20,467 research outputs found
On the heating of source of the Orion KL hot core
We present images of the J=10-9 rotational lines of HC3N in the vibrationally
excited levels 1v7, 1v6 and 1v5 of the hot core (HC) in Orion KL. The images
show that the spatial distribution and the size emission from the 1v7 and 1v5
levels are different. While the J=10-9 1v7 line has a size of 4''x 6'' and
peaks 1.1'' NE of the 3 mm continuum peak, the J=10--9 1v5 line emission is
unresolved (<3'') and peaks 1.3'' south of the 3 mm peak. This is a clear
indication that the HC is composed of condensations with very different
temperatures (170 K for the 1v7 peak and K for the 1v5 peak). The
temperature derived from the 1v7 and 1v5 lines increases with the projected
distance to the suspected main heating source I. Projection effects along the
line of sight could explain the temperature gradient as produced by source I.
However, the large luminosity required for source I, >5 10^5 Lsolar, to explain
the 1v5 line suggests that external heating by this source may not dominate the
heating of the HC. Simple model calculations of the vibrationally excited
emission indicate that the HC can be internally heated by a source with a
luminosity of 10^5 Lsolar, located 1.2'' SW of the 1v5 line peak (1.8'' south
of source I). We also report the first detection of high-velocity gas from
vibrationally excited HC3N emission. Based on excitation arguments we conclude
that the main heating source is also driving the molecular outflow. We
speculate that all the data presented in this letter and the IR images are
consistent with a young massive protostar embedded in an edge-on disk.Comment: 13 pages, 3 figures, To be published in Ap.J. Letter
Dispersal of larval and juvenile seabream: Implications for Mediterranean marine protected areas
In the marine context, information about dispersal is essential for the design of networks of marine protected areas (MPAs). Generally, most of the dispersal of demersal fishes is thought to be driven by the transport of eggs and larvae in currents, with the potential contribution of dispersal in later life stages relatively minimal.Using otolith chemistry analyses, we estimate dispersal patterns across a spatial scale of approximately 180. km at both propagule (i.e. eggs and larvae) and juvenile (i.e. between settlement and recruitment) stages of a Mediterranean coastal fishery species, the two-banded seabream Diplodus vulgaris. We detected three major natal sources of propagules replenishing local populations in the entire study area, suggesting that propagule dispersal distance extends to at least 90. km. For the juvenile stage, we detected dispersal of up to 165. km. Our work highlights the surprising and significant role of dispersal during the juvenile life stages as an important mechanism connecting populations. Such new insights are crucial for creating effective management strategies (e.g. MPAs and MPA networks) and to gain support from policymakers and stakeholders, highlighting that MPA benefits can extend well beyond MPA borders, and not only via dispersal of eggs and larvae, but also through movement by juveniles
The modular method: Milkfish pond culture
The modular method of milkfish culture (Chanos chanos) described in the manual is an improvement over the traditional extensive method. The manual is intended for the use of fish farmers and aquaculturists, extensionists, and students of aquaculture not only in the Philippines, but also in other milkfish-producing countries in Southeast Asia and the world. It covers the following: Interesting facts about milkfish -- biological characteristics, artificial breeding of milkfish; Design and operation of modular pond system -- pond preparation, stocking in the nursery or transition ponds, stocking in the rearing ponds, care of stock, pond utilization and production schedule, harvest and post-harvest; and, Economics and costing
Cherenkov telescope array extragalactic survey discovery potential and the impact of axion-like particles and secondary gamma rays
The Cherenkov Telescope Array (CTA) is about to enter construction phase and
one of its main key science projects is to perform an unbiased survey in search
of extragalactic sources. We make use of both the latest blazar gamma--ray
luminosity function and spectral energy distribution to derive the expected
number of detectable sources for both the planned Northern and Southern arrays
of the CTA observatory. We find that a shallow, wide survey of about 0.5 hour
per field of view would lead to the highest number of blazar detections.
Furthermore, we investigate the effect of axion-like particles and secondary
gamma rays from propagating cosmic rays on the source count distribution, since
these processes predict different spectral shape from standard extragalactic
background light attenuation. We can generally expect more distant objects in
the secondary gamma-ray scenario, while axion-like particles do not
significantly alter the expected distribution. Yet, we find that, these results
strongly depend on the assumed magnetic field strength during the propagation.
