115 research outputs found
Spinor Dynamics-Driven Formation of a Dual-Beam Atom Laser
We demonstrate a novel dual-beam atom laser formed by outcoupling oppositely
polarized components of an F=1 spinor Bose-Einstein condensate whose Zeeman
sublevel populations have been coherently evolved through spin dynamics. The
condensate is formed through all-optical means using a single-beam running-wave
dipole trap. We create a condensate in the field-insensitive state, and
drive coherent spin-mixing evolution through adiabatic compression of the
initially weak trap. Such dual beams, number-correlated through the angular
momentum-conserving reaction , have been
proposed as tools to explore entanglement and squeezing in Bose-Einstein
condensates, and have potential use in precision phase measurements.Comment: 4 pages, 4 figure
A compact high-flux cold atom beam source
We report on an efficient and compact high-flux Cs atom beam source based on
a retro-reflected two-dimensional magneto-optical trap (2D MOT). We realize an
effective pushing field component by tilting the 2D MOT collimators towards a
separate three-dimensional magneto-optical trap (3D MOT) in ultra-high vacuum.
This technique significantly improved 3D MOT loading rates to greater than atoms/s using only 20 mW of total laser power for the source. When
operating below saturation, we achieve a maximum efficiency of atoms/s/W
Shell potentials for microgravity Bose-Einstein condensates
Extending the understanding of Bose-Einstein condensate (BEC) physics to new
geometries and topologies has a long and varied history in ultracold atomic
physics. One such new geometry is that of a bubble, where a condensate would be
confined to the surface of an ellipsoidal shell. Study of this geometry would
give insight into new collective modes, self-interference effects,
topology-dependent vortex behavior, dimensionality crossovers from thick to
thin shells, and the properties of condensates pushed into the ultradilute
limit. Here we discuss a proposal to implement a realistic experimental
framework for generating shell-geometry BEC using radiofrequency dressing of
magnetically-trapped samples. Such a tantalizing state of matter is
inaccessible terrestrially due to the distorting effect of gravity on
experimentally-feasible shell potentials. The debut of an orbital BEC machine
(NASA Cold Atom Laboratory, aboard the International Space Station) has enabled
the operation of quantum-gas experiments in a regime of perpetual freefall, and
thus has permitted the planning of microgravity shell-geometry BEC experiments.
We discuss specific experimental configurations, applicable inhomogeneities and
other experimental challenges, and outline potential experiments.Comment: 6 pages, 3 figure
Breakdown of the scale invariance in the vicinity of Tonks-Girardeau gas
In this article, we consider the monopole excitations of the harmonically
trapped Bose gas in the vicinity of the Tonks-Girardeau limit. Using
Girardeau's Fermi-Bose duality and subsequently an effective fermion-fermion
odd-wave interaction, we obtain the dominant correction to the
scale-invariance-protected value of the excitation frequency, for
microscopically small excitation amplitudes. We produce a series of diffusion
Monte Carlo results that confirm our analytic prediction for three particles.
And less expectedly, our result stands in excellent agreement with the result
of a hydrodynamic simulation of the microscopically large but macroscopically
small excitations.Comment: 8 pages, 3 figure
Observation of ultracold atomic bubbles in orbital microgravity
Substantial leaps in the understanding of quantum systems have been driven by exploring geometry, topology, dimensionality and interactions in ultracold atomic ensembles1–6. A system where atoms evolve while confined on an ellipsoidal surface represents a heretofore unexplored geometry and topology. Realizing an ultracold bubble—potentially Bose–Einstein condensed—relates to areas of interest including quantized-vortex flow constrained to a closed surface topology, collective modes and self-interference via bubble expansion7–17. Large ultracold bubbles, created by inflating smaller condensates, directly tie into Hubble-analogue expansion physics18–20. Here we report observations from the NASA Cold Atom Lab21 facility onboard the International Space Station of bubbles of ultracold atoms created using a radiofrequency-dressing protocol. We observe bubble configurations of varying size and initial temperature, and explore bubble thermodynamics, demonstrating substantial cooling associated with inflation. We achieve partial coverings of bubble traps greater than one millimetre in size with ultracold films of inferred few-micrometre thickness, and we observe the dynamics of shell structures projected into free-evolving harmonic confinement. The observations are among the first measurements made with ultracold atoms in space, using perpetual freefall to explore quantum systems that are prohibitively difficult to create on Earth. This work heralds future studies (in orbital microgravity) of the Bose–Einstein condensed bubble, the character of its excitations and the role of topology in its evolution
Exploring the limits of ultracold atoms in space
Existing space-based cold atom experiments have demonstrated the utility of microgravity for improvements in observation times and for minimizing the expansion energy and rate of a freely evolving coherent matter wave. In this paper we explore the potential for space-based experiments to extend the limits of ultracold atoms utilizing not just microgravity, but also other aspects of the space environment such as exceptionally good vacuums and extremely cold temperatures. The tantalizing possibility that such experiments may one day be able to probe physics of quantum objects with masses approaching the Planck mass is discussed
BPD-MA-mediated photosensitization in vitro and in vivo: cellular adhesion and β1 integrin expression in ovarian cancer cells
In vivo high-resolution fluorescence microendoscopy for ovarian cancer detection and treatment monitoring
EPIdemiology of Surgery-Associated Acute Kidney Injury (EPIS-AKI) : Study protocol for a multicentre, observational trial
More than 300 million surgical procedures are performed each year. Acute kidney injury (AKI) is a common complication after major surgery and is associated with adverse short-term and long-term outcomes. However, there is a large variation in the incidence of reported AKI rates. The establishment of an accurate epidemiology of surgery-associated AKI is important for healthcare policy, quality initiatives, clinical trials, as well as for improving guidelines. The objective of the Epidemiology of Surgery-associated Acute Kidney Injury (EPIS-AKI) trial is to prospectively evaluate the epidemiology of AKI after major surgery using the latest Kidney Disease: Improving Global Outcomes (KDIGO) consensus definition of AKI. EPIS-AKI is an international prospective, observational, multicentre cohort study including 10 000 patients undergoing major surgery who are subsequently admitted to the ICU or a similar high dependency unit. The primary endpoint is the incidence of AKI within 72 hours after surgery according to the KDIGO criteria. Secondary endpoints include use of renal replacement therapy (RRT), mortality during ICU and hospital stay, length of ICU and hospital stay and major adverse kidney events (combined endpoint consisting of persistent renal dysfunction, RRT and mortality) at day 90. Further, we will evaluate preoperative and intraoperative risk factors affecting the incidence of postoperative AKI. In an add-on analysis, we will assess urinary biomarkers for early detection of AKI. EPIS-AKI has been approved by the leading Ethics Committee of the Medical Council North Rhine-Westphalia, of the Westphalian Wilhelms-University Münster and the corresponding Ethics Committee at each participating site. Results will be disseminated widely and published in peer-reviewed journals, presented at conferences and used to design further AKI-related trials. Trial registration number NCT04165369
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