bluuebunny/crossref_metadata_2025 huggingface dataset:
Quantitative and qualitative effects of a severe ice storm on an old-growth beech–maple forest
Authors: Takahashi Koichi , Arii Ken , Lechowicz Martin J.
Published: July 2007

Comparing permanent plots censused in 1997 and again in 2005, we quantified the impact of a severe ice storm on forest composition and dynamics in an old-growth beech–maple forest in eastern Canada. Acer saccharum Marsh. and Fagus grandifolia Ehrh. accounted for 78% of stand basal area immediately before the January 1998 ice storm. By 2005, eight growing seasons after the ice storm, stand basal area had dropped from 49.1 m2/ha to 31.5 m2/ha, and total tree density (>1 cm diameter at breast height (DBH)) decreased from 6350 stems/ha to 3875 stems/ha. However, A. saccharum and F. grandifolia remained dominant, accounting for 74% of stand basal area. Detrended correspondence analysis of relative dominance ratios at each plot in 1997 and 2005 showed that community composition did not change much during this period for either understory (1 cm ≤ DBH < 10 cm) or canopy trees (DBH ≥ 10 cm). The ice storm did not lead to significant recruitment of saplings (DBH ≥ 1 cm), but appears to have only contributed more to the growth of already-established saplings. We conclude that the ice storm of 1998 substantially decreased stand basal area and stem density but did not act to change the overall species composition or tree diversity in this old-growth beech–maple forest.
Impact of simulated aspen shoot blight on trembling aspen
Authors: Blenis P.V.
Published: July 2007

Although aspen shoot blight (ASB), caused by Pollaccia americana Ondrej, is a common disease of trembling aspen ( Populus tremuloides Michx.), its impact is uncertain. Mechanical wounding, previously shown to be a reliable surrogate for ASB infection, was used to assess ASB impact in two experiments. In the first experiment, the effect of date of wounding on impact was studied by wounding 1-year-old aspen on four dates between 29 June and 10 August 2001. Tree form at the end of the 2001 growing season varied with wounding date, and for each of the wounding dates, tree height was reduced relative to that of unwounded, control trees. After the 2005 growing season, only trees wounded on 17 July were shorter than unwounded trees and the difference in heights was only 62 cm. In the second experiment, trees spaced at 2.0 or 0.67 m were wounded in four successive seasons to determine the effect of multiple years of infection on trees growing at different densities. Simulated ASB reduced tree height by an average of 16 cm, whereas branchiness was not increased by ASB, even at the lower density. Although ASB should not be ignored, these results suggest that it is unlikely to be amongst the most destructive pests of intensively managed aspen.
Patterns of leaf area and growing space efficiency in young even-aged and multiaged coast redwood stands
Authors: Berrill John-Pascal , O’Hara Kevin L.
Published: July 2007

Projected leaf area estimates were used to predict volume increment and basal area of second-growth coast redwood ( Sequoia sempervirens (D. Don) Endl.) trees on Jackson Demonstration State Forest, Mendocino County, California. Sample plots were established within even-aged and multiaged mixed-species stands. Redwood tree basal area growth was more strongly related to sapwood area than to tree size and differed significantly between canopy strata and overstory stratum crown classes. Projected leaf area was predicted from sapwood area for each tree, and summarized to the stand level, giving a maximum stand leaf area index (LAI) estimate of 14.9 m2/m2. Redwood tree growing space efficiency (GSE; the ratio of stem volume increment to leaf area) was greatest on average among emergent overstory trees, followed by dominant and codominant overstory trees. There was no evidence of declining overstory tree GSE with increasing leaf area over the range of data collected. A nonlinear model predicted increasing understory tree GSE with increasing leaf area. Models that predict basal area and LAI were developed to permit implementation of GSE models from basic inventory data.
Double sampling may improve the efficiency of litterfall estimatesContribution No. 2335 of the New Hampshire Agricultural Experiment Station, Durham, N.H.
Authors: Dellenbaugh Mary , Ducey Mark J. , Innes James C.
Published: July 2007

The effort required for an extensive litterfall measurement campaign can be prohibitive. We propose a double sampling approach, in which a large set of traps is used in each stand to estimate total litterfall, and only a subset of these traps is sorted to the relevant components. We examine its feasibility using data from a regional litterfall study of eastern white pine ( Pinus strobus L.), in which the variables of interest were biomass of foliar litterfall from pine and nitrogen content of foliar litterfall from all vegetation. Double sampling was more efficient than simple random sampling but only if every trap received a rapid presorting to remove twigs and cones. The optimal strategy when pine foliar litterfall biomass was the target variable was to conduct full sorting on 33% of the traps. When foliar litterfall N was the target, sorting only 20% of the traps was optimal. Holding time costs constant, the variance of estimated pine foliar litterfall biomass could be reduced by 18%, whereas that for foliar litterfall N could be reduced by 49%. Alternately, when variance was held constant, the time cost could be reduced by 17% for pine foliar litterfall biomass or 44% for foliar litterfall N.
Effect of tree, stand, and site variables on the allometry of Eucalyptus globulus tree biomass
Authors: António Nuno , Tomé Margarida , Tomé José , Soares Paula , Fontes Luís
Published: July 2007

