11,308 research outputs found
CPV tests with rare kaon decays
The K_S \to pi+/- e+ e- decay mode has been investigated using the data
collected in 2002 by the NA48/1 collaboration. With about 23k signal events and
59k K_L \to pi+ pi- pi0_D normalization decays, the K_S \to pi+ pi- e+ e-
branching ratio was determined. This result is also used to set an upper limit
on the presence of E1 direct emission in the decay amplitude. The CP-violating
asymmetry has been also measured.
We report on measurements of the rare decays K +/- \to pi+/- e+ e- and K+/-
\to pi+/- mu+ mu- . The full NA48/2 data set was analyzed, leading to more than
7200 reconstructed events in the electronic and more than 3000 events in the
muonic channel, the latter exceeding the total existing statistics by a factor
of four. For both channels the selected events are almost background-free. From
these events, we have determined the branching fraction and form factors of
K+/- \to pi+/- e+ e- using different theoretical models. Our results improve
the existing world averages significantly. In addition, we measured the CP
violating asymmetry between K+ and K- in this channel to be less than a few
percent.Comment: 4 pages, 1 figure, To appear in the proceedings of IX International
Conference on Hyperons, Charm and Beauty Hadrons (BEACH2010), Perugia, Italy,
21-26 June 201
Minimalistic Unsupervised Learning with the Sparse Manifold Transform
We describe a minimalistic and interpretable method for unsupervised
learning, without resorting to data augmentation, hyperparameter tuning, or
other engineering designs, that achieves performance close to the SOTA SSL
methods. Our approach leverages the sparse manifold transform, which unifies
sparse coding, manifold learning, and slow feature analysis. With a one-layer
deterministic sparse manifold transform, one can achieve 99.3% KNN top-1
accuracy on MNIST, 81.1% KNN top-1 accuracy on CIFAR-10 and 53.2% on CIFAR-100.
With a simple gray-scale augmentation, the model gets 83.2% KNN top-1 accuracy
on CIFAR-10 and 57% on CIFAR-100. These results significantly close the gap
between simplistic ``white-box'' methods and the SOTA methods. Additionally, we
provide visualization to explain how an unsupervised representation transform
is formed. The proposed method is closely connected to latent-embedding
self-supervised methods and can be treated as the simplest form of VICReg.
Though there remains a small performance gap between our simple constructive
model and SOTA methods, the evidence points to this as a promising direction
for achieving a principled and white-box approach to unsupervised learning
Polarization anisotropy in the optical properties of silicon ellipsoids
A new real space quantum mechanical approach with local field effects
included is applied to the calculation of the optical properties of silicon
nanocrystals. Silicon ellipsoids are studied and the role of surface
polarization is discussed in details. In particular, surface polarization is
shown to be responsible for a strong optical anisotropy in silicon ellipsoids,
much more pronounced with respect to the case in which only quantum confinement
effects are considered. The static dielectric constant and the absorption
spectra are calculated, showing that the perpendicular and parallel components
have a very different dependence on the ellipsoid aspect ratio. Then, a
comparison with the classical dielectric model is performed, showing that the
model only works for large and regular structures, but it fails for thin
elongated ellipsoids.Comment: 5 pages, 4 figures, International Conference on NANO-Structures
Self-Assemblin
HI intensity mapping with FAST
We discuss the detectability of large-scale HI intensity fluctuations using
the FAST telescope. We present forecasts for the accuracy of measuring the
Baryonic Acoustic Oscillations and constraining the properties of dark energy.
The FAST -beam L-band receivers (-- GHz) can provide
constraints on the matter power spectrum and dark energy equation of state
parameters () that are comparable to the BINGO and CHIME
experiments. For one year of integration time we find that the optimal survey
area is . However, observing with larger frequency coverage
at higher redshift (-- GHz) improves the projected errorbars on the
HI power spectrum by more than confidence level. The combined
constraints from FAST, CHIME, BINGO and Planck CMB observations can provide
reliable, stringent constraints on the dark energy equation of state.Comment: 7 pages, 3 figures, submitted to "Frontiers in Radio Astronomy and
FAST Early Sciences Symposium 2015" conference proceedin
Pt decorated amorphous RuIr alloys as high efficiency electrocatalyst for methanol oxidation
This study focuses primarily on improving the utilization and
activity of anodic catalysts for methanol electro-oxidation. The
Direct Methanol Fuel Cell (DMFC) anodic catalyst, a carbon
supported Pt decorated amorphous RuIr nanoparticles catalyst
(Pt@RuIr/C) was prepared by a two-step reduction method. The
structure of Pt@RuIr/C nanoparticles was confirmed by
Transmission Electron Microscopy (TEM) and X-ray Diffraction
(XRD). The Pt@RuIr electrocatalysts exhibited good uniformity in
distribution. Cyclic Voltammetry experiments showed that under
the same quality of noble-metal, the Pt@RuIr/C catalyst had higher
activity than the PtRuIr/C catalyst for methanol oxidation. It was
also shown that the as-prepared structure of the Pt decorated
amorphous RuIr alloys could obviously decrease the usage of
noble-metal and enhance its catalytic activity at the same time.Web of Scienc
Enzymatic and genetic polymorphisms of paraoxonase- 1 in the Gabonese population: The relation to lipid parameters in patients with diabetes
