140 research outputs found
Tasting Phenylthiocarbamide (PTC): A New Integrative Genetics Lab with an Old Flavor
First reported in the early 1930s, variation in the ability to taste phenylthiocarbamide (PTC) has since become one of the most widely studied of all human genetic traits. Guo and Reed (2001) provide an excellent review of work on this polymorphism prior to the identification and sequencing of the PTC gene by Kim et al. (2003), and Wooding (2006) provides a stimulating historical review of the role various scientists have played in the study of PTC taste sensitivity and the importance of these studies in relation to natural selection. Identification of the PTC gene and a number of subsequent publications (Wooding et al., 2004; Kim et al., 2005; Wooding et al., 2006) have provided the basis for a new, integrative laboratory investigation of PTC taste sensitivity. This genetics laboratory culminates in the use of the polymerase chain reaction (PCR) and restriction endonuclease digestion to determine the PTC genotype of each student. But âgetting there is half the funâ and, in this case, âgetting thereâ requires students to use not only their knowledge of molecular techniques in genetics but also their knowledge of Mendelian genetics, population genetics, probability, and pedigree analysis. The other âhalf the funâ in this case is that in determining their PTC phenotypes and genotypes, students are learning something about themselves
The DEEP2 Galaxy Redshift Survey: Redshift Identification of Single-Line Emission Galaxies
We present two methods for determining spectroscopic redshifts of galaxies in
the DEEP2 survey which display only one identifiable feature, an emission line,
in the observed spectrum ("single-line galaxies"). First, we assume each single
line is one of the four brightest lines accessible to DEEP2: Halpha, [OIII]
5007, Hbeta, or [OII] 3727. Then, we supplement spectral information with BRI
photometry. The first method, parameter space proximity (PSP), calculates the
distance of a single-line galaxy to galaxies of known redshift in (B-R), (R-I),
R, observed wavelength parameter space. The second method is an artificial
neural network (ANN). Prior information, such as allowable line widths and
ratios, rules out one or more of the four lines for some galaxies in both
methods. Based on analyses of evaluation sets, both methods are nearly perfect
at identifying blended [OII] doublets. Of the lines identified as Halpha in the
PSP and ANN methods, 91.4% and 94.2% respectively are accurate. Although the
methods are not this accurate at discriminating between [OIII] and Hbeta, they
can identify a single line as one of the two, and the ANN method in particular
unambiguously identifies many [OIII] lines. From a sample of 640 single-line
spectra, the methods determine the identities of 401 (62.7%) and 472 (73.8%)
single lines, respectively, at accuracies similar to those found in the
evaluation sets.Comment: 11 pages, 6 figures, accepted to Ap
Infrared Galaxies in the Field of the Massive Cluster Abell S1063: Discovery of a Luminous Kiloparsec-Sized HII Region in a Gravitationally Lensed IR-Luminous Galaxy at
Using the Spitzer Space Telescope and Herschel Space Observatory, we have
conducted a survey of infrared galaxies in the field of the galaxy cluster
Abell S1063 (AS1063) at , which is one of the most massive clusters
known and a target of the HST CLASH and Frontier-Field surveys. The
Spitzer/MIPS 24 m and Herschel/PACS & SPIRE images revealed that the core
of AS1063 is surprisingly devoid of infrared sources, showing only a few
detectable sources within the central r. There is, however, one
particularly bright source (2.3 mJy at 24 m; 106 mJy at 160 m), which
corresponds to a background galaxy at . The modest magnification factor
(4.0) implies that this galaxy is intrinsically IR-luminous (L). What is particularly interesting about
this galaxy is that HST optical/near-infrared images show a remarkably bright
and large (1 kpc) clump at one edge of the disk. Our follow-up
optical/near-infrared spectroscopy shows Balmer (H-H8) and forbidden
emission from this clump ([OII] 3727, [OIII]
4959,5007, [NII] 6548,6583), indicating that it
is a HII region. The HII region appears to have formed in-situ, as
kinematically it is part of a rotating disk, and there is no evidence of nearby
interacting galaxies. With an extinction correction of A mag, the
star formation rate of this giant HII region is 10 M yr,
which is exceptionally large, even for high redshift HII regions. Such a large
and luminous HII region is often seen at but quite rare in the nearby
Universe.Comment: Accepted for publication in the Astrophysical Journal. 29 pages, 15
figure
The DEEP2 Redshift Survey: Lyman Alpha Emitters in the Spectroscopic Database
We present the first results of a search for Lyman-alpha emitters (LAEs) in
the DEEP2 spectroscopic database that uses a search technique that is different
from but complementary to traditional narrowband imaging surveys. We have
visually inspected ~20% of the available DEEP2 spectroscopic data and have
found nine high-quality LAEs with clearly asymmetric line profiles and an
additional ten objects of lower quality, some of which may also be LAEs. Our
survey is most sensitive to LAEs at z=4.4-4.9 and that is indeed where all but
one of our high-quality objects are found. We find the number density of our
spectroscopically-discovered LAEs to be consistent with those found in
narrowband imaging searches. The combined, averaged spectrum of our nine
high-quality objects is well fit by a two-component model, with a second,
lower-amplitude component redshifted by ~420 km/s with respect to the primary
Lyman-alpha line, consistent with large-scale outflows from these objects. We
conclude by discussing the advantages and future prospects of blank-sky
spectroscopic surveys for high-z LAEs.Comment: Accepted for publication in Ap
Adaptive Autoimmunity and Foxp3-Based Immunoregulation in Zebrafish
