bluuebunny/crossref_metadata_2025 huggingface dataset:
Holocene sedimentation in glacial Tasikutaaq Lake, Baffin Island
Authors: Lemmen Donald S. , Gilbert Robert , Smol John P. , Hall Roland I.
Published: October 2008

Tasikutaaq Lake, on Cumberland Peninsula, Baffin Island, receives inflow and fine sediment from a 448 km2 drainage basin, 21% of which is glacier covered. During the summer of 1983 the lake remained essentially isothermal between about 4 and 6 °C. The suspended sediment concentration of inflow never exceeded 100 mg L−1 with overflow and homopycnal flow dominant.Surface sediments are clearly laminated, although varves are not apparent. The sediments are very fine, with less than 3% sand in all but the most proximal sites. Average sedimentation rates between 1976 and 1983 ranged from about 4 mm a−1 to 0.25 mm a−1 down lake from the point of inflow. The absence of varves is a function of the low rates of sediment accumulation and the long residence time of the fine sediments in the water column.Three sediment cores up to 135 cm in length reveal marked changes in sediment characteristics and diatom assemblages through the Holocene. During the late Foxe Glaciation it is likely that glacier ice contacted the lake, with retreat upvalley recorded by thinly varved (?) silts. By 7580 ± 140 BP ice had retreated to near its present margins. The earliest diatom assemblage in the cores is dominated by small Fragilaria spp., typical of late glacial, pioneering environments. Sedimentation rates during much of the Hypsithermal were about five times less than at present, with the resulting massive sediments having "nonglacial" characteristics despite the presence of glacial ice in the drainage basin. A planktonic diatom flora suggests that summer lake ice cover was minimal at this time. A climatic deterioration at about 4500 BP marks the onset of the Neoglacial, recorded by a shift in the diatom assemblage to species characteristic of more shallow water environments. Retreat from Neoglacial moraines is recorded by clearly laminated sediments and increasing accumulation rates. In general, laminated sediments relate to periods of high sediment input associated with glacial retreat, whereas massive sediments relate to low sediment input in association with glacial stabilization or advance.
Source terranes for Proterozoic sedimentary rocks in southern British Columbia: Nd isotopic and petrographic evidence
Authors: Burwash R. A. , Cavell P. A. , Burwash E. J.
Published: October 2008

Quartz arenites of the Fort Steele Formation, the lowest exposed stratigraphic unit of the Purcell Supergroup, have Nd crustal residence times (Tcr) of 2.61–2.63 Ga. These overlap the low end of the Tcr range of the polymetamorphic Kenoran–Hudsonian basement of southern Alberta and southwestern Saskatchewan. The Tcr values of overlying fine-grained Purcell rocks average 2.0 Ga.Near Lake Windermere, the basal Toby conglomerates of the Windermere Supergroup, apparently derived from underlying Purcell strata, have Tcr values of 1.98 and 2.03 Ga. Stratigraphically higher argillite and arkoses range from 2.35 to 2.54 Ga. This higher range indicates contributions from a source terrane different from the main body of the Purcell Supergroup.Our interpretation of events in the East Kootenay area is that early Purcell sedimentation (Fort Steele Formation) was derived from reworking of the crystalline basement of the Alberta shelf as the Beltian Sea transgressed. As the basin deepened, it was filled by fine-grained turbidites from a distal southern or southeastern source. Later Purcell strata have more complex paleocurrent direction patterns but relatively uniform Tcr values similar to those of the earlier turbidites. Following the East Kootenay orogeny, the basal conglomerate of the Windermere Supergroup (Toby Formation) consisted dominantly of locally derived clasts. These Purcell-derived strata grade upward into arkosic rocks with an admixture of Archean detrital material, probably from a proximal eastern source.
The ichnotaxonomy of Conostichus and other plug-shaped ichnofossils
Authors: Pemberton S. George , Frey Robert W. , Bromley Richard G.
Published: October 2008

The systematics of the single-entrance, plug-shaped, soft-substrate trace fossils have long been in need of revision. At least 15 ichnogenera, comprising 32 ichnospecies, have been used, but an examination of the type material that is available suggests that this is excessive. A review of ichnotaxa indicates that the valid ichnospecies can be encompassed within five ichnogenera as follows: Conostichus (five ichnospecies), Bergaueria (including Kulindrichnus, three), Conichnus (including Amphorichnus, two), Dolopichnus (one), and Astropolichnus (one). In addition, several minor ichnogenera for related structures are considered. These are Calycraterion, Margaritichnus, and Mammillichnis.The majority of plug-shaped structures are interpreted as cubichnia or domichnia, dominantly of actinarian sea anemones. The occurrence of these trace fossils is predominantly in Paleozoic rocks.
Evidence for recent temperature-induced water migration into permafrost from the tritium content of ground ice near Mayo, Yukon Territory, Canada
Authors: Burn C. R. , Michel F. A.
Published: October 2008

Determinations of the tritium (3H) content of ground ice collected near Mayo, Yukon Territory, indicate that since the mid-1950s atmospheric water has infiltrated permafrost to depths of up to 50 cm. The rate of tritium infiltration into permafrost at two plots irrigated with tritiated water in 1983 suggests that tritium movement is principally due to temperature-induced mass transport rather than molecular diffusion.
Climatic significance of Late Pleistocene insect fossils from Marias Pass, Montana
Authors: Elias Scott A.
Published: October 2008