The objective of this study was to develop a system of compatible equations to estimate eucalyptus ( Eucalyptus globulus Labill.) tree aboveground biomass and biomass of tree components for forest biomass prediction across regional boundaries. Data came from 441 trees sampled on several sites (99 and 14 plots in planted and coppice regenerated stands, respectively) representative of the eucalyptus expansion area in Portugal. The system of equations, simultaneously fitted using seemingly unrelated regression, was based on the allometric model for the biomass of stem wood, stem bark, leaves, and branches. Total aboveground biomass was expressed as the sum of the biomass of the respective tree components. The study allowed the following conclusions: (i) there is a significant increase in the predictive ability of the models that include height (stem components) or crown length (crown components) as an additional predictor to diameter at 1.30 m; (ii) there is a clear effect of the stage of development of the stand on tree allometry, with a decreasing pattern of the allometric constants; (iii) no effect of stand density, site index or climate on tree allometry was found; and (iv) for practical purposes, the same system of equations can be used for planted and coppice regenerated stands.
Spread of beech bark disease in the eastern United States and its relationship to regional forest composition
Authors: Morin Randall S. , Liebhold Andrew M. , Tobin Patrick C. , Gottschalk Kurt W. , Luzader Eugene
Published: July 2007

Beech bark disease (BBD) is an insect–fungus complex involving the beech scale insect ( Cryptococcus fagisuga Lind.) and one of two canker fungi. Beech scale was introduced to Halifax, Nova Scotia around 1890, presumably with the fungus Neonectria coccinea var. faginata Lohm. The disease has subsequently spread through a large portion of the range of beech. We used historical maps of the extent of the advancing BBD front (defined by presence of scale insects) in North America to estimate its rate of spread as 14.7 ± 0.9 km/year. This estimate did not account for stochastic “jumps” by the scale insects to several disjunct locations; therefore, this rate is a conservative estimate. Comparison of the year of scale colonization with beech density did not suggest a relationship between the scale spread rate and beech density. Our analyses also indicated that BBD has invaded less than 30% of regions where beech is present, but it has invaded most of the regions where beech is a dominant component of stands. Despite regional increases in beech mortality following invasion, considerable amounts of live beech remain in invaded areas. Moreover, the volume of beech has increased in most areas, though generally at lower rates than that observed for associated tree species.
Estimating branch production in trembling aspen, Douglas-fir, jack pine, black spruce, and balsam fir
Authors: Bernier P.Y. , Lavigne M.B. , Hogg E.H. , Trofymow J.A.
Published: July 2007

Measuring net primary productivity of trees requires the measurement of total wood production of branches. Recent work on balsam fir ( Abies balsamea ) has shown that branch-wood production can be estimated as a function of foliage production. We extend the analysis to four other species found in the Canadian forest: black spruce ( Picea mariana ), jack pine ( Pinus banksiana ), Douglas-fir ( Pseudotsuga menziesii ), and trembling aspen ( Populus tremuloides ). Results show that the ratio of annual branch-wood production to annual foliage production is about 1.0 for conifer species (between 0.86 and 1.12) and 0.56 for aspen during a nondrought year. An analysis using field measurements of litterfall and stem-diameter increment from selected forested sites shows that branch-wood production accounts for a smaller proportion of aboveground net primary productivity in trembling aspen (15%–20%) than in conifer species (25%). Also, litterfall capture of small branches (<1 cm diameter) accounts for only 33% of branch detritus production in conifers and 50% in trembling aspen. This study supports the use of an alternative method for estimating branch-wood production that reduces the potential bias in field estimates of net primary productivity.
The demographic structure of European aspen (Populus tremula) populations in managed and old-growth boreal forests in eastern Finland
Authors: Latva-Karjanmaa Tarja , Penttilä Reijo , Siitonen Juha
Published: July 2007

European aspen ( Populus tremula L.) is a keystone species for biodiversity in boreal forests. However, large aspen have largely been removed from managed forests, whereas regeneration and the long-term persistence of mature trees in protected areas are matters of concern. We recorded the numbers of mature (≥20 cm diameter) aspen in old-growth and managed forests in eastern Finland, based on a large-scale inventory (11 400 ha, 36 000 living and dead trees). In addition, saplings and small aspen trees were surveyed on thirty-six 1 ha sample plots. The average volumes of mature living and dead aspen were 4.0 and 1.3 m3/ha in continuous old-growth forests and 0.2 and 0.6 m3/ha in managed forests, respectively. These results indicate that large aspen trees in managed forests are a legacy of the past, when forest landscapes were less intensively managed. We conclude that the long-term persistence of aspen in protected areas can only be secured by means of restoration measures that create gaps large enough for regeneration to occur. More emphasis should be given to sparing aspen during thinning and to retaining mature aspen during regeneration cutting in managed forests.
Ecosystem carbon accumulation following fallow farmland afforestation with red pine in southern Quebec
Authors: Ouimet Rock , Tremblay Sylvie , Périé Catherine , Prégent Guy
Published: July 2007

