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Time-course of effects of external beam radiation on [18F]FDG uptake in healthy tissue and bone marrow.
The utility of PET for monitoring responses to radiation therapy have been complicated by metabolically active processes in surrounding normal tissues. We examined the time-course of [18F]FDG uptake in normal tissues using small animal-dedicated PET during the 2 month period following external beam radiation. Four mice received 12 Gy of external beam radiation, in a single fraction to the left half of the body. Small animal [18F]FDG-PET scans were acquired for each mouse at 0 (pre-radiation), 1, 2, 3, 4, 5, 8, 12, 19, 24, and 38 days following irradiation. [18F]FDG activity in various tissues was compared between irradiated and non-irradiated body halves before, and at each time point after irradiation. Radiation had a significant impact on [18F]FDG uptake in previously healthy tissues, and time-course of effects differed in different types of tissues. For example, liver tissue demonstrated increased uptake, particularly over days 3-12, with the mean left to right uptake ratio increasing 52% over mean baseline values (p < 0.0001). In contrast, femoral bone marrow uptake demonstrated decreased uptake, particularly over days 2-8, with the mean left to right uptake ratio decreasing 26% below mean baseline values (p = 0.0005). Significant effects were also seen in lung and brain tissue. Radiation had diverse effects on [18F]FDG uptake in previously healthy tissues. These kinds of data may help lay groundwork for a systematically acquired database of the time-course of effects of radiation on healthy tissues, useful for animal models of cancer therapy imminently, as well as interspecies extrapolations pertinent to clinical application eventually
A Monte Carlo based phase space model for quality assurance of intensity modulated radiotherapy incorporating leaf specific characteristics
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134797/1/mp3409.pd
Resonance superfluidity in a quantum degenerate Fermi gas
We consider the superfluid phase transition that arises when a Feshbach
resonance pairing occurs in a dilute Fermi gas. We apply our theory to consider
a specific resonance in potassium-40, and find that for achievable experimental
conditions, the transition to a superfluid phase is possible at the high
critical temperature of about 0.5 T_F. Observation of superfluidity in this
regime would provide the opportunity to experimentally study the crossover from
the superfluid phase of weakly-coupled fermions to the Bose-Einstein
condensation of strongly-bound composite bosons.Comment: 4 pages, 3 figure
Clusters at Half Hubble Time: Galaxy Structure and Colors in RXJ0152.7-1357 and MS1054-03
We study the photometric and structural properties of spectroscopically
confirmed members in the two massive X-ray--selected z=0.83 galaxy clusters
MS1054-03 and RXJ0152-1357 using three-band mosaic imaging with the Hubble
Space Telescope Advanced Camera for Surveys. The samples include 105 and 140
members of MS1054-03 and RXJ0152-1357, respectively, with ACS F775W magnitude <
24.0. We develop a promising new structural classification method, based on a
combination of the best-fit Sersic indices and the normalized root-mean-square
residuals from the fits; the resulting classes agree well with the visual ones,
but are less affected by galaxy orientation. We examine the color--magnitude
relations in detail and find that the color residuals correlate with the local
mass density measured from our weak lensing maps; we identify a threshold
density of , in units of the critical density, above which
the star formation appears to cease. For RXJ0152-1357, we also find a trend in
the color residuals with velocity, resulting from an offset of about 980 km/s
in the mean redshifts of the early- and late-type galaxies. Analysis of the
color--color diagrams indicates that a range of star formation time-scales are
needed to reproduce the loci of the galaxy colors. We also identify some
cluster galaxies whose colors can only be explained by large amounts, mag, of internal dust extinction. [Abstract shortened]Comment: 30 pages, emulateapj format; 23 figures, many in color. Accepted by
ApJ; scheduled for the 10 June 2006 issue. Some figures degraded; for a
higher resolution version, see: http://astro.wsu.edu/blakeslee/z1clusters
Signatures of resonance superfluidity in a quantum Fermi gas
In this letter, we predict a direct and observable signature of the
superfluid phase in a quantum Fermi gas, in a temperature regime already
accessible in current experiments. We apply the theory of resonance
superfluidity to a gas confined in a harmonic potential and demonstrate that a
significant increase in density will be observed in the vicinity of the trap
center.Comment: 4 pages, 4 figure
Creation of ultracold molecules from a Fermi gas of atoms
Since the realization of Bose-Einstein condensates (BEC) in atomic gases an
experimental challenge has been the production of molecular gases in the
quantum regime. A promising approach is to create the molecular gas directly
from an ultracold atomic gas; for example, atoms in a BEC have been coupled to
electronic ground-state molecules through photoassociation as well as through a
magnetic-field Feshbach resonance. The availability of atomic Fermi gases
provides the exciting prospect of coupling fermionic atoms to bosonic
molecules, and thus altering the quantum statistics of the system. This
Fermi-Bose coupling is closely related to the pairing mechanism for a novel
fermionic superfluid proposed to occur near a Feshbach resonance. Here we
report the creation and quantitative characterization of exotic, ultracold
