bluuebunny/crossref_metadata_2025_split huggingface dataset:
Crystal structure of rhodocytin, a ligand for the platelet‐activating receptor CLEC‐2
Authors: Watson Aleksandra A. , Eble Johannes A. , O'Callaghan Chris A. 
Published: June 2008

AbstractBinding of the snake venom protein rhodocytin to CLEC‐2, a receptor on the surface of human platelets, initiates a signaling cascade leading to platelet activation and aggregation. We have previously solved the structure of CLEC‐2. The 2.4 Å resolution crystal structure of rhodocytin presented here demonstrates that it is the first snake venom or other C‐type lectin‐like protein to assemble as a non‐disulfide linked (αβ)2 tetramer. Rhodocytin is highly adapted for interaction with CLEC‐2 and displays a concave binding surface, which is highly complementary to the experimentally determined binding interface on CLEC‐2. Using computational dynamic methods, surface electrostatic charge and hydrophobicity analyses, and protein–protein docking predictions, we propose that the (αβ)2 rhodocytin tetramer induces clustering of CLEC‐2 receptors on the platelet surface, which will trigger major signaling events resulting in platelet activation and aggregation.
Epigenetic dysregulation of the DAP kinase/p14/HDM2/p53/Apaf-1 apoptosis pathway in acute leukaemias
Authors: Chim C S , Chan W W L , Kwong Y L 
Published: June 2008

Background:Dysregulation of apoptosis is important in carcinogenesis.Aim and Methods:To analyse the potential inactivation of the DAP kinase/p14/HDM2/p53/Apaf-1 pathway by aberrant promoter methylation in acute leukaemias.Results:Of five leukaemic lines examined,p14was unmethylated in Raji, HL60 and U937, but completely deleted in Jurkat and NB4.DAP kinasewas totally methylated in Raji and NB4, but unmethylated in HL60, Jurkat and U937.Apaf-1was unmethylated in all the lines. At diagnosis,DAP kinasemethylation occurred in eight (25%) APL patients and none of the other AML patients (8/32 vs 0/50, p = 0.001).DAP kinasemethylation was detected in four (16%) ALL patients.p14andApaf-1methylation was not detected in any of the 32 cases of acute promyelocytic leukaemia (APL), 50 cases of other subtypes of acute myeloid leukaemia (AML), and 25 cases of acute lymphoblastic leukaemia.Conclusion:Among AML subtypes,DAP kinaseis preferentially hypermethylated in APL.
Rb–Sr and U–Pb geochronology and setting of the Buffalo Head Hills kimberlite field, northern AlbertaThis article is one of a selection of papers published in this Special Issue on the themeGeology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.
Authors: Eccles D. Roy , Creaser Robert A. , Heaman Larry M. , Ward Jeff 
Published: June 2008

New Rb–Sr phlogopite and U–Pb perovskite age determinations for 12 of 38 known ultramafic bodies in the Buffalo Head Hills area of north-central Alberta show that kimberlitic magmatism occurred in at least two separate episodes during Late Cretaceous and Paleocene time. Nine kimberlites yield Coniacian to Campanian ages of between 88 ± 5 Ma (U–Pb perovskite, K5A) and 81.2 ± 2.3 Ma (Rb–Sr phlogopite, K252). A Danian U–Pb perovskite isochron age of 63.5 ± 0.7 Ma was obtained for the BM2 kimberlite, and Selandian Rb–Sr ages of 59.6 ± 2.8 and 60.3 ± 0.8 Ma were determined for the K1A and K19 bodies, respectively. These specific periods of magmatism correspond to characteristic intra-field features such as kimberlite spatial distribution, diamond content, rock classification, and mechanisms of emplacement. The ∼88–81 Ma group generally occurs in the northwestern part of the field and defines the diamond window for the Buffalo Head Hills kimberlite field. This volcanism is contemporaneous with sedimentary host rock deposition, which has important implications for the size and morphological complexity of the kimberlite bodies. The ∼64 Ma BM2 body represents the only known occurrence of hypabyssal-facies kimberlite in this field and is similar in terms of source composition to the ∼88–81 Ma kimberlites, but is not diamond bearing. The ∼60 Ma group occurs in the southwestern part of the field, is derived from a weakly diamondiferous – barren hybrid ultramafic source and features bodies that are eroded to present-day stratigraphic levels.
Quaternary stratigraphy and glacial history of the Peace River valley, northeast British ColumbiaThis article is one of a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.
Authors: Hartman Gregory M.D. , Clague John J. 
Published: June 2008