We assessed the organic C stocks and inferred their changes in vegetation biomass, forest floor, and soil using a 50 year chronosequence of red pine ( Pinus resinosa Ait.) plantations established on postagricultural fields in southern Quebec, Canada. The data come from soil and tree field surveys carried out in the 1970s in 348 sites. Organic C concentrations were usually measured in three major mineral soil horizons; for the remaining soil horizons, they were estimated using pedotransfer functions. The effect of soil order, drainage, and texture was analysed. Over 22 years, organic C accumulation rates (Mg C·ha–1·year–1) were 1.66 ± 0.03 in vegetation biomass, 0.56 ± 0.07 in forest floor, 0.86 ± 0.47 in loamy soils (0–100 cm), and  –0.18 ± 0.24 in sandy soils (0–100 cm). The greater rate of C accumulation in loamy soils was due to the contribution of the 30–100 cm subsoil layer. The overall net accumulation of organic C in these plantation ecosystems was estimated to 51.4 ± 4.8 Mg C·ha–1at 22 years. Soils of these plantations acted as a C sink in the first two decades, particularly in loamy soils compared with sandy soils, with no major differences among soil order or drainage.
A hierarchical analysis of stand structure, composition, and burn patterns as indicators of stand age in an Engelmann spruce – subalpine fir forest
Authors: Gass Tobah M. , Robinson Andrew P.
Published: July 2007

We studied the relationship between observed fire effects and stand age in a recently burned subalpine Engelmann spruce ( Picea engelmannii Parry ex. Engelm.) – subalpine fir ( Abies lasiocarpa (Hook.) Nutt.) forest in New Mexico. We installed a network of variable-radius plots to assess stand structure, and cored 379 trees to measure the spatial patterns of the stand ages with respect to fire boundaries. We found that pre-fire stand age and stand mortality were not significantly related at either of two spatial scales (p ≤ 0.33 and p ≤ 0.26). We also found that stand structure and stand composition were poor indicators of stand age. The random effects terms of a linear mixed-effects model revealed substantial heterogeneity in stand structure and composition with respect to age at fine spatial scales. Discussions of the factors contributing to stand-replacing fires in subalpine Engelmann spruce – subalpine fir forests might be improved by focusing on traits that are more reliably linked to fuel characteristics, rather than on the age of the stands.
Fuels on disturbed and undisturbed sites in the southern Appalachian Mountains, USA
Authors: Waldrop Thomas A. , Brudnak Lucy , Rideout-Hanzak Sandra
Published: July 2007

Fuel distribution in the southern Appalachian Mountain region was measured in over 1000 study plots that were stratified by topographic position (aspect and slope position) and disturbance history. Few fuel differences occurred among topographic positions for undisturbed plots, indicating that fuel accumulation is no greater on highly productive sites than on less productive sites. Litter was slightly higher on undisturbed upper slopes (4.2 t/ha) than on lower slopes (3.7 t/ha) but woody fuels showed no significant differences. Rhododendron ( Rhododendron spp.) and mountain laurel ( Kalmia latifolia L.) were less common than expected, occurring on 25% and 42% of sampled plots, respectively. Disturbance history and type played a greater role in determining fuel loads than did topographic position. Disturbances had occurred on 30% of sample plots within the past 10 years and were most common on exposed slopes. Litter was significantly lower in burned plots (3.5 t/ha vs. 4.0 t/ha in undisturbed plots). One-hour fuels (1.0 t/ha) were significantly higher on beetle-killed plots than on undisturbed plots (0.7 t/ha) while larger woody fuels tended to be greater in plots subjected to beetle attack, fire, and wind.
Modeling long-term tree growth curves in response to warming climate: test cases from a subtropical mountain forest and a tropical rainforest in Mexico
Authors: Ricker Martin , Gutiérrez-García Genaro , Daly Douglas C.
Published: July 2007

The Earth’s temperature has increased 0.6 °C over the last 100 years, and further climate change is predicted to potentially raise it by 3.5 °C over the next century. More than half of the global annual net primary production of biomass is estimated to occur in the tropics, especially tropical evergreen forest. In temperate forests, increasing temperature may extend the non-frost growing season, and thus increase the CO2sequestration rate, but some authors have also suggested a negative impact of warming in tropical forests from decreased photosynthetic activity. Using the PL model (Ricker and del Río 2004), we forecast growth of two Mexican tree species after climate warming. The model predicts the high-mountain species Pinus hartwegii Lindl. to decrease its expected relative growth throughout its lifetime by 10.6% as a consequence of a 0.6 °C temperature increase; in contrast, the tropical rainforest species Diospyros digyna Jacq. is predicted to increase its expected relative growth throughout its lifetime by 25.4%. The key factor appears to be the expected relationship between temperature and precipitation, rather than temperature alone. While one cannot expect a universal response across sites, some standing tropical rainforests such as those at Los Tuxtlas in Mexico may constitute a carbon sink in a changing climate.
Pedodiversity in an old-growth northern hardwood forest in the Huron Mountains, Upper Peninsula, Michigan
Authors: Scharenbroch B.C. , Bockheim J.G.
Published: July 2007

We investigated three primary causes of old-growth forest pedodiversity imposed by top-down trophic interactions, including pit and mound topography from past tree fall events, current canopy gaps from tree falls, and the influence of individual tree species on soil properties and processes. In this paper, we discuss the effects of pits, mounds, gaps, and individual tree species on pedodiversity in a single soil map unit in an old-growth northern hardwood forest. Pits and level areas had significantly greater soil organic matter, cation-exchange capacity, and exchangeable K and Ca contents than mounds. Gap subplots had significantly less cation-exchange capacity, K, Mg, and Ca compared with level areas within the contiguous forest. Base cations (K, Mg, and Ca) were significantly greater under sugar maple ( Acer saccharum Marsh.) compared with eastern hemlock ( Tsuga canadensis (L.) Carr.). Extractable P was significantly greater under yellow birch ( Betula alleghaniensis Britt.) compared with eastern hemlock. We quantified pedodiversity in an old-growth northern hardwood forest stand and single soil map unit using principal components analyses, ArcGIS, and biodiversity indices. Our results suggest that pedodiversity should be considered in soil survey and forest management.
QCD COLLISIONAL ENERGY LOSS IN AN INCREASINGLY INTERACTING QUARK–GLUON PLASMA
Authors: GAY DUCATI M. B. , GONÇALVES V. P. , MACKEDANZ L. F.
Published: July 2007

