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We present a review of the presently available observations of the extragalactic background light (EBL) obtained by means of night sky photometry. The EBL is a quantity of great cosmological importance; areas which are directly affected include galaxy formation and evolution, the appropriateness of different cosmological models, and the local luminosity density due to galaxies and other matter in intergalactic space. The basic problem in measuring the EBL is its separation from other, much stronger components of the light of the night sky. None of the different observational techniques have succeeded in providing a generally accepted measurement of the EBL. After a review of available methods, we present new results from an experiment by Mattila and Schnur (1989) utilizing the dark cloud technique in the area of L1642, a high-latitude dark nebula in the galactic anticentre direction.
An analysis of fluctuations in the brightness of the Milky Way using the concept that interstellar matter occurs in the form of discrete clouds was first applied by Ambarzumian (1940, 1944). This theory was formulated in a general way and discussed in great detail in a series of papers by Chandrasekhar and Münch (1950a, 1950b, 1951, 1952), by Münch and Chandrasekhar (1952), and by Limber (1953). More recently Peters (1970) presented an analysis of this kind based on extensive photographic observational material. Although the influence of clumpiness of the dust distribution on the mean integrated starlight was thoroughly discussed in these papers, it has not been properly included in most of the photometric models of the Galaxy. Only the models of Caplan and Grec (1979) and Mattila (1980a, 1980b) incorporate these effects.
We have searched for point-like sources in eight fields mapped at two or three wavelengths between 90 μm and 180 μm with the ISOPHOT instrument aboard the ISO satellite. Most of the 55 sources detected are suspected to be extragalactic and cannot be associated with previously known objects. It is probable, also from the far-infrared (FIR) spectral energy distributions, that dust-enshrouded, distant galaxies form a significant fraction of the sources.
We present a tentative list of the detected extragalactic FIR-sources. Based on the analyzed data we estimate the number density of extragalactic sources at wavelengths 90 μm, 150 μm and 180 μm and at flux density levels down to 100 mJy to be 1 x 105 sr−1, 2x105 sr−1, and 3xl05 sr−1, respectively.
Models of strong galaxy evolution are in best agreement with our results, although the number of detections exceeds predictions of most models. No-evolution models can be rejected at a high confidence level. Comparison with COBE results indicates that at 90 μm the detected sources correspond to >20% of the extragalactic background light. At longer wavelengths the corresponding fraction is ~ 10%.
The higher spatial resolution and sensitivity of ISO allowed several extragalactic surveys to be extended to greater depth than obtained with IRAS. With the extended wavelength range deep surveys were performed for the first time at wavelengths up to ~ 200 μm. They favour galaxy models with strong evolution. With ISO's new capabilities the spectral energy distributions of larger samples of ULIRGs in the local universe and those of quasars and radio galaxies were determined. These data are applicable as templates to the more distant universe. Foreground components from zodiacal light and cirrus to the intracluster dust emission were studied in connection with their separation from the extragalactic background radiation.
The light of the night sky consists of atmospheric components (airglow, light scattered in the atmosphere) and – even in the case of spaceborne observations – of zodiacal, galactic and extragalactic light. Although all components are of similar importance, investigations on zodiacal light have profitted most by the space age since their object of research, the interplanetary dust cloud, became accessible to direct in-situ measurements. Lunar samples and measurements by micrometeoroid detectors provide individual and eventually detailed information on impact events, which however are limited in number and therefore restricted in statistical significance. Zodiacal light investigations involve scattered light of many particles in large volume elements and therefore provide global information about physical properties and spatial distribution of interplanetary dust grains, however just in terms of average values. Therefore both sources of information are complementary and a synthesis can only be achieved by synoptic interpretation of zodiacal light, micrometeoroid, and meteoroid investigations also including dynamical aspects. Measurements of zodiacal light (and emission) from rockets, manned or non manned spacecraft, and deep space probes gained drastically in importance compared to ground based observations. On the other hand investigations on airglow have become more and more a topic of geophysics Caeronomy). They remain relevant however to astronomy as far as photometric features are concerned. These general trends continued in the last triennium and have influenced the activities of our commission.
The light of the night sky includes several components which spread all over the celestial sphere. These light components are terrestrial (airglow), interplanetary (zodiacal light), galactic (integrated starlight, diffuse galactic light) and extragalactic (extragalactic background light). Thus the study of nature of each light source, covering large distance, is pursued in different fields of astronomy. However, the techniques of measurement for respective components are similar and the knowledge of other lights is indispensable even in the study of a particular component.