Two Cordilleran and three Laurentide glacial advances are recorded in Quaternary sediments and landforms in the Peace River valley, northeast British Columbia. The advances are inferred from fluvial gravels, glaciolacustrine sediments, and tills within nested paleovalleys excavated during three interglaciations and from the distribution of granitoid clasts derived from the Canadian Shield. Till of the last (Late Wisconsinan) Laurentide glaciation occurs at the surface, except where it is overlain by postglacial sediments. The advance that deposited this till was the most extensive in the study area, and the only advance definitively recognized in western Alberta south of the study area. Late Wisconsinan Cordilleran till has not been found in the study area, but Cordilleran and Laurentide ice may have coalesced briefly during the last glaciation. Support for this supposition is provided by the inferred deflection of Laurentide flutings to the southeast by Cordilleran ice. The earliest Laurentide advance may have been the least extensive of the three Laurentide events recognized in the study area. Erratics attributed to this advance occur only east of the Halfway River – Beatton River drainage divide.
Quaternary stratigraphy of the Prophet River, northeastern British ColumbiaThis article is one of a selection of papers published in this Special Issue on the theme Geology of northeastern British Columbia and northwestern Alberta: diamonds, shallow gas, gravel, and glaciers.
Authors: Trommelen Michelle , Levson Vic 
Published: June 2008

Exposures in the Prophet River valley in northeast British Columbia provide a unique glimpse into the Quaternary history of the northwest Canadian Boreal Plains. The region shows evidence of Late Wisconsinan Laurentide glaciation in the form of widespread till, containing abundant erratic clasts derived from the Canadian Shield. Vertical sections along the Prophet River expose non-glacial and advance glacial sediments below this till. Pre-Late Wisconsinan non-glacial or interglacial floodplain sediments are interbedded with fluvial gravels at many sites. Macrofossils within horizontally laminated organic-rich black clay and silt indicate deposition on the floodplain of the paleo-Prophet River within an oxbow lake. The climate during deposition is interpreted to be similar to present, supporting a dominantly spruce forest. Wood obtained from eight sites provided non-finite radiocarbon ages, and one sample provided an age of 49 300 ± 2000 BP, which is also considered non-finite. Glaciolacustrine clays and silts, deposited during impoundment of eastward-flowing drainage by the advance of the Laurentide Ice Sheet (LIS) in the Late Wisconsinan, overlie the non-glacial sediments throughout the valley. A blanket of clast-poor, clay-rich till up to 20 m thick, and deposited by the LIS, drapes the glaciolacustrine sediments. Since deglaciation, the Prophet River has incised the valley and formed fluvial terraces at different levels above the modern river.
The crustal structure of the southern Nain and Makkovik provinces of Labrador derived from refraction seismic data
Authors: Funck Thomas , Hansen Annette K. , Reid Ian D. , Louden Keith E. 
Published: June 2008

Data from a refraction seismic profile parallel to the coast of Labrador (Canada) were used to determine the crustal structure across the boundary of the Nain and Makkovik provinces, and to look for evidence for an offshore continuation of the Mesoproterozoic Nain Plutonic Suite (NPS). Seven seismometers recorded airgun shots along the 283 km long line. P- and S-wave velocity models were developed from forward and inverse modeling of travel times. The velocity model distinguishes three distinct zones. In the Saglek block of the Nain Province, the crust is divided into three layers with P-wave velocities between 5.8 and 6.9 km/s. Farther to the south, upper crustal velocities increase to 6.3–6.5 km/s and the Poisson’s ratio increases from 0.24 to 0.27. This zone correlates with a gravity low that is interpreted to outline the offshore continuation of the NPS. The upper crustal velocities are intermediate between anorthositic and granitoid rock samples collected from the NPS. A lower crustal reflector is limited to the area underneath the NPS and may be related to dioritic magmas. Mid-crustal and lower crustal velocities do not vary along the line and no underplating was detected. Within the Makkovik Province, upper crustal velocities of 5.9–6.2 km/s may indicate a dioritic composition similar to the Island Harbour Bay plutonic suite. Moho depth varies between 28 and 36 km with the maximum beneath the NPS. The variations could not be linked to effects of the Makkovikian orogeny but are thought to relate to Mesozoic rifting in Labrador Sea.
High-resolution seismo-stratigraphy and sedimentological properties of late- and postglacial sediments in Lac Guillaume-Delisle Estuary and Nastapoka Sound, eastern Hudson Bay
Authors: Lavoie Caroline , Hill Philip R. , Allard Michel , St-Onge Guillaume , Lajeunesse Patrick 
Published: June 2008

