Four-Dimensional Geometry: An Introduction.
ERIC Educational Resources Information Center
Hess, Adrien L.
This document presents six chapters on four-dimensional geometry, whose titles are: (1) A Brief History; (2) What Is Four-Dimensional Geometry?; (3) Selected Drawings and Models; (4) How to Study the Configurations; (5) Selected Topics; and (6) Applications. The text, suitable for students in advanced levels of secondary school mathematics,…
Cohomology of real four-dimensional triquadrics
NASA Astrophysics Data System (ADS)
Krasnov, Vyacheslav A.
2012-10-01
We consider non-singular intersections of three real six-dimensional quadrics. They are referred to for brevity as real four-dimensional triquadrics. We calculate the dimensions of their cohomology spaces with coefficients in the field of two elements.
On four dimensional N = 3 superconformal theories
NASA Astrophysics Data System (ADS)
Aharony, Ofer; Evtikhiev, Mikhail
2016-04-01
In this note we study four dimensional theories with N = 3 superconformal symmetry, that do not also have N = 4 supersymmetry. No examples of such theories are known, but their existence is also not ruled out. We analyze several properties that such theories must have. We show that their conformal anomalies obey a = c. Using the N = 3 superconformal algebra, we show that they do not have any exactly marginal deformations preserving N = 3 supersymmetry, or global symmetries (except for their R-symmetries). Finally, we analyze the possible dimensions of chiral operators labeling their moduli space.
String breaking in four dimensional lattice QCD
Duncan, A.; Eichten, E.; Thacker, H.
2001-06-01
Virtual quark pair screening leads to breaking of the string between fundamental representation quarks in QCD. For unquenched four dimensional lattice QCD, this (so far elusive) phenomenon is studied using the recently developed truncated determinant algorithm (TDA). The dynamical configurations were generated on a 650 MHz PC. Quark eigenmodes up to 420 MeV are included exactly in these TDA studies performed at low quark mass on large coarse [but O(a{sup 2}) improved] lattices. A study of Wilson line correlators in Coulomb gauge extracted from an ensemble of 1000 two-flavor dynamical configurations reveals evidence for flattening of the string tension at distances R{approx}>1 fm.
Four-dimensional visualization of rising microbubbles
NASA Astrophysics Data System (ADS)
Jung, Ji Won; Jeon, Hyung Min; Pyo, Jaeyeon; Lim, Jae-Hong; Weon, Byung Mook; Kohmura, Yoshiki; Ishikawa, Tetsuya; Je, Jung Ho
2014-05-01
Four-dimensional imaging, which indicates imaging in three spatial dimensions as a function of time, provides useful evidence to investigate the interactions of rising bubbles. However, this has been largely unexplored for microbubbles, mostly due to problems associated with strong light scattering and shallow depth of field in optical imaging. Here, tracking x-ray microtomography is used to visualize rising microbubbles in four dimensions. Bubbles are tracked by moving the cell to account for their rise velocity. The sizes, shapes, time-dependent positions, and velocities of individual rising microbubbles are clearly identified, despite substantial overlaps between bubbles in the field of view. Our tracking x-ray microtomography affords opportunities for understanding bubble-bubble (or particle) interactions at microscales - important in various fields such as microfluidics, biomechanics, and floatation.
Quantum teleportation of four-dimensional qudits
Al-Amri, M.; Evers, Joerg; Zubairy, M. Suhail
2010-08-15
A protocol for the teleportation of arbitrary quantum states of four-dimensional qudits is presented. The qudit to be teleported is encoded in the combined state of two ensembles of atoms placed in a cavity at the sender's side. The receiver uses a similar setup, with his atoms prepared in a particular initial state. The teleportation protocol then consists of adiabatic mapping of the ensemble states onto photonic degrees of freedom, which are then directed onto a specific beam splitter and detection setup. For part of the measurement outcome, the qudit state is fully transferred to the receiver. Other detection events lead to partial teleportation or failed teleportation attempts. The interpretation of the different detection outcomes and possible ways of improving the full teleportation probability are discussed.
Four-dimensional visualization of rising microbubbles
NASA Astrophysics Data System (ADS)
Je, Jung Ho; Jung, Ji Won; Pyo, Jaeyeon; Lim, Jae-Hong
2014-11-01
Four-dimensional imaging, which indicates imaging in three spatial dimensions as a function of time, provides useful evidence to investigate the interactions of rising bubbles. However, this has been largely unexplored for microbubbles, mostly due to problems associated with strong light scattering and shallow depth of field in optical imaging. Here, we developed tracking x-ray microtomography that is capable of visualizing rising microbubbles in four dimensions. Bubbles are tracked by moving the in-situ cell to account for their rise velocity. The sizes, shapes, time-dependent positions, and velocities of individual rising microbubbles are clearly identified, despite substantial overlaps between bubbles in the field of view. Our tracking x-ray microtomography affords opportunities for understanding bubble-bubble (or particle) interactions at microscales - important in various fields such as microfluidics, biomechanics, and floatation.
Generic Submanifolds of Nearly Kaehler Manifolds with Certain Parallel Canonical Structure
Zhu, Qingqing; Yang, Biaogui
2014-01-01
The class of generic submanifold includes all real hypersurfaces, complex submanifolds, totally real submanifolds, and CR-submanifolds. In this paper we initiate the study of generic submanifolds in a nearly Kaehler manifold from differential geometric point of view. Some fundamental results in this paper will be obtained. PMID:27355057
FASTSPECT: A four-dimensional brain imager
Patton, D.D.; Barrett, H.H.; Chen, J.C. |
1994-05-01
The exact location of a lesion in the brain is most critical. High-resolution quantitative 4-dimensional brain imaging would offer improvement in detecting and characterizing brain lesions over state-of-the-art SPECT systems. We report the first clinical brain images on FASTSPECT (Four-dimensional Arizona Stationary SPECT), a fixed imaging system based on 24 modular 10 cm x 10 cm gamma cameras in 2 rings (13+11) about the bead. Each module views the entire brain continuously from a different perspective through one or more pinhole apertures. The system gathers true 3-dimensional whole-brain data it 1-2 frame/sec, fully adequate for vascular dynamics, and is therefore a 4-dimensional imaging system (dynamic SPECT). To calibrate the system a (3.3 mm){sup 3} point source of Tc-99m is stepped through each voxel in the object space. We measure the response of each detector element on each modular camera to the source at each position. The resulting system matrix (dimensions approximately 100,000 x 160,000) is compressed, stored and used in the iterative reconstruction algorithm. Three volunteers, blindfolded for 20 min to suppress visual cortical uptake, were imaged after bolus IV injection of 30 mCi (1.11 GBq) Tc-99m HMPAO. Dynamic images at 2 sec/frame clearly showed common and internal carotid arteries, and anterior and middle cerebral artery groups. Static images (11 million counts in 20 min imaging time) clearly showed the cerebral cortex and white matter, cerebellar cortex and white matter, thalami, caudate, lentiform nuclei, cingulate gyrus, brain stem, and brachium pontis. Distinguishable only with difficulty were putamen from globus pallidus, ventral from dorsal thalamus, and cerebrospinal fluid from white matter. Comparison with concurrent conventional single-headed SPECT images in the same subjects showed significantly better anatomic definition in the FASTSPECT images. Conventional SPECT is incapable of full-brain dynamic imaging.
Hermitian geometry of 6-dimensional submanifolds of the Cayley algebra
Banaru, M B
2002-06-30
Orientable 6-dimensional submanifolds (of general type) of the Cayley algebra are investigated on which the 3-fold vector cross products in the octave algebra induce a Hermitian structure. It is shown that such submanifolds of the Cayley algebra are minimal, non-compact, and para-Kaehler, their holomorphic bisectional curvature is positive and vanishes only at the geodesic points. It is also proved that cosymplectic hypersurfaces of 6-dimensional Hermitian submanifolds of the octave algebra are ruled. A simple test for the minimality of such surfaces is obtained. It is shown that 6-dimensional submanifolds of the Cayley algebra satisfying the axiom of g-cosymplectic hypersurfaces are Kaehler manifolds.
General flat four-dimensional world pictures and clock systems
NASA Technical Reports Server (NTRS)
Hsu, J. P.; Underwood, J. A.
1978-01-01
We explore the mathematical structure and the physical implications of a general four-dimensional symmetry framework which is consistent with the Poincare-Einstein principle of relativity for physical laws and with experiments. In particular, we discuss a four-dimensional framework in which all observers in different frames use one and the same grid of clocks. The general framework includes special relativity and a recently proposed new four-dimensional symmetry with a nonuniversal light speed as two special simple cases. The connection between the properties of light propagation and the convention concerning clock systems is also discussed, and is seen to be nonunique within the four-dimensional framework.
2013-01-01
Background Genome-wide association studies have become very popular in identifying genetic contributions to phenotypes. Millions of SNPs are being tested for their association with diseases and traits using linear or logistic regression models. This conceptually simple strategy encounters the following computational issues: a large number of tests and very large genotype files (many Gigabytes) which cannot be directly loaded into the software memory. One of the solutions applied on a grand scale is cluster computing involving large-scale resources. We show how to speed up the computations using matrix operations in pure R code. Results We improve speed: computation time from 6 hours is reduced to 10-15 minutes. Our approach can handle essentially an unlimited amount of covariates efficiently, using projections. Data files in GWAS are vast and reading them into computer memory becomes an important issue. However, much improvement can be made if the data is structured beforehand in a way allowing for easy access to blocks of SNPs. We propose several solutions based on the R packages ff and ncdf. We adapted the semi-parallel computations for logistic regression. We show that in a typical GWAS setting, where SNP effects are very small, we do not lose any precision and our computations are few hundreds times faster than standard procedures. Conclusions We provide very fast algorithms for GWAS written in pure R code. We also show how to rearrange SNP data for fast access. PMID:23711206
On the four-dimensional formulation of dimensionally regulated amplitudes
NASA Astrophysics Data System (ADS)
Fazio, A. R.; Mastrolia, P.; Mirabella, E.; Torres Bobadilla, W. J.
2014-12-01
Elaborating on the four-dimensional helicity scheme, we propose a pure four-dimensional formulation (FDF) of the -dimensional regularization of one-loop scattering amplitudes. In our formulation particles propagating inside the loop are represented by massive internal states regulating the divergences. The latter obey Feynman rules containing multiplicative selection rules which automatically account for the effects of the extra-dimensional regulating terms of the amplitude. We present explicit representations of the polarization and helicity states of the four-dimensional particles propagating in the loop. They allow for a complete, four-dimensional, unitarity-based construction of -dimensional amplitudes. Generalized unitarity within the FDF does not require any higher-dimensional extension of the Clifford and the spinor algebra. Finally we show how the FDF allows for the recursive construction of -dimensional one-loop integrands, generalizing the four-dimensional open-loop approach.
Arrangements of codimension-one submanifolds
Shnurnikov, Igor' N
2012-09-30
We study the number f of connected components in the complement to a finite set (arrangement) of closed submanifolds of codimension 1 in a closed manifold M. In the case of arrangements of closed geodesics on an isohedral tetrahedron, we find all possible values for the number fof connected components. We prove that the set of numbers that cannot be realized by the number f of an arrangement of n {>=} 71 projective planes in the three-dimensional real projective space is contained in the similar known set of numbers that are not realizable by arrangements of n lines on the projective plane. For Riemannian surfaces M we express the number f via a regular neighbourhood of a union of immersed circles and the multiplicities of their intersection points. For m-dimensional Lobachevskii space we find the set of all possible numbers f for hyperplane arrangements. Bibliography: 18 titles.
Splitting a simple homotopy equivalence along a submanifold with filtration
Bak, A; Muranov, Yu V
2008-06-30
A simple homotopy equivalence f:M{sup n}{yields}X{sup n} of manifolds splits along a submanifold Y subset of X if it is homotopic to a map that is a simple homotopy equivalence on the transversal preimage of the submanifold and on the complement of this preimage. The problem of splitting along a submanifold with filtration is a natural generalization of this problem. In this paper we define groups LSF{sub *} of obstructions to splitting along a submanifold with filtration and describe their properties. We apply the results obtained to the problem of the realization of surgery and splitting obstructions by maps of closed manifolds and consider several examples. Bibliography: 36 titles.
Hydrogen atom as a four-dimensional oscillator
Chen, A.C.
1980-08-01
A coordinate transformation which exhibits the rotational invariance of the hydrogen atom in four-dimensional Hilbert space is introduced. The coordinates are shown to be directly related to the spherical polar and parabolic coordinates in position space. With the use of the transformation, the Schroedinger equation for the hydrogen atom left-multiplied by 4r is transformed into one for a four-dimensional harmonic oscillator. Solutions are obtained and related to the hydrogenic wave functions. Group-theoretical implications of the transformation and its application to the hydrogen Stark problem are briefly discussed.
Vector particles tunneling from four-dimensional Schwarzschild black holes
NASA Astrophysics Data System (ADS)
Chen, Ge-Rui; Zhou, Shiwei; Huang, Yong-Chang
2015-05-01
Vector particles' Hawking radiation from a four-dimensional Schwarzschild black hole is investigated. By applying the WKB approximation and the Hamilton-Jacobi ansatz to the Proca equation, we obtain the tunneling spectrum of vector particles and the expected Hawking temperature.
Common time in a four-dimensional symmetry framework
NASA Technical Reports Server (NTRS)
Hsu, J. P.; Sherry, T. N.
1980-01-01
Following the ideas of Poincare, Reichenbach, and Grunbaum concerning the convention of setting up clock systems, clock systems and light propagation are analyzed within the framework of four-dimensional symmetry. It is possible to construct a new four-dimensional symmetry framework incorporating common time: observers in different inertial frames of reference use one and the same clock system, which is located in any one of the frames. Consequently, simultaneity has a meaning independent of position and independent of frame of reference. A further consequence is that the two-way speeds of light alone are isotropic in any frame. By the choice of clock system there will be one frame in which the one-way speed of light is isotropic. This frame can be arbitrarily chosen. The difference between one-way speeds and two-way speeds of light signals is considered in detail.
Finding four dimensional symplectic maps with reduced chaos: Preliminary results
Weishi Wan; Cary, J.R.; Shasharina, S.G.
1998-06-01
A method for finding integrable four-dimensional symplectic maps is outlined. The method relies on solving for parameter values at which the linear stability factors of the fixed points of the map have the values corresponding to integrability. This method is applied to accelerator lattices in order to increase dynamic aperture. Results show a increase of the dynamic aperture after correction, which implies the validity of the method.
Platonic solids generate their four-dimensional analogues.
Dechant, Pierre Philippe
2013-11-01
This paper shows how regular convex 4-polytopes - the analogues of the Platonic solids in four dimensions - can be constructed from three-dimensional considerations concerning the Platonic solids alone. Via the Cartan-Dieudonné theorem, the reflective symmetries of the Platonic solids generate rotations. In a Clifford algebra framework, the space of spinors generating such three-dimensional rotations has a natural four-dimensional Euclidean structure. The spinors arising from the Platonic solids can thus in turn be interpreted as vertices in four-dimensional space, giving a simple construction of the four-dimensional polytopes 16-cell, 24-cell, the F4 root system and the 600-cell. In particular, these polytopes have `mysterious' symmetries, that are almost trivial when seen from the three-dimensional spinorial point of view. In fact, all these induced polytopes are also known to be root systems and thus generate rank-4 Coxeter groups, which can be shown to be a general property of the spinor construction. These considerations thus also apply to other root systems such as A(1)\\oplus I(2)(n) which induces I(2)(n)\\oplus I(2)(n), explaining the existence of the grand antiprism and the snub 24-cell, as well as their symmetries. These results are discussed in the wider mathematical context of Arnold's trinities and the McKay correspondence. These results are thus a novel link between the geometries of three and four dimensions, with interesting potential applications on both sides of the correspondence, to real three-dimensional systems with polyhedral symmetries such as (quasi)crystals and viruses, as well as four-dimensional geometries arising for instance in Grand Unified Theories and string and M-theory. PMID:24132220
Five Dimensional Minimal Supergravities and Four Dimensional Complex Geometries
Grover, Jai; Gutowski, Jan B.; Herdeiro, Carlos A. R.; Sabra, Wafic
2009-05-01
We discuss the relation between solutions admitting Killing spinors of minimal supergravities in five dimensions and four dimensional complex geometries. In the ungauged case (vanishing cosmological constant {lambda} 0) the solutions are determined in terms of a hyper-Kaehler base space; in the gauged case ({lambda}<0) the complex geometry is Kaehler; in the de Sitter case ({lambda}>0) the complex geometry is hyper-Kaehler with torsion (HKT). In the latter case some details of the derivation are given. The method for constructing explicit solutions is discussed in each case.
Four-dimensional characterization of a sheet-forming web
Sari-Sarraf, Hamed; Goddard, James S.
2003-04-22
A method and apparatus are provided by which a sheet-forming web may be characterized in four dimensions. Light images of the web are recorded at a point adjacent the initial stage of the web, for example, near the headbox in a paperforming operation. The images are digitized, and the resulting data is processed by novel algorithms to provide a four-dimensional measurement of the web. The measurements include two-dimensional spatial information, the intensity profile of the web, and the depth profile of the web. These measurements can be used to characterize the web, predict its properties and monitor production events, and to analyze and quantify headbox flow dynamics.
Four-Dimensional Global Reference-Atmosphere Model
NASA Technical Reports Server (NTRS)
Johnson, Dale; Blocker, Rhonda S.
1988-01-01
Four-Dimensional Global Reference Atmosphere Model (GRAM) computer program developed from empirical atmospheric model generating values for pressure, density, temperature, and winds, from ground to orbital altitudes. Is amalgamation of two empirical atmospheric models for low and high atmosphere with newly-developed latitude-and longitude-dependent model for middle atmosphere. UNIVAC version written in UNIVAC FORTRAN. DEC VAX version of GRAM written in FORTRAN 77. Applications include simulation of reentry trajectories of external tanks, studies of global circulation and diffusion and generation of plots or data for comparison.
Semiclassical States Associated with Isotropic Submanifolds of Phase Space
NASA Astrophysics Data System (ADS)
Guillemin, V.; Uribe, A.; Wang, Z.
2016-05-01
We define classes of quantum states associated with isotropic submanifolds of cotangent bundles. The classes are stable under the action of semiclassical pseudo-differential operators and covariant under the action of semiclassical Fourier integral operators. We develop a symbol calculus for them; the symbols are symplectic spinors. We outline various applications.
Four-dimensional maps of the human somatosensory system
Avanzini, Pietro; Abdollahi, Rouhollah O.; Sartori, Ivana; Caruana, Fausto; Pelliccia, Veronica; Casaceli, Giuseppe; Mai, Roberto; Lo Russo, Giorgio; Rizzolatti, Giacomo; Orban, Guy A.
2016-01-01
A fine-grained description of the spatiotemporal dynamics of human brain activity is a major goal of neuroscientific research. Limitations in spatial and temporal resolution of available noninvasive recording and imaging techniques have hindered so far the acquisition of precise, comprehensive four-dimensional maps of human neural activity. The present study combines anatomical and functional data from intracerebral recordings of nearly 100 patients, to generate highly resolved four-dimensional maps of human cortical processing of nonpainful somatosensory stimuli. These maps indicate that the human somatosensory system devoted to the hand encompasses a widespread network covering more than 10% of the cortical surface of both hemispheres. This network includes phasic components, centered on primary somatosensory cortex and neighboring motor, premotor, and inferior parietal regions, and tonic components, centered on opercular and insular areas, and involving human parietal rostroventral area and ventral medial-superior-temporal area. The technique described opens new avenues for investigating the neural basis of all levels of cortical processing in humans. PMID:26976579
Human four-dimensional spatial intuition in virtual reality.
