Kinematically Extended Continuum Theories: Correlation Between Microscopical Deformation and Macroscopical Strain Measures

The present work investigates the correlation between macrocscopical deformation modes and microscopical deformation modes. Thereby, the macroscopical deformation is represented by the strain-like quantities of the according macroscopical continuum theory while the microscopical deformation is expressed in the form of a Taylor series expansion. The use of an energy criterion makes it possible to derive a quantitative relation between microscopical and macroscopical deformation. The procedure is applied to different kinematically extended continuum theories on the macroscopical level. The investigation may help to select an optimal macroscopical continuum theory instead of choosing a theory based on phenomenological observations, whereby the optimal theory ist that one, which reflects the microscopical deformation behaviour best. The microscopical deformation behaviour depends on the topology of the microstructure under consideration. Thus, the optimal theory is affected by the topology of the microstructure

A Systematic Treatment of Acacia coulteri (Fabaceae, Mimosoideae) and Similar Species in the New World

Detailed descriptions, habitat preferences, geographic ranges, and representative specimens are given for the 13 taxa of the Acacia coulteri group from Mexico, Central America, and the southwestern United States. These species form a distinct group within Acacia series Vulgares, lacking prickles and usually having persistent stipules. A principal components analysis (PCA) of vegetative and floral features shows that the specimens examined form discrete units in plots of the first three principal components. The groups established by PCA mostly coincide with previously described species. The taxa within this group are phenetically similar, sharing many morphological features. These data also suggest that there is occasional gene flow between species, but that hybrids are not common. About half the species have restricted ranges (A. compacta, A. dolichostachya, A. durangensis, A. millefolia, A. russelliana, A. sericea, and A. willardiana), but the remainder are wide-ranging, either from Oaxaca and Puebla north into central and northern Mexico (A. acatlensis, A. coulteri, A. mammifera, and A. salazari), or south into Central America (A. centralis and A. usumacintensis)

Vascular Flora of Hooper Branch Savanna Nature Preserve, Iroquois County, Illinois

INHS Technical Report prepared for Illinois Department of Natural Resources, Division of Natural Heritag

Claytonia virginica L.

https://thekeep.eiu.edu/herbarium_specimens_byname/20816/thumbnail.jp

Seismicity of the central Afar rift and implications for Tendaho dam hazards

Temporary broadband seismic networks deployed from 2007 to 2011 around the Afar triple junction of the East African Rift System provide insights into seismicity patterns of the actively deforming crust around the 1.86 km3 impounded lake system behind the Tendaho dam. The observed seismicity correlates well with the active magmatic centres around central Afar. The area around the dam site is characterized by a network of intersecting NNE- and NW-trending faults. Seismicity clusters observed in the specified time interval indicate that both fault sets are active and are potential sources of seismogenic hazards. The dam neighbourhood is naturally active and it is a challenge to associate the observed seismic activity to either a change in magmato-tectonic conditions or attribute it to the influence of reservoir load. It is evident that the dam region experi- ences high levels of seismic and volcano-tectonic unrest, regardless of the origin of the activity. The spatial overlap of narrow zones of crustal seismicity and upper mantle low velocity zones observed in S-wave tomography models suggests that melt production zones guide the distribution of strain during continental rupture. Given its volcanically and seismically active setting, the Tendaho dam site and the surrounding region require continuous monitoring for the safety of downstream popu- lations and development infrastructures in the Afar National Regional State of Ethiopia

Density Dependence, Whitebark Pine Decline and Vital Rates of Grizzly Bears in The Greater Yellowstone Ecosystem

Recent evidence suggests annual population growth of the grizzly bear (Ursus arctos) population in the Greater Yellowstone Ecosystem has slowed from 4.1–7.6 percent during 1983–2001 to 0.3–2.2 percent during 2002–2011. Substantial changes in availability of an important fall food has occurred over the past decade. Whitebark pine (Pinus albicaulis), a highly variable but important fall food source for grizzly bears, has experienced substantial mortality due to a mountain pine beetle (Dendroctonus ponderosae) outbreak that started in the early 2000s. Concurrent with changes in food resources, the grizzly bear population has reached high densities in some areas and has continued to expand, now occupying >50,000 km2. We tested research hypotheses to examine if changes in vital rates detected during the past decade were more associated with grizzly bear density versus a whitebark pine decline. We focused our assessment on known-fate data to estimate survival of cubs-of-the-year, yearlings, and independent bears (? 2 yrs) and reproductive transition of females from having no offspring to having cubs.  We observed a change in survival of independent bears between the periods of 1983–2001 and 2002–2012, which was mostly a function of increased male survival; female survival did not change. Cub survival and reproductive transition declined during the last decade and were associated with an index of grizzly bear density, which indicated increasing density over time. We found no support that the decline in these vital rates was associated with the index of whitebark decline

