18,623 research outputs found
Metabolic profile, bioavailability and toxicokinetics of zearalenone-14-glucoside in rats after oral and intravenous administration by liquid chromatography high-resolution mass spectrometry and tandem mass spectrometry
Zearalenone-14-glucoside (ZEN-14G), a key modified mycotoxin, has attracted a great deal of attention due to the possible conversion to its free form of zearalenone (ZEN) exerting toxicity. In this study, the toxicokinetics of ZEN-14G were investigated in rats after oral and intravenous administration. The plasma concentrations of ZEN-14G and its major five metabolites were quantified using a validated liquid chromatography tandem mass spectrometry (LC-MS/MS) method. The data were analyzed via non-compartmental analysis using software WinNonlin 6.3. The results indicated that ZEN-14G was rapidly hydrolyzed into ZEN in vivo. In addition, the major parameters of ZEN-14G following intravenous administration were: area under the plasma concentration-time curve (AUC), 1.80 h.ng/mL; the apparent volume of distribution (V-Z), 7.25 L/kg; and total body clearance (CL), 5.02 mL/h/kg, respectively. After oral administration, the typical parameters were: AUC, 0.16 h.ng/mL; V-Z, 6.24 mL/kg; and CL, 4.50 mL/h/kg, respectively. The absolute oral bioavailability of ZEN-14G in rats was about 9%, since low levels of ZEN-14G were detected in plasma, which might be attributed to its extensive metabolism. Therefore, liquid chromatography high-resolution mass spectrometry (LC-HRMS) was adopted to clarify the metabolic profile of ZEN-14G in rats' plasma. As a result, eight metabolites were identified in which ZEN-14-glucuronic acid (ZEN-14GlcA) had a large yield from the first time-point and continued accumulating after oral administration, indicating that ZEN-14-glucuronic acid could serve a potential biomarker of ZEN-14G. The obtained outcomes would prompt the accurate safety evaluation of ZEN-14G
Formation of new stellar populations from gas accreted by massive young star clusters
Stars in star clusters are thought to form in a single burst from a common
progenitor cloud of molecular gas. However, massive, old globular clusters --
with ages greater than 10 billion years and masses of several hundred thousand
solar masses -- often harbour multiple stellar populations, indicating that
more than one star-forming event occurred during their lifetimes. Colliding
stellar winds from late-stage, asymptotic-giant-branch stars are often invoked
as second-generation star-formation trigger. The initial cluster masses should
be at least 10 times more massive than they are today for this to work.
However, large populations of clusters with masses greater than a few million
solar masses are not found in the local Universe. Here we report on three 1-2
billion-year-old, massive star clusters in the Magellanic Clouds, which show
clear evidence of burst-like star formation that occurred a few hundred million
years after their initial formation era. We show that such clusters could
accrete sufficient gas reservoirs to form new stars if the clusters orbited in
their host galaxies' gaseous discs throughout the period between their initial
formation and the more recent bursts of star formation. This may eventually
give rise to the ubiquitous multiple stellar populations in globular clusters.Comment: 10 pages, 11 figures, Authors' version of a letter published in
Nature (27 January 2016), including Methods and Extended Dat
Maximum Estrada Index of Bicyclic Graphs
Let be a simple graph of order , let
be the eigenvalues of the
adjacency matrix of . The Esrada index of is defined as
. In this paper we determine the unique
graph with maximum Estrada index among bicyclic graphs with fixed order
Gravitational conundrum? Dynamical mass segregation versus disruption of binary stars in dense stellar systems
Upon their formation, dynamically cool (collapsing) star clusters will,
within only a few million years, achieve stellar mass segregation for stars
down to a few solar masses, simply because of gravitational two-body
encounters. Since binary systems are, on average, more massive than single
stars, one would expect them to also rapidly mass segregate dynamically.
Contrary to these expectations and based on high-resolution Hubble Space
Telescope observations, we show that the compact, 15-30 Myr-old Large
Magellanic Cloud cluster NGC 1818 exhibits tantalizing hints at the >= 2 sigma
level of significance (> 3 sigma if we assume a power-law secondary-to-primary
mass-ratio distribution) of an increasing fraction of F-star binary systems
(with combined masses of 1.3-1.6 Msun) with increasing distance from the
cluster center, specifically between the inner 10 to 20" (approximately
equivalent to the cluster's core and half-mass radii) and the outer 60 to 80".
