16 research outputs found
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Conifer establishment from seed on tephra deposits from the 1980 eruptions of Mount St. Helens, Washington
Information concerning the factors controlling seedling establishment on tephra deposits (airfall volcanic ejecta) is limited. The establishment and growth of six coniferous species, Abies amabills (Dougl.) Forbes (Pacific silver fir), A. procera Rehd. (noble fir), Pinus monticola Dougl. (western white pine), P. Contorta Dougl. (lodgepole pine), Pseudotsuga menziesii (Mirb.) Franco (Douglas-fir) and Tsuga heterophylla (Raf.) Sarg. (western hemlock) are assessed as a function of: 1) depth of tephra deposit, 2) condition of tephra surface crust, and 3) availability of shade on seedbed. In October 1980, seeds were planted on four sites 20 km northeast of Mount St. Helens, Washington in a split-split plot design which incorporated plantings on both tephra deposited May 18 and pre-eruption soil. All six species established from seed on tephra deposits less than 20 cm deep. Cultivation of the tephra surface crust yielded more established seedlings than either total removal of tephra deposit or untreated tephra. Where differences between species were significant, Pseudotsuga menziesii was tallest and Tsuga heterophylla the shortest of the species tested. Seedlings grown on tephra were generally shorter than those grown on underlying soil, regardless of surface treatment. The principal factors affecting establishment in this study were: 1) loss of seed prior to germination, 2) failure of germinating seeds to penetrate the tephra surface crust, and 3) the occurrence of extended drought and/or extreme surface temperatures
International Spread of Multidrug-resistant Salmonella Schwarzengrund in Food Products
This serovar was isolated from persons, food, and food animals in Thailand, Denmark, and the United States
Improving resolution of public health surveillance for human Salmonella enterica serovar Typhimurium infection: 3 years of prospective multiple-locus variable-number tandem-repeat analysis (MLVA)
<p>Abstract</p> <p>Background</p> <p>Prospective typing of <it>Salmonella enterica </it>serovar Typhimurium (STM) by multiple-locus variable-number tandem-repeat analysis (MLVA) can assist in identifying clusters of STM cases that might otherwise have gone unrecognised, as well as sources of sporadic and outbreak cases. This paper describes the dynamics of human STM infection in a prospective study of STM MLVA typing for public health surveillance.</p> <p>Methods</p> <p>During a three-year period between August 2007 and September 2010 all confirmed STM isolates were fingerprinted using MLVA as part of the New South Wales (NSW) state public health surveillance program.</p> <p>Results</p> <p>A total of 4,920 STM isolates were typed and a subset of 4,377 human isolates was included in the analysis. The STM spectrum was dominated by a small number of phage types, including DT170 (44.6% of all isolates), DT135 (13.9%), DT9 (10.8%), DT44 (4.5%) and DT126 (4.5%). There was a difference in the discriminatory power of MLVA types within endemic phage types: Simpson's index of diversity ranged from 0.109 and 0.113 for DTs 9 and 135 to 0.172 and 0.269 for DTs 170 and 44, respectively. 66 distinct STM clusters were observed ranging in size from 5 to 180 cases and in duration from 4 weeks to 25 weeks. 43 clusters had novel MLVA types and 23 represented recurrences of previously recorded MLVA types. The diversity of the STM population remained relatively constant over time. The gradual increase in the number of STM cases during the study was not related to significant changes in the number of clusters or their size. 667 different MLVA types or patterns were observed.</p> <p>Conclusions</p> <p>Prospective MLVA typing of STM allows the detection of community outbreaks and demonstrates the sustained level of STM diversity that accompanies the increasing incidence of human STM infections. The monitoring of novel and persistent MLVA types offers a new benchmark for STM surveillance.</p> <p>A part of this study was presented at the MEEGID × (Molecular Epidemiology and Evolutionary Genetics of Infectious Diseases) Conference, 3-5 November 2010, Amsterdam, The Netherlands</p
Toward a theory of repeat purchase drivers for consumer services
The marketing discipline’s knowledge about the drivers of service customers’ repeat purchase behavior is highly fragmented. This research attempts to overcome that fragmented state of knowledge by making major advances toward a theory of repeat purchase drivers for consumer services. Drawing on means–end theory, the authors develop a hierarchical classification scheme that organizes repeat purchase drivers into an integrative and comprehensive framework. They then identify drivers on the basis of 188 face-to-face laddering interviews in two countries (USA and Germany) and assess the drivers’ importance and interrelations through a national probability sample survey of 618 service customers. In addition to presenting an exhaustive and coherent set of hierarchical repeat-purchase drivers, the authors provide theoretical explanations for how and why drivers relate to one another and to repeat purchase behavior. This research also tests the boundary conditions of the proposed framework by accounting for different service types. In addition to its theoretical contribution, the framework provides companies with specific information about how to manage long-term customer relationships successfully