Ambinder, Michael S; Wang, Ranxiao Frances; Crowell, James A; Francis, George K; Brinkmann, Peter
2009-10-01
It is a long-lasting question whether human beings, who evolved in a physical world of three dimensions, are capable of overcoming this fundamental limitation to develop an intuitive understanding of four-dimensional space. Techniques of analogy and graphical illustration have been developed with some subjective reports of success. However, there has been no objective evaluation of such achievements. Here, we show evidence that people with basic geometric knowledge can learn to make spatial judgments on the length of, and angle between, line segments embedded in four-dimensional space viewed in virtual reality with minimal exposure to the task and no feedback to their responses. Their judgments incorporated information from both the three-dimensional (3-D) projection and the fourth dimension, and the underlying representations were not algebraic in nature but based on visual imagery, although primitive and short lived. These results suggest that human spatial representations are not completely constrained by our evolution and development in a 3-D world. Illustration of the stimuli and experimental procedure (as video clips) and the instruction to participants (as a PDF file) may be downloaded from http://pbr.psychonomic-journals.org/content/supplemental. PMID:19815783
Four-dimensional maps of the human somatosensory system.
Avanzini, Pietro; Abdollahi, Rouhollah O; Sartori, Ivana; Caruana, Fausto; Pelliccia, Veronica; Casaceli, Giuseppe; Mai, Roberto; Lo Russo, Giorgio; Rizzolatti, Giacomo; Orban, Guy A
2016-03-29
A fine-grained description of the spatiotemporal dynamics of human brain activity is a major goal of neuroscientific research. Limitations in spatial and temporal resolution of available noninvasive recording and imaging techniques have hindered so far the acquisition of precise, comprehensive four-dimensional maps of human neural activity. The present study combines anatomical and functional data from intracerebral recordings of nearly 100 patients, to generate highly resolved four-dimensional maps of human cortical processing of nonpainful somatosensory stimuli. These maps indicate that the human somatosensory system devoted to the hand encompasses a widespread network covering more than 10% of the cortical surface of both hemispheres. This network includes phasic components, centered on primary somatosensory cortex and neighboring motor, premotor, and inferior parietal regions, and tonic components, centered on opercular and insular areas, and involving human parietal rostroventral area and ventral medial-superior-temporal area. The technique described opens new avenues for investigating the neural basis of all levels of cortical processing in humans. PMID:26976579
The Cosmological Constant in Four-Dimensional String Theory
NASA Astrophysics Data System (ADS)
Dienes, Keith Roger
1991-02-01
We propose several new theoretical mechanisms by which four-dimensional string models can have vanishing one-loop cosmological constants in the absence of spacetime supersymmetry. One line of approach involves Atkin-Lehner symmetry: this symmetry was recently proposed as precisely such a mechanism, but it has been shown that for models formulated in four-dimensional spacetime this symmetry cannot be realized. We therefore investigate various means of retaining the general Atkin-Lehner idea without having strict Atkin-Lehner symmetry. We first explicitly construct non-Atkin-Lehner symmetric partition functions which not only lead to vanishing cosmological constants but which also avoid a recent proof that Atkin-Lehner symmetric partition functions cannot arise from physically viable string models in greater than two dimensions. We then develop a systematic generalization of Atkin-Lehner symmetry, basing our considerations on the use of non-hermitian operators as well as on a general class of possible congruence subgroups of the full modular group. We find that whereas in many instances our resulting symmetries reduce to either strict Atkin-Lehner symmetry or symmetries closely related to it, in other cases we obtain symmetries of a fundamentally new character. Our results therefore suggest possible new avenues for retaining the general Atkin-Lehner "selection rule" approach for obtaining a vanishing one-loop cosmological constant. We then present a series of new one-loop non-supersymmetric four-dimensional heterotic string partition functions which we conjecture to lead as well to vanishing one-loop cosmological constants. These partition functions have neither the strict nor our generalized Atkin-Lehner symmetries. We demonstrate that our partition functions satisfy various requirements imposed by the physical consistency of possible corresponding string models, and discuss the results of an automated search for such models. Although we find no such models directly
Lung deformation estimation and four-dimensional CT lung reconstruction.
Xu, Sheng; Taylor, Russell H; Fichtinger, Gabor; Cleary, Kevin
2005-01-01
Four-dimensional (4D) computed tomography (CT) image acquisition is a useful technique in radiation treatment planning and interventional radiology in that it can account for respiratory motion of lungs. Current 4D lung reconstruction techniques have limitations in either spatial or temporal resolution. In addition, most of these techniques rely on auxiliary surrogates to relate the time of CT scan to the patient's respiratory phase. In this paper, we propose a novel 4D CT lung reconstruction and deformation estimation algorithm. Our algorithm is purely image based. The algorithm can reconstruct high quality 4D images even if the original images are acquired under irregular respiratory motion. The algorithm is validated using synthetic 4D lung data. Experimental results from a swine study data are also presented. PMID:16685974
Wilson loops in four-dimensional quantum gravity
NASA Astrophysics Data System (ADS)
Modanese, Giovanni
1994-06-01
A Wilson loop is defined, in four-dimensional pure Einstein gravity, as the trace of the holonomy of the Christoffel connection or of the spin connection, and its invariance under the symmetry transformations of the action is shown (diffeomorphisms and local Lorentz transformations). We then compute the loop perturbatively, both on a flat background and in the presence of an external source; we also allow some modifications in the form of the action, and test the action of ``stabilized'' gravity. A geometrical analysis of the results in terms of the gauge group of the Euclidean theory, SO(4), leads us to the conclusion that the corresponding statistical system does not develop any configuration with localized curvature at low temperature. This ``nonlocal'' behavior of the quantized gravitational field strongly contrasts with that of usual gauge fields. Our results also provide an explanation for the absence of any invariant correlation of the curvature in the same approximation.
Spin(7)-Instantons, Cayley Submanifolds and Fueter Sections
NASA Astrophysics Data System (ADS)
Walpuski, Thomas
2016-07-01
We prove an existence theorem for Spin(7)-instantons, which are highly concentrated near a Cayley submanifold; thus giving a partial converse to Tian's foundational compactness theorem (Ann Math (2) 151(1):193-268, 2000). As an application, we show how to construct Spin(7)-instantons on Spin(7)-manifolds with suitable local K3 Cayley fibrations. This recovers an example constructed by Lewis (Spin(7) instantons, Ph.D. Thesis, 1998).
On Sasakian hypersurfaces in 6-dimensional Hermitian submanifolds of the Cayley algebra
Banaru, M B
2003-08-31
A criterion for the minimality of a Sasakian hypersurface in a 6-dimensional Hermitian submanifold of the octave algebra is found. It is proved that the type number of a Sasakian hypersurface in a 6-dimensional Hermitian submanifold of the octave algebra is four or five. It is also proved that a Sasakian hypersurface in a 6-dimensional Hermitian submanifold of the Cayley algebra is minimal if and only if it is ruled.
Reversible Hopf bifurcation in four-dimensional maps
NASA Astrophysics Data System (ADS)
Roy, Tarun K.; Lahiri, Avijit
1991-10-01
Following a recent work [Sevryuk and Lahiri, Phys. Lett. A 154, 104 (1991)], we study the bifurcation of four-dimensional reversible maps in which the eigenvalues of the Jacobian of the map at a symmetric fixed point move off the unit circle along a pair of conjugate rays as some parameter ɛ crosses a threshold value. We construct a perturbation scheme to show that, depending on a control parameter γ, the bifurcation can be either ``normal'' or ``inverted'' in nature. In the former case, two one-parameter families of elliptic invariant curves passing arbitrarily close to the fixed point (which coexist with Kolmogorov-Arnold-Moser tori) merge together and move away from the fixed point. In the latter case, the families of elliptic invariant curves meet a family of hyperbolic invariant curves. As ɛ is varied, all these invariant curves shrink to the fixed point and are annihilated. The problem of determining whether an invariant curve is elliptic or hyperbolic is related to a tight-binding model on a linear quasiperiodic chain familiar in solid-state theory. Numerical evidence confirming these results is presented. A few areas for further study are indicated.
Motion artifact detection in four-dimensional computed tomography images
NASA Astrophysics Data System (ADS)
Bouilhol, G.; Ayadi, M.; Pinho, R.; Rit, S.; Sarrut, D.
2014-03-01
Motion artifacts appear in four-dimensional computed tomography (4DCT) images because of suboptimal acquisition parameters or patient breathing irregularities. Frequency of motion artifacts is high and they may introduce errors in radiation therapy treatment planning. Motion artifact detection can be useful for image quality assessment and 4D reconstruction improvement but manual detection in many images is a tedious process. We propose a novel method to evaluate the quality of 4DCT images by automatic detection of motion artifacts. The method was used to evaluate the impact of the optimization of acquisition parameters on image quality at our institute. 4DCT images of 114 lung cancer patients were analyzed. Acquisitions were performed with a rotation period of 0.5 seconds and a pitch of 0.1 (74 patients) or 0.081 (40 patients). A sensitivity of 0.70 and a specificity of 0.97 were observed. End-exhale phases were less prone to motion artifacts. In phases where motion speed is high, the number of detected artifacts was systematically reduced with a pitch of 0.081 instead of 0.1 and the mean reduction was 0.79. The increase of the number of patients with no artifact detected was statistically significant for the 10%, 70% and 80% respiratory phases, indicating a substantial image quality improvement.
An economical approach to four-dimensional variational data assimilation
NASA Astrophysics Data System (ADS)
Wang, Bin; Liu, Juanjuan; Wang, Shudong; Cheng, Wei; Juan, Liu; Liu, Chengsi; Xiao, Qingnong; Kuo, Ying-Hwa
2010-07-01
Four-dimensional variational data assimilation (4DVar) is one of the most promising methods to provide optimal analysis for numerical weather prediction (NWP). Five national NWP centers in the world have successfully applied 4DVar methods in their global NWPs, thanks to the increment method and adjoint technique. However, the application of 4DVar is still limited by the computer resources available at many NWP centers and research institutes. It is essential, therefore, to further reduce the computational cost of 4DVar. Here, an economical approach to implement 4DVar is proposed, using the technique of dimensionreduced projection (DRP), which is called "DRP-4DVar." The proposed approach is based on dimension reduction using an ensemble of historical samples to define a subspace. It directly obtains an optimal solution in the reduced space by fitting observations with historical time series generated by the model to form consistent forecast states, and therefore does not require implementation of the adjoint of tangent linear approximation. To evaluate the performance of the DRP-4DVar on assimilating different types of mesoscale observations, some observing system simulation experiments are conducted using MM5 and a comparison is made between adjoint-based 4DVar and DRP-4DVar using a 6-hour assimilation window.
Four dimensional deformable image registration using trajectory modeling
Castillo, Edward; Castillo, Richard; Martinez, Josue; Shenoy, Maithili; Guerrero, Thomas
2013-01-01
A four-dimensional deformable image registration (4D DIR) algorithm, referred to as 4D local trajectory modeling (4DLTM), is presented and applied to thoracic 4D computed tomography (4DCT) image sets. The theoretical framework on which this algorithm is built exploits the incremental continuity present in 4DCT component images to calculate a dense set of parameterized voxel trajectories through space as functions of time. The spatial accuracy of the 4DLTM algorithm is compared with an alternative registration approach in which component phase to phase (CPP) DIR is utilized to determine the full displacement between maximum inhale and exhale images. A publically available DIR reference database (http://www.dir-lab.com) is utilized for the spatial accuracy assessment. The database consists of ten 4DCT image sets and corresponding manually identified landmark points between the maximum phases. A subset of points are propagated through the expiratory 4DCT component images. Cubic polynomials were found to provide sufficient flexibility and spatial accuracy for describing the point trajectories through the expiratory phases. The resulting average spatial error between the maximum phases was 1.25 mm for the 4DLTM and 1.44 mm for the CPP. The 4DLTM method captures the long-range motion between 4DCT extremes with high spatial accuracy. PMID:20009196
Dynamic ventilation imaging from four-dimensional computed tomography
NASA Astrophysics Data System (ADS)
Guerrero, Thomas; Sanders, Kevin; Castillo, Edward; Zhang, Yin; Bidaut, Luc; Pan, Tinsu; Komaki, Ritsuko
2006-02-01
A novel method for dynamic ventilation imaging of the full respiratory cycle from four-dimensional computed tomography (4D CT) acquired without added contrast is presented. Three cases with 4D CT images obtained with respiratory gated acquisition for radiotherapy treatment planning were selected. Each of the 4D CT data sets was acquired during resting tidal breathing. A deformable image registration algorithm mapped each (voxel) corresponding tissue element across the 4D CT data set. From local average CT values, the change in fraction of air per voxel (i.e. local ventilation) was calculated. A 4D ventilation image set was calculated using pairs formed with the maximum expiration image volume, first the exhalation then the inhalation phases representing a complete breath cycle. A preliminary validation using manually determined lung volumes was performed. The calculated total ventilation was compared to the change in contoured lung volumes between the CT pairs (measured volume). A linear regression resulted in a slope of 1.01 and a correlation coefficient of 0.984 for the ventilation images. The spatial distribution of ventilation was found to be case specific and a 30% difference in mass-specific ventilation between the lower and upper lung halves was found. These images may be useful in radiotherapy planning.
Four dimensional lidar imaging of the atmosphere (Invited)
NASA Astrophysics Data System (ADS)
Eloranta, E.
2010-12-01
High resolution four-dimensional depictions of atmospheric structure are needed for many atmospheric investigations. Scanning lidar offers the potential to provide high spatial and temporal resolution four-dimensional imaging of atmospheric structure. This paper will use data acquired with the University of Wisconsin Volume Imaging Lidar (VIL) to illustrate the potential of such measurements, describe the necessary lidar performance requirements , and provide measurement examples. The University of Wisconsin Volume imaging lidar acquired it's first data in the 1987 FIFE experiment and was operated in several deployments until it was mothballed after the 1997-98 Lake-ICE experiment. Although this data is old and the system is now obsolete, the data illustrates the power of the measurement approach and the system characteristics needed to acquire such data. The key challenge in acquiring useful 4-D scan is to provide high spatial resolution along with a scan repeat time short enough to maintain temporal coherence between successive images. This requires a high power transmitter, high pulse repetition rates, large optics, high quantum efficiency, good optical throughput and fast data acquisition. The VIL operated at a wavelength of 1064 nm, emitting an average power of 40 W at a repetition rate of 100 Hz. The receiver utilized 0.5 m diameter telescope with an avalanche photodiode detector that provides a quantum efficiency of ~35%. Operating at the fundamental Nd:YAG wavelength of 1064 rather than the more usual doubled 532 nm wavelength, avoided the loss of power and photon numbers involved in frequency doubling. It also allowed use of the high quantum efficiency of the avalanche photodiode in place of the the lower efficiency photomultiplier. Signal-to-noise calculations show that the combination of higher photon numbers and greater quantum efficiency more than maked up for the large dark current noise of the APD-amplifier combination. The high power and sensitivity
Four-dimensional flow magnetic resonance imaging in cirrhosis
Stankovic, Zoran
2016-01-01
Since its introduction in the 1970’s, magnetic resonance imaging (MRI) has become a standard imaging modality. With its broad and standardized application, it is firmly established in the clinical routine and an essential element in cardiovascular and abdominal imaging. In addition to sonography and computer tomography, MRI is a valuable tool for diagnosing cardiovascular and abdominal diseases, for determining disease severity, and for assessing therapeutic success. MRI techniques have improved over the last few decades, revealing not just morphologic information, but functional information about perfusion, diffusion and hemodynamics as well. Four-dimensional (4D) flow MRI, a time-resolved phase contrast-MRI with three-dimensional (3D) anatomic coverage and velocity encoding along all three flow directions has been used to comprehensively assess complex cardiovascular hemodynamics in multiple regions of the body. The technique enables visualization of 3D blood flow patterns and retrospective quantification of blood flow parameters in a region of interest. Over the last few years, 4D flow MRI has been increasingly performed in the abdominal region. By applying different acceleration techniques, taking 4D flow MRI measurements has dropped to a reasonable scanning time of 8 to 12 min. These new developments have encouraged a growing number of patient studies in the literature validating the technique’s potential for enhanced evaluation of blood flow parameters within the liver’s complex vascular system. The purpose of this review article is to broaden our understanding of 4D flow MRI for the assessment of liver hemodynamics by providing insights into acquisition, data analysis, visualization and quantification. Furthermore, in this article we highlight its development, focussing on the clinical application of the technique. PMID:26755862
Weak constraints in four-dimensional variational data assimilation
NASA Astrophysics Data System (ADS)
Watkinson, L. R.; Lawless, A. S.; Nichols, N. K.; Roulstone, I.
2009-04-01
The formulation of four-dimensional variational data assimilation (4D-Var) allows the incorporation of constraints into the cost function which need only be weakly satisfied. A common constraint imposed in this way is the requirement that the analysis be close to a previous short-range forecast or background field. In many environmental systems certain quantities are known to be conserved exactly or to be approximately conserved, but this knowledge is often not used directly within the assimilation system. In this study we investigate the benefit obtained from imposing these conservation properties as weak constraints in the 4D-Var problem. To study this problem we make use of Kepler's two- and three-body systems for planetary orbits. These are Hamiltonian systems and, as such, are known to exactly conserve the Hamiltonian, which in this case is equal to the total energy. A 4D-Var scheme is designed in which two different constraints on the a priori information can be applied. The first is a standard background constraint, which controls the distance to a background state expressed in terms of the model variables. The second constraint uses the Hamiltonian calculated from the background state as a weak constraint on the Hamiltonian of the analysis. The formulation of this second constraint is shown to change the nature of the gradient equation, with components in different directions to the gradient obtained from the background constraint. Using identical twin experiments we illustrate how the two constraints influence the final analysis in different ways. We show how by constraining the Hamiltonian quantity together with the background state it is possible to obtain a more accurate analysis than when using a background state alone. This is found to be true even if the numerical model respects the conservation properties of the system.
Verification of four-dimensional photon dose calculations.