Background: The objective was to study the relationship between the paraoxonase-1 activity, genetic polymorphisms and lipid parameters in a black patient population.Method: This study investigates patients with type 2 diabetes and hypertension for which concentrations of total high-density lipoprotein (HDL) and low-density lipoprotein (LDL) cholesterol, triglycerides, apolipoprotein AI, apolipoprotein B100, the latency time of oxidation of small and dense LDL, arylesterase activity and genetic polymorphism of paraoxonase-1 at positions T(-107)C, L55M and Q192R were determined and compared to healthy subjects.Results: Concerning the T(-107C) polymorphism, the -107T allele is higher in healthy subjects (0.325) than in those with diabetes (0.660). This was the same for the 55M allele, whereas the -107C allele was lower in healthy patients (0.675) than in patients with diabetes (0.340). Paraoxonase-1 activity was lower in patients with diabetes than in healthy subjects, irrespective of genotype. The -107CC genotypes had higher HDL cholesterol AI apolipoprotein I concentrations than -107TT in the control group (p-value = 0.0001), patients with diabetes (p-value = 0.002), and patients with hyptertension (p-value = 0.001). This result was also obtained with the 55LL genotype.Conclusion: The prevalence of paraoxonase-1 alleles associated with lesser enzyme activities was found to be more common in patients with diabetes than in the control group. Possibly, this genetic distribution contributes to the high cardiovascular risk that is observed in certain black patients, compared to that in white patients
Atomically precise lateral modulation of a two-dimensional electron liquid in anatase TiO2 thin films
Engineering the electronic band structure of two-dimensional electron liquids
(2DELs) confined at the surface or interface of transition metal oxides is key
to unlocking their full potential. Here we describe a new approach to tailoring
the electronic structure of an oxide surface 2DEL demonstrating the lateral
modulation of electronic states with atomic scale precision on an unprecedented
length scale comparable to the Fermi wavelength. To this end, we use pulsed
laser deposition to grow anatase TiO2 films terminated by a (1 x 4) in-plane
surface reconstruction. Employing photo-stimulated chemical surface doping we
induce 2DELs with tunable carrier densities that are confined within a few TiO2
layers below the surface. Subsequent in-situ angle resolved photoemission
experiments demonstrate that the (1 x 4) surface reconstruction provides a
periodic lateral perturbation of the electron liquid. This causes strong
backfolding of the electronic bands, opening of unidirectional gaps and a
saddle point singularity in the density of states near the chemical potential
El sabotaje durante la Guerra Civil: la industria naval de Cartagena
Anàlisi del sabotatge dut a terme a l'Arsenal i la factoria cartagenera de la Societat Espanyola de Construcció Naval, un sector estratègic per a la defensa de la República, atesa la seva significació en el manteniment de la flota i la producció armamentística. Queden de manifest l'àmplia xarxa quintacolumnista, el desenvolupament i les actuacions, i es pot deduir la contribució a la derrota republicana.Analysis of the sabotage carried out in the Arsenal and the Cartagena factory of the Spanish Shipbuilding Society, a strategic sector for the defense of the Republic, given its significance in fleet maintenance and arms production. The extensive fifth columnist network, its development and actions are evident, and its contribution to the republican defeat can be deduced.Análisis del sabotaje llevado a cabo en el Arsenal y la factoría cartagenera de la Sociedad Española de Construcción Naval, un sector estratégico para la defensa de la República, dada su significación en el mantenimiento de la flota y la producción armamentística. Quedan de manifiesto la amplia red quintacolumnista, su desarrollo y actuaciones, pudiendo deducirse su contribución a la derrota republicana
Light management in highly-textured perovskite solar cells: From full-device ellipsometry characterization to optical modelling for quantum efficiency optimization
While perovskite solar cells (PSCs) are now reaching high power conversion
efficiencies (PCEs), further performance improvement requires a fine management
and an optimization of the light pathway and harvesting in the cells. These go
through an accurate understanding, characterization and modelling of the
optical processes occurring in these complex, often textured, multi-layered
systems. In the present work, we have considered a typical methylammonium lead
iodide (MAPI) solar cell built on a fluorine-doped tin oxide (FTO) electrode of
high roughness (43 nm RMS). By variable-angle spectroscopic ellipsometry (VASE)
of the full PSC device, we have been able to determine the optical constants of
all the device layers. We have designed a one-dimensional (1D) optical model of
the stacked layers where the rough texture is described as layers of
effective-medium index. We have supported the model using data extracted from
scanning electron microscopy, diffuse spectroscopy and photovoltaic efficiency
measurements. We show that the 1D model, while insufficient to describe
scattering by the FTO plate alone, gives an accurate description of the full
device optical properties. By comparison with the experimental external quantum
efficiency (EQE), we estimate the internal quantum efficiency (IQE) and the
effect of the losses related to electron transfer. Based on this work, we
finally discuss the optical losses mechanisms and the possible strategies that
can be implemented to improve light management within PSC devices and further
increase their performances.Comment: 14 pages, 5 figure
Reduction of 400 GeV / c slow extraction beam loss with a wire diffuser at the CERN Super Proton Synchrotron
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