A quantum engine in the BEC-BCS crossover.

Heat engines convert thermal energy into mechanical work both in the classical and quantum regimes1. However, quantum theory offers genuine non-classical forms of energy, different from heat, which so far have not been exploited in cyclic engines. Here we experimentally realize a quantum many-body engine fuelled by the energy difference between fermionic and bosonic ensembles of ultracold particles that follows from the Pauli exclusion principle2. We employ a harmonically trapped superfluid gas of 6Li atoms close to a magnetic Feshbach resonance3 that allows us to effectively change the quantum statistics from Bose-Einstein to Fermi-Dirac, by tuning the gas between a Bose-Einstein condensate of bosonic molecules and a unitary Fermi gas (and back) through a magnetic field4-10. The quantum nature of such a Pauli engine is revealed by contrasting it with an engine in the classical thermal regime and with a purely interaction-driven device. We obtain a work output of several 106 vibrational quanta per cycle with an efficiency of up to 25%. Our findings establish quantum statistics as a useful thermodynamic resource for work production.

Self-Pinning Transition of a Tonks-Girardeau Gas in a Bose-Einstein Condensate.

We show that a Tonks-Girardeau (TG) gas that is immersed in a Bose-Einstein condensate can undergo a transition to a crystal-like Mott state with regular spacing between the atoms without any externally imposed lattice potential. We characterize this phase transition as a function of the interspecies interaction and temperature of the TG gas, and show how it can be measured via accessible observables in cold atom experiments. We also develop an effective model that accurately describes the system in the pinned insulator state and which allows us to derive the critical temperature of the transition.

Inverted harmonic oscillator dynamics of the nonequilibrium phase transition in the Dicke model.

We show how the dynamics of the Dicke model after a quench from the ground-state configuration of the normal phase into the superradiant phase can be described for a limited time by a simple inverted harmonic oscillator model and that this limited time approaches infinity in the thermodynamic limit. Although we specifically discuss the Dicke model, the presented mechanism can also be used to describe dynamical quantum phase transitions in other systems and presents an opportunity for simulations of physical phenomena associated with an inverted harmonic oscillator.

Asymmetric Loop Spectra and Unbroken Phase Protection due to Nonlinearities in PT-Symmetric Periodic Potentials.

We demonstrate that the interplay between a nonlinearity and PT symmetry in a periodic potential results in peculiar features of nonlinear periodic solutions. These include thresholdless symmetry breaking and asymmetric (multi-)loop structures of the nonlinear Bloch spectrum, persistence of unbroken PT symmetry even after the gap is closed, nonmonotonic dependence of the PT phase transition on the defocusing nonlinearity, and enhanced stability of the nonlinear states corresponding to the loop structures. The asymmetry and the loop structure of the spectrum are explained within the framework of a two-mode approximation and an effective potential theory and are validated numerically.

Simulating the Same Physics with Two Distinct Hamiltonians.

We develop a framework and give an example for situations where two distinct Hamiltonians living in the same Hilbert space can be used to simulate the same physics. As an example of an analog simulation, we first discuss how one can simulate an infinite-range-interaction one-axis twisting Hamiltonian using a short-range nearest-neighbor-interaction Heisenberg XXX model with a staggered field. Based on this, we show how one can build an alternative version of a digital quantum simulator. As a by-product, we present a method for creating many-body maximally entangled states using only short-range nearest-neighbor interactions.

In Situ Thermometry of a Cold Fermi Gas via Dephasing Impurities.

The precise measurement of low temperatures is a challenging, important, and fundamental task for quantum science. In particular, in situ thermometry is highly desirable for cold atomic systems due to their potential for quantum simulation. Here, we demonstrate that the temperature of a noninteracting Fermi gas can be accurately inferred from the nonequilibrium dynamics of impurities immersed within it, using an interferometric protocol and established experimental methods. Adopting tools from the theory of quantum parameter estimation, we show that our proposed scheme achieves optimal precision in the relevant temperature regime for degenerate Fermi gases in current experiments. We also discover an intriguing trade-off between measurement time and thermometric precision that is controlled by the impurity-gas coupling, with weak coupling leading to the greatest sensitivities. This is explained as a consequence of the slow decoherence associated with the onset of the Anderson orthogonality catastrophe, which dominates the gas dynamics following its local interaction with the immersed impurity.