We also provide source count predictions for the High Altitude Water Cherenkov
observatory (HAWC), the Large High Altitude Air Shower Observatory (LHAASO) and
a novel proposal of a hybrid detector.Comment: 16 pages, 4 figures, ApJ 2017 in pres
Mudcrab, Scylla spp, production in brackishwater ponds
This manual covers the specifics of grow-out operation — site selection, pond specification, pond preparation, source of juveniles, transport and stocking, care of pond and stock, feeds and feeding, harvest, postharvest.
Also includes costs-and-benefits analysis and a list of useful references.Mudcrab (Scylla spp) production in brackishwater ponds is now gaining popularity, especially in communities that need to supplement their income. The manual covers the following: Distribution; Grow-out operation in ponds - site selection, pond specification, pond preparation, source of juveniles, transport and stocking of juveniles, care of pond and stock, feeds and feeding, harvest, post-harvest; Production and profits; Cost and analysis. It is hoped that the manual will be of use to fishfarmers and aquaculturists, extensionists, and students of aquaculture not only in the Philippines but also in other mudcrab producing countries in Southeast Asia
Majorana fermions in pinned vortices
Exploiting the peculiar properties of proximity-induced superconductivity on
the surface of a topological insulator, we propose a device which allows the
creation of a Majorana fermion inside the core of a pinned Abrikosov vortex.
The relevant Bogolyubov-de Gennes equations are studied analytically. We
demonstrate that in this system the zero-energy Majorana fermion state is
separated by a large energy gap, of the order of the zero-temperature
superconducting gap , from a band of single-particle non-topological
excitations. In other words, the Majorana fermion remains robust against
thermal fluctuations, as long as the temperature remains substantially lower
than the critical superconducting temperature. Experimentally, the Majorana
state may be detected by measuring the tunneling differential conductance at
the center of the Abrikosov vortex. In such an experiment, the Majorana state
manifests itself as a zero-bias anomaly separated by a gap, of the order of
, from the contributions of the nontopological excitations.Comment: 9 pages, 2 eps figures, new references are added, several typos are
correcte
The single channel TripOff and the channel grouping on the WINER PL500F8 for the HMPID LV system
Organic Molecules in the Galactic Center. Hot Core Chemistry without Hot Cores
We study the origin of large abundances of complex organic molecules in the
Galactic center (GC). We carried out a systematic study of the complex organic
molecules CH3OH, C2H5OH, (CH3)2O, HCOOCH3, HCOOH, CH3COOH, H2CO, and CS toward
40 GC molecular clouds. Using the LTE approximation, we derived the physical
properties of GC molecular clouds and the abundances of the complex
molecules.The CH3OH abundance between clouds varies by nearly two orders of
magnitude from 2.4x10^{-8} to 1.1x10^{-6}. The abundance of the other complex
organic molecules relative to that of CH3OH is basically independent of the
CH3OH abundance, with variations of only a factor 4-8. The abundances of
complex organic molecules in the GC are compared with those measured in hot
cores and hot corinos, in which these complex molecules are also abundant. We
find that both the abundance and the abundance ratios of the complex molecules
relative to CH3OH in hot cores are similar to those found in the GC clouds.
However, hot corinos show different abundance ratios than observed in hot cores
and in GC clouds. The rather constant abundance of all the complex molecules
relative to CH3OH suggests that all complex molecules are ejected from grain
mantles by shocks. Frequent (similar 10^{5}years) shocks with velocities >6km/s
are required to explain the high abundances in gas phase of complex organic
molecules in the GC molecular clouds. The rather uniform abundance ratios in
the GC clouds and in Galactic hot cores indicate a similar average composition
of grain mantles in both kinds of regions. The Sickle and the Thermal Radio
Arches, affected by UV radiation, show different relative abundances in the
complex organic molecules due to the differentially photodissociation of these
molecules.Comment: 18 pages, 10 Postscript figures, uses aa.cls, aa.bst, 10pt.rtx,
natbib.sty, revsymb.sty revtex4.cls, aps.rtx and aalongtabl.sty. Accepted in
A&A 2006. version 2. relocated figures and tables. Language editor
suggestions. added reference
On the Practical Use in Hydrography of Filtered Daily Values of Mean Sea Level
It is shown that the mean monthly sea level of a non-permanent station can be referred to the long-term sea level of a permanent one when tidal stations are influenced by similar meteorological and oceanographical effects. Practical methods are derived : one is based on the direct transference and the other based on the ratio of the variances of the daily mean sea level. Applications of the methods are made for the ports of Cananeia, Ubatuba, Santos and Ilha Grande on the southern coast of Brazil
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