735 research outputs found
Current relaxation in nonlinear random media
We study the current relaxation of a wave packet in a nonlinear random sample
coupled to the continuum and show that the survival probability decays as . For intermediate times , the exponent
satisfies a scaling law where is
the nonlinearity strength and is the localization length of the
corresponding random system with . For and we find a universal decay with which is a signature of the
{\it nonlinearity-induced delocalization}. Experimental evidence should be
observable in coupled nonlinear optical waveguides.Comment: revised version, PRL in press, 4 pages, 4 figs (fig 3 with reduced
quality
Reversing conditional orderings
We analyze some specific aspects concerning conditional orderings and relations among them. To this purpose we define a suitable concept of reversed conditional ordering and prove some related results. In particular we aim to compare the univariate stochastic orderings ≤ st, ≤ hr, and ≤ lr in terms of differences among different notions of conditional orderings. Some applications of our result to the analysis of positive dependence will be detailed. We concentrate attention to the case of a pair of scalar random variables X, Y . Suitable extensions to multivariate cases are possible
The signature of subsurface Kondo impurities in the local tunnel current
The conductance of a tunnel point-contact in an STM-like geometry having a
single defect placed below the surface is investigated theoretically. The
effect of multiple electron scattering by the defect after reflections by the
metal surface is taken into account. In the approximation of s-wave scattering
the dependence of the conductance on the applied voltage and the position of
the defect is obtained. The results are illustrated for a model s-wave phase
shift describing Kondo-resonance scattering. We demonstrate that multiple
electron scattering by the magnetic impurity plays a decisive role in the
point-contact conductance at voltages near the Kondo resonance. We find that
the sign and shape of the Kondo anomaly depends on the position of the defect.Comment: 13 pages, 4 figures. To be published in J. Phys.: Cond. Ma
Detection of high-risk human papillomavirus RNA in urine for cervical cancer screening with HPV 16 & 18/45 genotyping
© 2020 The Authors Objective: To detect high-risk human papillomavirus (hrHPV) messenger-RNA (mRNA) in urine samples, compare their concordance with cervical samples including HPV 16 & 18/45 genotyping, and to determine the utility in detecting ≥ CIN 2 lesions. Methods: A cohort of 189 non-pregnant patients (age ≥ 25) was recruited in three groups: Group 1 with abnormal pap-smears and hrHPV positivity, Group 2 with normal pap-smears and hrHPV positivity, and Group 3 with normal pap-smears and hrHPV negativity. Urine samples were tested for hrHPV-mRNA and subsequent hrHPV-mRNA genotype if positive. High-risk HPV detection and genotyping were performed using Aptima assays which are validated for cervical HPV testing. Colposcopy results from groups 1 & 2 were analyzed. Results: The sensitivity of urine hrHPV-mRNA detection was 31.5% while the specificity and PPV were above 95% (96.9% & 95.1% respectively) (p \u3c 0.001). The kappa agreement with cervical samples was fair (0.22, p = 0.04). The sensitivity and specificity of urine hrHPV-mRNA genotyping were 20.0% & 100% respectively (p \u3c 0.001) with 100% genotype-specific concordance. The kappa agreement with cervical samples was fair (0.25, p = 0.16). For urine hrHPV-mRNA detection of ASC-H/HSIL when grouped by age ≥ 30, the sensitivity and specificity were 45.4% & 63.9% respectively (p = 0.009). For urine hrHPV-mRNA detection of ≥ CIN 2 for all ages, the sensitivity and specificity were 45.5% & 75.0% respectively (p = 0.03). Conclusion: Using the Aptima Assay, urine hrHPV-mRNA detection is suboptimal for cervical cancer screening but given the high specificity, it has the potential to identify high-grade lesions (≥ CIN 2). Urine hrHPV-mRNA genotyping via this modality is not beneficial in triage settings of normal or abnormal cytology to determine the need for colposcopy
Severe acute respiratory syndrome coronavirus 2 antibodies in pregnant women admitted to labor and delivery units.
Generalized Ladder Operators for Shape-invariant Potentials
A general form for ladder operators is used to construct a method to solve
bound-state Schr\"odinger equations. The characteristics of supersymmetry and
shape invariance of the system are the start point of the approach. To show the
elegance and the utility of the method we use it to obtain energy spectra and
eigenfunctions for the one-dimensional harmonic oscillator and Morse potentials
and for the radial harmonic oscillator and Coulomb potentials.Comment: in Revte
Analysis of the structure and mechanical properties in medical alloys based on titanium and cobalt manufactured by selective laser melting
Comparative analysis of the structure and internal stress in Ti-6Al-4V alloys manufactured by 3D printing and processing with screw extrusion
Study is based on the compare characterization of the structure and evaluation of the residual internal stresses in Ti-6Al-4V samples manufactured by the 3D printing (selective laser melting) and in the Ti-6Al-4V samples obtained with using of the severe plastic deformation by screw extrusion. The microstructure and residual stresses were examined by transmission electron microscope and X-ray diffractometer. High tensile internal residual stresses in the 3D printed sample were found. The high compressive residual internal stresses were found in the hot pressed and in the twisted samples. It was shown that arising of the high residual stresses in the studied samples under various technological processes occurred in various ways. The residual stresses in the severe plastic deformed samples arose due to non-uniform volumetric plastic deformation. In 3D printed sample, the residual tensile stresses arose from both phase (martensitic) transformation and thermal deformation. © Published under licence by IOP Publishing Ltd
Magnetic properties of polymerized C with Fe
We provide evidence that high-pressure high-temperature (2.5 GPa and 1040 K)
treatment of mixtures of iron with fullerene powders leads to the complete
transformation of iron into iron carbide FeC. The comparison of the
magnetic properties (Curie temperature and magnetic moment) of the here studied
samples and those for the ferromagnetic polymer Rh-C indicates that the
main ferromagnetic signal reported in those samples is due to FeC and not
related to the ferromagnetism of carbon as originally interpreted. Taking into
account the results obtained in this study the original paper on ``Magnetic
carbon" (Nature {\bf 413}, 716 (2001)) was recently retracted.Comment: 5 Figures, 4 page
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