bluuebunny/crossref_metadata_2025_split huggingface dataset:
Matrix metalloproteinase‐12 gene expression in human vascular smooth muscle cells
Authors: Wu Lihua , Tanimoto Akihide , Murata Yoshitaka , Sasaguri Takakazu , Fan Jianglin , Sasaguri Yasuyuki , Watanabe Teruo 
Published: March 2003

AbstractBackground: Matrix metalloproteinases (MMPs) play an important role in smooth muscle cell (SMC) migration and proliferation during vascular remodelling. To investigate the expression of MMP‐12 by SMCs, we examined the protein secretion and mRNA expression of MMP‐12 by cultured medial SMCs and intimal SMCs derived from human aortic atherosclerotic lesions. To further elucidate the molecular mechanism for MMP‐12 expression in SMCs, we determined the sequence requirements for MMP‐12 gene transcriptional activity.Results: Cultured medial SMCs and intimal SMCs showed substantial MMP‐12 expression at both the protein and mRNA levels. A series of 5′‐deletion and site‐directed mutants of the human MMP‐12 promoter demonstrated that an AP‐1 site spanning −81 to −75 bp was critical for the MMP‐12 promoter activity in SMCs. An electrophoretic mobility shift assay confirmed the AP‐1 binding activity in SMCs and showed that the protein bound to the AP‐1 site consisted predominantly of c‐Jun, JunD and Fra‐1. Two structurally different inhibitors of phosphatidylinositol 3‐kinase, wortmannin and LY294002, inhibited MMP‐12 transcriptional activity and AP‐1 binding.Conclusion: These results indicated the expression of MMP‐12 in vascular SMCs and showed that the MMP‐12 gene expression was dependent on the AP‐1 binding activity. Phosphatidylinositol 3‐kinase signalling may be involved in MMP‐12 transcriptional activation through AP‐1 binding activity.
Very high resolution 3D marine seismic data processing for geotechnical applications
Authors: Marsset  , Missiaen  , De Roeck  , Noble  , Versteeg  , Henriet  
Published: March 2003

The processing of a small‐scale, very high resolution (VHR) shallow marine 3D data volume is described. The data were acquired over a small clay diapir, on the river Schelde, in 1990. Using an array of 12 dual‐channel microstreamers towed from a catamaran, a network of 1 m × 1 m bins could be produced over an area of 50 m × 180 m (< 100 m penetration). Positioning was performed with an auto‐tracking laser ranging system, assuring an absolute accuracy of a few decimetres.Preliminary processing steps included tidal correction and multiple removal. An important step concerned the application of 3D prestack Kirchhoff depth migration. Indeed this processing allows easy handling of the exact positions of both source and receivers as the latter were not set out on a conventional regular grid due to navigation difficulties. Because of the restricted data volume and the more‐or‐less stratified medium, a 1D velocity model could be used. This allowed a considerable simplification of the migration algorithm, based on summation. Traveltimes were calculated only once, using a 2D time grid with 0.1 m intervals.This migration method proved very efficient, greatly improving the seismic image, and involved only limited CPU time on a small computer (Sparc 10 workstation). It clearly demonstrates that advanced seismic processing can form a valuable and economically feasible tool for VHR shallow subsurface 3D seismics, as long as the velocity field is not too complex. This method should therefore no longer be restricted to large computers and hydrocarbon exploration, but should also become a routine for VHR 3D shallow seismic work.
Selection of the wavenumbers k using an optimization method for the inverse Fourier transform in 2.5D electrical modelling
Authors: Xu Shi‐zhe , Duan Ben‐chun , Zhang Da‐hai 
Published: March 2003

AbstractAn optimization method is used to select the wavenumbers k for the inverse Fourier transform in 2.5D electrical modelling. The model tests show that with the wavenumbers k selected in this way the inverse Fourier transform performs with satisfactory accuracy.
The effect of subsurface pipes on apparent‐resistivity measurements
Authors: Vickery Anna C. , Hobbs Bruce A. 
Published: March 2003

