687 research outputs found
Radio Astronomical Polarimetry and the Lorentz Group
In radio astronomy the polarimetric properties of radiation are often
modified during propagation and reception. Effects such as Faraday rotation,
receiver cross-talk, and differential amplification act to change the state of
polarized radiation. A general description of such transformations is useful
for the investigation of these effects and for the interpretation and
calibration of polarimetric observations. Such a description is provided by the
Lorentz group, which is intimately related to the transformation properties of
polarized radiation. In this paper the transformations that commonly arise in
radio astronomy are analyzed in the context of this group. This analysis is
then used to construct a model for the propagation and reception of radio
waves. The implications of this model for radio astronomical polarimetry are
discussed.Comment: 10 pages, accepted for publication in Astrophysical Journa
Spitzer View of Young Massive Stars in the LMC HII Complex N44
The HII complex N44 in the Large Magellanic Cloud (LMC) provides an excellent
site to perform a detailed study of star formation in a mild starburst, as it
hosts three regions of star formation at different evolutionary stages and it
is not as complicated and confusing as the 30 Doradus giant HII region. We have
obtained Spitzer Space Telescope observations and complementary ground-based 4m
uBVIJK observations of N44 to identify candidate massive young stellar objects
(YSOs). We further classify the YSOs into Types I, II, and III, according to
their spectral energy distributions (SEDs). In our sample of 60 YSO candidates,
~65% of them are resolved into multiple components or extended sources in
high-resolution ground-based images. We have modeled the SEDs of 36 YSOs that
appear single or dominant within a group. We find good fits for Types I and
I/II YSOs,but Types II and II/III YSOs show deviations between their observed
SEDs and models that do not include PAH emission. We have also found that some
Type III YSOs have central holes in their disk components. YSO counterparts are
found in four ultracompact HII regions and their stellar masses determined from
SED model fits agree well with those estimated from the ionization requirements
of the HII regions. The distribution of YSOs is compared with those of the
underlying stellar population and interstellar gas conditions to illustrate a
correlation between the current formation of O-type stars and previous
formation of massive stars. Evidence of triggered star formation is also
presented.Comment: 63 pages, 15 figures, accepted for publication for ApJ; some figures
in jpeg format to meet the size limit; preprint with high resolution images
can be found at http://www.astro.virginia.edu/~cc5ye/n44yso.pd
Disparities in routine breast cancer screening for medicaid managed care members with a work-limiting disability
Objective: Examine disparities in routine mammography for women who qualify for Medicaid, because of a work-limiting disability.
Methods: Individual-level data were obtained for women enrolled in Massachusetts Medicaid Managed Care plans who met the 2007 Healthcare Effectiveness Data and Information Set (HEDIS) criteria for the breast cancer screening measure (n=35,171). Disability status was determined from Medicaid eligibility records. Mammography screening was modeled using multivariate logistic regression. Separate models for women with and without a disability were also estimated.
Results: Although unadjusted breast cancer screening rates were roughly equal for women with and without disability, after adjusting for confounders disability status had a significant negative association with screening mammography (OR=0.74; p
Conclusion: Nationwide, rates of routine mammography for Medicaid managed care plans averaged below 50% in 2006. Given that a majority of eligible women served by Medicaid have disabilities, and studies have shown that women with disabilities are more likely to be diagnosed with late stage disease, a focus on improving rates of screening for women with disabilities is overdue
Anti-tubulin drugs conjugated to anti-ErbB antibodies selectively radiosensitize.
Tumour resistance to radiotherapy remains a barrier to improving cancer patient outcomes. To overcome radioresistance, certain drugs have been found to sensitize cells to ionizing radiation (IR). In theory, more potent radiosensitizing drugs should increase tumour kill and improve patient outcomes. In practice, clinical utility of potent radiosensitizing drugs is curtailed by off-target side effects. Here we report potent anti-tubulin drugs conjugated to anti-ErbB antibodies selectively radiosensitize to tumours based on surface receptor expression. While two classes of potent anti-tubulins, auristatins and maytansinoids, indiscriminately radiosensitize tumour cells, conjugating these potent anti-tubulins to anti-ErbB antibodies restrict their radiosensitizing capacity. Of translational significance, we report that a clinically used maytansinoid ADC, ado-trastuzumab emtansine (T-DM1), with IR prolongs tumour control in target expressing HER2+ tumours but not target negative tumours. In contrast to ErbB signal inhibition, our findings establish an alternative therapeutic paradigm for ErbB-based radiosensitization using antibodies to restrict radiosensitizer delivery
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BIOTIGER, A NATURAL MICROBIAL PRODUCT FOR ENHANCED HYDROCARBON RECOVERY FROM OIL SANDS.