Lac Guillaume-Delisle Estuary and Nastapoka Sound are two sedimentary basins that recorded the late Quaternary deglaciation on the eastern coast of Hudson Bay. Acoustic profiles reveal an average sediments thickness of 15 m in the estuary and 6 m in the sound. These sediments reach 70 m thick in deep glacial troughs. Within the studied basins, four seismo-stratigraphic units overlying the acoustic basement were recognized. Unit 1 (subaqueous ice-contact and draped glaciomarine deposits associated with the Quebec–Labrador Ice Sector (QLIS) of the Laurentide Ice Sheet (LIS) and the Tyrrell Sea) records the presence of a short ice-marginal stillstand during glacial retreat. Unit 2 (paraglacial and postglacial fluvial-deltaic deposits) and unit 3 (postglacial silty deposits) result from erosion of emerged sediments and redeposition in response to changes in relative sea level (RSL). Finally, unit 4 is composed of deformed deposits associated with a mass wasting event. The stratigraphic sequence and the spatial distribution patterns of deposits show that Lac Guillaume-Delisle is a good model to explain the dynamics of the QLIS margin during and after successive ice stillstands, continuous RSL fall, river discharge (ablation on land), and its final ablation inland. Additionally, seven cores were sampled in the southeast part of the estuary. Geochemical (organic carbon and total nitrogen) and carbon isotopic contents, used as alternative proxy, indicate that the sampled sediments correspond to the postglacial estuarine deposits of unit 3. Allochthonous sources of carbon dominate the supply to the sediments where the environment is regularly flushed by fresh and marine waters.
Paleomagnetism and counterclockwise tectonic rotation of the Upper Oligocene Sooke Formation, southern Vancouver Island, British Columbia
Authors: Prothero Donald R. , Draus Elizabeth , Cockburn Thomas C. , Nesbitt Elizabeth A. 
Published: June 2008

The age of the Sooke Formation on the southern coast of Vancouver Island, British Columbia, Canada, has long been controversial. Prior paleomagnetic studies have produced a puzzling counterclockwise tectonic rotation on the underlying Eocene volcanic basement rocks, and no conclusive results on the Sooke Formation itself. We took 21 samples in four sites in the fossiliferous portion of the Sooke Formation west of Sooke Bay from the mouth of Muir Creek to the mouth of Sandcut Creek. After both alternating field (AF) and thermal demagnetization, the Sooke Formation produces a single-component remanence, held largely in magnetite, which is entirely reversed and rotated counterclockwise by 35° ± 12°. This is consistent with earlier results and shows that the rotation is real and not due to tectonic tilting, since the Sooke Formation in this region has almost no dip. This rotational signature is also consistent with counterclockwise rotations obtained from the northeast tip of the Olympic Peninsula in the Port Townsend volcanics and the Eocene–Oligocene sediments of the Quimper Peninsula. The reversed magnetozone of the Sooke sections sampled is best correlated with Chron C6Cr (24.1–24.8 Ma) or latest Oligocene in age, based on the most recent work on the Liracassis apta Zone molluscan fauna, and also a number of unique marine mammals found in the same reversed magnetozone in Washington and Oregon.
Root dynamics in sprouting tanoak forests of southwestern Oregon
Authors: Ahrens Glenn R. , Newton Michael 
Published: June 2008

