2,346 research outputs found
PACS photometer calibration block analysis
The absolute stability of the PACS bolometer response over the entire mission
lifetime without applying any corrections is about 0.5% (standard deviation) or
about 8% peak-to-peak. This fantastic stability allows us to calibrate all
scientific measurements by a fixed and time-independent response file, without
using any information from the PACS internal calibration sources. However, the
analysis of calibration block observations revealed clear correlations of the
internal source signals with the evaporator temperature and a signal drift
during the first half hour after the cooler recycling. These effects are small,
but can be seen in repeated measurements of standard stars. From our analysis
we established corrections for both effects which push the stability of the
PACS bolometer response to about 0.2% (stdev) or 2% in the blue, 3% in the
green and 5% in the red channel (peak-to-peak). After both corrections we still
see a correlation of the signals with PACS FPU temperatures, possibly caused by
parasitic heat influences via the Kevlar wires which connect the bolometers
with the PACS Focal Plane Unit. No aging effect or degradation of the
photometric system during the mission lifetime has been found.Comment: 15 pages, accepted for publication in Experimental Astronom
Studies on the maize cold tolerance tests in the Martonvásár phytotron
The climatic conditions in Hungary and in the countries to which seed is exported
makes the study of maize cold tolerance and constant improvements in the cold tolerance
of Martonvásár hybrids especially important. An improvement in the early spring cold
tolerance of maize would allow it to be grown in more northern areas with a cooler
climate, while on traditional maize-growing areas the profitability of maize production
could be improved by earlier sowing, leading to a reduction in transportation and drying
costs and in diseases caused by Fusarium sp. The recognition of this fact led Martonvásár
researchers to start investigating this subject nearly four decades ago. The phytotron has
proved an excellent tool for studying and improving the cold tolerance of maize. The
review will give a brief summary of the results achieved in the field of maize cold
tolerance in the Martonvásár institute in recent decades
Locating mesolithic hunter-gatherer camps in the Carpathian Basin
The Mesolithic in Eastern Europe was the last time that hunter-gatherer economies thrived there before the spread of agriculture in the second half of the seventh millennium BC. But the period, and the interactions between foragers and the first farmers, are poorly understood in the Carpathian Basin and surrounding areas because few sites are known, and even fewer have been excavated and published. How did site location differ between Mesolithic and Early Neolithic settlers? And where should we look for rare Mesolithic sites? Proximity analysis is seldom used for predictive modeling for hunter-gatherer sites at large scales, but in this paper, we argue that it can serve as an important starting point for prospection for rare and poorly understood sites. This study uses proximity analysis to provide quantitative landscape associations of known Mesolithic and Early Neolithic sites in the Carpathian Basin to show how Mesolithic people chose attributes of the landscape for camps, and how they differed from the farmers who later settled. We use elevation and slope, rivers, wetlands prior to the twentieth century, and the distribution of lithic raw materials foragers and farmers used for toolmaking to identify key proxies for preferred locations. We then build predictive models for the Mesolithic and Early Neolithic in the Pannonian region to highlight parts of the landscape that have relatively higher probabilities of having Mesolithic sites still undiscovered and contrast them with the settlement patterns of the first farmers in the area. We find that large parts of Pannonia conform to landforms preferred by Mesolithic foragers, but these areas have not been subject to investigation
The Polyamine Binding Site in Inward Rectifier K+ Channels
Strongly inwardly rectifying potassium channels exhibit potent and steeply voltage-dependent block by intracellular polyamines. To locate the polyamine binding site, we have examined the effects of polyamine blockade on the rate of MTSEA modification of cysteine residues strategically substituted in the pore of a strongly rectifying Kir channel (Kir6.2[N160D]). Spermine only protected cysteines substituted at a deep location in the pore, between the “rectification controller” residue (N160D in Kir6.2, D172 in Kir2.1) and the selectivity filter, against MTSEA modification. In contrast, blockade with a longer synthetic polyamine (CGC-11179) also protected cysteines substituted at sites closer to the cytoplasmic entrance of the channel. Modification of a cysteine at the entrance to the inner cavity (169C) was unaffected by either spermine or CGC-11179, and spermine was clearly “locked” into the inner cavity (i.e., exhibited a dramatically slower exit rate) following modification of this residue. These data provide physical constraints on the spermine binding site, demonstrating that spermine stably binds at a deep site beyond the “rectification controller” residue, near the extracellular entrance to the channel
The Polyamine Binding Site in Inward Rectifier K+ Channels
