2,720 research outputs found
C18O (3-2) observations of the Cometary Globule CG 12: a cold core and a C18O hot spot
The feasibility of observing the C18O (3-2) spectral line in cold clouds with
the APEX telescope has been tested. As the line at 329.330 GHz lies in the wing
of a strong atmospheric H2O absorption it can be observed only at high altitude
observatories. Using the three lowest rotational levels instead of only two
helps to narrow down the physical properties of dark clouds and globules. The
centres of two C18O maxima in the high latitude low mass star forming region CG
12 were mapped in C18O (3-2) and the data were analyzed together with spectral
line data from the SEST. The T_MB(3-2)/T_MB(2-1) ratio in the northern C18O
maximum, CG 12 N, is 0.8, and in the southern maximum, CG 12 S, ~2. CG 12 N is
modelled as a 120'' diameter (0.4pc) cold core with a mass of 27 Msun. A small
size maximum with a narrow, 0.8 kms-1, C18O (3-2) spectral line with a peak
temperature of T_MB ~11 K was detected in CG 12 S. This maximum is modelled as
a 60'' to 80'' diameter (~0.2pc) hot (80 K < Tex < 200 K) ~1.6 Msun clump. The
source lies on the axis of a highly collimated bipolar molecular outflow near
its driving source. This is the first detection of such a compact, warm object
in a low mass star forming region.Comment: APEX A&A special issue, accepte
Light and colour of cirrus, translucent and opaque dust in the high-latitude area of LDN 1642
We have performed a 5-colour surface photometric study of the
high-galactic-latitude area of dark nebula LDN 1642. Scattered light properties
are presented of diffuse, translucent and opaque dust over the range of 3500 --
5500 A. Far infrared absolute photometry at 200 um improves the precision of
and provides a zero point to the extinction. The intensity of the scattered
light depends on dust column density in a characteristic way: for optically
thin dust the intensity first increases linearly, then turns to a saturation
value; at still larger extinctions the intensity turns down to a slow decrease.
The value of the saturated intensity maximum shifts in a systematic way,
from 1.5 mag at 3500 A, to mag at 5500 A. The intensity
curves offer a straight-forward explanation for the behaviour of the
scattered-light colours. At the intensity peak the colour agrees with the
integrated starlight colour, while it is bluer at the low- and redder at the
high-column-density side of the peak, respectively. These colour changes are a
direct consequence of the wavelength dependence of the extinction. We have
compared the colours of the LDN 1642 area with other relevant observational
studies: high-latitude diffuse/translucent clouds, wide-field cirrus dust; and
externally illuminated AGB-star envelopes. For extragalactic
low-surface-brightness sources cirrus is an unwanted foreground contaminant.
Our results for cirrus colours can help to distinguish cases where a diffuse
plume or stream, apparently associated with a galaxy or a group or cluster, is
more likely a local cirrus structure.
