Dynamics of a Fermi Gas Quenched to Unitarity.

We present an experimental study of a two component Fermi gas following an interaction quench into the superfluid phase. Starting with a weakly attractive gas in the normal phase, interactions are ramped to unitarity at a range of rates and we measure the subsequent dynamics as the gas approaches equilibrium. Both the formation and condensation of fermion pairs are mapped via measurements of the pair momentum distribution and can take place on very different timescales, depending on the adiabaticity of the quench. The contact parameter is seen to respond very quickly to changes in the interaction strength, indicating that short-range correlations, based on the occupation of high-momentum modes, evolve far more rapidly than the correlations in low-momentum modes necessary for pair condensation.

High-Frequency Sound in a Unitary Fermi Gas.

We present an experimental and theoretical study of the phonon mode in a unitary Fermi gas. Using two-photon Bragg spectroscopy, we measure excitation spectra at a momentum of approximately half the Fermi momentum, both above and below the superfluid critical temperature T_{c}. Below T_{c}, the dominant excitation is the Bogoliubov-Anderson (BA) phonon mode, driven by gradients in the phase of the superfluid order parameter. The temperature dependence of the BA phonon is consistent with a theoretical model based on the quasiparticle random phase approximation in which the dominant damping mechanism is via collisions with thermally excited quasiparticles. As the temperature is increased above T_{c}, the phonon evolves into a strongly damped collisional mode, accompanied by an abrupt increase in spectral width. Our study reveals strong similarities between sound propagation in the unitary Fermi gas and bosonic liquid helium.

Contact and Sum Rules in a Near-Uniform Fermi Gas at Unitarity.

We present an experimental study of the high-energy excitation spectra of unitary Fermi gases. Using focused beam Bragg spectroscopy, we locally probe atoms in the central region of a harmonically trapped cloud where the density is nearly uniform, enabling measurements of the dynamic structure factor for a range of temperatures both below and above the superfluid transition. Applying sum rules to the measured Bragg spectra, we resolve the characteristic behavior of the universal contact parameter, C, across the superfluid transition. We also employ a recent theoretical result for the kinetic (second-moment) sum rule to obtain the internal energy of gases at unitarity.

Erratum: Bright Solitonic Matter-Wave Interferometer [Phys. Rev. Lett. 113, 013002 (2014)].

This corrects the article DOI: 10.1103/PhysRevLett.113.013002.

Non-destructive shadowgraph imaging of ultra-cold atoms.

An imaging system is presented that is capable of far-detuned non-destructive imaging of a Bose-Einstein condensate with the signal proportional to the second spatial derivative of the density. Whilst demonstrated with application to Rb85, the technique generalizes to other atomic species and is shown to be capable of a signal-to-noise of ∼25 at 1 GHz detuning with 100 in-trap images showing no observable heating or atom loss. The technique is also applied to the observation of individual trajectories of stochastic dynamics inaccessible to single shot imaging. Coupled with a fast optical phase locked loop, the system is capable of dynamically switching to resonant absorption imaging during the experiment.

Simultaneous Precision Gravimetry and Magnetic Gradiometry with a Bose-Einstein Condensate: A High Precision, Quantum Sensor.

A Bose-Einstein condensate is used as an atomic source for a high precision sensor. A 5×10^{6} atom F=1 spinor condensate of ^{87}Rb is released into free fall for up to 750 ms and probed with a T=130 ms Mach-Zehnder atom interferometer based on Bragg transitions. The Bragg interferometer simultaneously addresses the three magnetic states |m_{f}=1,0,-1⟩, facilitating a simultaneous measurement of the acceleration due to gravity with a 1000 run precision of Δg/g=1.45×10^{-9} and the magnetic field gradient to a precision of 120 pT/m.

Time-of-flight detection of ultra-cold atoms using resonant frequency modulation imaging.

