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We have studied the transition from two to three dimensions in a low temperature weakly interacting 6Li Fermi gas. Below a critical atom number N2D only the lowest transverse vibrational state of a highly anisotropic oblate trapping potential is occupied and the gas is two dimensional. Above N2D the Fermi gas enters the quasi-2D regime where shell structure associated with the filling of individual transverse oscillator states is apparent. This dimensional crossover is demonstrated through measurements of the cloud size and aspect ratio versus atom number. [ABSTRACT FROM AUTHOR]

We observe two consecutive heteronuclear Efimov resonances in an ultracold Li-Cs mixture by measuring three-body loss coefficients as a function of magnetic field near a Feshbach resonance. The first resonance is detected at a scattering length of a-(0) = -320(10)a0, corresponding to ∼7(∼3) times the Li-Cs (Cs-Cs) van der Waals range. The second resonance appears at 5.8(1.0)a-(0), close to the unitaritylimited regime at the sample temperature of 450 nK. Indication of a third resonance is found in the atom loss spectra. The scaling of the resonance positions is close to the predicted universal scaling value of 4.9 for zero temperature. Deviations from universality might be caused by finite-range and temperature effects, as well as magnetic field-dependent Cs-Cs interactions. [ABSTRACT FROM AUTHOR]

The contact I, introduced by Tan, has emerged as a key parameter characterizing universal properties of strongly interacting Fermi gases. For ultracold Fermi gases near a Feshbach resonance, the contact depends upon two quantities: the interaction parameter 1/(k(F)a), where k(F) is the Fermi wave vector and a is the s-wave scattering length, and the temperature T/T(F), where T(F) is the Fermi temperature. We present the first measurements of the temperature dependence of the contact in a unitary Fermi gas using Bragg spectroscopy. The contact is seen to follow the predicted decay with temperature and shows how pair-correlations at high momentum persist well above the superfluid transition temperature.

We show that short-range pair correlations in a strongly interacting Fermi gas follow a simple universal law described by Tan's relations. This is achieved through measurements of the static structure factor which displays a universal scaling proportional to the ratio of Tan's contact to the momentum C/q. Bragg spectroscopy of ultracold 6Li atoms from a periodic optical potential is used to measure the structure factor for a wide range of momenta and interaction strengths, providing broad confirmation of this universal law. We calibrate our Bragg spectra using the f-sum rule, which is found to improve the accuracy of the structure factor measurement.

We present a comprehensive study of the Bose-Einstein condensate to Bardeen-Cooper-Schrieffer (BEC-BCS) crossover in fermionic 6Li using Bragg spectroscopy. A smooth transition from molecular to atomic spectra is observed with a clear signature of pairing at and above unitarity. These spectra probe the dynamic and static structure factors of the gas and provide a direct link to two-body correlations. We have characterized these correlations and measured their density dependence across the broad Feshbach resonance at 834 G.

Using a serum-free medium supplemented with hormones and growth factors, which included epidermal growth factor (EGF), we investigated the binding and processing-degradation of [125I]EGF in WI-38 cells of various in vitro ages. The binding and processing-degradation systems of these cells remained essentially unchanged throughout their lifespan. The number of specific [125I]EGF binding sites per cell increased as the cultures senesced, though the number of specific binding sites per micron 2 (surface area) remained constant. The kinetics of ligand degradation as well as the qualitative and quantitative nature of the degradation products also remained essentially unchanged throughout the life-span. The only consistent alteration in any of the binding parameters measured was the slight decrease in the apparent Kd of the ligand-receptor complex, independent of temperature. Quantitation of EGF-stimulated DNA synthesis revealed a decrease in the percentage of cells incorporating [3H]thymidine ([3H]TdR) during a 30-h exposure from 45% in young cells to 0.25% in senescent cells, although [125I]EGF binding or processing-degradation did not differ significantly in young and old cells. Thus, EGF binding does not decrease in senescence.