Vinogradskiy, Yevgeniy Y; Balter, Peter; Followill, David S; Alvarez, Paola E; White, R Allen; Starkschall, George
2009-08-01
Recent work in the area of thoracic treatment planning has been focused on trying to explicitly incorporate patient-specific organ motion in the calculation of dose. Four-dimensional (4D) dose calculation algorithms have been developed and incorporated in a research version of a commercial treatment planning system (Pinnacle3, Philips Medical Systems, Milpitas, CA). Before these 4D dose calculations can be used clinically, it is necessary to verify their accuracy with measurements. The primary purpose of this study therefore was to evaluate and validate the accuracy of a 4D dose calculation algorithm with phantom measurements. A secondary objective was to determine whether the performance of the 4D dose calculation algorithm varied between different motion patterns and treatment plans. Measurements were made using two phantoms: A rigid moving phantom and a deformable phantom. The rigid moving phantom consisted of an anthropomorphic thoracic phantom that rested on a programmable motion platform. The deformable phantom used the same anthropomorphic thoracic phantom with a deformable insert for one of the lungs. Two motion patterns were investigated for each phantom: A sinusoidal motion pattern and an irregular motion pattern extracted from a patient breathing profile. A single-beam plan, a multiple-beam plan, and an intensity-modulated radiation therapy plan were created. Doses were calculated in the treatment planning system using the 4D dose calculation algorithm. Then each plan was delivered to the phantoms and delivered doses were measured using thermoluminescent dosimeters (TLDs) and film. The measured doses were compared to the 4D-calculated doses using a measured-to-calculated TLD ratio and a gamma analysis. A relevant passing criteria (3% for the TLD and 5% /3 mm for the gamma metric) was applied to determine if the 4D dose calculations were accurate to within clinical standards. All the TLD measurements in both phantoms satisfied the passing criteria
Energy aware path planning in complex four dimensional environments
NASA Astrophysics Data System (ADS)
Chakrabarty, Anjan
This dissertation addresses the problem of energy-aware path planning for small autonomous vehicles. While small autonomous vehicles can perform missions that are too risky (or infeasible) for larger vehicles, the missions are limited by the amount of energy that can be carried on board the vehicle. Path planning techniques that either minimize energy consumption or exploit energy available in the environment can thus increase range and endurance. Path planning is complicated by significant spatial (and potentially temporal) variations in the environment. While the main focus is on autonomous aircraft, this research also addresses autonomous ground vehicles. Range and endurance of small unmanned aerial vehicles (UAVs) can be greatly improved by utilizing energy from the atmosphere. Wind can be exploited to minimize energy consumption of a small UAV. But wind, like any other atmospheric component , is a space and time varying phenomenon. To effectively use wind for long range missions, both exploration and exploitation of wind is critical. This research presents a kinematics based tree algorithm which efficiently handles the four dimensional (three spatial and time) path planning problem. The Kinematic Tree algorithm provides a sequence of waypoints, airspeeds, heading and bank angle commands for each segment of the path. The planner is shown to be resolution complete and computationally efficient. Global optimality of the cost function cannot be claimed, as energy is gained from the atmosphere, making the cost function inadmissible. However the Kinematic Tree is shown to be optimal up to resolution if the cost function is admissible. Simulation results show the efficacy of this planning method for a glider in complex real wind data. Simulation results verify that the planner is able to extract energy from the atmosphere enabling long range missions. The Kinematic Tree planning framework, developed to minimize energy consumption of UAVs, is applied for path planning
Biharmonic Submanifolds with Parallel Mean Curvature Vector in Pseudo-Euclidean Spaces
NASA Astrophysics Data System (ADS)
Fu, Yu
2013-12-01
In this paper, we investigate biharmonic submanifolds in pseudo-Euclidean spaces with arbitrary index and dimension. We give a complete classification of biharmonic spacelike submanifolds with parallel mean curvature vector in pseudo-Euclidean spaces. We also determine all biharmonic Lorentzian surfaces with parallel mean curvature vector field in pseudo-Euclidean spaces.
Geometric analysis of the Lorentzian distance function on trapped submanifolds
NASA Astrophysics Data System (ADS)
Alías, Luis J.; Pacelli Bessa, G.; de Lira, Jorge H. S.
2016-06-01
We use geometric analysis of the Lorentzian distance on an n-dimensional spacetime \\bar{M} to derive some non-existence results and some sharp mean curvature estimates for trapped submanifolds contained in the chronological future of either a point p\\in \\bar{M} or of a space-like achronal hypersurface {{Σ }}\\subset \\bar{M}. Our results are given as an application of the corresponding Hessian comparison results for the Lorentzian distance function and the so-called weak maximum principle for the Laplacian operator.
Invariant submanifold for series arrays of Josephson junctions
NASA Astrophysics Data System (ADS)
Marvel, Seth A.; Strogatz, Steven H.
2009-03-01
We study the nonlinear dynamics of series arrays of Josephson junctions in the large-N limit, where N is the number of junctions in the array. The junctions are assumed to be identical, overdamped, driven by a constant bias current, and globally coupled through a common load. Previous simulations of such arrays revealed that their dynamics are remarkably simple, hinting at the presence of some hidden symmetry or other structure. These observations were later explained by the discovery of N -3 constants of motion, the choice of which confines the resulting flow in phase space to a low-dimensional invariant manifold. Here we show that the dimensionality can be reduced further by restricting attention to a special family of states recently identified by Ott and Antonsen. In geometric terms, the Ott-Antonsen ansatz corresponds to an invariant submanifold of dimension one less than that found earlier. We derive and analyze the flow on this submanifold for two special cases: an array with purely resistive loading and another with resistive-inductive-capacitive loading. Our results recover (and in some instances improve) earlier findings based on linearization arguments.
Geometry of the submanifolds of SEXn. I. The C-nonholonomic frame of reference
NASA Astrophysics Data System (ADS)
Chung, Kyung Tae; So, Keum Sook; Lee, Jong Woo
1989-08-01
A connection which is both Einstein and semisymmetric is called an SE connection. A generalized n-dimensional Riemannian manifold on which the differential geometric structure is imposed by g λμ through an SE connection is called an n-dimensional SE manifold and denoted by SEXn. This paper is the introductory part of a systematic study of the submanifolds of SEXn. It introduces a new concept of the C-nonholonomic frame of references in SEXn at points of its submanifold and deals with its consequences. The second part will deal with the generalized fundamental equations on an SE hypersubmanifold of SEXn. The third part will be devoted to the theory of parallelism in SEXn and in its submanifold. Finally, the last part will study the curvature theory in a submanifold of SEXn.
Mirzoyan, V A
2008-04-30
A full local classification and a geometric description of normally flat minimal semi-Einstein submanifolds of Euclidean spaces having multiple principal curvature vectors and an integrable conullity distribution are presented. Bibliography: 30 titles.
Dirac method and symplectic submanifolds in the cotangent bundle of a factorizable Lie group
NASA Astrophysics Data System (ADS)
Capriotti, S.; Montani, H.
2011-07-01
We study some symplectic submanifolds in the cotangent bundle of a factorizable Lie group defined by second class constraints. By applying the Dirac method, we study many issues of these spaces as fundamental Dirac brackets, symmetries, and collective dynamics. As the main application, we study integrable systems on these submanifolds as inherited from a system on the whole cotangent bundle, meeting in a natural way with the Adler-Kostant-Symes theory of integrability.
Improving the Horizontal Transport in the Lower Troposphere with Four Dimensional Data Assimilation
The physical processes involved in air quality modeling are governed by dynamically-generated meteorological model fields. This research focuses on reducing the uncertainty in the horizontal transport in the lower troposphere by improving the four dimensional data assimilation (F...
Questions on universal constants and four-dimensional symmetry from a broad viewpoint. I
NASA Technical Reports Server (NTRS)
Hsu, J. P.
1983-01-01
It is demonstrated that there is a flexibility in clock synchronizations and that four-dimensional symmetry framework can be viewed broadly. The true universality of basic constants is discussed, considering a class of measurement processes based on the velocity = distance/time interval, which always yields some number when used by an observer. The four-dimensional symmetry framework based on common time for all observers is formulated, and related processes of measuring light speed are discussed. Invariant 'action functions' for physical laws in the new four-dimensional symmetry framework with the common time are established to discuss universal constants. Truly universal constants are demonstrated, and it is shown that physics in this new framework and in special relativity are equivalent as far as one-particle systems and the S-matrix in field theories are concerned.
NASA Astrophysics Data System (ADS)
Pahlavani, M. R.; Mirfathi, S. M.
2016-04-01
Four-dimensional Langevin equations have been suggested for the dynamical simulation of neutron-induced fission at low and medium excitation energies. The mass distribution of the fission fragments, the neutron multiplicity, and the fission cross section for the thermal and fast neutron-induced fission of 233U, 235U, and 238U is studied by considering energy dissipation of the compound nucleus through the fission using four-dimensional Langevin equations combined with a Monte Carlo simulation approach. The calculated results using this approach indicate reasonable agreement with available experimental data.
Abedi-Fardad, J.; Rezaei-Aghdam, A.; Haghighatdoost, Gh.
2014-05-15
We construct integrable and superintegrable Hamiltonian systems using the realizations of four dimensional real Lie algebras as a symmetry of the system with the phase space R{sup 4} and R{sup 6}. Furthermore, we construct some integrable and superintegrable Hamiltonian systems for which the symmetry Lie group is also the phase space of the system.
Conceptualising Quality of School Life from Pupils' Perspectives: A Four-Dimensional Model
ERIC Educational Resources Information Center
Tangen, Reidun
2009-01-01
This paper presents a four-dimensional, dynamic model of pupils' subjective quality of school life. The model is based on the author's and colleagues' studies of experiences and perspectives of pupils in regular schools who have been assessed as having "special educational needs". The conceptualisation of quality of school life proposed here is…
Adding Four- Dimensional Data Assimilation (a.k.a. grid nudging) to MPAS
Adding four-dimensional data assimilation (a.k.a. grid nudging) to MPAS.The U.S. Environmental Protection Agency is investigating the use of MPAS as the meteorological driver for its next-generation air quality model. To function as such, MPAS needs to operate in a diagnostic mod...
Quasinormal modes and greybody factors of a four-dimensional Lifshitz black hole with z=0
NASA Astrophysics Data System (ADS)
Catalán, Marcela; Cisternas, Eduardo; González, P. A.; Vásquez, Yerko
2016-06-01
We study scalar perturbations for a four-dimensional asymptotically Lifshitz black hole in conformal gravity with dynamical exponent z=0, and spherical topology for the transverse section, and we find analytically and numerically the quasinormal modes for scalar fields for some special cases. Then, we study the stability of these black holes under scalar field perturbations and greybody factors.
NASA Astrophysics Data System (ADS)
Galloway, Gregory J.; Senovilla, José M. M.
2010-08-01
Standard singularity theorems are proven in Lorentzian manifolds of arbitrary dimension n if they contain closed trapped submanifolds of arbitrary co-dimension. By using the mean curvature vector to characterize trapped submanifolds, a unification of the several possibilities for the boundary conditions in the traditional theorems and their generalization to an arbitrary co-dimension is achieved. The classical convergence conditions must be replaced by a condition on sectional curvatures, or tidal forces, which reduces to the former in the cases of the co-dimension 1, 2 or n.
Four-dimensional optical coherence tomography imaging of total liquid ventilated rats
NASA Astrophysics Data System (ADS)
Kirsten, Lars; Schnabel, Christian; Gaertner, Maria; Koch, Edmund
2013-06-01
Optical coherence tomography (OCT) can be utilized for the spatially and temporally resolved visualization of alveolar tissue and its dynamics in rodent models, which allows the investigation of lung dynamics on the microscopic scale of single alveoli. The findings could provide experimental input data for numerical simulations of lung tissue mechanics and could support the development of protective ventilation strategies. Real four-dimensional OCT imaging permits the acquisition of several OCT stacks within one single ventilation cycle. Thus, the entire four-dimensional information is directly obtained. Compared to conventional virtual four-dimensional OCT imaging, where the image acquisition is extended over many ventilation cycles and is triggered on pressure levels, real four-dimensional OCT is less vulnerable against motion artifacts and non-reproducible movement of the lung tissue over subsequent ventilation cycles, which widely reduces image artifacts. However, OCT imaging of alveolar tissue is affected by refraction and total internal reflection at air-tissue interfaces. Thus, only the first alveolar layer beneath the pleura is visible. To circumvent this effect, total liquid ventilation can be carried out to match the refractive indices of lung tissue and the breathing medium, which improves the visibility of the alveolar structure, the image quality and the penetration depth and provides the real structure of the alveolar tissue. In this study, a combination of four-dimensional OCT imaging with total liquid ventilation allowed the visualization of the alveolar structure in rat lung tissue benefiting from the improved depth range beneath the pleura and from the high spatial and temporal resolution.
Minimality on biharmonic space-like submanifolds in pseudo-Riemannian space forms
NASA Astrophysics Data System (ADS)
Liu, Jiancheng; Du, Li; Zhang, Juan
2015-06-01
In this paper, we investigate the minimality or the constraint of the mean curvature of three kinds of biharmonic space-like submanifolds in pseudo-Riemannian space forms: (1) pseudo-umbilical ones; (2) the ones with parallel mean curvature vector; (3) with constant mean curvature.
Lightlike hypersurfaces along spacelike submanifolds in anti-de Sitter space
Izumiya, Shyuichi
2015-11-15
Anti-de Sitter space is the Lorentzian space form with negative curvature. In this paper, we consider lightlike hypersurfaces along spacelike submanifolds in anti-de Sitter space with general codimension. In particular, we investigate the singularities of lightlike hypersurfaces as an application of the theory of Legendrian singularities.
Legendre submanifolds in contact manifolds as attractors and geometric nonequilibrium thermodynamics
Goto, Shin-itiro
2015-07-15
It has been proposed that equilibrium thermodynamics is described on Legendre submanifolds in contact geometry. It is shown in this paper that Legendre submanifolds embedded in a contact manifold can be expressed as attractors in phase space for a certain class of contact Hamiltonian vector fields. By giving a physical interpretation that points outside the Legendre submanifold can represent nonequilibrium states of thermodynamic variables, in addition to that points of a given Legendre submanifold can represent equilibrium states of the variables, this class of contact Hamiltonian vector fields is physically interpreted as a class of relaxation processes, in which thermodynamic variables achieve an equilibrium state from a nonequilibrium state through a time evolution, a typical nonequilibrium phenomenon. Geometric properties of such vector fields on contact manifolds are characterized after introducing a metric tensor field on a contact manifold. It is also shown that a contact manifold and a strictly convex function induce a lower dimensional dually flat space used in information geometry where a geometrization of equilibrium statistical mechanics is constructed. Legendre duality on contact manifolds is explicitly stated throughout.
Legendre submanifolds in contact manifolds as attractors and geometric nonequilibrium thermodynamics
NASA Astrophysics Data System (ADS)
Goto, Shin-itiro
2015-07-01
It has been proposed that equilibrium thermodynamics is described on Legendre submanifolds in contact geometry. It is shown in this paper that Legendre submanifolds embedded in a contact manifold can be expressed as attractors in phase space for a certain class of contact Hamiltonian vector fields. By giving a physical interpretation that points outside the Legendre submanifold can represent nonequilibrium states of thermodynamic variables, in addition to that points of a given Legendre submanifold can represent equilibrium states of the variables, this class of contact Hamiltonian vector fields is physically interpreted as a class of relaxation processes, in which thermodynamic variables achieve an equilibrium state from a nonequilibrium state through a time evolution, a typical nonequilibrium phenomenon. Geometric properties of such vector fields on contact manifolds are characterized after introducing a metric tensor field on a contact manifold. It is also shown that a contact manifold and a strictly convex function induce a lower dimensional dually flat space used in information geometry where a geometrization of equilibrium statistical mechanics is constructed. Legendre duality on contact manifolds is explicitly stated throughout.
Rotating system for four-dimensional transverse rms-emittance measurements
NASA Astrophysics Data System (ADS)
Xiao, C.; Maier, M.; Du, X. N.; Gerhard, P.; Groening, L.; Mickat, S.; Vormann, H.
2016-07-01
Knowledge of the transverse four-dimensional beam rms parameters is essential for applications that involve lattice elements that couple the two transverse degrees of freedom (planes). Of special interest is the elimination of interplane correlations to reduce the projected emittances. A dedicated rotating system for emittance measurements (ROSE) has been proposed, developed, and successfully commissioned to fully determine the four-dimensional beam matrix. This device has been used at the high charge injector (HLI) at GSI in a beam line which is composed of a skew quadrupole triplet, a normal quadrupole doublet, and ROSE. Mathematical algorithms, measurements, and the analysis of errors and the decoupling capability for ion beams of 83Kr 13+ at 1.4 MeV /u are reported in this paper.
Three- and four-dimensional ultrasound in fetal echocardiography: an up-to-date overview.
Adriaanse, B M E; van Vugt, J M G; Haak, M C
2016-09-01
Congenital heart diseases (CHD) are the most commonly overlooked lesions in prenatal screening programs. Real-time two-dimensional ultrasound (2DUS) is the conventionally used tool for fetal echocardiography. Although continuous improvements in the hardware and post-processing software have resulted in a good image quality even in late first trimester, 2DUS still has its limitations. Four-dimensional ultrasound with spatiotemporal image correlation (STIC) is an automated volume acquisition, recording a single three-dimensional (3D) volume throughout a complete cardiac cycle, which results in a four-dimensional (4D) volume. STIC has the potential to increase the detection rate of CHD. The aim of this study is to provide a practical overview of the possibilities and (dis)advantages of STIC. A review of literature and evaluation of the current status and clinical value of 3D/4D ultrasound in prenatal screening and diagnosis of congenital heart disease are presented. PMID:26963426
FAST TRACK COMMUNICATION Single-charge rotating black holes in four-dimensional gauged supergravity
NASA Astrophysics Data System (ADS)
Chow, David D. K.
2011-02-01
We consider four-dimensional U(1)4 gauged supergravity, and obtain asymptotically AdS4, non-extremal, charged, rotating black holes with one non-zero U(1) charge. The thermodynamic quantities are computed. We obtain a generalization that includes a NUT parameter. The general solution has a discrete symmetry involving inversion of the rotation parameter, and has a string frame metric that admits a rank-2 Killing-Stäckel tensor.
SU-E-CAMPUS-T-03: Four-Dimensional Dose Distribution Measurement Using Plastic Scintillator
Hashimoto, M; Kozuka, T; Oguchi, M; Nishio, T; Haga, A; Hanada, T; Kabuki, S
2014-06-15
Purpose: To develop the detector for the four-dimensional dose distribution measurement. Methods: We made the prototype detector for four-dimensional dose distribution measurement using a cylindrical plastic scintillator (5 cm diameter) and a conical reflection grass. The plastic scintillator is used as a phantom. When the plastic scintillator is irradiated, the scintillation light was emitted according to absorbed dose distribution. The conical reflection grass was arranged to surround the plastic scintillator, which project to downstream the projection images of the scintillation light. Then, the projection image was reflected to 45 degree direction by flat reflection grass, and was recorded by camcorder. By reconstructing the three-dimensional dose distribution from the projection image recorded in each frame, we could obtain the four-dimensional dose distribution. First, we tested the characteristic according to the amount of emitted light. Then we compared of the light profile and the dose profile calculated with the radiotherapy treatment planning system. Results: The dose dependency of the amount of light showed linearity. The pixel detecting smaller amount of light had high sensitivity than the pixel detecting larger amount of light. However the difference of the sensitivity could be corrected from the amount of light detected in each pixel. Both of the depth light profile through the conical reflection grass and the depth dose profile showed the same attenuation in the region deeper than peak depth. In lateral direction, the difference of the both profiles was shown at outside field and penumbra region. We consider that the difference is occurred due to the scatter of the scintillation light in the plastic scintillator block. Conclusion: It was possible to obtain the amount of light corresponding to the absorbed dose distribution from the prototype detector. Four-dimensional dose distributions can be reconstructed with high accuracy by the correction of
Kink modes and effective four dimensional fermion and Higgs brane models
George, Damien P.; Volkas, Raymond R.
2007-05-15
In the construction of a classical smoothed out brane world model in five dimensions, one uses a dynamically generated domain wall (a kink) to localize an effective four dimensional theory. At the level of the Euler-Lagrange equations the kink sets up a potential well, a mechanism which has been employed extensively to obtain localized, four dimensional, massless chiral fermions. We present the generalization of this kink trapping mechanism for both scalar and fermionic fields, and retain all degrees of freedom that were present in the higher dimensional theory. We show that a kink background induces a symmetric modified Poeschl-Teller potential well, and give explicit analytic forms for all the bound modes and a restricted set of the continuum modes. We demonstrate that it is possible to confine an effective four dimensional scalar field with a quartic potential of arbitrary shape. This can be used to place the standard model electroweak Higgs field on the brane, and also generate nested kink solutions. We also consider the limits of the parameters in the theory which give thin kinks and localized and delocalized scalar and fermionic fields.
