1,803 research outputs found
Face tracking using a hyperbolic catadioptric omnidirectional system
In the first part of this paper, we present a brief review on catadioptric omnidirectional
systems. The special case of the hyperbolic omnidirectional system is analysed in depth.
The literature shows that a hyperboloidal mirror has two clear advantages over alternative
geometries. Firstly, a hyperboloidal mirror has a single projection centre [1]. Secondly, the
image resolution is uniformly distributed along the mirror’s radius [2].
In the second part of this paper we show empirical results for the detection and tracking
of faces from the omnidirectional images using Viola-Jones method. Both panoramic and
perspective projections, extracted from the omnidirectional image, were used for that purpose.
The omnidirectional image size was 480x480 pixels, in greyscale. The tracking method used
regions of interest (ROIs) set as the result of the detections of faces from a panoramic projection
of the image. In order to avoid losing or duplicating detections, the panoramic projection was
extended horizontally. Duplications were eliminated based on the ROIs established by previous
detections. After a confirmed detection, faces were tracked from perspective projections (which
are called virtual cameras), each one associated with a particular face. The zoom, pan and tilt
of each virtual camera was determined by the ROIs previously computed on the panoramic
image.
The results show that, when using a careful combination of the two projections, good frame
rates can be achieved in the task of tracking faces reliably
B\"acklund Transformations of MKdV and Painlev\'e Equations
For there are and actions on the space of solutions of
the first nontrivial equation in the Z_2$ actions on the space of solutions of the standard MKdV equation.
These actions survive scaling reduction, and give rise to transformation groups
for certain (systems of) ODEs, including the second, fourth and fifth
Painlev\'e equations.Comment: 8 pages, plain te
Beyond complex Langevin equations II: a positive representation of Feynman path integrals directly in the Minkowski time
Recently found positive representation for an arbitrary complex, gaussian
weight is used to construct a statistical formulation of gaussian path
integrals directly in the Minkowski time. The positivity of Minkowski weights
is achieved by doubling the number of real variables. The continuum limit of
the new representation exists only if some of the additional couplings tend to
infinity and are tuned in a specific way. The construction is then successfully
applied to three quantum mechanical examples including a particle in a constant
magnetic field -- a simplest prototype of a Wilson line. Further
generalizations are shortly discussed and an intriguing interpretation of new
variables is alluded to.Comment: 16 pages, 2 figures, references adde
Effective spatial dimension of extremal non-dilatonic black p-branes and the description of entropy on the world volume
By investigating the critical behavior appearing at the extremal limit of the
non-dilatonic, black p-branes in (d+p) dimensions, we find that some critical
exponents related to the critical point obey the scaling laws. From the scaling
laws we obtain that the effective spatial dimension of the non-dilatonic black
holes and black strings is one, and is p for the non-dilatonic black p-branes.
For the dilatonic black holes and black p-branes, the effective dimension will
depend on the parameters in theories. Thus, we give an interpretation why the
Bekenstein-Hawking entropy may be given a simple world volume interpretation
only for the non-dilatonic black p-branes.Comment: 4 pages, RevTex, no figures, to appear in Phys. Rev. Let
Non-monotonic magnetic field and density dependence of in-plane magnetoresistance in dilute two-dimensional holes in GaAs/AlGaAs
We studied low temperature (T=50mK) in-plane magnetoresistance of a dilute
two-dimensional hole system in GaAs/AlGaAs heterostructure that exhibits an
apparent metal-insulator transition. We found an anisotropic magnetoresistance,
which changes dramatically at high in-plane fields (B_{\parallel}\agt5T) as
the hole density is varied. At high densities where the system behaves metallic
at , the transverse magnetoresistance is larger than the
longitudinal magnetoresistance. With decreasing the hole density the difference
becomes progressively smaller, and at densities near the "critical" density and
lower, the longitudinal magnetoresistance becomes larger than the transverse
magnetoresistance
Fecal occult blood and fecal calprotectin as point-of-care markers of intestinal morbidity in Ugandan children with Schistosoma mansoni infection.
BACKGROUND: Calprotectin is a calcium-binding cytoplasmic protein found in neutrophils and increasingly used as a marker of bowel inflammation. Fecal occult blood (FOB) is also a dependable indicator of bowel morbidity. The objective of our study was to determine the applicability of these tests as surrogate markers of Schistosoma mansoni intestinal morbidity before and after treatment with praziquantel (PZQ).
METHODS: 216 children (ages 3-9 years old) from Buliisa District in Lake Albert, Uganda were examined and treated with PZQ at baseline in October 2012 with 211 of them re-examined 24 days later for S. mansoni and other soil transmitted helminths (STH). POC calprotectin and FOB assays were performed at both time points on a subset of children. Associations between the test results and infection were analysed by logistic regression.