Resonant frequency modulation imaging is used to detect free falling ultra-cold atoms. A theoretical comparison of fluorescence imaging (FI) and frequency modulation imaging (FMI) is made, indicating that for low optical depth clouds, FMI accomplished a higher signal-to-noise ratio under conditions necessary for a 200 µm spatially resolved atom interferometer. A 750 ms time-of-flight measurement reveals near atom shot-noise limited number measurements of 2×106 Bose-condensed Rb87 atoms. The detection system is applied to high precision spinor BEC based atom interferometer.

Fast machine-learning online optimization of ultra-cold-atom experiments.

We apply an online optimization process based on machine learning to the production of Bose-Einstein condensates (BEC). BEC is typically created with an exponential evaporation ramp that is optimal for ergodic dynamics with two-body s-wave interactions and no other loss rates, but likely sub-optimal for real experiments. Through repeated machine-controlled scientific experimentation and observations our 'learner' discovers an optimal evaporation ramp for BEC production. In contrast to previous work, our learner uses a Gaussian process to develop a statistical model of the relationship between the parameters it controls and the quality of the BEC produced. We demonstrate that the Gaussian process machine learner is able to discover a ramp that produces high quality BECs in 10 times fewer iterations than a previously used online optimization technique. Furthermore, we show the internal model developed can be used to determine which parameters are essential in BEC creation and which are unimportant, providing insight into the optimization process of the system.

Bright solitonic matter-wave interferometer.

We present the first realization of a solitonic atom interferometer. A Bose-Einstein condensate of 1×10(4) atoms of rubidium-85 is loaded into a horizontal optical waveguide. Through the use of a Feshbach resonance, the s-wave scattering length of the 85Rb atoms is tuned to a small negative value. This attractive atomic interaction then balances the inherent matter-wave dispersion, creating a bright solitonic matter wave. A Mach-Zehnder interferometer is constructed by driving Bragg transitions with the use of an optical lattice colinear with the waveguide. Matter-wave propagation and interferometric fringe visibility are compared across a range of s-wave scattering values including repulsive, attractive and noninteracting values. The solitonic matter wave is found to significantly increase fringe visibility even compared with a noninteracting cloud.

11 W narrow linewidth laser source at 780 nm for laser cooling and manipulation of Rubidium.

We present a narrow linewidth continuous laser source with over 11 W output power at 780 nm, based on single-pass frequency doubling of an amplified 1560 nm fibre laser with 36% efficiency. This source offers a combination of high power, simplicity, mode quality and stability. Without any active stabilization, the linewidth is measured to be below 10 kHz. The fibre seed is tunable over 60 GHz, which allows access to the D2 transitions in 87Rb and 85Rb, providing a viable high-power source for laser cooling as well as for large-momentum-transfer beamsplitters in atom interferometry. Sources of this type will pave the way for a new generation of high flux, high duty-cycle degenerate quantum gas experiments.

Comparative study of different standardization concepts in quantitative competitive reverse transcription-PCR assays.

Four different standardization approaches based on a competitive reverse transcription (RT)-PCR assay were compared with a noncompetitive assay based on an external standard curve. Criteria for assessment were accuracy in quantitation, correctness of recovery, sensitivity, dynamic range, reproducibility, throughput, and convenience of sample handling. As a model system, we used the 5'-noncoding region of hepatitis C virus (HCV) for amplification in all quantitative RT-PCRs. A computer program that allowed parallel data processing was developed. Surprisingly, all methods were found suitable for accurate quantitation and comparable with respect to the criterion correctness of recovery. All results differed only by a factor of about 2. The reason for this finding might be that all of our mimics, as well as the wild-type genome of HCV, exhibited exactly the same amplification and hybridization efficacy. Moreover, minimal competition occurred in our experiments over a 5-log dynamic range. A further topic of our investigation was the comparison of two different competitive RNA fragments, mimics, with regard to their suitability as internal standards. One was a heterologous mimic, in which only the primer binding sites were identical to the wild type. The second one was a homologous mimic identical to the wild type except for a small region used for differential hybridization, which was replaced by a permutated sequence of the same length. Both the homologous and heterologous internal mimics were found appropriate for an accurate competitive RT-PCR assay, provided that amplification efficacy, as well as capture efficacy, is proven identical for both analyte and mimic.