Hoon Jung, Sang; Min Yoon, Sang; Ho Park, Sung; Cho, Byungchul; Won Park, Jae; Jung, Jinhong; Park, Jin-hong; Hoon Kim, Jong; Do Ahn, Seung
2013-01-15
Purpose: In order to evaluate the dosimetric impact of respiratory motion on the dose delivered to the target volume and critical organs during free-breathing radiotherapy, a four-dimensional dose was evaluated using deformable image registration (DIR). Methods: Four-dimensional computed tomography (4DCT) images were acquired for 11 patients who were treated for liver cancer. Internal target volume-based treatment planning and dose calculation (3D dose) were performed using the end-exhalation phase images. The four-dimensional dose (4D dose) was calculated based on DIR of all phase images from 4DCT to the planned image. Dosimetric parameters from the 4D dose, were calculated and compared with those from the 3D dose. Results: There was no significant change of the dosimetric parameters for gross tumor volume (p > 0.05). The increase D{sub mean} and generalized equivalent uniform dose (gEUD) for liver were by 3.1%{+-} 3.3% (p= 0.003) and 2.8%{+-} 3.3% (p= 0.008), respectively, and for duodenum, they were decreased by 15.7%{+-} 11.2% (p= 0.003) and 15.1%{+-} 11.0% (p= 0.003), respectively. The D{sub max} and gEUD for stomach was decreased by 5.3%{+-} 5.8% (p= 0.003) and 9.7%{+-} 8.7% (p= 0.003), respectively. The D{sub max} and gEUD for right kidney was decreased by 11.2%{+-} 16.2% (p= 0.003) and 14.9%{+-} 16.8% (p= 0.005), respectively. For left kidney, D{sub max} and gEUD were decreased by 11.4%{+-} 11.0% (p= 0.003) and 12.8%{+-} 12.1% (p= 0.005), respectively. The NTCP values for duodenum and stomach were decreased by 8.4%{+-} 5.8% (p= 0.003) and 17.2%{+-} 13.7% (p= 0.003), respectively. Conclusions: The four-dimensional dose with a more realistic dose calculation accounting for respiratory motion revealed no significant difference in target coverage and potentially significant change in the physical and biological dosimetric parameters in normal organs during free-breathing treatment.
NASA Technical Reports Server (NTRS)
Ghil, M.
1980-01-01
A unified theoretical approach to both the four-dimensional assimilation of asynoptic data and the initialization problem is attempted. This approach relies on the derivation of certain relationships between geopotential tendencies and tendencies of the horizontal velocity field in primitive-equation models of atmospheric flow. The approach is worked out and analyzed in detail for some simple barotropic models. Certain independent results of numerical experiments for the time-continuous assimilation of real asynoptic meteorological data into a complex, baroclinic weather prediction model are discussed in the context of the present approach. Tentative inferences are drawn for practical assimilation procedures.
Four-dimensional (4D) tracking of high-temperature microparticles
NASA Astrophysics Data System (ADS)
Wang, Zhehui; Liu, Q.; Waganaar, W.; Fontanese, J.; James, D.; Munsat, T.
2016-11-01
High-speed tracking of hot and molten microparticles in motion provides rich information about burning plasmas in magnetic fusion. An exploding-wire apparatus is used to produce moving high-temperature metallic microparticles and to develop four-dimensional (4D) or time-resolved 3D particle tracking techniques. The pinhole camera model and algorithms developed for computer vision are used for scene calibration and 4D reconstructions. 3D positions and velocities are then derived for different microparticles. Velocity resolution approaches 0.1 m/s by using the local constant velocity approximation.
One-way quantum computation with four-dimensional photonic qudits
Joo, Jaewoo; Knight, Peter L.; O'Brien, Jeremy L.; Rudolph, Terry
2007-11-15
We consider the possibility of performing linear optical quantum computations making use of extra photonic degrees of freedom. In particular, we focus on the case where we use photons as quadbits, four-dimensional photonic qudits. The basic 2-quadbit cluster state is a hyperentangled state across polarization and two spatial mode degrees of freedom. We examine the nondeterministic methods whereby such states can be created from single photons and/or Bell pairs and then give some mechanisms for performing higher-dimensional fusion gates.
Connection between the hydrogen atom and the four-dimensional oscillator
Chen, A.C.; Kibler, M.
1985-06-01
The connection between the three-dimensional hydrogen atom and a four-dimensional harmonic oscillator (or equivalently a coupled pair of two-dimensional harmonic oscillators) subjected to a constraint condition is further explored. In particular, the role the constraint condition plays in determining the phase relationship between the pair of two-dimensional oscillators is examined. Furthermore, the connection is discussed in a group-theoretical context involving the Lie algebras of SO(4), SO(3,1), E(3), SO(4,2), and Sp(8,R).
Two-charge rotating black holes in four-dimensional gauged supergravity
NASA Astrophysics Data System (ADS)
Chow, David D. K.
2011-09-01
We obtain an asymptotically AdS, non-extremal, electrically charged and rotating black hole solution of four-dimensional U(1)4 gauged supergravity with two non-zero and independent U(1) charges. The thermodynamical quantities are computed. We find BPS solutions that are nakedly singular. The solution is generalized to include a NUT parameter and dyonic gauge fields. The string frame metric has a rank-2 Killing-Stäckel tensor and has completely integrable geodesic motion, and the massless Klein-Gordon equation separates for the Einstein frame metric.
Four-dimensional generalized difference matrix and some double sequence spaces
NASA Astrophysics Data System (ADS)
Tuǧ, Orhan; Başar, Feyzi
2016-08-01
In this study, we introduce some new double sequence spaces B(Mu), B(Cp), B(Cbp), B(Cr) and B(Lq) as the domain of four-dimensional generalized difference matrix B(r,s,t,u) in the spaces Mu, Cp, Cbp, Cr and Lq, respectively. We show that the double sequence spaces B(Mu), B(Cbp) and B(Cr) are the Banach spaces under some certain conditions. We give some inclusion relations with some topological properties.
Model independent determination of the gluon condensate in four dimensional SU(3) gauge theory.
Bali, Gunnar S; Bauer, Clemens; Pineda, Antonio
2014-08-29
We determine the nonperturbative gluon condensate of four-dimensional SU(3) gauge theory in a model-independent way. This is achieved by carefully subtracting high-order perturbation theory results from nonperturbative lattice QCD determinations of the average plaquette. No indications of dimension-two condensates are found. The value of the gluon condensate turns out to be of a similar size as the intrinsic ambiguity inherent to its definition. We also determine the binding energy of a B meson in the heavy quark mass limit. PMID:25215978
NASA Astrophysics Data System (ADS)
Wei, Wei; Xu, Jingjiang; Baran, Utku; Song, Shaozhen; Qin, Wan; Qi, Xiaoli; Wang, Ruikang K.
2016-03-01
We demonstrate in vivo volumetric optical microangiography at ˜200 volumes/s by the use of 1.6 MHz Fourier domain mode-locking swept source optical coherence tomography and an effective 36 kHz microelectromechanical system (MEMS) scanner. We propose an intervolume analysis strategy to contrast the dynamic blood flow signal from the static tissue background. The proposed system is demonstrated by imaging cerebral blood flow in mice in vivo. For the first time, imaging speed, sensitivity, and temporal resolution become possible for a direct four-dimensional observation of microcirculations within live body parts.
The pedagogical value of the four-dimensional picture: I. Relativistic mechanics of point particles
NASA Astrophysics Data System (ADS)
Kosyakov, B. P.
2014-03-01
In this paper we outline two subjects of relativistic mechanics: (i) the set of allowable world lines, and (ii) the origin of the relativistic law of dynamics governing point particles. We show that: (i) allowable world lines in the classical theory of particles and fields are quite simple geometric objects as opposed to their associated three-dimensional trajectories; and (ii) Newton’s second law requires neither modification nor generalization, it should only be smoothly embedded in the four-dimensional geometry of Minkowski spacetime to yield the dynamical law for relativistic particles.
A four-dimensional model with the fermionic determinant exactly evaluated
NASA Astrophysics Data System (ADS)
Mignaco, J. A.; Rego Monteiro, M. A.
1986-07-01
A method is presented to compute the fermion determinant of some class of field theories. By this method the following results of the fermion determinant in two dimensions are easily recovered: (i) Schwinger model without reference to a particular gauge. (ii) QCD in the light-cone gauge. (iii) Gauge invariant result of QCD. The method is finally applied to give an analytical solution of the fermion determinant of a four-dimensional, non-abelian, Dirac-like theory with massless fermions interacting with an external vector field through a pseudo-vectorial coupling. Fellow of the Conselho Nacional de Desenvolvimento Cientifico e Tecnologico (CNPq), Brazil.
Troupis, John M; Bell, Simon N
2014-01-01
Thoracic outlet syndrome is caused by compression of the neurovascular structures crossing the interscalene triangle, costoclavicular space or retropectoralis minor space. The costoclavicular space is the most frequent site of arterial compression and is mainly a result of anatomical variations and masses occupying the costoclavicular space causing a compression effect on the vascular or neural structures within it. We present a case of thoracic outlet syndrome caused by dynamic impingement of the clavicle and the second rib diagnosed by four-dimensional computed tomography scanning.
Ultrafast core-loss spectroscopy in four-dimensional electron microscopy
van der Veen, Renske M.; Penfold, Thomas J.; Zewail, Ahmed H.
2015-01-01
We demonstrate ultrafast core-electron energy-loss spectroscopy in four-dimensional electron microscopy as an element-specific probe of nanoscale dynamics. We apply it to the study of photoexcited graphite with femtosecond and nanosecond resolutions. The transient core-loss spectra, in combination with ab initio molecular dynamics simulations, reveal the elongation of the carbon-carbon bonds, even though the overall behavior is a contraction of the crystal lattice. A prompt energy-gap shrinkage is observed on the picosecond time scale, which is caused by local bond length elongation and the direct renormalization of band energies due to temperature-dependent electron–phonon interactions. PMID:26798793
A novel four-dimensional analytical approach for analysis of complex samples.
Stephan, Susanne; Jakob, Cornelia; Hippler, Jörg; Schmitz, Oliver J
2016-05-01
A two-dimensional LC (2D-LC) method, based on the work of Erni and Frei in 1978, was developed and coupled to an ion mobility-high-resolution mass spectrometer (IM-MS), which enabled the separation of complex samples in four dimensions (2D-LC, ion mobility spectrometry (IMS), and mass spectrometry (MS)). This approach works as a continuous multiheart-cutting LC system, using a long modulation time of 4 min, which allows the complete transfer of most of the first - dimension peaks to the second - dimension column without fractionation, in comparison to comprehensive two-dimensional liquid chromatography. Hence, each compound delivers only one peak in the second dimension, which simplifies the data handling even when ion mobility spectrometry as a third and mass spectrometry as a fourth dimension are introduced. The analysis of a plant extract from Ginkgo biloba shows the separation power of this four-dimensional separation method with a calculated total peak capacity of more than 8700. Furthermore, the advantage of ion mobility for characterizing unknown compounds by their collision cross section (CCS) and accurate mass in a non-target approach is shown for different matrices like plant extracts and coffee. Graphical abstract Principle of the four-dimensional separation. PMID:27038056
Four-dimensional modulation and coding: An alternate to frequency-reuse
NASA Technical Reports Server (NTRS)
Wilson, S. G.; Sleeper, H. A.
1983-01-01
Four dimensional modulation as a means of improving communication efficiency on the band-limited Gaussian channel, with the four dimensions of signal space constituted by phase orthogonal carriers (cos omega sub c t and sin omega sub c t) simultaneously on space orthogonal electromagnetic waves are discussed. "Frequency reuse' techniques use such polarization orthogonality to reuse the same frequency slot, but the modulation is not treated as four dimensional, rather a product of two-d modulations, e.g., QPSK. It is well known that, higher dimensionality signalling affords possible improvements in the power bandwidth sense. Four-D modulations based upon subsets of lattice-packings in four-D, which afford simplification of encoding and decoding are described. Sets of up to 1024 signals are constructed in four-D, providing a (Nyquist) spectral efficiency of up to 10 bps/Hz. Energy gains over the reuse technique are in the one to three dB range t equal bandwidth.
Four-dimensional modulation and coding - An alternate to frequency-reuse
NASA Technical Reports Server (NTRS)
Wilson, S. G.; Sleeper, H. A.; Srinath, N. K.
1984-01-01
Four dimensional modulation as a means of improving communication efficiency on the band-limited Gaussian channel, with the four dimensions of signal space constituted by phase orthogonal carriers (cos omega sub c t and sin omega sub c t) simultaneously on space orthogonal electromagnetic waves are discussed. 'Frequency reuse' techniques use such polarization orthogonality to reuse the same frequency slot, but the modulation is not treated as four dimensional, rather a product of two-D modulations, e.g., QPSK. It is well known that, higher dimensionality signalling affords possible improvements in the power bandwidth sense. Four-D modulations based upon subsets of lattice-packings in four-D, which afford simplification of encoding and decoding are described. Sets of up to 1024 signals are constructed in four-D, providing a (Nyquist) spectral efficiency of up to 10 bps/Hz. Energy gains over the reuse technique are in the one to three dB range t equal bandwidth.
Four dimensional chaos and intermittency in a mesoscopic model of the electroencephalogram.
Dafilis, Mathew P; Frascoli, Federico; Cadusch, Peter J; Liley, David T J
2013-06-01
The occurrence of so-called four dimensional chaos in dynamical systems represented by coupled, nonlinear, ordinary differential equations is rarely reported in the literature. In this paper, we present evidence that Liley's mesoscopic theory of the electroencephalogram (EEG), which has been used to describe brain activity in a variety of clinically relevant contexts, possesses a chaotic attractor with a Kaplan-Yorke dimension significantly larger than three. This accounts for simple, high order chaos for a physiologically admissible parameter set. Whilst the Lyapunov spectrum of the attractor has only one positive exponent, the contracting dimensions are such that the integer part of the Kaplan-Yorke dimension is three, thus giving rise to four dimensional chaos. A one-parameter bifurcation analysis with respect to the parameter corresponding to extracortical input is conducted, with results indicating that the origin of chaos is due to an inverse period doubling cascade. Hence, in the vicinity of the high order, strange attractor, the model is shown to display intermittent behavior, with random alternations between oscillatory and chaotic regimes. This phenomenon represents a possible dynamical justification of some of the typical features of clinically established EEG traces, which can arise in the case of burst suppression in anesthesia and epileptic encephalopathies in early infancy. PMID:23822476
Non-Invasive Evaluation of Heart Function with Four-Dimensional Echocardiography
Chen, Ran; Zhu, Meihua; Sahn, David J.; Ashraf, Muhammad
2016-01-01
Background The aim of this study is to assess the accuracy and feasibility of left ventricular systolic function determined by four-dimensional echocardiography (4DE). Methods Latex balloons were sewn into the left ventricle (LV) of 20 freshly harvested pig hearts which were then passively driven by a pulsatile pump apparatus. Global longitudinal strain (GLS), global circumferential strain (GCS), global area strain (GAS) and left ventricular ejection fraction (LVEF) derived from 4DEand two-dimensional echocardiography (2DE)-derived LVEF were quantified at different stroke volumes (SV) 30–70 ml and correlated with sonomicrometry data. Results In all comparisons, GLS, GCS, GAS, 2DE-LVEF, and 4DE-LVEF demonstrated strong correlations with sonomicrometry data (r = 0.77, r = 0.89, r = 0.79, r = 0.93, r = 0.96, all P <0.001). Bland-Altman analyses showed slight overestimations of echo-derived GLS, GCS, 2DE-LVEF and 3DE-LVEF over sonomicrometry values (bias = 2.88, bias = 3.99, bias = 3.37, bias = 2.78, respectively). Furthermore, there is better agreement between GCS, 4D LVEF and sonomicrometry values compared with GLS and 2D LVEF. Conclusion Four-dimensional echocardiography accurately assesses LV function. GCS derived by 4DE is a potential alternative parameter to quantify LV systolic function. PMID:27144844
Four dimensional chaos and intermittency in a mesoscopic model of the electroencephalogram
NASA Astrophysics Data System (ADS)
Dafilis, Mathew P.; Frascoli, Federico; Cadusch, Peter J.; Liley, David T. J.
2013-06-01
The occurrence of so-called four dimensional chaos in dynamical systems represented by coupled, nonlinear, ordinary differential equations is rarely reported in the literature. In this paper, we present evidence that Liley's mesoscopic theory of the electroencephalogram (EEG), which has been used to describe brain activity in a variety of clinically relevant contexts, possesses a chaotic attractor with a Kaplan-Yorke dimension significantly larger than three. This accounts for simple, high order chaos for a physiologically admissible parameter set. Whilst the Lyapunov spectrum of the attractor has only one positive exponent, the contracting dimensions are such that the integer part of the Kaplan-Yorke dimension is three, thus giving rise to four dimensional chaos. A one-parameter bifurcation analysis with respect to the parameter corresponding to extracortical input is conducted, with results indicating that the origin of chaos is due to an inverse period doubling cascade. Hence, in the vicinity of the high order, strange attractor, the model is shown to display intermittent behavior, with random alternations between oscillatory and chaotic regimes. This phenomenon represents a possible dynamical justification of some of the typical features of clinically established EEG traces, which can arise in the case of burst suppression in anesthesia and epileptic encephalopathies in early infancy.
Wang, Shang; Lakomy, David S; Garcia, Monica D; Lopez, Andrew L; Larin, Kirill V; Larina, Irina V
2016-08-01
Hemodynamic analysis of the mouse embryonic heart is essential for understanding the functional aspects of early cardiogenesis and advancing the research in congenital heart defects. However, high-resolution imaging of cardiac hemodynamics in mammalian models remains challenging, primarily due to the dynamic nature and deep location of the embryonic heart. Here we report four-dimensional micro-scale imaging of blood flow in the early mouse embryonic heart, enabling time-resolved measurement and analysis of flow velocity throughout the heart tube. Our method uses Doppler optical coherence tomography in live mouse embryo culture, and employs a post-processing synchronization approach to reconstruct three-dimensional data over time at a 100 Hz volume rate. Experiments were performed on live mouse embryos at embryonic day 9.0. Our results show blood flow dynamics inside the beating heart, with the capability for quantitative flow velocity assessment in the primitive atrium, atrioventricular and bulboventricular regions, and bulbus cordis. Combined cardiodynamic and hemodynamic analysis indicates this functional imaging method can be utilized to further investigate the mechanical relationship between blood flow dynamics and cardiac wall movement, bringing new possibilities to study biomechanics in early mammalian cardiogenesis. Four-dimensional live hemodynamic imaging of the mouse embryonic heart at embryonic day 9.0 using Doppler optical coherence tomography, showing directional blood flows in the sinus venosus, primitive atrium, atrioventricular region and vitelline vein. PMID:26996292
Muralidhar, K R; Komanduri, Krishna; Rout, Birendra Kumar; Ramesh, K K D
2013-07-01
Four dimensional (4D) target localization system (Calypso System) was installed at our hospital, which is equipped with Beacon Transponders, Console, Electromagnetic Array, Optical System, Tracking Station, Treatment table overlay, and Calypso kVue Couch top. The objective of this presentation is to describe the results of commissioning measurements carried out on the Calypso System to verify the manufacturer specifications and also to evolve a quality assurance (QA) procedure which can be used to test its performance routinely. The QA program consists of a series of tests (QA for checking the calibration or system accuracy, Camera Calibration with L-frame fixture, Camera Calibration with T-frame fixture, System calibration Fixture targets test, Localization, and Tracking). These tests were found to be useful to assess the performance of the Calypso System. PMID:24049322
NASA Astrophysics Data System (ADS)
Man, Tianlong; Wan, Yuhong; Wu, Fan; Wang, Dayong
2015-11-01
We present a new method for the four-dimensional tracking of a spatially incoherent illuminated object. Self-interference digital holography is utilized for recording the hologram of the spatially incoherent illuminated object. Three-dimensional spatial coordinates encoded in the hologram are extracted by holographic reconstruction procedure and tracking algorithms, while the time information is reserved by the single-shot configuration. Applications of the holographic tracking methods are expanded to the incoherent imaging areas. Speckles and potential damage to the samples of the coherent illuminated tracking methods are overcome. Results on the quantitative tracking of three-dimensional spatial position over time are reported. In practical, living zebra fish larva is used to demonstrate one of the applications of the method.