Orthogonality Catastrophe as a Consequence of the Quantum Speed Limit.

A remarkable feature of quantum many-body systems is the orthogonality catastrophe that describes their extensively growing sensitivity to local perturbations and plays an important role in condensed matter physics. Here we show that the dynamics of the orthogonality catastrophe can be fully characterized by the quantum speed limit and, more specifically, that any quenched quantum many-body system, whose variance in ground state energy scales with the system size, exhibits the orthogonality catastrophe. Our rigorous findings are demonstrated by two paradigmatic classes of many-body systems-the trapped Fermi gas and the long-range interacting Lipkin-Meshkov-Glick spin model.

Torque of guided light on an atom near an optical nanofiber.

We calculate analytically and numerically the axial orbital and spin torques of guided light on a two-level atom near an optical nanofiber. We show that the generation of these torques is governed by the angular momentum conservation law in the Minkowski formulation. The orbital torque on the atom near the fiber has a contribution from the average recoil of spontaneously emitted photons. Photon angular momentum and atomic spin angular momentum can be converted into atomic orbital angular momentum. The orbital and spin angular momenta of the guided field are not transferred separately to the orbital and spin angular momenta of the atom.

Comprehensive analysis of west nile virus-specific T cell responses in humans.

BACKGROUND: Cellular responses have been shown to play a role in immune control and clearance of West Nile virus (WNV) in murine models. However, little is known about the immunogenic regions of the virus or the phenotype of responding T cells in human infection. METHODS: Frozen peripheral blood mononuclear cells (PBMCs) from 35 WNV-infected blood donors were screened for virus-specific T cell responses by an interferon-gamma (IFN-gamma) enzyme-linked immunosorbent spot assay that used 452 overlapping peptides spanning all WNV proteins. More-detailed phenotypic studies were performed on subjects with high-magnitude T cell responses. RESULTS: In individuals with identified responses, the total number of recognized WNV peptides ranged from 1 to 9 (median, 2 peptides), and the overall magnitude of responses ranged from 50 to 4210 spot-forming cells (SFCs) per 10(6) PBMCs (median, 130 SFCs/10(6) PBMCs). A subset of 8 frequently recognized peptides from the regions of the genome encoding membrane, envelope, and nonstructural 3 and 4b proteins was identified. Phenotypic study of the highest magnitude WNV-specific T cell responses revealed that most were mediated by CD8+ cells that expressed perforin and/or granzyme B. CONCLUSIONS: These findings are the first to define the breadth and characteristics of the human T cell response to WNV and have implications for candidate vaccine design and evaluation.

Surgery for non-small cell carcinoma in geriatric patients: 15-year experience.

The purpose of this study was to determine the clinical patterns, short- and long-term survival in elderly patients after surgery for non-small cell lung carcinoma. The 273 patients aged over 70 years who underwent curative resection from 1986 to 2001 were retrospectively assessed. Mean age was 73.2+/-3.1 years, (11% were>80 years). The mean follow-up was 31 months. Standard procedures were used: 151 lobectomies, 49 bilateral lobectomies, 42 pneumonectomies, 9 sleeve resections, and 22 wedge resections. The 30-day mortality was 5.4%. Multivariate analysis showed that extended procedures, male sex, and age were predictors of mortality. Overall survival rates at 5, 10, and 15 years were 35.6%, 10.5%, and 2.5%, respectively. Advanced disease stage, low forced expiratory volume in 1 second, and previous cardiac disease were independent predictors that adversely influenced survival. Geriatric patients with non-small cell lung carcinoma can undergo resection safely with acceptable long-term survival. Lobectomy is the procedure of choice, extended resections should only be carried out in highly selected patients. Careful attention to preoperative clinical staging is important as the elderly beyond the early stage of disease fare poorly. Surgery is justified for the treatment of stage I-II lung cancer.

Delay-induced excitability.

We analyze the stochastic dynamics of a bistable system under the influence of time-delayed feedback. Assuming an asymmetric potential, we show the existence of a regime in which the system dynamics displays excitability by calculating the relevant residence time distributions and power spectra. Experimentally we then observe this behavior in the polarization dynamics of a vertical cavity surface emitting laser with optoelectronic feedback. Extending these observations to two-dimensional systems with diffusive coupling, we finally show numerically that delay-induced excitability can lead to the appearance of propagating wave fronts and spirals.