Subsurface conducting pipes can be either a target or a noise source in geophysical surveying. Their effect as a noise source in resistivity imaging can be so severe as to render the geophysical data uninterpretable. A method is developed here for identifying, locating and removing the effects of subsurface conducting pipes from image data, thus revealing the background resistivity structure.A previously known analytic solution for the potential distribution produced by current injection in a uniform half‐space containing an infinitely long conducting cylinder is used to calculate apparent resistivities corresponding to electrode arrays on the surface of the half‐space. Most results concern the Wenner array and an examination is made of the effects produced by varying the electrode spacing and the depth, size and orientation of the pipe with respect to the array. A method is developed for locating pipes in resistivity image data by cross‐correlation of the analytic solution with the measured field data. Pipe effects are then removed by multiplying each datum point in the measurements by the reciprocal of the corresponding value in the analytic solution. The success of the method is demonstrated by applications to synthetic data sets involving one or two pipes embedded in non‐uniform half‐spaces.In further examples, the method is applied to some measured resistivity images from an ex‐industrial site (a former oil distribution terminal), where an electromagnetic survey had previously revealed a labyrinth of underground pipes. The method is shown to be successful in removing the effects of the pipes to reveal the underlying geology.
Deep structure of the northeastern margin of the Parnaiba Basin, Brazil, from magnetotelluric imaging
Authors: Mohamed Adel K. , Meju Maxwell A. , Fontes Sergio L. 
Published: March 2003

ABSTRACTThe magnetotelluric (MT) method has been applied to the determination of the deep resistivity structure of the northeastern margin of the Parnaiba Basin. Transient electromagnetic (TEM) and MT data were collected in early 1999 along a 95 km long N–S line, extending from the coast across the projected subcrop position of a discontinuous fault found to the west of the study area that is believed to be a possible basin‐bounding fault. The MT data were processed to yield the TE‐ and TM‐mode responses and then corrected for static shift using central‐loop and single‐loop TEM data, respectively. Regularized 2D MT inversion was subsequently undertaken using a structured initial model with the near‐surface constrained by TEM inversion results. As a consistency check, we performed another set of 2D inversions using different smooth initial models. The various optimal 2D inversion models show clearly the presence of a major basement trough, over 2 km deep, located about 70 km from the coast. We interpret it as possibly marking the main basin margin and suggest that it may have implications for groundwater resource development in the area.
Wave velocities and attenuation of shaley sandstones as a function of pore pressure and partial saturation
Authors: Pham Nam H. , Carcione José M. , Helle Hans B. , Ursin Bjørn 
Published: March 2003

ABSTRACTWe obtain the wave velocities and quality factors of clay‐bearing sandstones as a function of pore pressure, frequency and partial saturation. The model is based on a Biot‐type three‐phase theory that considers the coexistence of two solids (sand grains and clay particles) and a fluid mixture. Additional attenuation is described with the constant‐Q model and viscodynamic functions to model the high‐frequency behaviour. We apply a uniform gas/fluid mixing law that satisfies the Wood and Voigt averages at low and high frequencies, respectively. Pressure effects are accounted for by using an effective stress law. By fitting a permeability model of the Kozeny– Carman type to core data, the model is able to predict wave velocity and attenuation from seismic to ultrasonic frequencies, including the effects of partial saturation. Testing of the model with laboratory data shows good agreement between predictions and measurements.
Organic matter accumulation following fires in a moorland soil chronosequence
Authors: Haslam S. F. I. , Chudek J. A. , Goldspink C. R. , Hopkins D. W. 
Published: March 2003

AbstractSevere fires in 1957 and 1976 removed the vegetation and soil organic matter from the litter layers and organic horizons of soils at two adjacent moorland sites leaving exposed the uppermost mineral horizon of the soil. In the period since, plant recolonization and soil organic matter reaccumulation have occurred to give a chronosequence. Assuming no major changes in the carbon and nitrogen content of the unburned soil since 1957, the rates of accumulation of soil C and N were estimated to be 0.035 kg C m–2 y–1 and 0.001 kg N m–2 y–1 over the first 19 years, and 0.50 kg C m–2 y–1 and 0.023 kg N m–2 y–1 over the period from 19 to 38 years after burning. Solid‐state 13C NMR (cross‐polarization, magic angle spinning 13C nuclear magnetic resonance spectroscopy) showed that the ratio of alkyl‐ and methyl‐C‐to‐O‐alkyl‐C increased with stage of decomposition and in the unburned soil with decreasing particle‐size. For the organic matter that had reaccumulated in the 1957‐burned soil, the alkyl‐C‐to‐O‐alkyl‐C ratio of the > 2000 μm and 2000–250 μm particle‐size fractions were greater than those of the corresponding size fractions from the unburned soil, indicating that the reaccumulated soil organic matter was subject to decomposition but limited fragmentation or comminution.
Biomass and compositional changes occur in chalk grassland turves exposed to elevated CO2 for two seasons in FACE
Authors: Warwick Kevin Robert , Taylor Gail , Blum Herbert 
Published: March 2003

