4,356 research outputs found
SuperLupus: A Deep, Long Duration Transit Survey
SuperLupus is a deep transit survey monitoring a Galactic Plane field in the
Southern hemisphere. The project is building on the successful Lupus Survey,
and will double the number of images of the field from 1700 to 3400, making it
one of the longest duration deep transit surveys. The immediate motivation for
this expansion is to search for longer period transiting planets (5-8 days) and
smaller radii planets. It will also provide near complete recovery for the
shorter period planets (1-3 days). In March, April, and May 2008 we obtained
the new images and work is currently in progress reducing these new data.Comment: 3 pages, 2 figures, to appear in the Proceedings of IAU Symposium
253, 2008: Transiting Planet
Bone marrow transplantation alters the tremor phenotype in the murine model of globoid-cell leukodystrophy
Tremor is a prominent phenotype of the twitcher mouse, an authentic genetic model of Globoid-Cell Leukodystrophy (GLD, Krabbe’s disease). In the current study, the tremor was quantified using a force-plate actometer designed to accommodate low-weight mice. The actometer records the force oscillations caused by a mouse’s movements, and the rhythmic structure of the force variations can be revealed. Results showed that twitcher mice had significantly increased power across a broad band of higher frequencies compared to wildtype mice. Bone marrow transplantation (BMT), the only available therapy for GLD, worsened the tremor in the twitcher mice and induced a measureable alteration of movement phenotype in the wildtype mice. These data highlight the damaging effects of conditioning radiation and BMT in the neonatal period. The behavioral methodology used herein provides a quantitative approach for assessing the efficacy of potential therapeutic interventions for Krabbe’s disease
Lupus-TR-3b: A Low-Mass Transiting Hot Jupiter in the Galactic Plane?
We present a strong case for a transiting Hot Jupiter planet identified
during a single-field transit survey towards the Lupus Galactic plane. The
object, Lupus-TR-3b, transits a V=17.4 K1V host star every 3.91405d.
Spectroscopy and stellar colors indicate a host star with effective temperature
5000 +/- 150K, with a stellar mass and radius of 0.87 +/- 0.04M_sun and 0.82
+/- 0.05R_sun, respectively. Limb-darkened transit fitting yields a companion
radius of 0.89 +/- 0.07R_J and an orbital inclination of 88.3 +1.3/-0.8 deg.
Magellan 6.5m MIKE radial velocity measurements reveal a 2.4 sigma K=114 +/-
25m/s sinusoidal variation in phase with the transit ephemeris. The resulting
mass is 0.81 +/- 0.18M_J and density 1.4 +/- 0.4g/cm^3. Y-band PANIC image
deconvolution reveal a V>=21 red neighbor 0.4'' away which, although highly
unlikely, we cannot conclusively rule out as a blended binary with current
data. However, blend simulations show that only the most unusual binary system
can reproduce our observations. This object is very likely a planet, detected
from a highly efficient observational strategy. Lupus-TR-3b constitutes the
faintest ground-based detection to date, and one of the lowest mass Hot
Jupiters known.Comment: 4 pages, 4 figures, accepted for publication in ApJ
Characterizing Bars at z~0 in the optical and NIR: Implications for the Evolution of Barred Disks with Redshift
Critical insights on galaxy evolution stem from the study of bars. With the
advent of HST surveys that trace bars in the rest-frame optical out to z~1, it
is critical to provide a reference baseline for bars at z~0 in the optical
band. We present results on bars at z~0 in the optical and NIR bands based on
180 spirals from OSUBSGS. (1) The deprojected bar fraction at z~0 is ~60% +/-6%
in the NIR H-band and ~44% +/-6% in the optical B-band. (2) The results before
and after deprojection are similar, which is encouraging for high-redshift
studies that forego deprojection. (3) Studies of bars at z~0.2-1.0 (lookback
time of 3-8 Gyr) have reported an optical bar fraction of ~30% +/-6%, after
applying cutoffs in absolute magnitude (M_V = 1.5
kpc), and bar ellipticity (e_bar >= 0.4). Applying these exact cutoffs to the
OSUBSGS data yields a comparable optical B-band bar fraction at z~0 of ~
34%+/-6%. This rules out scenarios where the optical bar fraction in bright
disks declines strongly with redshift. (4) Most (~70%) bars have moderate to
high strentgh or ellipticity (0.50 <= e_bar <= 0.75). There is no bimodality in
the distribution of e_bar. The H-band bar fraction and e_bar show no
substantial variation across RC3 Hubble types Sa to Scd. (5) RC3 bar types
should be used with caution. Many galaxies with RC3 types "AB" turn out to be
unbarred and RC3 bar classes "B" and "AB" have a significant overlap in e_bar.