The discovery of the jet quenching in central Au + Au collisions at the Relativistic Heavy-Ion Collider (RHIC) at Brookhaven National Laboratory has provided clear evidence for the formation of strongly interacting dense matter. It has been predicted to occur due to the energy loss of high energy partons that propagate through the quark–gluon plasma. In this paper we investigate the dependence of the parton energy loss due to elastic scatterings in a parton plasma on the value of the strong coupling and its running with the evolution of the system. We analyze different prescriptions for the QCD coupling and calculate the energy and length dependence of the fractional energy loss. Moreover, the partonic quenching factor for light and heavy quarks is estimated. We found that the predicted enhancement of the heavy to light hadrons (D/π) ratio is strongly dependent on the running of the QCD coupling constant.
BRANE TILINGS
Authors: KENNAWAY KRISTIAN D.
Published: July 2007

We review and extend the progress made over the past few years in understanding the structure of toric quiver gauge theories; those which are induced on the worldvolume of a stack of D3-branes placed at the tip of a toric Calabi–Yau cone, at an "orbifold point" in Kähler moduli space. These provide an infinite class of four-dimensional [Formula: see text] superconformal field theories which may be studied in the context of the AdS/CFT correspondence. It is now understood that these gauge theories are completely specified by certain two-dimensional torus graphs, called brane tilings, and the combinatorics of the dimer models on these graphs. In particular, knowledge of the dual Sasaki–Einstein metric is not required to determine the gauge theory, only topological and symplectic properties of the toric Calabi–Yau cone. By analyzing the symmetries of the toric quiver theories we derive the dimer models and use them to construct the moduli space of the theory both classically and semiclassically. Using mirror symmetry the brane tilings are shown to arise in string theory on the worldvolumes of the fractional D6-branes that are mirror to the stack of D3-branes at the tip of the cone.
On the periodicity and magnitude of Late Carboniferous glacio-eustatie sea-level changes
Authors: MAYNARD J. R. , LEEDER M. R.
Published: July 2007

Data from sedimentary cycles in basins from northern England, the Appalachians and Midcontinent US afford an insight into periodicities and controls of Late Carboniferous glacio-eustatic sea-level changes. Lithofacies with identifiable palaeobathymetry are used to assess the magnitude of sea-level change in the Pennine Basin of northern England; the method yields a minimum value of 42m. Walsh power spectral analysis is employed to resolve periodicities of about 120ka within the Pennine Basin of northern England, 212, 140 and 93 ka within the Midcontinent US succession and 109, 84, 67, 63 ka within the Appalachian Basin. Within the Pennine Basin periodicities and magnitudes are found to be independent of their position within the basin thus any tectonism can be assumed to have had a negligible effect on the transgressions. A simplified modelled climatic curve is derived from Milankovitch parameters and Pleistocene δ
18
O data. This is used in a basin fill model that simulates the thermally subsiding Pennine Basin. The resulting distribution of marine deposits is seen to depend upon both the steady regional subsidence and the magnitude and extent of glacio-eustatic transgressions.
Hardgrounds, reworked concretion levels and condensed horizons in the Jurassic of western India: their significance for basin analysis
Authors: FÜRSICH F. T. , OSCHMANN W. , SINGH I. B. , JAITLY A. K.
Published: July 2007

Jurassic sediments in the shallow pericratonic basins of Kachchh and Rajasthan, western India, exhibit numerous signs of reduced sedimentation, omission, erosion and in situ reworking, in combination with synsedimentary cementation. Hardgrounds developed on carbonate shoals in the Bathonian of Rajasthan, whilst reworked concretion levels are characteristic of offshore siliciclastic sediments of the Callovian of Kachchh. A prominent marker horizon, the Oxfordian Dhosa Oolite Member, occurs throughout much of the Kachchh sub-basin and is a highly condensed unit characterized by hardgrounds, intraformational cobbles, reworked concretions, stromatolitic iron crusts, iron oncoids, and shell lags. Hardgrounds, reworked concretion levels, and condensation horizons are interpreted as the preserved relicts of transgressive pulses. Such pulses were possibly controlled by eustatic rise of sea level. Of at least equal importance, however, was a tectonic control which is demonstrated by the presence of small neptunian dykes, boulder beds derived from small submarine cliffs and rapid lateral facies and thickness changes in the Dhosa Oolite Member. These indications of extensional tectonics are thought to be connected to rifting and initial sea floor spreading between Africa and India.
Tectonic evolution of the northern Kenyan Rift
Authors: MORLEY C. K. , WESCOTT W. A. , STONE D. M. , HARPER R. M. , WIGGER S. T. , KARANJA F. M.
Published: July 2007