Root and shoot biomass were measured across an 8 year chronosequence in mature and regenerating stands of tanoak ( Lithocarpus densiflorus (Hook. & Arn.) Rehd.), following cutting and burning in mature tanoak forests. Tanoak stump sprouts rapidly replaced leaf biomass but did not maintain preexisting root systems. Rather, root biomass declined for several years, with the largest proportional decline in extra-fine roots. Four years after harvest, live root biomasses in diameter classes 0.25–2.00 and 0.25–5.00 mm were 25% and 30% of values in mature tanoak forests, respectively. The proportion of dead roots was strongly correlated with maximum summer soil temperature. Root/shoot ratios recovered to preharvest values by age 3–4 years, at which time the live biomass of fine roots and leaf biomass was approximately 30%–40% of values in mature forest. From age 4 to 8 years, stable root/shoot ratios were associated with a three- to four-fold reduction in growth rate of leaf biomass and a proportional increase in growth of fine roots. These findings support the general theory of a functional root–shoot balance in tanoak and suggest a possible role for soil temperature in postharvest root dynamics. Improved understanding of postdisturbance root and shoot dynamics in tanoak will help identify competitive interactions and priorities for vegetation management decisions in establishment of conifers following harvest of mixed conifer–hardwood forests of southwestern Oregon and northern California.
A biophysical process model of tree mortality in surface fires
Authors: Michaletz S. T. , Johnson E. A. 
Published: June 2008

The mechanisms governing tree mortality in surface fires are poorly understood, owing in large part to the absence of a process-based framework for defining and evaluating these mechanisms. This paper begins the development of such a framework by deriving a first-order process model of tree mortality in surface fires (intensities less than approximately 2500 kW·m–1). A buoyant line-source plume model is used to drive heat transfer models of vascular cambium and vegetative bud necroses, which are linked to tree mortality using an allometrically-based sapwood area budget. Model predictions are illustrated for white spruce ( Picea glauca ), lodgepole pine ( Pinus contorta ), and trembling aspen ( Populus tremuloides ) and are compared with independent mortality data for Engelmann spruce ( Picea engelmannii Parry ex Engelm.) and Pinus contorta Dougl. Results help define first-order mortality mechanisms and suggest second-order mortality mechanisms that should be incorporated into future modeling efforts.
Fine root growth and mortality in different-aged ponderosa pine stands
Authors: Andersen Chris P. , Phillips Donald L. , Rygiewicz Paul T. , Storm Marjorie J. 
Published: June 2008

Root minirhizotron tubes were installed at two sites around three different age classes of ponderosa pine ( Pinus ponderosa Dougl. ex Laws.) to follow patterns of fine root (≤2 mm diameter) dynamics during a 4 year study. Both sites were old-growth forests until 1978, when one site was clear-cut and allowed to regenerate naturally. The other site had both intermediate-aged trees (50–60 years) and old-growth trees (>250 years old). Estimates of fine root standing crop were greatest around young trees and least around intermediate-aged trees. Root production was highly synchronized in all age classes, showing a single peak in late May – early June each year. Root production and mortality were proportional to standing root crop (biomass), suggesting that allocation to new root growth was proportional to root density regardless of tree age. The turnover index (mortality/maximum standing crop) varied from 0.62 to 0.89·year–1, indicating root life spans in excess of 1 year. It appears that young ponderosa pine stands have greater rates of fine root production than older stands but lose more fine roots each year through mortality. The results indicate that soil carbon may accumulate faster in younger than in older stands.
Partial cutting reduces species richness of fungi on woody debris in oak-rich forests
Authors: Nordén Björn , Götmark Frank , Ryberg Martin , Paltto Heidi , Allmér Johan 
Published: June 2008

Partial cutting is increasingly applied in European temperate oak-dominated forests for biofuel harvesting, and to counteract succession in protected stands. Effects on biodiversity of these measures need to be carefully evaluated, and species-rich but neglected taxa such as fungi should be considered. We studied the effects of partial cutting on fungal fruiting bodies on woody debris. In 21 closed canopy forests rich in large oaks in Sweden, on average 25%–30% of the basal area was cut. Fruiting bodies were counted and some were collected in treated and control plots before and after treatment. We found 334 basidiomycete and 47 ascomycete species. Species richness of basidiomycetes declined significantly more in treated plots (on average 26%) than in control plots (on average 13%) between seasons. Species richness of ascomycetes increased by 17% in control plots and decreased by 2% in treated plots. Total species richness was significantly reduced on fine woody debris (1–10 cm in diameter), but not on coarse woody debris (>10 cm). Overall species composition did not change significantly as a result of partial cutting, but red-listed species tended to decrease more in treated plots. We suggest that approximately 30% of the stands should not be thinned, and dead stems and fallen branches should not be removed, to favor saproxylic fungi and their associated fauna.
Competitive effects of woody and herbaceous vegetation in a young boreal mixedwood stand
Authors: Man Cosmin D. , Comeau Philip G. , Pitt Douglas G. 
Published: June 2008