AbstractArtificial turves composed of 7 chalk grassland species (Festuca ovina L.; Briza media L.; Bromopsis erecta (Hudson) Fourr.; Plantago media L.; Sanguisorba minor Scop.; Anthyllis vulneraria L. and Lotus corniculatus L.) were grown from seed and exposed to two seasons of elevated (600 μmol mol–1) and ambient (340 μmol mol–1) CO2 concentrations in free air CO2 enrichment (ETH‐FACE, Zurich). The turves were clipped regularly to a height of 5 cm and assessed for above ground biomass production and relative abundance based on accumulated clipped dry biomass as well as by point quadrat recording. Below ground biomass production was assessed with root in‐growth bags during the second season of growth.Increases in total biomass (> 30%) were noted in elevated CO2, but the differences did not become significant until the second season of growth. Individual species’ biomass varied in response to elevated CO2, with significant increases in biomass in elevated CO2 turves for both legume species, and no significant CO2 effect on S. minor or P. media. An initial positive CO2 effect on biomass of combined grass species was reversed by the end of the experiment with less biomass and a significantly smaller proportion of total biomass present in elevated CO2, which was attributed primarily to changes in proportion of F. ovina.Species relative abundance was significantly affected by elevated CO2 in the final 4 of the 6 clip events, with the legume species increasing in proportion at the expense of the other species, particularly the grasses. Root length and dry weight were both significantly increased in elevated CO2 (77% and 89%, respectively), and these increases were greater than increases in shoot biomass (36%) from the same period.Species responses to elevated CO2, within the model community, were not consistent with predictions made from data on individual species, leading to the conclusion that responses to elevated CO2, at the community level, and species within the community level, are the result of direct physiological effects and indirect competitive effects. These conclusions are discussed with respect to the ecological responses of natural communities, and the chalk grassland community in particular, to elevated CO2.
Recent Juniperus occidentalis (Western Juniper) expansion on a protected site in central Oregon
Authors: Knapp PauL. A. , Soulé Peter T. 
Published: March 2003

AbstractThe expansion of Juniperus occidentalis (western juniper) has been extensive in the last century, and increases in density and cover have been linked with the indirect effects of domestic livestock grazing (i.e. cessation of periodic fires, increases of nurse‐plant sites), and more favourable climatic conditions. In this study, we document changes in vegetation (including J. occidentalis) in central Oregon over a 23‐year period and relate these changes to their probable causes. In June 1995 we returned to the Horse Ridge Research Natural Area (HRRNA), a site that has a history of minimal anthropogenic impacts, to replicate a 1972 vegetation survey. Using the canopy‐intercept method, line intercept method, and aerial photography analysis to measure herbaceous cover, shrub cover and tree cover, respectively, we found significant changes had occurred in the 23‐year period between studies. Relative changes of tree, shrub, and perennial herbaceous cover were 59%, 7%, and – 38%, respectively. Relative increases in J. occidentalis density, as measured by the number of clumps and the number of stems, were 37% and 53%, respectively. Mean maximum height of J. occidentalis had increased by 10%. We examined the role of potentially confounding influences (e.g. fire, grazing, pathogens, climatic variability) and found that none of the traditional mechanisms implicated in J. occidentalis expansion adequately explained the observed changes. We suggest that the role of biological inertia of both anthropogenic and natural means may have had a profound effect on the J. occidentalis ecology of HRRNA.
Effects of soil warming during spring on photosynthetic recovery in boreal Norway spruce stands
Authors: Bergh Johan , Linder SunE. 
Published: March 2003