The different components of the light of the night sky have their origin in different formations of matter in the universe - encompassing a huge scale of distances ranging from a few kilometers in the earth’s atmosphere to the most distant known galaxies and beyond. Correspondingly, the borderlines to other Commissions are not very well defined and thus material relevant to Commission 21 can also be found in the reports of other Commissions on the following topics: zodiacal light and zodiacal IR emission (Comm. 22, 44), integrated starlight (33, 25), diffuse galactic light (34), extragalactic background light (47), airglow and atmospheric scattered light (50), and space-borne observations of the LONS (44). From the Commission 21 point of view the connecting link between these various fields is the special techniques utilized in the surface photometric measurements and reductions of background radiations which extend over the entire sky. One crucial problem is the separation of the LONS into its several components. The approach for solving this task is to utilize the different spatial distributions and different broad and narrow band spectral properties of each of the LONS component. Thus the successful measurement and separation of one of the LONS components requires a knowledge of the properties of all the other components. This situation has become apparent in recent years as the infrared background radiation database, provided by the Infrared Astronomical Satellite (IRAS), has been analyzed: both the zodiacal and galactic dust emissions have to be analyzed hand in hand, and both these components must be very accurately mastered before any conclusions are possible on the extragalactic component. It is also obvious that very similar problems are encountered in the ultraviolet and infrared wavelength regions as in the more traditional optical domain. Thus the techniques developed in one of these wavelength domains are directly applicable in the others.
The cold, dry, and stable air above the summits of the Antarctic plateau provides the best ground-based observing conditions from optical to sub-millimetre wavelengths to be found on the Earth. Pathfinder for an International Large Optical Telescope (PILOT) is a proposed 2 m telescope, to be built at Dome C in Antarctica, able to exploit these conditions for conducting astronomy at optical and infrared wavelengths. While PILOT is intended as a pathfinder towards the construction of future grand-design facilities, it will also be able to undertake a range of fundamental science investigations in its own right. This paper provides the performance specifications for PILOT, including its instrumentation. It then describes the kinds of projects that it could best conduct. These range from planetary science to the search for other solar systems, from star formation within the Galaxy to the star formation history of the Universe, and from gravitational lensing caused by exo-planets to that produced by the cosmic web of dark matter. PILOT would be particularly powerful for wide-field imaging at infrared wavelengths, achieving near diffraction-limited performance with simple tip–tilt wavefront correction. PILOT would also be capable of near diffraction-limited performance in the optical wavebands, as well be able to open new wavebands for regular ground-based observation, in the mid-IR from 17 to 40 μm and in the sub-millimetre at 200 μm.
In fluid mechanics, multicomponent fluid systems are generally treated either as homogeneous solutions or as completely immiscible parts of a multiphasic system. In immiscible systems, the main task in numerical simulations is to find the location of the interface evolving over time, driven by normal and tangential surface forces. The lattice-Boltzmann method (LBM), on the other hand, is based on a mesoscopic description of the multicomponent fluid systems, and appears to be a promising framework that can lead to realistic predictions of segregation in non-ideal mixtures of partially miscible fluids. In fact, the driving forces in segregation are of a molecular nature: there is competition between the intermolecular forces and the random thermal motion of the molecules. Since these microscopic mechanisms are not accessible from a macroscopic standpoint, the LBM can provide a bridge linking the microscopic and macroscopic domains. To this end, the first purpose of this article is to present the kinetic equations in their continuum forms for the description of the mixing and segregation processes in mixtures. This paper is limited to isothermal segregation; non-isothermal segregation was discussed by Philippi et al. (Phil. Trans. R. Soc., vol. 369, 2011, pp. 2292–2300). Discretization of the kinetic equations leads to evolution equations, written in LBM variables, directly amenable for numerical simulations. Here the dynamics of the kinetic model equations is demonstrated with numerical simulations of a spinodal decomposition problem with dissolution. Finally, some simplified versions of the kinetic equations suitable for immiscible flows are discussed.
There are numerous instruments for screening for depression. A feasible screen is good at both recognising and predicting depression.
To study the ability of the Depression Scale and its items to recognise and predict a depressive episode.
A sample of patients attending primary care was examined in 1991–1992 and again 7 years later. The accuracy of the Depression Scale at baseline and at follow-up was tested against the Short Form of the Composite International Diagnostic Interview (CIDI-SF) diagnosis of depression at follow-up. The sensitivity and specificity of the Depression Scale and its items were assessed.
Both baseline and follow-up Depression Scale scores were consistent with the CIDI–SF diagnoses. It was possible to find single items efficient at both recognising and predicting depression.
