Analysis of unidirectional non-paraxial invisibility of purely reflective PT-symmetric volume gratings

We study the diffraction produced by a slab of purely reflective PT-symmetric volume Bragg grating that combines modulations of refractive index and gain/loss of the same periodicity with a quarter-period shift between them. Such a complex grating has a directional coupling between the different diffraction orders, which allows us to find an analytic solution for the first three orders of the full Maxwell equations without resorting to the paraxial approximation. This is important, because only with the full equations can the boundary conditions, allowing for the reflections, be properly implemented. Using our solution we analyze unidirectional invisibility of such a grating in a wide variety of configurations.Comment: 17 pages, 11 figures. arXiv admin note: text overlap with arXiv:1412.050

Spatiotemporal control of cellular microenvironments with photonics

Abstract only

A versatile dual spot laser scanning confocal microscopy system for advanced fluorescence correlation spectroscopy analysis in living cell

A fluorescence correlation spectroscopy (FCS) system based on two independent measurement volumes is presented. The optical setup and data acquisition hardware are detailed, as well as a complete protocol to control the location, size and shape of the measurement volumes. A method that allows to monitor independently the excitation and collection efficiency distribution is proposed. Finally, a few examples of measurements that exploit the two spots in static and/or scanning schemes, are reported.Comment: Accepted for publication in Review of Scientific Instrumen

A Nonpolymorphic Class I Gene in the Murine Major Histocompatibility Complex

DNA sequence analysis of a class I gene (QlO), which maps to the Qa2,3 locus in the C57BL/lO (H- 2b haplotype) mouse, reveals that it is almost identical to a cDNA clone (pH16) isolated from a SWR/J (H-2q haplotype) mouse liver cDNA library. Exon 5, in particular, has an unusual structure such that a polypeptide product is unlikely to be anchored in the cell membrane. Our findings suggest that the two sequences are derived from allelic class I genes, which are nonpolymorphic, in contrast to H-2K allelic sequences from the same mice, and they may encode liver-specific polypeptides of unknown function. Our previous studies indicate that the QlO gene is a potential donor gene for the generation of mutations at the H-2K locus by inter-gene transfer of genetic information. Thus the lack of polymorphism in class I genes at the QlO locus implies either that they are not recipients for such exchanges or that selective pressure prevents the accumulation of mutations in genes at this locus

Birds-Eye-View of R.F. Learned and Son Saw Mill, Natchez, Miss.

https://egrove.olemiss.edu/ms_pcards/1141/thumbnail.jp

Tilt angle dependent three-dimensional position detection of a trapped cylindrical particle in a focused laser beam

We investigated theoretically the applicability of an optically trapped cylindrical particle as a local probe in photonic force microscopy. To do this we calculated the far-field scattering from a subwavelength-sized dielectric cylinder in a highly focused laser field. From this we obtained interferometric three-dimensional-position detection signals and compared these to signals calculated for a spherical particle. We have calculated the accuracy to which the position of an optically trapped cylinder can be determined, as a function of the cylinder’s orientational fluctuations. The position accuracy is better than a few nanometers for tilt angle fluctuations up to several degrees. Our study is relevant for trapping experiments, where the influence of angle fluctuations needs to be estimated

Magnetohydrodynamic activity inside a sphere

We present a computational method to solve the magnetohydrodynamic equations in spherical geometry. The technique is fully nonlinear and wholly spectral, and uses an expansion basis that is adapted to the geometry: Chandrasekhar-Kendall vector eigenfunctions of the curl. The resulting lower spatial resolution is somewhat offset by being able to build all the boundary conditions into each of the orthogonal expansion functions and by the disappearance of any difficulties caused by singularities at the center of the sphere. The results reported here are for mechanically and magnetically isolated spheres, although different boundary conditions could be studied by adapting the same method. The intent is to be able to study the nonlinear dynamical evolution of those aspects that are peculiar to the spherical geometry at only moderate Reynolds numbers. The code is parallelized, and will preserve to high accuracy the ideal magnetohydrodynamic (MHD) invariants of the system (global energy, magnetic helicity, cross helicity). Examples of results for selective decay and mechanically-driven dynamo simulations are discussed. In the dynamo cases, spontaneous flips of the dipole orientation are observed.Comment: 15 pages, 19 figures. Improved figures, in press in Physics of Fluid

Thiol density dependent classical potential for methyl-thiol on a Au(111) surface

A new classical potential for methyl-thiol on a Au(111) surface has been developed using density functional theory electronic structure calculations. Energy surfaces between methyl-thiol and a gold surface were investigated in terms of symmetry sites and thiol density. Geometrical optimization was employed over all the configurations while minimum energy and thiol height were determined. Finally, a new interatomic potential has been generated as a function of thiol density, and applications to coarse-grained simulations are presented