17,617 research outputs found
boosting in kernel regression
In this paper, we investigate the theoretical and empirical properties of
boosting with kernel regression estimates as weak learners. We show that
each step of boosting reduces the bias of the estimate by two orders of
magnitude, while it does not deteriorate the order of the variance. We
illustrate the theoretical findings by some simulated examples. Also, we
demonstrate that boosting is superior to the use of higher-order kernels,
which is a well-known method of reducing the bias of the kernel estimate.Comment: Published in at http://dx.doi.org/10.3150/08-BEJ160 the Bernoulli
(http://isi.cbs.nl/bernoulli/) by the International Statistical
Institute/Bernoulli Society (http://isi.cbs.nl/BS/bshome.htm
Conformal symmetry transformations and nonlinear Maxwell equations
We make use of the conformal compactification of Minkowski spacetime
to explore a way of describing general, nonlinear Maxwell fields with conformal
symmetry. We distinguish the inverse Minkowski spacetime
obtained via conformal inversion, so as to discuss a doubled compactified
spacetime on which Maxwell fields may be defined. Identifying with the
projective light cone in -dimensional spacetime, we write two
independent conformal-invariant functionals of the -dimensional Maxwellian
field strength tensors -- one bilinear, the other trilinear in the field
strengths -- which are to enter general nonlinear constitutive equations. We
also make some remarks regarding the dimensional reduction procedure as we
consider its generalization from linear to general nonlinear theories.Comment: 12 pages, Based on a talk by the first author at the International
Conference in Mathematics in honor of Prof. M. Norbert Hounkonnou (October
29-30, 2016, Cotonou, Benin). To be published in the Proceedings, Springer
201
Spectral statistics of the uni-modular ensemble
We investigate the spectral statistics of Hermitian matrices in which the
elements are chosen uniformly from U (1), called the uni-modular ensemble
(UME), in the limit of large matrix size. Using three complimentary methods; a
supersymmetric integration method, a combinatorial graph-theoretical analysis
and a Brownian motion approach, we are able to derive expressions for 1/N
corrections to the mean spectral moments and also analyse the fluctuations
about this mean. By addressing the same ensemble from three different point of
view, we can critically compare their relative advantages and derive some new
results.Comment: 35 pages, 3 figure
Continuous Hawking-Page transitions in Einstein-scalar gravity
We investigate continuous Hawking-Page transitions in Einstein's gravity
coupled to a scalar field with an arbitrary potential in the weak gravity
limit. We show that this is only possible in a singular limit where the
black-hole horizon marginally traps a curvature singularity. Depending on the
subleading terms in the potential, a rich variety of continuous phase
transitions arise. Our examples include second and higher order, including the
Berezinskii-Kosterlitz-Thouless type. In the case when the scalar is dilaton,
the condition for a continuous phase transition lead to (asymptotically)
linear-dilaton background. We obtain the scaling laws of thermodynamic
functions, as well as the viscosity coefficients near the transition. In the
limit of weak gravitational interactions, the bulk viscosity asymptotes to a
universal constant, independent of the details of the scalar potential. As a
byproduct of our analysis we obtain a one-parameter family of kink solutions in
arbitrary dimension d that interpolate between AdS near the boundary and
linear-dilaton background in the deep interior. The continuous Hawking-Page
transitions found here serve as holographic models for normal-to superfluid
transitions.Comment: 35 pages + appendice
Holographic bulk viscosity: GPR vs EO
Recently Eling and Oz (EO) proposed a formula for the holographic bulk
viscosity, in arXiv:1103.1657, derived from the null horizon focusing equation.
