2,855 research outputs found
The disappearance of a narrow Mg II absorption system in quasar SDSS J165501.31+260517.4
In this letter, we present for the first time, the discovery of the
disappearance of a narrow Mg II absorption system
from the spectra of quasar SDSS J165501.31+260517.4 (). This
absorber is located at , and has a velocity offset of
with respect to the quasar. According to the velocity
offset and the line variability, this narrow Mg II
absorption system is likely intrinsic to the quasar. Since the corresponding UV
continuum emission and the absorption lines of another narrow Mg II
absorption system at are very
stable, we think that the disappearance of the absorption system is unlikely to
be caused by the change in ionization of absorption gas. Instead, it likely
arises from the motion of the absorption gas across the line of sight
The Fundamental and Application of Transient Flashing Spray Cooling in Laser Dermatology
Cryogen spray cooling (CSC) has been successfully implemented in laser dermatology such as the treatment of port wine stain. It can protect epidermis from irreversible thermal injuries and increase laser energy, leading to the improvement in therapeutic outcomes. Different from traditional steady spray cooling, CSC is highly transient with short spurt duration (several tens of milliseconds). Besides, CSC can achieve flashing atomization and fine droplets with simple structure nozzles by rapid release of superheat. In this chapter, the mechanism of CSC flashing spray, spray and thermal characteristics of droplets, the measurement method of transient temperature and algorithms for heat flux estimation, and the dynamic surface heat transfer and its relation with spray characteristics are fully discussed. Finally, the heat transfer enhancement of CSC is introduced including alternative cryogens, new nozzles, and hypobaric pressure method to increase the cooling ability, which is essential to improve therapeutic outcome, especially for darkly pigmented human skin
Bounds of the longest directed cycle length for minimal strong digraphs
AbstractIn this paper we present the upper and lower bounds of the longest directed cycle length for minimal strong digraphs in terms of the numbers of vertices and arcs. These bounds are both sharp. In addition, we give analogous results for minimal 2-edge connected graphs
Evaluating Feynman integrals by the hypergeometry
The hypergeometric function method naturally provides the analytic
expressions of scalar integrals from concerned Feynman diagrams in some
connected regions of independent kinematic variables, also presents the systems
of homogeneous linear partial differential equations satisfied by the
corresponding scalar integrals. Taking examples of the one-loop and
massless functions, as well as the scalar integrals of two-loop vacuum
and sunset diagrams, we verify our expressions coinciding with the well-known
results of literatures. Based on the multiple hypergeometric functions of
independent kinematic variables, the systems of homogeneous linear partial
differential equations satisfied by the mentioned scalar integrals are
established. Using the calculus of variations, one recognizes the system of
linear partial differential equations as stationary conditions of a functional
under some given restrictions, which is the cornerstone to perform the
continuation of the scalar integrals to whole kinematic domains numerically
with the finite element methods. In principle this method can be used to
evaluate the scalar integrals of any Feynman diagrams.Comment: 39 pages, including 2 ps figure
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