The influence of aspen ( Populus tremuloides Michx.) and herbaceous (forb and grass) vegetation on resource availability and white spruce ( Picea glauca (Moench) Voss) growth were examined as part of a long-term experiment established in 2002 near Whitecourt, Alberta, Canada. During the 2005 growing season, we examined the effects of herbicide treatments designed to control only woody (triclopyr ester) or both woody and herbaceous (glyphosate) vegetation on leaf area index (LAI) of both the woody and herbaceous components and relationships among LAI and light, soil moisture, air temperature, soil temperature, nitrogen availability, and spruce growth. Treatments reduced LAI and increased light, soil nitrogen availability, and white spruce growth. There were no apparent effects of the treatments on soil moisture in 2005. Both the woody and herb–grass layers appear to be competing for light and soil nitrogen in this young plantation. Controlling only woody vegetation resulted in an increase in herbaceous and total LAI (dominated by the grass Calamagrostis canadensis (Michx.) Beauv.). Spot treatment, involving control of vegetation within a 2 m radius of spruce seedlings while leaving 1 m of untreated ground between treated spots, may be a promising alternative to classical broadcast treatments for establishing spruce in a mixedwood stand. Spot treatments provided good growing conditions and reduced exposure of spruce seedlings to summer and winter frost injury during the first 3 years after planting.
Relative importance of different secondary successional pathways in an Alaskan boreal forest
Authors: Kurkowski Thomas A. , Mann Daniel H. , Rupp T. Scott , Verbyla David L. 
Published: June 2008

Postfire succession in the Alaskan boreal forest follows several different pathways, the most common being self-replacement and species-dominance relay. In self-replacement, canopy-dominant tree species replace themselves as the postfire dominants. It implies a relatively unchanging forest composition through time maintained by trees segregated within their respective, ecophysiological niches on an environmentally complex landscape. In contrast, species-dominance relay involves the simultaneous, postfire establishment of multiple tree species, followed by later shifts in canopy dominance. It implies that stand compositions vary with time since last fire. The relative frequencies of these and other successional pathways are poorly understood, despite their importance in determining the species mosaic of the present forest and their varying, potential responses to climate changes. Here we assess the relative frequencies of different successional pathways by modeling the relationship between stand type, solar insolation, and altitude; by describing how stand age relates to species composition; and by inferring successional trajectories from stand understories. Results suggest that >70% of the study forest is the product of self-replacement, and tree distributions are controlled mainly by the spatial distribution of solar insolation and altitude, not by time since last fire. As climate warms over the coming decades, deciduous trees will invade cold sites formerly dominated by black spruce, and increased fire frequency will make species-dominance relay even rarer.
Basidiomycete decay fungi within stems of Nothofagus windfalls in a Southern Hemisphere beech forest
Authors: Hood I. A. , Beets P. N. , Gardner J. F. , Kimberley M. O. , Power M. W.P. , Ramsfield T. D. 
Published: June 2008

Fungi were isolated to determine the predominant decomposer species active in the coarse woody debris in a beech forest in the central North Island of New Zealand. Basidiomycetes were obtained in 55% of 4569 isolation attempts from discs cut from six trees each of Nothofagus fusca (Hook. F.) Oerst. and Nothofagus menziesii (Hook. F.) Oerst. uprooted during a storm 24 years earlier. Percentage yields varied significantly among trees but not between tree species. However, for N. fusca, basidiomycetes were obtained less frequently from stems of greater mean diameter. In total, 96% of basidiomycete isolates were composed of 18 species, the most abundant being Armillaria novae-zelandiae (G. Stev.) Herink, mainly present in the outer 12 cm, and Ganoderma cf. applanatum sensu Wakef. and Cyclomyces tabacinus (Mont.) Pat., which penetrated more deeply. These fungi were distributed along the stems as somatically incompatible colonies reaching lengths of 11, 2, and 3 m for each species, respectively; those of G. cf. applanatum were separated by brown pseudosclerotial plates. Fruiting of these species was significantly associated with isolation of cultures and, for G. cf. applanatum and C. tabacinus, provided a reliable guide to stem colonization. Basidiomycete diversity in the Nothofagus stems was greater than in two podocarp species in an earlier study. Data from this investigation are being used to assess how decay fungi, together with other factors, influence rates of decomposition of indigenous coarse woody debris.