RESULTS: Fecal calprotectin concentrations of 150-300 µg/g were associated with S. mansoni egg patent infection both at baseline and follow up (OR: 12.5 P = 0.05; OR: 6.8 P = 0.02). FOB had a very strong association with baseline anemia (OR: 9.2 P = 0.03) and medium and high egg intensity schistosomiasis at follow up (OR: 6.6 P = 0.03; OR: 51.3 P = 0.003). Both tests were strongly associated with heavy intensity S. mansoni infections. There was a significant decrease in FOB and calprotectin test positivity after PZQ treatment in those children who had egg patent schistosomiasis at baseline.
CONCLUSIONS: Both FOB and calprotectin rapid assays were found to correlate positively and strongly with egg patent S. mansoni infection with a positive ameloriation response after PZQ treatment indicative of short term reversion of morbidity. Both tests were appropriate for use in the field with excellent operational performance and reliability. Due to its lower-cost which makes its scale-up of use affordable, FOB could be immediately adopted as a monitoring tool for PC campaigns for efficacy evaluation before and after treatment
Composite nucleons in scalar and vector mean-fields
We emphasize that the composite structure of the nucleon may play quite an
important role in nuclear physics. It is shown that the momentum-dependent
repulsive force of second order in the scalar field, which plays an important
role in Dirac phenomenology, can be found in the quark-meson coupling (QMC)
model, and that the properties of nuclear matter are well described through the
quark-scalar density in a nucleon and a self-consistency condition for the
scalar field. The difference between theories of point-like nucleons and
composite ones may be seen in the change of the -meson mass in nuclear
matter if the composite nature of the nucleon suppresses contributions from
nucleon-antinucleon pair creation.Comment: 10 page
The specificity and patterns of staining in human cells and tissues of p16INK4a antibodies demonstrate variant antigen binding
The validity of the identification and classification of human cancer using antibodies to detect biomarker proteins depends upon antibody specificity. Antibodies that bind to the tumour-suppressor protein p16INK4a are widely used for cancer diagnosis and research. In this study we examined the specificity of four commercially available anti-p16INK4a antibodies in four immunological applications. The antibodies H-156 and JC8 detected the same 16 kDa protein in western blot and immunoprecipitation tests, whereas the antibody F-12 did not detect any protein in western blot analysis or capture a protein that could be recognised by the H-156 antibody. In immunocytochemistry tests, the antibodies JC8 and H-156 detected a predominately cytoplasmic localised antigen, whose signal was depleted in p16INK4a siRNA experiments. F-12, in contrast, detected a predominately nuclear located antigen and there was no noticeable reduction in this signal after siRNA knockdown. Furthermore in immunohistochemistry tests, F-12 generated a different pattern of staining compared to the JC8 and E6H4 antibodies. These results demonstrate that three out of four commercially available p16INK4a antibodies are specific to, and indicate a mainly cytoplasmic localisation for, the p16INK4a protein. The F-12 antibody, which has been widely used in previous studies, gave different results to the other antibodies and did not demonstrate specificity to human p16INK4a. This work emphasizes the importance of the validation of commercial antibodies, aside to the previously reported use, for the full verification of immunoreaction specificity
The Field-Tuned Superconductor-Insulator Transition with and without Current Bias
The magnetic-field-tuned superconductor-insulator transition has been studied
in ultrathin Beryllium films quench-condensed near 20 K. In the zero-current
limit, a finite-size scaling analysis yields the scaling exponent product vz =
1.35 +/- 0.10 and a critical sheet resistance R_{c} of about 1.2R_{Q}, with
R_{Q} = h/4e^{2}. However, in the presence of dc bias currents that are smaller
than the zero-field critical currents, vz becomes 0.75 +/- 0.10. This new set
of exponents suggests that the field-tuned transitions with and without dc bias
currents belong to different universality classes.Comment: RevTex 4 pages, 4 figures, and 1 table minor change
Up-Down Quark Mass Difference Effect in Nuclear Many-Body Systems
A charge-symmetry-breaking nucleon-nucleon force due to the up-down quark
mass difference is evaluated in the quark cluster model. It is applied to the
shell-model calculation for the isovector mass shifts of isospin multiplets and
the isospin-mixing matrix elements in 1s0d-shell nuclei. We find that the
contribution of the quark mass difference effect is large and agrees with
experiment. This contribution may explain the Okamoto-Nolen-Schiffer anomaly,
alternatively to the meson-mixing contribution, which is recently predicted to
be reduced by the large off-shell correction
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