Electrophoretic purification of the alpha and beta subunits of phosphorylase kinase and evidence in support of the deduced amino acid sequences.

A simple, rapid sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) method is presented for isolating the alpha, alpha' and beta subunits of rabbit muscle phosphorylase kinase. The SDS-PAGE procedure can yield milligram amounts of alpha and beta from a single preparative gel and also allows isolation of the alpha' isozyme free of alpha. Notably the method provides the purified subunits in a form amenable to structural analysis. Edman degradation of alpha and alpha' reveal identical NH2-terminal structures. Amino acid analysis of the electrophoretically purified alpha and beta subunits are in good agreement with their deduced primary structures. The amino acid sequence of 488 residues in alpha and 713 residues in beta were determined by gas phase Edman degradation. The data support the recently deduced primary structures of alpha (Zander et al., Proc. Natl. Acad. Sci. USA, 1988, 85, 9381-9385).

The alpha and beta subunits of phosphorylase kinase are homologous: cDNA cloning and primary structure of the beta subunit.

We have cloned cDNA molecules encoding the beta subunit of phosphorylase kinase (ATP:phosphorylase-b phosphotransferase; EC 2.7.1.38) from rabbit fast-twitch skeletal muscle and have determined the complete primary structure of the polypeptide by a combination of peptide and DNA sequencing. In the mature beta subunit, the initial methionine is replaced by an acetyl group. The subunit is composed of 1092 amino acids and has a calculated molecular mass of 125,205 Da. Alignment of its sequence with the alpha subunit of phosphorylase kinase reveals extensive regions of homology, but each molecule also possesses unique sequences. Two of the three phosphorylation sites known for the beta subunit and all seven phosphorylation sites known for the alpha subunit are located in these unique domains.

Residency education in for-profit general hospitals.

In May, 1983, when the new University of Louisville teaching hospital was opened under the auspices of Humana Corporation, it became the first university hospital operated by a for-profit corporation. We describe the agreement that launched this venture and summarize the experiences of the Department of Psychiatry and Behavioral Sciences with Humana, Inc., during the past 3 years. We review our impressions of both the positive and negative effects that the for-profit managing style has had thus far on the teaching programs of the Department. Based on our experiences, there are financial and other benefits, but we think that there are also potential dangers for the future of psychiatric education inherent in the administration of a teaching hospital by a for-profit corporation. The "atmosphere of business" that pervades the climate of opinion in the United States in the 1980s and is merely epitomized by the increasing role of enterpreneurial groups in medicine can be antithetical to principles of psychiatry and has implications for psychiatric education in the future. Awareness of these developments is a task for psychiatric education and, when it is possible, comparative studies of residents and their programs in nonprofit and for-profit hospitals should be conducted.

Depression and internal medicine.

Although the Fathers of Internal Medicine described melancholia and wrote extensively about the affective disorders, internists continue to have difficulties diagnosing their medical patients' depressions. Consequently, it often falls to the psychiatric consultant to make the diagnosis amongst the medical population. We present current concepts of affective disorder that should be clinically relevant to the psychiatrist who works with internists and their patients. Early, accurate diagnosis of depressed medical patients requires increased awareness of depression, observation of the patient's appearance and mood, sensitivity to his or her feelings, and specific questioning about symptoms, losses, and stressors. For depressed medical patients, we present a comprehensive treatment program which often should include: 1) supportive psychotherapy, 2) antidepressant medications; and 3) resocialization or rehabilitation. We outline certain indications for psychiatric referral, and urge psychiatrists and internists to work together closely. Increasing the sensitivity of our colleagues in internal medicine toward affective illness should lead to more prompt identification and treatment of medical patients' depressions.