4,411 research outputs found
Deterministic delivery of remote entanglement on a quantum network
Large-scale quantum networks promise to enable secure communication,
distributed quantum computing, enhanced sensing and fundamental tests of
quantum mechanics through the distribution of entanglement across nodes. Moving
beyond current two-node networks requires the rate of entanglement generation
between nodes to exceed their decoherence rates. Beyond this critical
threshold, intrinsically probabilistic entangling protocols can be subsumed
into a powerful building block that deterministically provides remote entangled
links at pre-specified times. Here we surpass this threshold using diamond spin
qubit nodes separated by 2 metres. We realise a fully heralded single-photon
entanglement protocol that achieves entangling rates up to 39 Hz, three orders
of magnitude higher than previously demonstrated two-photon protocols on this
platform. At the same time, we suppress the decoherence rate of remote
entangled states to 5 Hz by dynamical decoupling. By combining these results
with efficient charge-state control and mitigation of spectral diffusion, we
are able to deterministically deliver a fresh remote state with average
entanglement fidelity exceeding 0.5 at every clock cycle of 100 ms
without any pre- or post-selection. These results demonstrate a key building
block for extended quantum networks and open the door to entanglement
distribution across multiple remote nodes.Comment: v2 - updated to include relevant citatio
An Improved Algorithm for Generating Database Transactions from Relational Algebra Specifications
Alloy is a lightweight modeling formalism based on relational algebra. In
prior work with Fisler, Giannakopoulos, Krishnamurthi, and Yoo, we have
presented a tool, Alchemy, that compiles Alloy specifications into
implementations that execute against persistent databases. The foundation of
Alchemy is an algorithm for rewriting relational algebra formulas into code for
database transactions. In this paper we report on recent progress in improving
the robustness and efficiency of this transformation
Outcomes of acute versus subacute scapholunate ligament repair
PURPOSE: This study investigated the long-term outcomes of direct scapholunate ligament (SLL) repairs with or without dorsal capsulodesis performed within 6 weeks (acute repair) of a SLL tear versus 6 to 12 weeks following injury (subacute repair).
METHODS: A review of medical records from April 1996 to April 2012 identified 24 patients who underwent SLL repair (12 acute, 12 subacute). Patients returned to the clinic for radiographic examinations of the injured wrist, standardized physical examinations, and validated questionnaires.
RESULTS: The mean follow-up times for the acute and subacute groups were 7.2 and 6.2 years, respectively. At the final examination, patients with acute surgery regained more wrist extension (acute = 55°, subacute = 47°). The total wrist flexion-extension arcs, grip strengths, pinch strengths, and patient-rated outcome scores were found to be similar between groups. The final scapholunate gap, scapholunate angle, and the prevalence of arthritis were also found to be similar between the acute and subacute groups.
CONCLUSIONS: Although SLL repair is more commonly recommended for treatment of acute SLL injuries, there were no significant long-term differences between acute and subacute SLL surgeries (repair ± capsulodesis).
TYPE OF STUDY/LEVEL OF EVIDENCE: Prognostic III
Ultrasound Imaging of Gene Expression in Mammalian Cells
The study of cellular processes occurring inside intact organisms requires methods to visualize cellular functions such as gene expression in deep tissues. Ultrasound is a widely used biomedical technology enabling noninvasive imaging with high spatial and temporal resolution. However, no genetically encoded molecular reporters are available to connect ultrasound contrast to gene expression in mammalian cells. To address this limitation, we introduce mammalian acoustic reporter genes. Starting with a gene cluster derived from bacteria, we engineered a eukaryotic genetic program whose introduction into mammalian cells results in the expression of intracellular air-filled protein nanostructures called gas vesicles, which produce ultrasound contrast. Mammalian acoustic reporter genes allow cells to be visualized at volumetric densities below 0.5% and permit high-resolution imaging of gene expression in living animals
Asteroid Redirect Mission Concept: A Bold Approach for Utilizing Space Resources
The utilization of natural resources from asteroids is an idea that is older than the Space Age. The technologies are now available to transform this endeavour from an idea into reality. The Asteroid Redirect Mission (ARM) is a mission concept which includes the goal of robotically returning a small Near-Earth Asteroid (NEA) or a multi-ton boulder from a large NEA to cislunar space in the mid 2020's using an advanced Solar Electric Propulsion (SEP) vehicle and currently available technologies. The paradigm shift enabled by the ARM concept would allow in-situ resource utilization (ISRU) to be used at the human mission departure location (i.e., cislunar space) versus exclusively at the deep-space mission destination. This approach drastically reduces the barriers associated with utilizing ISRU for human deep-space missions. The successful testing of ISRU techniques and associated equipment could enable large-scale commercial ISRU operations to become a reality and enable a future space-based economy utilizing processed asteroidal materials. This paper provides an overview of the ARM concept and discusses the mission objectives, key technologies, and capabilities associated with the mission, as well as how the ARM and associated operations would benefit humanity's quest for the exploration and settlement of space
Source placement error for permanent implant of the prostate
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/134896/1/mp8058.pd
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