328 research outputs found
Sexual dimorphism in the Drosophila melanogaster (Diptera: Drosophilidae) metabolome increases throughout development
The expression of sexually dimorphic phenotypes from a shared genome between males and females is a longstanding puzzle in evolutionary biology. Increasingly, research has made use of transcriptomic technology to examine the molecular basis of sexual dimorphism through gene expression studies, but even this level of detail misses the metabolic processes that ultimately link gene expression with the whole organism phenotype. We use metabolic profiling in Drosophila melanogaster to complete this missing step, with a view to examining variation in male and female metabolic profiles, or metabolomes, throughout development. We show that the metabolome varies considerably throughout larval, pupal and adult stages. We also find significant sexual dimorphism in the metabolome, although only in pupae and adults, and the extent of dimorphism increases throughout development. We compare this to transcriptomic data from the same population and find that the general pattern of increasing sex differences throughout development is mirrored in RNA expression. We discuss our results in terms of the usefulness of metabolic profiling in linking genotype and phenotype to more fully understand the basis of sexually dimorphic phenotypes
Detecting differential gene expression in blastocysts following pronuclear transfer.
Nuclear transfer techniques (a.k.a. mitochondrial replacement therapies) are currently under development to provide a route to eliminating particular instances of mitochondrial disease from the germline. Before these kinds of techniques are implemented clinically it is of primary concern that their safety and efficacy is established. In a recent paper, Hyslop et al. (Nature 534:383-386, 2016. doi: 10.1038/nature18303 ) utilized a specific version of pronuclear transfer to investigate the consequences for gene expression in the developing embryo, which may indicate whether or not developmental pathways have been perturbed. However, the study was only able to include a small number of blastocysts within each treatment group, although a larger number of single cell expression profiles from each blastocyst were acquired. Using simulated datasets we show that the size and experimental design of this study cannot provide conclusive evidence that expression profiles of manipulated or control samples are indistinguishable from one another due to low power. These simulations also illustrate why visual inspections of principle component analyses used in the study cannot replace statistical modeling of treatment effects
Utilisation of wastewater for fuel and fodder production and environmental and social benefits in semi-arid, peri-urban zones of sub-Saharan Africa. Third Annual Report: 1/12/2004 - 30/11/2005
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Ensemble prediction for nowcasting with a convection-permitting model - II: forecast error statistics
A 24-member ensemble of 1-h high-resolution forecasts over the Southern United Kingdom is used to study short-range forecast error statistics. The initial conditions are found from perturbations from an ensemble transform Kalman filter. Forecasts from this system are assumed to lie within the bounds of forecast error of an operational forecast system. Although noisy, this system is capable of producing physically reasonable statistics which are analysed and compared to statistics implied from a variational assimilation system. The variances for temperature errors for instance show structures that reflect convective activity. Some variables, notably potential temperature and specific humidity perturbations, have autocorrelation functions that deviate from 3-D isotropy at the convective-scale (horizontal scales less than 10 km). Other variables, notably the velocity potential for horizontal divergence perturbations, maintain 3-D isotropy at all scales. Geostrophic and hydrostatic balances are studied by examining correlations between terms in the divergence and vertical momentum equations respectively. Both balances are found to decay as the horizontal scale decreases. It is estimated that geostrophic balance becomes less important at scales smaller than 75 km, and hydrostatic balance becomes less important at scales smaller than 35 km, although more work is required to validate these findings. The implications of these results for high-resolution data assimilation are discussed
Streamer Wave Events Observed in Solar Cycle 23
In this paper we conduct a data survey searching for well-defined streamer
wave events observed by the Large Angle and Spectrometric Coronagraph (LASCO)
on-board the Solar and Heliospheric Observatory (SOHO) throughout Solar Cycle
23. As a result, 8 candidate events are found and presented here. We compare
different events and find that in most of them the driving CMEs ejecta are
characterized by a high speed and a wide angular span, and the CME-streamer
interactions occur generally along the flank of the streamer structure at an
altitude no higher than the bottom of the field of view of LASCO C2. In
addition, all front-side CMEs have accompanying flares. These common
observational features shed light on the excitation conditions of streamer wave
events.
