41,971 research outputs found
Analytic structure of the Landau gauge gluon propagator
The results of different non-perturbative studies agree on a power law as the
infrared behavior of the Landau gauge gluon propagator. This propagator
violates positivity and thus indicates the absence of the transverse gluons
from the physical spectrum, i.e. gluon confinement. A simple analytic structure
for the gluon propagator is proposed capturing all of its features. We comment
also on related investigations for the Landau gauge quark propagator.Comment: 4 pages, 2 figures, talk given by R.A. at 6th Conference on Quark
Confinement and the Hadron Spectrum, Villasimius, Sardinia, Italy, 21-25 Sep
200
Probing Unquenching Effects in the Gluon Polarisation in Light Mesons
We introduce an extension to the ladder truncated Bethe-Salpeter equation for
mesons and the rainbow truncated quark Dyson-Schwinger equations which includes
quark-loop corrections to the gluon propagator. This truncation scheme obeys
the axialvector Ward-Takahashi identity relating the quark self-energy and the
Bethe-Salpeter kernel. Two different approximations to the Yang-Mills sector
are used as input: the first is a sophisticated truncation of the full
Yang-Mills Dyson-Schwinger equations, the second is a phenomenologically
motivated form. We find that the spectra and decay constants of pseudoscalar
and vector mesons are overall described well for either approach. Meson mass
results for charge eigenstate vector and pseudoscalar meson masses are compared
to lattice data. The effects of unquenching the system are small but not
negligible.Comment: 26 pages, 13 figure
Mapping of lymphatic filariasis in loiasis areas: A new strategy shows no evidence for Wuchereria bancrofti endemicity in Cameroon
Improving broadband displacement detection with quantum correlations
Interferometers enable ultrasensitive measurement in a wide array of
applications from gravitational wave searches to force microscopes. The role of
quantum mechanics in the metrological limits of interferometers has a rich
history, and a large number of techniques to surpass conventional limits have
been proposed. In a typical measurement configuration, the tradeoff between the
probe's shot noise (imprecision) and its quantum backaction results in what is
known as the standard quantum limit (SQL). In this work we investigate how
quantum correlations accessed by modifying the readout of the interferometer
can access physics beyond the SQL and improve displacement sensitivity.
Specifically, we use an optical cavity to probe the motion of a silicon nitride
membrane off mechanical resonance, as one would do in a broadband displacement
or force measurement, and observe sensitivity better than the SQL dictates for
our quantum efficiency. Our measurement illustrates the core idea behind a
technique known as \textit{variational readout}, in which the optical readout
quadrature is changed as a function of frequency to improve broadband
displacement detection. And more generally our result is a salient example of
how correlations can aid sensing in the presence of backaction.Comment: 17 pages, 5 figure
A brief review of low-dose rate (LDR) and high-dose rate (HDR) brachytherapy boost for high-risk prostate
For patients with unfavorable or high-risk prostate cancer, dose escalated radiation therapy leads to improved progression free survival but attempts to deliver increased dose by external beam radiation therapy (EBRT) alone can be limited by late toxicities to nearby genitourinary and gastrointestinal organs at risk. Brachytherapy is a method to deliver dose escalation in conjunction with EBRT with a potentially improved late toxicity profile and improved prostate cancer related outcomes. At least three randomized controlled trials have demonstrated improved biochemical control with the addition of either low-dose rate (LDR) or high-dose rate (HDR) brachytherapy to EBRT, although only ASCENDE-RT compared brachytherapy to dose-escalated EBRT but did report an over 50% improvement in biochemical failure with a LDR boost. Multiple single institution and comparative research series also support the use of a brachytherapy boost in the DE-EBRT era and demonstrate excellent prostate cancer specific outcomes. Despite improved oncologic outcomes with a brachytherapy boost in the high-risk setting, the utilization of both LDR, and HDR brachytherapy use is declining. The acute genitourinary toxicities when brachytherapy boost is combined with EBRT, particularly a LDR boost, are of concern in comparison to EBRT alone. HDR brachytherapy boost has many physical properties inherent to its rapid delivery of a large dose which may reduce acute toxicities and also appeal to the radiobiology of prostate cancer. We herein review the evidence for use of either LDR or HDR brachytherapy boost for high-risk prostate cancer and summarize comparisons between the two treatment modalities
Instrumentation design study for testing a hypersonic ramjet engine on the x-15 a-2. volume 3- conceptual design of measurement systems
Instrumentation for testing hypersonic ramjet engine on X-15A-2 aircraf
Long-term storage and age‐biased export of fluvial organic carbon: field evidence from West Iceland
Terrestrial organic carbon (OC) plays an important role in the carbon cycle, but questions remain regarding the controls and timescale(s) over which atmospheric CO₂ remains sequestered as particulate OC (POC). Motivated by observations that terrestrial POC is physically stored within soils and other shallow sedimentary deposits, we examined the role that sediment storage plays in the terrestrial OC cycle. Specifically, we tested the hypothesis that sediment storage impacts the age of terrestrial POC. We focused on the Efri Haukadalsá River catchment in Iceland as it lacks ancient sedimentary bedrock that would otherwise bias radiocarbon‐based determinations of POC storage duration by supplying pre‐aged “petrogenic” POC.
Our radiocarbon measurements of riverine suspended sediments and deposits implicated millennial‐scale storage times. Comparison between the sample types (suspended and deposits) suggested an age offset between transported (suspended sediments) and stored (deposits) POC at the time of sampling, which is predicted by theory for the sediment age distribution in floodplains. We also observed that POC in suspended sediments is younger than the predicted mean storage duration generated from independent geomorphological data, which suggested an additional role for OC cycling. Consistent with this, we observed interparticle heterogeneity in the composition of POC by imaging our samples at the microscale using X‐ray absorption spectroscopy. Specifically, we found that particles within individual samples differed in their sulfur oxidation state, which is indicative of multiple origins and/or diagenetic histories. Altogether, our results support recent coupled sediment storage and OC cycling models and indicate that the physical drivers of sediment storage are important factors controlling the cadence of carbon cycling
Consequences Of Fully Dressing Quark-Gluon Vertex Function With Two-Point Gluon Lines
We extend recent studies of the effects of quark-gluon vertex dressing upon
the solutions of the Dyson-Schwinger equation for the quark propagator. A
momentum delta function is used to represent the dominant infrared strength of
the effective gluon propagator so that the resulting integral equations become
algebraic. The quark-gluon vertex is constructed from the complete set of
diagrams involving only 2-point gluon lines. The additional diagrams, including
those with crossed gluon lines, are shown to make an important contribution to
the DSE solutions for the quark propagator, because of their large color
factors and the rapid growth in their number
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