4,967 research outputs found
A simplified protocol for detecting two systemic bait markers (Rhodamine B and iophenoxic acid) in small mammals
We developed a method of quantifying levels of fluorescence in the whiskers of wild stoats (Mustela erminea) using fluorescence microscopy and Axiovision 3.0.6.1 software. The method allows for discrimination between natural fluorescence present in or on a whisker, and the fluorescence resulting from the ingestion of the systemic marker Rhodamine B (RB), although some visual judgement is still required. We also developed a new high performance liquid chromatography (HPLC) protocol for detecting the systemic marker iophenoxic acid (IPA) in the blood of laboratory rats (Rattus norvegicus) and wild stoats. With this method, the blood of an animal that has consumed IPA can be tested for the presence of the foreign IPA compound itself. This is a more reliable test than the previous method, which measured the raised level of natural blood protein-bound iodine correlated with IPA absorption. The quantity of blood required from animal subjects is very small (10 μl), so the testing is less intrusive and the method can be extended to smaller species. The extraction technique uses methanol, rather than acids and heavy metal salts, thereby simplifying the procedure. Recovery of IPA is quantitative, giving a highly reliable reading. In experiments on captive rats the IPA method proved successful. Of 12 positively marked carcasses, two that had not been frozen for the 24 h before blood samples were taken showed relatively lower IPA levels. The same IPA detection method, as well as the whisker analysis for RB, was applied successfully to a population of wild stoats to which both Rhodamine B and IPA were made available at bait stations. The presence of both bait markers was detectable in rats for at least 21 days and in stoats for at least 27 days
Quantitative features of multifractal subtleties in time series
Based on the Multifractal Detrended Fluctuation Analysis (MFDFA) and on the
Wavelet Transform Modulus Maxima (WTMM) methods we investigate the origin of
multifractality in the time series. Series fluctuating according to a qGaussian
distribution, both uncorrelated and correlated in time, are used. For the
uncorrelated series at the border (q=5/3) between the Gaussian and the Levy
basins of attraction asymptotically we find a phase-like transition between
monofractal and bifractal characteristics. This indicates that these may solely
be the specific nonlinear temporal correlations that organize the series into a
genuine multifractal hierarchy. For analyzing various features of
multifractality due to such correlations, we use the model series generated
from the binomial cascade as well as empirical series. Then, within the
temporal ranges of well developed power-law correlations we find a fast
convergence in all multifractal measures. Besides of its practical significance
this fact may reflect another manifestation of a conjectured q-generalized
Central Limit Theorem
Hubble and Spitzer Observations of an Edge-on Circumstellar Disk around a Brown Dwarf
We present observations of a circumstellar disk that is inclined close to
edge-on around a young brown dwarf in the Taurus star-forming region. Using
data obtained with SpeX at the NASA Infrared Telescope Facility, we find that
the slope of the 0.8-2.5 um spectrum of the brown dwarf 2MASS J04381486+2611399
cannot be reproduced with a photosphere reddened by normal extinction. Instead,
the slope is consistent with scattered light, indicating that circumstellar
material is occulting the brown dwarf. By combining the SpeX data with mid-IR
photometry and spectroscopy from the Spitzer Space Telescope and previously
published millimeter data from Scholz and coworkers, we construct the spectral
energy distribution for 2MASS J04381486+2611399 and model it in terms of a
young brown dwarf surrounded by an irradiated accretion disk. The presence of
both silicate absorption at 10 um and silicate emission at 11 um constrains the
inclination of the disk to be ~70 deg, i.e. ~20 deg from edge-on. Additional
evidence of the high inclination of this disk is provided by our detection of
asymmetric bipolar extended emission surrounding 2MASS J04381486+2611399 in
high-resolution optical images obtained with the Hubble Space Telescope.
According to our modeling for the SED and images of this system, the disk
contains a large inner hole that is indicative of a transition disk (R_in~58
R_star~0.275 AU) and is somewhat larger than expected from embryo ejection
models (R_out=20-40 AU vs. R_out<10-20 AU).Comment: The Astrophysical Journal, in pres
Emission from Water Vapor and Absorption from Other Gases at 5-7.5 Microns in Spitzer-IRS Spectra of Protoplanetary Disks
We present spectra of 13 T Tauri stars in the Taurus-Auriga star-forming
region showing emission in Spitzer Space Telescope Infrared Spectrograph (IRS)
5-7.5 micron spectra from water vapor and absorption from other gases in these
stars' protoplanetary disks. Seven stars' spectra show an emission feature at
6.6 microns due to the nu_2 = 1-0 bending mode of water vapor, with the shape
of the spectrum suggesting water vapor temperatures > 500 K, though some of
these spectra also show indications of an absorption band, likely from another
molecule. This water vapor emission contrasts with the absorption from warm
water vapor seen in the spectrum of the FU Orionis star V1057 Cyg. The other
six of the thirteen stars have spectra showing a strong absorption band,
peaking in strength at 5.6-5.7 microns, which for some is consistent with
gaseous formaldehyde (H2CO) and for others is consistent with gaseous formic
acid (HCOOH). There are indications that some of these six stars may also have
weak water vapor emission. Modeling of these stars' spectra suggests these
gases are present in the inner few AU of their host disks, consistent with
recent studies of infrared spectra showing gas in protoplanetary disks.Comment: 33 pages, 9 figures, to appear in the 20 August, 2014, V791 - 2 issue
of the Astrophysical Journa
Spitzer-IRS Observations of FU Orionis Objects
We present 5-35 m spectra, taken with the Infrared Spectrograph (IRS) on
the Spitzer Space Telescope, of five FU Orionis objects: FU Ori, V1515 Cyg,
V1057 Cyg, BBW 76, and V346 Nor. All but V346 Nor reveal amorphous silicate
grains in emission at 10 m and 20 m, and show water-vapor absorption
bands at 5.8 and 6.8 m and SiO or possibly methane absorption at 8 m.