AbstractThe effect of soil thawing and soil temperature on postwinter recovery of photosynthetic capacity was studied, during late spring and early summer, in Norway spruce stands in northern Sweden. Soil temperature was manipulated by means of buried heating cables. The warming treatment was applied to stands with low (natural) and high (fertilized) availability of nutrients. Soil thawing, expressed as water availability, was followed by means of sapflow in stems, and shoot water potentials. The recovery of photosynthetic capacity was assessed by measuring the rate of light‐saturated photosynthesis (Amax), and maximum photochemical efficiency of photosystem II in detached shoots, and chlorophyll a fluorescence. Accumulation of starch reserves in the needles was followed as an independent indicator of photosynthetic performance in situ. Snowmelt and soil thawing occurred more than one month earlier in heated than in unheated plots. This was expressed both as sapflow and as differences in shoot water potential between treatments. During May, the rates of Amax were significantly higher on heated than on control plots. The effect of soil warming on Amax was, however, not reflected in chlorophyll fluorescence or needle starch content. The time course of the recovery of photosynthetic capacity was mainly controlled by mean air temperature and by the frequency of severe night frosts, and to a lesser extent by earlier soil thawing and higher soil temperatures.
A test of the effect of supplemental UV‐B radiation on the common frog, Rana temporaria L., during embryonic development
Authors: Cummins Clive P. , Greenslade Peter D. , Mcleod Andrew R. 
Published: March 2003

AbstractThe release of certain man‐made chemicals has led to recurrent, seasonal destruction of ozone in the upper atmosphere, allowing more solar radiation in the UV‐B waveband to reach the Earth. Consequently, many amphibians may suffer increased exposure to UV‐B at various stages in their lives. Embryonic stages of species which spawn in the spring, in shallow, open water, are at high risk of increased exposure. We exposed newly fertilized eggs of one such species, Rana temporaria L., to sunlight with and without supplemental UV‐B. We used outdoor arrays of lamps to simulate the increase in UV‐B which might result from previously documented ozone depletion. From immediately after fertilization to when hatchlings began feeding, ambient solar UV‐B, weighted for DNA‐damaging potential, was supplemented by ≈ 81% in 1995 and 113% in 1996. These levels of supplementation approximated the increase in solar UV‐B expected to result from losses of 21% and 25%, respectively, of the total amount of ozone in the atmospheric column, relative to pre‐ozone‐depletion values. We found no evidence that these additions of UV‐B radiation increased the incidence of mortality or overt developmental abnormality among embryos. We stress the need for appropriate dosimetry in studies of effects of UV‐B on organisms.
Acclimation of respiration to temperature and CO2 in seedlings of boreal tree species in relation to plant size and relative growth rate
Authors: Tjoelker MarK. G. , Oleksyn Jacek , Reich Peter B. 
Published: March 2003

SummaryThe role of acclimation of dark respiration to temperature and CO2 concentration and its relationship to growth are critical in determining plant response to predicted global change. We explored temperature acclimation of respiration in seedlings of tree species of the North American boreal forest. Populus tremuloides, Betula papyrifera, Larix laricina, Pinus banksiana, and Picea mariana plants were grown from seed in controlled‐environments at current and elevated concentrations of CO2 (370 and 580 μmol mol–1) in combination with three temperature treatments of 18/12, 24/18, and 30/24 °C (light/dark period). Specific respiration rates of roots and shoots acclimated to temperature, damping increases in rates across growth‐temperature environments compared to short‐term temperature responses. Compared at a standard temperature, root and shoot respiration rates were, on average, 40% lower in plants grown at the highest compared to lowest growth temperature. Broad‐leaved species had a lower degree of temperature acclimation of respiration than did the conifers. Among species and treatment combinations, rates of respiration were linearly related to size and relative growth rate, and relationships were comparable among growth environments. Specific respiration rates and whole‐plant respiratory CO2 efflux as a proportion of daily net CO2 uptake increased at higher growth temperatures, but were minimally affected by CO2 concentration. Whole‐plant specific respiration rates were two to three times higher in broad‐leaved than coniferous species. However, compared to faster‐growing broad‐leaved species, slower‐growing conifers lost a larger proportion of net daily CO2 uptake as respiratory CO2 efflux, especially in roots. Interspecific variation in acclimation responses of dark respiration to temperature is more important than acclimation of respiration to CO2 enrichment in modifying tree seedling growth responses to projected increases in CO2 concentration and temperature.
Interactions of tropospheric CO2 and O3 enrichments and moisture variations on microbial biomass and respiration in soil
Authors: Islam K. R. , Mulchi C. L. , Ali A. A. 
Published: March 2003

