4,134 research outputs found
Scattering mechanism in a step-modulated subwavelength metal slit: a multi-mode multi-reflection analysis
In this paper, the scattering/transmission inside a step-modulated
subwavelength metal slit is investigated in detail. We firstly investigate the
scattering in a junction structure by two types of structural changes. The
variation of transmission and reflection coefficients depending on structural
parameters are analyzed. Then a multi-mode multi-reflection model based on ray
theory is proposed to illustrate the transmission in the step-modulated slit
explicitly. The key parts of this model are the multi-mode excitation and the
superposition procedure of the scatterings from all possible modes, which
represent the interference and energy transfer happened at interfaces. The
method we use is an improved modal expansion method (MEM), which is a more
practical and efficient version compared with the previous one [Opt. Express
19, 10073 (2011)]. In addition, some commonly used methods, FDTD, scattering
matrix method, and improved characteristic impedance method, are compared with
MEM to highlight the preciseness of these methods.Comment: 25 pages, 9 figure
Investigation of Artifact Contamination Impact on EEG Oscillations Towards Enhanced Motor Function Characterization
The significant advancements in electroencephalography (EEG)-driven technology have led to its widespread use in assessing stroke-related conditions. Over the years, various studies have explored the potential of EEG oscillatory patterns in neurological research, with several of them giving limited attention to the signal processing techniques employed, precluding a proper understanding of EEG oscillatory patterns under various conditions. To resolve this issue, we systematically investigated how artifacts impact EEG oscillatory rhythms associated with upper limb movement-related tasks. Thus, the EEG signals of motor tasks were acquired non-invasively from healthy subjects and processed using automated artifact-attenuation methods. Subsequently, the Mu and Beta bands in the brain's motor cortex region were extracted through time-frequency analysis and analyzed using relevant metrics. Experimental results revealed that artifacts in EEG would substantially influence the brain activation strength and response during motor tasks. Notably, signals preprocessed with Reduction of Electroencephalographic Artifacts based on Multi Wiener Filter and Enhanced Wavelet Independent Component Analysis (RELAX_MWF_wICA) showed better brain responses and high task classification performance compared to other methods and the raw signal across motor tasks. This study's findings revealed that the choice of signal processing technique is crucial, as it would influence its analysis and interpretation, thus highlighting the need for careful consideration and usage
The Victoria west: Earliest prepared core technology in the acheulean at canteen kopje and implications for the cognitive evolution of early hominids
Prepared core technology illustrates in-depth planning and the presence of a mental template during the core reduction process. This technology is, therefore, a significant indicator in studying the evolution of abstract thought and the cognitive abilities of hominids. Here, we report on Victoria West cores excavated from the Canteen Kopje site in central South Africa, with a preliminary age estimate of approximately 1Ma (million years ago) for these cores. Technological analysis shows that the VictoriaWest cores bear similarities to the âVolumetric Conceptâ as defined for the Levallois, a popular and widely distributed prepared core technology from at least 200 ka (thousand years ago). Although these similarities are present, several notable differences also occur that make the Victoria West a unique and distinctive prepared core technology; these are: elongated and convergent core shapes, consistent blow directions for flake removal, a predominance of large side-struck flakes, and the use of these flakes to make Acheulean large cutting tools. This innovative core reduction strategy at Canteen Kopje extends the roots of prepared core technology to the latter part of the Early Acheulean and clearly demonstrates an increase in the cognitive abilities and complexities of hominids in this time period.EM201
Effects of color superconductivity on the structure and formation of compact stars
We show that if color superconducting quark matter forms in hybrid or quark
stars it is possible to satisfy most of recent observational boundaries on
masses and radii of compact stellar objects. An energy of the order of
erg is released in the conversion from a (metastable) hadronic star
into a (stable) hybrid or quark star in presence of a color superconducting
phase. If the conversion occurs immediately after the deleptonization of the
proto-neutron star, the released energy can help Supernovae to explode. If the
conversion is delayed the energy released can power a Gamma Ray Burst. A delay
between the Supernova and the subsequent Gamma Ray Burst is possible, in
agreement with the delay proposed in recent analysis of astrophysical data.Comment: 4 pages, 2 figures. To be published in Phys.Rev.
