650 research outputs found
Polarized galactic synchrotron and dust emission and their correlation
We present an analysis of the level of polarized dust and synchrotron
emission using the WMAP9 and Planck data. The primary goal of this study is to
inform the assessment of foreground contamination in the cosmic microwave
background (CMB) measurements below from 23 to 353 GHz. We
compute angular power spectra as a function of sky cut based on the Planck 353
GHz polarization maps. Our primary findings are the following. (1) There is a
spatial correlation between the dust emission as measured by Planck at 353 GHz
and the synchrotron emission as measured by WMAP at 23 GHz with
or greater for and ,
dropping to for . (2) A simple foreground model
with dust, synchrotron, and their correlation fits well to all possible cross
spectra formed with the WMAP and Planck 353 GHz data given the current
uncertainties. (3) In the 50 cleanest region of the polarized dust map, the
ratio of synchrotron to dust amplitudes at 90 GHz for 50 110 is
. Smaller regions of sky can be cleaner although the
uncertainties in our knowledge of synchrotron emission are larger. A
high-sensitivity measurement of synchrotron below 90 GHz will be important for
understanding all the components of foreground emission near 90 GHz.Comment: 10 pages, 8 figures; Published in JCAP. Source masks updated, minor
change
Estimating the Impact of foregrounds on the Future Detection of Rayleigh scattering
Rayleigh scattering of the cosmic microwave background (CMB) by neutral
hydrogen shortly after recombination leaves frequency-dependent imprints on
intensity and polarization fluctuations. High signal-to-noise observations of
CMB Rayleigh scattering would provide additional insight into the physics of
recombination, including greater constraining power for parameters like the
primordial helium fraction, the light relic density, and the sum of neutrino
masses. However, such a measurement of CMB Rayleigh scattering is challenging
due to the presence of astrophysical foregrounds, which are more intense at the
high frequencies, where the effects of Rayleigh scattering are most prominent.
Here we forecast the detectability of CMB Rayleigh scattering including
foreground removal using blind internal linear combination methods for a set of
near-future surveys. We show that atmospheric effects for ground-based
observatories and astrophysical foregrounds pose a significant hindrance to
detecting CMB Rayleigh scattering with experiments planned for this decade,
though a high-significance measurement should be possible with a future CMB
satellite.Comment: 14 pages, 12 figure
Interferon dimers: IFN-PEG-IFN
Increasingly complex proteins can be made by a recombinant chemical approach where proteins that can be made easily can be combined by site-specific chemical conjugation to form multifunctional or more active protein therapeutics. Protein dimers may display increased avidity for cell surface receptors. The increased size of protein dimers may also increase circulation times. Cytokines bind to cell surface receptors that dimerise, so much of the solvent accessible surface of a cytokine is involved in binding to its target. Interferon (IFN) homo-dimers (IFN-PEG-IFN) were prepared by two methods: site-specific bis-alkylation conjugation of PEG to the two thiols of a native disulphide or to two imidazoles on a histidine tag of two His8-tagged IFN (His8IFN). Several control conjugates were also prepared to assess the relative activity of these IFN homo-dimers. The His8IFN-PEG20-His8IFN obtained by histidine-specific conjugation displayed marginally greater in vitro antiviral activity compared to the IFN-PEG20-IFN homo-dimer obtained by disulphide re-bridging conjugation. This result is consistent with previous observations in which enhanced retention of activity was made possible by conjugation to an N-terminal His-tag on the IFN. Comparison of the antiviral and antiproliferative activities of the two IFN homo-dimers prepared by disulphide re-bridging conjugation indicated that IFN-PEG10-IFN was more biologically active than IFN-PEG20-IFN. This result suggests that the size of PEG may influence the antiviral activity of IFN-PEG-IFN homo-dimers
Breakthrough switching speed with an all-optical chalcogenide glass chip: 640 Gbit/s demultiplexing
We report the first demonstration of error-free 640 Gbit/s
demultiplexing using the Kerr non-linearity of an only 5 cm long
chalcogenide glass waveguide chip. Our approach exploits four-wave
mixing by the instantaneous nonlinear response of chalcogenide. Excellent
performance is achieved with only 2 dB average power penalty and no
indication of error-floor. Characterisation of the FWM efficiency for the
chalcogenide waveguide is given and confirms the good performance of the
device
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