A small insect fossil assemblage was recovered from Late Pleistocene lake sediment below the Mount St. Helens Jy ash near Marias Pass, Montana. The insect fauna contains several arctic, alpine, and open-ground beetles, including Bembidion sulcipenne hyperboroides and possibly Holoboreaphilus nordenskioeldi. This fauna, in conjunction with the plant macrofossil evidence, suggests that at about 11 400 BP tree line was at least 450 m lower than present.
Late winter – early spring sedimentation off the Great Whale River, southeastern Hudson Bay
Authors: d'Anglejan B. , Biksham G.
Published: October 2008

Sediment traps were used to measure particle-settling fluxes in serial moorings offshore of Great Whale River (Hudson Bay), both under the late winter sea-ice cover and during and after breakup. Before breakup, the settling fluxes ranged between 0.25 and 2 g cm−2 100 a−1, increasing from April to May in response to the progressively larger under-ice algal biomass. Fluxes also increased with depth. During and after breakup, including the early summer period of peak runoff, sedimentation rates increased to values of up to 33 g cm−2100 a−1. These fluxes agree with the mean sedimentation rate determined from 210Pb activities in the underlying sediments.
Geological environment of the Cigar Lake uranium deposit
Authors: Bruneton P.
Published: October 2008

The Cigar Lake uranium deposit occurs within the Athabasca Basin of northern Saskatchewan, Canada. Like other major uranium deposits of the basin, it is located at the unconformity separating Helikian sandstones of the Athabasca Group from Aphebian metasediments and plutonic rocks of the Wollaston Group. The Athabasca Group was deposited in an intra-continental sedimentary basin that was filled by fluviatile terrestrial quartz sandstones and conglomerates. The group appears undeformed and its actual maximum thickness is about 1500 m. On the eastern side of the basin, the detrital units correspond to the Manitou Falls Formations where most of the uranium deposits are located. The Lower Pelitic unit of the Wollaston Group, which lies directly on the Archean basement, is considered to be the most favourable horizon for uranium mineralization. During the Hudsonian orogeny (1800–1900 Ma), the group underwent polyphase deformation and upper amphibolite facies metamorphism. The Hudsonian orogeny was followed by a long period of erosion and weathering and the development of a paleoweathering profile.On the Waterbury Lake property, the Manitou Falls Formation is 250–500 m thick and corresponds to units MFd, MFc, and MFb. The conglomeratic MFb unit hosts the Cigar Lake deposit. However, the basal conglomerate is absent at the deposit, wedging out against an east–west, 20 m high, pre-Athabasca basement ridge, on top of which is located the orebody.Two major lithostructural domains are present in the metamorphic basement of the property: (1) a southern area composed mainly of pelitic metasediments (Wollaston Domain) and (2) a northern area with large lensoid granitic domes (Mudjatik Domain). The Cigar Lake east–west pelitic basin, which contains the deposit, is located in the transitional zone between the two domains. The metamorphic basement rocks in the basin consist mainly of graphitic metapelitic gneisses and calcsilicate gneisses, which are inferred to be part of the Lower Pelitic unit. Graphite- and pyrite-rich "augen gneisses," an unusual facies within the graphitic metapelitic gneisses, occur primarily below the Cigar Lake orebody.The mineralogy and geochemistry of the graphitic metapelitic gneisses suggest that they were originally shales. The abundance of magnesium in the intercalated carbonates layers indicates an evaporitic origin.The structural framework is dominated by large northeast–southwest lineaments and wide east–west mylonitic corridors. These mylonites, which contain the augen gneisses, are considered to be the most favourable features for the concentration of uranium mineralization.Despite the presence of the orebody, large areas of the Waterbury Lake property remain totally unexplored and open for new discoveries.
Clay mineralogy and isotope geochemistry of the alteration halo at the Cigar Lake uranium deposit
Authors: Percival J. B. , Bell K. , Torrance J. K.
Published: October 2008

The clay-size fraction of the alteration halo associated with the Cigar Lake uranium deposit consists of illite with subordinate kaolinite, sudoite (Al-chlorite), Fe-chlorite, hematite, and traces of an illite–chlorite mixed-layer mineral. The Kübler Index of illite crystallinity ranges from 2.0 to 6.7; the most-altered samples average 4.0. These data indicate that high-grade diagenetic to anchizonal conditions have been reached within the alteration halo. Intensity ratios of the 002 and 001 illite reflections (I(002)/I(001)) are generally greater than 0.4, the phengite–muscovite boundary, reflecting aluminum-rich illites; illite composition approaches hydromuscovite. Whereas 1M and 2M polytypes prevail regionally, the presence of 3T and 2M polytypes in the alteration halo suggests that, locally, higher temperatures have been attained than the regional estimates of 180–220 °C.K–Ar dates for illite-rich samples, from 1255 to 1148 Ma, could reflect variable resetting of the K–Ar system during hydrothermal fluid circulation subsequent to and (or) during main-stage uranium-ore formation. The sudoite–illite assemblage from an altered basement sample yields a date of 815 Ma, unlike the clay-rich ore sample that contains no radiogenic argon. The younger date of the basement sample and the lack of radiogenic 40Ar in the ore sample may result from alteration.Average δD and δ18O values for illite-rich samples are −82 and +10, respectively. Samples that contain sudoite are enriched in D, but the ore sample containing Fe-chlorite is depleted in D and 18O relative to the illite-rich samples. The variation observed in δD values may reflect the exchange behaviour of different clay minerals or low-temperature interaction with meteoric waters.
Géochimie des eaux liées au gisement d'uranium de Cigar Lake (Saskatchewan, Canada) et apport des isotopes de l'uranium et du plomb comme guides de prospection
Authors: Toulhoat Pierre , Beaucaire Catherine
Published: October 2008

