The Role of Nitrogen and Phosphorus in the Growth, Toxicity, and Distribution of the Toxic Cyanobacteria, Microcystis aeruginosa

Microcystis aeruginosa is among the most common harmful algal-blooming species in the world. Potent microcystins released by M. aeruginosa have been linked to liver failure and death in aquatic mammals, like the endangered California sea otter, and provide a serious public health risk to humans. Once characterized as a freshwater problem, M. aeruginosa is expanding on a global scale, making persistent returns in freshwater, brackish, and coastal marine ecosystems. Though commonly observed dominating aquatic ecosystems in low N:P atomic ratios less than 44:1, the reliability of N:P ratios as a tool for managing and predicting M. aeruginosa blooms is explored through analyzing the specific roles of N and P in influencing its growth, toxicity, and distribution. N is far more influential than P in regulating growth, toxicity, and distribution of M. aeruginosa, and ammonium (NH4+) is the most bioavailable form of N to M. aeruginosa. Thus, as the proportion of NH4+ increases in total N concentrations, phytoplankton communities shift towards M. aeruginosa dominance. Changing concentrations of N and P have been observed to influence the N:P ratio values that provide optimal growth, with higher N and P concentrations providing a higher range of N:P ratios in which optimal growth can occur. Furthermore, local environmental factors can influence M. aeruginosa presence more than nutrient availability, with M. aeruginosa favoring extended dry seasons and warmer surface water temperatures between 25-30°C. Management of M. aeruginosa should focus on regulating concentrations of N and P, including NH4+, instead of using N:P ratios as a management tool. Furthermore, management decisions may be unique depending on local environmental factors

Sensemaking In Information Systems: Toward A Sensemaking Inquiring System

Complexity and uncertainty have long been problems for organizations of all types. Organizational members do not do a very good job of dealing with the complexity and uncertainty as research shows that when faced with complex situations humans often turn to the same sources of information repeatedly (a practice that will eventually betray them), and/or reduce the amount of scanning that they do (Weick 1995; Boyd and Fulk 1996). Organizations often turn to information systems to help them deal with the complexity, but they often take a techno-centric view of knowledge that does not incorporate the human qualities needed for unstructured decisions (Malhotra 1997; Courtney 2001; Malhotra 2001). Additionally, there are times when the information systems that we are using may hinder the processes of dealing with the complexity (Weick and Meader 1993). Weick\u27s (1995) concept of sensemaking is believed to help us to deal with this complexity. In his work with Meader (1993) he wonders what the effects of a sensemaking support system would have, but he does not have the answer because they state that it has not been asked. This dissertation answers the call of Weick and Meader as well as other scholars that have called for sensemaking and human intuition to be included in our information systems. This is accomplished by viewing sensemaking from an inquiring systems perspective (Churchman 1971) to develop a kernel theory that will be used in the context of design science to develop design requirements and principles for a sensemaking system. These design principles are then used to build an instantiation of the system in the form of SenseMan, a system designed to help a local government agency deal with complexity in the context of software updates. Finally the design is evaluated for its effectiveness in dealing with the complexity of in this context using both quantitative and qualitative methods

Letter from Parrish to Roach, January 11, 1974

A letter from James M. Parrish, Dean of the College of Business administration to W.J. Roach, Chairman, Department of Language and Literature. The letter congratulates Mr. Roach and the Halyard staff on the first edition of the campus newspaper

Buoyancy Instabilities in a Weakly Collisional Intracluster Medium

The intracluster medium of galaxy clusters is a weakly collisional, high-beta plasma in which the transport of heat and momentum occurs primarily along magnetic-field lines. Anisotropic heat conduction allows convective instabilities to be driven by temperature gradients of either sign, the magnetothermal instability (MTI) in the outskirts of non-isothermal clusters and the heat-flux buoyancy-driven instability (HBI) in their cooling cores. We employ the Athena MHD code to investigate the nonlinear evolution of these instabilities, self-consistently including the effects of anisotropic viscosity (i.e. Braginskii pressure anisotropy), anisotropic conduction, and radiative cooling. We highlight the importance of the microscale instabilities that inevitably accompany and regulate the pressure anisotropies generated by the HBI and MTI. We find that, in all but the innermost regions of cool-core clusters, anisotropic viscosity significantly impairs the ability of the HBI to reorient magnetic-field lines orthogonal to the temperature gradient. Thus, while radio-mode feedback appears necessary in the central few tens of kpc, conduction may be capable of offsetting radiative losses throughout most of a cool core over a significant fraction of the Hubble time. Magnetically-aligned cold filaments are then able to form by local thermal instability. Viscous dissipation during the formation of a cold filament produces accompanying hot filaments, which can be searched for in deep Chandra observations of nearby cool-core clusters. In the case of the MTI, anisotropic viscosity maintains the coherence of magnetic-field lines over larger distances than in the inviscid case, providing a natural lower limit for the scale on which the field can fluctuate freely. In the nonlinear state, the magnetic field exhibits a folded structure in which the field-line curvature and field strength are anti-correlated.Comment: 20 pages, 20 figures, submitted to ApJ; Abstract abridge