(6) Most bars have sizes below 5 kpc. Bar and disk sizes correlate, and most
bars have a_bar/R_25~0.1-0.5. This suggests that the growths of bars and disks
are intimately tied.Comment: 11 pages, 17 figures, 3 tables, ApJ accepted, abridged abstract
below. Minor changes and shortened paper for ApJ limits. For high resolution
figures see http://www.as.utexas.edu/~marinova/paper1-highres.pd
Limits on I-band microvariability of the Galactic Bulge Miras
We search for microvariability in a sample of 485 Mira variables with high
quality I-band light curves from the second generation Optical Gravitational
Lensing Experiment (OGLE-II). Rapid variations with amplitudes in the ~0.2-1.1
mag range lasting hours to days were discovered in Hipparcos data by de Laverny
et al. (1998). Our search is primarily sensitive to events with time-scales of
about 1 day, but retains a few percent efficiency (per object) for detecting
unresolved microvariability events as short as 2 hours. We do not detect any
candidate events. Assuming that the distribution of the event time profiles is
identical to that from the Hipparcos light curves we derive the 95% confidence
level upper limit of 0.038 per year per star for the rate of such events (1 per
26 years per average object of the ensemble). The high event rates of the order
of 1 per year per star implied by the Hipparcos study in the H_P band are
excluded with high confidence by the OGLE-II data in the I band. Our
non-detection could still be explained by much redder spectral response of the
I filter compared to the H_P band or by population differences between the
bulge and the solar neighborhood. In any case, the OGLE-II I-band data provide
the first limit on the rate of the postulated microvariability events in Mira
stars and offer new quantitative constraints on their properties. Similar
limits are obtained for other pulse shapes and a range of the assumed
time-scales and size-frequency distributions.Comment: Accepted for publication in Ap
Behavioral Consequences of NMDA Antagonist-Induced Neuroapoptosis in the Infant Mouse Brain
Background: Exposure to NMDA glutamate antagonists during the brain growth spurt period causes widespread neuroapoptosis in the rodent brain. This period in rodents occurs during the first two weeks after birth, and corresponds to the third trimester of pregnancy and several years after birth in humans. The developing human brain may be exposed to NMDA antagonists through drug-abusing mothers or through anesthesia. Methodology/Principal Findings: We evaluated the long-term neurobehavioral effects of mice exposed to a single dose of the NMDA antagonist, phencyclidine (PCP), or saline, on postnatal day 2 (P2) or P7, or on both P2 and P7. PCP treatment on P2 + P7 caused more severe cognitive impairments than either single treatment. Histological examination of acute neuroapoptosis resulting from exposure to PCP indicated that the regional pattern of degeneration induced by PCP in P2 pups was different from that in P7 pups. The extent of damage when evaluated quantitatively on P7 was greater for pups previously treated on P2 compared to pups treated only on P7. Conclusions: These findings signify that PCP induces different patterns of neuroapoptosis depending on the developmental age at the time of exposure, and that exposure at two separate developmental ages causes more severe neuropathological and neurobehavioral consequences than a single treatment
Integral-field spectroscopy of the quadruple QSO HE 0435-1223: Evidence for microlensing
We present the first spatially resolved spectroscopic observations of the
recently discovered quadruple QSO and gravitational lens HE0435-1223. Using the
Potsdam Multi-Aperture Spectrophotometer (PMAS), we show that all four QSO
components have very similar but not identical spectra. In particular, the
spectral slopes of components A, B, and D are indistinguishable, implying that
extinction due to dust plays no major role in the lensing galaxy. While also
the emission line profiles are identical within the error bars, as expected
from lensing, the equivalent widths show significant differences between
components. Most likely, microlensing is responsible for this phenomenon. This
is also consistent with the fact that component D, which shows the highest
relative continuum level, has brightened by 0.07 mag since Dec 2001. We find
that the emission line flux ratios between the components are in better
agreement with simple lens models than broad band or continuum measurements,
but that the discrepancies between model and data are still unacceptably large.