The primary objective of this study is a better understanding of the chemical evolution of the waters crossing the Cigar Lake (Saskatchewan, Canada) uranium ore deposit and, once described, to investigate the behavior of the lead and uranium isotopes and to test their use as guidelines in exploration. The underground waters around the Cigar Lake ore deposit were sampled by pumping bore holes or by air lifting. Isotopic analyses of U and Pb and chemical analyses of the major elements and of some trace elements (Ba, Ra, U) were completed. Based on these results, a model is proposed to explain the genesis and evolution of the waters and also to account for the water–minerals equilibria. The saturation indices of uraninite and coffinite were determined by way of oxidation–reduction potentials calculated on the basis of measured Fe contents. The waters saturated with these minerals, which are also the most reduced, are systematically located directly above or across the ore deposit. These saturation indices, as well as the calculated oxidation–reduction potentials, are good guidelines for hydrogeochemical exploration in the Cigar Lake orebody setting; however, they must be used only in a relative fashion. Furthermore, the 234U/238U disequilibrium measurements and the U concentration in the waters permit the recognition of waters having percolated through the mineralized zones (higher U concentrations, lower disequilibria). The nature of the mineralization is probably responsible for the coexistence of the two evolutionary trends within the mineralized zones; in the high-grade zones, the disequilibria are low, whereas in the zones of disseminated mineralization or in halos surrounding the orebody, the disequilibria are greater, reflecting the prevailing influence of selective dissolution of 234U in the zones where exchange surfaces between the mineral carrying U and the solution are more important. The measurement of Pb isotopic ratios in the waters also permits of a clear characterization of waters that have percolated through the ore deposit: in this case, the Pb isotopic ratios are enriched in radiogenic Pb. [Journal Translation]
A new Ambystomatid salamander, Dicamptodon antiquus n.sp., from the Paleocene of Alberta, Canada
Authors: Naylor Bruce G. , Fox Richard C.
Published: October 2008

The discovery of a skull and partial postcranial skeleton of Dicamptodon from northern Alberta is the earliest certain record of the subfamily Dicamptodontinae. The specimen comes from Late Paleocene lake sediments, which also contain the remains of fish and plants. The close resemblance of the specimen to larvae or neotenes of extant Dicamptodon shows that this family exhibits the common trend of extreme conservatism known from other salamanders. The specimen is found in association with floral assemblages, confirming Nussbaum's hypothesis of the origin of the genus in northwestern North America.
A coral reef in the Telkwa Range, British Columbia: the earliest Jurassic example
Authors: Stanley Jr George D. , McRoberts Christopher A.
Published: October 2008

An end-Triassic mass extinction profoundly affected reef ecosystems that flourished in the Late Triassic Tethys seaway. The collapse of Late Triassic coral–sponge reefs was followed by an Early Jurassic (Hettangian–Sinemurian) perturbation interval with a near-global absence of reefs and sharp reductions in diversity. A Jurassic (Sinemurian) reef in the Hazelton Group of central British Columbia appears to fill the gap. Its paleoecology and composition show it to be the first large-framework example in North America and perhaps the world. It demonstrates that the reef-building Triassic coral, Phacelostylophyllum, survived the extinction event and was constructing reefs in Early Jurassic time during a global reef eclipse. The reef is a 48 m thick bioherm that grew within the island-arc complex of Stikinia. Following a decrease in volcanism, reef building began with bivalves growing upon water-lain tuffs. The reef was dominated by large dendroid–phaceloid corals, primarily Phacelostylophyllum rugosum, a species known from the Upper Triassic of Italy, which produced extensive constructional framework. Other fossils include bivalves, solitary and colonial corals, and a variety of dwellers and reef destroyers. Three stages of growth are present. During siliciclastic deposition, the reef mound grew into a bioherm with steep relief and flanking beds. Two intervals of arrested growth marked by pyroclastic lenses and hard grounds punctuated the reef's history. The reef was finally overwhelmed by volcaniclastic sediment, was uplifted, and developed paleokarst. The reef is unique in understanding the dynamics of recovery after the end-Triassic mass extinction.
A Frost Tube for the Determination of Freezing in the Active Layer above Permafrost
Authors: Mackay J. Ross
Published: October 2008

A frost tube which can be used in permafrost areas to determine both the downward and upward movements of the two freezing fronts in the active layer, during the fall freeze-back period, is described. The principle, which is based upon the differential vertical migration of fine and coarse particles resting upon an upward moving horizontal ice–water interface, is discussed. Attention is drawn to some of the ice characteristics of the active layer and top of the permafrost which result from upward freezing at the bottom of the active layer.
The Bearing Capacity of Rigid Piles Under Inclined Loads in Sand. III: Pile Groups
Authors: Meyerhof G. G. , Ranjan Gopal
Published: October 2008

