1,421 research outputs found
Satellite remote sensing can provide semi-automated monitoring to aid coastal decision-making
Coastlines are projected to face unprecedented pressures over the next century due to climate change-induced changes in sea level, storm, wave, and tidal regimes. This projection of increasing pressure is driving a reappraisal of existing shoreline management practices, with both science and policy calling for future strategies to work with the natural protection provided by coastal habitats such as salt marshes. However, we currently lack the understanding of long-term ecosystem dynamics required to incorporate these habitats into the definitive predictions of risk relied on in coastal protection planning. Satellite remote sensing has the potential to provide data that could address this knowledge gap with its frequent repeat times and global coverage facilitating the production of high temporal frequency time-series over large areas. This study sought to explore this potential in one of the largest coastal plain estuaries the in the UK, the Severn Estuary. The Random Forest machine learning algorithm was used to develop a time-series of marsh extents across the estuary from 1985 to 2020 in Google Earth Engine, with widths also extracted as a proxy for the marshes’ protective capacity. These changes were monitored in six areas that contained the most significant areas of salt marsh across the estuary. This analysis revealed a significant increasing trend in extent and widths (p 90% and a strong agreement found between the detected widths and those found in previous surveys. These findings demonstrate that satellite remote sensing combined with machine learning has the potential to provide valuable insights into changes in the extents of marshes and therefore their protective capacity. This information can be useful in the coastal planning process, allowing decision-makers to assess the sustainability of existing defences fronted by marshes, as well as allowing them to make informed decisions about the location of restoration schemes
Comparison of 99mTc-sestamibi and doxorubicin to monitor inhibition of P-glycoprotein function
P-glycoprotein (Pgp) overexpression is a well-recognized factor in resistance to chemotherapy. Doxorubicin flow cytometry is used to monitor Pgp function in haematological specimens and biopsies from other cancers, and radionuclide imaging with sestamibi has recently shown promise for non-invasive monitoring. In the present study the two methods were directly compared in single-cell suspensions of three variants of the human breast carcinoma cell line MCF7: sensitive MCF7/WT, doxorubicin-selected MCF7/AdrR, and MDR1 -gene-transfected MCF7/BC19 cells with doxorubicin resistance factors of 1, 192, and 14, respectively. Accumulation of sestamibi and mean fluorescence of doxorubicin (5.5 μM) were assessed over 60 min in the presence and absence of Pgp modulators GG918 (0.01 to 0.2 μM) and PSC833 (0.05 to 2.0 μM). Accumulation curves for sestamibi and doxorubicin differed among the cell variants under control conditions, with sestamibi showing a significantly greater difference between WT and resistant cells than doxorubicin. Both GG918 and PSC833 reversed uptake deficits to WT levels for sestamibi in MCF7/BC19 cells and doxorubicin in MCF7/BC19 and MCF7/AdrR cells, but failed to show the same effect for sestamibi in MCF7/AdrR cells (∼30% of MCF7/WT level). Thus, both methods clearly distinguished sensitive from resistant MCF7 variants, with the radionuclide method showing greater sensitivity. © 2001 Cancer Research Campaign http://www.bjcancer.co
Probing Dark Energy with Baryonic Acoustic Oscillations from Future Large Galaxy Redshift Surveys
We show that the measurement of the baryonic acoustic oscillations in large
high redshift galaxy surveys offers a precision route to the measurement of
dark energy. The cosmic microwave background provides the scale of the
oscillations as a standard ruler that can be measured in the clustering of
galaxies, thereby yielding the Hubble parameter and angular diameter distance
as a function of redshift. This, in turn, enables one to probe dark energy. We
use a Fisher matrix formalism to study the statistical errors for redshift
surveys up to z=3 and report errors on cosmography while marginalizing over a
large number of cosmological parameters including a time-dependent equation of
state. With redshifts surveys combined with cosmic microwave background
satellite data, we achieve errors of 0.037 on Omega_x, 0.10 on w(z=0.8), and
0.28 on dw(z)/dz for cosmological constant model. Models with less negative
w(z) permit tighter constraints. We test and discuss the dependence of
performance on redshift, survey conditions, and fiducial model. We find results
that are competitive with the performance of future supernovae Ia surveys. We
conclude that redshift surveys offer a promising independent route to the
measurement of dark energy.Comment: submitted to ApJ, 24 pages, LaTe
Complete Treatment of Galaxy Two-Point Statistics: Gravitational Lensing Effects and Redshift-Space Distortions
We present a coherent theoretical framework for computing gravitational
lensing effects and redshift-space distortions in an inhomogeneous universe and
investigate their impacts on galaxy two-point statistics. Adopting the
linearized FRW metric, we derive the gravitational lensing and the generalized
Sachs-Wolfe effects that include the weak lensing distortion, magnification,
and time delay effects, and the redshift-space distortion, Sachs-Wolfe, and
integrated Sachs-Wolfe effects, respectively. Based on this framework, we first
compute their effects on observed source fluctuations, separating them as two
physically distinct origins: the volume effect that involves the change of
volume and is always present in galaxy two-point statistics, and the source
effect that depends on the intrinsic properties of source populations. Then we
identify several terms that are ignored in the standard method, and we compute
the observed galaxy two-point statistics, an ensemble average of all the
combinations of the intrinsic source fluctuations and the additional
contributions from the gravitational lensing and the generalized Sachs-Wolfe
effects. This unified treatment of galaxy two-point statistics clarifies the
relation of the gravitational lensing and the generalized Sachs-Wolfe effects
to the metric perturbations and the underlying matter fluctuations. For near
future dark energy surveys, we compute additional contributions to the observed
galaxy two-point statistics and analyze their impact on the anisotropic
structure. Thorough theoretical modeling of galaxy two-point statistics would
be not only necessary to analyze precision measurements from upcoming dark
energy surveys, but also provide further discriminatory power in understanding
the underlying physical mechanisms.Comment: 20 pages, 5 figures, Fig.4 corrected, appendix added, accepted for
publication in Physical Review
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