1,688 research outputs found
MUSTANG 3.3 Millimeter Continuum Observations of Class 0 Protostars
We present observations of six Class 0 protostars at 3.3 mm (90 GHz) using
the 64-pixel MUSTANG bolometer camera on the 100-m Green Bank Telescope. The
3.3 mm photometry is analyzed along with shorter wavelength observations to
derive spectral indices (S_nu ~ nu^alpha) of the measured emission. We utilize
previously published dust continuum radiative transfer models to estimate the
characteristic dust temperature within the central beam of our observations. We
present constraints on the millimeter dust opacity index, beta, between 0.862
mm, 1.25 mm, and 3.3 mm. Beta_mm typically ranges from 1.0 to 2.4 for Class 0
sources. The relative contributions from disk emission and envelope emission
are estimated at 3.3 mm. L483 is found to have negligible disk emission at 3.3
mm while L1527 is dominated by disk emission within the central beam. The
beta_mm^disk <= 0.8 - 1.4 for L1527 indicates that grain growth is likely
occurring in the disk. The photometry presented in this paper may be combined
with future interferometric observations of Class 0 envelopes and disks.Comment: 19 pages, 3 figures, AJ accepted, in pres
Observations of M87 and Hydra A at 90 GHz
This paper presents new observations of the AGNs M87 and Hydra A at 90 GHz
made with the MUSTANG bolometer array on the Green Bank Telescope at 8.5"
resolution. A spectral analysis is performed combining this new data and
archival VLA data on these objects at longer wavelengths. This analysis can
detect variations in spectral index and curvature expected from energy losses
in the radiating particles. M87 shows only weak evidence for steepening of the
spectrum along the jet suggesting either re-acceleration of the relativistic
particles in the jet or insufficient losses to affect the spectrum at 90 GHz.
The jets in Hydra A show strong steepening as they move from the nucleus
suggesting unbalanced losses of the higher energy relativistic particles. The
difference between these two sources may be accounted for by the different
lengths over which the jets are observable, 2 kpc for M87 and 45 kpc for Hydra
A.Comment: 11 pages, submitted to Ap
CMB observations with the Jodrell Bank - IAC interferometer at 33 GHz
The paper presents the first results obtained with the Jodrell Bank - IAC
two-element 33 GHz interferometer. The instrument was designed to measure the
level of the Cosmic Microwave Background (CMB) fluctuations at angular scales
of 1 - 2 degrees. The observations analyzed here were taken in a strip of the
sky at Dec = +41 deg with an element separation of 16.7 lambda, which gives a
maximum sensitivity to ~1.6 deg structures on the sky. The data processing and
calibration of the instrument are described. The sensitivity achieved in each
of the two channels is 7 micro K per resolution element. A reconstruction of
the sky at Dec = +41 deg using a maximum entropy method shows the presence of
structure at a high level of significance. A likelihood analysis, assuming a
flat CMB spatial power spectrum, gives a best estimate of the level of CMB
fluctuations of Delta Tl = 43 (+13,-12) micro K for the range l = 109 +/- 19;
the main uncertainty in this result arises from sample variance. We consider
that the contamination from the Galaxy is small. These results represent a new
determination of the CMB power spectrum on angular scales where previous
results show a large scatter; our new results are in agreement with the
theoretical predictions of the standard inflationary cold dark matter models.Comment: 11 pages, 11 figures. Web site at
http://www.jb.man.ac.uk/research/cmb/ Accepted for publication in MNRA
Dosimetric validation for an automatic brain metastases planning software using single-isocenter dynamic conformal arcsDosimetric validation for an automatic brain metastases planning software using single-isocenter dynamic conformal arcs.
An automatic brain-metastases planning (ABMP) software has been installed in our institution. It is dedicated for treating multiple brain metastases with radiosurgery on linear accelerators (linacs) using a single-setup isocenter with noncoplanar dynamic conformal arcs. This study is to validate the calculated absolute dose and dose distribution of ABMP. Three types of measurements were performed to validate the planning software: 1, dual micro ion chambers were used with an acrylic phantom to measure the absolute dose; 2, a 3D cylindrical phantom with dual diode array was used to evaluate 2D dose distribution and point dose for smaller targets; and 3, a 3D pseudo-in vivo patient-specific phantom filled with polymer gels was used to evaluate the accuracy of 3D dose distribution and radia-tion delivery. Micro chamber measurement of two targets (volumes of 1.2 cc and 0.9 cc, respectively) showed that the percentage differences of the absolute dose at both targets were less than 1%. Averaged GI passing rate of five different plans measured with the diode array phantom was above 98%, using criteria of 3% dose difference, 1 mm distance to agreement (DTA), and 10% low-dose threshold. 3D gel phantom measurement results demonstrated a 3D displacement of nine targets of 0.7 ± 0.4 mm (range 0.2 ~ 1.1 mm). The averaged two-dimensional (2D) GI passing rate for several region of interests (ROI) on axial slices that encompass each one of the nine targets was above 98% (5% dose difference, 2 mm DTA, and 10% low-dose threshold). Measured D95, the minimum dose that covers 95% of the target volume, of the nine targets was 0.7% less than the calculated D95. Three different types of dosimetric verification methods were used and proved the dose calculation of the new automatic brain metastases planning (ABMP) software was clinical acceptable. The 3D pseudo-in vivo patient-specific gel phantom test also served as an end-to-end test for validating not only the dose calculation, but the treatment delivery accuracy as well
Novel actions of next-generation taxanes benefit advanced stages of prostate cancer.