The Depression Scale is a useful screening instrument for depression, with both diagnostic and predictive validity.
Cometary globule CG 12 lies at the distance of 630 pc more than 200 pc above the Galactic plane. The cloud's structure could be due to the passage of a supernova blast wave. Curiously, the cometary tail points at the galactic plane which would put the putative supernova even farther above the Galactic plane than the globule. The globule contains a low/intermediate mass stellar cluster with at least 9 members (Williams et al. 1977). The head of CG 12 has been observed using NIR imaging (NTT SOFI), mm continuum (SEST SIMBA) and sub mm (APEX) and mm (SEST) spectroscopy (Haikala & Olberg 2006, Haikala et al.). The molecular material is distributed in a North-South 10' long elongated lane with two compact maxima separated by 3'. Strong C18O (3-2), (2-1) and (1-0) emission is detected in both maxima and both have an associated compact 1.2 mm continuum source. The Northern core, CG 12 N, is cold and is possibly still pre-stellar. A dense and compact core is observed in DCO+ and CS emission in the direction of the Southern core, CG 12 S. A remarkable C18O hot spot was detected in CG 12 S. This is the first detection of such a compact, warm object in a low mass star forming region. The hot spot can be modelled with a 60″ to 80″ diameter (~0.2 pc) hot (80 K ≲ Tex≲ 100 K) 1.6 solar mass clump (Haikala et al. 2006). The hot spot lies at the edge of a dense cloud core and on the axis of a highly collimated bipolar molecular outflow (White 1993). The driving source of the outflow is most probably embedded in the dense core. NIR imaging reveals a bright cone like feature with a faint counter cone in the centre of CG 12 S. The size of the CG 12 compact head, 1.1 pc by 1.8 pc, and the C18O mass larger than 100 solar masses are comparable to those of other nearby low/intermediate mass star formation regions.
We examine the intensity of scattered near-infrared (NIR) light in the case of interstellar clouds illuminated by the normal interstellar radiation field. We have developed a way to convert the observed surface brightness into estimates of the column density and have estimated the accuracy of the new method. The NIR intensities can be converted into reliable estimates of the column density in regions with AV up to almost 20 magnitudes. The errors can be further reduced with detailed radiative transfer modelling and by using the lower resolution information that is provided by the colour excess data of background stars. Therefore, NIR scattered light is a promising new way to map quiescent interstellar clouds at a high, even sub-arcsecond resolution.
Results from a large-scale, capture—recapture study of humpback whales Megaptera novaeangliae in the North Atlantic show that migration timing is influenced by feeding ground origin. No significant differences were observed in the number of individuals from any feeding area that were re-sighted in the common breeding area in the West Indies. However, there was a relationship between the proportion (logit transformed) of West Indies sightings and longitude (r2=0.97, F1,3=98.27, P=0.0022) suggesting that individuals feeding farther to the east are less likely to winter in the West Indies. A relationship was also detected between sighting date in the West Indies and feeding area. Mean sighting dates in the West Indies for individuals identified in the Gulf of Maine and eastern Canada were significantly earlier than those for animals identified in Greenland, Iceland and Norway (9.97 days, t179=3.53, P=0.00054). There was also evidence for sexual segregation in migration; males were seen earlier on the breeding ground than were females (6.63 days, t105=1.98, P=0.050). This pattern was consistently observed for animals from all feeding areas; a combined model showed a significant effect for both sex (F1=5.942, P=0.017) and feeding area (F3=4.756, P=0.0038). The temporal difference in occupancy of the West Indies between individuals from different feeding areas, coupled with sexual differences in migratory patterns, presents the possibility that there are reduced mating opportunities between individuals from different high latitude areas.
