Alternative derivation of Mie theory with electromagnetic potentials for diffuse particles

Mie's theory of light scattering on spherical particles is being increasingly used in nanophotonics, and these demanding applications have laid bare some shortcomings of Mie theory in its standard formulation. One problem that deserves special attention is the electron spill-out in small metallic nanoparticles, which invalidates the assumption of an abrupt interface. Here we present an alternative derivation of Mie theory without this assumption. To avoid the usual electromagnetic boundary conditions suitable for a hard-wall interface, we set up equations for the electromagnetic potentials instead of the electric and magnetic field. We show that in the limit of a hard-wall interface, the results of the standard Mie theory are recovered. Additionally, a numerical solution scheme is proposed for the equations for the vector potential and the scalar potential. Analysis of the optical cross sections of soft-interface nanospheres shows that the absorption increases and occurs at lower frequencies as compared to hard-walled nanospheres. This effect is rather dramatic in large spheres with large spill-out, due to the disappearance of high-frequency resonance peaks

Fano resonances in plasmonic core-shell particles and the Purcell effect

Despite a long history, light scattering by particles with size comparable with the light wavelength still unveils surprising optical phenomena, and many of them are related to the Fano effect. Originally described in the context of atomic physics, the Fano resonance in light scattering arises from the interference between a narrow subradiant mode and a spectrally broad radiation line. Here, we present an overview of Fano resonances in coated spherical scatterers within the framework of the Lorenz-Mie theory. We briefly introduce the concept of conventional and unconventional Fano resonances in light scattering. These resonances are associated with the interference between electromagnetic modes excited in the particle with different or the same multipole moment, respectively. In addition, we investigate the modification of the spontaneous-emission rate of an optical emitter at the presence of a plasmonic nanoshell. This modification of decay rate due to electromagnetic environment is referred to as the Purcell effect. We analytically show that the Purcell factor related to a dipole emitter oriented orthogonal or tangential to the spherical surface can exhibit Fano or Lorentzian line shapes in the near field, respectively.Comment: 28 pages, 10 figures; invited book chapter to appear in "Fano Resonances in Optics and Microwaves: Physics and Application", Springer Series in Optical Sciences (2018), edited by E. O. Kamenetskii, A. Sadreev, and A. Miroshnichenk

The survey of central obesity and BMI associated with different phenotypes of polycystic ovary syndrome in adolescents

Introduction: Adipose tissue distribution is effective in metabolic complications resulting from obesity. The present study aimed to determine the prevalence of obesity and android obesity based on various phenotypes of Polycystic Ovarian Syndrome (PCOS) in 14–18 year old high-school female students in Shiraz in 2009. Methods: This descriptive study was conducted on 14–18 years old high-school girl in Shiraz in 2009. 3190-Subject sample size was determined. After obtaining written informed consents, demographic information questionnaire was completed and the participants were examined regarding hirsutism, acne, alopecia, and menstrual disorders. Besides, the criteria proposed by Adams et al. were employed to diagnose PCOS in sonography. Android obesity and BMI were evaluated. Then, the data were entered into the SPSS software (v. 11.5) and analyzed. Results: The participants’ mean weight, mean height, and mean waist circumference were 54.14 ± 9.99 kg, 160.20 ± 5.76 cm, and 65.24 ± 7.34 cm, respectively. In addition, 616 participants (20.5%) were underweight, 234 (9.5%) were overweight, and 110 (3.5%) were obese. Also, 15 participants (0.5%) had android obesity. The results of independent t-test showed no significant difference among various phenotypes of PCOS regarding mean android obesity and BMI (P > 0.05). Overall, 16.6% of the study participants (514 subjects) suffered from menstrual disorders and oligomenorrhea. Also, 99 participants (3.1%) had BMI ⩾ 26. Conclusion: The results revealed no significant relationship between female adolescents’ obesity and various phenotypes of PCOS. However, adolescents should be informed about the long-term hyperandrogenic outcomes which are accompanied by insulin secretion and endanger their health after the age of 40 years