826 research outputs found
Heavy flavor quenching and flow: the roles of initial condition, pre-equilibrium evolution and in-medium interaction
Within an advanced Langevin-hydrodynamics framework coupled to a hybrid
fragmentation-coalescence hadronization model, we study heavy flavor quenching
and flow in relativistic heavy-ion collisions. We investigate how the initial
heavy quark spectrum, the energy loss and hadronization mechanisms of heavy
quarks in medium, the evolution profile of pre-equilibrium stage, the flow of
medium and the temperature dependence of heavy quark diffusion coefficient
influence the suppression and elliptic flow of heavy mesons at RHIC and the
LHC. Our result shows that different modeling of initial conditions,
pre-equilibrium evolution and in-medium interaction can individually yield
about 10-40% uncertainties in D meson suppression and flow at low transverse
momentum. We also find that a proper combination of collisional versus
radiative energy loss, coalescence versus fragmentation in hadronization, and
the inclusion of medium flow are the most important factors for describing the
suppression and elliptic flow of heavy mesons.Comment: 9 pages, 7 figures; to be published in Chinese Physics
Charmed hadron chemistry in relativistic heavy-ion collisions
We develop for charmed hadron production in relativistic heavy-ion collisions
a comprehensive coalescence model that includes an extensive set of and
-wave hadronic states as well as the strict energy-momentum conservation,
which ensures the boost invariance of the coalescence probability and the
thermal limit of the produced hadron spectrum. By combining our hadronization
scheme with an advanced Langevin-hydrodynamics model that incorporates both
elastic and inelastic energy loss of heavy quarks inside the dynamical
quark-gluon plasma, we obtain a successful description of the
-integrated and differential and ratios
measured at RHIC and the LHC. We find that including the effect of radial flow
of the medium is essential for describing the enhanced ratio
observed in relativistic heavy-ion collisions. We also find that the puzzling
larger ratio observed in Au+Au collisions at RHIC than in Pb+Pb
collisions at the LHC is due to the interplay between the effects of the QGP
radial flow and the charm quark transverse momentum spectrum at hadronization.
Our study further suggests that charmed hadrons have larger sizes in medium
than in vacuum.Comment: 6 pages, 5 figure
The management of a duodenal fistula involving the right hepatic duct: a rare case report
The formation of an internal fistula between the biliary system and the gastrointestinal tract is a rare condition with various etiologies, predominantly associated with recurrent chronic inflammation of the biliary system and tumors. Patients with this condition may lack specific clinical manifestations, presenting with symptoms such as abdominal pain, fever, jaundice, or may show no clinical signs at all. Common types of internal fistulas include cholecystoduodenal fistula, cholecystocolonic fistula, and choledochoduodenal fistula. Among these, the right hepaticoduodenal fistula is extremely rare and seldom reported in clinical literature. We herein report a case of right hepaticoduodenal fistula and analyze its mechanism, treatment principles, and preventive measures through a literature review
Association between Sex Hormone and Blood Uric Acid in Male Patients with Type 2 Diabetes
The association between serum uric acid (SUA) level and sexual dysfunction in patients with diabetes is not well characterized. Type 2 diabetes mellitus (T2DM) causes metabolic disorders, including abnormal serum uric acid (SUA) levels. In this study, we enrolled 205 male patients with T2DM and investigated the relationship between sex hormone levels and SUA. Patients were divided into four groups based on SUA quartiles. On the other hand, based on the total testosterone (TT) level, patients were divided into three groups; SUA and other laboratory indices were determined. Increase in SUA level was significantly associated with decreased levels of TT, luteinizing hormone, follicle-stimulating hormone, sex hormone-binding globulin, and increased levels of dehydroepiandrosterone, age, body mass index (BMI), waist circumference, glycated hemoglobin, serum creatinine, and HOMA-IR levels. SUA, waist circumference, BMI, and HOMA-IR showed a negative correlation with TT level, while age showed a positive correlation with TT level. SUA and body mass index were found to be risk factors for gonadal dysfunction. Therefore, we conclude that hypogonadism of male patients with T2DM is related to SUA level
Frequency tuning behaviour of terahertz quantum cascade lasers revealed by a laser beating scheme
In the terahertz frequency range, the commercialized spectrometers, such as the Fourier transform infrared and time domain spectroscopies, show spectral resolutions between a hundred megahertz and a few gigahertz. Therefore, the high precision frequency tuning ability of terahertz lasers cannot be revealed by these traditional spectroscopic techniques. In this work, we demonstrate a laser beating experiment to investigate the frequency tuning characteristics of terahertz quantum cascade lasers (QCLs) induced by temperature or drive current. Two terahertz QCLs emitting around 4.2 THz with identical active regions and laser dimensions (150 μm wide and 6 mm long) are employed in the beating experiment. One laser is operated as a frequency comb and the other one is driven at a lower current to emit a single frequency. To measure the beating signal, the single mode laser is used as a fast detector (laser self-detection). The laser beating scheme allows the high precision measurement of the frequency tuning of the single mode terahertz QCL. The experimental results show that in the investigated temperature and current ranges, the frequency tuning coefficients of the terahertz QCL are 6.1 MHz/0.1 K (temperature tuning) and 2.7 MHz/mA (current tuning) that cannot be revealed by a traditional terahertz spectrometer. The laser beating technique shows potential abilities in high precision linewidth measurements of narrow absorption lines and multi-channel terahertz communications
VLBI astrometry on the white dwarf pulsar AR Scorpii
AR Scorpii (AR Sco), the only-known radio-pulsing white dwarf binary, shows unusual pulsating emission at the radio, infrared, optical, and ultraviolet bands. To determine its astrometric parameters at the radio band independently, we conducted multi-epoch Very Long Baseline Interferometry (VLBI) phase-referencing observations with the European VLBI Network at 5 GHz and the Chinese VLBI Network plus the Warkworth 30-m telescope (New Zealand) at 8.6 GHz. By using the differential VLBI astrometry, we provide high-precision astrometric measurements on the parallax (pi = 8.52(-0.07)(+0.04) mas) and proper motion (mu(alpha) = 9.48(-0.07)(+0.04) mas yr(-1), mu(delta) = -51.32(-0.38)(+0.22) mas yr (-1)). The new VLBI results agree with the optical Gaia astrometry. Our kinematic analysis reveals that the Galactic space velocities of AR Sco are quite consistent with that of both intermediate polars and polars. Combined with the previous tightest VLBI constraint on the size, our parallax distance suggests that the radio emission of AR Sco should be located within the light cylinder of its white dwarf
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