Strongly inwardly rectifying potassium channels exhibit potent and steeply voltage-dependent block by intracellular polyamines. To locate the polyamine binding site, we have examined the effects of polyamine blockade on the rate of MTSEA modification of cysteine residues strategically substituted in the pore of a strongly rectifying Kir channel (Kir6.2[N160D]). Spermine only protected cysteines substituted at a deep location in the pore, between the “rectification controller” residue (N160D in Kir6.2, D172 in Kir2.1) and the selectivity filter, against MTSEA modification. In contrast, blockade with a longer synthetic polyamine (CGC-11179) also protected cysteines substituted at sites closer to the cytoplasmic entrance of the channel. Modification of a cysteine at the entrance to the inner cavity (169C) was unaffected by either spermine or CGC-11179, and spermine was clearly “locked” into the inner cavity (i.e., exhibited a dramatically slower exit rate) following modification of this residue. These data provide physical constraints on the spermine binding site, demonstrating that spermine stably binds at a deep site beyond the “rectification controller” residue, near the extracellular entrance to the channel
Multiple conducting carriers generated in LaAlO3/SrTiO3 heterostructures
We have found that there is more than one type of conducting carriers
generated in LaAlO3/SrTiO3 heterostructures by comparing the sheet carrier
density and mobility from optical transmission spectroscopy with those from
dc-transport measurements. When multiple types of carriers exist, optical
characterization dominantly reflects the contribution from the high-density
carriers whereas dc-transport measurements may exaggerate the contribution of
the high-mobility carriers even though they are present at low-density. Since
the low-temperature mobilities determined by dc-transport in the LaAlO3/SrTiO3
heterostructures are much higher than those extracted by optical method, we
attribute the origin of high-mobility transport to the low-density conducting
carriers.Comment: 3 figures, supplemental materia
Comet C/2013 A1 (Siding Spring) as seen with the Herschel Space Observatory
The thermal emission of comet C/2013 A1 (Siding Spring) was observed on March
31, 2013, at a heliocentric distance of 6.48 au using the PACS photometer
camera of the Herschel Space Observatory. The comet was clearly active, showing
a coma that could be traced to a distance of 10", i.e. 50000 km. Analysis of
the radial intensity profiles of the coma provided dust mass and dust
production rate; the derived grain size distribution characteristics indicate
an overabundance of large grains in the thermal emission. We estimate that
activity started about 6 months before these observations, at a heliocentric
distance of 8 au.Comment: 4 pages, 3 figures + a one-page Appendix with 2 figures, accepted for
publication in Astronomy & Astrophysics (Letter
Variation in education doctoral students’ conceptions of university teaching
The development of doctoral students as university teachers has received substantially less attention compared with their development as researchers, with a similar deficit extending to research on how they experience and understand university teaching. This article reports the results of a phenomenographic study of education doctoral students’ conceptions of teaching in higher education. Using samples from two education departments in England and Sweden, we conducted interviews to identify variation in doctoral students’ experiences of university teaching. Analysis of the transcripts produced six qualitatively different conceptions of teaching: doctoral students conceptualised university teaching as a means of (A) transmitting knowledge, (B) presenting contrasting concepts of education, (C) communicating and engaging with students, (D) enabling students to apply knowledge and skills, (E) enabling students to interpret and compare concepts of education, and (F) promoting personal, professional and societal development and change. While in broad agreement with previous studies on university teachers’ conceptions of teaching, the study offers a unique insight into how the subject of education is understood by doctoral students who teach. The findings also underline the need to introduce common frameworks of academic development for academics and doctoral students alike that prioritise ways of representing and engaging with the structure of the subject, rather than the acquisition of teaching skills
Herschel-PACS photometry of Uranus' five major moons
Aims. We aim to determine far-infrared fluxes at 70, 100, and 160m of
the five major Uranus satellites Titania, Oberon, Umbriel, Ariel and Miranda,
based on observations with the photometer PACS-P aboard the Herschel Space
Observatory.
Methods. The bright image of Uranus is subtracted using a scaled Uranus point
spread function (PSF) reference established from all maps of each wavelength in
an iterative process removing the superimposed moons. Photometry of the
satellites is performed by PSF photometry. Thermophysical models of the icy
moons are fitted to the photometry of each measurement epoch and auxilliary
data at shorter wavelengths.
Results. The best fitting thermophysical models provide constraints for
important thermal properties of the moons like surface roughness and thermal
inertia. We present the first thermal infrared radiometry longward of 50m
of the four largest Uranian moons, Titania, Oberon, Umbriel and Ariel, at
epochs with equator-on illumination. Due to this inclination geometry there was
heat transport to the night side so that thermal inertia played a role,
allowing us to constrain that parameter. Also some indication for differences
in the thermal properties of leading and trailing hemispheres is found. We
specify precisely the systematic error of the Uranus flux by its moons, when
using Uranus as a far-infrared prime flux calibrator.
Conclusions. We have successfully demonstrated an image processing technique
for PACS photometer data allowing to remove a bright central source. We have
established improved thermophysical models of the five major Uranus satellites.
Derived thermal inertia values resemble more those of TNO dwarf planets Pluto
and Haumea than those of smaller TNOs and Centaurs.Comment: 25 pages, 10 figures, 7 tables, plus appendices. Accepted for
publication on A&
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