These absorption features closely match these bands in model stellar
photospheres -- signs of the gaseous photospheres of the inner regions of these
objects' accretion disks. The continuum emission at 5-8 m is also
consistent with such disks, and, for FU Orionis and BBW 76, longer-wavelength
emission may be fit by a model which includes moderate disk flaring. V1057 Cyg
and V1515 Cyg have much more emission at longer wavelengths than the others,
perhaps evidence of substantial remnant of their natal, infalling envelopes.Comment: 30 pages, 8 figures, accepted by Ap
Uncertainty Modelling to Evaluate Nitrogen Balances As a Tool to Determine N2 and N2O Formation in Ammonia Bioscrubbers
Biological scrubbers aim at reducing gaseous ammonia emissions by transferring it to a water phase followed by conversion to nitrite and nitrate. A small part of the removed nitrogen may be emitted as N 2 and N 2O produced as a result of denitrification processes. Due to the large greenhouse warming potential of N 2O, even a small emission could be a point of concern. Determining these N losses in form of N 2 and N 2O via nitrogen balance is an alternative, but little is known about the uncertainty associated to this method. The main aim of this work was to develop an uncertainty model that evaluated N-balances in biological scrubbers in terms of result uncertainty. Secondary objectives were to provide a methodology to determine individual uncertainties involved, and to conduct a sensitivity analysis to identify the main contributors to the final uncertainty. For a defined scenario (biotrickling scrubber, 70% NH 3 removal; 5% of inlet N-NH 3 lost as N 2 and N 2O), the standard uncertainty expressed in relative terms of the average was 132% (released N in form of N 2 and N 2O). Main contributors to the final uncertainty were airflow rate and water volume in the scrubber basin. Uncertainty of the measurements of gaseous NH 3 concentrations and N compounds in water had a reduced effect on the final uncertainty. Based on these results, N balances are not recommended to evaluate N 2 and N 2O formation in biological scrubbers, at least for the conditions considered in this work. © Copyright 2012, Mary Ann Liebert, Inc.The auhors would like to thank the Netherlands Ministry of Economic Affairs, Agriculture and Innovation, and the Netherlands Ministry of Infrastructure and the Environment, for financial support.Estellés Barber, F.; Calvet Sanz, S.; Melse, RW.; Ogink, N. (2012). Uncertainty Modelling to Evaluate Nitrogen Balances As a Tool to Determine N2 and N2O Formation in Ammonia Bioscrubbers. Environmental Engineering Science. 29(6):1-6. doi:10.1089/ees.2011.01891629
SPITZER: Accretion in Low Mass Stars and Brown Dwarfs in the Lambda Orionis Cluster
We present multi-wavelength optical and infrared photometry of 170 previously
known low mass stars and brown dwarfs of the 5 Myr Collinder 69 cluster (Lambda
Orionis). The new photometry supports cluster membership for most of them, with
less than 15% of the previous candidates identified as probable non-members.
The near infrared photometry allows us to identify stars with IR excesses, and
we find that the Class II population is very large, around 25% for stars (in
the spectral range M0 - M6.5) and 40% for brown dwarfs, down to 0.04 Msun,
despite the fact that the H(alpha) equivalent width is low for a significant
fraction of them. In addition, there are a number of substellar objects,
classified as Class III, that have optically thin disks. The Class II members
are distributed in an inhomogeneous way, lying preferentially in a filament
running toward the south-east. The IR excesses for the Collinder 69 members
range from pure Class II (flat or nearly flat spectra longward of 1 micron), to
transition disks with no near-IR excess but excesses beginning within the IRAC
wavelength range, to two stars with excess only detected at 24 micron.
Collinder 69 thus appears to be at an age where it provides a natural
laboratory for the study of primordial disks and their dissipation.Comment: ApJ, in pres
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