1,277 research outputs found
Overvåking NOAH Langøya 2003. Strandsoneregistreringer samt miljøgifter i blåskjell og sedimenter
Årsliste 2004Analyser av miljøgifter i blåskjell og sedimenter fra området utenfor NOAHs behandlingsanlegg for farlig avfall på Langøya i Oslofjorden har siden overvåkingen startet i 1994 stort sett indikert en god miljøtilstand i området. Tilstanden i blåskjell i 2003 kan for det meste klassifiseres som ubetydelig til moderat forurenset. Arsen og vanadium viste overkonsentrasjoner, dvs. over anntatt høyt bakgrunnsnivå, i hele undersøkelsesområdet, med høyest verdier på de to stasjonene lengst unna Langøya (B7 og BK). Overkonsentrasjoner av bly og krom var begrenset til Langøya-stasjonene. Kadmium ble kun registrert med overkonsentrasjoner ved bulk-kaia. Det var lave nivåer av organiske miljøgifter på stasjon B3 og BK (Mølen), men TBT var forhøyet på begge stasjonene (hhv. klasse III og klasse II). De nye prøvetakingene utenfor bulk-kaia bekreftet at en har et problem med kontaminering av bly og kadmium utenfor kaia. Problemet er imidlertid begrenset til et mindre område. Siden 1996 har det vært en signifikant oppadgående trend i konsentrasjonen av arsen, kadmium og bly i blåskjell på stasjon B3 utenfor kaia. Nikkel viste derimot nedadgående trend på B3. Forøvrig var det ingen trender i resultatene. De endringer hos strandsoneorganismer som er observert i forhold til tidligere år indikerer ingen redusert kvalitet hos de biologiske samfunnene på Langøya.NOAH Langøya A
Implications of a solar-system population of massive 4th generation neutrinos for underground searches of monochromatic neutrino-annihilation signals
It has been recently pointed out that any primary galactic population of
Weakly Interacting Massive Particles (WIMP) generates, through collisions with
solar matter, a secondary population of ``slow'' WIMPs trapped in the inner
solar system. We show that taking into account this ``slow'' solar-system
population dramatically enhances the possibility to probe the existence of
stable massive neutrinos (of a 4th generation) in underground neutrino
experiments. Our work suggests that a reanalysis of existing underground
neutrino data should be able to bring extremely tight constraints on the
possible existence of a stable massive 4th neutrino.Comment: 15 pages, 4 figure
Clock drawing performance in cognitively normal elderly
The Clock Drawing Test (CDT) is a common neuropsychological measure sensitive to cognitive changes and functional skills (e.g., driving test performance) among older adults. However, normative data have not been adequately developed. We report the distribution of CDT scores using three common scoring systems [Mendez, M. F., Ala, T., & Underwood, K. L. (1992). Development of scoring criteria for the Clock Drawing Task in Alzheimer's Disease. Journal of the American Geriatrics Society, 40, 1095-1099; Cahn, D. A., Salmon, D. P., Monsch, A. U., Butters, N., Wiederholt, W. C., & Corey-Bloom, J. (1996). Screening for dementia of the Alzheimer type in the community: The utility of the Clock Drawing Test. Archives of Clinical Neuropsychology, 11(6), 529-539], among 207 cognitively normal elderly. The systems were well correlated, took little time to use, and had high inter-rater reliability. We found statistically significant differences in CDT scores based on age and WRAT-3 Reading score, a marker of education quality. We present means, standard deviations, and t- and z-scores based on these subgroups. We found that "normal" CDT performance includes a wider distribution of scores than previously reported. Our results may serve as useful comparisons for clinicians wishing to know whether their patients perform in the general range of cognitively normal elderly. © 2007 National Academy of Neuropsychology
Calculating exclusion limits for Weakly Interacting Massive Particle direct detection experiments without background subtraction
Competitive limits on the weakly interacting massive particle (WIMP)
spin-independent scattering cross section are currently being produced by 76Ge
detectors originally designed to search for neutrinoless double beta decay,
such as the Heidelberg-Moscow and IGEX experiments. In the absence of
background subtraction, limits on the WIMP interaction cross section are set by
calculating the upper confidence limit on the theoretical event rate, given the
observed event rate. The standard analysis technique involves calculating the
90% upper confidence limit on the number of events in each bin, and excluding
any set of parameters (WIMP mass and cross-section) which produces a
theoretical event rate for any bin which exceeds the 90% upper confidence limit
on the event rate for that bin. We show that, if there is more than one energy
bin, this produces exclusion limits that are actually at a lower degree of
confidence than 90%, and are hence erroneously tight. We formulate criteria
which produce true 90% confidence exclusion limits in these circumstances,
including calculating the individual bin confidence limit for which the overall
probability that no bins exceeds this confidence limit is 90% and calculating
the 90% minimum confidence limit on the number of bins which exceed their
individual bin 90% confidence limits. We then compare the limits on the WIMP
cross-section produced by these criteria with those found using the standard
technique, using data from the Heidelberg-Moscow and IGEX experiments.Comment: 6 pages, 3 figures, 3 tables, shortened version to appear in Phys.
Rev. D, contents otherwise unchange
The 69 {}m forsterite band in spectra of protoplanetary disks. Results from the Herschel DIGIT programme
Context. We have analysed far-infrared spectra of 32 circumstellar disks around Herbig Ae/Be and T Tauri stars obtained within the Herschel key programme Dust, Ice and Gas in Time (DIGIT). The spectra were taken with the Photodetector Array Camera and Spectrometer (PACS) on board the Herschel Space Observatory. In this paper we focus on the detection and analysis of the 69 {}m emission band of the crystalline silicate forsterite.
