systems. In the presence of spontaneous decay rates, the speed of the gates can be improved by a factor 2 without sacrificing high fidelity and robustness against parameter fluctuations. Even though this leads to finite gate failure rates, the scheme is comparable with other quantum computing proposals