Laser induced fluorescence measurements of axial velocity, velocity shear, and parallel ion temperature profiles during the route to plasma turbulence in a linear magnetized plasma device.

We report experimental measurements of the axial plasma flow and the parallel ion temperature in a magnetized linear plasma device. We used laser induced fluorescence to measure Doppler resolved ion velocity distribution functions in argon plasma to obtain spatially resolved axial velocities and parallel ion temperatures. We also show changes in the parallel velocity profiles during the transition from resistive drift wave dominated plasma to a state of weak turbulence driven by multiple plasma instabilities.

Simultaneous use of camera and probe diagnostics to unambiguously identify and study the dynamics of multiple underlying instabilities during the route to plasma turbulence.

We use multiple-tip Langmuir probes and fast imaging to unambiguously identify and study the dynamics of underlying instabilities during the controlled route to fully-developed plasma turbulence in a linear magnetized helicon plasma device. Langmuir probes measure radial profiles of electron temperature, plasma density and potential; from which we compute linear growth rates of instabilities, cross-phase between density and potential fluctuations, Reynold's stress, particle flux, vorticity, time-delay estimated velocity, etc. Fast imaging complements the 1D probe measurements by providing temporally and spatially resolved 2D details of plasma structures associated with the instabilities. We find that three radially separated plasma instabilities exist simultaneously. Density gradient driven resistive drift waves propagating in the electron diamagnetic drift direction separate the plasma into an edge region dominated by strong, velocity shear driven Kelvin-Helmholtz instabilities and a central core region which shows coherent Rayleigh-Taylor modes propagating in the ion diamagnetic drift direction. The simultaneous, complementary use of both probes and camera was crucial to identify the instabilities and understand the details of the very rich plasma dynamics.

Dipole enhancement of positron binding to molecules.

Measurements of positron-molecule binding energies are made for molecules with large permanent dipole moments (>2.7 D), by studying vibrational-Feshbach-mediated annihilation resonances as a function of incident positron energy. The binding energies are relatively large (e.g., ≥90 meV) as compared to those for similar sized molecules studied previously and analogous weakly bound electron-molecule (negative ion) states. Comparisons with existing theoretical predictions are discussed.

Peripheral T-cell lymphoma presenting as sclerouveitis.

PURPOSE: To report an unusual case of ocular peripheral T-cell lymphoma presenting as sclerouveitis. METHODS: A 53-year-old woman presented with painful, unilateral sclerouveitis and was initially treated with antivirals and corticosteroids for what was presumed to be isolated ocular HSV infection with vasculitis. When she failed to improve the conjunctiva was biopsied and characterized by immunohistochemical and molecular methods. The literature regarding conjunctival T-cell lymphomas as well as lymphomas mimicking scleritis is reviewed. RESULTS: Biopsies of a scleral/conjunctival nodule from the right eye were obtained on 2 occasions, the second of which revealed the presence of intermediate to large size lymphocytes that were CD3, T-cell intracellular antigen 1 and Granzyme B positive but CD56 and Epstein Barr virus negative. Polymerase chain reaction showed clonal T-cell receptor gamma rearrangements in DNA samples isolated from biopsy tissue. Another biopsy was obtained from a mucosal lesion in the oropharynx, which was shown to contain an identical T-cell receptor gamma rearrangement. These results led to the diagnosis of peripheral T-cell lymphoma. Conjunctival T-cell lymphomas have been reported in two other patients both of which also had involvement of upper airway structures. Five other reports of lymphoma mimicking scleritis are discussed. CONCLUSIONS: Peripheral T-cell lymphoma should be considered in the differential diagnosis of patients who present with sclerouveitis of unknown etiology unresponsive to conventional therapy. If a conjunctival T-cell lymphoma is identified a systemic evaluation for lymphoma with particular attention to the upper airway is justified.