Background: Jawed vertebrates generate their immune-receptor repertoire by a recombinatorial mechanism that has the potential to produce harmful autoreactive lymphocytes. In mammals, peripheral tolerance to self-antigens is enforced by Foxp3+ regulatory T cells. Recombinatorial mechanisms also operate in teleosts, but active immunoregulation is thought to be a late incorporation to the vertebrate lineage. Methods/Principal Findings: Here we report the characterization of adaptive autoimmunity and Foxp3-based immunoregulation in the zebrafish. We found that zebrafish immunization with an homogenate of zebrafish central nervous system (zCNS) triggered CNS inflammation and specific antibodies. We cloned the zebrafish ortholog for mammalian Foxp3 (zFoxp3) which induced a regulatory phenotype on mouse T cells and controlled IL-17 production in zebrafish embryos. Conclusions/Significance: Our findings demonstrate the acquisition of active mechanisms of self-tolerance early in vertebrate evolution, suggesting that active regulatory mechanisms accompany the development of the molecular potential for adaptive autoimmunity. Moreover, they identify the zebrafish as a tool to study the molecular pathways controlling adaptive immunity
The DEEP2 Redshift Survey: Lyα Emitters in the Spectroscopic Database
We present the first results of a search for Lyα emitters (LAEs) in the DEEP2 spectroscopic database that uses a search technique that is different from but complementary to traditional narrowband imaging surveys. We have visually inspected ~20% of the available DEEP2 spectroscopic data and have found nine high-quality LAEs with clearly asymmetric line profiles and an additional 10 objects of lower quality, some of which may also be LAEs. Our survey is most sensitive to LAEs at z = 4.4â4.9 and that is indeed where all but one of our high-quality objects are found. We find the number density of our spectroscopically discovered LAEs to be consistent with those found in narrowband imaging searches. The combined, averaged spectrum of our nine high-quality objects is well fit by a two-component model, with a second, lower amplitude component redshifted by ~420 km s^(â1) with respect to the primary Lyα line, consistent with large-scale outflows from these objects. We conclude by discussing the advantages and future prospects of blank-sky spectroscopic surveys for high-z LAEs
Transverse Sizes of CIV Absorption Systems Measured from Multiple QSO Sightlines
We present tomography of the circum-galactic metal distribution at redshift
1.7 to 4.5 derived from echellete spectroscopy of binary quasars. We find CIV
systems at similar redshifts in paired sightlines more often than expected for
sightline-independent redshifts. As the separation of the sightlines increases
from 36 kpc to 907 kpc, the amplitude of this clustering decreases. At the
largest separations, the CIV systems cluster similar to Lyman-break galaxies
(Adelberger et al. 2005a). The CIV systems are significantly less correlated
than these galaxies, however, at separations less than R_1 ~ 0.42 +/- 0.15 h-1
comoving Mpc. Measured in real space, i.e., transverse to the sightlines, this
length scale is significantly smaller than the break scale estimated from the
line-of-sight correlation function in redshift space (Scannapieco et al.
2006a). Using a simple model, we interpret the new real-space measurement as an
indication of the typical physical size of enriched regions. We adopt this size
for enriched regions and fit the redshift-space distortion in the line-of-sight
correlation function. The fitted velocity kick is consistent with the peculiar
velocity of galaxies as determined by the underlying mass distribution and
places an upper limit on the outflow (or inflow) speed of metals. The implied
time scale for dispersing metals is larger than the typical stellar ages of
Lyman-break galaxies (Shapley et al. 2001), and we argue that enrichment by
galaxies at z > 4.3 played a greater role in dispersing metals. To further
constrain the growth of enriched regions, we discuss empirical constraints on
the evolution of the CIV correlation function with cosmic time. This study
demonstrates the potential of tomography for measuring the metal enrichment
history of the circum-galactic medium.Comment: 22 pages, 15 figures, 1 tabl
The DEEP2 Galaxy Redshift Survey: Design, Observations, Data Reduction, and Redshifts
We describe the design and data sample from the DEEP2 Galaxy Redshift Survey,
the densest and largest precision-redshift survey of galaxies at z ~ 1
completed to date. The survey has conducted a comprehensive census of massive
galaxies, their properties, environments, and large-scale structure down to
absolute magnitude M_B = -20 at z ~ 1 via ~90 nights of observation on the
DEIMOS spectrograph at Keck Observatory. DEEP2 covers an area of 2.8 deg^2
divided into four separate fields, observed to a limiting apparent magnitude of
R_AB=24.1. Objects with z < 0.7 are rejected based on BRI photometry in three
of the four DEEP2 fields, allowing galaxies with z > 0.7 to be targeted ~2.5
times more efficiently than in a purely magnitude-limited sample. Approximately
sixty percent of eligible targets are chosen for spectroscopy, yielding nearly
53,000 spectra and more than 38,000 reliable redshift measurements. Most of the
targets which fail to yield secure redshifts are blue objects that lie beyond z
~ 1.45. The DEIMOS 1200-line/mm grating used for the survey delivers high
spectral resolution (R~6000), accurate and secure redshifts, and unique
internal kinematic information. Extensive ancillary data are available in the
DEEP2 fields, particularly in the Extended Groth Strip, which has evolved into
one of the richest multiwavelength regions on the sky. DEEP2 surpasses other
deep precision-redshift surveys at z ~ 1 in terms of galaxy numbers, redshift
accuracy, sample number density, and amount of spectral information. We also
provide an overview of the scientific highlights of the DEEP2 survey thus far.
This paper is intended as a handbook for users of the DEEP2 Data Release 4,
which includes all DEEP2 spectra and redshifts, as well as for the
publicly-available DEEP2 DEIMOS data reduction pipelines. [Abridged]Comment: submitted to ApJS; data products available for download at
http://deep.berkeley.edu/DR4
- âŠ