Keywords: ISM: dust, extinction -- ISM: clouds, individual LDN 1642 --
Galaxy: solar neighbourhood -- Astronomical instruments, methods and
techniques: methods -- Physical data and processes: scatteringComment: 20 pages, 10 figures, accepted for publication in MNRAS, published as
MNRAS advance article on June 27 202
Higher-dimensional multifractal value sets for conformal infinite graph directed Markov systems
We give a description of the level sets in the higher dimensional
multifractal formalism for infinite conformal graph directed Markov systems. If
these systems possess a certain degree of regularity this description is
complete in the sense that we identify all values with non-empty level sets and
determine their Hausdorff dimension. This result is also partially new for the
finite alphabet case.Comment: 20 pages, 1 figur
In situ determination of nitrogen content in InGaAsN quantum wells
The growth of InGaAsN/GaAs multiple quantum well structures by metal-organic vapor phase epitaxy is monitored by in situ reflectometry. The nitrogen incorporation is found to depend superlinearly on the precursor flow and a threshold value for the flow is observed. By in situmeasurements of the InGaAsN quantum well samples with a fixed indium content, the change in the reflectance during the quantum wellgrowth is found to be linearly dependent on the quantum well nitrogen content. A model to determine the nitrogen content already during the growth is developed. Moreover, the field of application of in situ reflectance monitoring is extended from thick layers to thin layers, including quantum wells.Peer reviewe
Radio monitoring of NGC 7469: Late time radio evolution of SN 2000ft and the circumnuclear starburst in NGC 7469
We present the results of an eight-year long monitoring of the radio emission
from the Luminous Infrared Galaxy (LIRG) NGC 7469, using 8.4 GHz Very Large
Array (VLA) observations at 0.3'' resolution. Our monitoring shows that the
late time evolution of the radio supernova SN 2000ft follows a decline very
similar to that displayed at earlier times of its optically thin phase. The
late time radio emission of SN 2000ft is therefore still being powered by its
interaction with the presupernova stellar wind, and not with the interstellar
medium (ISM). Indeed, the ram pressure of the presupernova wind is \rho_w v_w^2
\approx 7.6E-9 dyn/cm^2, at a supernova age of approximately 2127 days, which
is significantly larger than the expected pressure of the ISM around SN 2000ft.
At this age, the SN shock has reached a distance r_{sh \approx 0.06 pc, and our
observations are probing the interaction of the SN with dense material that was
ejected by the presupernova star about 5820 years prior to its explosion. From
our VLA monitoring, we estimate that the swept-up mass by the supernova shock
after about six years of expansion is \approx 0.29 M_sun, assuming an average
expansion speed of the supernova of 10000 km/s.
We also searched for recently exploded core-collapse supernovae in our VLA
images. Apart from SN 2000ft (S_\nu \approx 1760 microJy at its peak,
corresponding to 1.1E28 erg/s/Hz, we found no evidence for any other radio
supernova (RSN) more luminous than \approx 6.0E26 erg/s/Hz, which suggests that
no other Type IIn SN has exploded since 2000 in the circumnuclear starburst of
NGC 7469.Comment: 10 pages, 5 figures, accepted for publication in MNRA
Fluid-mediated, brittle–ductile deformation at seismogenic depth – Part 2: Stress history and fluid pressure variations in a shear zone in a nuclear waste repository (Olkiluoto Island, Finland)
Abstract. The microstructural record of fault rocks active at the brittle–ductile transition zone (BDTZ) may retain information on the rheological parameters driving the switch in deformation mode and on the role of stress and fluid pressure in controlling different fault slip behaviours. In this study we analysed the deformation microstructures of the strike-slip fault zone BFZ045 in Olkiluoto (SW Finland), located in the site of a deep geological repository for nuclear waste. We combined microstructural analysis, electron backscatter diffraction (EBSD), and mineral chemistry data to reconstruct the variations in pressure, temperature, fluid pressure, and differential stress that mediated deformation and strain localization along BFZ045 across the BDTZ. BFZ045 exhibits a mixed ductile–brittle deformation, with a narrow (<20 cm thick) brittle fault core with cataclasites and pseudotachylytes that overprint a wider (60–100 cm thick) quartz-rich mylonite. Mylonitic deformation took place at 400–500 ∘C and 3–4 kbar, typical of the greenschist facies metamorphism at the base of the seismogenic crust. We