4,976 research outputs found
Pairing effect on the giant dipole resonance width at low temperature
The width of the giant dipole resonance (GDR) at finite temperature T in
Sn-120 is calculated within the Phonon Damping Model including the neutron
thermal pairing gap determined from the modified BCS theory. It is shown that
the effect of thermal pairing causes a smaller GDR width at T below 2 MeV as
compared to the one obtained neglecting pairing. This improves significantly
the agreement between theory and experiment including the most recent data
point at T = 1 MeV.Comment: 8 pages, 5 figures to be published in Physical Review
Dynamical Behavior of a stochastic SIRS epidemic model
In this paper we study the Kernack - MacKendrick model under telegraph noise.
The telegraph noise switches at random between two SIRS models. We give out
conditions for the persistence of the disease and the stability of a disease
free equilibrium. We show that the asymptotic behavior highly depends on the
value of a threshold which is calculated from the intensities of
switching between environmental states, the total size of the population as
well as the parameters of both SIRS systems. According to the value of
, the system can globally tend towards an endemic case or a disease
free case. The aim of this work is also to describe completely the omega-limit
set of all positive solutions to the model. Moreover, the attraction of the
omega-limit set and the stationary distribution of solutions will be pointed
out.Comment: 16 page
Damping of giant dipole resonance in hot rotating nuclei
The phonon damping model (PDM) is extended to include the effect of angular
momentum at finite temperature. The model is applied to the study of damping of
giant dipole resonance (GDR) in hot and noncollectively rotating spherical
nuclei. The numerical results obtained for Mo88 and Sn106 show that the GDR
width increases with both temperature T and angular momentum M. At T > 4 MeV
and M<= 60 hbar the increase in the GDR width slows down for Sn106, whereas at
M<= 80 hbar the GDR widths in both nuclei nearly saturate. By adopting the
nuclear shear viscosity extracted from fission data at T= 0, it is shown that
the maximal value of the angular momentum for Mo88 and Sn106 should be around
46 and 55 hbar, respectively, so that the universal conjecture for the lower
bound of the specific shear viscosity for all fluids is not violated up to T= 5
MeV.Comment: 19 pages, 6 figures, accepted in Phys. Rev.
A Novel Hybrid K-Means and GMM Machine Learning Model for Breast Cancer Detection
Breast cancer is the second leading cause of death among a large number of women worldwide. It may be challenging for radiologists to diagnose and treat breast cancer. Consequently, primary care improves disease prevention and death. Early detection increases treatment options and saves life, which is the major target of this research. This research indicates the versatility of the methodology by integrating contemporary segmentation approaches with machine learning methods, which are developing areas of research. In the pre-processing process, an adaptive median filter is utilized for noise removal, enhancement of image quality, conservation of edges, and smoothing. This research makes a significant contribution by proposing a new parameter for evaluating K-means and a Gaussian mixture model (GMM) performance. A hybrid combination of segmentation and detection was applied to breast cancer. The proposed technique is significant for classifying benign and malignant tumors. The simulated results are discussed and evaluated to determine the competence of this method for the early diagnosis of breast cancer. This method allows medical experts to recognize breast cancer at a faster rate and provide higher accuracy. An ANOVA test was used to determine the multi-variant analysis and prediction rate for the proposed method
A Bogomol`nyi equation for intersecting domain walls
We argue that the Wess-Zumino model with quartic superpotential admits static
solutions in which three domain walls intersect at a junction. We derive an
energy bound for such junctions and show that configurations saturating it
preserve 1/4 supersymmetry.Comment: 4 pages revtex. No figures. Revised version to appear in Physical
Review Letters includes discussion of the supersymmetry algebr
Emergence of Quantum Phase-Slip Behaviour in Superconducting NbN Nanowires: DC Electrical Transport and Fabrication Technologies
Superconducting nanowires undergoing quantum phase-slips have potential for
impact in electronic devices, with a high-accuracy quantum current standard
among a possible toolbox of novel components. A key element of developing such
technologies is to understand the requirements for, and control the production
of, superconducting nanowires that undergo coherent quantum phase-slips. We
present three fabrication technologies, based on using electron-beam
lithography or neon focussed ion-beam lithography, for defining narrow
superconducting nanowires, and have used these to create nanowires in niobium
nitride with widths in the range of 20-250 nm. We present characterisation of
the nanowires using DC electrical transport at temperatures down to 300 mK. We
demonstrate that a range of different behaviours may be obtained in different
nanowires, including bulk-like superconducting properties with critical-current
features, the observation of phase-slip centres and the observation of zero
conductance below a critical voltage, characteristic of coherent quantum
phase-slips. We observe critical voltages up to 5 mV, an order of magnitude
larger than other reports to date. The different prominence of quantum
phase-slip effects in the various nanowires may be understood as arising from
the differing importance of quantum fluctuations. Control of the nanowire
properties will pave the way for routine fabrication of coherent quantum
phase-slip nanowire devices for technology applications.Comment: 14 pages, 8 figure
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