1,200 research outputs found
The Nationality of Theories
Keynote dialogue for 22nd IACCP World Congress, Reims, July 16, 201
Optical Continuum and Emission-Line Variability of Seyfert 1 Galaxies
We present the light curves obtained during an eight-year program of optical
spectroscopic monitoring of nine Seyfert 1 galaxies: 3C 120, Akn 120, Mrk 79,
Mrk 110, Mrk 335, Mrk 509, Mrk 590, Mrk 704, and Mrk 817. All objects show
significant variability in both the continuum and emission-line fluxes. We use
cross-correlation analysis to derive the sizes of the broad Hbeta-emitting
regions based on emission-line time delays, or lags. We successfully measure
time delays for eight of the nine sources, and find values ranging from about
two weeks to a little over two months. Combining the measured lags and widths
of the variable parts of the emission lines allows us to make virial mass
estimates for the active nucleus in each galaxy. The virial masses are in the
range 10^{7-8} solar masses.Comment: 24 pages, 16 figures. Accepted for publication in Ap
Revised Sources of Guidance Measures: Six Events and Demographic Controls
In this paper, we update the country-level scores of sources of guidance reported in Peterson and Smith (2008) across 61 countries and based on 7,982 respondents. These scores represent aggregate tendencies of the use of specific sources of guidance in a country and provide an alternative to value-based cultural measures. Based on role and cognition theories, sources include how roles, rules and norms influence decision making in six frequent organizational events that managers encounter. Scores are controlled for demographic effects of respondents’ age and gender, as well as for organizational characteristics, namely ownership, department and organizational types. We also provide correlations between the sources of guidance scores and Hofstede’s, GLOBE’s, and Schwartz’s dimension scores
Biodiversity Patterns of Littoral Tidal River Fishes in the Gulf Coastal Plain Region of Mississippi
Fish biodiversity patterns within littoral habitats of major tidal river systems of coastal Mississippi were examined. The biodiversity of littoral tidal river fishes varied meaningfully on several spatial scales in the Gulf Coastal Plain region of Mississippi. Fish diversity typically appeared higher in littoral channel habitats than in side-pond habitats of tidal river systems. Faunal representation by three core groups of littoral fishes (cyprinids, centrarchids, and fundulids) generally differed between side-pond and channel habitats, as well as among different tidal river systems. Some of the faunal variation among systems reflected biogeographic (east/west) trends, but most of the variation reflected system size-related patterns. Among-site similarity in fish assemblage composition reflected both site proximity and system size. Moreover, the degree of variability in assemblage composition increased with system size. Thus, regional assemblage patterns were generally most discernible on the landscape scale, rather than through historical congruence. This limited regional study of tidal river fish biodiversity improved our biogeographic understanding by revealing the importance of landscape-scale factors such as tidal river size and associated variation in the available species pool. Understanding landscape-scale environmental variation is key to explaining regional fish diversity patterns
Regional Patterns in the Otolith Chemistry of Juvenile Spotted Seatrout (\u3ci\u3eCynoscion nebulosus\u3c/i\u3e) Differ Under Contrasting Hydrological Regimes
The value of using otolith chemistry to characterize recruitment in terms of natal source regions depends on how consistently spatio-temporal variation can be resolved. The objective of this study was to compare regional classification patterns in the otolith chemistry of juvenile Spotted Seatrout (Cynoscion nebulosus) between two years experiencing disparate hydrological regimes, and separated by a five year interlude. Spatial patterns in the whole-otolith chemistry of juveniles of this estuarine-dependent species were compared between years using five otolith elements and two stable isotopes. Consistent size-related trends in uptake and deposition were evidenced by parallel ontogenetic relationships for six otolith variables. Nine natal regions were discerned equally well in both years; and region accounted for similar overall amounts of variation in the seven otolith variables in both years. However, the otolith variables did not distinguish the nine regions in the same manner in both years, and natal regions varied in how similar they were in otolith chemistry between years. Consequently, between-year cross-classification accuracy varied widely among regions, and geographic distance per se was unimportant for explaining regional patterns in otolith chemistry. Salinity correlated significantly with regional patterns in otolith chemistry in 2001, but not at all in 2006 when conditions were much drier. Regional patterns in individual otolith variables reflected either a general trend based on hydrology, a regional-local effect whereby geographically closer regions exhibited similar otolith chemistry, or a location-specific effect for which there was either no correlation in otolith concentration among regions between years, or a significant but individualistic relationship. In addition to elucidating limitations of using otolith chemistry to identify natal source regions or for tracking fish movements, knowing more about how and why otolith chemistry varies could be used to address specific questions about early recruitment dynamics, or to aid in the development of more reliable instruments for discerning natal source contributions
A Method for Revealing and Addressing Security Vulnerabilities in Cyber-physical Systems by Modeling Malicious Agent Interactions with Formal Verification
Several cyber-attacks on the cyber-physical systems (CPS) that monitor and control critical infrastructure were publically announced over the last few years. Almost without exception, the proposed security solutions focus on preventing unauthorized access to the industrial control systems (ICS) at various levels – the defense in depth approach. While useful, it does not address the problem of making the systems more capable of responding to the malicious actions of an attacker once they have gained access to the system. The first step in making an ICS more resilient to an attacker is identifying the cyber security vulnerabilities the attacker can use during system design. This paper presents a method that reveals cyber security vulnerabilities in ICS through the formal modeling of the system and malicious agents. The inclusion of the malicious agent in the analysis of an existing systems identifies security vulnerabilities that are missed in traditional functional model checking
Do Small, Patchy, Constructed Intertidal Oyster Reefs Reduce Salt Marsh Erosion As Well As Natural Reefs?
One ecological service that oyster reefs provide is stabilization of shorelines through reduced wave energy and erosion from boat traffic, storms, and predominant wind direction. Additionally, increasing sedimentation can enhance the growth of emergent marsh vegetation which further stabilizes unconsolidated sediments. A 21 mo study of constructed (with only 30-35% coverage) and natural oyster reefs in 3 bayous in the Grand Bay National Estuarine Research Reserve (NERR) suggested constructed reefs benefit this retrograding deltaic ecosystem. The marsh edge adjacent to all constructed reefs was less eroded (mean = 0.043 m) than edges adjacent to natural reefs (mean = 0.728 m), although all natural and constructed sites, regardless of bayou, illustrated large variations in marsh edge growth. The marsh edge in constructed sites in one bayou retreated more than in the other bayous, most likely due to its coarser sediments, greater boat traffic, and its apparent higher energy location within the landscape. By the end of this study, the ecological function of constructed oyster reefs in all bayous, as measured by marsh edge erosion reduction, was equivalent or exceeded the function in nearby natural oyster reefs. The physical structure of the reef further served to reduce erosion and marsh loss and this approach may be useful for management of a retrograding deltaic estuarine ecosystem like the Grand Bay NERR
Irrigation cost and return analysis : general information
File: Agri. Engr. 4 7/69/7M, 3/71/3.5M"A series of four UMC Guides provides a procedure for complete economic analysis of an irrigation system. Use this Guide with others on Annual Ownership Costs, Annual Operation Costs, and Cost and Return Analysis Summary. For Cash flow implications of irrigation investments, see UMC Guide 1694, 'Cash Flow Analysis of Irrigation and Land Grading Investments.'"--First pageMark Peterson and C. F. Cromwell Jr. (Department of Agricultural Engineering), and Herman Workman (Department of Agricultural Economics, College of Agriculture)Rev. 7/73/8
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