157 research outputs found
Treatment of solid tumors with chimeric antigen receptor-engineered T cells: current status and future prospects
The finite-distance gravitational deflection of massive particles in stationary spacetime: a Jacobi metric approach
In this paper, we study the weak gravitational deflection of relativistic
massive particles for a receiver and source at finite distance from the lens in
stationary, axisymmetric and asymptotically flat spacetimes. For this purpose,
we extend the generalized optical metric method to the generalized Jacobi
metric method by using the Jacobi-Maupertuis Randers-Finsler metric. More
specifically,we apply the Gauss-Bonnet theorem to the generalized Jacobi metric
space and then obtain an expression for calculating the deflection angle, which
is related to Gaussian curvature of generalized optical metric and geodesic
curvature of particles orbit. In particular, the finite-distance correction to
the deflection angle of signal with general velocity in the the Kerr black hole
and Teo wormhole spacetimes are considered. Our results cover the previous work
of the deflection angle of light, as well as the deflection angle of massive
particles in the limit for the receive and source at infinite distance from the
lens object. In Kerr black hole spacetime, we compared the effects due to the
black hole spin, the finite-distance of source or receiver, and the
relativistic velocity in microlensings and lensing by galaxies. It is found in
these cases, the effect of BH spin is usually a few orders larger than that of
the finite-distance and relativistic velocity, while the relative size of the
latter two could vary according to the particle velocity, source or observer
distance and other lensing parameters.Comment: 16 pages, 4 figure
Deflection of charged signals in a dipole magnetic field in Schwarzschild background using Gauss-Bonnet theorem
This paper studies the deflection of charged particles in a dipole magnetic
field in Schwarzschild spacetime background in the weak field approximation. To
calculate the deflection angle, we use Jacobi metric and Gauss-Bonnet theorem.
Since the corresponding Jacobi metric is a Finsler metric of Randers type, we
use both the osculating Riemannian metric method and generalized Jacobi metric
method. The deflection angle up to fourth order is obtained and the effect of
the magnetic field is discussed. It is found that the magnetic dipole will
increase (or decrease) the deflection angle of a positively charged signal when
its rotation angular momentum is parallel (or antiparallel) to the magnetic
field. It is argued that the difference in the deflection angles of different
rotation directions can be viewed as a Finslerian effect of the
non-reversibility of the Finsler metric. The similarity of the deflection angle
in this case with that for the Kerr spacetime allows us to directly use the
gravitational lensing results in the latter case. The dependence of the
apparent angles on the magnetic field suggests that by measuring these angles
the magnetic dipole might be constrained.Comment: 13 pages, 3 figure
The deflection of charged massive particles by a 4-Dimensional charged Einstein-Gauss-Bonnet black hole
Based on the Jacobi metric method, this paper studies the deflection of a
charged massive particle by a novel 4-dimensional charged Einstein-Gauss-Bonnet
black hole. We focus on the weak-filed approximation and consider the
deflection angle with finite-distance effects, i.e. the source and observer at
finite distances from the black hole. To this end, we use a geometric and
topological method, which is to apply the Gauss-Bonnet theorem to the
Jacobi-metric surface to calculate the deflection angle. We find that the
deflection angle contains a pure gravitational contribution , a pure
electrostatic one and a gravitational-electrostatic coupling term
. We also show that the electrostatic contribution can
also be computed by the Jacobi-metric method using the GB theorem to a charge
in a Minkowski flat spacetime background. We find that the deflection angle
increases(decreases) if the Gauss-Bonnet coupling constant is
negative(positive). Furthermore, the effects of the BH charge, the particle
charge-to-mass ratio and the particle velocity on the deflection angle are
analyzed.Comment: 11 pages, 5 Figures; conclusion part improved and reference adde
High-responsivity vertical-illumination Si/Ge uni-traveling-carrier photodiodes based on silicon-on-insulator substrate
Si/Ge uni-traveling carrier photodiodes exhibit higher output current when
space-charge effects are overcome and thermal effects are suppressed, which is
highly beneficial for increasing the dynamic range of various microwave
photonic systems and simplifying high-bit-rate digital receivers in different
applications. From the point of view of packaging, detectors with
vertical-illumination configuration can be easily handled by pick-and-place
tools and are a popular choice for making photo-receiver modules. However,
vertical-illumination Si/Ge uni-traveling carrier (UTC) devices suffer from
inter-constraint between high speed and high responsivity. Here, we report a
high responsivity vertical-illumination Si/Ge UTC photodiode based on a
silicon-on-insulator substrate. The maximum absorption efficiency of the
devices was 2.4 times greater than the silicon substrate owing to constructive
interference. The Si/Ge UTC photodiode was successfully fabricated and had a
dominant responsivity at 1550 nm of 0.18 A/W, a 50% improvement even with a 25%
thinner Ge absorption layer.Comment: 5pages,2figure
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