572 research outputs found
Design of pixel-level ADCs for energy-sensitive hybrid pixel detectors
Single-photon counting hybrid pixel detectors have shown\ud
to be a valid alternative to other types of X-ray imaging\ud
devices due to their high sensitivity, low noise, linear behavior\ud
and wide dynamic range. One important advantage of these\ud
devices is the fact that detector and readout electronics are\ud
manufactured separately. This allows the use of industrial\ud
state-of-the-art CMOS processes to make the readout\ud
electronics, combined with a free choice of detector material\ud
(high resistivity Silicon, GaAs or other). By measuring not\ud
only the number of X-ray photons but also their energies (or\ud
wavelengths), the information content of the image increases,\ud
given the same X-ray dose. We have studied several\ud
possibilities of adding energy sensitivity to the single photon\ud
counting capability of hybrid pixel detectors, by means of\ud
pixel-level analog-to-digital converters. We show the results of\ud
simulating different kinds of analog-to-digital converters in\ud
terms of power, area and speed
A distinct magnetic property of the inner penumbral boundary
A sunspot emanates from a growing pore or protospot. In order to trigger the
formation of a penumbra, large inclinations at the outskirts of the protospot
are necessary. The penumbra develops and establishes by colonising both umbral
areas and granulation. Evidence for a unique stable boundary value for the
vertical component of the magnetic field strength, ,
was found along the umbra-penumbra boundary of developed sunspots. We use
broadband G-band images and spectropolarimetric GFPI/VTT data to study the
evolution of and the vertical component of the magnetic field on a forming
umbra-penumbra boundary. For comparison with stable sunspots, we also analyse
the two maps observed by Hinode/SP on the same spot after the penumbra formed.
The vertical component of the magnetic field, , at the
umbra-penumbra boundary increases during penumbra formation owing to the
incursion of the penumbra into umbral areas. After 2.5 hours, the penumbra
reaches a stable state as shown by the GFPI data. At this stable stage, the
simultaneous Hinode/SP observations show a value comparable to
that of umbra-penumbra boundaries of fully fledged sunspots. We confirm that
the umbra-penumbra boundary, traditionally defined by an intensity threshold,
is also characterised by a distinct canonical magnetic property, namely by
. During the penumbra formation process, the inner
penumbra extends into regions where the umbra previously prevailed. Hence, in
areas where , the magneto-convection
mode operating in the umbra turns into a penumbral mode. Eventually, the inner
penumbra boundary settles at , which hints toward the
role of as inhibitor of the penumbral mode of
magneto-convection.Comment: Accepted as a Letter to A&A. Reproduced with permission from
Astronomy & Astrophysics, \copyright ES
A distinct magnetic property of the inner penumbral boundary III. Analysis of simulated sunspots
The analyses of sunspot observations revealed a fundamental magnetic property
of the umbral boundary, the invariance of the vertical component of the
magnetic field. We aim to analyse the magnetic properties of the umbra-penumbra
boundary in simulated sunspots and thus assess their similarity to observed
sunspots. Also, we aim to investigate the role of plasma and the ratio
of kinetic to magnetic energy in simulated sunspots on the convective motions.
We use a set of non-grey simulation runs of sunspots with the MURaM code. These
data are used to synthesise the Stokes profiles that are then degraded to the
Hinode spectropolarimeter-like observations. Then, the data are treated like
real Hinode observations of a sunspot and magnetic properties at the umbral
boundaries are determined. Simulations with potential field extrapolation
produce a realistic magnetic field configuration on their umbral boundaries.