Buoyant Bubbles in Intracluster Gas: Effects of Magnetic Fields and Anisotropic Viscosity

Recent observations by Chandra and XMM-Newton indicate there are complex structures at the cores of galaxy clusters, such as cavities and filaments. One plausible model for the formation of such structures is the interaction of radio jets with the intracluster medium (ICM). To investigate this idea, we use three-dimensional magnetohydrodynamic simulations including anisotropic (Braginskii) viscosity to study the effect of magnetic fields on the evolution and morphology of buoyant bubbles in the ICM. We investigate a range of different initial magnetic field geometries and strengths, and study the resulting x-ray surface brightness distribution for comparison to observed clusters. Magnetic tension forces and viscous transport along field lines tend to suppress instabilities parallel, but not perpendicular, to field lines. Thus, the evolution of the bubble depends strongly on the initial field geometry. We find toroidal field loops initially confined to the interior of the bubble are best able reproduce the observed cavity structures.Comment: 1 table, 10 figures, 29 pages. Accepted at ApJ. Figures with better quality are available at ApJ onlin

The Role of Gamification in Motivating User Participation in Requirements Determinations

The success of a project heavily relies on the quality of requirements determinations, which the systems are built upon. However, about 60% of project failures are due to weak requirements determinations. This weakness is due to poor communication and lack of stakeholder engagement. Understanding the factors that motivate user participation behaviors during requirements determinations will help to recognize how users will demonstrate positive behaviors and will be more engaged. However, empirical research on the factors that motivate participants during requirements determinations to engage and share their knowledge is still lacking. The purpose of this paper is to examine the motivational impact of gamification elements on user participation behaviors during requirements determinations. This paper presents an extended model of the theory of reasoned action. The extended model posits that gamification elements will influence user participation intentions indirectly through their effects on attitude and subjective norms

Power Issues in G2G E-Government Applications

This paper addresses a type of wicked problem in the design of information systems in the context of G2G e-Government information systems. These problems, called power issues, have all of the characteristics of wicked problems; however, they are differentiated from them because their roots are based in power. The Power Perspectives Framework from Bradshaw-Camball and Murray is utilized in the context of these G2G systems to provide a framework for the identification and classification of power issues and Courtney’s DSS paradigm is extended to assist in resolving them by incorporating the power perspective into the methodology

Towards a Taxonomy of Information Spillage and Leakage

Studies of information exposure are a cornerstone of information security research. Within the research realm of information exposure, the inadvertent exposure of information is a topic of particular interest. In the extent literature this phenomenon is often referred to as information leakage or information spillage. In this work in progress, we seek to understand the extent usage of these terms and to work towards a harmonized definition of both terms. We present a systematic review of literature detailing the prior use of both terms and the definitions put forward in the literature. Furthermore, we propose a framework for defining information spillage and information leakage based on the dimensions of user action and system behavior

Vice or Virtue? Exploring the Dichotomy of an Offensive Security Engineer and Government “Hack Back” Policies

In response to increasing cybersecurity threats, government and private agencies have increasingly hired offensive security experts: red-hat” hackers. They differ from the better-known “white-hat” hackers in applying the methods of cybercriminals against cybercriminals and counter or preemptively attacking, rather than focusing on defending against attacks. Often considered the vigilantes of the hacker ecosystem, they work under the same rules as would be hackers, attackers, hacktivists, organized cyber-criminals, and state-sponsored attackers—which can easily lead them into the unethical practices often associated with such groups. Utilizing the virtue (ethics) theory and cyber attribution, we argue that there exists a dichotomy among offensive security engineers, one that appreciates organizational security practices, but at the same time violates ethics in how to retaliate against a malicious attacker

Internet Use and Online Activities in U.S. States: Geographic Disparities and Socio-economic Influences

Attention in the digital divide research agenda is shifting gradually from material access of information and communication technologies (ICTs) to actual use of ICTs. As internet usage increases worldwide and online activities concomitantly expand in range and sophistication, it becomes essential to examine patterns and disparities of such usage. This paper examines geographic patterns and disparities along with influences of demographic, economic, and social factors on internet use in U.S. states. Our conceptual model of internet use posits associations of 21 traditional (socio-economic) as well as non-traditional independent variables (social capital, societal openness, innovation, infrastructure, and affordability) with dependent indicators of e-communication, e-commerce, e-education, e-entertainment, e-health, and telework. Age, race/ethnicity, innovation, urban location, managerial and scientific occupations, and social capital are found to predominantly influence internet use spanning a range of online activities. Policy implications of these findings are discussed taking cognizance of geographic disparities in internet use among the fifty states