Following Part I on vertical piles and Part II on inclined piles the present Part III deals with the general principles for estimating ultimate capacity of a pile bent under inclined load. The results of loading tests on two model pile bents with depth/diameter ratios of 13 and 23 for free standing bents and 15 and 25 for piled bents are presented. Test results on free standing and piled bents are reported in compact and dense states of packing of sand. Bents with vertical and batter piles have been tested under inclinations of load varying from vertical to horizontal.The experimental results are discussed and conclusions regarding the behavior of free standing and piled bents under inclination of load, type of bent, and pile cap are drawn.
An Artificial Material for Simulating Champlain Clays
Authors: Tavenas F. A. , Roy M. , Rochelle P. La
Published: October 2008

As part of an investigation on the behavior of Champlain clays, full scale penetrometer and vane tests had to be performed in the laboratory to observe the behavior of the soil during such tests. Since it was impossible to obtain samples of the necessary size, it was decided to develop a synthetic material which would model the mechanical properties of the Champlain clays.Such a model material has been defined. It consists of a mixture of kaolinite, bentonite, cement, and water. It is first shown to have a stress–strain behavior identical to that of the clay in unconfined compression tests, provided it is aged for 16 days. It is also shown to simulate very well all other mechanical properties of the Champlain clays, and more particularly the peculiar shape of the failure envelope in effective stress as well as the preconsolidation pressure.This material has been used successfully for laboratory penetrometer tests. It can also be used for the installation of instruments in situ or for the analysis of any testing or sampling technique.
Manicouagan-3: Auscultation du barrage principal
Authors: Dascal O.
Published: October 2008

The Manicouagan-3 hydro-electric development, presently under construction by Hydro-Quebec, required the erection of a 350 ft (107 m) high earth dam, founded on a 420 ft (126 m) deep gorge filled with alluvions.The presence of a pervious and highly compressible foundation (the alluvial material is composed mainly of a loose fine sand) of great depth combined with very steep slopes of the rock abutments, has imposed the adoption of a special solution to avoid seepage under the dam due to the high permeability and to minimize the formation of cracks in the core due to large differential settlements.The behavior of the dam during and after construction will be monitored by a complex instrumentation system, which includes a large number of instruments, bench marks, and reference points, implemented in the foundation, cut-off walls, and the embankment of the dam.Thus, 113 piezometers, 48 extensometers, 30 total pressure cells, 6100 ft (1830 m) of inclinometers, 465 ft (155 m) shear strips, and 137 survey points are incorporated in the instrumentation system.The number of readings to be recorded and the necessity to get the results in the shortest time possible have required the automation of the survey and a computer treatment of the results.The readings are surveyed by computerized equipment and the results recorded on punch tapes. An IBM tape-to-card puncher is used to transfer the readings recorded on the tape to a punch card, which can then be transmitted by the IBM-2780 terminal installed at Manic-3 to the Hydro-Quebec's computer (IBM-370-155) at Montreal.A special computer program was established by Hydro-Quebec for the storage and the treatment of the raw data furnished by the instrumentation system.The program is intended to allow a speedy presentation of the results in tabular or graphic (diagram) form for each instrument, or group of instruments.The results in tabular forms are retransmitted immediately by the terminal, and only the graphs, drawn in Montreal are transmitted periodically by the post.
Microstructure of Billings Shale and Biochemical Alteration Products, Ottawa, Canada
Authors: Gillott J. E. , Penner E. , Eden W. J.
Published: October 2008

A microstructural analysis has been made of altered and unaltered black shale from a site where foundation heave has occurred. Jarosite framboids composed of very small interlocking crystals, much larger crystals of gypsum and microorganisms are described in the altered shale. The relative roles of jarosite, gypsum, and other hydrated sulphates in the generation of heave forces is not fully understood. If jarosite is responsible, most black shales have a heave potential; if gypsum is responsible only black shales which contain carbonate need be of concern. Recognition of fungi and other microbes suggests a more complex biogeochemical cycle than previously supposed; the use of microorganisms as a method of controlling heave warrants more investigation.
Stability of Slopes in Frozen Soil, Mackenzie Valley, N.W.T.
Authors: McRoberts E. C. , Morgenstern N. R.
Published: October 2008

A field study of landslides has shown that certain types of mass movement in the Mackenzie Valley, N.W.T. are associated with shear failure in frozen soil. These land-slides have been classified on a descriptive basis as being block and multiple retrogressive slides. A detailed description of the characteristic morphology, and of the soil and permafrost conditions at these slides has been presented.Quantitative analysis of slides at a site on the Mountain River are consistent with the view that failure occurs through frozen soil with the base of the slide in unfrozen clay. It appears that high pore water pressures control the available shear strength in the unfrozen clay and that the long term strength of the permafrost soils is governed by a frictional resistance.
Compaction of Weathered Clays near Sarnia, Ontario
Authors: Ogunbadejo T. A. , Quigley R. M.
Published: October 2008

