Identifying factors that shape the spatial distribution of genetic variation within and among natural populations is crucial to understanding many population> and landscape>level processes. In this study, I characterize the strength and extent of spatial genetic structure in Oenothera harringtonii (Onagraceae), an insect>pollinated, gravity>dispersed herb endemic to the grasslands of...
Habitat fragmentation can alter the conditions of natural plant populations, introducing novel selective pressures. The ability of a population to respond to environmental change can be inferred by assessing the population’s genetic diversity and the heritability of traits thought to be under selection.
Two experiments were conducted to assess the germination, growth, and survival of Cirsium pitcheri Torr. ex Eaton T & G in the Chicagoland region. The first experiment involved growing seeds from various native populations to determine tolerance for the current Chicagoland climate. The second experiment tested three of the populations...
Pollination is a reproductive necessity in the majority of the world’s flowering plants. Pollen limitation threatens plant reproduction, particularly in self-incompatible species. Although assessing pollen limitation usually requires pollen supplementation experiments, alternative methods support the findings of traditional pollen supplementation experiments.
Pollination is a reproductive necessity in the majority of the world’s flowering plants. Pollen limitation threatens plant reproduction, particularly in self-incompatible species. Although assessing pollen limitation usually requires pollen supplementation experiments, alternative methods support the findings of traditional pollen supplementation experiments.
Past efforts to reintroduce the native legume species Desmodium glutinosum and Lespedeza violacea into restored woodlands have not produced self-sustaining populations. Proposed factors preventing reintroduction include herbivory, persistent environmental effects of invasive shrubs, poor performance of commercial Rhizobium inoculants, and competitive displacement associated with elevated nitrogen availability. To address these...
Current ecological restoration efforts seek to restore a target community, maximize biodiversity or provide habitat for rare species. In practice, restoration ecology is often initiated and sustained without knowledge or reverence to the belowground ecosystem processes, though these processes often subtend the long-term sustainability of aboveground and belowground ecological communities.
The underutilized tropical fruit tree, “cempedak” (Artocarpus integer (Thunb.) Merr. , Moraceae), is a major crop in Malaysia but the distribution of genetic diversity in the crop and its putative wild progenitor, “bangkong” (Artocarpus integer var. silvestris Corner), have not been studied. To investigate the diversity and origins of cempedak,...
Acoustic emission (AE) testing was deployed on details of two large steel Interstate Highway bridges: one cantilever through-truss and one trapezoidal box girder bridge. Quantitative measurements of activity levels at known and suspected crack locations were made by monitoring AE under normal service loads (e.g., live traffic and wind). AE...
Scour is by far the primary cause of bridge failures in the United States. Scour and other hydraulic effects are particularly threatening because the deterioration is often invisible, hidden beneath turbid water. Many scour monitoring methods attempt to measure the development of scour pockets themselves. However, this is difficult due...
Acoustic emission (AE) testing was used to identify the source of audible “bangs” generated during opening and closing of a large, double-leaf rolling-lift bascule bridge. The data were analyzed using a combination of well-established AE
techniques, including first hit analysis (FHA), planar location analysis, and linear location analysis. The FHA...
Kosnik, D. E., Northwestern University . Infrastructure Technology Institute, Department of Civil Environmental Engineering, Robert R. McCormick School of Engineering Applied Science. (2008). A new approach to acoustic emission testing of difficult-to-reach steel bridge details. Evanston, Illinois: Infrastructure Technology Institute/Department of Civil & Environmental Engineering.
This paper describes application of AE monitoring techniques to localize the sources of large noises in civil structures. These noises occur during operation of moveable portions of a structure in such things as lift bridges and moveable sports stadium roofs. The use of straightforward AE monitoring techniques can provide clear...
This report includes the findings of acoustic emission (AE) tests on the Fremont tied arch bridge in Portland Oregon conducted by research engineers from the Infrastructure Technology Institute of Northwestern University on March 24th, 1997.
This technical report shows the findings of acoustic emission and strain gage monitoring tests conducted by research engineers of Infrastructure Technology Institute from Northwestern University on April 18, 1997 in Sacramento, California.
Current bridge condition determination is based almost entirely on the use of visual inspection. This approach to bridge inspection provides data that is subjective and not traceable. Nondestructive evaluation (NDE) is a tool that in actuality is little used on bridges, but could eliminate much of the subjectivity of the...
A remote global monitoring system is being operated on a 65 year old lift bridge in Sturgeon Bay Wisconsin. The system uses both strain gages and clinometers to continuously monitor the "health" of the fracture critical components of the bridge. Ruggedized miniaturized data loggers are locally mounted on the structure...
This report shows the results of acoustic emission (AE) monitoring, and provides additional information on the nature of the ultrasonic indications in the north east trunnion shaft.
The finite element method is used to investigate failure mechanisms in pin-hanger connection in aging highway bridges. Bridge pins and hangers are typically considered as critical elements whose failure may result in partial or entire collapse of the structure. The primary function of a pin-hanger connection is to allow for...