Natural-frequency splitting of a guitar string caused by a non-uniform magnetic field.

A magnet can affect the vibration of the metal strings in a musical instrument. Here it is shown that a magnetic field can cause splitting of a metal guitar string's normally degenerate transverse vibration modes, leading to a beat note in the resulting sound. A distributed-spring model accurately predicts the natural frequencies of a vibrating guitar string in the non-uniform magnetic field.

Analysis of light scattering by red blood cells in ektacytometry using global pattern fitting.

Ektacytometry measures the shape of red blood cells under shear stress by analyzing the diffraction pattern of laser light passing through a thin layer of suspended cells. Here we model the diffraction pattern using a combination of Bessel and anomalous scattering functions, and employ a global pattern-fitting technique over nine different shear stresses to determine the separate mechanical properties of normal and non-deformable cells. This technique is capable of yielding the correct elongation index of the normal cells over a range of shear stresses even when they are mixed with as much as 50% non-deformable cells. Additionally, the relative concentrations of normal and non-deformable cells can be determined.

Rewritable densification gratings in boron-doped fibers.

We show that the strength of long-period gratings recorded in boron-doped fibers by CO2 radiation can be significantly enhanced by a uniform pre-exposure by the same laser. The resultant gratings could be erased by a similar uniform exposure and then recorded again multiple times with no loss of fiber sensitivity. We suggest that such gratings are formed by reversible densification of the fiber core. These densification gratings have higher thermal stability than gratings written with ultraviolet light.