7,632 research outputs found
Exact solutions of embedding the four-dimensional perfect fluid in a five- or higher-dimensional Einstein spacetime and the cosmological interpretations
We investigate an exact solution that describes the embedding of the
four-dimensional (4D) perfect fluid in a five-dimensional (5D) Einstein
spacetime. The effective metric of the 4D perfect fluid as a hypersurface with
induced matter is equivalent to the Robertson-Walker metric of cosmology. This
general solution shows interconnections among many 5D solutions, such as the
solution in the braneworld scenario and the topological black hole with
cosmological constant. If the 5D cosmological constant is positive, the metric
periodically depends on the extra dimension. Thus we can compactify the extra
dimension on and study the phenomenological issues. We also generalize
the metric ansatz to the higher-dimensional case, in which the 4D part of the
Einstein equations can be reduced to a linear equation.Comment: 8 pages, 1 figures; v2: minor errors corrected; v3: references added;
v4: matches the version to appear in PL
Quantitative Assessment of Robotic Swarm Coverage
This paper studies a generally applicable, sensitive, and intuitive error
metric for the assessment of robotic swarm density controller performance.
Inspired by vortex blob numerical methods, it overcomes the shortcomings of a
common strategy based on discretization, and unifies other continuous notions
of coverage. We present two benchmarks against which to compare the error
metric value of a given swarm configuration: non-trivial bounds on the error
metric, and the probability density function of the error metric when robot
positions are sampled at random from the target swarm distribution. We give
rigorous results that this probability density function of the error metric
obeys a central limit theorem, allowing for more efficient numerical
approximation. For both of these benchmarks, we present supporting theory,
computation methodology, examples, and MATLAB implementation code.Comment: Proceedings of the 15th International Conference on Informatics in
Control, Automation and Robotics (ICINCO), Porto, Portugal, 29--31 July 2018.
11 pages, 4 figure
Appearance and disappearance of superconductivity in SmFe1-xNixAsO (x = 0.0 to 1.0)
Bulk polycrystalline Ni-substituted SmFe1-xNixAsO (x = 0.0 to 1.0) samples
are synthesized by solid state reaction route in an evacuated sealed quartz
tube. The cell volume decreases with increase of Ni content in SmFe1-xNixAsO,
thus indicating successful substitution of smaller ion Ni at Fe site. The
resistivity measurements showed that the spin-density-wave (SDW) transition is
suppressed drastically with Ni doping and subsequently superconductivity is
achieved in a narrow range of x from 0.04 to 0.10 with maximum Tc of 9K at x =
0.06. For higher content of Ni (x > 0.10), the system becomes metallic and
superconductivity is not observed down to 2K. The magneto-transport [R(T)H]
measurements exhibited the upper critical field [Hc2(0)] of up to 300kOe. The
flux flow activation energy (U/kB) is estimated ~98.37K for 0.1T field.
Magnetic susceptibility measurements also confirms bulk superconductivity for x
= 0.04, 0.06 and 0.08 samples. The lower critical field (Hc1) is around 100Oe
at 2K for x = 0.06 sample. Heat capacity CP(T) measurements exhibited a hump
like transition pertaining to SDW in Fe planes at around 150K and an AFM
ordering of Sm spins below temperature of 5.4K for ordered Sm spins [TN(Sm)].
Though, the SDW hump for Fe spins disappears for Ni doped samples, the TN (Sm)
remains unaltered but with a reduced transition height, i.e., decreased
entropy. In conclusion, complete phase diagram of SmFe1-xNixAsO (x = 0.0 to
1.0) is studied in terms of its structural, electrical, magnetic and thermal
properties.Comment: 18 pages text + Figures; comments suggestions welcome
([email protected]
Consensus of linear multi-agent systems with fully distributed control gains under a general directed graph
Deterministic, Stash-Free Write-Only ORAM
Write-Only Oblivious RAM (WoORAM) protocols provide privacy by encrypting the
contents of data and also hiding the pattern of write operations over that
data. WoORAMs provide better privacy than plain encryption and better
performance than more general ORAM schemes (which hide both writing and reading
access patterns), and the write-oblivious setting has been applied to important
applications of cloud storage synchronization and encrypted hidden volumes. In
this paper, we introduce an entirely new technique for Write-Only ORAM, called
DetWoORAM. Unlike previous solutions, DetWoORAM uses a deterministic,
sequential writing pattern without the need for any "stashing" of blocks in
local state when writes fail. Our protocol, while conceptually simple, provides
substantial improvement over prior solutions, both asymptotically and
experimentally. In particular, under typical settings the DetWoORAM writes only
2 blocks (sequentially) to backend memory for each block written to the device,
which is optimal. We have implemented our solution using the BUSE (block device
in user-space) module and tested DetWoORAM against both an encryption only
baseline of dm-crypt and prior, randomized WoORAM solutions, measuring only a
3x-14x slowdown compared to an encryption-only baseline and around 6x-19x
speedup compared to prior work
Distributed tracking control of leader-follower multi-agent systems under noisy measurement
In this paper, a distributed tracking control scheme with distributed
estimators has been developed for a leader-follower multi-agent system with
measurement noises and directed interconnection topology. It is supposed that
each follower can only measure relative positions of its neighbors in a noisy
environment, including the relative position of the second-order active leader.
