1,765 research outputs found
X-ray luminescence computed tomography using a focused X-ray beam
Due to the low X-ray photon utilization efficiency and low measurement
sensitivity of the electron multiplying charge coupled device (EMCCD) camera
setup, the collimator based narrow beam X-ray luminescence computed tomography
(XLCT) usually requires a long measurement time. In this paper, we, for the
first time, report a focused X-ray beam based XLCT imaging system with
measurements by a single optical fiber bundle and a photomultiplier tube (PMT).
An X-ray tube with a polycapillary lens was used to generate a focused X-ray
beam whose X-ray photon density is 1200 times larger than a collimated X-ray
beam. An optical fiber bundle was employed to collect and deliver the emitted
photons on the phantom surface to the PMT. The total measurement time was
reduced to 12.5 minutes. For numerical simulations of both single and six fiber
bundle cases, we were able to reconstruct six targets successfully. For the
phantom experiment, two targets with an edge-to-edge distance of 0.4 mm and a
center-to-center distance of 0.8 mm were successfully reconstructed by the
measurement setup with a single fiber bundle and a PMT.Comment: 39 Pages, 12 Figures, 2 Tables, In submission (under review) to JB
Patient Uncertainty About Physician Online Service Availability
In online medical consultation platforms, the situation when patients pursue a physician who has no availability to respond to the request is averse to patients, physicians, and the platform. We explore a potential coordinating mechanism by information intervention in the platform, namely service availability information disclosure. To demonstrate the effectiveness of the intervention, we first explore whether capacity is the potential constraint to the physicians’ acceptance rate. After that, we explore the effect of the intervention on matching efficiency and quality. Our result demonstrates that there is a negative relationship between the number of consultation requests received, which is the premise of the effectiveness of the intervention
Regularization dependence of pion generalised parton distributions
Pion generalised parton distributions are calculated within the framework of
the Nambu--Jona-Lasinio model using different regularization schemes, including
the proper time regularization scheme, the three dimensional momentum cutoff
scheme, the four dimensional momentum cutoff scheme, and the Pauli-Villars
regularization scheme. Furthermore, we check the theoretical constraints of
pion generalised parton distributions required by the symmetries of quantum
chromodynamics in different regularization schemes. The diagrams of pion parton
distribution functions are plotted, in addition, we evaluate the Mellin moments
of generalised parton distributions, which related to the electromagnetic and
gravitational form factors of pion. Pion generalised parton distributions are
continuous but not differential at , when considering the effect
of D-term, generalised parton distributions become not continuous at in all the four regularization schemes. Generalised parton distributions
in impact parameter space are considered, the width distribution of quark
in the pion and the mean-squared
are calculated. The light-front transverse-spin distributions are studied, when
quark polarized in the light-front-transverse direction, the
transverse-spin density is no longer symmetric around , the
peaks shift to , we compare the average transverse shift
and in
different regularization schemes. The light-cone energy radius and
the light-cone charge radius are also evaluated, we find that in the
proper time regularization scheme the values of these quantities are the
largest, in the three dimensional momentum cutoff scheme they are the smallest.Comment: 34 pages, 39 figure
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