Recent geological fieldwork, radiometric age dating of volcanic rocks, gravity and seismic reflection surveys have considerably refined our understanding of the tectonic evolution of the northern Kenya Rift. These data reveal that deep, half-graben basins up to 7 km thick were initiated west of Lake Turkana probably during Late Oligocene-Early Miocene times. The basins, bounded by easterly dipping faults, trend along the western side of the rift from Lake Turkana to the Elgayo Escarpment-Tugen Hills area. Some rift basins were episodically active from the Oligocene to the Pliocene while others were only active for a few million years. Some sag basins may have developed during periods of rifting quiescence. In the Turkana area the location of faulting gradually shifted eastwards with time. Volcanism both preceded and accompanied rifting. Within the Turkana area, volcanism moved south and east with time, beginning about 33 Ma (probably preceding half graben formation by a few million years) and continued to the present day. Extension along faults is greater in the Turkana area (between 25-40 km) and decreases southwards to probably 5-10 km or less in the southern Kenya rift. This pattern of extension values agrees with deep seismic refraction work (KRISP), which indicates thin crust in the Turkana area (about 20 km) that thickens to about 35 km south of Lake Baringo. The extension values, crustal thinning, age of volcanism and the timing of faulting to the south all point towards a southerly propagation of the rift.
Silurian turbidite provenance and the closure of Iapetus
Authors: WILLIAMS D. M. , O’CONNOR P. D. , MENUGE J.
Published: July 2007

Subduction of Iapetus crust during the Caledonian orogeny has been seen by some authors as terminating at the end of Ordovician times and by others as continuing through the Silurian. We present petrological and chemical data which support a coeval arc origin for detritus in the Lettergesh Formation (Silurian), western Ireland. The arc, based on continental crust, lay to the north of the present outcrops of this formation, along the Laurentian margin of Iapetus, implying active oceanic subduction in the Silurian. This subduction may have been followed by some continental underplating around the middle of the Wenlock giving rise to a successor basin in Ireland and Scotland.
Geophysical investigation of the Honningsvåg igneous complex, Scandinavian Caledonides
Authors: TORSVIK T. H. , OLESEN O. , TRENCH A. , ANDERSEN T. B. , WALDERHAUG H. J. , SMETHURST M. A.
Published: July 2007

The Honningsvåg igneous complex within the Mageroy nappe, northern Norway, has marked magnetic and gravimetric signatures. Palaeomagnetic studies reveal a Siluro-Devonian (Scandian) dual-polarity remanence (NE and up—SW and down; mean declination = 045°, inclination = -38° and
a

95

=
8.4°). Rock-magnetic and petrological studies indicate a pure magnetite host for the remanent magnetization component. Magnetic-fabric ellipsoids delineate Dl and D2 Scandian structures affecting the area, and demonstrate an internal reclined fold-structure of the Honningsvåg igneous complex. Forward-modelling demonstrates that a short-wavelength, poúitive aeromagnetic anomaly (c. 700 nT) over the northwestern part of the complex is associated with an area of reverse remanent polarity (SW and down). Conversely, areas of normal remanence polarity (NE and up most common) are associated with magnetic ‘lows’ or ‘quiet’ zones. The gravity field in the vicinity of the complex displays a symmetrical positive anomaly of approximately 200 g.u. (wavelength 15 km). This can be attributed to a density contrast of approximately 0.20 Mg/m
3
between the gabbros of the Honningsvåg complex (2.93) and surrounding metasediments (2.73). An optimal geophysical and geological model demonstrates that the complex has been tilted through 90°, and now has the form of a steeply dipping reclined fold-structure extending to a depth of at least 6 km.

Palaeomagnetic remanence acquisition post-dates emplacement of the Magerøy nappe (late Dl), and probably originated during post-Dl uplift. Brittle, upper-crust, D2 deformation which continued into Devonian times, folded the Honningsvåg igneous complex and introduced a small but systematic dispersion in the palaeomagnetic remanence directions. The magnetization is, therefore, post-Dl but pre-D2 in age, and can be termed ‘syn-Scandian’. Palaeomagnetic and isotopic evidence suggests a syn-tectonic magnetization age of
c.
410 Ma. The palaeomagnetic pole (N7° and E344°) resembles that from the underlying Kalak nappe complex. It is therefore inferred that the Scandian emplacement of the Magerøy nappe was synchronous with a thermal event which affected the older and underlying Finnmarkian-defor-med Kalak nappe complex.
Petrological constraints and
PT
path of Devonian collapse tectonics within the Scandian mountain belt (Western Gneiss Region, Norway)
Authors: CHAUVET A. , KIENAST J. R. , PINARDON J. L. , BRUNEL M.
Published: July 2007

In Norway, post-Caledonian extension controlled the formation and sedimentation of Middle Devonian sedimentary basins. These ‘collapse basins’ were deposited along a low-angle extensional detachment fault on top of Caledonian high-grade metamorphic rocks of the Western Gneiss Region. This paper concerns the petrological analysis of eclogite and high-pressure micaschist collected within the extensional shear zone. Study of gneisses and micaschists surrounding these high-pressure rocks allows description of the complete
PT
path which characterized this area.