NASA Astrophysics Data System (ADS)
Lopez, Andrew L., III; Wang, Shang; Larin, Kirill V.; Overbeek, Paul A.; Larina, Irina V.
2015-09-01
Efficient phenotyping of developmental defects in model organisms is critical for understanding the genetic specification of normal development and congenital abnormalities in humans. We previously reported that optical coherence tomography (OCT) combined with live embryo culture is a valuable tool for mouse embryo imaging and four-dimensional (4-D) cardiodynamic analysis; however, its capability for analysis of mouse mutants with cardiac phenotypes has not been previously explored. Here, we report 4-D (three-dimensional+time) OCT imaging and analysis of the embryonic heart in a Wdr19 mouse mutant, revealing a heart looping defect. Quantitative analysis of cardiac looping revealed a statistically significant difference between mutant and control embryos. Our results indicate that live 4-D OCT imaging provides a powerful phenotyping approach to characterize embryonic cardiac function in mouse models.
Breakup of invariant tori for the four-dimensional semi-standard map
NASA Astrophysics Data System (ADS)
Bolt, Erik M.; Meiss, James D.
1993-07-01
We compute the domain of existence of two-dimensional invariant tori with fixed frequency vectors for a four-dimensional, complex, symplectic map. The map is a generalization of the semi-standard map studied by Greene and Percival; it has three parameters, a1 and a2 representing the strength of the kicks in each degree of freedom, and ɛ, the coupling. The domain of existence of a torus in ( a1, a2) is shown to be complete and log-convex for fixed k = ɛ/ a1a2. Explicit bounds on the domain for fixed k are obtained. Numerical results show that quadratic irrationals can be more robust than the cubic irrational, “the spiral mean”.
Statistical Entropy of Four-Dimensional Rotating Black Holes from Near-Horizon Geometry
Cvetic, M.; Larsen, F.; Cvetic, M.
1999-01-01
We show that a class of four-dimensional rotating black holes allow five-dimensional embeddings as black rotating strings. Their near-horizon geometry factorizes locally as a product of the three-dimensional anti{endash}de Sitter space-time and a two-dimensional sphere (AdS{sub 3}{times}S{sup 2} ), with angular momentum encoded in the global space-time structure. Following the observation that the isometries on the AdS{sub 3} space induce a two-dimensional (super)conformal field theory on the boundary, we reproduce the microscopic entropy with the correct dependence on the black hole angular momentum. {copyright} {ital 1999} {ital The American Physical Society }
Lu Wei; Low, Daniel A.; Parikh, Parag J.; Nystrom, Michelle M.; El Naqa, Issam M.; Wahab, Sasha H.; Handoko, Maureen; Fooshee, David; Bradley, Jeffrey D.
2005-07-15
An important consideration in four-dimensional CT scanning is the selection of a breathing metric for sorting the CT data and modeling internal motion. This study compared two noninvasive breathing metrics, spirometry and abdominal height, against internal air content, used as a surrogate for internal motion. Both metrics were shown to be accurate, but the spirometry showed a stronger and more reproducible relationship than the abdominal height in the lung. The abdominal height was known to be affected by sensor placement and patient positioning while the spirometer exhibited signal drift. By combining these two, a normalization of the drift-free metric to tidal volume may be generated and the overall metric precision may be improved.
A time-parallel approach to strong-constraint four-dimensional variational data assimilation
NASA Astrophysics Data System (ADS)
Rao, Vishwas; Sandu, Adrian
2016-05-01
A parallel-in-time algorithm based on an augmented Lagrangian approach is proposed to solve four-dimensional variational (4D-Var) data assimilation problems. The assimilation window is divided into multiple sub-intervals that allows parallelization of cost function and gradient computations. The solutions to the continuity equations across interval boundaries are added as constraints. The augmented Lagrangian approach leads to a different formulation of the variational data assimilation problem than the weakly constrained 4D-Var. A combination of serial and parallel 4D-Vars to increase performance is also explored. The methodology is illustrated on data assimilation problems involving the Lorenz-96 and the shallow water models.
Flame four-dimensional deflection tomography with compressed-sensing-revision reconstruction
NASA Astrophysics Data System (ADS)
Zhang, Bin; Zhao, Minmin; Liu, Zhigang; Wu, Zhaohang
2016-08-01
Deflection tomography with limited angle projections was investigated to visualize a premixed flame. A projection sampling system for deflection tomography was used to obtain chronological deflectogram arrays at six view angles with only a pair of gratings. A new iterative reconstruction algorithm with deflection angle compressed-sensing revision was developed to improve reconstruction-distribution quality from incomplete projection data. Numerical simulation and error analysis provided a good indication of algorithm precision and convergence. In the experiment, 150 fringes were processed, and temperature distributions in 20 cross-sections were reconstructed from projection data in four instants. Four-dimensional flame structures and temperature distributions in the flame interior were visualized using the visualization toolkit. The experimental reconstruction was then compared with the result obtained from computational fluid dynamic analysis.
Gronenborn, A.M.; Clore, G.M.
1994-12-01
Complete understanding of a protein`s function and mechanism of action can only be achieved with a knowledge of its three-dimensional structure at atomic resolution. At present, there are two methods available for determining such structures. The first method, which has been established for many years, is x-ray diffraction of protein single crystals. The second method has blossomed only in the last 5 years and is based on the application of nuclear magnetic resonance (NMR) spectroscopy to proteins in solution. This review paper describes three- and four-dimensional NMR methods applied to protein structure determination and was adapted from Clore and Gronenborn. The review focuses on the underlying principals and practice of multidimensional NMR and the structural information obtained.
Four-dimensional motility tracking of biological cells by digital holographic microscopy
Yu, Xiao; Hong, Jisoo; Liu, Changgeng; Cross, Michael; Haynie, Donald T.; Kim, Myung K.
2014-01-01
Abstract. Three-dimensional profiling and tracking by digital holography microscopy (DHM) provide label-free and quantitative analysis of the characteristics and dynamic processes of objects, since DHM can record real-time data for microscale objects and produce a single hologram containing all the information about their three-dimensional structures. Here, we have utilized DHM to visualize suspended microspheres and microfibers in three dimensions, and record the four-dimensional trajectories of free-swimming cells in the absence of mechanical focus adjustment. The displacement of microfibers due to interactions with cells in three spatial dimensions has been measured as a function of time at subsecond and micrometer levels in a direct and straightforward manner. It has thus been shown that DHM is a highly efficient and versatile means for quantitative tracking and analysis of cell motility. PMID:24699632
A four-dimensional, mesoscale, non-gaussian multispectral smoke model. Phase 1: Feasibility study
NASA Astrophysics Data System (ADS)
Yamartino, R. J.; Strimaitis, D. G.; Scire, J. S.; Insley, E. M.
1992-12-01
The feasibility of developing a four-dimensional, non-Gaussian mesoscale multispectral smoke model that could run on a personal computer is investigated. Several of the model components are formulated, coded, and tested. This included the main driver program for accessing and interpolating the mesoscale winds and generating particle trajectories, a sub-grid-scale velocity field generator based on the kinematic simulation approach, and a dry deposition model for particle deposition velocities. Current understanding of flow and turbulence modeling is reviewed and can be applied to developing appropriate kinematic simulation fields. Technical approaches to account for the height and particle size dependent probability of particle removal and to compute the point and path average particle concentrations are also presented. Conclusions and recommendations for future work are included.
A four-dimensional primitive equation model for coupled coastal-deep ocean studies
NASA Technical Reports Server (NTRS)
Haidvogel, D. B.
1981-01-01
A prototype four dimensional continental shelf/deep ocean model is described. In its present form, the model incorporates the effects of finite amplitude topography, advective nonlinearities, and variable stratification and rotation. The model can be forced either directly by imposed atmospheric windstress and surface pressure distributions, and energetic mean currents imposed by the exterior oceanic circulation; or indirectly by initial distributions of shoreward propagation mesoscale waves and eddies. To avoid concerns over the appropriate specification of 'open' boundary conditions on the cross-shelf and seaward model boundaries, a periodic channel geometry (oriented along-coast) is used. The model employs a traditional finite difference expansion in the cross-shelf direction, and a Fourier (periodic) representation in the long-shelf coordinate.
Muralidhar, K. R.; Komanduri, Krishna; Rout, Birendra Kumar; Ramesh, K. K. D.
2013-01-01
Four dimensional (4D) target localization system (Calypso System) was installed at our hospital, which is equipped with Beacon Transponders, Console, Electromagnetic Array, Optical System, Tracking Station, Treatment table overlay, and Calypso kVue Couch top. The objective of this presentation is to describe the results of commissioning measurements carried out on the Calypso System to verify the manufacturer specifications and also to evolve a quality assurance (QA) procedure which can be used to test its performance routinely. The QA program consists of a series of tests (QA for checking the calibration or system accuracy, Camera Calibration with L-frame fixture, Camera Calibration with T-frame fixture, System calibration Fixture targets test, Localization, and Tracking). These tests were found to be useful to assess the performance of the Calypso System. PMID:24049322
Metallic phase of the quantum Hall effect in four-dimensional space
NASA Astrophysics Data System (ADS)
Edge, Jonathan; Tworzydlo, Jakub; Beenakker, Carlo
2013-03-01
We study the phase diagram of the quantum Hall effect in four-dimensional (4D) space. Unlike in 2D, in 4D there exists a metallic as well as an insulating phase, depending on the disorder strength. The critical exponent ν ~ 1 . 2 of the diverging localization length at the quantum Hall insulator-to-metal transition differs from the semiclassical value ν = 1 of 4D Anderson transitions in the presence of time-reversal symmetry. Our numerical analysis is based on a mapping of the 4D Hamiltonian onto a 1D dynamical system, providing a route towards the experimental realization of the 4D quantum Hall effect. NanoCTM, FOM/NWO, ERC
Four-dimensional multiphoton microscopy with time-correlated single-photon counting.
Schönle, A; Glatz, M; Hell, S W
2000-12-01
We report on the implementation of fluorescence-lifetime imaging in multiphoton excitation microscopy that uses PC-compatible modules for time-correlated single-photon counting. Four-dimensional data stacks are produced with each pixel featuring fluorescence-decay curves that consist of as many as 4096 bins. Fluorescence lifetime(s) and their amplitude(s) are extracted by statistical methods at each pixel or in arbitrarily defined regions of interest. When employing an avalanche photodiode the width of the temporal response function is 420 ps. Although this response confines the temporal resolution to values greater than several hundreds of picoseconds, the lifetime precision is determined by the signal-to-noise ratio and can be in the range of tens of picosconds. Lifetime changes are visualized in pulsed-laser-deposited fluorescent layers as well as in cyan fluorescent proteins that transfer energy to yellow fluorescent proteins in live mammalian cells. PMID:18354639
New supersymmetric black holes in four-dimensional N = 2 supergravity
NASA Astrophysics Data System (ADS)
Mandal, Taniya; Tripathy, Prasanta K.
2016-05-01
In this paper, we consider the four-dimensional N = 2 supergravity theory arising from the compactification of type IIA string theory on a Calabi-Yau manifold. We analyze the supersymmetric flow equations for static, spherically symmetric, single-centered black holes. These flow equations are solved by a set of algebraic equations involving the holomorphic sections and harmonic functions. We examine black hole configurations with D0-D4-D6 charge for which the most general solution of these algebraic equations are considered. Though the black hole solution is unique for a given value of the charges, we find new phases of the black hole solutions upon varying them.
Four-dimensional lattice rules generated by skew-circulant matrices.
Lyness, J. N.; Sorevik, T.; Mathematics and Computer Science; Univ. of Bergen
2003-01-01
We introduce the class of skew-circulant lattice rules. These are s-dimensional lattice rules that may be generated by the rows of an s x s skew-circulant matrix. (This is a minor variant of the familiar circulant matrix.) We present briefly some of the underlying theory of these matrices and rules. We are particularly interested in finding rules of specified trigonometric degree d. We describe some of the results of computer-based searches for optimal four-dimensional skew-circulant rules. Besides determining optimal rules for {delta} = d + 1 {<=} 47, we have constructed an infinite sequence of rules Q(4, {delta}) that has a limit rho index of 27/34 {approx} 0.79. This index is an efficiency measure, which cannot exceed 1, and is inversely proportional to the abscissa count.
Possible second-order phase transition in strongly coupled unquenched planar four-dimensional QED
Oliensis, J. ); Johnson, P.W. )
1990-07-15
We study chiral-symmetry breaking in four-dimensional QED with {ital N} fermion species using truncated Schwinger-Dyson equations, and taking vacuum-polarization effects into account via a momentum-dependent gauge coupling. These effects transmute the infinite-order phase transition found previously for the case of a fixed gauge coupling into a second-order phase transition. For large {ital N}, the phase transition may not exist, as it is determined primarily by the physics at the cutoff. We also carry out a preliminary renormalization-group analysis of the theory near the critical coupling: the results are compatible with the existence of a nontrivial continuum limit for the planar theory at the critical value, with an effectively dimensionless fermion field.
Berry curvature and four-dimensional monopoles in the relativistic chiral kinetic equation.
Chen, Jiunn-Wei; Pu, Shi; Wang, Qun; Wang, Xin-Nian
2013-06-28
We derive a relativistic chiral kinetic equation with manifest Lorentz covariance from Wigner functions of spin-1/2 massless fermions in a constant background electromagnetic field. It contains vorticity terms and a four-dimensional Euclidean Berry monopole which gives an axial anomaly. By integrating out the zeroth component of the 4-momentum p, we reproduce the previous three-dimensional results derived from the Hamiltonian approach, together with the newly derived vorticity terms. The phase space continuity equation has an anomalous source term proportional to the product of electric and magnetic fields (FσρF[over ˜]σρ∼EσBσ). This provides a unified interpretation of the chiral magnetic and vortical effects, chiral anomaly, Berry curvature, and the Berry monopole in the framework of Wigner functions. PMID:23848865
Four-dimensionally coded PSK systems for combatting effects of severe ISI and CCI
NASA Astrophysics Data System (ADS)
Fang, R.; Lee, W.
A combined forward error correction (FEC) coding and modulation technique is proposed for transmissions over four-dimensional (4-D) channels that are interference and noise limited. Improved error performance is achieved by 4-D channel coding, with the expanded signal set in a manner similar to Ungerboeck's set-partitioning method, which maximizes the free Euclidean distance. Lower bounds on free Euclidean distance at the output of the 4-D modulator are derived for evaluating the asymptotic performance. As an example, a rate 2/3 convolutional encoder combined with a 4-D coded QPSK signal could yield an Eb/No gain of about 3 to 4 dB over an uncoded two-dimensional (2-D) BPSK system. Performance over a linear channel in the presence of thermal noise, intersymbol interference (ISI), and co-channel interference (CCI) is also evaluated.
Four-Dimensional Positron Emission Tomography: Implications for Dose Painting of High-Uptake Regions
Aristophanous, Michalis; Killoran, Joseph H.; Chen, Aileen B.; Berbeco, Ross I.
2011-07-01
Purpose: To investigate the behavior of tumor subvolumes of high [18F]-fluorodeoxyglucose (FDG) uptake as seen on clinical four-dimensional (4D) FDG-positron emission tomography (PET) scans. Methods and Materials: Four-dimensional FDG-PET/computed tomography scans from 13 patients taken before radiotherapy were available. The analysis was focused on regions of high uptake that are potential dose-painting targets. A total of 17 lesions (primary tumors and lymph nodes) were analyzed. On each one of the five phases of the 4D scan a classification algorithm was applied to obtain the region of highest uptake and segment the tumor volume. We looked at the behavior of both the high-uptake subvolume, called 'Boost,' and the segmented tumor volume, called 'Target.' We measured several quantities that characterize the Target and Boost volumes and quantified correlations between them. Results: The behavior of the Target could not always predict the behavior of the Boost. The shape deformation of the Boost regions was on average 133% higher than that of the Target. The gross to internal target volume expansion was on average 27.4% for the Target and 64% for the Boost, a statistically significant difference (p < 0.05). Finally, the inhale-to-exhale phase (20%) had the highest shape deformation for the Boost regions. Conclusions: A complex relationship between the measured quantities for the Boost and Target volumes is revealed. The results suggest that in cases in which advanced therapy techniques such as dose painting are being used, a close examination of the 4D PET scan should be performed.
Four-dimensional computed tomography (4DCT): A review of the current status and applications.
Kwong, Yune; Mel, Alexandra Olimpia; Wheeler, Greg; Troupis, John M
2015-10-01
The applications of conventional computed tomography (CT) have been widely researched and implemented in clinical practice. A recent technological innovation in the field of CT is the emergence of four-dimensional computed tomography (4DCT), where a three-dimensional computed tomography volume containing a moving structure is imaged over a period of time, creating a dynamic volume data set. 4DCT has previously been mainly utilised in the setting of radiation therapy planning, but with the development of wide field of view CT, 4DCT has opened major avenues in the diagnostic arena. The aim of this study is to provide a comprehensive narrative review of the literature regarding the current clinical applications of 4DCT. The applications reviewed include both routine diagnostic usage as well as an appraisal of the current research literature. A systematic review of the studies related to 4DCT was conducted. The Medline database was searched using the MeSH subject heading 'Four-Dimensional Computed Tomography'. After excluding non-human and non-English papers, 2598 articles were found. Further exclusion criteria were applied, including date range (since wide field of view CT was introduced in 2007), and exclusion of technical/engineering/physics papers. Further filtration of papers included identification of Review papers. This process yielded 67 papers. Of these, exclusion of papers not specifically discussing 4DCT (cone beam, 4D models) yielded 38 papers. As part of the review, the technique for 4DCT is described, with perspectives as to how it has evolved and its benefits in different clinical indications. PMID:26041442
Breathing-Synchronized Delivery: A Potential Four-Dimensional Tomotherapy Treatment Technique
Zhang Tiezhi . E-mail: tiezhi.zhang@beaumont.edu; Lu Weiguo; Olivera, Gustavo H.; Keller, Harry; Jeraj, Robert; Manon, Rafael; Mehta, Minesh; Mackie, Thomas R.; Paliwal, Bhudatt
2007-08-01
Purpose: To introduce a four-dimensional (4D) tomotherapy treatment technique with improved motion control and patient tolerance. Methods and Materials: Computed tomographic images at 10 breathing phases were acquired for treatment planning. The full exhalation phase was chosen as the planning phase, and the CT images at this phase were used as treatment-planning images. Region of interest delineation was the same as in traditional treatment planning, except that no breathing motion margin was used in clinical target volume-planning target volume expansion. The correlation between delivery and breathing phases was set assuming a constant gantry speed and a fixed breathing period. Deformable image registration yielded the deformation fields at each phase relative to the planning phase. With the delivery/breathing phase correlation and voxel displacements at each breathing phase, a 4D tomotherapy plan was obtained by incorporating the motion into inverse treatment plan optimization. A combined laser/spirometer breathing tracking system has been developed to monitor patient breathing. This system is able to produce stable and reproducible breathing signals representing tidal volume. Results: We compared the 4D tomotherapy treatment planning method with conventional tomotherapy on a static target. The results showed that 4D tomotherapy can achieve dose distributions on a moving target similar to those obtained with conventional delivery on a stationary target. Regular breathing motion is fully compensated by motion-incorporated breathing-synchronized delivery planning. Four-dimensional tomotherapy also has close to 100% duty cycle and does not prolong treatment time. Conclusion: Breathing-synchronized delivery is a feasible 4D tomotherapy treatment technique with improved motion control and patient tolerance.