Finally, we present a detection of the lensing galaxy, although this is close
to the limits of the data. Comparing with a model galaxy spectrum, we obtain a
redshift estimate of z_lens=0.44+-0.02.Comment: 9 pages, 7 figures, accepted for publication in A&
Expression of nampt in hippocampal and cortical excitatory neurons is critical for cognitive function
Nicotinamide adenine dinucleotide (NAD(+)) is an enzyme cofactor or cosubstrate in many essential biological pathways. To date, the primary source of neuronal NAD(+) has been unclear. NAD(+) can be synthesized from several different precursors, among which nicotinamide is the substrate predominantly used in mammals. The rate-limiting step in the NAD(+) biosynthetic pathway from nicotinamide is performed by nicotinamide phosphoribosyltransferase (Nampt). Here, we tested the hypothesis that neurons use intracellular Nampt-mediated NAD(+) biosynthesis by generating and evaluating mice lacking Nampt in forebrain excitatory neurons (CaMKIIαNampt(−/−) mice). CaMKIIαNampt(−/−) mice showed hippocampal and cortical atrophy, astrogliosis, microgliosis, and abnormal CA1 dendritic morphology by 2–3 months of age. Importantly, these histological changes occurred with altered intrahippocampal connectivity and abnormal behavior; including hyperactivity, some defects in motor skills, memory impairment, and reduced anxiety, but in the absence of impaired sensory processes or long-term potentiation of the Schaffer collateral pathway. These results clearly demonstrate that forebrain excitatory neurons mainly use intracellular Nampt-mediated NAD(+) biosynthesis to mediate their survival and function. Studying this particular NAD(+) biosynthetic pathway in these neurons provides critical insight into their vulnerability to pathophysiological stimuli and the development of therapeutic and preventive interventions for their preservation
The Influence of Bars on Nuclear Activity
We test ideas on fueling of galactic nuclei by bar-driven inflow by comparing
the detection rate and intensity of nuclear H II regions and AGNs among barred
and unbarred galaxies in a sample of over 300 spirals selected from our recent
optical spectroscopic survey of nearby galaxies. Among late-type spirals
(Sc-Sm), but not early-type (S0/a-Sbc), we observe in the barred group a very
marginal increase in the detection rate of H II nuclei and a corresponding
decrease in the incidence of AGNs. The minor differences in the detection
rates, however, are statistically insignificant, most likely stemming from
selection effects and not from a genuine influence from the bar. The presence
of a bar seems to have no noticeable impact on the likelihood of a galaxy to
host either nuclear star formation or an AGN. The nuclei of early-type barred
spirals do exhibit measurably higher star-formation rates than their unbarred
counterparts, as indicated by either the luminosity or the equivalent width of
H-alpha emission. By contrast, late-type spirals do not show such an effect.
Bars have a negligible effect on the strength of the AGNs in our sample,
regardless of the Hubble type of the host galaxy. This result confirms similar
conclusions reached by other studies based on much smaller samples.Comment: To appear in the Astrophysical Journal. LaTex, 31 pages including 6
postscript figures and 3 tables. AAStex macros include
Comprehensive functional characterization of murine infantile Batten disease including Parkinson-like behavior and dopaminergic markers
Infantile neuronal ceroid lipofuscinosis (INCL, Infantile Batten disease) is a neurodegenerative lysosomal storage disease caused by a deficiency in palmitoyl protein thioesterase-1 (PPT1). The PPT1-deficient mouse (Cln1−/−) is a useful phenocopy of human INCL. Cln1−/− mice display retinal dysfunction, seizures, motor deficits, and die at ~8 months of age. However, little is known about the cognitive and behavioral functions of Cln1−/− mice during disease progression. In the present study, younger (~1–2 months of age) Cln1−/− mice showed minor deficits in motor/sensorimotor functions while older (~5–6 months of age) Cln1−/− mice exhibited more severe impairments, including decreased locomotor activity, inferior cued water maze performance, decreased running wheel ability, and altered auditory cue conditioning. Unexpectedly, certain cognitive functions such as some learning and memory capabilities seemed intact in older Cln1−/− mice. Younger and older Cln1−/− mice presented with walking initiation defects, gait abnormalities, and slowed movements, which are analogous to some symptoms reported in INCL and parkinsonism. However, there was no evidence of alterations in dopaminergic markers in Cln1−/− mice. Results from this study demonstrate quantifiable changes in behavioral functions during progression of murine INCL and suggest that Parkinson-like motor/sensorimotor deficits in Cln1−/− mice are not mediated by dopamine deficiency
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