This formula seems different from that obtained earlier by Gubser, Pufu and
Rocha (GPR) in arXiv:0806.0407 calculated from the IR limit of the two-point
function of the trace of the stress tensor. The two were shown to agree only
for some simple scaling cases. We point out that the two formulae agree in two
non-trivial holographic theories describing RG flows. The first is the strongly
coupled N=2* gauge theory plasma. The second is the semi-phenomenological model
of Improved Holographic QCD.Comment: 21 pages, 2 figure
Alternative antibody for the detection of CA125 antigen: a European multicenter study for the evaluation of the analytical and clinical performance of the Access (R) OV Monitor assay on the UniCel (R) Dxl 800 Immunoassay System
Background: Cancer antigen CA125 is known as a valuable marker for the management of ovarian cancer. Methods: The analytical and clinical performance of the Access OV Monitor Immunoassay System (Beckman Coulter) was evaluated at five different European sites and compared with a reference system, defined as CA125 on the Elecsys System (Roche Diagnostics). Results: Total imprecision (%CV) of the OV Monitor ranged between 3.1% and 8.8%, and inter-laboratory reproducibility between 4.7% and 5.0%. Linearity upon dilution showed a mean recovery of 100% (SD+8.1%). Endogenous interferents had no influence on OV Monitor levels (mean recoveries: hemoglobin 107%, bilirubin 103%, triglycericles 103%). There was no high-dose hook effect up to 27,193 kU/L. Clinical performance investigated in sera from 1811 individuals showed a good correlation between the Access OV Monitor and Elecsys CA125 (R = 0.982, slope = 0.921, intercept = + 1.951). OV Monitor serum levels were low in healthy individuals (n = 267, median = 9.7 kU/L, 95th percentile = 30.8 kU/L), higher in individuals with various benign diseases (n = 549, medians = 10.9-16.4 kU/L, 95th percentiles = 44.2-355 kU/L) and even higher in individuals suffering from various cancers (n = 995, medians= 12.4-445 kU/L; 95th percentiles = 53.4-4664 kU/L). Optimal diagnostic accuracy for cancer detection against the relevant benign control group by the OV Monitor was found for ovarian cancer {[}area under the curve (AUC) 0.898]. Results for the reference CA125 assay were comparable (AUC 0.899). Conclusions: The Access OV Monitor provides very good methodological characteristics and demonstrates an excellent analytical and clinical correlation with Elecsys CA125. The best diagnostic accuracy for the OV Monitor was found in ovarian cancer. Our results also suggest a clinical value of the OV Monitor in other cancers
Design for non-designers (D4ND)
This article exposes a methodology of design workshops for non-designers (D4ND) developed in an academic context interested in (1) deepening the explanation for what is the design for non-designers and (2) the strategies which may be to provide the tools of design thinking to non-designers. It is not a matter of transposing formal training structures to non-formal training, but rather, to explore new pedagogical processes involving design students to be applied to non-designers. Design is seen here as a discipline supported by an active learning process, critical, and directed towards problem-solving. We use the word design in its broadest sense, contemplating a humanist vision capable of generating social transformations, promoting more democratic actions that aim at a better, more just and equal world. At an individual level, it can empower people (students and non-designers) to increase their quality of life. In the first part, we address the assumption of D4ND project, beginning by describing its goals and identifying its actors. Later we questioned the work process through design and how to create knowledge through the implementation of the workshops. In the second part, we expose the methodology of the exercise of D4ND and present a synthesis of its outputs: five projects. We conclude with an analysis of the outcomes of this pedagogical experience, at the level of the students, as well as the team teachers. Closing this paper with the perspective of the future of the D4ND project.info:eu-repo/semantics/publishedVersio
Human microglial cells synthesize albumin in brain
Albumin has been implicated in Alzheimer's disease since it can bind to and transport amyloid beta, the causative agent; albumin is also a potent inhibitor of amyloid beta polymerization. In a pilot phase study of Human Brain Proteome Project, we found evidence that albumin may be synthesized in immortalized human microglial cells, human primary microglial cells, and human fetal and adult brain tissues. We also found the synthesis and secretion is enhanced upon microglial activation by Amyloid [beta]~1-42~, lipopolysaccharide treatment or human Alzheimer's brain
Shot Noise in Digital Holography
We discuss on noise in heterodyne holography in an off-axis configuration. We
show that, for a weak signal, the noise is dominated by the shot noise on the
reference beam. This noise corresponds to an equivalent noise on the signal
beam of one photoelectron per pixel, for the whole sequence of images used to
build the digital hologram
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