2,382 research outputs found
The Alternative Appeal
For decades, Americans expressed dissatisfaction with conventional cancer treatments. I examine the appeal of biological alternatives to surgery, chemotherapy, and radiation therapy for patients with cancer. The limited effectiveness and side effects of many conventional cancer therapies led many patients to pursue a variety of unconventional therapies. To improve the quality of care for cancer patients, mainstream providers must better understand, and even collaborate with, alternative practitioners
The Alternative Appeal
For decades, Americans expressed dissatisfaction with conventional cancer treatments. I examine the appeal of biological alternatives to surgery, chemotherapy, and radiation therapy for patients with cancer. The limited effectiveness and side effects of many conventional cancer therapies led many patients to pursue a variety of unconventional therapies. To improve the quality of care for cancer patients, mainstream providers must better understand, and even collaborate with, alternative practitioners
On the Detection of Molecules in the Atmosphere of HD189733b using HST NICMOS Transmission Spectroscopy
The HST/NICMOS transmission spectrum measurements of HD 189733b that suggest
the detection of methane (CH) in an exoplanet atmosphere have been a
source of significant controversy. With what is probably the best analyzed
exoplanet spectroscopy data set to date, different teams, using different
methods, have claimed evidence both contradicting and supporting the original
findings. Here, we report results from a uniform spectral retrieval analysis of
the three, independent, published spectra together with null hypothesis
testing. Based on Bayesian model comparison, we find that two of the three
spectra show strong evidence ( 3.6) for the detection of
molecular features mainly due to water and methane while the third is
consistent with a weak molecular detection at the 2.2 level. We
interpret the agreement in the spectral modulation established by previous
authors and the atmospheric retrieval results presented here, as a confirmation
of the original detection of molecular absorbers in the atmosphere of HD
189733b.Comment: Accepted to Ap
Probing the terminator region atmosphere of the Hot-Jupiter XO-1b with transmission spectroscopy
We report here the first infrared spectrum of the hot-Jupiter XO-1b. The
observations were obtained with NICMOS instrument onboard the Hubble Space
Telescope during a primary eclipse of the XO-1 system. Near
photon-noise-limited spectroscopy between 1.2 and 1.8 micron allows us to
determine the main composition of this hot-Jupiter's planetary atmosphere with
good precision. This is the third hot-Jupiter's atmosphere for which
spectroscopic data are available in the near IR. The spectrum shows the
presence of water vapor (H2O), methane (CH4) and carbon dioxide (CO2), and
suggests the possible presence of carbon monoxide (CO). We show that the
published IRAC secondary transit emission photometric data are compatible with
the atmospheric composition at the terminator determined from the NICMOS
spectrum, with a range of possible mixing-ratios and thermal profiles;
additional emission spectroscopy data are needed to reduce the degeneracy of
the possible solutions. Finally, we note the similarity between the 1.2-1.8
micron transmission spectra of XO-1b and HD 209458b, suggesting that in
addition to having similar stellar/orbital and planetary parameters the two
systems may also have a similar exoplanetary atmospheric composition.Comment: ApJ accepted, 4 figure
Blind extraction of an exoplanetary spectrum through Independent Component Analysis
Blind-source separation techniques are used to extract the transmission
spectrum of the hot-Jupiter HD189733b recorded by the Hubble/NICMOS instrument.
Such a 'blind' analysis of the data is based on the concept of independent
component analysis. The de-trending of Hubble/NICMOS data using the sole
assumption that nongaussian systematic noise is statistically independent from
the desired light-curve signals is presented. By not assuming any prior, nor
auxiliary information but the data themselves, it is shown that spectroscopic
errors only about 10 - 30% larger than parametric methods can be obtained for
11 spectral bins with bin sizes of ~0.09 microns. This represents a reasonable
trade-off between a higher degree of objectivity for the non-parametric methods
and smaller standard errors for the parametric de-trending. Results are
discussed in the light of previous analyses published in the literature. The
fact that three very different analysis techniques yield comparable spectra is
a strong indication of the stability of these results.Comment: ApJ accepte
Molecular Signatures in the Near Infrared Dayside Spectrum of HD 189733b
We have measured the dayside spectrum of HD 189733b between 1.5 and 2.5
microns using the NICMOS instrument on the Hubble Space Telescope. The emergent
spectrum contains significant modulation, which we attribute to the presence of
molecular bands seen in absorption. We find that water (H2O), carbon monoxide
(CO), and carbon dioxide (CO2) are needed to explain the observations, and we
are able to estimate the mixing ratios for these molecules. We also find
temperature decreases with altitude in the ~0.01 < P < ~1 bar region of the
dayside near-infrared photosphere and set an upper limit to the dayside
abundance of methane (CH4) at these pressures.Comment: 13 pages, 3 figures. accepted in Astrophysical Journal Letter
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