Production efficiency of ultracold feshbach molecules in bosonic and fermionic systems

We investigate the production efficiency of ultracold molecules in bosonic 85Rb and fermionic 40K when the magnetic field is swept across a Feshbach resonance. For adiabatic sweeps of the magnetic field, our novel model shows that the conversion efficiency of both species is solely determined by the phase space density of the atomic cloud, in contrast with a number of theoretical predictions. In the nonadiabatic regime our measurements of the 85Rb molecule conversion efficiency follow a Landau-Zener model.     

Vortex precession in Bose-Einstein condensates: observations with filled and empty cores

We have observed and characterized the dynamics of singly quantized vortices in dilute-gas Bose-Einstein condensates. Our condensates are produced in a superposition of two internal states of 87Rb, with one state supporting a vortex and the other filling the vortex core. Subsequently, the state filling the core can be partially or completely removed, reducing the radius of the core by as much as a factor of 13, all the way down to its bare value of the healing length. The corresponding superfluid rotation rates, evaluated at the core radius, vary by a factor of 150, but the precession frequency of the vortex core about the condensate axis changes by only a factor of 2.     

Stable 85Rb bose-einstein condensates with widely tunable interactions

Bose-Einstein condensation has been achieved in a magnetically trapped sample of 85Rb atoms. Long-lived condensates of up to 10(4) atoms have been produced by using a magnetic-field-induced Feshbach resonance to reverse the sign of the scattering length. This system provides new opportunities for the study of condensate physics. The variation of the scattering length near the resonance has been used to magnetically tune the condensate self-interaction energy over a wide range, extending from strong repulsive to large attractive interactions. When the interactions were switched from repulsive to attractive, the condensate shrank to below our resolution limit, and after approximately 5 ms emitted a burst of high-energy atoms.     

Changes in tumor interstitial pressure induced by photodynamic therapy.

This study has examined the changes in tumor interstitial pressure exhibited during and after photodynamic therapy (PDT). The kinetics of these changes are marked by an initial decrease, followed by a rapid rise in tumor interstitial pressure. We have also employed two inhibitory agents to evaluate the different components of the pressure curve. Specially designed pressure chambers were seeded with chondrosarcoma and implanted subcutaneously in rats. Animals were injected with 0-50 mg/kg Photofrin II (i.v.) 7 days post-implantation and tumors were exposed to 0-540 J/cm2 630 nm 24 h later. Interstitial pressure was monitored via a transducer connected to the implanted chamber. Additional groups of animals were injected with either indomethacin (an inhibitor of thromboxane synthesis) or Ketanserin (a serotonin antagonist) before light treatment. Porphyrin doses of 10 mg/kg and above (135 J/cm2), or light doses of 135 J/cm2 and above (25 mg/kg Photofrin II) were effective in modifying interstitial pressure. Porphyrin doses greater than 25 mg/kg, or light doses greater than 270 J/cm2 produced no further increases in interstitial pressure. Animals given indomethacin (10 mg/kg i.p.) exhibited the initial decrease in pressure during light treatment, but showed no increase past baseline levels. Animals given Ketanserin (10 mg/kg i.p.) demonstrated no decrease in pressure during PDT, but showed the same elevations in pressure as controls. This suggests that two independent mechanisms account for the different components of the pressure curve, and that serotonin release may occur during PDT.     

Microscopic dynamics in a strongly interacting Bose-Einstein condensate

An initially stable 85Rb Bose-Einstein condensate (BEC) was subjected to a carefully controlled magnetic field pulse near a Feshbach resonance. This pulse probed the strongly interacting regime for the BEC, with the diluteness parameter (na(3)) ranging from 0.01 to 0.5. Condensate number loss resulted from the pulse, and for triangular pulses shorter than 1 ms, decreasing the pulse length actually increased the loss, until very short time scales (approximately 10 micros) were reached. The observed time dependence is very different from that expected in traditional inelastic loss processes, suggesting the presence of new microscopic BEC physics.     

In Vivo and In Vitro Photodynamic Studies with Benzochlorin Iminium Salts Delivered by a Lipid Emulsion

Benzochlorin iminium salts (Bis) are hydrophobic photosensitizers based on an octaethylbenzochlorin nucleus that absorb in the near-IR region of the visible spectrum. In these studies the photodynamic activities of the zinc, copper and metal-free BI derivatives were compared in vivo in C3H-HeJ mice bearing a mammary adenocarcinoma tumor line. In vitro studies were also performed with the radiation-induced fibrosarcoma tumor line. An argon-pumped Ti-sapphire laser tuned to deliver light between 710 and 800 nm or an Oriel arc-lamp filtered to deliver broadband light above 590 nm were used as light source. A lipid emulsion was used as the delivery system for sensitizers in all studies. A pronounced solvent dependence was observed for the Q band for each of all iminium salts examined. As an example, the metal-free (BI) derivative had an absorption maximum at 798 nm in dichloromethane and at 727 nm in serum. The action spectra showed a greater PDT response at blue-shifted wavelengths for each of the three iminium salts both in vivo and in vitro. Among the three derivatives, the zinc analog (ZnBI) produced the greatest tumor regression at the low drug/light dose of 0.7 (μ mole/kg and 200 J/cm². These results indicate that iminium salts have characteristics that may make them promising third-generation photosensitizers.