65 research outputs found
A trapped single ion inside a Bose-Einstein condensate
Improved control of the motional and internal quantum states of ultracold
neutral atoms and ions has opened intriguing possibilities for quantum
simulation and quantum computation. Many-body effects have been explored with
hundreds of thousands of quantum-degenerate neutral atoms and coherent
light-matter interfaces have been built. Systems of single or a few trapped
ions have been used to demonstrate universal quantum computing algorithms and
to detect variations of fundamental constants in precision atomic clocks. Until
now, atomic quantum gases and single trapped ions have been treated separately
in experiments. Here we investigate whether they can be advantageously combined
into one hybrid system, by exploring the immersion of a single trapped ion into
a Bose-Einstein condensate of neutral atoms. We demonstrate independent control
over the two components within the hybrid system, study the fundamental
interaction processes and observe sympathetic cooling of the single ion by the
condensate. Our experiment calls for further research into the possibility of
using this technique for the continuous cooling of quantum computers. We also
anticipate that it will lead to explorations of entanglement in hybrid quantum
systems and to fundamental studies of the decoherence of a single, locally
controlled impurity particle coupled to a quantum environment
Quantum Holographic Encoding in a Two-dimensional Electron Gas
The advent of bottom-up atomic manipulation heralded a new horizon for
attainable information density, as it allowed a bit of information to be
represented by a single atom. The discrete spacing between atoms in condensed
matter has thus set a rigid limit on the maximum possible information density.
While modern technologies are still far from this scale, all theoretical
downscaling of devices terminates at this spatial limit. Here, however, we
break this barrier with electronic quantum encoding scaled to subatomic
densities. We use atomic manipulation to first construct open
nanostructures--"molecular holograms"--which in turn concentrate information
into a medium free of lattice constraints: the quantum states of a
two-dimensional degenerate Fermi gas of electrons. The information embedded in
the holograms is transcoded at even smaller length scales into an atomically
uniform area of a copper surface, where it is densely projected into both two
spatial degrees of freedom and a third holographic dimension mapped to energy.
In analogy to optical volume holography, this requires precise amplitude and
phase engineering of electron wavefunctions to assemble pages of information
volumetrically. This data is read out by mapping the energy-resolved electron
density of states with a scanning tunnelling microscope. As the projection and
readout are both extremely near-field, and because we use native quantum states
rather than an external beam, we are not limited by lensing or collimation and
can create electronically projected objects with features as small as ~0.3 nm.
These techniques reach unprecedented densities exceeding 20 bits/nm2 and place
tens of bits into a single fermionic state.Comment: Published online 25 January 2009 in Nature Nanotechnology; 12 page
manuscript (including 4 figures) + 2 page supplement (including 1 figure);
supplementary movie available at http://mota.stanford.ed
High ALDH Activity Identifies Chemotherapy-Resistant Ewing's Sarcoma Stem Cells That Retain Sensitivity to EWS-FLI1 Inhibition
Cancer stem cells are a chemotherapy-resistant population capable of self-renewal and of regenerating the bulk tumor, thereby causing relapse and patient death. Ewing's sarcoma, the second most common form of bone tumor in adolescents and young adults, follows a clinical pattern consistent with the Cancer Stem Cell model - remission is easily achieved, even for patients with metastatic disease, but relapse remains frequent and is usually fatal.We have isolated a subpopulation of Ewing's sarcoma cells, from both human cell lines and human xenografts grown in immune deficient mice, which express high aldehyde dehydrogenase (ALDH(high)) activity and are enriched for clonogenicity, sphere-formation, and tumor initiation. The ALDH(high) cells are resistant to chemotherapy in vitro, but this can be overcome by the ATP binding cassette transport protein inhibitor, verapamil. Importantly, these cells are not resistant to YK-4-279, a small molecule inhibitor of EWS-FLI1 that is selectively toxic to Ewing's sarcoma cells both in vitro and in vivo.Ewing's sarcoma contains an ALDH(high) stem-like population of chemotherapy-resistant cells that retain sensitivity to EWS-FLI1 inhibition. Inhibiting the EWS-FLI1 oncoprotein may prove to be an effective means of improving patient outcomes by targeting Ewing's sarcoma stem cells that survive standard chemotherapy
An immune dysfunction score for stratification of patients with acute infection based on whole-blood gene expression
Dysregulated host responses to infection can lead to organ dysfunction and sepsis, causing millions of global deaths each year. To alleviate this burden, improved prognostication and biomarkers of response are urgently needed. We investigated the use of whole-blood transcriptomics for stratification of patients with severe infection by integrating data from 3149 samples from patients with sepsis due to community-acquired pneumonia or fecal peritonitis admitted to intensive care and healthy individuals into a gene expression reference map. We used this map to derive a quantitative sepsis response signature (SRSq) score reflective of immune dysfunction and predictive of clinical outcomes, which can be estimated using a 7- or 12-gene signature. Last, we built a machine learning framework, SepstratifieR, to deploy SRSq in adult and pediatric bacterial and viral sepsis, H1N1 influenza, and COVID-19, demonstrating clinically relevant stratification across diseases and revealing some of the physiological alterations linking immune dysregulation to mortality. Our method enables early identification of individuals with dysfunctional immune profiles, bringing us closer to precision medicine in infection
An immune dysfunction score for stratification of patients with acute infection based on whole-blood gene expression.