Application of appropriate geothermometers and geobarometers confirms that the retrograde evolution following high-pressure conditions (ll-15kbar at 500-600°C) was characterized by nearly isothermal decompression followed by amphibolite facies metamorphism. The shape of the
PT
path is compared with theoretical models of thermal evolution of continental orogenic crust during uplift. We can observe an increase in temperature during the first stages of decompression smaller than predicted by the models. Considering the evidence for extensional tectonic in the study area, we propose to explain such a small increase in temperature during the decompression by the intervention of extension which accelerates the collapse process and reduces the late-orogenic heating of the Caledonian thickened crust.
Variscan structure and its influence on post-Carboniferous basin development, Western Approaches Basin, SW UK Continental Shelf
Authors: HILLIS R. R. , CHAPMAN T. J.
Published: July 2007

Reflection seismic records from the Western Approaches Basin (SW UK Continental Shelf) reveal SSE-dipping reflection packages within the Variscan basement. These have been mapped and are believed to originate from Variscan thrusts. Orthogonal transfer faults are apparent as NNW-trending zones of discontinuity. Structural trends in the Permian-Mesozoic Western Approaches Basin parallel those of the underlying basement. An end-Variscan structural high in the northern part of the basin was progressively onlapped from the south during Permian times. This high may have been formed by thrust-driven tectonic thickening of the crust. During Late Jurassic-Early Cretaceous times Variscan thrusts were reactivated in the western part of the basin (Melville Basin) to form a half-graben. However, in the east (St Mary's Basin), the basin is more symmetrical, and Mesozoic reactivation of Variscan thrusts cannot be unequivocally demonstrated.
Upper Palaeozoic tectono-sedimentary evolution of the Arabian and adjoining plates
Authors: HUSSEINI M. I.
Published: July 2007

From the Devonian to possibly the early Carboniferous, the Arabian and adjacent plates were structurally affected by a regional Hercynian (Variscan) tectonic event. This tectonic event is interpreted to be the crustal response to regional compression caused by the initiation of subduction of the Palaeo-Tethyan oceanic crust near the margin of Gondwana along Turkey and Iran. The uplifted areas associated with this tectonic event were largely eroded during the late Carboniferous and early Permian when glacio-fluviatile and marginal marine conditions prevailed.

The Palaeozoic era closed in the late Permian with a major transgression which deposited massive carbonates over most of a peneplaned Arabian plate. Also in late Permian, as well as Triassic, active rifting along the Zagros suture projected extensional stresses across the Arabian plate causing substantial extensional movements along most major basement-controlled, fault systems.
Nature and origin of a laterally extensive alluvial sandstone body in the Middle Jurassic Scalby Formation
Authors: ALEXANDER Jan
Published: July 2007

Complex internal structure is characteristic of many high-sinuosity channel deposits. This is particularly true of meander-belts formed in lower delta plain or coastal plain settings, as demonstrated by an 'exhumed meander-belt' exposed for 3.5 km along the coast north of Scarborough, Yorkshire. Point bar, counterpoint bar, channel plug, floodplain lake and sheet flood deposits all contribute significantly to the internal architecture of the sandstone body. Units that are recognizably of point bar lateral-accretion origin, make up a little over 24% of the area of the 'exhumed meander-belt', counterpoint bar deposits over 1%. The bulk of the sandstone body is composed of channel plug and sheet flood sandstones and units whose origin is not easily recognizable due to partial preservation. The structure of the point bar and counterpoint bar deposits indicate that channels of a variety of types were responsible for the deposit. Although, in general the channels were small, mixed load and highly sinuous. The counterpoint bar deposits observed in the wave-cut platform vary in curvature, composition and structure. Counterpoint bars are sedimentary packages deposited on or near the outer bank of an alluvial channel meander. Four theoretical mechanisms for producing these deposits are suggested: (a) flow separation in a tight bend of a suspension load dominated river; (b) changing radius of curvature of a river bend; (c) local cut-bank embayment development during high stage flow filling at lower flow conditions and (d) complex meander loop development. Of these only two have been recognized in the 'exhumed meander-belt'.
GOLDFINDER: a knowledge-based system for mineral prospecting
Authors: HAWKES D. D.
Published: July 2007

GOLDFINDER is a prototype knowledge-based system which assesses the potential of a gold prospect and gives advice on the best locality to site a drill hole. By interaction with the user, the system establishes a dynamic database containing, at a sophisticated level, information about the main lithologies, the nature of any mineralization or alteration, and the structural features of the prospect. Using a method of intersecting loci, the system locates a drill site with a precision governed only by the scale of the prospect map.

GOLDFINDER is written in PROLOG within a Macintosh environment and utilizes an interpreter based on two-valued logic. Knowledge is coded partly as semantic networks but mainly as a production system with a structured rule base. A conventional ‘how’ explanation is improved by appending the reason why the expert included a particular rule. A powerful ‘what if’ facility enables the geologist to change the parameters and use the system for modelling purposes. At present, the domain of GOLDFINDER is restricted to Archaean greenstone belts. The present knowledge base could be removed to provide a shell for prospecting any metalliferous mineral deposit.
The Cell Biology of Synaptic Plasticity: AMPA Receptor Trafficking
Authors: Shepherd Jason D. , Huganir Richard L.
Published: July 2007

The cellular processes that govern neuronal function are highly complex, with many basic cell biological pathways uniquely adapted to perform the elaborate information processing achieved by the brain. This is particularly evident in the trafficking and regulation of membrane proteins to and from synapses, which can be a long distance away from the cell body and number in the thousands. The regulation of neurotransmitter receptors, such as the AMPA-type glutamate receptors (AMPARs), the major excitatory neurotransmitter receptors in the brain, is a crucial mechanism for the modulation of synaptic transmission. The levels of AMPARs at synapses are very dynamic, and it is these plastic changes in synaptic function that are thought to underlie information storage in the brain. Thus, understanding the cellular machinery that controls AMPAR trafficking will be critical for understanding the cellular basis of behavior as well as many neurological diseases. Here we describe the life cycle of AMPARs, from their biogenesis, through their journey to the synapse, and ultimately through their demise, and discuss how the modulation of this process is essential for brain function.
Regulation of Sterol Synthesis in Eukaryotes
Authors: Espenshade Peter J. , Hughes Adam L.
Published: July 2007

