1,149 research outputs found
Fundamental Performance of a Dispersed Fixed Delay Interferometer In Searching For Planets Around M Dwarfs
We present a new method to calculate fundamental Doppler measurement limits
with a dispersed fixed-delay interferometer (DFDI) in the near infrared
wavelength region for searching for exoplanets around M dwarfs in the coming
decade. It is based on calculating the Q factor, a measure of flux-normalized
Doppler sensitivity in the fringing spectra created with DFDI. We calculate the
Q factor as a function of spectral resolution R, stellar projected rotational
velocity V sini, stellar effective temperature T_eff and optical path
difference (OPD) of the interferometer. We also compare the DFDI Q factor to
that for the popular cross-dispersed echelle spectrograph method (the direct
echelle (DE) method). Given the IR Doppler measurement is likely to be
detector-limited for a while, we introduce new merit functions, which is
directly related to photon-limited RV uncertainty, to evaluate Doppler
performance with the DFDI and DE methods. We find that DFDI has strength in
wavelength coverage and multi-object capability over the DE for a limited
detector resource. We simulate the performance of the InfraRed Exoplanet
Tracker (IRET) based on the DFDI design, being considered for the next
generation IR Doppler measurements. The predicted photon-limited RV uncertainty
suggests that IRET is capable of detecting Earth-like exoplanets in habitable
zone around nearby bright M dwarfs if they exist. A new method is developed to
quantitatively estimate the influence of telluric lines on RV uncertainty. Our
study shows that photon-limited RV uncertainty can be reached if 99% of the
strength of telluric lines can be removed from the measured stellar spectra. At
low to moderate levels of telluric line strength removal (50% to 90%), the
optimal RV uncertainty is typically a factor of 2-3 times larger than
photon-limited RV uncertainty.Comment: 43 pages, 20 figures, 6 tables. Accepted by Ap
High Cycle Fatigue Properties of the Zr-Modified Al–Si–Cu–Mg Alloy at Elevated Temperatures
Jaguar Range Rover (JLR) [grant number R33232
Bilaterally Combined Electric and Acoustic Hearing in Mandarin-Speaking Listeners: The Population With Poor Residual Hearing
The hearing loss criterion for cochlear implant candidacy in mainland China is extremely stringent (bilateral severe to
profound hearing loss), resulting in few patients with substantial residual hearing in the nonimplanted ear. The main objective
of the current study was to examine the benefit of bimodal hearing in typical Mandarin-speaking implant users who have
poorer residual hearing in the nonimplanted ear relative to those used in the English-speaking studies. Seventeen Mandarinspeaking bimodal users with pure-tone averages of 80 dB HL participated in the study. Sentence recognition in quiet and in
noise as well as tone and word recognition in quiet were measured in monaural and bilateral conditions. There was no
significant bimodal effect for word and sentence recognition in quiet. Small bimodal effects were observed for sentence
recognition in noise (6%) and tone recognition (4%). The magnitude of both effects was correlated with unaided thresholds at
frequencies near voice fundamental frequencies (F0s). A weak correlation between the bimodal effect for word recognition
and unaided thresholds at frequencies higher than F0s was identified. These results were consistent with previous findings
that showed more robust bimodal benefits for speech recognition tasks that require higher spectral resolution than speech
recognition in quiet. The significant but small F0-related bimodal benefit was also consistent with the limited acoustic hearing
in the nonimplanted ear of the current subject sample, who are representative of the bimodal users in mainland China.
These results advocate for a more relaxed implant candidacy criterion to be used in mainland China
Imaging the Disk around TW Hydrae with the Submillimeter Array
We present ~2"-4" aperture synthesis observations of the circumstellar disk surrounding the nearby young star TW Hya in the CO J = 2-1 and J = 3-2 lines and associated dust continuum obtained with the partially completed Submillimeter Array. The extent and peak flux of the 230 and 345 GHz dust emission follow closely the predictions of the irradiated accretion disk model of Calvet et al. The resolved molecular line emission extends to a radius of at least 200 AU, the full extent of the disk visible in scattered light, and shows a clear pattern of Keplerian rotation. Comparison of the images with two-dimensional Monte Carlo models constrains the disk inclination angle to 7° ± 1°. The CO emission is optically thick in both lines, and the kinetic temperature in the line formation region is ~20 K. Substantial CO depletion, by an order of magnitude or more from canonical dark cloud values, is required to explain the characteristics of the line emission
Nanoscale Zr-containing precipitates; a solution for significant improvement of high-temperature strength in Al-Si-Cu-Mg alloys
Jaguar Range Rove
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Strengthening die-cast Al-Mg and Al-Mg-Mn alloys with Fe as a beneficial element
Jaguar Range Rover (JLR
Excision of a Nasal Dermoid Sinus Cyst via Open Rhinoplasty Approach and Primary Reconstruction Using Tutoplast-Processed Fascia Lata
Nasal dermoid sinus cysts are the most common congenital midline nasal lesion, accounting for 1% to 3% of all dermoid cysts, and 4% to 12% of all head and neck dermoids. Selection of the appropriate reconstruction technique, after dermoid resection, is important for treatment. Here we describe the successful management of a case with a nasal dermoid sinus cyst using an open rhinoplasty approach, and primary reconstruction using Tutoplast-processed fascia lata and crushed septal cartilage
A Genome-Wide Analysis of Promoter-Mediated Phenotypic Noise in Escherichia coli
Gene expression is subject to random perturbations that lead to fluctuations in the rate of protein production. As a consequence, for any given protein, genetically identical organisms living in a constant environment will contain different amounts of that particular protein, resulting in different phenotypes. This phenomenon is known as “phenotypic noise.” In bacterial systems, previous studies have shown that, for specific genes, both transcriptional and translational processes affect phenotypic noise. Here, we focus on how the promoter regions of genes affect noise and ask whether levels of promoter-mediated noise are correlated with genes' functional attributes, using data for over 60% of all promoters in Escherichia coli. We find that essential genes and genes with a high degree of evolutionary conservation have promoters that confer low levels of noise. We also find that the level of noise cannot be attributed to the evolutionary time that different genes have spent in the genome of E. coli. In contrast to previous results in eukaryotes, we find no association between promoter-mediated noise and gene expression plasticity. These results are consistent with the hypothesis that, in bacteria, natural selection can act to reduce gene expression noise and that some of this noise is controlled through the sequence of the promoter region alon
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