Strange Stars with a Density-Dependent Bag Parameter
We have studied strange quark stars in the framework of the MIT bag model,
allowing the bag parameter B to depend on the density of the medium. We have
also studied the effect of Cooper pairing among quarks, on the stellar
structure. Comparison of these two effects shows that the former is generally
more significant. We studied the resulting equation of state of the quark
matter, stellar mass-radius relation, mass-central-density relation,
radius-central-density relation, and the variation of the density as a function
of the distance from the centre of the star. We found that the
density-dependent B allows stars with larger masses and radii, due to
stiffening of the equation of state. Interestingly, certain stellar
configurations are found to be possible only if B depends on the density. We
have also studied the effect of variation of the superconducting gap parameter
on our results.Comment: 23 pages, 8 figs; v2: 25 pages, 9 figs, version to be published in
Phys. Rev. (D
A utility approach to individualized optimal dose selection using biomarkers
In many settings, including oncology, increasing the dose of treatment results in both increased efficacy and toxicity. With the increasing availability of validated biomarkers and prediction models, there is the potential for individualized dosing based on patient specific factors. We consider the setting where there is an existing dataset of patients treated with heterogenous doses and including binary efficacy and toxicity outcomes and patient factors such as clinical features and biomarkers. The goal is to analyze the data to estimate an optimal dose for each (future) patient based on their clinical features and biomarkers. We propose an optimal individualized dose finding rule by maximizing utility functions for individual patients while limiting the rate of toxicity. The utility is defined as a weighted combination of efficacy and toxicity probabilities. This approach maximizes overall efficacy at a prespecified constraint on overall toxicity. We model the binary efficacy and toxicity outcomes using logistic regression with dose, biomarkers and doseâbiomarker interactions. To incorporate the large number of potential parameters, we use the LASSO method. We additionally constrain the dose effect to be nonânegative for both efficacy and toxicity for all patients. Simulation studies show that the utility approach combined with any of the modeling methods can improve efficacy without increasing toxicity relative to fixed dosing. The proposed methods are illustrated using a dataset of patients with lung cancer treated with radiation therapy.Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/154301/1/bimj2068.pdfhttps://deepblue.lib.umich.edu/bitstream/2027.42/154301/2/bimj2068_am.pd
Negative time delay for wave reflection from a one-dimensional semi-harmonic well
It is reported that the phase time of particles which are reflected by a
one-dimensional semi-harmonic well includes a time delay term which is negative
for definite intervals of the incoming energy. In this interval, the absolute
value of the negative time delay becomes larger as the incident energy becomes
smaller. The model is a rectangular well with zero potential energy at its
right and a harmonic-like interaction at its left.Comment: 6 pages, 5 eps figures. Talk presented at the XXX Workshop on
Geometric Methods in Physics, Bialowieza, Poland, 201
Temperature dependence of the excitonic insulator phase model in 1T-TiSe2
Recently, detailed calculations of the excitonic insulator phase model
adapted to the case of 1\textit{T}-TiSe have been presented. Through the
spectral function theoretical photoemission intensity maps can be generated
which are in very good agreement with experiment [Phys. Rev. Lett. {\bf 99},
(2007) 146403]. In this model, excitons condensate in a BCS-like manner and
give rise to a charge density wave, characterized by an order parameter. Here,
we assume an analytical form of the order parameter, allowing to perform
temperature dependent calculations. The influence of this order parameter on
the electronic spectral function, to be observed in photoemission spectra, is
discussed. The resulting chemical potential shift and an estimation of the
resistivity are also shown.Comment: 4 pages, 3 figures, paper submitted at the Strongly Correlated
Electron System conference, Brazil, 200
What information can we obtain from the yield ratio in heavy-ion collisions ?
The recently reported data on the yield ratio in central
rapidity region of heavy-ion collisions are analyzed by theoretical formula
which accounts for Coulomb interaction between central charged fragment (CCF)
consisting of nearly stopped nucleons with effective charge
Z_{\mbox{\scriptsize eff}} and charged pions produced in the same region of
the phase space. The Coulomb wave function method is used instead of the usual
Gamow factor in order to account for the finite production range of pions,
. For Gaussian shape of the pion production sources it results in a
quasi-scaling in and Z_{\mbox{\scriptsize eff}} which makes
determination of parameters and Z_{\mbox{\scriptsize eff}} from the
existing experimental data difficult. Only sufficiently accurate data taken in
the extreme small - region, where this
quasi-scaling is broken, could be used for this purpose.Comment: 7 pages, Latex type, 8 figure
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