Cholesterol is an essential component of mammalian cell membranes and is required for proper membrane permeability, fluidity, organelle identity, and protein function. Cells maintain sterol homeostasis by multiple feedback controls that act through transcriptional and posttranscriptional mechanisms. The membrane-bound transcription factor sterol regulatory element binding protein (SREBP) is the principal regulator of both sterol synthesis and uptake. In mammalian cells, the ER membrane protein Insig has emerged as a key component of homeostatic regulation by controlling both the activity of SREBP and the sterol-dependent degradation of the biosynthetic enzyme HMG-CoA reductase. In this review, we focus on recent advances in our understanding of the molecular mechanisms of the regulation of sterol synthesis. A comparative analysis of SREBP and HMG-CoA reductase regulation in mammals, yeast, and flies points toward an equilibrium model for how lipid signals regulate the activity of sterol-sensing proteins and their downstream effectors.
Nitric oxide increases GLUT4 expression and regulates AMPK signaling in skeletal muscle
Authors: Lira Vitor A. , Soltow Quinlyn A. , Long Jodi H. D. , Betters Jenna L. , Sellman Jeff E. , Criswell David S.
Published: July 2007

Nitric oxide (NO) and 5′-AMP-activated protein kinase (AMPK) are involved in glucose transport and mitochondrial biogenesis in skeletal muscle. Here, we examined whether NO regulates the expression of the major glucose transporter in muscle (GLUT4) and whether it influences AMPK-induced upregulation of GLUT4. At low levels, the NO donor S-nitroso- N-penicillamine (SNAP, 1 and 10 μM) significantly increased GLUT4 mRNA (∼3-fold; P < 0.05) in L6 myotubes, and cotreatment with the AMPK inhibitor compound C ablated this effect. The cGMP analog 8-bromo-cGMP (8-Br-cGMP, 2 mM) increased GLUT4 mRNA by ∼50% ( P < 0.05). GLUT4 protein expression was elevated 40% by 2 days treatment with 8-Br-cGMP, whereas 6 days treatment with 10 μM SNAP increased GLUT4 expression by 65%. Cotreatment of cultures with the guanylyl cyclase inhibitor 1H-[1,2,4]oxadiazolo[4,3,-a]quinoxalin-1-one prevented the SNAP-induced increase in GLUT4 protein. SNAP (10 μM) also induced significant phosphorylation of α-AMPK and acetyl-CoA carboxylase and translocation of phosphorylated α-AMPK to the nucleus. Furthermore, L6 myotubes exposed to 5-aminoimidazole-4-carboxamide-1-β-d-ribofuranoside (AICAR) for 16 h presented an approximately ninefold increase in GLUT4 mRNA, whereas cotreatment with the non-isoform-specific NOS inhibitor NG-nitro-l-arginine methyl ester, prevented ∼70% of this effect. In vivo, GLUT4 mRNA was increased 1.8-fold in the rat plantaris muscle 12 h after AICAR injection, and this induction was reduced by ∼50% in animals cotreated with the neuronal and inducible nitric oxide synthases selective inhibitor 1-(2-trifluoromethyl-phenyl)-imidazole. We conclude that, in skeletal muscle, NO increases GLUT4 expression via a cGMP- and AMPK-dependent mechanism. The data are consistent with a role for NO in the regulation of AMPK, possibly via control of cellular activity of AMPK kinases and/or AMPK phosphatases.
Alpha One Antitrypsin Deficiency: From Gene to Treatment
Authors: Wood Alice M. , Stockley Robert A.
Published: July 2007

α1-antitrypsin deficiency is a genetic disorder which contributes to the development of chronic obstructive pulmonary disease, bronchiectasis, liver cirrhosis and panniculitis. The discovery of α1-antitrypsin and its function as an antiprotease led to the protease-antiprotease hypothesis, which goes some way to explaining the pathogenesis of emphysema. This article will review the clinical features of α1-antitrypsin deficiency, the genetic mutations known to cause it, and how they do so at a molecular level. Specific treatments for the disorder based on this knowledge will be reviewed, including α1-antitrypsin replacement, gene therapy and possible future therapies, such as those based on stem cells.
Expansion of B Cells Is Necessary for the Induction of T-Cell Tolerance Elicited through the Anterior Chamber of the Eye
Authors: Ashour Hossam M. , Niederkorn Jerry Y.
Published: July 2007

Antigens injected into the anterior chamber (AC) of the eye induce a form of peripheral immune tolerance termed anterior chamber-associated immune deviation (ACAID). ACAID is initiated by F4/80+ ocular antigen-presenting cells (APC) which capture ocular antigens and migrate to the spleen where they transfer antigenic peptides to B cells, which act as ancillary APC for the induction of T-regulatory cells (Treg) that inhibit delayed-type hypersensitivity (DTH) responses. Here we show that ocular-like APC induce the expansion of tolerogenic splenic B cells. Furthermore, we show that inhibiting B-cell proliferation with either mitomycin-c or γ-irradiation abolishes the ability of B cells to induce Treg. To our knowledge, this is the first study to report that B-cell proliferation is needed for B-cell-induced T-cell tolerance.
Blockade of IP-10/CXCR3 Promotes Progressive Renal Fibrosis
Authors: Nakaya Izaya , Wada Takashi , Furuichi Kengo , Sakai Norihiko , Kitagawa Kiyoki , Yokoyama Hitoshi , Ishida Yuko , Kondo Toshikazu , Sugaya Takeshi , Kawachi Hiroshi , Shimizu Fujio , Narumi Shosaku , Haino Makoto , Gerard Craig , Matsushima Kouji , Kaneko Shuichi
Published: July 2007