Influence of Whitebark Pine Decline on Fall Habitat Use and Movements of Grizzly Bears in the Greater Yellowstone Ecosystem

Seeds of whitebark pine (WBP; Pinus albicaulis) are a major food item for grizzly bears (Ursus arctos) in the greater Yellowstone ecosystem. Higher rates of bear mortality and bear-human conflicts are linked with low WBP productivity. Recently, infestations of mountain pine beetle (Dendroctonus ponderosae) have killed many mature, cone-bearing WBP trees. We investigated whether this decline caused bears to reduce their use of WBP and increase use of areas near humans. We used 52,332 GPS locations of 72 individuals (89 bear-years) monitored during fall (15 Aug–30 Sep) to examine temporal changes in habitat use and movements during 2000–2011. We calculated a Manley-Chesson (MC) index for selectivity of mapped WBP habitats for each individual within its 100% local convex hull home range, and determined dates of WBP use. One third of sampled grizzly bears had fall ranges with little or no mapped WBP habitat. Most other bears (72%) had a MC index > 0.5, indicating selection for WBP habitats. Over the study period, mean MC index decreased and median date of WBP use shifted about 1 week later. We detected no trends in movement indices over time. Outside of national parks, 78 percent of bears selected for secure habitat (areas ? 500 m from roads), but mean MC index decreased over the study period during years of good WBP productivity. The foraging plasticity of grizzly bears likely allowed them to adjust to declining WBP. However, the reduction in mortality risk associated with use of WBP habitat may be diminishing for bears in multiple-use areas

The development of multiple phases of superposed rifting in the Turkana Depression, East Africa: evidence from receiver functions

The Turkana Depression in Eastern Africa separates the elevated plateaus of East Africa to the south and Ethiopia-Yemen to the north. It remains unclear whether the Depression lacks dynamic mantle support, or if the entire East Africa region is dynamically supported and the Depression compensated isostatically by thinned crust. Also poorly understood is how Miocene-Recent extension has developed across the Depression, connecting spatially separated magmatic rift zones in Ethiopia and Kenya. Receiver function analysis is used to constrain Moho depth and bulk-crustal V P /V S ratio below new seismograph networks in the Depression, and on the northern Tanzania craton. Crustal thickness is ∼40 km below northern Uganda and 30–35 km below southern Ethiopia, but 20–30 km below most of the Depression, where mass-balance calculations reveal low elevations can be explained adequately by crustal thinning alone. Despite the fact that magmatism has occurred for 45 Ma across the Depression, more than 15 Ma before East African Rift (EAR) extension initiated, bulk crustal V P /V S across southern Ethiopia and the Turkana Depression (∼1.74) is similar to that observed in areas unaffected by Cenozoic rifting and magmatism. Evidence for voluminous lower crustal intrusions and/or melt, widespread below the Ethiopian rift and Ethiopian plateau to the north, is therefore lacking. These observations, when reviewed in light of high stretching factors (β ≤ 2.11), suggest Cenozoic extension has been dominated until recently by faulting and plate stretching, rather than magma intrusion, which is likely an incipient process, operating directly below seismically-active Lake Turkana. Early-stage EAR basins to the west of Lake Turkana, with associated stretching factors of β ≈ 2, formed in crust only moderately thinned during earlier rifting episodes. Conversely, ∼23 km-thick crust beneath the Kino Sogo Fault Belt (KSFB) has small offset faults and thin sedimentary strata, suggesting almost all of the observed stretching occurred in Mesozoic times. Despite the KSFB marking the shortest path between focused extensional zones to the north and south, seismicity and GPS data show that modern extension is localized below Lake Turkana to the west. Failed Mesozoic rift zones, now characterized by thinned crust and relatively refractory mantle lithosphere, are being circumnavigated, not exploited by EAR rifting