We also conduct a further analysis on one specific streamer wave event on 5
June 2003. The heliocentric distances of 4 wave troughs/crests at various
exposure times are determined; they are then used to deduce the wave properties
like period, wavelength, and phase speeds. It is found that both the period and
wavelength increase gradually with the wave propagation along the streamer
plasma sheet, and the phase speed of the preceding wave is generally faster
than that of the trailing ones. The associated coronal seismological study
yields the radial profiles of the Alfv\'en speed and magnetic field strength in
the region surrounding the streamer plasma sheet. Both quantities show a
general declining trend with time. This is interpreted as an observational
manifestation of the recovering process of the CME-disturbed corona. It is also
found that the Alfv\'enic critical point is at about 10 R where the
flow speed, which equals the Alfv\'en speed, is 200 km s
Asclepius or Hippocrates? Differing interpretations of post‐compulsory initial teacher training mentoring
Towards a global land surface climate fiducial reference measurements network
There is overwhelming evidence that the climate system has warmed since the instigation of instrumental meteorological observations. The Fifth Assessment Report of the Intergovernmental Panel on Climate Change concluded that the evidence for warming was unequivocal. However, owing to imperfect measurements and ubiquitous changes in measurement networks and techniques, there remain uncertainties in many of the details of these historical changes. These uncertainties do not call into question the trend or overall magnitude of the changes in the global climate system. Rather, they act to make the picture less clear than it could be, particularly at the local scale where many decisions regarding adaptation choices will be required, both now and in the future. A set of high-quality long-term fiducial reference measurements of essential climate variables will enable future generations to make rigorous assessments of future climate change and variability, providing society with the best possible information to support future decisions. Here we propose that by implementing and maintaining a suitably stable and metrologically well-characterized global land surface climate fiducial reference measurements network, the present-day scientific community can bequeath to future generations a better set of observations. This will aid future adaptation decisions and help us to monitor and quantify the effectiveness of internationally agreed mitigation steps. This article provides the background, rationale, metrological principles, and practical considerations regarding what would be involved in such a network, and outlines the benefits which may accrue. The challenge, of course, is how to convert such a vision to a long-term sustainable capability providing the necessary well-characterized measurement series to the benefit of global science and future generations
Using reference radiosondes to characterise NWP model uncertainty for improved satellite calibration and validation
The characterisation of errors and uncertainties in numerical
weather prediction (NWP) model fields is a major challenge that is addressed
as part of the Horizon 2020 Gap Analysis for Integrated Atmospheric ECV
CLImate Monitoring (GAIA-CLIM) project. In that regard, observations from the
GCOS (Global Climate Observing System) Reference Upper-Air Network (GRUAN)
radiosondes are being used at the Met Office and European Centre for
Medium-Range Weather Forecasts (ECMWF) to assess errors and uncertainties
associated with model data.
The software introduced in this study and referred to as the GRUAN processor
has been developed to collocate GRUAN radiosonde profiles and NWP model
fields, simulate top-of-atmosphere brightness temperature at frequencies
used by space-borne instruments, and propagate GRUAN uncertainties in that
simulation. A mathematical framework used to estimate and assess the
uncertainty budget of the comparison of simulated brightness temperature is
also proposed.
A total of 1 year of GRUAN radiosondes and matching NWP fields from the Met Office and
ECMWF have been processed and analysed for the purposes of demonstration of
capability. We present preliminary results confirming the presence of known
biases in the temperature and humidity profiles of both NWP centres. The
night-time difference between GRUAN and Met Office (ECMWF) simulated
brightness temperature at microwave frequencies predominantly sensitive to
temperature is on average smaller than 0.1 K (0.4 K). Similarly, this
difference is on average smaller than 0.5 K (0.4 K) at microwave
frequencies predominantly sensitive to humidity.
The uncertainty estimated for the Met Office–GRUAN difference ranges from
0.08 to 0.13 K for temperature-sensitive frequencies and from 1.6 to 2.5 K
for humidity-sensitive frequencies. From the analysed sampling, 90 % of
the comparisons are found to be in statistical agreement.
This initial study has the potential to be extended to a larger collection
of GRUAN profiles, covering multiple sites and years, with the aim of
providing a robust estimation of both errors and uncertainties of NWP model
fields in radiance space for a selection of key microwave and infrared
frequencies.</p
IRAS 20050+2720: Anatomy of a young stellar cluster
IRAS 20050+2720 is young star forming region at a distance of 700 pc without
apparent high mass stars. We present results of our multiwavelength study of
IRAS 20050+2720 which includes observations by Chandra and Spitzer, and 2MASS
and UBVRI photometry. In total, about 300 YSOs in different evolutionary stages
are found. We characterize the distribution of young stellar objects (YSOs) in
this region using a minimum spanning tree (MST) analysis. We newly identify a
second cluster core, which consists mostly of class II objects, about 10 arcmin
from the center of the cloud. YSOs of earlier evolutionary stages are more
clustered than more evolved objects. The X-ray luminosity function (XLF) of
IRAS 20050+2720 is roughly lognormal, but steeper than the XLF of the more
massive Orion nebula complex. IRAS 20050+2720 shows a lower N_H/A_K ratio
compared with the diffuse ISM.Comment: 15 pages, 12 figures, accepted by A
Status of the CRESST Dark Matter Search
The CRESST experiment aims for a detection of dark matter in the form of
WIMPs. These particles are expected to scatter elastically off the nuclei of a
target material, thereby depositing energy on the recoiling nucleus. CRESST
uses scintillating CaWO4 crystals as such a target. The energy deposited by an
interacting particle is primarily converted to phonons which are detected by
transition edge sensors. In addition, a small fraction of the interaction
energy is emitted from the crystals in the form of scintillation light which is
measured in coincidence with the phonon signal by a separate cryogenic light
detector for each target crystal. The ratio of light to phonon energy permits
the discrimination between the nuclear recoils expected from WIMPs and events
from radioactive backgrounds which primarily lead to electron recoils. CRESST
has shown the success of this method in a commissioning run in 2007 and, since
then, further investigated possibilities for an even better suppression of
backgrounds. Here, we report on a new class of background events observed in
the course of this work. The consequences of this observation are discussed and
we present the current status of the experiment.Comment: Proceedings of the 13th International Workshop on Low Temperature
Detectors, 4 pages, 3 figure
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