Background/Aim: Fibrosis is a hallmark of progressive organ disease. The 10-kDa interferon-inducible protein IP-10/CXCL10 is a potent chemoattractant for activated T lymphocytes, natural killer cells, and monocytes. However, the involvement of IP-10 in the pathogenesis of renal diseases viaits receptor, CXCR3, remains unclear. To contribute to the clarification of this issue was the aim of this study. Methods: The impacts of IP-10 on renal fibrosis were investigated in a unilateral ureteral obstruction model in CXCR3-deficient mice and mice treated with anti-IP-10-neutralizing monoclonal antibody. Anti-IP-10 monoclonal antibody (5 mg/kg/day) was injected intravenously once a day until sacrifice on days 1, 4, or 7 after treatment. The effects of IP-10 were confirmed in cultured tubular epithelial cells. Results: IP-10 and CXCR3 were upregulated in progressive renal fibrosis. Blockade of IP-10/CXCR3 promotes renal fibrosis, as evidenced by increases in interstitial fibrosis and hydroxyproline contents, concomitant decrease in hepatocyte growth factor expression, and converse increase in transforming growth factor-β1 in diseased kidneys. IP-10 blockade affected neither macrophage nor T cell infiltration in diseased kidneys. Conclusion: These results suggest that blockade of IP-10 via CXCR3 contributes to renal fibrosis, possibly by upregulation of transforming growth factor-β1, concomitant with downregulation of hepatocyte growth factor.
TGF-Beta Treatment Modulates PD-L1 and CD40 Expression in Proximal Renal Tubular Epithelial Cells and Enhances CD8+ Cytotoxic T-Cell Responses
Authors: Starke Astrid , Wüthrich Rudolf P. , Waeckerle-Men Ying
Published: July 2007

Background/Aim: TGF-β expression is increased in immune-mediated and fibrotic renal diseases and modulates the tubulointerstitial T-cell response. We examined whether TGF-β changes the expression of PD-L1 and CD40 in the renal proximal tubular epithelial cell (TEC), and whether the activation of CD8+ cytotoxic T cells (CTLs) is influenced by TGF-β treatment of TECs. Methods: Murine TECs were treated with TGF-β or IFN-γ. The expression of PD-L1 and CD40 was examined with RT-PCR and flow cytometry. To investigate if TGF-β treatment influenced the antigen presentation capacity of TECs, OT-1 CTLs were co-incubated with TGF-β-treated, OVA257–264 peptide-pulsed congeneic TECs. The cytotoxicity of OT-1 CTLs was estimated by their capacity to produce IFN-γ and their cytolytic activity. Results: TGF-β treatment lead to a transition in morphology of renal TECs and downregulated the basal and the IFN-γ-stimulated PD-L1 expression in TECs. Interestingly, TGF-β treatment of TECs increased the constitutive and IFN-γ-induced CD40 expression. In contrast to IFN-γ which reduced the CTL activity, TGF-β treatment of TECs elevated the OVA-specific CTL response. Conclusion: Our data show that TGF-β changed the cellular phenotype and the expression of PD-L1 and CD40 on TECs and enhanced the activity of OVA peptide-specific CD8+ T cells. TGF-β may thereby play an important role in the progression of renal tubulointerstitial damage in CD8+ T-cell-mediated renal diseases.
Characterization of Developing Bowel Transplanted from Transgenic Erythropoietin Receptor-Deficient Mouse Embryos
Authors: Mascher-Denen Marcella , McPherson Ronald J. , Kapur Raj P. , Juul Sandra E.
Published: July 2007

Background: Erythropoietin (Epo) receptors (EpoR) are present in embryonic and postnatal mammalian bowel, and activation of EpoR signaling with recombinant Epo (rEpo) has trophic effects. Transgenic mice with absent Epo function are embryonic lethal, so it is not known whether Epo function is required for bowel development. Objective: To characterize bowel structure in the absence of EpoR signaling. Methods: Heterozygous EpoR knockout mice were mated. Bowel segments from their embryos were dissected and transplanted beneath the renal capsule of adult wild-type mice and residual embryo tissue was excised for genotyping. Transplants were harvested at 7, 14 or 21 days. The transplanted bowel segments were immunostained to identifyproliferation (BrdU+), as well as neuronal (PGP9.5+), endothelial (vWF+), and neuroendocrine (synaptophysin+) cells. Gross and microscopic characteristics of intestinal differentiation were evaluated. Results: 50 transplants were performed: bowel from 49 embryos survived to harvest and 43 showed evidence of bowel development with appropriate small or large intestinal features. No differences in morphology, immunolabeling, or BrdU incorporation were observed between homozygous-null, heterozygote or wild-type bowel. Smooth muscle and mucosal cells were present, along with neuronal, endothelial, and neuroendocrine cells in all genotypes. Conclusions: Enteric EpoR signaling is not essential for intestinal morphogenesis.