5,685 research outputs found
Performance of a azimuthally excited 3D-printed resonator for multi-pass spectroscopic applications
A design is presented for an acoustically resonant cell, based on the excitation of azimuthal resonances, to enhance the sensitivity of multi-pass photoacoustic spectroscopy. The acoustic cell is fabricated in one part using a photo-polymerization based 3D-Printing technique. Characterization of the cell performance is undertaken using calibrated concentrations of methane. The quality factor (< 76) of the cell compares favorably to existing designs based on longitudinal resonances. The minimum detectable normalized noise equivalent absorption coefficient for the cell was measured as: 3.667×10^ -10 Wcm^-1 Hz^-1/2, resulting in a minimum sensitivity for methane of 6 ppm with 700 s of averaging
Direct photon production with effective field theory
The production of hard photons in hadronic collisions is studied using
Soft-Collinear Effective Theory (SCET). This is the first application of SCET
to a physical, observable cross section involving energetic partons in more
than two directions. A factorization formula is derived which involves a
non-trivial interplay of the angular dependence in the hard and soft functions,
both quark and gluon jet functions, and multiple partonic channels. The
relevant hard, jet and soft functions are computed to one loop and their
anomalous dimensions are determined to three loops. The final resummed
inclusive direct photon distribution is valid to next-to-next-to-leading
logarithmic order (NNLL), one order beyond previous work. The result is
improved by including non-logarithmic terms and photon isolation cuts through
matching, and compared to Tevatron data and to fixed order results at the
Tevatron and the LHC. The resummed cross section has a significantly smaller
theoretical uncertainty than the next-to-leading fixed-order result,
particularly at high transverse momentum.Comment: 42 pages, 9 figures; v2: references added, minor changes; v3: typos;
v4: typos, corrections in (16), (47), (72
An unusual interplay among disorder, Kondo-effect and spin-glass behavior in the Kondo lattices, CeAuCoSi
We report the results of magnetic measurements for the solid solution
CeAuCoSi. The results reveal that this solid solution is
characterized by a magnetic phase diagram (plot of magnetic transition
temperature versus ) unusual for Kondo lattices. In particular, the
spin-glass freezing induced by disorder is observed only for the compositions
at the weak coupling limit; as one approaches the quantum critical point by a
gradual replacement of Au by Co, this disorder effect is surprisingly
suppressed in favor of long range antiferro-magnetic ordering in contrast to
expectations. This unusual interplay between disorder, spin-glass freezing and
the Kondo-effect calls for further refinement of theories on competition
between magnetism and the Kondo effect.Comment: 4 pages, 3 figure
Electron correlation and interference effects in strong-field processes
Several correlation and interference effects in strong-field physics are
investigated. We show that the interference of continuum wave packets can be
the dominant mechanism of high-harmonic generation (HHG) in the
over-the-barrier regime. Next, we combine HHG with resonant x-ray excitation to
force the recolliding continuum electron to recombine with a core hole rather
than the valence hole from that it was previously tunnel ionized. The scheme
opens up perspectives for nonlinear xuv physics, attosecond x-ray pulses, and
spectroscopy of core orbitals. Then, a method is proposed to generate
attochirp-free harmonic pulses by engineering the appropriate electron wave
packet. Finally, resonant photoionization mechanisms involving two atoms are
discussed which can dominate over the direct single-atom ionization channel at
interatomic distances in the nanometer range.Comment: to be published in Springer Proceedings "Multiphoton Processes and
Attosecond Physics
The COVID rehabilitation paradox: why we need to protect and develop geriatric rehabilitation services in the face of the pandemic. Comment
Older multi-morbid persons often fall seriously ill due to COVID-19. To be able to participate in a social life again, they often need special rehabilitation measures. Geriatric rehabilitation is a multi-professional service geared to these needs. Paradoxically, however, capacities in geriatric rehabilitation are currently being reduced despite increasing demand. The reasons are manifold and are not only due to the current situation. This article highlights the current situation leading to the COVID rehabilitation paradox and shows ways to learn from it for the future.</p
Innovations in the Analysis of Chandra-ACIS Observations
As members of the instrument team for the Advanced CCD Imaging Spectrometer
(ACIS) on NASA's Chandra X-ray Observatory and as Chandra General Observers, we
have developed a wide variety of data analysis methods that we believe are
useful to the Chandra community, and have constructed a significant body of
publicly-available software (the ACIS Extract package) addressing important
ACIS data and science analysis tasks. This paper seeks to describe these data
analysis methods for two purposes: to document the data analysis work performed
in our own science projects, and to help other ACIS observers judge whether
these methods may be useful in their own projects (regardless of what tools and
procedures they choose to implement those methods).