Two simulations with potential field upper boundary, but different subsurface
magnetic field structures, differ significantly in the extent of their
penumbrae. Increasing the penumbra width by forcing more horizontal magnetic
fields at the upper boundary results in magnetic properties that are not
consistent with observations. This implies that the size of the penumbra is
given by the subsurface structure of the magnetic field. None of the sunspot
simulations is consistent with observed properties of the magnetic field and
direction of the Evershed flow at the same time. Strong outward directed
Evershed flows are only found in setups with artificially enhanced horizontal
component of the magnetic field at the top boundary that are not consistent
with the observed magnetic field properties at the UP boundary. We want to
stress out that the `photospheric' boundary of simulated sunspots is defined by
a magnetic field strength of equipartition field value
The magnetic nature of umbra-penumbra boundary in sunspots
Sunspots are the longest-known manifestation of solar activity, and their
magnetic nature has been known for more than a century. Despite this, the
boundary between umbrae and penumbrae, the two fundamental sunspot regions, has
hitherto been solely defined by an intensity threshold. Here, we aim at
studying the magnetic nature of umbra-penumbra boundaries in sunspots of
different sizes, morphologies, evolutionary stages, and phases of the solar
cycle. We used a sample of 88 scans of the Hinode/SOT spectropolarimeter to
infer the magnetic field properties in at the umbral boundaries. We defined
these umbra-penumbra boundaries by an intensity threshold and performed a
statistical analysis of the magnetic field properties on these boundaries. We
statistically prove that the umbra-penumbra boundary in stable sunspots is
characterised by an invariant value of the vertical magnetic field component:
the vertical component of the magnetic field strength does not depend on the
umbra size, its morphology, and phase of the solar cycle. With the statistical
Bayesian inference, we find that the strength of the vertical magnetic field
component is, with a likelihood of 99\%, in the range of 1849-1885 G with the
most probable value of 1867 G. In contrast, the magnetic field strength and
inclination averaged along individual boundaries are found to be dependent on
the umbral size: the larger the umbra, the stronger and more horizontal the
magnetic field at its boundary. The umbra and penumbra of sunspots are
separated by a boundary that has hitherto been defined by an intensity
threshold. We now unveil the empirical law of the magnetic nature of the
umbra-penumbra boundary in stable sunspots: it is an invariant vertical
component of the magnetic field.Comment: accepted as A&A lette
A new invasive weed-feeding species of Polypedilum (Pentapedilum) Kieffer from South Africa (Diptera: Chironomidae, Chironominae)
Polypedilum (Pentapedilum) tuburcinatum Andersen et Bello González sp. n. is described and figured as male, female, pupa and larva based on material collected in the Eastern Cape Province in South Africa, imported into quarantine in Ireland and reared in the laboratory. The species feeds on the aquatic weed Lagarosiphon major (Ridl.) Moss ex Wager and is regarded as a promising candidate agent for biological control of this invasive weedpublishedVersio
Adaptive fractionation at the MR-linac
Objective. Fractionated radiotherapy typically delivers the same dose in each fraction. Adaptive fractionation (AF) is an approach to exploit inter-fraction motion by increasing the dose on days when the distance of tumor and dose-limiting organs at risk (OAR) is large and decreasing the dose on unfavorable days. We develop an AF algorithm and evaluate the concept for patients with abdominal tumors previously treated at the MR-linac in 5 fractions.Approach. Given daily adapted treatment plans, inter-fractional changes are quantified by sparing factorsδdefined as the OAR-to-tumor dose ratio. The key problem of AF is to decide on the dose to deliver in fractiont, givenδand the dose delivered in previous fractions, but not knowing futureδs. Optimal doses that maximize the expected biologically effective dose in the tumor (BED) while staying below a maximum OAR BEDconstraint are computed using dynamic programming, assuming a normal distribution overδwith mean and variance estimated from previously observed patient-specificδs. The algorithm is evaluated for 16 MR-linac patients in whom tumor dose was compromised due to proximity of bowel, stomach, or duodenum.Main Results. In 14 out of the 16 patients, AF increased the tumor BEDcompared to the reference treatment that delivers the same OAR dose in each fraction. However, in 11 of these 14 patients, the increase in BEDwas below 1 Gy. Two patients with large sparing factor variation had a benefit of more than 10 Gy BEDincrease. For one patient, AF led to a 5 Gy BEDdecrease due to an unfavorable order of sparing factors.Significance. On average, AF provided only a small increase in tumor BED. However, AF may yield substantial benefits for individual patients with large variations in the geometry
Specialized odorant receptors in social insects that detect cuticular hydrocarbon cues and candidate pheromones.