Oxidation weathering has produced up to 15% swelling clay from originally inactive soil chlorites in the upper 2 m of crustal soils at Sarnia, Ontario. Carbonates have been leached from the upper 1.5 m and deposited at depth.Surface soils containing the montmorillonite compact less efficiently than deeper soils, yielding modified A.A.S.H.O. densities up to 6 p.c.f. less than for deeper soils, provided the samples are not dried prior to compaction. Air drying produces clay mineral collapse and more efficient laboratory compaction, thus hiding the true compaction behavior of the surface soils.
Measurement of Hydraulic Conductivity of Frozen Soils
Authors: Williams P. J. , Burt T. P.
Published: October 2008

Frozen soils contain a significant amount of water which moves under appropriate gradients. An apparatus has been devised for measuring the hydraulic conductivity. It involves the use of reservoirs containing a weak solution of lactose such that the free energy is initially reduced to that of the water in the soil. The solution therefore remains unfrozen. A gradient is established by application of pressure, and pure water moves in the sample. The hydraulic conductivity is found to depend on soil type and temperature.
Dynamic experiments with small pile foundations
Authors: Novak Milos , F.Grigg Ronald
Published: October 2008

Dynamic experiments with small pile foundations were conducted in the field. Individual piles and a group of piles were tested. The experimental data were compared with theoretical predictions made on the basis of a theory described previously by Novak. It was found that the theory predicts the general characteristics of the response very well. Resonant amplitudes and natural frequencies can be predicted reasonably well when a shear modulus of the soil derived from a static test of a pile is used and when a correction for the effect of pile group (interaction) is made.
An approach to engineering geological investigations on the Island of Montreal
Authors: Grice R. H.
Published: October 2008

In Montreal, knowledge of extent of saturated sands and marine clays is essential before the construction period begins as many foundations require the excavation of these materials. Details of clay seams in limestones and decomposed igneous sills and dykes are needed, but the discovery of areas where there is an upper zone of 10 to 20 ft (3 to 6 m) of disturbed bedrock is of greater importance. Thus investigations should be concentrated in local problems.The maintenance of an up-to-date central inventory of all geological and geotechnical data together with information on the constructional difficulties and costs involved is desirable, but it appears only practicable to index work as a general rule.The review of a past investigation showed that in an area of simple geology the standard spacing of drillholes was appropriate and successfully defined bedrock morphology and elevations; however, elsewhere on the Island only chance or a greater density of investigation may reveal bad conditions.Investigations can only be optimum if the ‘users’, the structural designers, quantity estimators, construction supervisors as well as contractors are required to acknowledge formally the impact of the geological and geotechnical appraisals upon their planning and operations including the effects of conditions suspected to be present but not actually confirmed.
The effect of horizontal consolidation on differential settlements of footings on clay
Authors: Baker R.
Published: October 2008

This paper presents a discussion of the effect of horizontal consolidation on the differential settlements of footings on clay. Plane symmetry is considered. The solution of the two-dimensional consolidation equation is expressed in integral form, and evaluated numerically for different initial stress distributions.It was found that under certain conditions, horizontal consolidation can cause temporary differential settlements that are up to 50% larger than those expected on the basis of vertical consolidation only. The conditions favourable to such a phenomenon are: high stress concentration in the periphery of a structure, high anisotropy of the clay, thick clay layer, and small separation between the footings.
UNDERSTANDING THE STANDARD MODEL, AS A BRIDGE TO THE DISCOVERY OF NEW PHENOMENA AT THE LHC
Authors: MANGANO MICHELANGELO L.
Published: October 2008

I discuss the basic elements of the process that will lead to the discovery of possible new phenomena at the LHC (Large Hadron Collider). We review the status of the tools available to model the Standard Model backgrounds, and the role that such tools can play in the discovery phase, and in the exploration of the features and parameters of such new phenomena.
The Treatment of Borderline Personality Disorder: Implications of Research on Diagnosis, Etiology, and Outcome
Authors: Paris Joel
Published: October 2008

The treatment of patients with borderline personality disorder (BPD) is challenging. Making a diagnosis is necessary to plan therapy. But since we do not know the etiology of BPD, treatment cannot be based on a well-established theory. Outcome research shows that most patients recover with time. A series of clinical trials show that a variety of psychotherapies are effective in BPD and that the effects of medication are unimpressive.
Unpackingβ: Within-Host Dynamics and the Evolutionary Ecology of Pathogen Transmission
Authors: Antolin Michael F.
Published: October 2008

Rather than being fixed, pathogen transmission varies and is thus an object of natural selection. I examine how opportunities for selection on pathogen transmission depend on (a) pathogen fitness, (b) genetic variability, and (c) forces acting at within- and between-host levels. The transmission rate, β, influences processes such as epidemic spread, postepidemic fade-outs, and low-level persistence. Complexity of infection processes within hosts leads to different transmission rates among hosts and between types of pathogens (viruses, bacteria, eukaryotic Protozoa). Generality emerges, however, by “unpacking” β into within- and between-host opportunities for selection. This is illustrated by evolutionary biology of the bacterium Yersinia pestis, which causes plague in mammals, remains highly virulent and is transmitted by multiple routes, including fleas and direct contacts with infected hosts. The strength of within-host selection is manifested through infectivity, replication, pathogenicity, and dissemination from hosts. At the between-host level, responses to selection are less predictable because of environmental variation, whereas vector-borne transmission (usually by arthropods) provides additional opportunities for selection and trade-offs between vectors and hosts. In subdivided host populations, selection favors transmission before local pathogen extinction occurs, but key components (e.g. infectious periods of hosts) are determined by within-host dynamics. Pathogen transmission is often viewed in the context of transmission-virulence trade-offs, but within-host dynamics may cause host damage unrelated to transmission, and thus transmission-virulence trade-offs are not universal.
The Great American Schism: Divergence of Marine Organisms After the Rise of the Central American Isthmus
Authors: Lessios H.A.
Published: October 2008