Preventing Data Ambiguity in Infectious Diseases with Four-Dimensional and Personalized Evaluations
Iandiorio, Michelle J.; Fair, Jeanne M.; Chatzipanagiotou, Stylianos; Ioannidis, Anastasios; Trikka-Graphakos, Eleftheria; Charalampaki, Nikoletta; Sereti, Christina; Tegos, George P.; Hoogesteijn, Almira L.; Rivas, Ariel L.
2016-01-01
Background Diagnostic errors can occur, in infectious diseases, when anti-microbial immune responses involve several temporal scales. When responses span from nanosecond to week and larger temporal scales, any pre-selected temporal scale is likely to miss some (faster or slower) responses. Hoping to prevent diagnostic errors, a pilot study was conducted to evaluate a four-dimensional (4D) method that captures the complexity and dynamics of infectious diseases. Methods Leukocyte-microbial-temporal data were explored in canine and human (bacterial and/or viral) infections, with: (i) a non-structured approach, which measures leukocytes or microbes in isolation; and (ii) a structured method that assesses numerous combinations of interacting variables. Four alternatives of the structured method were tested: (i) a noise-reduction oriented version, which generates a single (one data point-wide) line of observations; (ii) a version that measures complex, three-dimensional (3D) data interactions; (iii) a non-numerical version that displays temporal data directionality (arrows that connect pairs of consecutive observations); and (iv) a full 4D (single line-, complexity-, directionality-based) version. Results In all studies, the non-structured approach revealed non-interpretable (ambiguous) data: observations numerically similar expressed different biological conditions, such as recovery and lack of recovery from infections. Ambiguity was also found when the data were structured as single lines. In contrast, two or more data subsets were distinguished and ambiguity was avoided when the data were structured as complex, 3D, single lines and, in addition, temporal data directionality was determined. The 4D method detected, even within one day, changes in immune profiles that occurred after antibiotics were prescribed. Conclusions Infectious disease data may be ambiguous. Four-dimensional methods may prevent ambiguity, providing earlier, in vivo, dynamic, complex, and
Dynamic Imaging of Vocal Fold Oscillation With Four-Dimensional Optical Coherence Tomography
Kobler, James B.; Chang, Ernest W.; Zeitels, Steven M.; Yun, Seok-Hyun
2011-01-01
Objectives/Hypothesis Optical coherence tomography (OCT) can provide high-resolution (~10–15 μm/pixel) images of vocal fold microanatomy, as demonstrated previously. We explored physiologically triggered Fourier-domain OCT for imaging vocal folds during phonation. The goal is to visualize dynamic histological cross sections and four-dimensional data sets where multiple planes are displayed in synchronized motion. If feasible, this approach could be a useful research tool and spur development of new clinical instrumentation. Study Design A Fourier-domain, triggered OCT system was created and tested in experiments on excised calf larynges to obtain preliminary observations and characterize important factors affecting image quality. Methods Larynges were imaged during phonation driven by warm, humidified air. A subglottal pressure signal was used to synchronize the OCT system with the phonatory cycle. Image sequences were recorded as functions of anatomical location or sub-glottal pressure. Implant materials were also imaged during vibration, both in isolation and after injection into a vocal fold. Results Oscillations of epithelium and lamina propria were observed, and parameters such as shape, amplitude, and velocity of the vocal fold mucosal waves were found to be measurable. Ripples of mucosal wave as small as 100 μm in vertical height were clearly visible. Internal strain was also observed in normal and implanted vocal folds. Conclusions Four-dimensional OCT of the vocal fold may help to more directly relate biomechanics to anatomy and disease. It may also be useful for assaying the functional rheology of implants in the context of real tissue. With further development, this technology has potential for clinical endoscopic application. PMID:20564724
Lp p-harmonic 1-forms on submanifolds in a Hadamard manifold
NASA Astrophysics Data System (ADS)
Han, Yingbo; Pan, Hong
2016-09-01
Let Mm(m ≥ 3) be an m-dimensional complete noncompact oriented submanifold with finite total curvature, in a Hadamard manifold N m + n with the sectional curvature satisfying -k2
NASA Astrophysics Data System (ADS)
Franke, Philipp; Elbern, Hendrik
2016-04-01
Estimating volcanic ash emissions is a very challenging task due to limited monitoring capacities of the ash plume and nonlinear processes in the atmosphere, which renders application of source strength and injection height estimations difficult. Most models, which estimate volcanic ash emissions, make strong simplifications of the dispersion of volcanic ash and corresponding atmospheric processes. The objective of this work is to estimate volcanic ash emissions and simulate the ensuing dispersion applying a full chemistry transport model in a hybrid approach by using its adjoint as well as an ensemble of model runs to quantify forecast uncertainties. Therefore, the four dimensional variational data assimilation version of the EURAD-IM chemistry transport model is extended to include a Sequential Importance Resampling Smoother (SIRS), introducing novel weighting and resampling strategies. In the main SIRS step the ensemble members exchange high rated emission patterns while rejecting emission patterns with low value for the forecast. The emission profiles of the ensemble members are perturbed afterwards to guarantee different emissions for all ensemble members. First identical twin experiments show the ability of the system to estimate the temporal and vertical distribution of volcanic ash emissions. The 4D-var data assimilation algorithm of the new system additionally provides quantitative emission estimation.
Spatially isotropic four-dimensional imaging with dual-view plane illumination microscopy
Wu, Yicong; Wawrzusin, Peter; Senseney, Justin; Fischer, Robert S; Christensen, Ryan; Santella, Anthony; York, Andrew G; Winter, Peter W; Waterman, Clare M; Bao, Zhirong; Colón-Ramos, Daniel A; McAuliffe, Matthew; Shroff, Hari
2014-01-01
Optimal four-dimensional imaging requires high spatial resolution in all dimensions, high speed and minimal photobleaching and damage. We developed a dual-view, plane illumination microscope with improved spatiotemporal resolution by switching illumination and detection between two perpendicular objectives in an alternating duty cycle. Computationally fusing the resulting volumetric views provides an isotropic resolution of 330 nm. As the sample is stationary and only two views are required, we achieve an imaging speed of 200 images/s (i.e., 0.5 s for a 50-plane volume). Unlike spinning-disk confocal or Bessel beam methods, which illuminate the sample outside the focal plane, we maintain high spatiotemporal resolution over hundreds of volumes with negligible photobleaching. To illustrate the ability of our method to study biological systems that require high-speed volumetric visualization and/or low photobleaching, we describe microtubule tracking in live cells, nuclear imaging over 14 h during nematode embryogenesis and imaging of neural wiring during Caenorhabditis elegans brain development over 5 h. PMID:24108093
A four-dimensional snapshot hyperspectral video-endoscope for bio-imaging applications
Lim, Hoong-Ta; Murukeshan, Vadakke Matham
2016-01-01
Hyperspectral imaging has proven significance in bio-imaging applications and it has the ability to capture up to several hundred images of different wavelengths offering relevant spectral signatures. To use hyperspectral imaging for in vivo monitoring and diagnosis of the internal body cavities, a snapshot hyperspectral video-endoscope is required. However, such reported systems provide only about 50 wavelengths. We have developed a four-dimensional snapshot hyperspectral video-endoscope with a spectral range of 400–1000 nm, which can detect 756 wavelengths for imaging, significantly more than such systems. Capturing the three-dimensional datacube sequentially gives the fourth dimension. All these are achieved through a flexible two-dimensional to one-dimensional fiber bundle. The potential of this custom designed and fabricated compact biomedical probe is demonstrated by imaging phantom tissue samples in reflectance and fluorescence imaging modalities. It is envisaged that this novel concept and developed probe will contribute significantly towards diagnostic in vivo biomedical imaging in the near future. PMID:27044607
Simulations of four-dimensional simplicial quantum gravity as dynamical triangulation
Agishtein, M.E.; Migdal, A.A. )
1992-04-20
In this paper, Four-Dimensional Simplicial Quantum Gravity is simulated using the dynamical triangulation approach. The authors studied simplicial manifolds of spherical topology and found the critical line for the cosmological constant as a function of the gravitational one, separating the phases of opened and closed Universe. When the bare cosmological constant approaches this line from above, the four-volume grows: the authors reached about 5 {times} 10{sup 4} simplexes, which proved to be sufficient for the statistical limit of infinite volume. However, for the genuine continuum theory of gravity, the parameters of the lattice model should be further adjusted to reach the second order phase transition point, where the correlation length grows to infinity. The authors varied the gravitational constant, and they found the first order phase transition, similar to the one found in three-dimensional model, except in 4D the fluctuations are rather large at the transition point, so that this is close to the second order phase transition. The average curvature in cutoff units is large and positive in one phase (gravity), and small negative in another (antigravity). The authors studied the fractal geometry of both phases, using the heavy particle propagator to define the geodesic map, as well as with the old approach using the shortest lattice paths.
Zhao, Kristin; Breighner, Ryan; Holmes, David; Leng, Shuai; McCollough, Cynthia; An, Kai-Nan
2015-07-01
Accurate quantification of subtle wrist motion changes resulting from ligament injuries is crucial for diagnosis and prescription of the most effective interventions for preventing progression to osteoarthritis. Current imaging techniques are unable to detect injuries reliably and are static in nature, thereby capturing bone position information rather than motion which is indicative of ligament injury. A recently developed technique, 4D (three dimensions + time) computed tomography (CT) enables three-dimensional volume sequences to be obtained during wrist motion. The next step in successful clinical implementation of the tool is quantification and validation of imaging biomarkers obtained from the four-dimensional computed tomography (4DCT) image sequences. Measures of bone motion and joint proximities are obtained by: segmenting bone volumes in each frame of the dynamic sequence, registering their positions relative to a known static posture, and generating surface polygonal meshes from which minimum distance (proximity) measures can be quantified. Method accuracy was assessed during in vitro simulated wrist movement by comparing a fiducial bead-based determination of bone orientation to a bone-based approach. The reported errors for the 4DCT technique were: 0.00-0.68 deg in rotation; 0.02-0.30 mm in translation. Results are on the order of the reported accuracy of other image-based kinematic techniques. PMID:25901447
Four-dimensional 1H and 23Na imaging using continuously oscillating gradients.
Star-Lack, J M; Roos, M S; Wong, S T; Schepkin, V D; Budinger, T F
1997-02-01
A class of fast magnetic spectroscopic imaging methods using continuously oscillating gradients for four-dimensional (three spatial and one spectral) localization is introduced. Sampling may start immediately following the application of an RF excitation pulse, thus enabling measurement of spin density, chemical shift, and relaxation rates of short-T2 species. For spatial localization, steady-state sinusoidal gradient waveforms are used to sample a ball in k space. The two types of trajectories presented include: (1) continuously oscillating gradients with continuously rotating direction used for steady-state free-precession imaging and (2) continuously oscillating gradients followed by a spoiler directed along discrete projections. Design criteria are given and spatial-spectral and spatial-temporal reconstruction methods are developed. Theoretical point-spread functions and signal-to-noise ratios are derived while considering T2*, off-resonance effects, and RF excitation options. Experimental phantom, in vivo, and in vitro 1H and 23Na images collected at 2.35 T are presented. The 1H images were acquired with isotropic spatial resolution ranging from 0.03 to 0.27 cm3 and gradient-oscillation frequencies ranging from 600 to 700 Hz, thus allowing for the separation of water and lipid signals within a voxel. The 23Na images, acquired with 500 and 800 Hz gradient waveforms and 0.70 cm3 isotropic resolution, were resolved in the time domain, yielding spatially localized FIDs. PMID:9169223
Relativistic positioning: four-dimensional numerical approach in Minkowski space-time
NASA Astrophysics Data System (ADS)
Puchades, Neus; Sáez, Diego
2012-10-01
We simulate the satellite constellations of two Global Navigation Satellite Systems: Galileo (EU) and GPS (USA). Satellite motions are described in the Schwarzschild space-time produced by an idealized spherically symmetric non rotating Earth. The trajectories are then circumferences centered at the same point as Earth. Photon motions are described in Minkowski space-time, where there is a well known relation, (Coll et al. in Class. Quantum Gravit. 27:065013, 2010a), between the emission and inertial coordinates of any event. Here, this relation is implemented in a numerical code, which is tested and applied. The first application is a detailed numerical four-dimensional analysis of the so-called emission coordinate region and co-region. In a second application, a GPS (Galileo) satellite is considered as the receiver and its emission coordinates are given by four Galileo (GPS) satellites. The bifurcation problem (double localization) in the positioning of the receiver satellite is then pointed out and discussed in detail.
A four-dimensional snapshot hyperspectral video-endoscope for bio-imaging applications.
Lim, Hoong-Ta; Murukeshan, Vadakke Matham
2016-01-01
Hyperspectral imaging has proven significance in bio-imaging applications and it has the ability to capture up to several hundred images of different wavelengths offering relevant spectral signatures. To use hyperspectral imaging for in vivo monitoring and diagnosis of the internal body cavities, a snapshot hyperspectral video-endoscope is required. However, such reported systems provide only about 50 wavelengths. We have developed a four-dimensional snapshot hyperspectral video-endoscope with a spectral range of 400-1000 nm, which can detect 756 wavelengths for imaging, significantly more than such systems. Capturing the three-dimensional datacube sequentially gives the fourth dimension. All these are achieved through a flexible two-dimensional to one-dimensional fiber bundle. The potential of this custom designed and fabricated compact biomedical probe is demonstrated by imaging phantom tissue samples in reflectance and fluorescence imaging modalities. It is envisaged that this novel concept and developed probe will contribute significantly towards diagnostic in vivo biomedical imaging in the near future. PMID:27044607
Uddin, A K M Nizam; Mansfield, Darren R; Farmer, Michael W; Lau, Kenneth K
2015-12-01
Amyloid is a heterogeneous family of extracellular proteinaceous deposits characterized by apple-green birefringence on polarized light microscopy. There are rare case reports of these extracellular deposits accumulating in the upper and central airways. Progressive infiltration may impair glottic and airway function with some cases requiring intervention to improve flow. Bronchoscopy and lung function testing provide dynamic information to monitor for disease progression; however, the recent development of 320 multislice computed tomography (320 CT) enables dynamic, four-dimensional (4-D) evaluation of laryngeal and tracheal structure and function and presents as a noninvasive, low-radiation dose surveillance tool. We reviewed a 43-year-old man with primary amyloidosis of the larynx and central airways who presented with an 18-year history of progressive dysphonia without breathlessness and preserved lung function. 4-D CT demonstrated marked thickening of supraglottic folds and trachea with marked tracheal dilatation. Despite gross structural abnormalities, dynamic function assessed throughout inspiration and expiration was normal, demonstrating neither rigidity nor dynamic collapse. This combination of structural and functional assessment of the proximal airway by 4-D CT is a novel application to surveillance for laryngeal and tracheal amyloid. PMID:26740884
NASA Astrophysics Data System (ADS)
Yumimoto, Keiya; Uno, Itsushi
We developed a four-dimensional variational (4DVAR) data assimilation system for a regional chemical transport model (CTM). In this study, we applied it to inverse modeling of CO emissions in the eastern Asia during April 2001 and demonstrated the feasibility of our assimilation system. Three ground-based observations were used for data assimilation. Assimilated results showed better agreement with observations; they reduced the RMS difference by 16-27%. Observations obtained on board the R/V Ronald H. Brown were used for independent validation of the assimilated results. The CO emissions over industrialized east central China between Shanghai and Beijing were increased markedly by the assimilation. The results show that the annual anthropogenic (fossil and biofuel combustion) CO emissions over China are 147 Tg. Sensitivity analyses using the adjoint model indicate that the high CO concentration measured on 17 April at Rishiri, Japan (which the assimilation was unable to reproduce) originated in Russia or had traveled from outside the Asian region (e.g. Europe).
A four-dimensional virtual hand brain–machine interface using active dimension selection
NASA Astrophysics Data System (ADS)
Rouse, Adam G.
2016-06-01
Objective. Brain–machine interfaces (BMI) traditionally rely on a fixed, linear transformation from neural signals to an output state-space. In this study, the assumption that a BMI must control a fixed, orthogonal basis set was challenged and a novel active dimension selection (ADS) decoder was explored. Approach. ADS utilizes a two stage decoder by using neural signals to both (i) select an active dimension being controlled and (ii) control the velocity along the selected dimension. ADS decoding was tested in a monkey using 16 single units from premotor and primary motor cortex to successfully control a virtual hand avatar to move to eight different postures. Main results. Following training with the ADS decoder to control 2, 3, and then 4 dimensions, each emulating a grasp shape of the hand, performance reached 93% correct with a bit rate of 2.4 bits s‑1 for eight targets. Selection of eight targets using ADS control was more efficient, as measured by bit rate, than either full four-dimensional control or computer assisted one-dimensional control. Significance. ADS decoding allows a user to quickly and efficiently select different hand postures. This novel decoding scheme represents a potential method to reduce the complexity of high-dimension BMI control of the hand.
Four-dimensional dielectric property image obtained from electron spectroscopic imaging series.
Lo, S C; Kai, J J; Chen, F R; Chang, L; Chen, L C; Chiang, C C; Ding, P; Chin, B; Zhang, H; Chen, F
2001-01-01
We have demonstrated a new quantitative method to characterize two-dimensional distributions of energy-dependent dielectric function of materials from low loss electron spectroscopic image (ESI) series. Two problems associated with extracted image-spectrum from the low-loss image series, under-sampling and loss of energy resolution, were overcome by using fast Fourier transformation (FFT) interpolation and maximum entropy deconvolution method. In this study, Black Diamond/Si3N4/SiO2/Si-substrate dielectric layer designed for copper metallization was used as the sample. We show that the reconstructed (FFT interpolated and maximum entropy deconvoluted) image-spectrum obtained from ESI series images can be quantified with the same accuracy as conventional electron energy-loss spectroscopy spectra. Since the analysis of the dielectric function is sensitive to the local thickness of the specimen using Kramers-Kronig analysis, we also developed a new method to quantitatively determine the dielectric constant for low-k materials. We have determined the thickness of the Black Diamond using the extrapolated thickness method from the materials of known dielectric constants. Using Kramers-Kronig formula, the dielectric function map can be deduced from two-dimensional reconstructed single scattering spectra with providing the information of thickness. We proposed a four-dimensional data presentation for revealing the uniformity of the energy dependent property. The accuracy of our methods depends on the thickness determination and on the quality of the reconstructed spectra from the image series. PMID:11918416
Dynamics of neutron-induced fission of 235U using four-dimensional Langevin equations
NASA Astrophysics Data System (ADS)
Pahlavani, M. R.; Mirfathi, S. M.