Strip scanning measurements with crossing position angles
have been carried out at 120 μm and 180 μm
with the ISOPHOT instrument aboard ISO to observe extended FIR
emission from six Abell clusters. The
raw I120 μm/I180 μm surface brightness ratio
including zodiacal light shows a bump towards Abell 1656 (Coma), dips
towards Abell 262 and Abell 2670, and is without an unambiguous
feature towards Abell 400, Abell 496, and Abell 4038. The subtraction
of the zodiacal light leaves the bump towards Abell 1656 still
present, while the dips towards Abell 262 and Abell 2670 are no longer
discernible. This behavior can be reconciled in Abell 1656 with a
localized excess of emitting material outside the Galaxy with
properties different from the galactic foreground cirrus, and in Abell
262 and Abell 2670 with galactic cirrus structures localized on the
line-of-sight to these clusters. At 120 μm the excess
towards Abell 1656 (Coma) is ≈ 0.2 MJy/sr, with an integrated
excess flux within the central region of 10'-15' diameter of ≈ 2.8 Jy. It is interpreted as
being due to thermal emission from intracluster dust distributed in
the hot X-ray emitting intracluster medium. Only a rough estimate of
the associated dust mass of MD ≈ 107 M⊙ can be derived, since the dust temperature is poorly constrained. The
visual extinction associated with this dust mass is negligible
(AV << 0.1 mag) and much smaller than claimed from
optical observations. No evidence for intracluster dust is found in
the other five clusters observed. The rather low inferred dust mass
in Abell 1656 together with the absence of a signature for
intracluster dust in the other clusters observed indicates
intracluster dust is likely not responsible for the excess X-ray
absorption seen in cooling flow clusters. These observations thereby
represent a further unsuccessful attempt in detecting the presumed final stage of the cooling flow material, in accord with quite a number of previous studies. Finally, the observed dimming of the high - redshift supernovae is unlikely be attributable to extinction caused
by dust in the intracluster or even a presumed intercluster medium.
The report discusses the possible multi-colour photometry of the
diffuse sky surface with the Astro and Spectro telescopes of GAIA.
The ordinary photometry of faint stars will give good results of the
background for at least 500 million spots on the sky. Measurement
from about 100 of these spots in a small area could be averaged to
obtain a precision of about 0.5 S10 of GAIA medium-band
photometry in each of the 5 million areas. It is concluded that GAIA
medium-band photometry is suited to tackle a whole range of
astrophysically interesting diffuse sky components. After modelling
and subtracting the time-variable Zodiacal Light, GAIA could provide
multi-wavelength all sky maps of the low galactic latitude Diffuse
Galactic Light and the high latitude Galactic Cirrus Clouds. Possibly
also the Extragalactic Background Light could be detected.
Background. Personality traits have shown considerable
heritable components. Association between
alleles of a polymorphism in the third exon of the dopamine D4 receptor
gene (DRD4) and the
personality trait Novelty Seeking has been reported. Recently, in a sample
non-psychiatric subjects we could not detect any significant relationships
between the same
polymorphism and Novelty Seeking related scales in the Karolinska Scales
of Personality (KSP).
However, there was a tendency in the direction of the proposed association.
There were also
tentative associations between an exon I 13 bp deletion polymorphism and
the personality traits
Socialization and Guilt.
Methods. We investigated a new Swedish population-based sample
(N=167) investigated with the
KSP for three DRD4 polymorphisms.
Results. Neither of the previous results were replicated.
Combining the previous and the present
samples did not give rise to any significant association between DRD4 polymorphisms
Conclusions. The dopamine D4 receptor gene is probably not
of importance to the different
personality dimensions as measured by the Karolinska Scales of Personality.
It is important to know which level of tactical preparedness is reached after completing lectures and training included in a medical curriculum. A computer-based interactive programme aimed for tactical training of emergency care tactics at the scene (Matimed,™ Matimed Ltd, Kuopio, Finland) was used in testing the skills of 20 medical students.
In this standardised test, every student first received guided introduction on the technical use of the programme. The test included four severely injured victims. The traumas used were hepatic rupture, flail chest, haemothorax, and femoral fracture. The students were tested in making decisions on the priority of care and transportation and in keeping the patients alive with appropriate emergency care until they were transported to a trauma centre.
Only five of20 (25%) succeeded in this task, 50% lost one victim and 25% lost two. The results show that the tactical preparedness of medical students is far from what is presumed. A more detailed analysis shows serious deficiencies in decision-making, priority order of actions, and in the use of available resources.
This type of interactive computer-aided training of tactics appropriately supplements theoretical lectures, and partially fills the need for practical training.
Hearing results are presented for 164 ears with chronic otitis media which were operated on radically and obliterated with a musculo-periosteal flap (Palva flap), and in which tympanoplasty was performed. The ears were followed-up annualy for 5–13 years (mean 6.8 years). Results are compared with the method of ossiculoplasty and with the condition of the stapes superstructure at operation. Ossiculoplasty using autogenous cortical bone columellas resulted in a somewhat greater improvement in the post-operative air-bone gap than ossiculoplasty with auto- or homo-graft ossicles, when compared wih the pre-operative gap. Similarly, the post-operative gap improved more in ears with an intact stapes superstructure than in ears in which the stapes superstructure was absent. The use of an autogenous cortical bone columella can be recommended in cases in which the patient's own ossicles are affected by disease and cannot be used.
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