After a 12-million-year (My) process, the Central American Isthmus was completed 2.8 My ago. Its emergence affected current flow, salinity, temperature, and primary productivity of the Pacific and the Atlantic and launched marine organisms of the two oceans into independent evolutionary trajectories. Those that did not go extinct have diverged. As no vicariant event is better dated than the isthmus, molecular divergence between species pairs on its two coasts is of interest. A total of 38 regions of DNA have been sequenced in 9 clades of echinoids, 38 of crustaceans, 42 of fishes, and 26 of molluscs with amphi-isthmian subclades. Of these, 34 are likely to have been separated at the final stages of Isthmus completion, 73 split earlier and 8 maintained post-closure genetic contact. Reproductive isolation has developed between several isolates, but is complete in only the sea urchin Diadema. Adaptive divergence can be seen in life history parameters. Lower primary productivity in the Caribbean has led to the evolution of higher levels of maternal provisioning in marine invertebrates.
Conspecific Brood Parasitism in Birds: A Life-History Perspective
Authors: Lyon Bruce E. , Eadie John McA.
Published: October 2008

Conspecific brood parasitism (CBP), whereby females lay eggs in the nests of other conspecifics, occurs in over 200 species of birds. As an alternative tactic to typical nesting, CBP expands and enriches the classic avian clutch size problem. It is an integral component of a flexible life-history strategy and, consequently, many intriguing aspects of this behavior—adaptive benefits to parasites, host-parasite interactions, population and evolutionary dynamics—can be understood best from a life-history perspective. Because parasite fitness depends on hosts, yet parasitism potentially reduces host fitness, CBP offers a novel opportunity to explore conflicts of interest within species. The intersection of life-history evolution, conflicts of interest, and frequency-dependent fitness provides much scope for theoretical exploration, and recent models indicate a complex range of evolutionary dynamics is possible, including consequences of CBP for population dynamics and conservation. CBP may also be a macroevolutionary stepping stone to diverse breeding systems.
Spatial Dynamics of Foodwebs
Authors: Amarasekare Priyanga
Published: October 2008

Foodwebs are important units of biodiversity, and yet, our knowledge of their spatial dynamics is sketchy at best. Here I attempt to synthesize existing knowledge into a framework that can both identify crucial gaps in the theory as well as facilitate empirical investigations. The synthesis is based on two major axes, foodweb complexity and type of movement, and considers two types of spatial effects, foodweb persistence via a reduction in local extinction and foodweb diversity via an increase in species coexistence. It highlights both invariant properties that are robust to increasing foodweb complexity and emergent properties that result from the interplay between foodweb dynamics and type of movement. It underscores the need for a comparative theoretical framework that can yield testable predictions.
The Earliest Land Plants
Authors: Gensel Patricia G.
Published: October 2008

Considerable progress has been made in documenting evidence of very early plants starting in the basal Ordovician employing dispersed spore, phytodebris, and mesofossil data. Macrofossil evidence is sparse until Late Silurian, but recent new data are improving our understanding of aspects of earliest plants. The considerable information about the possible source of cryptospores and trilete spores especially from the well-preserved mesofossils of the Late Silurian and Early Devonian is summarized. Promising avenues of research are the study of spore ultrastructure, and neo-paleo comparisons between newly discovered resistant components of extant bryophytes and fragmentary fossil remains. Recent macrofossil discoveries in the Late Silurian advance our understanding of early events in plant evolution and raise new questions about the timing of evolution or relationships among earliest (mostly vascular) plants.
The Kidney and Ear: Emerging Parallel Functions
Authors: Torban Elena , Goodyer Paul
Published: October 2008

The association between renal dysplasia and minor malformations of the external ear is weak. However, there is a remarkable list of syndromes that link the kidney to the inner ear. To organize these seemingly disparate syndromes, we cluster representative examples into three groups: (a) syndromes that share pathways regulating development; (b) syndromes involving dysfunction of the primary cilium, which normally provides critical information to epithelial cells about the fluid in which they are bathed; (c) syndromes arising from dysfunction of specialized proteins that transport ions and drugs in and out of the extracellular fluid or provide structural support.
Benefits of Training and Development for Individuals and Teams, Organizations, and Society
Authors: Aguinis Herman , Kraiger Kurt
Published: October 2008

This article provides a review of the training and development literature since the year 2000. We review the literature focusing on the benefits of training and development for individuals and teams, organizations, and society. We adopt a multidisciplinary, multilevel, and global perspective to demonstrate that training and development activities in work organizations can produce important benefits for each of these stakeholders. We also review the literature on needs assessment and pretraining states, training design and delivery, training evaluation, and transfer of training to identify the conditions under which the benefits of training and development are maximized. Finally, we identify research gaps and offer directions for future research.
Pendrin in the mouse kidney is primarily regulated by Cl− excretion but also by systemic metabolic acidosis
Authors: Hafner Patricia , Grimaldi Rosa , Capuano Paola , Capasso Giovambattista , Wagner Carsten A.
Published: October 2008