2015-08-01
Background: Langevin equations have been suggested as a key approach to the dynamical analysis of energy dissipation in excited nuclei, formed during heavy-ion fusion-fission reactions. Recently, a few researchers theoretically reported investigations of fission for light nuclei in a low excitation energy using the Langevin approach, without considering the contribution of pre- and post-scission particles and γ -ray emission. Purpose: We study the dynamical evolution of mass distribution of fission fragments, and neutron and γ -ray multiplicity for 236U as compound nuclei that are constructed after fusion of a neutron and 235U. Method: Energy dissipation of the compound nucleus through fission is calculated using the Langevin dynamical approach combined with a Monte Carlo method. Also the shape of the fissioning nucleus is restricted to "funny hills" parametrization. Results: Fission fragment mass distribution, neutron and γ -ray multiplicity, and the average kinetic energy of emitted neutrons and γ rays at a low excitation energy are calculated using a dynamical model, based on the four-dimensional Langevin equations. Conclusions: The theoretical results show reasonable agreement with experimental data and the proposed dynamical model can well explain the energy dissipation in low energy induced fission.
An inventory of four-dimensional data sets for the earth sciences
NASA Technical Reports Server (NTRS)
Gregory, Terri
1989-01-01
The wide variety of data available to the diligent researcher and the myriad paths to obtaining it are emphasized. This inventory is an attempt to make accessible much of the four-dimensional data available in the world. In this quick-look catalog are listed separate data sets (Data Sets sections), sources of data including centers and large data bases (Sources section), and some data expected to be available in the future (Future Data section). In the Data Sets section, individual data sets are arranged alphabetically by institution, with those archived in the U.S.A. listed first, followed by those found elsewhere. The Sources section includes large data bases, centers, and directories. Sources are arranged alphabetically by country. This section is followed by a Future Data section which is a collection of data sets, experiments, and other future developments of which we are cognizant. A collection of further information and order blanks provided by some of the archiving institutions are presented in the appendix.
Mathematical properties of a class of four-dimensional neutral signature metrics
NASA Astrophysics Data System (ADS)
Brooks, D.; Musoke, N.; McNutt, D.; Coley, A.
2015-11-01
While the Lorentzian and Riemannian metrics for which all polynomial scalar curvature invariants vanish (the VSI property) are well-studied, less is known about the four-dimensional neutral signature metrics with the VSI property. Recently it was shown that the neutral signature metrics belong to two distinct subclasses: the Walker and Kundt metrics. In this paper we have chosen an example from each of the two subcases of the Ricci-flat VSI Walker metrics respectively. To investigate the difference between the metrics we determine the existence of a null, geodesic, expansion-free, shear-free and vorticity-free vector, and classify these spaces using their holonomy algebras. The geometric implications of these algebras are further studied by identifying the recurrent or covariantly constant null vectors, whose existence is required by the holonomy structure in each example. We conclude the paper with a simple example of the equivalence algorithm for these pseudo-Riemannian manifolds, which is the only approach to classification that provides all necessary information to determine equivalence.
Supersymmetric Janus solutions in four-dimensional N =3 gauged supergravity
NASA Astrophysics Data System (ADS)
Karndumri, Parinya
2016-06-01
We construct supersymmetric Janus solutions using four-dimensional N =3 gauged supergravity with S O (3 )×S U (3 ) gauge group. The N =3 supersymmetric AdS4 vacuum with unbroken S O (3 )×S U (3 ), identified with the compactification of eleven-dimensional supergravity on AdS4×N010 , provides a gravity dual of supersymmetric N =3 Chern-Simons-Matter theory in three dimensions with S U (3 ) flavor symmetry. The Janus solutions accordingly describe supersymmetric conformal interfaces within this Chern-Simons-Matter theory via the AdS /CFT holography. We find two classes of Janus solutions preserving respectively (2,1) and (0,1) supersymmetry on the (1 +1 )-dimensional conformal defects. The solution with (2,1) supersymmetry preserves S O (2 )×S O (2 )×S O (2 )⊂S O (3 )×S U (3 ) symmetry while the (0,1) supersymmetric solution is invariant under a larger S O (2 )×S U (2 )×S O (2 ) symmetry.
Four-dimensional IMRT treatment planning using a DMLC motion-tracking algorithm
NASA Astrophysics Data System (ADS)
Suh, Yelin; Sawant, Amit; Venkat, Raghu; Keall, Paul J.
2009-06-01
The purpose of this study is to develop a four-dimensional (4D) intensity-modulated radiation therapy (IMRT) treatment-planning method by modifying and applying a dynamic multileaf collimator (DMLC) motion-tracking algorithm. The 4D radiotherapy treatment scenario investigated is to obtain a 4D treatment plan based on a 4D computed tomography (CT) planning scan and to have the delivery flexible enough to account for changes in tumor position during treatment delivery. For each of 4D CT planning scans from 12 lung cancer patients, a reference phase plan was created; with its MLC leaf positions and three-dimensional (3D) tumor motion, the DMLC motion-tracking algorithm generated MLC leaf sequences for the plans of other respiratory phases. Then, a deformable dose-summed 4D plan was created by merging the leaf sequences of individual phase plans. Individual phase plans, as well as the deformable dose-summed 4D plan, are similar for each patient, indicating that this method is dosimetrically robust to the variations of fractional time spent in respiratory phases on a given 4D CT planning scan. The 4D IMRT treatment-planning method utilizing the DMLC motion-tracking algorithm explicitly accounts for 3D tumor motion and thus hysteresis and nonlinear motion, and is deliverable on a linear accelerator.
NASA Astrophysics Data System (ADS)
Alasti, H.; Cho, Y. B.; Vandermeer, A. D.; Abbas, A.; Norrlinger, B.; Shubbar, S.; Bezjak, A.
2006-06-01
We present treatment planning methods based on four-dimensional computed tomography (4D-CT) to incorporate tumour motion using (1) a static field and (2) a dynamic field. Static 4D fields are determined to include the target in all breathing phases, whereas dynamic 4D fields are determined to follow the shape of the tumour assessed from 4D-CT images with a dynamic weighting factor. The weighting factor selection depends on the reliability of patient breathing and limitations of the delivery system. The static 4D method is compared with our standard protocol for gross tumour volume (GTV) coverage, mean lung dose and V20. It was found that the GTV delineated on helical CT without incorporating breathing motion does not adequately represent the target compared to the GTV delineated from 4D-CT. Dosimetric analysis indicates that the static 4D-CT based technique results in a reduction of the mean lung dose compared with the standard protocol. Measurements on a moving phantom and simulations indicated that 4D radiotherapy (4D-RT) synchronized with respiration-induced motion further reduces mean lung dose and V20, and may allow safe application of dose escalation and CRT/IMRT. The motions of the chest cavity, tumour and thoracic structures of 24 lung cancer patients are also analysed.
A Four-Dimensional Computed Tomography Analysis of Multiorgan Abdominal Motion
Hallman, Joshua L.; Mori, Shinichiro; Sharp, Gregory C.; Lu, Hsiao-Ming; Hong, Theodore S.; Chen, George T.Y.
2012-05-01
Purpose: To characterize and quantify multiorgan respiration-induced motion in the abdomen in liver and pancreatic cancer patients. Methods and Materials: Four-dimensional computed tomography scans were acquired for 18 patients treated for abdominal tumors. Contours of multiple abdominal organs were drawn by the radiation oncologist at one respiratory phase; these contours were propagated to other respiratory phases by deformable registration. Three-dimensional organ models were generated from the resulting contours at each phase. Motions of the bounding box and center of mass were extracted and analyzed for the clinical target volume and organs at risk. Results: On average, the center of mass motion for liver clinical target volumes was 9.7 mm (SD 5 mm) in the superior-inferior direction, with a range of 3 to 18 mm; for pancreatic tumors, the average was 5 mm (SD 1 mm) m with a range of 3 to 7 mm. Abdominal organs move in unison, but with varying amplitudes. Gating near exhale (T40-T60) reduces the range of motion by a factor of {approx}10. Conclusion: We have used deformable registration to calculate the trajectories of abdominal organs in four dimensions, based on center of mass and bounding box motion metrics. Our results are compared with previously reported studies. Possible reasons for differences are discussed.
Subject-specific four-dimensional liver motion modeling based on registration of dynamic MRI.
Noorda, Yolanda H; Bartels, Lambertus W; Viergever, Max A; Pluim, Josien P W
2016-01-01
Magnetic resonance-guided high intensity focused ultrasound treatment of the liver is a promising noninvasive technique for ablation of liver lesions. For the technique to be used in clinical practice, however, the issue of liver motion needs to be addressed. A subject-specific four-dimensional liver motion model is presented that is created based on registration of dynamically acquired magnetic resonance data. This model can be used for predicting the tumor motion trajectory for treatment planning and to indicate the tumor position for treatment guidance. The performance of the model was evaluated on a dynamic scan series that was not used to build the model. The method achieved an average Dice coefficient of 0.93 between the predicted and actual liver profiles and an average vessel misalignment of 3.0 mm. The model performed robustly, with a small variation in the results per subject. The results demonstrate the potential of the model to be used for MRI-guided treatment of liver lesions. Furthermore, the model can possibly be applied in other image-guided therapies, for instance radiotherapy of the liver. PMID:27493981
Morphogenesis of an extended phenotype: four-dimensional ant nest architecture.
Minter, Nicholas J; Franks, Nigel R; Brown, Katharine A Robson
2012-03-01
Animals produce a variety of structures to modify their environments adaptively. Such structures represent extended phenotypes whose development is rarely studied. To begin to rectify this, we used micro-computed tomography (CT) scanning and time-series experiments to obtain the first high-resolution dataset on the four-dimensional growth of ant nests. We show that extrinsic features within the environment, such as the presence of planes between layers of sediment, influence the architecture of Lasius flavus nests, with ants excavating horizontal tunnels along such planes. Intrinsically, the dimensions of the tunnels are associated with individual colonies, the dynamics of excavation can be explained by negative feedback and the angular distribution of tunnels is probably a result of local competition among tunnels for miners. The architecture and dynamics of ant nest excavation therefore result from local interactions of ants with one another and templates inherent in the environment. The influence of the environment on the form of structures has been documented across both biotic and abiotic domains. Our study opens up the utility of CT scanning as a technique for observing the morphogenesis of such structures. PMID:21849386
Morphogenesis of an extended phenotype: four-dimensional ant nest architecture
Minter, Nicholas J.; Franks, Nigel R.; Robson Brown, Katharine A.
2012-01-01
Animals produce a variety of structures to modify their environments adaptively. Such structures represent extended phenotypes whose development is rarely studied. To begin to rectify this, we used micro-computed tomography (CT) scanning and time-series experiments to obtain the first high-resolution dataset on the four-dimensional growth of ant nests. We show that extrinsic features within the environment, such as the presence of planes between layers of sediment, influence the architecture of Lasius flavus nests, with ants excavating horizontal tunnels along such planes. Intrinsically, the dimensions of the tunnels are associated with individual colonies, the dynamics of excavation can be explained by negative feedback and the angular distribution of tunnels is probably a result of local competition among tunnels for miners. The architecture and dynamics of ant nest excavation therefore result from local interactions of ants with one another and templates inherent in the environment. The influence of the environment on the form of structures has been documented across both biotic and abiotic domains. Our study opens up the utility of CT scanning as a technique for observing the morphogenesis of such structures. PMID:21849386
Longitudinal four-dimensional mapping of subcortical anatomy in human development.
Raznahan, Armin; Shaw, Phillip W; Lerch, Jason P; Clasen, Liv S; Greenstein, Deanna; Berman, Rebecca; Pipitone, Jon; Chakravarty, Mallar M; Giedd, Jay N
2014-01-28
Growing access to large-scale longitudinal structural neuroimaging data has fundamentally altered our understanding of cortical development en route to human adulthood, with consequences for basic science, medicine, and public policy. In striking contrast, basic anatomical development of subcortical structures such as the striatum, pallidum, and thalamus has remained poorly described--despite these evolutionarily ancient structures being both intimate working partners of the cortical sheet and critical to diverse developmentally emergent skills and disorders. Here, to begin addressing this disparity, we apply methods for the measurement of subcortical volume and shape to 1,171 longitudinally acquired structural magnetic resonance imaging brain scans from 618 typically developing males and females aged 5-25 y. We show that the striatum, pallidum, and thalamus each follow curvilinear trajectories of volume change, which, for the striatum and thalamus, peak after cortical volume has already begun to decline and show a relative delay in males. Four-dimensional mapping of subcortical shape reveals that (i) striatal, pallidal, and thalamic domains linked to specific fronto-parietal association cortices contract with age whereas other subcortical territories expand, and (ii) each structure harbors hotspots of sexually dimorphic change over adolescence--with relevance for sex-biased mental disorders emerging in youth. By establishing the developmental dynamism, spatial heterochonicity, and sexual dimorphism of human subcortical maturation, these data bring our spatiotemporal understanding of subcortical development closer to that of the cortex--allowing evolutionary, basic, and clinical neuroscience to be conducted within a more comprehensive developmental framework. PMID:24474784
A four-dimensional snapshot hyperspectral video-endoscope for bio-imaging applications
NASA Astrophysics Data System (ADS)
Lim, Hoong-Ta; Murukeshan, Vadakke Matham
2016-04-01
Hyperspectral imaging has proven significance in bio-imaging applications and it has the ability to capture up to several hundred images of different wavelengths offering relevant spectral signatures. To use hyperspectral imaging for in vivo monitoring and diagnosis of the internal body cavities, a snapshot hyperspectral video-endoscope is required. However, such reported systems provide only about 50 wavelengths. We have developed a four-dimensional snapshot hyperspectral video-endoscope with a spectral range of 400–1000 nm, which can detect 756 wavelengths for imaging, significantly more than such systems. Capturing the three-dimensional datacube sequentially gives the fourth dimension. All these are achieved through a flexible two-dimensional to one-dimensional fiber bundle. The potential of this custom designed and fabricated compact biomedical probe is demonstrated by imaging phantom tissue samples in reflectance and fluorescence imaging modalities. It is envisaged that this novel concept and developed probe will contribute significantly towards diagnostic in vivo biomedical imaging in the near future.
Slow gantry rotation acquisition technique for on-board four-dimensional digital tomosynthesis
Maurer, Jacqueline; Pan Tinsu; Yin, Fang-Fang
2010-02-15
Purpose: Four-dimensional cone-beam computed tomography (4D CBCT) has been investigated for motion imaging in the radiotherapy treatment room. The drawbacks of 4D CBCT are long scan times and high imaging doses. The aims of this study were to develop and investigate a slow gantry rotation acquisition protocol for four-dimensional digital tomosynthesis (4D DTS) as a faster, lower dose alternative to 4D CBCT. Methods: This technique was implemented using an On-Board Imager kV imaging system (Varian Medical Systems, Palo Alto, CA) mounted on the gantry of a linear accelerator. The general procedure for 4D DTS imaging using slow gantry rotation acquisition consists of the following steps: (1) acquire projections over a limited gantry rotation angle in a single motion with constant frame rate and gantry rotation speed; (2) generate a respiratory signal and temporally match projection images with appropriate points from the respiratory signal; (3) use the respiratory signal to assign phases to each of the projection images; (4) sort projection images into phase bins; and (5) reconstruct phase images. Phantom studies were conducted to validate theoretically derived relationships between acquisition and respiratory parameters. Optimization of acquisition parameters was then conducted by simulating lung scans using patient data. Lung tumors with approximate volumes ranging from 0.12 to 1.53 cm{sup 3} were studied. Results: A protocol for slow gantry rotation 4D DTS was presented. Equations were derived to express relationships between acquisition parameters (frame rate, phase window, and angular intervals between projections), respiratory cycle durations, and resulting acquisition times and numbers of projections. The phantom studies validated the relationships, and the patient studies resulted in determinations of appropriate acquisition parameters. The phase window must be set according to clinical goals. For 10% phase windows, we found that appropriate frame rates
Lee, Louis; Ma, Yunzhi; Ye, Yinyu; Xing, Lei
2009-07-01
Four-dimensional computed tomography (4DCT) offers an extra dimension of 'time' on the three-dimensional patient model with which we can incorporate target motion in radiation treatment (RT) planning and delivery in various ways such as in the concept of internal target volume, in gated treatment or in target tracking. However, for all these methodologies, different phases are essentially considered as non-interconnected independent phases for the purpose of optimization, in other words, the 'time' dimension has yet to be incorporated explicitly in the optimization algorithm and fully exploited. In this note, we have formulated a new 4D inverse planning technique that treats all the phases in the 4DCT as one single entity in the optimization. The optimization is formulated as a quadratic problem for disciplined convex programming that enables the problem to be analyzed and solved efficiently. In the proof-of-principle examples illustrated, we show that the temporal information of the spatial relation of the target and organs at risk could be 'exchanged' amongst different phases so that an appropriate weighting of dose deposition could be allocated to each phase, thus enabling a treatment with a tight target margin and a full duty cycle otherwise not achievable by either of the aforementioned methodologies. Yet there are practical issues to be solved in the 4D RT planning and delivery. The 4D concept in the optimization we have formulated here does provide insight on how the 'time' dimension can be exploited in the 4D optimization process. PMID:19521008
A Four-Dimensional CT-Based Evaluation of Techniques for Gastric Irradiation
Geld, Ylanga G. van; Senan, Suresh; Soernsen de Koste, John R. van; Verbakel, Wilko F.A.R.; Slotman, Ben J.; Lagerwaard, Frank J.
2007-11-01
Purpose: To evaluate three-dimensional conformal (3D-CRT), intensity-modulated (IMRT) and respiration-gated radiotherapy (RGRT) techniques for gastric irradiation for target coverage and minimization of renal doses. All techniques were four-dimensional (4D)-CT based, incorporating the intrafractional mobility of the target volume and organs at risk (OAR). Methods and Materials: The stomach, duodenal C-loop, and OAR (kidneys, liver, and heart) were contoured in all 10 phases of planning 4D-CT scans for five patients who underwent abdominal radiotherapy. Planning target volumes (PTVs) encompassing all positions of the stomach (PTV{sub allphases}) were generated. Three respiratory phases for RGRT in inspiration and expiration were identified, and corresponding PTV{sub inspiration} and PTV{sub expiration} and OAR volumes were created. Landmark-based fields recommended for the Radiation Therapy Oncology Group (RTOG) 99-04 study protocol were simulated to assess PTV coverage. IMRT and 3D-CRT planning with and without additional RGRT planning were performed for all PTVs, and corresponding dose volume histograms were analyzed. Results: Use of landmark-based fields did not result in full geometric coverage of the PTV{sub allphases} in any patient. IMRT significantly reduced mean renal doses compared with 3D-CRT (15.0 Gy {+-} 0.9 Gy vs. 20.1 Gy {+-} 9.3 Gy and 16.6 Gy {+-} 1.5 Gy vs. 32.6 Gy {+-} 7.1 Gy for the left and right kidneys, respectively; p = 0.04). No significant increase in renal sparing was seen when adding RGRT to either 3D-CRT or IMRT. Tolerance doses to the other OAR were not exceeded. Conclusions: Individualized field margins are essential for gastric irradiation. IMRT plans significantly reduce renal doses, but the benefits of RGRT in gastric irradiation appear to be limited.
