1,721,247 research outputs found
Tumor Growth Rate of Luminal and Nonluminal Invasive Breast Cancer Calculated on MRI Imaging
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Amplification of the quantum superposition macroscopicity of a flux qubit by a magnetized Bose gas
No full textWe calculate a measure of superposition macroscopicity M for a superposition of screening current states in a superconducting flux qubit (SFQ), by relating M to the action of an instanton trajectory connecting the potential wells of the flux qubit. When a magnetized Bose-Einstein condensed (BEC) gas containing N-B similar to O (10(6)) atoms is brought into a O(1) mu m proximity of the flux qubit in an experimentally realistic geometry, we demonstrate the appearance of a twofold to fivefold amplification of M over the bare value without the BEC, by calculating the instanton trajectory action from the microscopically derived effective flux Lagrangian of a hybrid quantum system composed of the flux qubit and a spin-F atomic Bose gas. Exploiting the connection between M and the maximal metrological usefulness of a multimode superposition state, we show that amplification of M in the ground state of the hybrid system is equivalent to a decrease in the quantum Cramer-Rao bound for estimation of an externally applied flux. Our result therefore demonstrates the increased usefulness of the BEC-SFQ hybrid system as a sensor of ultraweak magnetic fields below the standard quantum limit.N
Quantum sine-Gordon dynamics on analogue curved spacetime in a weakly imperfect scalar Bose gas
No full textUsing the coherent state functional integral expression of the partition function, we show that the sine-Gordon model on an analogue curved spacetime arises as the effective quantum field theory for phase fluctuations of a weakly imperfect Bose gas on an incompressible background superfluid flow when these fluctuations are restricted to a subspace of the single-particle Hilbert space. We consider bipartitions of the single-particle Hilbert space relevant to experiments on ultracold bosonic atomic or molecular gases, including, e.g., restriction to high-or low-energy sectors of the dynamics and spatial bipartition corresponding to tunnel-coupled planar Bose gases. By assuming full unitary quantum control in the low-energy subspace of a trapped gas, we show that (1) appropriately tuning the particle number statistics of the lowest-energy mode partially decouples the low-and high-energy sectors, allowing any low-energy single-particle wave function to define a background for sine-Gordon dynamics on curved spacetime and (2) macroscopic occupation of a quantum superposition of two states of the lowest two modes produces an analogue curved spacetime depending on two background flows, with respective weights continuously dependent on the corresponding weights of the superposed quantum states.N
Intrinsic measurement errors for the speed of light in vacuum
No full textThe speed of light in vacuum, one of the most important and precisely measured natural constants, is fixed by convention to c = 299 792 458 m s(-1). Advanced theories predict possible deviations from this universal value, or even quantum fluctuations of c. Combining arguments from quantum parameter estimation theory and classical general relativity, we here establish rigorously the existence of lower bounds on the uncertainty to which the speed of light in vacuum can be determined in a given region of space-time, subject to several reasonable restrictions. They provide a novel perspective on the experimental falsifiability of predictions for the quantum fluctuations of space-time.OAIID:RECH_ACHV_DSTSH_NO:T201721132RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A078167CITE_RATE:3.283DEPT_NM:물리·천문학부EMAIL:[email protected]_YN:YN
Review of clinical studies and first clinical experiences with a commercially available cone-beam breast CT in Europe
No full textThe dedicated cone-beam breast computed tomography (CBBCT) is a new and promising imaging modality which provides isotropic, 3D images of the breast with high spatial and contrast resolution. Non-contrast and contrast-enhanced CBBCT (CE-CBBCT) was superior to mammography for the visualization of breast masses, especially in patients with dense breast tissue. CE-CBBCT accurately detects DCIS and distinguishes it from benign causes of microcalcifications when compared with non-contrast CBBCT and mammography. The purpose of this report is to describe the technology and its possible indications, and to present the first results from recent clinical studies, illustrating these with our own image examples. (C) 2016 Elsevier Inc. All rights reserved
Probing the Scale Invariance of the Inflationary Power Spectrum in Expanding Quasi-Two-Dimensional Dipolar Condensates
No full textWe consider an analogue de Sitter cosmos in an expanding quasi-two-dimensional Bose-Einstein condensate with dominant dipole-dipole interactions between the atoms or molecules in the ultracold gas. It is demonstrated that a hallmark signature of inflationary cosmology, the scale invariance of the power spectrum of inflaton field correlations, experiences strong modifications when, at the initial stage of expansion, the excitation spectrum displays a roton minimum. Dipolar quantum gases thus furnish a viable laboratory tool to experimentally investigate, with well-defined and controllable initial conditions, whether primordial oscillation spectra deviating from Lorentz invariance at trans-Planckian momenta violate standard predictions of inflationary cosmology.OAIID:RECH_ACHV_DSTSH_NO:T201721131RECH_ACHV_FG:RR00200001ADJUST_YN:EMP_ID:A078167CITE_RATE:8.839DEPT_NM:물리·천문학부EMAIL:[email protected]_YN:YN
Pre- and post-contrast versus post-contrast cone-beam breast CT: can we reduce radiation exposure while maintaining diagnostic accuracy?
No full textFeasibility of Vacuum-Assisted Breast Cone-Beam CT–Guided Biopsy and Comparison With Prone Stereotactic Biopsy
No full textOBJECTIVE. The feasibility of breast vacuum-assisted biopsy (VAB) guided by cone-beam CT (CBCT) was assessed. The initial clinical performance of CT-guided breast VAB was compared with that of established prone stereotactic VAB. MATERIALS AND METHODS. In this retrospective clinical trial, VABs were performed for women with mammographically suspicious breast lesions using a dedicated breast CBCT protocol. The technical success rate, total intervention time, and complications were documented and compared with examinations performed by prone stereotactic VAB. RESULTS. Between June 2015 and March 2016, 65 patients with 68 target lesions underwent image-guided VAB. CT-guided VAB was performed for 29 patients with 31 lesions. Thirty-six patients with 37 lesions underwent prone stereotactic VAB. The type of lesion was not different between the two groups (p = 0.135). Technical success rate was achieved in 31 of 33 lesions (93.9%) with CT-guided VAB versus 37 of 38 lesions (97.4%) with prone stereotactic VAB. The mean (+/- SD) total intervention time was 22.7 +/- 8.4 minutes for CT-guided VAB versus 28.8 +/- 9.4 minutes for prone stereotactic VAB (p < 0.05). Reidentifying and targeting lesions took about the same time for both systems (p = 0.362). The time for tissue sampling was significantly faster with CT-guided VAB (p < 0.05). No major complications were observed with either system. CONCLUSION. CT-guided VAB is safe and feasible using the currently available breast CBCT protocol. The mean total intervention time to complete VAB and the time for tissue sampling was significantly faster using CT-guided VAB in comparison with prone stereotactic VAB
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