2,732 research outputs found
Characteristics and performance of the ESTEC large space simulator cryogenic system
The final concept and performance characteristics of the Large Space Simulator (LSS) at ESTEC, The Netherlands are discussed. The LSS cryogenics system has proven its operational capabilities under simulated heat load conditions and provides sufficient margin for future elevated requirements. The acceptance test proved that nominal operating pressures can be lower than the design parameters, providing increased system safety and reliability. The ease of access for repair and the incorporated redundancy will limit system downtime. Finally, the system design resulted in a low consumption of LN sub 2, which is an important factor in keeping the operational costs at a low level
On the nature of the barlens component in barred galaxies: what do boxy/peanut bulges look like when viewed face-on?
Barred galaxies have interesting morphological features whose presence and
properties set constraints on galactic evolution. Here we examine barlenses,
i.e. lens-like components whose extent along the bar major axis is shorter than
that of the bar and whose outline is oval or circular. We identify and analyse
barlenses in -body plus SPH simulations, compare them extensively with those
from the NIRS0S (Near-IR S0 galaxy survey) and the SG samples (Spitzer
Survey of Stellar Structure in Galaxies) and find very good agreement. We
observe barlenses in our simulations from different viewing angles. This
reveals that barlenses are the vertically thick part of the bar seen face-on,
i.e. a barlens seen edge-on is a boxy/peanut/X bulge. In morphological studies,
and in the absence of kinematics or photometry, a barlens, or part of it, may
be mistaken for a classical bulge. Thus the true importance of classical
bulges, both in numbers and mass, is smaller than currently assumed, which has
implications for galaxy formation studies. Finally, using the shape of the
isodensity curves, we propose a rule of thumb for measuring the barlens extent
along the bar major axis of moderately inclined galaxies, thus providing an
estimate of which part of the bar is thicker.Comment: 21 pages, 11 figures, revised version as published in MNRA
[Review of: N.S. Eidsheim (2019) The Race of Sound : Listening, Timbre and Vocality in African American Music]
Foreword
On invitation, I wrote a new foreword to the reissue of eContact! 1.1 Women in Electroacoustic, inaugural issue of eContact! published by the Canadian Electroacoustic Community (CEC) in 1998
The -Class Tower of
The seminal papers in the field of root-discriminant bounds are those of
Odlyzko and Martinet. Both papers include the question of whether the field
has finite or infinite -class tower. This is a
critical case that will either substantially lower the best known upper bound
for lim inf of root-discriminants (if infinite) or else give a counter-example
to what is often termed Martinet's conjecture or question (if finite). Using
extensive computation and introducing some new techniques, we give strong
evidence that the tower is in fact finite, establishing other properties of its
Galois group en route
Statistics of the structure components in S0s: implications for bar induced secular evolution
The fractions and dimension of bars, rings and lenses are studied in the
Near-IR S0 galaxy Survey (NIRS0S). We find evidence that multiple lenses in
some barred S0s are related to bar resonances in a similar manner as the inner
and outer rings, for which the outer/inner length ratio 2. Inner lenses in the
non-barred galaxies normalized to galaxy diameter are clearly smaller than
those in the barred systems. Interestingly, these small lenses in the
non-barred galaxies have similar sizes as barlenses (lens-like structures
embedded in a bar), and therefore might actually be barlenses in former barred
galaxies, in which the outer, more elongated bar component, has been destroyed.
We also find that fully developed inner lenses are on average a factor 1.3
larger than bars, whereas inner rings have similar sizes as bars. The fraction
of inner lenses is found to be constant in all family classes (A, AB, B).