PURPOSE: To improve the outcomes of patients with castration-resistant prostate cancer (CRPC), there is an urgent need for more effective therapies and approaches that individualize specific treatments for patients with CRPC. These studies compared the novel taxane cabazitaxel with the previous generation docetaxel, and aimed to determine which tumors are most likely to respond.
EXPERIMENTAL DESIGN: Cabazitaxel and docetaxel were compared via in vitro modeling to determine the molecular mechanism, biochemical and cell biologic impact, and cell proliferation, which was further assessed ex vivo in human tumor explants. Isogenic pairs of RB knockdown and control cells were interrogated in vitro and in xenograft tumors for cabazitaxel response.
RESULTS: The data herein show that (i) cabazitaxel exerts stronger cytostatic and cytotoxic response compared with docetaxel, especially in CRPC; (ii) cabazitaxel induces aberrant mitosis, leading to pyknotic and multinucleated cells; (iii) taxanes do not act through the androgen receptor (AR); (iv) gene-expression profiling reveals distinct molecular actions for cabazitaxel; and (v) tumors that have progressed to castration resistance via loss of RB show enhanced sensitivity to cabazitaxel.
CONCLUSIONS: Cabazitaxel not only induces improved cytostatic and cytotoxic effects, but also affects distinct molecular pathways, compared with docetaxel, which could underlie its efficacy after docetaxel treatment has failed in patients with CRPC. Finally, RB is identified as the first potential biomarker that could define the therapeutic response to taxanes in metastatic CRPC. This would suggest that loss of RB function induces sensitization to taxanes, which could benefit up to 50% of CRPC cases
The Radio - 2 mm Spectral Index of the Crab Nebula Measured with GISMO
We present results of 2 mm observations of the Crab Nebula, obtained using
the Goddard-IRAM Superconducting 2 Millimeter Observer (GISMO) bolometer camera
on the IRAM 30 m telescope. Additional 3.3 mm observations with the MUSTANG
bolometer array on the Green Bank Telescope are also presented. The integrated
2 mm flux density of the Crab Nebula provides no evidence for the emergence of
a second synchrotron component that has been proposed. It is consistent with
the radio power law spectrum, extrapolated up to a break frequency of
log(nu_{b} [GHz]) = 2.84 +/- 0.29 or nu_{b} = 695^{+651}_{-336} GHz. The Crab
Nebula is well-resolved by the ~16.7" beam (FWHM) of GISMO. Comparison to radio
data at comparable spatial resolution enables us to confirm significant spatial
variation of the spectral index between 21 cm and 2 mm. The main effect is a
spectral flattening in the inner region of the Crab Nebula, correlated with the
toroidal structure at the center of the nebula that is prominent in the near-IR
through X-ray regime.Comment: Accepted for publication in the Ap
GMRF Estimation under Topological and Spectral Constraints
International audienceWe investigate the problem of Gaussian Markov random field selection under a non-analytic constraint: the estimated models must be compatible with a fast inference algorithm, namely the Gaussian belief propagation algorithm. To address this question, we introduce the *-IPS framework, based on iterative proportional scaling, which incrementally selects candidate links in a greedy manner. Besides its intrinsic sparsity-inducing ability, this algorithm is flexible enough to incorporate various spectral constraints, like e.g. walk summability, and topological constraints, like short loops avoidance. Experimental tests on various datasets, including traffic data from San Francisco Bay Area, indicate that this approach can deliver, with reasonable computational cost, a broad range of efficient inference models, which are not accessible through penalization with traditional sparsity-inducing norms
Gene Expression Profiles as Markers of Aggressive Disease-EGFR as a Factor
We previously reported that 43 (58%) of 75 head and neck squamous cell carcinoma (HNSCC) tumors harbor increased epidermal growth factor receptor (EGFR) gene copy numbers as determined by fluorescent in situ hybridization. In this study, an increased EGFR copy number was associated with decreased progression-free survival and overall survival of HNSCC patients. However, activated EGFR protein levels are difficult to quantify by immunohistochemistry and are subject to dynamic regulation, specifically receptor downregulation on ligand binding. Therefore, we generated an activated EGFR gene expression signature in an in vitro HaCaT keratinocyte model system to further study genes involved in the EGFR signaling pathway in HNSCC. The results from this model system have suggested that the activated EGFR signature might reflect the activated state of the EGFR pathway in human HNSCC tumors and that it is associated with the increased EGFR gene copy number by fluorescent in situ hybridization. Furthermore, the activated EGFR signature has provided additional leads, because they are related to co-regulated molecular pathways and associated gene products on activation of EGFR. These could be exploited to refine and optimize combination therapies to be used in conjunction with available EGFR inhibitors in individual HNSCC patients
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