Control of the Onset of Filamentation in Condensed Media

Propagation of intense, ultrashort laser pulses through condensed media like crystals of BaF$_2$ and sapphire results in the formation of filaments. We demonstrate that the onset of filamentation may be controlled by rotating the plane of polarization of incident light. We directly visualize filamentation in BaF_2 via six-photon absorption-induced fluorescence and, concomitantly, by probing the spectral and spatial properties of white light that is generated.Comment: To appear in Phys. Rev.

Amplified Spontaneous Emission enhanced Forward Stimulated Raman Scattering in dye solutions

We study forward stimulated Raman emission from weakly fluorescent dye 4'-diethylamino-N-methyl-4-stilbazolium tosylate (DEST) in 1,2,dichloroethane solution excited by a 28 ps, 532 nm Nd: YAG laser. Neat 1, 2, dichloroethane emits the first Stokes line at 631 nm with a spectral width of 1.6 nm corresponding to a Raman shift of 2956 per cm. We observe reduction of spectral width with the addition of DEST in 1, 2, dichloroethane solution. The single pass conversion efficiency for forward Raman emission is as high as 20 percent in a 1 cm path length sample. The pulse duration of forward stimulated Raman emission measured by a third order autocorrelation technique is 10 ps in neat 1, 2, dichloroethane, whereas it is nearly 3 ps for 0.04 mM of DEST solution.Comment: 10 pages, 5 figure

Plasmodium-infected red blood cells exhibit enhanced rolling independent of host cells and alter flow of uninfected red cells

The pathogenicity of Plasmodium falciparum results from its unique ability to adhere to endothelium and uninfected erythrocytes. It is, therefore, important to understand the events leading to flowing blood cells undergoing such adhesion. Largely based on the leukocyte adhesion model, it is postulated that the slowing down (rolling) of Plasmodium-infected red blood cells (PRBCs) is initiated by interactions between certain host adhesion molecules and the parasite proteins. In this article we present data demonstrating that PRBCs do not require the presence of host adhesion molecules to slow down and roll. In a synchronized culture, the proportion of slow-flowing cells increased with parasite development and was highest at the trophozoite stage. We also observed that the uninfected red cells (URBCs), originating from a parasite culture containing PRBCs, were also inherently slower compared to malaria-unexposed normal red blood cells (NRBCs). NRBCs became slower upon incubation with supernatant taken from a parasite culture. However, such an effect was transient and the NRBCs reverted to their normal flow speed within 12 h upon withdrawal of culture supernatant. Based on our observations, we suggest that the higher propensity of PRBCs and URBCs to slow down is due to inherent structural anisotropy and altered membrane rigidity. Thus the initial events leading to the slowing down of malaria-infected blood cells appear to be different from those occurring during leukocyte adhesion

Let's not forget plants.

'Many physicists see the interface with biology as an exciting place to be'. Athene Donald provides a personal perspective on working at the interface between the physical and biological sciences.This is the accepted manuscript. The final version is available from IOP at http://iopscience.iop.org/1478-3975/11/5/053008