SummarySoil microbial biomass C (Cmic) is a sensitive indicator of trends in organic matter dynamics in terrestrial ecosystems. This study was conducted to determine the effects of tropospheric CO2 or O3 enrichments and moisture variations on total soil organic C (Corg), mineralizable C fraction (CMin), Cmic, maintenance respiratory (qCO2) or Cmic death (qD) quotients, and their relationship with basal respiration (BR) rates and field respiration (FR) fluxes in wheat‐soybean agroecosystems. Wheat (Triticum aestivum L.) and soybean (Glycine max. L. Merr) plants were grown to maturity in 3‐m dia open‐top field chambers and exposed to charcoal‐filtered (CF) air at 350 μL CO2 L−1; CF air + 150 μL CO2 L−1; nonfiltered (NF) air + 35 nL O3 L−1; and NF air + 35 nL O3 L−1 + 150 μL CO2 L−1 at optimum (− 0.05 MPa) and restricted soil moisture (− 1.0 ± 0.05 MPa) regimes. The + 150 μL CO2 L−1 additions were 18 h d−1 and the + 35 nL O3 L−1 treatments were 7 h d−1 from April until late October. While Corg did not vary consistently, CMin, Cmic and Cmic
fractions increased in soils under tropospheric CO2 enrichment (500 μL CO2 L−1) and decreased under high O3 exposures (55 ± 6 nL O3 L−1 for wheat; 60 ± 5 nL O3 L−1 for soybean) compared to the CF treatments (25 ± 5 nL O3 L−1). The qCO2 or qD quotients of Cmic were also significantly decreased in soils under high CO2 but increased under high O3 exposures compared to the CF control. The BR rates did not vary consistently but they were higher in well‐watered soils. The FR fluxes were lower under high O3 exposures compared to soils under the CF control. An increase in Cmic or Cmic
fractions and decrease in qCO2 or qD observed under high CO2 treatment suggest that these soils were acting as C sinks whereas, reductions in Cmic or Cmic
fractions and increase in qCO2 or qD in soils under elevated tropospheric O3 exposures suggest the soils were serving as a source of CO2.
Yield response of Lolium perenne swards to free air CO2 enrichment increased over six years in a high N input system on fertile soil
Authors: Daepp Markus , Suter Daniel , Almeida José P. F. , Isopp Hubert , Hartwig Ueli A. , Frehner Marco , Blum Herbert , Nösberger Josef , Lüscher Andreas 
Published: March 2003

SummaryAfter a step increase in the atmospheric partial pressure of CO2 (pCO2), the availability of mineral N may be insufficient to meet the plant's increased demand for N. Over time, however, the ecosystem may adapt to the new conditions, and a new equilibrium may be established in the fluxes of C and N. This would result in a higher dry mass (DM) yield response of the plants to elevated pCO2.The effect of elevated atmospheric pCO2 (60 Pa pCO2) was studied in Lolium perenne L. swards with two N fertilization treatments (14 and 56 g m−2 y−1) in a six‐year FACE (Free Air Carbon dioxide Enrichment) experiment. In the high N treatment, the input of N with fertilizer considerably exceeded the export of N with the harvested plant material in both CO2 treatments leading to an apparent net input of N into the ecosystem. Accordingly, the proportion of harvested N derived from 15N labelled fertilizer N, applied throughout the experiment (< 6 years), increased over the years. Under these high N conditions, the annual DM yield response of the Lolium perenne sward to elevated pCO2 increased (from 7% in 1993 to 25% in 1998). In parallel, the response of N yield to elevated pCO2 increased, and the initially negative effect of elevated pCO2 on specific leaf area (SLA) disappeared. The high N input system seemed to overcome in part an initially limiting effect of N on the yield response to elevated pCO2 within a few years. In contrast, there was no apparent net input of N into the ecosystem in the low N treatment, because N fertilization just compensated the export of N with the harvested plant material. Accordingly, the proportion of harvested N yield, derived from fertilizer N, which was applied throughout the experiment, remained low. At low N, the availability of mineral N strongly limited plant growth and yield production in both CO2 treatments; the low yields of DM and N, the low concentration of N in the plant material, and the low SLA reflected this. Although the plants grew under the same environmental conditions and the same management treatment as plants in the high N treatment, the response of DM yields to elevated pCO2 in the low N treatment remained weak throughout the experiment (5% in 1993 and 9% in 1998). The results are discussed in the context of the sizes of the different N pools in the soil, the allocation of N within the plant and the possible effects on temporal immobilization, and the availability of mineral N for yield production as affected by elevated pCO2 and N fertilization.