The ACIS data analysis recommendations we offer here address much of the
workflow in a typical ACIS project, including data preparation, point source
detection via both wavelet decomposition and image reconstruction, masking
point sources, identification of diffuse structures, event extraction for both
point and diffuse sources, merging extractions from multiple observations,
nonparametric broad-band photometry, analysis of low-count spectra, and
automation of these tasks. Many of the innovations presented here arise from
several, often interwoven, complications that are found in many Chandra
projects: large numbers of point sources (hundreds to several thousand), faint
point sources, misaligned multiple observations of an astronomical field, point
source crowding, and scientifically relevant diffuse emission.Comment: Accepted by the ApJ, 2010 Mar 10 (\#343576) 39 pages, 16 figure
Patient prioritization of comorbid chronic conditions in the Veteran population: Implications for patient-centered care
OBJECTIVE: Patients with comorbid chronic conditions may prioritize some conditions over others; however, our understanding of factors influencing those prioritizations is limited. In this study, we sought to identify and elaborate a range of factors that influence how and why patients with comorbid chronic conditions prioritize their conditions.
METHODS: We conducted semi-structured, one-on-one interviews with 33 patients with comorbidities recruited from a single Veterans Health Administration Medical Center.
FINDINGS: The diverse factors influencing condition prioritization reflected three overarching themes: (1) the perceived role of a condition in the body, (2) self-management tasks, and (3) pain. In addition to these themes, participants described the rankings that they believed their healthcare providers would assign to their conditions as an influencing factor, although few reported having shared their priorities or explicitly talking with providers about the importance of their conditions.
CONCLUSION: Studies that advance understanding of how and why patients prioritize their various conditions are essential to providing care that is patient-centered, reflecting what matters most to the individual while improving their health. This analysis informs guideline development efforts for the care of patients with comorbid chronic conditions as well as the creation of tools to promote patient-provider communication regarding the importance placed on different conditions
Charmless two-body B decays: A global analysis with QCD factorization
In this paper, we perform a global analysis of and decays
with the QCD factorization approach. It is encouraging to observe that the
predictions of QCD factorization are in good agreement with experiment. The
best fit is around . The penguin-to-tree ratio of decays is preferred to be larger than 0.3.
We also show the confidence levels for some interesting channels: , and , . For decays, they are expected to have smaller branching ratios with
more precise measurements.Comment: 20 pages, 4 figures, version to appear in Phys. Rev.
The Radio - X-ray relation as a star formation indicator: Results from the VLA--E-CDFS Survey
In order to trace the instantaneous star formation rate at high redshift, and
hence help understanding the relation between the different emission mechanisms
related to star formation, we combine the recent 4 Ms Chandra X-ray data and
the deep VLA radio data in the Extended Chandra Deep Field South region. We
find 268 sources detected both in the X-ray and radio band. The availability of
redshifts for of the sources in our sample allows us to derive
reliable luminosity estimates and the intrinsic properties from X-ray analysis
for the majority of the objects. With the aim of selecting sources powered by
star formation in both bands, we adopt classification criteria based on X-ray
and radio data, exploiting the X-ray spectral features and time variability,
taking advantage of observations scattered across more than ten years. We
identify 43 objects consistent with being powered by star formation. We also
add another 111 and 70 star forming candidates detected only in the radio or
X-ray band, respectively. We find a clear linear correlation between radio and
X-ray luminosity in star forming galaxies over three orders of magnitude and up
to . We also measure a significant scatter of the order of 0.4 dex,
higher than that observed at low redshift, implying an intrinsic scatter
component. The correlation is consistent with that measured locally, and no
evolution with redshift is observed. Using a locally calibrated relation
between the SFR and the radio luminosity, we investigate the L_X(2-10keV)-SFR
relation at high redshift. The comparison of the star formation rate measured
in our sample with some theoretical models for the Milky Way and M31, two
typical spiral galaxies, indicates that, with current data, we can trace
typical spirals only at z<0.2, and strong starburst galaxies with
star-formation rates as high as , up to .Comment: 21 pages, 10 figures, 5 table
A Description of Quasar Variability Measured Using Repeated SDSS and POSS Imaging
We provide a quantitative description and statistical interpretation of the
optical continuum variability of quasars. The Sloan Digital Sky Survey (SDSS)
has obtained repeated imaging in five UV-to-IR photometric bands for 33,881
spectroscopically confirmed quasars. About 10,000 quasars have an average of 60
observations in each band obtained over a decade along Stripe 82 (S82), whereas
the remaining ~25,000 have 2-3 observations due to scan overlaps. The observed
time lags span the range from a day to almost 10 years, and constrain quasar
variability at rest-frame time lags of up to 4 years, and at rest-frame
wavelengths from 1000A to 6000A. We publicly release a user-friendly catalog of
quasars from the SDSS Data Release 7 that have been observed at least twice in
SDSS or once in both SDSS and the Palomar Observatory Sky Survey, and we use it
to analyze the ensemble properties of quasar variability. Based on a damped
random walk (DRW) model defined by a characteristic time scale and an
asymptotic variability amplitude that scale with the luminosity, black hole
mass, and rest wavelength for individual quasars calibrated in S82, we can
fully explain the ensemble variability statistics of the non-S82 quasars such
as the exponential distribution of large magnitude changes. All available data
are consistent with the DRW model as a viable description of the optical
continuum variability of quasars on time scales of ~5-2000 days in the rest
frame. We use these models to predict the incidence of quasar contamination in
transient surveys such as those from PTF and LSST.Comment: 33 pages, 19 figures, replaced with accepted version. Catalog is
available at http://www.astro.washington.edu/users/ivezic/macleod/qso_dr7
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