BioTiger{trademark} is a unique microbial consortia that resulted from over 8 years of extensive microbiology screening and characterization of samples collected from a century-old Polish waste lagoon. BioTiger{trademark} shows rapid and complete degradation of aliphatic and aromatic hydrocarbons, produces novel surfactants, is tolerant of both chemical and metal toxicity and shows good activity at temperature and pH extremes. Although originally developed and used by the U.S. Department of Energy for bioremediation of oil-contaminated soils, recent efforts have proven that BioTiger{trademark} can also be used to increase hydrocarbon recovery from oil sands. This enhanced ex situ oil recovery process utilizes BioTiger{trademark} to optimize bitumen separation. A floatation test protocol with oil sands from Ft. McMurray, Canada was used for the BioTiger{trademark} evaluation. A comparison of hot water extraction/floatation test of the oil sands performed with BioTiger{trademark} demonstrated a 50% improvement in separation as measured by gravimetric analysis in 4 h and a five-fold increase at 25 hr. Since BioTiger{trademark} performs well at high temperatures and process engineering can enhance and sustain metabolic activity, it can be applied to enhance recovery of hydrocarbons from oil sands or other complex recalcitrant matrices
Triggered Star Formation and Dust around Mid-Infrared-Identified Bubbles
We use Two Micron All Sky Survey, GLIMPSE, and MIPSGAL survey data to analyze
the young stellar object (YSO) and warm dust distribution around several
mid-infrared-identified bubbles. We identify YSOs using J-band to 8 um
photometry and correlate their distribution relative to the PDR (as traced by
diffuse 8 um emission) which we assume to be associated with and surround a HII
region. We find that only 20% of the sample HII regions appear to have a
significant number of YSOs associated with their PDRs, implying that triggered
star formation mechanisms acting on the boundary of the expanding HII region do
not dominate in this sample. We also measure the temperature of dust inside 20
HII regions using 24 um and 70 um MIPSGAL images. In eight circularly symmetric
sources we analyze the temperature distribution and find shallower temperature
gradients than is predicted by an analytic model. Possible explanations of this
shallow temperature gradient are a radially dependent grain-size distribution
and/or non-equilibrium radiative processes.Comment: 35 pages, 17 figures, accepted for publication in Ap
Spitzer View of Young Massive Stars in the LMC HII Complexes. II. N159
The HII complex N159 in the Large Magellanic Cloud (LMC) is used to study
massive star formation in different environments, as it contains three giant
molecular clouds (GMCs) that have similar sizes and masses but exhibit
different intensities of star formation. We identify candidate massive young
stellar objects (YSOs) using infrared photometry, and model their SEDs to
constrain mass and evolutionary state. Good fits are obtained for less evolved
Type I, I/II, and II sources. Our analysis suggests that there are massive
embedded YSOs in N159B, a maser source, and several ultracompact HII regions.
Massive O-type YSOs are found in GMCs N159-E and N159-W, which are associated
with ionized gas, i.e., where massive stars formed a few Myr ago. The third
GMC, N159-S, has neither O-type YSOs nor evidence of previous massive star
formation. This correlation between current and antecedent formation of massive
stars suggests that energy feedback is relevant. We present evidence that
N159-W is forming YSOs spontaneously, while collapse in N159-E may be
triggered. Finally, we compare star formation rates determined from YSO counts
with those from integrated H-alpha and 24 micron luminosities and expected from
gas surface densities. Detailed dissection of extragalactic GMCs like the one
presented here is key to revealing the physics underlying commonly used star
formation scaling laws.Comment: 60 pages, 11 figures. Accepted for publication in Astrophysical
Journa
The association of polymorphism rs3736228 within the LRP5 gene with Bone Mineral Density in a Cohort of Caucasian Young Adults
INTRODUCTION: Osteoporosis is a significant burden for our aging population. Developing a better understanding of the genetic underpinnings of poor bone quality may assist in the future development of prevention strategies. Correa-Rodriguez et al. have identified a group of single nucleotide polymorphisms (SNPs) that were associated with bone mineral density (BMD) in a population of Spanish Caucasians. In particular, they found that SNP rs3736228 in the low-density lipoprotein receptor related protein 5 (LRP5) gene had an influence on BMD. While the role of LRP5 in the Wnt canonical pathway has been fairly well characterized, its association with phenotypic BMD and osteoporosis has only been explored in a limited fashion. The aim of this study is to expand on this, and to replicate the findings of previous studies in a cohort of healthy young adults.
METHODS: Cohort: The University of Calgary cohort from the Assessing Inherited Metabolic Syndrome Markers in the Young (UC AIMMY) study. Participants included consist of 168 healthy, predominantly Caucasian young adults. Phenotypes: height, weight, BMI, and total BMD. Genotyping: Allelic discrimination was determined. Statistical Analysis: After being tested for Hardy-Weinberg equilibrium (HWE), the data was run through analysis of covariance (ANCOVA).
