(Table 1) Estimated e-Nd(0) input calculated using the relative fraction of ODP Hole 105-647A amphibole grains originated from different provinces of the North America

Many marine radiogenic isotope records show both spatial and temporal variations, reflecting both the degree of mixing of distinct sources in the oceans and changes in the distribution of chemical weathering on the continents. However, changes in weathering and transport processes may themselves affect the composition of radiogenic isotopes released into seawater. The provenance of physically weathered material in the Labrador Sea, constrained through the use of Ar-Ar ages of individual detrital minerals, has been used to estimate the relative contributions of chemically weathered terranes releasing radiogenic isotopes into the Labrador Sea. A simple box-model approach for balancing observed Nd-isotope variations has been used to constrain the relative importance of localised input in the Labrador Sea, and the subsequent mixing of Labrador Sea Water into North Atlantic Deep-Water. The long-term pattern of erosion and deep-water formation around the North Atlantic seems to have been a relatively stable feature since 1.5 Ma, although there has been a dramatic shift in the nature of physical and chemical weathering affecting the release of Hf and Pb isotopes. The modelled Nd isotopes imply a relative decrease in water mass advection into the Labrador Sea between 2.4 and 1.5 Ma, accompanied by a decrease in the rate of overturning, possibly caused by an increased freshwater input into the Labrador Sea.

Miocene foraminiferal, bolboformid, dinoflagellate and diatom age calibrations for the northeastern North Atlantic

This study presents a new Miocene biostratigraphic synthesis for the high-latitude northeastern North Atlantic region. Via correlations to the bio-magnetostratigraphy and oxygen isotope records of Ocean Drilling Program and Deep Sea Drilling Project Sites, the ages of shallower North Sea deposits have been better constrained. The result has been an improved precision and documentation of the age designations of the existing North Sea foraminiferal zonal boundaries of King (1989) and Gradstein and Bäckström (1996). All calibrations have been updated to the Astronomically Tuned Neogene Time Scale (ATNTS) of Lourens et al. (2004). This improved Miocene biozonation has been achieved through: the updating of age calibrations for key microfossil bioevents, identification of new events, and integration of new biostratigraphic data from a foraminiferal analysis of commercial wells in the North Sea and Norwegian Sea. The new zonation has been successfully applied to two commercial wells and an onshore research borehole. At these high latitudes, where standard zonal markers are often absent, integration of microfossil groups significantly improves temporal resolution. The new zonation comprises 11 Nordic Miocene (NM) Zones with an average duration of 1 to 2 million years. This multi-group combination of a total of 92 bioevents (70 foraminifers and bolboformids; 16 dinoflagellate cysts and acritarchs; 6 marine diatoms) facilitates zonal identification throughout the Nordic Atlantic region. With the highest proportion of events being of calcareous walled microfossils, this zonation is primarily suited to micropaleontologists. A correlation of this Miocene biostratigraphy with a re-calibrated oxygen isotope record for DSDP Site 608 suggests a strong correlation between Miocene planktonic microfossil turnover rates and the inferred paleoclimatic trends. Benthic foraminifera zonal boundaries appear to often coincide with Miocene global sequence boundaries. The biostratigraphic record is punctuated by four main stratigraphic hiati which show variation in their geographic and temporal extent. These are related to the following regional unconformities: basal Neogene, Lower/Middle Miocene ("mid-Miocene unconformity"), basal Upper Miocene and basal Messinian unconformities. Further coring of Neogene sections in the North Sea and Norwegian Sea may better constrain their extent and their effect on the biostratigraphic record.

Comparison of multi-year Ka-band propagation characteristics at four sites in North America and Europe

Tropospheric phenomena such as clouds and mainly rain cause higher attenuation at Ka-band than at lower frequencies. In this collaborative paper, the main results of four long-term Ka-band propagation campaigns are presented. The experiments are carried out in Ottawa, Canada (satellite Anik F2); Aveiro, Portugal; Madrid, Spain; and Toulouse, France (satellite HotBird 6 in the last three cases) and have been running since 2004 in Aveiro, 2006 in Ottawa and Madrid, and 2008 in Toulouse. After a brief introduction of the experiments, rain rate and excess attenuation results are discussed, first for a common two-year measurement period and later for the whole database available. Seasonal attenuation statistics for Madrid, Ottawa and Aveiro are compared. Finally, fade duration and fade slope statistics derived at three locations are presented and discussed.

The Argasidae of North America, Central America and Cuba,

no.1

Manual of the mosses of North America. By Léo Lesquereux and Thomas P. James. With six plates illustrating the genera.

copy 1

Fresh-water rhizopods of North America.

Text

American fishes; a popular treatise upon the game and food fishes of North America, with especial reference to habits and methods of capture, by G. Brown Goode...with numerous illustrations.

1st ed.