Aims: This work aims at providing an overview of the 69 {}m forsterite bands present in the DIGIT sample. We use characteristics of the emission band (peak position and FWHM) to derive the dust temperature and to constrain the iron content of the crystalline silicates. With this information, constraints can be placed on the spatial distribution of the forsterite in the disk and the formation history of the crystalline grains.
Methods: The 69 {}m forsterite emission feature is analysed in terms of position and shape to derive the temperature and composition of the dust by comparison to laboratory spectra of that band. The PACS spectra are combined with existing Spitzer IRS spectra and we compare the presence and strength of the 69 {}m band to the forsterite bands at shorter wavelengths.
Results: A total of 32 disk sources have been observed. Out of these 32, 8 sources show a 69 {}m emission feature that can be attributed to forsterite. With the exception of the T Tauri star AS 205, all of the detections are for disks associated with Herbig Ae/Be stars. Most of the forsterite grains that give rise to the 69 {}m bands are found to be warm (~{}100-200 K) and iron-poor (less than ~{}2% iron). AB Aur is the only source where the emission cannot be fitted with iron-free forsterite requiring approximately 3-4% of iron.
Conclusions: Our findings support the hypothesis that the forsterite grains form through an equilibrium condensation process at high temperatures. The large width of the emission band in some sources may indicate the presence of forsterite reservoirs at different temperatures. The connection between the strength of the 69 and 33 {}m bands shows that at least part of the emission in these two bands originates fom the same dust grains. We further find that any model that can explain the PACS and the Spitzer IRS observations must take the effects of a wavelength dependent optical depth into account. We find weak indications of a correlation of the detection rate of the 69 {}m band with the spectral type of the host stars in our sample. However, the sample size is too small to obtain a definitive result. Appendix A is available in electronic form at http://www.aanda.or
Stripes and holes in a two-dimensional model of spinless fermions and hardcore bosons
We consider a Hubbard-like model of strongly-interacting spinless fermions
and hardcore bosons on a square lattice, such that nearest neighbor occupation
is forbidden. Stripes (lines of holes across the lattice forming antiphase
walls between ordered domains) are a favorable way to dope this system below
half-filling. The problem of a single stripe can be mapped to a spin-1/2 chain,
which allows understanding of its elementary excitations and calculation of the
stripe's effective mass for transverse vibrations. Using Lanczos exact
diagonalization, we investigate the excitation gap and dispersion of a hole on
a stripe, and the interaction of two holes. We also study the interaction of
two, three, and four stripes, finding that they repel, and the interaction
energy decays with stripe separation as if they are hardcore particles moving
in one (transverse) direction. To determine the stability of an array of
stripes against phase separation into particle-rich phase and hole-rich liquid,
we evaluate the liquid's equation of state, finding the stripe-array is not
stable for bosons but is possibly stable for fermions.Comment: 24 pages, 18 figure
Primordial perturbations and non-Gaussianities from modulated trapping
We propose a new mechanism to generate primordial curvature perturbations,
based on the resonant production of particles during inflation. It is known
that this phenomenon can trap the inflaton for a fraction of e-fold. This
effect is governed by the mass of the produced particles and by their coupling
to the inflaton, parameters which can depend on the expectation value of other
fields. If one of such additional fields - a 'modulaton' - is light, then its
fluctuations, acquired during the earlier stages of inflation, will induce a
spatial modulation of the trapping, and thus of the end of inflation,
corresponding to a curvature perturbation. We calculate the power spectrum,
bispectrum and trispectrum of the curvature perturbations generated by this
mechanism, taking into account the perturbations due to the inflaton
fluctuations as well. We find that modulated trapping could provide the main
contribution to the observed power spectrum and lead to detectable primordial
non-gaussianities.Comment: 16 pages, 2 figure
The Supersymmetric Standard Models with Decay and Stable Dark Matters
We propose two supersymmetric Standard Models (SMs) with decaying and stable
dark matter (DM) particles. To explain the SM fermion masses and mixings and
have a heavy decay DM particle S, we consider the Froggatt-Nielsen mechanism by
introducing an anomalous U(1)_X gauge symmetry. Around the string scale, the
U(1)_X gauge symmetry is broken down to a Z_2 symmetry under which S is odd
while all the SM particles are even. S obtains a vacuum expectation value
around the TeV scale, and then it can three-body decay dominantly to the
second/third family of the SM leptons in Model I and to the first family of the
SM leptons in Model II. Choosing a benchmark point in the constrained minimal
supersymmetric SM with exact R parity, we show that the lightest neutralino DM
is consistent with the CDMS II experiment. Considering S three-body decay and
choosing suitable parameters, we show that the PAMELA and Fermi-LAT experiments
and the PAMELA and ATIC experiments can be explained in Model I and Model II,
respectively.Comment: RevTex4, 26 pages, 6 figures, references added, version to appear in
EPJ
Are there eta-Helium bound states?
Using multiple scattering theory the scattering lengths of mesons on
helium nuclei are calculated and checked against final state
interactions from the He and He
reactions. The existence of an He quasibound state is indicated.Comment: revtex, 23 pages, 3 figures available by fax or mai
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