Eusocial insects use cuticular hydrocarbons as components of pheromones that mediate social behaviours, such as caste and nestmate recognition, and regulation of reproduction. In ants such as Harpegnathos saltator, the queen produces a pheromone which suppresses the development of workers' ovaries and if she is removed, workers can transition to a reproductive state known as gamergate. Here we functionally characterize a subfamily of odorant receptors (Ors) with a nine-exon gene structure that have undergone a massive expansion in ants and other eusocial insects. We deorphanize 22 representative members and find they can detect cuticular hydrocarbons from different ant castes, with one (HsOr263) that responds strongly to gamergate extract and a candidate queen pheromone component. After systematic testing with a diverse panel of hydrocarbons, we find that most Harpegnathos saltator Ors are narrowly tuned, suggesting that several receptors must contribute to detection and discrimination of different cuticular hydrocarbons important in mediating eusocial behaviour.Cuticular hydrocarbons (CHC) mediate the interactions between individuals in eusocial insects, but the sensory receptors for CHCs are unclear. Here the authors show that in ants such as H. saltator, the 9-exon subfamily of odorant receptors (HsOrs) responds to CHCs, and ectopic expression of HsOrs in Drosophila neurons imparts responsiveness to CHCs
Capra alba Moyà -Solà , 1987 del Pleistoceno Inferior de la Sierra de Quibas (Albanilla, Murcia, España)
A finales de la década de los 90 se realizó el primer estudio paleontológico del yacimiento de la Sierra
de Quibas (Montoya et al., 1999) en el que se describieron más de 60 taxones de vertebrados. Uno
de ellos fue el de un caprino asignado como Capra sp. aff Capra alba.
Las últimas campañas de excavación han librado nuevos restos de este taxón, lo que ha permitido
poder estudiarlo con mayor profundidad y asignarlo a Capra alba. Esta atribuciĂłn se basa en la comparaciĂłn
morfológica y métrica de los cráneos, núcleos óseos, dentición y metápodos con los ejemplares
de C. alba de Venta Micena (Orce, Granada).The first palaeontological study of the locality of Quibas dates from the end of the 1990ties (Montoya
et al., 1999), describing over 60 vertebrate taxa. One of these was a caprine assigned to Capra sp. aff.
Capra alba.
Recent excavations yielded new remains of this taxon, which permits a more profound study of its
affinities and an assignation to Capra alba, without reservation. This assignation is based on the morphological
and metrical comparison of the skulls, horn cores, dentition and metapodials from Quibas with
those of Capra alba from Venta Micena (Orce Granada)[email protected]
Evaluation of an operational real-time irrigation scheduling scheme for drip irrigated citrus fields in Picassent, Spain
[EN] Irrigated agriculture is very important for securing food production for an increasing population over the next decades. Given scarcity of water resources, optimal irrigation management is needed to reduce water while realizing maximal crop productivity. The new method of integrating soil water content measurements and the Community Land Model (CLM) using sequential data assimilation (DA) is promising to improve the prediction of soil water status and efficiently design irrigation strategies. Soil water content measured by FDR (Frequency Domain Reflectometry) was assimilated into CLM by LETKF (Local Ensemble Transform Kalman Filter) to improve model predictions. Atmospheric input data from GFS (Global Forecast System) were used to force CLM in order to predict short-term soil water contents. The irrigation amount was then calculated on the basis of the difference between predicted and targeted soil water content over the root zone.
During the real-time irrigation campaigns in Picassent (Spain) in 2015 and 2016, there were 6 fields irrigated according the data assimilation-optimization approach (CLM-DA), 2 further fields according the FAO (Food and Agriculture Organization) water balance method and also 2 fields traditionally according the farmers preference. The required amount of irrigation water for each citrus field was applied by SCADA (supervisory control and data acquisition system). Compared with the traditionally irrigated fields by farmers, 24% less irrigation water was needed for the CLM-DA scheduled fields averaged over both years from July to September, while the FAO fields were irrigated with 22% less water. Stem water potential data and soil moisture recordings of the CLM-DA scheduled fields did not indicate significant water stress during the irrigation period. The CLM-DA scheduled fields received less irrigation water than traditionally irrigated fields, but the orange production was not significantly suppressed.
Overall, our results show that the CLM-DA method is attractive given its water saving potential and automated approach, ease of incorporation of on-line measurements and ensemble based predictions of soil moisture evolution.The first author of this paper was funded by a stipend from the Government of China (CSC scholarship). The support of the super computing facilities of Forschungszentrum Juelich (JURECA) is gratefully acknowledged. We are also thankful to our colleagues in IVIA and Universitat Politecnica de Valencia for the installation of soil moisture sensors and conducting stem water potential measurements.Li, D.; Hendricks, H.; Han, X.; JimĂ©nez Bello, MA.; MartĂnez Alzamora, F.; Vereeken, H. (2018). Evaluation of an operational real-time irrigation scheduling scheme for drip irrigated citrus fields in Picassent, Spain. Agricultural Water Management. 208:465-477. https://doi.org/10.1016/j.agwat.2018.06.022S46547720
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