Joseph M. Smith

Singlet and triplet excited states of a pyramidalized alkene: Electron-energy-loss spectra, photoelectron spectra, and calculations of the excited states of tricyclo[3.3.3.03,7]undec-3(7)-ene

Abstract Spectroscopic consequences of alkene pyramidalization have been investigated by measuring the triplet and singlet excitation energies of the pyramidalized alkene, tricyclo[3.3.3.03,7]undec-3(7)-ene (1), and the unpyramidalized reference alkene, bicyclo[3.3.0]oct-1(5)-ene (2), using electron-energy-loss spectroscopy. The experimental excitation energies and intensities are compared with the results of density functional calculations that include configuration interaction and also with the results of CASPT2 calculations. The valence π,π* triplet and singlet states of 1 were found to be lower in energy than those of 2, by 0.7 and 1.1±0.2 eV, respectively. In general, pyramidalization in 1 results in smaller decreases in the energies of the Rydberg states than of the valence states. However, pyramidalization was found to have dramatic consequences on the relative ordering and intensities of the singlet Rydberg states, due to lower symmetry of 1, the change in the nature of the π and π* MOs in 1, and resulting changes in the mixing between valence and Rydberg excitations

NMR and molecular mechanics studies of the conformational dynamics of tricyclo[3.3.3.03,7]undecane derivatives

Dynamic NMR studies and molecular mechanics calculations both indicate that twisting about the C3-C7 bond facilitates flipping of the trimethylene bridge in the tricyclo[3.3.3.03.7]undecane ring system.

Quantifying Site-Specific Physical Heterogeneity Within an Estuarine Seascape

Quantifying physical heterogeneity is essential for meaningful ecological research and effective resource management. Spatial patterns of multiple, co-occurring physical features are rarely quantified across a seascape because of methodological challenges. Here, we identified approaches that measured total site-specific heterogeneity, an often overlooked aspect of estuarine ecosystems. Specifically, we examined 23 metrics that quantified four types of common physical features: (1) river and creek confluences, (2) bathymetric variation including underwater drop-offs, (3) land features such as islands/sandbars, and (4) major underwater channel networks. Our research at 40 sites throughout Plum Island Estuary (PIE) provided solutions to two problems. The first problem was that individual metrics that measured heterogeneity of a single physical feature showed different regional patterns. We solved this first problem by combining multiple metrics for a single feature using a within-physical feature cluster analysis. With this approach, we identified sites with four different types of confluences and three different types of underwater drop-offs. The second problem was that when multiple physical features co-occurred, new patterns of total site-specific heterogeneity were created across the seascape. This pattern of total heterogeneity has potential ecological relevance to structure-oriented predators. To address this second problem, we identified sites with similar types of total physical heterogeneity using an across-physical feature cluster analysis. Then, we calculated an additive heterogeneity index, which integrated all physical features at a site. Finally, we tested if site-specific additive heterogeneity index values differed for across-physical feature clusters. In PIE, the sites with the highest additive heterogeneity index values were clustered together and corresponded to sites where a fish predator, adult striped bass (Morone saxatilis), aggregated in a related acoustic tracking study. In summary, we have shown general approaches to quantifying site-specific heterogeneity.

Spatially Clustered Movement Patterns and Segregation of Subadult Chinook Salmon within the Salish Sea

AbstractWhile Pacific salmon are known for their extensive marine migrations, some species display much more limited alternative patterns, including residence within interior marine waters. To more clearly define the scale of movement of these residents, we used acoustic telemetry to track subadult Chinook Salmon Oncorhynchus tshawytscha caught in and released from discrete areas of the Salish Sea. Their movements were determined from detections at fixed receivers in central Puget Sound, Admiralty Inlet, the San Juan Islands, and the Strait of Juan de Fuca. Cluster analysis of the detections indicated four groups, with much less commonality of movement than might be inferred from the proximity of the tagging locations, which were only tens of kilometers apart. For example, none of the salmon tagged in central Puget Sound were detected in the San Juan Islands and vice versa. Thus, Chinook Salmon occupying central Puget Sound and the San Juan Islands may exhibit different distributions, extents of movement,...

Seasonal Movement Patterns of Striped Bass (Morone saxatilis) in Their Nonnative Range

Movement dynamics of nonnative species can change in new environments and differ from native populations. It has been more than 100xa0years since striped bass (Morone saxatilis) were introduced to the Sacramento-San Joaquin River system in California from the US east coast. Acoustic telemetry from 2011 to 2015 was used to examine striped bass seasonal residence patterns in their nonnative range across three regions—bay, delta and rivers, and the effect of fish length and release river (Sacramento River [SR] vs. Feather River [FR]) on movement. In spring, SR striped bass (nu2009=u200952) increased travel speed by 39% and river residence by 63% relative to other seasons, which is consistent with spawning migrations. In summer, SR striped bass spent the most time in the bay (meanu2009=u200928.2u2009±u200930.9xa0days) relative to other seasons and across regions. In winter, 87% of striped bass werexa0detected in the delta over 42% in the bay and 25% in the river. Release river also affected movement behaviors—FR striped bass (nu2009=u200911) spent more time in the river in all seasons compared to SR bass. Striped bass with sufficient tag life (nu2009=u200917) traveled farther distances in 365xa0days (meanu2009=u20091248u2009±u2009405xa0km, range: 641–2212xa0km) with increasing fish length. Seasonal patterns observed appeared to follow seasonal prey sources throughout the San Francisco Estuary. Individual behaviors, however, were highly variable, and this flexibility may be an important trait that has allowed striped bass to persist in their nonnative range.