Nuclear bars appear most frequently among the weakly barred (AB) galaxies,
which is consistent with the theoretical models by Maciejewski & Athanassoula
(2008). Similar sized bars as the nuclear bars were detected in seven
'non-barred' S0s. Galaxy luminosity does not uniquely define the sizes of bars
or bar-related structures, neither is there any upper limit in galaxy
luminosity for bar formation. Although all the family classes cover the same
range of galaxy luminosity, the non-barred (A) galaxies are on average 0.6 mag
brighter than the strongly barred (B) systems. Overall, our results are
consistent with the idea that bars play an important role in the formation of
the structure components of galaxies. The fact that multiple lenses are common
in S0s, and that at least the inner lenses can have very old stellar
populations, implies that the last destructive merger, or major gas accretion
event, must have taken place at a fairly high redshift.Comment: 36 pages (include 13 figures, 11 tables). Accepted to MNRAS 2013 Jan
2
Circuit-Model Analysis for Spintronic Devices with Chiral Molecules as Spin Injectors
Recent research discovered that charge transfer processes in chiral molecules
can be spin selective and named the effect chiral-induced spin selectivity
(CISS). Follow-up work studied hybrid spintronic devices with conventional
electronic materials and chiral (bio)molecules. However, a theoretical
foundation for the CISS effect is still in development and the spintronic
signals were not evaluated quantitatively. We present a circuit-model approach
that can provide quantitative evaluations. Our analysis assumes the scheme of a
recent experiment that used photosystem~I (PSI) as spin injectors, for which we
find that the experimentally observed signals are, under any reasonable
assumptions on relevant PSI time scales, too high to be fully due to the CISS
effect. We also show that the CISS effect can in principle be detected using
the same type of solid-state device, and by replacing silver with graphene, the
signals due to spin generation can be enlarged four orders of magnitude. Our
approach thus provides a generic framework for analyzing this type of
experiments and advancing the understanding of the CISS effect
MONITORING THE IMPACT ON POND PRODUCTIVITY FROM LEARNING AT THE COASTAL FIELD SCHOOL 2016-2019
The monitoring of aquaculture farmers by the UNDIP/WUR-team aims to
assess the progress towards reaching the goals set by the project Building with Nature
– Demak. As planned in this first year the sample was taken in one village:
Tambakbulusan. As farmers implemented the learning from the Coastal Field Schools
during the same season as the training was given, no baseline for this sample was
measured. In the village six ponds were monitored during one cropping season; we
report on five ponds as one of the ponds was the demonstration pond on which Blue
Forest will report.
Before stocking the ponds were dried for at least 5 days and composted goat
manure was mixed to the sediment. Thereafter an good dosage of home-made organic
fertilizer was added to improve water quality; during the culture period a smaller dose
was added weekly to maintain the plankton growth in the pond. The farmers prepared
the organic fertilizer (compost), called MOL, from fermented rotten fruits, vegetables
and household waste. One farmer used an industrial compost and another fed
manufactured pellets; thus the five farmers implemented partly the promoted LEISA
technology.
Several of the cropping cycles couldn’t be completed due to heavy rains or
flooding. The ponds were restocked. Some ponds were harvested early to avoid risk of
mortality due to increase of salinity of shrimp showing disease symptoms. Other water
quality parameters were within the limits for recommended limits for shrimp culture.
For one production cycle only from five ponds in one village, the shrimp
produced per ha was three times higher for the three LEISA farmers and for the other
two 20 times higher than the average found in the Demak baseline for one full year,
The average gross margin (income) was IDR 46 million/cycle, i.e. 4.5 times higher, but
for the three LEISA farmers this was IDR 14 million/cycle, i.e. 40% higher than the
average found in the Demak baseline for one full year. From the limited sample we
conclude preliminary that the technology trained by the CFS allows to reach the goals
set by BwN regarding pond productivity and income from aquaculture
Secants of Lagrangian Grassmannians
We study the dimensions of secant varieties of the Grassmannian of Lagrangian
subspaces in a symplectic vector space. We calculate these dimensions for third
and fourth secant varieties. Our result is obtained by providing a normal form
for four general points on such a Grassmannian and by explicitly calculating
the tangent spaces at these four points
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