Late Quaternary extinction of a tree species in eastern North America

Widespread species- and genus-level extinctions of mammals in North America and Europe occurred during the last deglaciation [16,000–9,000 yr B.P. (by 14C)], a period of rapid and often abrupt climatic and vegetational change. These extinctions are variously ascribed to environmental change and overkill by human hunters. By contrast, plant extinctions since the Middle Pleistocene are undocumented, suggesting that plant species have been able to respond to environmental changes of the past several glacial/interglacial cycles by migration. We provide evidence from morphological studies of fossil cones and anatomical studies of fossil needles that a now-extinct species of spruce (Picea critchfieldii sp. nov.) was widespread in eastern North America during the Last Glacial Maximum. P. critchfieldii was dominant in vegetation of the Lower Mississippi Valley, and extended at least as far east as western Georgia. P. critchfieldii disappeared during the last deglaciation, and its extinction is not directly attributable to human activities. Similarly widespread plant species may be at risk of extinction in the face of future climate change.

Paleoindian large mammal hunters on the plains of North America

From ≈11,200 to 8,000 years ago, the Great Plains of North America were populated by small Paleoindian hunting groups with well developed weaponry and the expertise to successfully hunt large mammals, especially mammoths and bison. Mammoths became extinct on the Plains by 11,000 years ago, and, although paleoecological conditions were worsening, their demise may have been hastened by human predation. After this, the main target of the Plains Paleoindian hunters consisted of subspecies of bison, Bison antiquus and Bison occidentalis. As bison populations gradually diminished, apparently because of worsening ecological conditions, by ≈8,000 years ago, human subsistence was forced into a greater dependence on small animal and plant foods. Human paleoecology studies of the Paleoindian time period rely heavily on multidisciplinary efforts. Geomorphologists, botanists, soil scientists, palynologists, biologists, and other specialists aid archaeologists in data recovery and analysis, although, with few exceptions, their contributions are derived from the fringes rather than the mainstream of their disciplines.

Characterization of a unique variant of bat rabies virus responsible for newly emerging human cases in North America.

The silver-haired bat variant of rabies virus (SHBRV) has been identified as the etiological agent of a number of recent human rabies cases in the United States that are unusual in not having been associated with any known history of conventional exposure. Comparison of the different biological and biochemical properties of isolates of this virus with those of a coyote street rabies virus (COSRV) revealed that there are unique features associated with SHBRV. In vitro studies showed that, while the susceptibility of neuroblastoma cells to infection by both viruses was similar, the infectivity of SHBRV was much higher than that of COSRV in fibroblasts (BHK-21) and epithelial cells (MA-104), particularly when these cells were kept at 34 degrees C. At this temperature, low pH-dependent fusion and cell-to-cell spread of virus is seen in BHK-21 cells infected with SHBRV but not with COSRV. It appears that SHBRV may possess an unique cellular tropism and the ability to replicate at lower temperature, allowing a more effective local replication in the dermis. This hypothesis is supported by in vivo results which showed that while SHBRV is less neurovirulent than COSRV when administered via the intramuscular or intranasal routes, both viruses are equally neuroinvasive if injected intracranially or intradermally. Consistent with the above findings, the amino acid sequences of the glycoproteins of SHBRV and COSRV were found to have substantial differences, particularly in the region that contains the putative toxic loop, which are reflected in marked differences in their antigenic composition. Nevertheless, an experimental rabies vaccine based on the Pittman Moore vaccine strain protected mice equally well from lethal doses of SHBRV and COSRV, suggesting that currently used vaccines should be effective in the postexposure prophylaxis of rabies due to SHBRV.

Fate of biological control introductions: monitoring an Australian fungal pathogen of grasshoppers in North America.

In North America there are two generally recognized pathotypes (pathotypes 1 and 2) of the fungus Entomophaga grylli which show host-preferential infection of grasshopper subfamilies. Pathotype 3, discovered in Australia, has a broader grasshopper host range and was considered to be a good biocontrol agent. Between 1989 and 1991 pathotype 3 was introduced at two field sites in North Dakota. Since resting spores are morphologically indistinguishable among pathotypes, we used pathotype-specific DNA probes to confirm pathotype identification in E. grylli-infected grasshoppers collected at the release sites in 1992, 1993, and 1994. In 1992, up to 23% of E. grylli-infected grasshoppers of the subfamilies Melanoplinae, Oedipodinae, and Gomphocerinae were infected by pathotype 3, with no infections > 1 km from the release sites. In 1993, pathotype 3 infections declined to 1.7%. In 1994 grasshopper populations were low and no pathotype 3 infections were found. The frequency of pathotype 3 infection has declined to levels where its long-term survival in North America is questionable. Analyses of biocontrol releases are critical to evaluating the environmental risks associated with these ecological manipulations, and molecular probes are powerful tools for monitoring biocontrol releases.

Forest losses predict bird extinctions in eastern North America.

Claims that there will be a massive loss of species as tropical forests are cleared are based on the relationship between habitat area and the number of species. Few studies calibrate extinction with habitat reduction. Critics raise doubts about this calibration, noting that there has been extensive clearing of the eastern North American forest, yet only 4 of its approximately 200 bird species have gone extinct. We analyze the distribution of bird species and the timing and extent of forest loss. The forest losses were not concurrent across the region. Based on the maximum extent of forest losses, our calculations predict fewer extinctions than the number observed. At most, there are 28 species of birds restricted to the region. Only these species would be at risk even if all the forests were cleared. Far from providing comfort to those who argue that the current rapid rate of tropical deforestation might cause fewer extinctions than often claimed, our results suggest that the losses may be worse. In contrast to eastern North America, small regions of tropical forest often hold hundreds of endemic bird species.