If confirmed, this will offer support of the theoretically predicted but thus
far unobserved dynamical disruption processes of the significant population of
'soft' binary systems---with relatively low binding energies compared to the
kinetic energy of their stellar members---in star clusters, which we have
access to here by virtue of the cluster's unique combination of youth and high
stellar density.Comment: Accepted for publication in The Astrophysical Journal; 19 pages in
AASTeX format; 3 figure
Treating Simple Tibia Fractures with Poly-DL-Lactic Acid Screw as a Locked Intramedullary Nail
Purpose: To investigate the curative effect of poly-DL-lactic acid (PDLLA) absorbable screw as a locked intramedullary nail for simple tibia fractures.Methods: In this study, 35 patients treated with the PDLLA screw were observed, and another 35 patients treated with a traditional locking intramedullary nail were treated as controls. Intraoperative blood loss, postoperative complications, fracture-healing time, and Johner-Wruh grade at the last followup time point of the two treatment groups were compared.Results: No patients experienced neurovascular injury during the operation, and no significant difference was observed in the operation and intraoperative blood loss of both two groups (p > 0.05). Postoperative x-ray results showed that the counterpoint and alignment of the fractures were favorable and that no rotational displacement had occurred. The follow-up period for all patients was 6 - 24 months, with a mean of 15.6 ± 6.7 months. All patients treated with PDLLA screw were observed to have well-healed tibia fractures, while three patients in the traditional treatment group appeared to have undesirable fracture healing. No infection, breakage of the internal fixator, or rotational displacement was found in either of the two groups, and no significant difference was observed in complication incidence between the two groups (p > 0.05). Additionally, Johner-Wruh grading showed no statistically significant difference between the two groups (p > 0.05). Interestingly, the fracture-healing time of the PDLLA screw-treated patients was significantly shortened compared with that of traditional treatment patients (p < 0.05).Conclusion: PDLLA screw, as a locked intramedullary nail, is a promising treatment for simple tibia fracture
Storage of multiple single-photon pulses emitted from a quantum dot in a solid-state quantum memory
Quantum repeaters are critical components for distributing entanglement over
long distances in presence of unavoidable optical losses during transmission.
Stimulated by Duan-Lukin-Cirac-Zoller protocol, many improved quantum-repeater
protocols based on quantum memories have been proposed, which commonly focus on
the entanglement-distribution rate. Among these protocols, the elimination of
multi-photons (multi-photon-pairs) and the use of multimode quantum memory are
demonstrated to have the ability to greatly improve the
entanglement-distribution rate. Here, we demonstrate the storage of
deterministic single photons emitted from a quantum dot in a
polarization-maintaining solid-state quantum memory; in addition,
multi-temporal-mode memory with , and narrow single-photon pulses
is also demonstrated. Multi-photons are eliminated, and only one photon at most
is contained in each pulse. Moreover, the solid-state properties of both
sub-systems make this configuration more stable and easier to be scalable. Our
work will be helpful in the construction of efficient quantum repeaters based
on all-solid-state devicesComment: Published version, including supplementary materia
Loop Formulas for Description Logic Programs
Description Logic Programs (dl-programs) proposed by Eiter et al. constitute
an elegant yet powerful formalism for the integration of answer set programming
with description logics, for the Semantic Web. In this paper, we generalize the
notions of completion and loop formulas of logic programs to description logic
programs and show that the answer sets of a dl-program can be precisely
captured by the models of its completion and loop formulas. Furthermore, we
propose a new, alternative semantics for dl-programs, called the {\em canonical
answer set semantics}, which is defined by the models of completion that
satisfy what are called canonical loop formulas. A desirable property of
canonical answer sets is that they are free of circular justifications. Some
properties of canonical answer sets are also explored.Comment: 29 pages, 1 figures (in pdf), a short version appeared in ICLP'1
Controlled unidirectional reflectionlessness by coupling strength in a non-Hermitian waveguide quantum electrodynamics system
Unidirectional reflectionlessness is investigated in a waveguide quantum
electrodynamics system that consists of a cavity and a -type
three-level quantum dot coupled to a one-dimensional plasmonic waveguide.
Analytical expressions of transmission and reflection coefficients are derived
and discussed for both resonant and off-resonant couplings. By appropriately
modulating the coupling strength, phase shift and Rabi frequency,
unidirectional reflectionlessness is observed at the exceptional points. And
unidirectional coherent perfect absorption is exhibited at the vicinity of
exceptional point. These results might find applications in designing quantum
devices of photons, such as optical switches and single-photon transistors.Comment: 11 pages, 7 figure
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