A neighbor-based tracking protocol together with distributed estimators is
designed based on a novel velocity decomposition technique. It is shown that
the closed loop tracking control system is stochastically stable in mean square
and the estimation errors converge to zero in mean square as well. A simulation
example is finally given to illustrate the performance of the proposed control
scheme.Comment: 8 Pages, 3 figure
Tunable-focus liquid lens controlled using a servo motor
We demonstrated a liquid lens whose focal length can be controlled by a servo motor. The lens cell is composed of elastic membrane, planar glass plate, a periphery sealing ring, and a liquid with a fixed volume in the lens chamber. Part of the periphery sealing ring is excavated to form a hollow chamber which functions as a reservoir. This hollowed periphery is surrounded by an exterior rubber membrane. The arm of a servo motor is used to deform the elastic rubber. Squeezing the liquid contained in the reservoir into the lens chamber. Excess liquid in the lens chamber will push the lens membrane to outward, resulting in a lens shape change. Due to the compact structure and easy operation, this liquid lens has potential applications in zoom lenses, auto beam steering, and eyeglasses
A Particle-based Multiscale Solver for Compressible Liquid-Vapor Flow
To describe complex flow systems accurately, it is in many cases important to
account for the properties of fluid flows on a microscopic scale. In this work,
we focus on the description of liquid-vapor flow with a sharp interface between
the phases. The local phase dynamics at the interface can be interpreted as a
Riemann problem for which we develop a multiscale solver in the spirit of the
heterogeneous multiscale method, using a particle-based microscale model to
augment the macroscopic two-phase flow system. The application of a microscale
model makes it possible to use the intrinsic properties of the fluid at the
microscale, instead of formulating (ad-hoc) constitutive relations
The imaginary part of the gap function in color superconductivity
We clarify general properties of the energy gap regarding its functional
dependence on the energy-momentum dictated by the invariance under a space
inversion or a time reversal. Then we derive perturbatively the equation of the
imaginary part of the gap function for dense QCD in weak coupling and
generalize our results from 2SC case to CFL case. We confirm that the imaginary
part is down by relative to the real part in weak coupling. The numerical
results show that, up to the leading order, the imaginary part is no larger
than one MeV at extremely large densities and can be as large as several MeV
the densities are of physical interest.Comment: 15 pages, 2 figures, typos corrected, a figure replaced. The version
to be appeared in Nucl.Phys.
Bcl-2 expression is altered with ovarian tumor progression: an immunohistochemical evaluation
<p>Abstract</p> <p>Background</p> <p>Ovarian cancer is the most lethal gynecologic malignancy. The ovarian tumor microenvironment is comprised of tumor cells, surrounding stroma, and circulating lymphocytes, an important component of the immune response, in tumors. Previous reports have shown that the anti-apoptotic protein Bcl-2 is overexpressed in many solid neoplasms, including ovarian cancers, and contributes to neoplastic transformation and drug-resistant disease, resulting in poor clinical outcome. Likewise, studies indicate improved clinical outcome with increased presence of lymphocytes. Therefore, we sought to examine Bcl-2 expression in normal, benign, and cancerous ovarian tissues to determine the potential relationship between epithelial and stromal Bcl-2 expression in conjunction with the presence of lymphocytes for epithelial ovarian tumor progression.</p> <p>Methods</p> <p>Ovarian tissue sections were classified as normal (n = 2), benign (n = 17) or cancerous (n = 28) and immunohistochemically stained for Bcl-2. Bcl-2 expression was assessed according to cellular localization, extent, and intensity of staining. The number of lymphocyte nests as well as the number of lymphocytes within these nests was counted.</p> <p>Results</p> <p>While Bcl-2 staining remained cytoplasmic, both percent and intensity of epithelial and stromal Bcl-2 staining decreased with tumor progression. Further, the number of lymphocyte nests dramatically increased with tumor progression.</p> <p>Conclusion</p> <p>The data suggest alterations in Bcl-2 expression and lymphocyte infiltration correlate with epithelial ovarian cancer progression. Consequently, Bcl-2 expression and lymphocyte status may be important for prognostic outcome or useful targets for therapeutic intervention.</p
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