The Cl−/anion exchanger pendrin (SLC26A4) is expressed on the apical side of renal non-type A intercalated cells. The abundance of pendrin is reduced during metabolic acidosis induced by oral NH4Cl loading. More recently, it has been shown that pendrin expression is increased during conditions associated with decreased urinary Cl− excretion and decreased upon Cl− loading. Hence, it is unclear if pendrin regulation during NH4Cl-induced acidosis is primarily due the Cl− load or acidosis. Therefore, we treated mice to increase urinary acidification, induce metabolic acidosis, or provide an oral Cl− load and examined the systemic acid-base status, urinary acidification, urinary Cl− excretion, and pendrin abundance in the kidney. NaCl or NH4Cl increased urinary Cl− excretion, whereas (NH4)2SO4, Na2SO4, and acetazolamide treatments decreased urinary Cl− excretion. NH4Cl, (NH4)2SO4, and acetazolamide caused metabolic acidosis and stimulated urinary net acid excretion. Pendrin expression was reduced under NaCl, NH4Cl, and (NH4)2SO4 loading and increased with the other treatments. (NH4)2SO4 and acetazolamide treatments reduced the relative number of pendrin-expressing cells in the collecting duct. In a second series, animals were kept for 1 and 2 wk on a low-protein (20%) diet or a high-protein (50%) diet. The high-protein diet slightly increased urinary Cl− excretion and strongly stimulated net acid excretion but did not alter pendrin expression. Thus, pendrin expression is primarily correlated with urinary Cl− excretion but not blood Cl−. However, metabolic acidosis caused by acetazolamide or (NH4)2SO4 loading prevented the increase or even reduced pendrin expression despite low urinary Cl− excretion, suggesting an independent regulation by acid-base status.
Function and role of voltage-gated sodium channel NaV1.7 expressed in aortic smooth muscle cells
Authors: Meguro Kentaro , Iida Haruko , Takano Haruhito , Morita Toshihiro , Sata Masataka , Nagai Ryozo , Nakajima Toshiaki
Published: October 2008

Voltage-gated Na+ channel currents ( INa) are expressed in several types of smooth muscle cells. The purpose of this study was to evaluate the expression of INa, its functional role, pathophysiology in cultured human (hASMCs) and rabbit aortic smooth muscle cells (rASMCs), and its association with vascular intimal hyperplasia. In whole cell voltage clamp, INa was observed at potential positive to −40 mV, was blocked by tetrodotoxin (TTX), and replacing extracellular Na+ with N-methyl-d-glucamine in cultured hASMCs. In contrast to native aorta, cultured hASMCs strongly expressed SCN9A encoding NaV1.7, as determined by quantitative RT-PCR. INa was abolished by the treatment with SCN9A small-interfering (si)RNA ( P < 0.01). TTX and SCN9A siRNA significantly inhibited cell migration ( P < 0.01, respectively) and horseradish peroxidase uptake ( P < 0.01, respectively). TTX also significantly reduced the secretion of matrix metalloproteinase-2 6 and 12 h after the treatment ( P < 0.01 and P < 0.05, respectively). However, neither TTX nor siRNA had any effect on cell proliferation. L-type Ca2+ channel current was recorded, and INa was not observed in freshly isolated rASMCs, whereas TTX-sensitive INa was recorded in cultured rASMCs. Quantitative RT-PCR and immunostaining for NaV1.7 revealed the prominent expression of SCN9A in cultured rASMCs and aorta 48 h after balloon injury but not in native aorta. In conclusion, these studies show that INa is expressed in cultured and diseased conditions but not in normal aorta. The NaV1.7 plays an important role in cell migration, endocytosis, and secretion. NaV1.7 is also expressed in aorta after balloon injury, suggesting a potential role for NaV1.7 in the progression of intimal hyperplasia.
A therapeutic dose of doxorubicin activates ubiquitin-proteasome system-mediated proteolysis by acting on both the ubiquitination apparatus and proteasome
Authors: Liu Jinbao , Zheng Hanqiao , Tang Mingxin , Ryu Youn-Chul , Wang Xuejun
Published: October 2008

The ubiquitin proteasome system (UPS) degrades abnormal proteins and most unneeded normal proteins, thereby playing a critical role in protein homeostasis in the cell. Proteasome inhibition is effective in treating certain forms of cancer, while UPS dysfunction is increasingly implicated in the pathogenesis of many severe and yet common diseases. It has been previously shown that doxorubicin (Dox) enhances the degradation of a UPS surrogate substrate in mouse hearts. To address the underlying mechanism, in the present study, we report that 1) Dox not only enhances the degradation of an exogenous UPS reporter (GFPu) but also antagonizes the proteasome inhibitor-induced accumulation of endogenous substrates (e.g., β-catenin and c-Jun) of the UPS in cultured NIH 3T3 cells and cardiomyocytes; 2) Dox facilitates the in vitro degradation of GFPu and c-Jun by the reconstituted UPS via the enhancement of proteasomal function; 3) Dox at a therapeutically relevant dose directly stimulates the peptidase activities of purified 20S proteasomes; and 4) Dox increases, whereas proteasome inhibition decreases, E3 ligase COOH-terminus of heat shock protein cognate 70 in 3T3 cells via a posttranscriptional mechanism. These new findings suggest that Dox activates the UPS by acting directly on both the ubiquitination apparatus and proteasome.
Impairment of coronary flow reserve in aortic stenosis
Authors: Garcia Damien , Camici Paolo G. , Durand Louis-Gilles , Rajappan Kim , Gaillard Emmanuel , Rimoldi Ornella E. , Pibarot Philippe
Published: October 2008

