Long phase coherence time and number squeezing of two Bose-Einstein condensates on an atom chip

We measure the relative phase of two Bose-Einstein condensates confined in a radio frequency induced double-well potential on an atom chip. We observe phase coherence between the separated condensates for times up to approximately 200 ms after splitting, a factor of 10 longer than the phase diffusion time expected for a coherent state for our experimental conditions. The enhanced coherence time is attributed to number squeezing of the initial state by a factor of 10. In addition, we demonstrate a rotationally sensitive (Sagnac) geometry for a guided atom interferometer by propagating the split condensates.

Low velocity quantum reflection of Bose-Einstein condensates

We study how interactions affect the quantum reflection of Bose-Einstein condensates. A patterned silicon surface with a square array of pillars resulted in high reflection probabilities. For incident velocities greater than 2.5 mm/s, our observations agreed with single-particle theory. At velocities below 2.5 mm/s, the measured reflection probability saturated near 60% rather than increasing towards unity as predicted by the accepted theoretical model. We extend the theory of quantum reflection to account for the mean-field interactions of a condensate which suppresses quantum reflection at low velocity. The reflected condensates show collective excitations as recently predicted.

Temporal artery biopsy for diagnosing giant cell arteritis: the longer, the better?

OBJECTIVE

To investigate the relation between temporal artery biopsy (TAB) length and diagnostic sensitivity for giant cell arteritis.

METHODS

Histological TAB reports generated from four hospital pathology departments were reviewed for demographics, histological findings, and formalin fixed TAB lengths. A biopsy was considered positive for giant cell arteritis if there was a mononuclear cell infiltrate predominating at the media-intima junction or in the media.

RESULTS

Among 1821 TAB reports reviewed, 287 (15.8%) were excluded because of missing data, sampling errors, or age < 50 years. Mean TAB length of the 1520 datasets finally analysed (67.2% women; mean (SD) age, 73.1 (10.0) years) was 1.33 (0.73) cm. Histological evidence of giant cell arteritis was found in 223 specimens (14.7%), among which 164 (73.5%) contained giant cells. Statistical analyses, including piecewise logistic regression, identified 0.5 cm as the TAB length change point for diagnostic sensitivity. Compared with TAB length of < 0.5 cm, the respective odds ratios for positive TAB without and with multinucleated giant cells in samples > or = 0.5 cm long were 5.7 (95% confidence interval, 1.4 to 23.6) and 4.0 (0.97 to 16.5).

CONCLUSIONS

A fixed TAB length of at least 0.5 cm could be sufficient to make a histological diagnosis of giant cell arteritis.

[Whipple disease, initially diagnosed as sarcoidosis]

INTRODUCTION

Whipple disease is a multisystem infectious disease caused by Tropheryma whipplei. We report a case in which an initial diagnosis of sarcoidosis was changed to Whipple disease endocarditis.

CASE

Based on clinical, radiographic, endoscopic and histologic findings, this 61-year-old man was diagnosed with sarcoidosis. Initial response to corticotherapy was good, but the patient required 35 mg of prednisone daily. The subsequent onset of clinical and laboratory signs of inflammation cast doubt on the diagnosis. After cardiac ultrasound revealed a mass 1 cm in diameter on the mitral valve, apparently vegetation, we diagnosed culture-negative infective endocarditis and ruled out most possible causes. PCR of a duodenal biopsy sample showed Tropheryma whipplei, thus confirming the diagnosis of Whipple disease, despite normal histological findings. After 3 weeks of intravenous gentamicin and amoxicillin treatment, oral cotrimoxazole was substituted. Follow-up transesophageal ultrasound showed no mitral vegetation. The patient, still under cotrimoxazole, has been off prednisone for 13 months and is completely asymptomatic.

CONCLUSION

This case is an illustration of the difficulty in distinguishing Whipple disease from sarcoidosis in practice and of the importance of that distinction.

Optical weak link between two spatially separated Bose-Einstein condensates

Two spatially separate Bose-Einstein condensates were prepared in an optical double-well potential. A bidirectional coupling between the two condensates was established by two pairs of Bragg beams which continuously outcoupled atoms in opposite directions. The atomic currents induced by the optical coupling depend on the relative phase of the two condensates and on an additional controllable coupling phase. This was observed through symmetric and antisymmetric correlations between the two outcoupled atom fluxes. A Josephson optical coupling of two condensates in a ring geometry is proposed. The continuous outcoupling method was used to monitor slow relative motions of two elongated condensates and characterize the trapping potential.

Light Scattering to Determine the Relative Phase of Two Bose-Einstein Condensates

We demonstrated an experimental technique based on stimulated light scattering to continuously sample the relative phase of two spatially separated Bose-Einstein condensates of atoms. The phase measurement process created a relative phase between two condensates with no initial phase relation, read out the phase, and monitored the phase evolution. This technique was used to realize interferometry between two trapped Bose-Einstein condensates without need for splitting or recombining the atom cloud.

