903 research outputs found
Unsupervised learning for cross-domain medical image synthesis using deformation invariant cycle consistency networks
Recently, the cycle-consistent generative adversarial networks (CycleGAN) has
been widely used for synthesis of multi-domain medical images. The
domain-specific nonlinear deformations captured by CycleGAN make the
synthesized images difficult to be used for some applications, for example,
generating pseudo-CT for PET-MR attenuation correction. This paper presents a
deformation-invariant CycleGAN (DicycleGAN) method using deformable
convolutional layers and new cycle-consistency losses. Its robustness dealing
with data that suffer from domain-specific nonlinear deformations has been
evaluated through comparison experiments performed on a multi-sequence brain MR
dataset and a multi-modality abdominal dataset. Our method has displayed its
ability to generate synthesized data that is aligned with the source while
maintaining a proper quality of signal compared to CycleGAN-generated data. The
proposed model also obtained comparable performance with CycleGAN when data
from the source and target domains are alignable through simple affine
transformations
Bifurcation of a reversible Hamiltonian system from a fixed point with fourfold eigenvalue zero
Wigner function quantum molecular dynamics
Classical molecular dynamics (MD) is a well established and powerful tool in
various fields of science, e.g. chemistry, plasma physics, cluster physics and
condensed matter physics. Objects of investigation are few-body systems and
many-body systems as well. The broadness and level of sophistication of this
technique is documented in many monographs and reviews, see for example
\cite{Allan,Frenkel,mdhere}. Here we discuss the extension of MD to quantum
systems (QMD). There have been many attempts in this direction which differ
from one another, depending on the type of system under consideration. One
direction of QMD has been developed for condensed matter systems and will not
discussed here, e.g. \cite{fermid}. In this chapter we are dealing with unbound
electrons as they occur in gases, fluids or plasmas. Here, one strategy is to
replace classical point particles by wave packets, e.g.
\cite{fermid,KTR94,zwicknagel06} which is quite successful. At the same time,
this method struggles with problems related to the dispersion of such a packet
and difficulties to properly describe strong electron-ion interaction and bound
state formation. We, therefore, avoid such restrictions and consider a
completely general alternative approach. We start discussion of quantum
dynamics from a general consideration of quantum distribution functions.Comment: 18 pages, based on lecture at Hareaus school on computational phyics,
Greifswald, September 200
Raman light scattering study and microstructural analysis of epitaxial films of the electron-doped superconductor La_{2-x}Ce_{x}CuO_{4}
We present a detailed temperature-dependent Raman light scattering study of
optical phonons in molecular-beam-epitaxy-grown films of the electron-doped
superconductor La_{2-x}Ce_{x}CuO_{4} close to optimal doping (x ~ 0.08, T_c =
29 K and x ~ 0.1, T_c = 27 K). The main focus of this work is a detailed
characterization and microstructural analysis of the films. Based on
micro-Raman spectroscopy in combination with x-ray diffraction,
energy-dispersive x-ray analysis, and scanning electron microscopy, some of the
observed phonon modes can be attributed to micron-sized inclusions of Cu_{2}O.
In the slightly underdoped film (x ~ 0.08), both the Cu_{2}O modes and others
that can be assigned to the La_{2-x}Ce_{x}CuO_{4} matrix show pronounced
softening and narrowing upon cooling below T ~ T_c. Based on control
measurements on commercial Cu_{2}O powders and on a comparison to prior Raman
scattering studies of other high-temperature superconductors, we speculate that
proximity effects at La_{2-x}Ce_{x}CuO_{4}/Cu_{2}O interfaces may be
responsible for these anomalies. Experiments on the slightly overdoped
La_{2-x}Ce_{x}CuO_{4} film (x ~ 0.1) did not reveal comparable phonon
anomalies.Comment: 7 pages, 8 figure
Five-Year Change in Visceral Adipose Tissue Quantity in a Minority Cohort: The Insulin Resistance Atherosclerosis Study (IRAS) Family Study
Disposition Index, Glucose Effectiveness, and Conversion to Type 2 Diabetes: The Insulin Resistance Atherosclerosis Study (IRAS)
Copper-free dual labeling of DNA by triazines and cyclopropenes as minimal orthogonal and bioorthogonal functions
Experimental Quantum Teleportation of a Two-Qubit Composite System
Quantum teleportation, a way to transfer the state of a quantum system from
one location to another, is central to quantum communication and plays an
important role in a number of quantum computation protocols. Previous
experimental demonstrations have been implemented with photonic or ionic
qubits. Very recently long-distance teleportation and open-destination
teleportation have also been realized. Until now, previous experiments have
only been able to teleport single qubits. However, since teleportation of
single qubits is insufficient for a large-scale realization of quantum
communication and computation2-5, teleportation of a composite system
containing two or more qubits has been seen as a long-standing goal in quantum
information science. Here, we present the experimental realization of quantum
teleportation of a two-qubit composite system. In the experiment, we develop
and exploit a six-photon interferometer to teleport an arbitrary polarization
state of two photons. The observed teleportation fidelities for different
initial states are all well beyond the state estimation limit of 0.40 for a
two-qubit system. Not only does our six-photon interferometer provide an
important step towards teleportation of a complex system, it will also enable
future experimental investigations on a number of fundamental quantum
communication and computation protocols such as multi-stage realization of
quantum-relay, fault-tolerant quantum computation, universal quantum
error-correction and one-way quantum computation.Comment: 16pages, 4 figure
Use of troponins in the classification of myocardial infarction from electronic health records. The Atherosclerosis Risk in Communities (ARIC) Study
Objective: Electronic health record (EHR) data are underutilized for abstracting classification criteria for heart disease. We compared extraction of EHR data on troponin I and T levels with human abstraction. Methods: Using EHR for hospitalizations identified through the Atherosclerosis Risk in Communities (ARIC) Study in four US hospitals, we compared blood levels of troponins I and T extracted from EHR structured data elements with levels obtained through data abstraction by human abstractors to 3 decimal places. Observations were divided randomly 50/50 into training and validation sets. Bayesian multilevel logistic regression models were used to estimate agreement by hospital in first and maximum troponin levels, troponin assessment date, troponin upper limit of normal (ULN), and classification of troponin levels as normal (2Ć ULN), or missing. Results: Estimated overall agreement in first measured troponin level in the validation data was 88.2% (95% credible interval: 65.0%-97.5%) and 95.5% (91.2-98.2%) for the maximum troponin level observed during hospitalization. The largest variation in probability of agreement was for first troponin measured, which ranged from 66.4% to 95.8% among hospitals. Conclusion: Extraction of maximum troponin values during a hospitalization from EHR structured data is feasible and accurate
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