Coronary flow reserve (CFR) is markedly reduced in patients with severe aortic valve stenosis (AS), but the exact mechanisms underlying this impairment of CFR in AS remain unclear. Reduced CFR is the key mechanism leading to myocardial ischemia symptoms and adverse outcomes in AS patients. The objective of this study was to develop an explicit mathematical model formulated with a limited number of parameters that describes the effect of AS on left coronary inflow patterns and CFR. We combined the mathematical V3 (ventricular-valvular-vascular) model with a new lumped-parameter model of coronary inflow. One thousand Monte-Carlo computational simulations with AS graded from mild up to very severe were performed within a wide range of physiological conditions. There was a good agreement between the CFR values computed with this new model and those measured in 24 patients with isolated AS ( r = 0.77, P < 10−4). A global sensitivity analysis showed that the valve effective orifice area (EOA) was the major physiological determinant of CFR (total sensitivity index = 0.87). CFR was markedly reduced when AS became severe, i.e., when EOA was <1.0 cm2, and was generally exhausted when the EOA was <0.5–0.6 cm2. The reduction of CFR that is associated with AS can be explained by the concomitance of 1) reduced myocardial supply as a result of decreased coronary perfusion pressure, and 2) increased myocardial metabolic demand as a result of increased left ventricular workload.
The physiology and pathophysiology of human breath-hold diving
Authors: Lindholm Peter , Lundgren Claes EG
Published: October 2008

This is a brief overview of physiological reactions, limitations, and pathophysiological mechanisms associated with human breath-hold diving. Breath-hold duration and ability to withstand compression at depth are the two main challenges that have been overcome to an amazing degree as evidenced by the current world records in breath-hold duration at 10:12 min and depth of 214 m. The quest for even further performance enhancements continues among competitive breath-hold divers, even if absolute physiological limits are being approached as indicated by findings of pulmonary edema and alveolar hemorrhage postdive. However, a remarkable, and so far poorly understood, variation in individual disposition for such problems exists. Mortality connected with breath-hold diving is primarily concentrated to less well-trained recreational divers and competitive spearfishermen who fall victim to hypoxia. Particularly vulnerable are probably also individuals with preexisting cardiac problems and possibly, essentially healthy divers who may have suffered severe alternobaric vertigo as a complication to inadequate pressure equilibration of the middle ears. The specific topics discussed include the diving response and its expression by the cardiovascular system, which exhibits hypertension, bradycardia, oxygen conservation, arrhythmias, and contraction of the spleen. The respiratory system is challenged by compression of the lungs with barotrauma of descent, intrapulmonary hemorrhage, edema, and the effects of glossopharyngeal insufflation and exsufflation. Various mechanisms associated with hypoxia and loss of consciousness are discussed, including hyperventilation, ascent blackout, fasting, and excessive postexercise O2consumption. The potential for high nitrogen pressure in the lungs to cause decompression sickness and N2narcosis is also illuminated.
Imatinib Mesylate Induces Quiescence in Gastrointestinal Stromal Tumor Cells through the CDH1-SKP2-p27Kip1 Signaling Axis
Authors: Liu Ying , Perdreau Sophie A. , Chatterjee Payel , Wang Linan , Kuan Shih-Fan , Duensing Anette
Published: October 2008

Gastrointestinal stromal tumors (GIST) are caused by activating mutations in the KIT or platelet-derived growth factor receptor α receptor tyrosine kinase genes. Approximately 85% of GIST patients treated with imatinib mesylate achieve disease stabilization, however, often in the presence of residual tumor masses. Complete remissions are rare and a substantial proportion of patients develop resistance to imatinib. Our study was designed to determine whether imatinib-associated responses may account for these clinical findings. We report here that imatinib stimulates cellular quiescence in a proportion of GIST cells as evidenced by up-regulation of the CDK inhibitor p27Kip1, loss of cyclin A, and reduced BrdUrd incorporation. Mechanistically, these events are associated with an imatinib-induced modulation of the APC/CDH1 signaling axis. Specifically, we provide evidence that imatinib down-regulates SKP2 and that this event is associated with increased nuclear CDH1, an activator of the APC that has been shown to regulate SKP2 stability. We also show that those GIST cells that do not undergo apoptosis in response to imatinib overexpress nuclear p27Kip1, indicating that they have withdrawn from the cell cycle and are quiescent. Lastly, we provide evidence that a fraction of primary GISTs with high SKP2 expression levels may have an increased risk of disease progression. Taken together, our results support a model in which GIST cells that do not respond to imatinib by apoptosis are removed from the proliferative pool by entering quiescence through modulation of the APC/CDH1-SKP2-p27Kip1 signaling axis. These results encourage further studies to explore compounds that modulate this pathway as antitumor agents in GISTs. [Cancer Res 2008;68(21):9015–23]