Quantum reflection from a solid surface at normal incidence

We observed quantum reflection of ultracold atoms from the attractive potential of a solid surface. Extremely dilute Bose-Einstein condensates of 23Na, with peak density 10(11)-10(12) atoms/cm(3), confined in a weak gravitomagnetic trap were normally incident on a silicon surface. Reflection probabilities of up to 20% were observed for incident velocities of 1-8 mm/s. The velocity dependence agrees qualitatively with the prediction for quantum reflection from the attractive Casimir-Polder potential. Atoms confined in a harmonic trap divided in half by a solid surface exhibited extended lifetime due to quantum reflection from the surface, implying a reflection probability above 50%.

Dynamical instability of a doubly quantized vortex in a Bose-Einstein condensate

Doubly quantized vortices were topologically imprinted in /F=1> 23Na condensates, and their time evolution was observed using a tomographic imaging technique. The decay into two singly quantized vortices was characterized and attributed to dynamical instability. The time scale of the splitting process was found to be longer at higher atom density.

Distillation of bose-einstein condensates in a double-well potential

Bose-Einstein condensates of sodium atoms, prepared in an optical dipole trap, were distilled into a second empty dipole trap adjacent to the first one. The distillation was driven by thermal atoms spilling over the potential barrier separating the two wells and then forming a new condensate. This process serves as a model system for metastability in condensates, provides a test for quantum kinetic theories of condensate formation, and also represents a novel technique for creating or replenishing condensates in new locations.

Atom interferometry with Bose-Einstein condensates in a double-well potential

A trapped-atom interferometer was demonstrated using gaseous Bose-Einstein condensates coherently split by deforming an optical single-well potential into a double-well potential. The relative phase between the two condensates was determined from the spatial phase of the matter wave interference pattern formed upon releasing the condensates from the separated potential wells. Coherent phase evolution was observed for condensates held separated by 13 microm for up to 5 ms and was controlled by applying ac Stark shift potentials to either of the two separated condensates.

Cooling Bose-Einstein condensates below 500 picokelvin

Spin-polarized gaseous Bose-Einstein condensates were confined by a combination of gravitational and magnetic forces. The partially condensed atomic vapors were adiabatically decompressed by weakening the gravito-magnetic trap to a mean frequency of 1hertz, then evaporatively reduced in size to 2500 atoms. This lowered the peak condensate density to 5 x 10(10) atoms per cubic centimeter and cooled the entire cloud in all three dimensions to a kinetic temperature of 450 +/- 80 picokelvin. Such spin-polarized, dilute, and ultracold gases are important for spectroscopy, metrology, and atom optics.

Coherent control of polariton parametric scattering in semiconductor microcavities

In a pump-probe experiment, we have been able to control, with phase-locked probe pulses, the ultrafast nonlinear optical emission of a semiconductor microcavity, arising from polariton parametric amplification. This evidences the coherence of the polariton population near k=0, even for delays much longer than the pulse width. The control of a large population at k=0 is possible although the probe pulses are much weaker than the large polarization they control. With rising pump power the dynamics of the scattering get faster. Just above threshold the parametric scattering process shows unexpected long coherence times, whereas when pump power is risen the contrast decays due to a significant pump reservoir depletion. The weak pulses at normal incidence control the whole angular emission pattern of the microcavity.

[Distal glue embolization in a patient with gastrointestinal hemorrhage]

This is a case report, concerning the endovascular use of N-butyl-2-cyanoacrylate, for treatment of a digestive hemorrhage from a distal branch of the superior mesenteric artery, leading to a successful outcome. This material, usually used in brain angiomas, constitutes an alternative for digestive embolization, which is quick, precise and definitive, without additional risk in experienced hands.

High-temperature ultrafast polariton parametric amplification in semiconductor microcavities

Cavity polaritons, the elementary optical excitations of semiconductor microcavities, may be understood as a superposition of excitons and cavity photons. Owing to their composite nature, these bosonic particles have a distinct optical response, at the same time very fast and highly nonlinear. Very efficient light amplification due to polariton-polariton parametric scattering has recently been reported in semiconductor microcavities at liquid-helium temperatures. Here we demonstrate polariton parametric amplification up to 120 K in GaAlAs-based microcavities and up to 220 K in CdTe-based microcavities. We show that the cut-off temperature for the amplification is ultimately determined by the binding energy of the exciton. A 5-micrometer-thick planar microcavity can amplify a weak light pulse more than 5,000 times. The effective gain coefficient of an equivalent homogeneous medium would be 107 cm-1. The subpicosecond duration and high efficiency of the amplification could be exploited for high-repetition all-optical microscopic switches and amplifiers. 105 polaritons occupy the same quantum state during the amplification, realizing a dynamical condensate of strongly interacting bosons which can be studied at high temperature.