K molecules. Starting with a quantum degenerate Fermi gas of atoms
at T < 150 nanoKelvin we scan over a Feshbach resonance to adiabatically create
over a quarter million trapped molecules, which we can convert back to atoms by
reversing the scan. The small binding energy of the molecules is controlled by
detuning from the Feshbach resonance and can be varied over a wide range. We
directly detect these weakly bound molecules through rf photodissociation
spectra that probe the molecular wavefunction and yield binding energies that
are consistent with theory
Evolution of the Color-Magnitude Relation in Galaxy Clusters at z ~1 from the ACS Intermediate Redshift Cluster Survey
We apply detailed observations of the Color-Magnitude Relation (CMR) with the
ACS/HST to study galaxy evolution in eight clusters at z~1. The early-type red
sequence is well defined and elliptical and lenticular galaxies lie on similar
CMRs. We analyze CMR parameters as a function of redshift, galaxy properties
and cluster mass. For bright galaxies (M_B < -21mag), the CMR scatter of the
elliptical population in cluster cores is smaller than that of the S0
population, although the two become similar at faint magnitudes. While the
bright S0 population consistently shows larger scatter than the ellipticals,
the scatter of the latter increases in the peripheral cluster regions. If we
interpret these results as due to age differences, bright elliptical galaxies
in cluster cores are on average older than S0 galaxies and peripheral
elliptical galaxies (by about 0.5Gyr). CMR zero point, slope, and scatter in
the (U-B)_z=0 rest-frame show no significant evolution out to redshift z~1.3
nor significant dependence on cluster mass. Two of our clusters display CMR
zero points that are redder (by ~2sigma) than the average (U-B)_z=0 of our
sample. We also analyze the fraction of morphological early-type and late-type
galaxies on the red sequence. We find that, while in the majority of the
clusters most (80% to 90%) of the CMR population is composed of early-type
galaxies, in the highest redshift, low mass cluster of our sample, the CMR
late-type/early-type fractions are similar (~50%), with most of the late-type
population composed of galaxies classified as S0/a. This trend is not
correlated with the cluster's X-ray luminosity, nor with its velocity
dispersion, and could be a real evolution with redshift.Comment: ApJ, in press, 27 pages, 22 figure
Irradiation of the potential cancer stem cell niches in the adult brain improves progression-free survival of patients with malignant glioma
<p>Abstract</p> <p>Background</p> <p>Glioblastoma is the most common brain tumor in adults. The mechanisms leading to glioblastoma are not well understood but animal studies support that inactivation of tumor suppressor genes in neural stem cells (NSC) is required and sufficient to induce glial cancers. This suggests that the NSC niches in the brain may harbor cancer stem cells (CSCs), Thus providing novel therapy targets. We hypothesize that higher radiation doses to these NSC niches improve patient survival by eradicating CSCs.</p> <p>Methods</p> <p>55 adult patients with Grade 3 or Grade 4 glial cancer treated with radiotherapy at UCLA between February of 2003 and May of 2009 were included in this retrospective study. Using radiation planning software and patient radiological records, the SVZ and SGL were reconstructed for each of these patients and dosimetry data for these structures was calculated.</p> <p>Results</p> <p>Using Kaplan-Meier analysis we show that patients whose bilateral subventricular zone (SVZ) received greater than the median SVZ dose (= 43 Gy) had a significant improvement in progression-free survival if compared to patients who received less than the median dose (15.0 vs 7.2 months PFS; P = 0.028). Furthermore, a mean dose >43 Gy to the bilateral SVZ yielded a hazard ratio of 0.73 (P = 0.019). Importantly, similarly analyzing total prescription dose failed to illustrate a statistically significant impact.</p> <p>Conclusions</p> <p>Our study leads us to hypothesize that in glioma targeted radiotherapy of the stem cell niches in the adult brain could yield significant benefits over radiotherapy of the primary tumor mass alone and that damage caused by smaller fractions of radiation maybe less efficiently detected by the DNA repair mechanisms in CSCs.</p
Early assembly of the most massive galaxies
The current consensus is that galaxies begin as small density fluctuations in
the early Universe and grow by in situ star formation and hierarchical merging.
Stars begin to form relatively quickly in sub-galactic sized building blocks
called haloes which are subsequently assembled into galaxies. However, exactly
when this assembly takes place is a matter of some debate. Here we report that
the stellar masses of brightest cluster galaxies, which are the most luminous
objects emitting stellar light, some 9 billion years ago are not significantly
different from their stellar masses today. Brightest cluster galaxies are
almost fully assembled 4-5 Gyrs after the Big Bang, having grown to more than
90% of their final stellar mass by this time. Our data conflict with the most
recent galaxy formation models based on the largest simulations of dark matter
halo development. These models predict protracted formation of brightest
cluster galaxies over a Hubble time, with only 22% of the stellar mass
assembled at the epoch probed by our sample. Our findings suggest a new picture
in which brightest cluster galaxies experience an early period of rapid growth
rather than prolonged hierarchical assembly.Comment: Published in Nature 2nd April 2009. This astro ph version includes
main text and supplementary material combine
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