used the recrystallized grain size piezometry for quartz to document a progressive increase in differential stress, from ca. 50 to ca. 120 MPa, towards the shear zone centre during mylonitization and strain localization. Syn-kinematic quartz veins formed along the mylonitic foliation due to transiently high pore fluid pressure (up to lithostatic value). The overprint of the veins by dynamic recrystallization and mylonitic creep is further evidence of the occurrence of brittle events under overall ductile conditions. We propose a conceptual model in which the ductile–brittle deformation cycle was controlled by transient oscillations in fluid pressure and progressively higher differential stress, possibly occurring in a narrowing shear zone deforming towards the peak strength of the crust at the BDTZ. </jats:p
Twinfilin is required for actin-dependent developmental processes in Drosophila
The actin cytoskeleton is essential for cellular remodeling and many developmental and morphological processes. Twinfilin is a ubiquitous actin monomer-binding protein whose biological function has remained unclear. We discovered and cloned the Drosophila twinfilin homologue, and show that this protein is ubiquitously expressed in different tissues and developmental stages. A mutation in the twf gene leads to a number of developmental defects, including aberrant bristle morphology. This results from uncontrolled polymerization of actin filaments and misori-entation of actin bundles in developing bristles. In wildtype bristles, twinfilin localizes diffusively to cytoplasm and to the ends of actin bundles, and may therefore be involved in localization of actin monomers in cells. We also show that twinfilin and the ADF/cofilin encoding gene twinstar interact genetically in bristle morphogenesis. These results demonstrate that the accurate regulation of size and dynamics of the actin monomer pool by twinfilin is essential for a number of actin-dependent developmental processes in multicellular eukaryotes
Small union with large set of centers
Let be a fixed set. By a scaled copy of around
we mean a set of the form for some .
In this survey paper we study results about the following type of problems:
How small can a set be if it contains a scaled copy of around every point
of a set of given size? We will consider the cases when is circle or sphere
centered at the origin, Cantor set in , the boundary of a square
centered at the origin, or more generally the -skeleton () of an
-dimensional cube centered at the origin or the -skeleton of a more
general polytope of .
We also study the case when we allow not only scaled copies but also scaled
and rotated copies and also the case when we allow only rotated copies
Hyvinvoinnin turvaamisen rajat : Näköaloja talouskriisiin ja hyvinvointivaltion kehitykseen Suomessa
Miten syksyllä 2008 alkanut globaali talouskriisi vaikuttaa pitkällä aikavälillä suomalaiseen hyvinvointivaltioon? Jos olisimme antiikin Kreikassa, voisimme mennä Delfoin oraakkelin luo Apollonin temppeliin ja esittää tämän kysymyksen ennuspapittarelle. Eräänä lokakuun päivänä 2009 Kelan tiloihin kokoontui joukko suomalaisia hyvinvointivaltion huippuasiantuntijoita. He kertoivat julkisen talouden, kansalaisten toimeentulon ja terveyden näkökulmista kolmelle ”professori-oraakkelille” eli tanskalaiselle Nina Smithille, ruotsalaiselle Johan Fritzellille ja saksalaisille Karl Hinrichsille Suomen kokemuksista edellisestä, 1990-luvun alun lamasta, sen jälkeisestä kehityksestä sekä omista tulevaisuuden arvioistaan. Seuraavana päivänä oraakkelit lausuivat ennustuksensa, joka paljastetaan tässä raportissa.10,00 euro
Revisiting the progenitor of the low-luminosity type II-plateau supernova, SN 2008bk
The availability of updated model atmospheres for red supergiants and
improvements in single and binary stellar evolution models, as well as
previously unpublished data prompted us to revisit the progenitor of
low-luminosity type II-Plateau supernova, SN 2008bk. Using mid-IR data in
combination with dust models, we find that high temperature (4250-4500 K), high
extinction (E(B-V)>0.7) solutions are incompatible with the data. We therefore
favour a cool (~3500-3700 K) progenitor with a luminosity of log(L/Lsun)~4.53.
Comparing with evolutionary tracks, we infer progenitor masses in the 8-10 Msun
range in agreement with some previous studies. This mass is consistent with the
observed pattern of low-luminosity Type IIP SNe coming from the explosion of
RSGs at the lower extremum for core-collapse. We also present multi-epoch data
of the progenitor, but do not find clear evidence of variability.Comment: 9 pages, 6 figure
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