Arginine deficiency-induced hyperammonemia in a home total parenteral nutrition-dependent patient: a case report

BACKGROUND

Patients with short bowel syndrome and renal dysfunction with TPN dependence are at high risk for developing hyperammonemia if the TPN does not contain sufficient quantities of arginine. Providing proper nutrition support is essential in the management of these patients.

METHODS

We report on a patient with short bowel syndrome, TPN dependence, and normal renal function who developed hyperammonemic encephalopathy due to inadvertent lack of arginine in his TPN.

RESULTS

The patient was successfully treated with hemodialysis and an IV arginine infusion to resolve the hyperammonemia. His home TPN was also adjusted such that arginine was added to his subsequent solutions.

CONCLUSIONS

Our patient underscores the importance of adequate and sustained arginine supplementation to avoid hyperammonemia in TPN dependent patients with short bowel syndrome.

Advanced life support: retention of registered nurses' knowledge 18 months after initial training

In 1996, The Wesley Hospital introduced a 2 day Advanced Life Support (ALS) course, targeted at all critical care registered nurses and medical officers. The purpose of this study was to explore the retention of theoretical knowledge and clinical skills of registered nurses who had successfully completed the 2 day ALS course 18 months previously and to establish effective retesting timeframes. The study utilised a repeated post-test measure design. Forty registered nurses participated in the study. Data were collected during ALS retesting using scores from a theoretical examination and from the results of four practical skill assessments (basic life support, airway management, defibrillation and code management). Using Wilcoxon test, data were analysed with and compared to the participant's original scores from the training program 18 months previously. The findings demonstrate that the participant's theoretical knowledge remained at an equivalent level over the 18 month timeframe. However, 18 months after successfully completing an ALS course, only 75 per cent (n = 30) of participants passed the practical skill assessment components, with the 25 per cent (n = 10) requiring a second attempt to pass. The implications from this study focus on the model of assessment utilised and the dichotomy between theoretical and practical skill assessment results. Additional study is required to determine the optimal timeframe for ALS retesting and educational strategies to help retain skills over time.

Crossover from exciton to biexciton polaritons in semiconductor microcavities

Pump-probe measurements in a microcavity containing a quantum well show that a population of circularly polarized ( sigma(+)) excitons can completely inhibit the transition to sigma(-) one-exciton states by transferring the oscillator strength to the biexcitonic resonance. With increasing pump intensity the linear exciton-polariton doublet evolves into a triplet polariton structure and finally into a shifted biexciton-polariton doublet. A theoretical model of interacting excitons demonstrates that the crossover from exciton to biexciton polaritons is driven by three-exciton Coulomb correlation.

Morphological and biochemical changes following acute unilateral testicular torsion in prepubertal rats

PURPOSE

The role played by reactive oxygen species in the effects of testicular torsion and torsion/detorsion on ipsilateral and contralateral testis was investigated.

MATERIALS AND METHODS

Prepubertal rats were submitted to unilateral testicular torsion alone or followed by detorsion for up to 1 week. Morphology and biochemical parameters (thiobarbituric reactive substances, superoxide dismutase-like and catalase-like activities) were evaluated.

RESULTS

Torsion (1 or 2 h) alone induced time-dependent morphological damages that worsened progressively after detorsion in ipsilateral testis but had no effect on contralateral testis. The levels of antioxidants against the superoxide anion and hydrogen peroxide decreased in ipsilateral but not in contralateral testis. However, the level of thiobarbituric reactive substances (an indicator of lipid perioxidation) decreased after testicular torsion or torsion/detorsion in both testes.

CONCLUSION

These data emphasize that oxidative stress may play a role in testicular damage caused by torsion/detorsion and that biochemical indicators of oxidative stress are more sensitive than histological techniques in detecting modifications in the contralateral testis.

Examination of the damping behavior of IMZ implants

The damping behavior of 392 IMZ implants with a diameter of 4 mm was examined by performing Periotest measurements during regular implant follow-up. The results were correlated with radiographically assessed peri-implant bone reduction. To guarantee statistical independence, only one randomly chosen implant per patient was considered in the examination. In 167 implants, the difference between the mean mandibular and maxillary Periotest values proved to be statistically significant. Age, sex, and radiographic length of the endosseous part of the abutment had no influence on the Periotest values. Assessment of the Periotest values can thus be considered an additional parameter for objective determination of IMZ implant success. However, exclusive use of the Periotest method without additional radiographic examinations does not seem to be justified.