RESULTS: Using a dominant model, we found that females with one or more copies of the risk T allele of SNP rs3736228 had a significant negative association with total BMD (p = 0.0347). However, a similar association was not seen in males in this cohort. We did not find a significant association for this polymorphism and height, weight, or BMI.
DISCUSSION: Polymorphisms in rs3736228 alter the codon in position 1330, downregulating the LRP5 cell surface receptor function. The LRP5 gene has now been shown in multiple studies to be associated with bone quality measures like calcaneal Qualitative Ultrasound (QUS) and BMD. Our study suggests that SNP rs3736228 also influences BMD in healthy young females. This supports the work of Correa-Rodriguez et al that found that when stratifying by sex, females only showed a trend towards significance (p = 0.092) in QUS measures.
SIGNIFICANCE: This study expands our understanding of the importance of LRP5 rs3736228 polymorphisms in BMD by extending its relationship to a cohort of predominantly Caucasian college students. While the development of BMD is polygenic, this work broadened the role of SNP rs3736228 across the age span, and the sexual dimorphism seen in musculoskeletal traits
A multi-wavelength study of the young star V1118 Orionis in outburst
Abriged version for astroph: The young late-type star V1118 Orionis was in
outburst from 2005 to 2006. We followed the outburst with optical and
near-infrared photometry; the X-ray emission was further probed with
observations taken with XMM-Newton and Chandra during and after the outburst.
In addition, we obtained mid-infrared photometry and spectroscopy with Spitzer
at the peak of the outburst and in the post-outburst phase. The spectral energy
distribution of V1118 Ori varied significantly over the course of the outburst.
The optical flux showed the largest variations, most likely due to enhanced
emission by a hot spot. The latter dominated the optical and near-infrared
emission at the peak of the outburst, while the disk emission dominated in the
mid-infrared. The X-ray flux correlated with the optical and infrared fluxes,
indicating that accretion affected the magnetically active corona and the
stellar magnetosphere. The thermal structure of the corona was variable with
some indication of a cooling of the coronal temperature in the early phase of
the outburst with a gradual return to normal values. Color-color diagrams in
the optical and infrared showed variations during the outburst, with no obvious
signature of reddening due to circumstellar matter. Using MC realizations of
star+disk+hotspot models to fit the SED in ``quiescence'' and at the peak of
the outburst, we determined that the mass accretion rate varied from about
2.5E-7 Msun/yr to 1E-6 Msun/yr; in addition the fractional area of the hotspot
increased significantly as well. The multi-wavelength study of the V1118 Ori
outburst helped us to understand the variations in spectral energy
distributions and demonstrated the interplay between the disk and the stellar
magnetosphere in a young, strongly accreting star.Comment: Accepted in A&A, Tables will be published onlin
Factors Affecting the Pharmacokinetics and Pharmacodynamics of PEGylated Liposomal Irinotecan (IHL-305) in Patients with Advanced Solid Tumors
IHL-305 is a PEGylated liposomal formulation of irinotecan (CPT-11). The objective of this study was to evaluate the factors associated with interpatient variability in the pharmacokinetics and pharmacodynamics of IHL-305 in patients with advanced solid tumors. IHL-305 was administered intravenously once every 4 weeks as part of a Phase I study. Pharmacokinetic studies of the liposomal sum total CPT-11, released CPT-11, SN-38, SN-38G, 7-ethyl-10-[4-N-(5-aminopentanoic acid)-1-piperidino]-carbonyloxycamptothecin, and 7-ethyl-10-[4-amino-1-piperidino]-carbonyloxycamptothecin in plasma were performed. Noncompartmental and compartmental pharmacokinetic analyses were conducted using pharmacokinetic data for sum total CPT-11. The pharmacokinetic variability of IHL-305 is associated with linear and nonlinear clearance. Patients whose age and body composition (ratio of total body weight to ideal body weight [TBW/IBW]) were greater than the median age and TBW/IBW of the study had a 1.7-fold to 2.6-fold higher ratio of released CPT-11 area under the concentration versus time curve (AUC) to sum total CPT-11 AUC. Patients aged \u3c60 years had a 1.3-fold higher ratio of percent decrease in monocytes at nadir to percent decrease in absolute neutrophil count at nadir as compared with patients aged ≥60 years. There was an inverse relationship between patient age and percent decrease in monocytes at nadir, ie, younger patients have a higher percent decrease in monocytes. Patients with a higher percent decrease in monocytes at nadir have a decreased plasma exposure of sum total CPT-11. The pharmacokinetics and pharmacodynamics of IHL-305 are consistent with those of other PEGylated liposomal carriers. Interpatient variability in the pharmacokinetics and pharmacodynamics of IHL-305 was associated with age, body composition, and monocytes
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