Molecular magnetic resonance imaging of atrial clots in a swine model.

BACKGROUND: The detection and differentiation of intracardiac masses is still challenging and may include neoplasms and thrombi. The aim of this study was the investigation of a targeted, fibrin-specific contrast agent (EP-2104R) for molecular targeted magnetic resonance imaging (MRI) of left atrial clots. METHODS AND RESULTS: Chronic human thrombi were surgically implanted in the left atrial appendage of 5 swine. Molecular MRI was performed with a navigator-gated, free-breathing, cardiac-triggered 3D inversion-recovery, black-blood, gradient-echo sequence before and after systemic administration of 4 micromol/kg EP-2104R. MR images were analyzed by 2 investigators, and the contrast-to-noise ratio was calculated. Location of clots was confirmed by autopsy, and the gadolinium concentration in the clots was assessed. Before contrast agent administration, thrombi were not visible on black-blood MR images. After contrast administration, all atrial clots (n=5) were selectively visualized as white spots with a high contrast-to-noise ratio (clot/blood, 29.7+/-8.0). The gadolinium concentration in the clots averaged 74+/-45 micromol/L. CONCLUSIONS: The fibrin-specific MR contrast agent EP-2104R allows for selective and high-contrast visualization of left atrial clots by means of molecular targeted MRI.

Intraoperative hemofiltration in adults: prevention of hypercirculatory syndrome?

Hypercirculatory syndrome (HCS) after cardiac surgery may be a sequela of extracorporeal circulation due to hemodilution and release of inflammatory mediators. The aim of this study was to investigate the influence of intraoperative hemofiltration (HF) on the incidence of HCS. A prospective cohort study of 80 patients scheduled for elective coronary bypass was performed. The patients were randomized to two groups: in the conventional (CONV) group 40 patients were treated conventionally and in the HF group 40 patients underwent intraoperative HF. There was no perioperative mortality. The incidence of HCS was comparable in both groups (32% in CONV group versus 40% in HF group; n.s.). Mean cardiac output was higher and systemic vascular resistance lower in CONV group patients than in HF group patients, however these differences did not reach statistical significance. According to this data intraoperative HF does not prevent postoperative HCS induced by cardiopulmonary bypass. Further studies are required to identify the etiology of HCS, and to prevent it occurring after open-heart surgery.

Congenital coronary artery fistulas in adults: surgical treatment and outcome.

BACKGROUND: Congenital coronary artery fistulas, a subgroup of anomalies of the coronary arteries, are an extremely rare cardiac defect. Most patients are asymptomatic, and if symptoms are presented, they depend on the underlying anatomy. Knowledge of those fistulas is important for prognosis and management. METHODS: Thirteen adult patients with congenital coronary fistulas (8 male, 5 female) were operated in our department during the last decade (1990-1999). Mean age was 61.5+/-10.8 years. Diagnosis was made by coronary angiography, and 15 congenital coronary artery fistulas were found. RESULTS: All patients were symptomatic with clinical symptoms depending on the associated cardiac disorder. Coronary artery fistulas originated from the proximal left descending artery (n=10), left main stem (n=3), circumflex artery (n=1), right coronary artery (n=1), and drained into the main pulmonary artery (n=14) and left ventricle (n=1). Nine fistulas (60%) were interrupted on the outside of the heart, and six fistulas (40%) were closed through the opened pulmonary artery. There was no surgical death and no fistula-related complication. CONCLUSIONS: Surgical closure of congenital coronary artery fistulas in adults can be performed with a very low risk, and closure is recommended to prevent complications.

Methylene blue administration in severe systemic inflammatory response syndrome (SIRS) after thoracic surgery.

A 66-year-old male patient developed significant pleural effusion on the right side six years after coronary bypass grafting and mitral valve replacement. After pleurocentesis, hemo-pneumothorax developed and finally resulted in complete atelectasis of the right lung. Three weeks later, the patient was transferred to our department, and underwent a right lateral thoracotomy. The hematoma was removed and a complete decortication was performed. Four hours postoperatively the patient developed severe SIRS with beginning multiorgan failure. Even extremely high doses of norepinephrine could not raise the systemic vascular resistance. Single intravenous administration of methylene blue lead to significant and permanent improvement of the hemodynamic status.