Dysregulated host responses to infection can lead to organ dysfunction and sepsis, causing millions of global deaths each year. To alleviate this burden, improved prognostication and biomarkers of response are urgently needed. We investigated the use of whole-blood transcriptomics for stratification of patients with severe infection by integrating data from 3149 samples from patients with sepsis due to community-acquired pneumonia or fecal peritonitis admitted to intensive care and healthy individuals into a gene expression reference map. We used this map to derive a quantitative sepsis response signature (SRSq) score reflective of immune dysfunction and predictive of clinical outcomes, which can be estimated using a 7- or 12-gene signature. Last, we built a machine learning framework, SepstratifieR, to deploy SRSq in adult and pediatric bacterial and viral sepsis, H1N1 influenza, and COVID-19, demonstrating clinically relevant stratification across diseases and revealing some of the physiological alterations linking immune dysregulation to mortality. Our method enables early identification of individuals with dysfunctional immune profiles, bringing us closer to precision medicine in infection
MBE growth of (110) refractory metals on a-plane sapphire
Molecular growth epitaxy (MBE) growth of (110) refractory metals on a-plane sapphire was discussed. Reflection high-energy electron diffraction (RHEED) and X-ray diffraction (XRD) techniques were used. Results showed that both Nb and Ta grow in an approximate layer-by-layer mode and growth in Mo is attributed to greater mismatch with sapphire
Determination of hydrogen ordering within the ss-RH2+x phase (R = Ho, Y) using electron diffraction techniques
Determination of hydrogen ordering within the ss-RH2+x phase (R = Ho, Y) using electron diffraction techniques
Structure of DyFe2/YFe2 Laves phase superlattices grown by molecular beam epitaxy
The crystal structure of a series of six high quality single crystal Laves phase superlattice samples, of structure [t1 ÅDyFe2/t2ÅYFe2]N, grown by molecular beam epitaxy have been probed using a high resolution triple crystal x-ray diffractometer. A study of the scattering near the 2 2 0, 4 4 0 and 2 6 2 reflections has revealed the presence of several superlattice peaks, showing that the samples exhibit a high degree of superlattice modulation. The typical mosaic spread is less than 0.9°, while the superlattice coherence lengths are typically 2000 Å. Fitting of a model to the data using a differential evolution algorithm with a Rietveld refinement has confirmed the high quality of these samples and shows that the interface widths are typically ∼20 Å. Measurements of the in-plane and out-of-plane lattice parameters show that the samples are subjected to a shear that is slightly anisotropic in the plane. Transverse scans through the Bragg and superlattice peaks show that the width is mainly dominated by a mosaic crystal effect, with a small contribution arising from the correlated roughness at the bilayer interfaces. Finally, high resolution electron microscopy images show directly that these superlattices exhibit a high degree of modulation
Misfit dislocations of epitaxial (110) niobium parallel to (11(2)over-bar-0) sapphire interfaces grown by molecular beam epitaxy
- …