Complete classification of parallel Lorentz surfaces in four-dimensional neutral pseudosphere
NASA Astrophysics Data System (ADS)
Chen, Bang-Yen
2010-08-01
A Lorentz surface of an indefinite space form is called parallel if its second fundamental form is parallel with respect to the Van der Waerden-Bortolotti connection. Such surfaces are locally invariant under the reflection with respect to the normal space at each point. Parallel surfaces are important in geometry as well as in general relativity since extrinsic invariants of such surfaces do not change from point to point. Parallel Lorentz surfaces in four-dimensional (4D) Lorentzian space forms are classified by Chen and Van der Veken ["Complete classification of parallel surfaces in 4-dimensional Lorentz space forms," Tohoku Math. J. 61, 1 (2009)]. Recently, explicit classification of parallel Lorentz surfaces in the pseudo-Euclidean 4-space E24 and in the pseudohyperbolic 4-space H24(-1) are obtained recently by Chen et al. ["Complete classification of parallel Lorentzian surfaces in Lorentzian complex space forms," Int. J. Math. 21, 665 (2010); "Complete classification of parallel Lorentz surfaces in neutral pseudo hyperbolic 4-space," Cent. Eur. J. Math. 8, 706 (2010)], respectively. In this article, we completely classify the remaining case; namely, parallel Lorentz surfaces in 4D neutral pseudosphere S24(1). Our result states that there are 24 families of such surfaces in S24(1). Conversely, every parallel Lorentz surface in S24(1) is obtained from one of the 24 families. The main result indicates that there are major differences between Lorentz surfaces in the de Sitter 4-space dS4 and in the neutral pseudo 4-sphere S24.
A new global four-dimensional variational ocean data assimilation system and its application
NASA Astrophysics Data System (ADS)
Liu, Juan; Wang, Bin; Liu, Hailong; Yu, Yongqiang
2008-07-01
A four-dimensional variational data assimilation (4DVar) system of the LASG/IAP Climate Ocean Model, version 1.0 (LICOM1.0), named LICOM-3DVM, has been developed using the three-dimensional variational data assimilation of mapped observation (3DVM), a 4DVar method newly proposed in the past two years. Two experiments with 12-year model integrations were designed to validate it. One is the assimilation run, called ASSM, which incorporated the analyzed weekly sea surface temperature (SST) fields from Reynolds and Smith (OISST) between 1990 and 2001 once a week by the LICOM-3DVM. The other is the control run without any assimilation, named CTL. ASSM shows that the simulated temperatures of the upper ocean (above 50 meters), especially the SST of equatorial Pacific, coincide with the Tropic Atmosphere Ocean (TAO) mooring data, the World Ocean Atlas 2001 (WOA01) data and the Met Office Hadley Centre’s sea ice and sea surface temperature (HadISST) data. It decreased the cold bias existing in CTL in the eastern Pacific and produced a Niño index that agrees with observation well. The validation results suggest that the LICOM-3DVM is able to effectively adjust the model results of the ocean temperature, although it’s hard to correct the subsurface results and it even makes them worse in some areas due to the incorporation of only surface data. Future development of the LICOM-3DVM is to include subsurface in situ observations and satellite observations to further improve model simulations.
Robust principal component analysis-based four-dimensional computed tomography
NASA Astrophysics Data System (ADS)
Gao, Hao; Cai, Jian-Feng; Shen, Zuowei; Zhao, Hongkai
2011-06-01
The purpose of this paper for four-dimensional (4D) computed tomography (CT) is threefold. (1) A new spatiotemporal model is presented from the matrix perspective with the row dimension in space and the column dimension in time, namely the robust PCA (principal component analysis)-based 4D CT model. That is, instead of viewing the 4D object as a temporal collection of three-dimensional (3D) images and looking for local coherence in time or space independently, we perceive it as a mixture of low-rank matrix and sparse matrix to explore the maximum temporal coherence of the spatial structure among phases. Here the low-rank matrix corresponds to the 'background' or reference state, which is stationary over time or similar in structure; the sparse matrix stands for the 'motion' or time-varying component, e.g., heart motion in cardiac imaging, which is often either approximately sparse itself or can be sparsified in the proper basis. Besides 4D CT, this robust PCA-based 4D CT model should be applicable in other imaging problems for motion reduction or/and change detection with the least amount of data, such as multi-energy CT, cardiac MRI, and hyperspectral imaging. (2) A dynamic strategy for data acquisition, i.e. a temporally spiral scheme, is proposed that can potentially maintain similar reconstruction accuracy with far fewer projections of the data. The key point of this dynamic scheme is to reduce the total number of measurements, and hence the radiation dose, by acquiring complementary data in different phases while reducing redundant measurements of the common background structure. (3) An accurate, efficient, yet simple-to-implement algorithm based on the split Bregman method is developed for solving the model problem with sparse representation in tight frames.
Evaluation of Bogus Vortex Techniques with Four-Dimensional Variational Data Assimilation
NASA Technical Reports Server (NTRS)
Pu, Zhao-Xia; Braun, Scott A.
2000-01-01
The effectiveness of techniques for creating "bogus" vortices in numerical simulations of hurricanes is examined by using the Penn State/NCAR nonhydrostatic mesoscale model (MM5) and its adjoint system. A series of four-dimensional variational data assimilation (4-D VAR) experiments is conducted to generate an initial vortex for Hurricane Georges (1998) in the Atlantic Ocean by assimilating bogus sea-level pressure and surface wind information into the mesoscale numerical model. Several different strategies are tested for improving the vortex representation. The initial vortices produced by the 4-D VAR technique are able to reproduce many of the structural features of mature hurricanes. The vortices also result in significant improvements to the hurricane forecasts in terms of both intensity and track. In particular, with assimilation of only bogus sea-level pressure information, the response in the wind field is contained largely within the divergent component, with strong convergence leading to strong upward motion near the center. Although the intensity of the initial vortex seems to be well represented, a dramatic spin down of the storm occurs within the first 6 h of the forecast. With assimilation of bogus surface wind data only, an expected dominance of the rotational component of the wind field is generated, but the minimum pressure is adjusted inadequately compared to the actual hurricane minimum pressure. Only when both the bogus surface pressure and wind information are assimilated together does the model produce a vortex that represents the actual intensity of the hurricane and results in significant improvements to forecasts of both hurricane intensity and track.
Stewart, Richard S; Kiss, Ilona M; Wilkinson, Robert S
2014-01-01
Four-dimensional (4D) light imaging has been used to study behavior of small structures within motor nerve terminals of the thin transversus abdominis muscle of the garter snake. Raw data comprises time-lapse sequences of 3D z-stacks. Each stack contains 4-20 images acquired with epifluorescence optics at focal planes separated by 400-1,500 nm. Steps in the acquisition of image stacks, such as adjustment of focus, switching of excitation wavelengths, and operation of the digital camera, are automated as much as possible to maximize image rate and minimize tissue damage from light exposure. After acquisition, a set of image stacks is deconvolved to improve spatial resolution, converted to the desired 3D format, and used to create a 4D "movie" that is suitable for variety of computer-based analyses, depending upon the experimental data sought. One application is study of the dynamic behavior of two classes of endosomes found in nerve terminals-macroendosomes (MEs) and acidic endosomes (AEs)-whose sizes (200-800 nm for both types) are at or near the diffraction limit. Access to 3D information at each time point provides several advantages over conventional time-lapse imaging. In particular, size and velocity of movement of structures can be quantified over time without loss of sharp focus. Examples of data from 4D imaging reveal that MEs approach the plasma membrane and disappear, suggesting that they are exocytosed rather than simply moving vertically away from a single plane of focus. Also revealed is putative fusion of MEs and AEs, by visualization of overlap between the two dye-containing structures as viewed in each three orthogonal projections. PMID:24799002
Impact of four-dimensional data assimilation (FDDA) on urban climate analysis
NASA Astrophysics Data System (ADS)
Pan, Linlin; Liu, Yubao; Liu, Yuewei; Li, Lei; Jiang, Yin; Cheng, Will; Roux, Gregory
2015-12-01
This study investigates the impact of four-dimensional data assimilation (FDDA) on urban climate analysis, which employs the NCAR (National Center for Atmospheric Research) WRF (the weather research and forecasting model) based on climate FDDA (CFDDA) technology to develop an urban-scale microclimatology database for the Shenzhen area, a rapidly developing metropolitan located along the southern coast of China, where uniquely high-density observations, including ultrahigh-resolution surface AWS (automatic weather station) network, radio sounding, wind profilers, radiometers, and other weather observation platforms, have been installed. CFDDA is an innovative dynamical downscaling regional climate analysis system that assimilates diverse regional observations; and has been employed to produce a 5 year multiscale high-resolution microclimate analysis by assimilating high-density observations at Shenzhen area. The CFDDA system was configured with four nested-grid domains at grid sizes of 27, 9, 3, and 1 km, respectively. This research evaluates the impact of assimilating high-resolution observation data on reproducing the refining features of urban-scale circulations. Two experiments were conducted with a 5 year run using CFSR (climate forecast system reanalysis) as boundary and initial conditions: one with CFDDA and the other without. The comparisons of these two experiments with observations indicate that CFDDA greatly reduces the model analysis error and is able to realistically analyze the microscale features such as urban-rural-coastal circulation, land/sea breezes, and local-hilly terrain thermal circulations. It is demonstrated that the urbanization can produce 2.5 k differences in 2 m temperatures, delays/speeds up the land/sea breeze development, and interacts with local mountain-valley circulations.
NASA Astrophysics Data System (ADS)
Elbern, H.; Schwinger, J.; Botchorishvili, R.
2010-03-01
A novel stratospheric chemical data assimilation system has been developed and applied to Environmental Satellite Michelson Interferometer for Passive Atmospheric Sounding (ENVISAT/MIPAS) data, aiming to combine the sophistication of the four-dimensional variational (4D-var) technique with flow-dependent covariance modeling and also to improve numerical performance. The system is tailored for operational stratospheric chemistry state monitoring. The atmospheric model of the assimilation system includes a state-of-the-art stratospheric chemistry transport module along with its adjoint and the German weather service's global meteorological forecast model, providing meteorological parameters. Both models share the same grid and same advection time step, to ensure dynamic consistency without spatial and temporal interpolation errors. A notable numerical efficiency gain is obtained through an icosahedral grid. As a novel feature in stratospheric variational data assimilation a special focus was placed on an optimal spatial exploitation of satellite data by dynamic formulation of the forecast error covariance matrix, providing potential vorticity controlled anisotropic and inhomogeneous influence radii. In this first part of the study the design and numerical features of the data assimilation system is presented, along with analyses of two case studies and a posteriori validation. Assimilated data include retrievals of O3, CH4, N2O, NO2, HNO3, and water vapor. The analyses are compared with independent observations provided by Stratospheric Aerosol and Gas Experiment II (SAGE II) and Halogen Occultation Experiment (HALOE) retrievals. It was found that there are marked improvements for both analyses and assimilation based forecasts when compared with control model runs without any data ingestion.
Robust principal component analysis-based four-dimensional computed tomography
Gao, Hao; Cai, Jian-Feng; Shen, Zuowei; Zhao, Hongkai
2012-01-01
The purpose of this paper for four-dimensional (4D) computed tomography (CT) is threefold. (1) A new spatiotemporal model is presented from the matrix perspective with the row dimension in space and the column dimension in time, namely the robust PCA (principal component analysis)-based 4D CT model. That is, instead of viewing the 4D object as a temporal collection of three-dimensional (3D) images and looking for local coherence in time or space independently, we perceive it as a mixture of low-rank matrix and sparse matrix to explore the maximum temporal coherence of the spatial structure among phases. Here the low-rank matrix corresponds to the ‘background’ or reference state, which is stationary over time or similar in structure; the sparse matrix stands for the ‘motion’ or time-varying component, e.g., heart motion in cardiac imaging, which is often either approximately sparse itself or can be sparsified in the proper basis. Besides 4D CT, this robust PCA-based 4D CT model should be applicable in other imaging problems for motion reduction or/and change detection with the least amount of data, such as multi-energy CT, cardiac MRI, and hyperspectral imaging. (2) A dynamic strategy for data acquisition, i.e. a temporally spiral scheme, is proposed that can potentially maintain similar reconstruction accuracy with far fewer projections of the data. The key point of this dynamic scheme is to reduce the total number of measurements, and hence the radiation dose, by acquiring complementary data in different phases while reducing redundant measurements of the common background structure. (3) An accurate, efficient, yet simple-to-implement algorithm based on the split Bregman method is developed for solving the model problem with sparse representation in tight frames. PMID:21540490
Four-dimensional computed tomography and detection of dynamic capitate subluxation.
Repse, Stephen E; Amis, Benjamin; Troupis, John M
2015-06-01
Midcarpal instability syndrome is often misdiagnosed, leading to delayed recognition, treatment and possibly poor clinical outcome. Four-dimensional computed tomography (4D CT) has previously proved useful in assessment of the acromioclavicular joint and wrist motion, allowing clinicians and radiologists to gain an understanding of abnormalities in function as well as morphology, which often contribute to patient symptoms. We present the case of a 25-year-old male with no history of trauma who presents with several months of a right wrist clunk on both passive and active (load bearing) motion. Plain film and 1.5 Tesla MRI with intra-articular contrast demonstrates a normal appearance, without joint space, tendon or ligament disturbance. We further investigated this condition using a wide volume detector CT scanning technique (4D CT). Data from the patient's asymptomatic wrist was utilized as a comparison for this study. Assessment of cine movie files from the symptomatic wrist revealed abnormal subluxation of the capitate from the lunate when compared with the normal wrist, in which the capitate did not deviate from the concavity of the lunate and did not cross the perpendicular line from the superior pole of the lunate in any phase of motion, which we defined as capitate subluxation. 4D CT allows for detection of capitate subluxation in an earlier stage of disease progression, constituting earlier recognition and providing the opportunity for earlier treatment of the disease, potentially mitigating significant patient morbidity. We have been able to confidently identify capitate subluxation both visually (assessment of the sagittal RLC axis) and objectively (documentation of percent subluxation of the capitate beyond the superior pole of the lunate). We propose that 4D CT investigation of all functional carpal instability syndromes may be beneficial as this technique has the potential to significantly increase our knowledge of dynamic carpal bone abnormalities
Novel Assessment of Renal Motion in Children as Measured via Four-Dimensional Computed Tomography
Pai Panandiker, Atmaram S.; Sharma, Shelly; Naik, Mihir H.; Wu, Shengjie; Hua, Chiaho; Beltran, Chris; Krasin, Matthew J.; Merchant, Thomas E.
2012-04-01
Objectives: Abdominal intensity-modulated radiation therapy and proton therapy require quantification of target and organ motion to optimize localization and treatment. Although addressed in adults, there is no available literature on this issue in pediatric patients. We assessed physiologic renal motion in pediatric patients. Methods and Materials: Twenty free-breathing pediatric patients at a median age of 8 years (range, 2-18 years) with intra-abdominal tumors underwent computed tomography simulation and four-dimensional computed tomography acquisition (slice thickness, 3 mm). Kidneys and diaphragms were contoured during eight phases of respiration to estimate center-of-mass motion. We quantified center of kidney mass mobility vectors in three dimensions: anteroposterior (AP), mediolateral (ML), and superoinferior (SI). Results: Kidney motion decreases linearly with decreasing age and height. The 95% confidence interval for the averaged minima and maxima of renal motion in children younger than 9 years was 5-9 mm in the ML direction, 4-11 mm in the AP direction, and 12-25 mm in the SI dimension for both kidneys. In children older than 9 years, the same confidence interval reveals a widening range of motion that was 5-16 mm in the ML direction, 6-17 mm in the AP direction, and 21-52 mm in the SI direction. Although not statistically significant, renal motion correlated with diaphragm motion in older patients. The correlation between diaphragm motion and body mass index was borderline (r = 0.52, p = 0.0816) in younger patients. Conclusions: Renal motion is age and height dependent. Measuring diaphragmatic motion alone does not reliably quantify pediatric renal motion. Renal motion in young children ranges from 5 to 25 mm in orientation-specific directions. The vectors of motion range from 5 to 52 mm in older children. These preliminary data represent novel analyses of pediatric intra-abdominal organ motion.
NASA Astrophysics Data System (ADS)
Saito, A.; Akiya, Y.; Yoshida, D.; Odagi, Y.; Yoshikawa, M.; Tsugawa, T.; Takahashi, M.; Kumano, Y.; Iwasaki, S.
2010-12-01
We have developed a four-dimensional display system of the Earth and planets to use in schools, science centers, and research institutes. It can display the Earth and planets in three-dimensional way without glasses, and the time variation of the scientific data can be displayed on the Earth and planets image. The system is named Dagik Earth, and educational programs using Dagik Earth have been developed for schools and science centers. Three dimensional displays can show the Earth and planets in exact form without any distortion, which cannot be achieved with two-dimensional display. Furthermore it can provide a sense of reality. There are several systems for the three-dimensional presentation of the Earth, such as Science on a sphere by NOAA, and Geocosmos by Miraikan, Japan. Comparing these systems, the advantage of Dagik Earth is portability and affordability. The system uses ordinary PC and PC projector. Only a spherical screen is the special equipment of Dagik Earth. Therefore Dagik Earth is easy to use in classrooms. Several educational programs have been developed and carried out in high schools, junior high schools, elementary schools and science centers. Several research institutes have used Dagik Earth in their public outreach programs to demonstrate their novel scientific results to public in an attractive way of presentation. A community of users and developers of Dagik Earth is being formed in Japan. In the presentation, the outline of Dagik Earth and the educational programs using Dagik Earth will be presented. Its future plan will also be discussed.
A quantitative evaluation study of four-dimensional gated cardiac SPECT reconstruction.
Jin, Mingwu; Yang, Yongyi; Niu, Xiaofeng; Marin, Thibault; Brankov, Jovan G; Feng, Bing; Pretorius, P Hendrik; King, Michael A; Wernick, Miles N
2009-09-21
In practice, gated cardiac SPECT images suffer from a number of degrading factors, including distance-dependent blur, attenuation, scatter and increased noise due to gating. Recently, we proposed a motion-compensated approach for four-dimensional (4D) reconstruction for gated cardiac SPECT and demonstrated that use of motion-compensated temporal smoothing could be effective for suppressing the increased noise due to lowered counts in individual gates. In this work, we further develop this motion-compensated 4D approach by also taking into account attenuation and scatter in the reconstruction process, which are two major degrading factors in SPECT data. In our experiments, we conducted a thorough quantitative evaluation of the proposed 4D method using Monte Carlo simulated SPECT imaging based on the 4D NURBS-based cardiac-torso (NCAT) phantom. In particular, we evaluated the accuracy of the reconstructed left ventricular myocardium using a number of quantitative measures including regional bias-variance analyses and wall intensity uniformity. The quantitative results demonstrate that use of motion-compensated 4D reconstruction can improve the accuracy of the reconstructed myocardium, which in turn can improve the detectability of perfusion defects. Moreover, our results reveal that while traditional spatial smoothing could be beneficial, its merit would become diminished with the use of motion-compensated temporal regularization. As a preliminary demonstration, we also tested our 4D approach on patient data. The reconstructed images from both simulated and patient data demonstrated that our 4D method can improve the definition of the LV wall. PMID:19724094
Michalski, Darek Sontag, Marc; Li Fang; Andrade, Regiane S. de; Uslene, Irmute; Brandner, Edward D.; Heron, Dwight E.; Yue Ning; Huq, M. Saiful
2008-07-01
Purpose: To evaluate the interfractional reproducibility of respiration-induced lung tumors motion, defined by their centroids and the intrafractional target motion range. Methods and Materials: Twentythree pairs of four-dimensional/computed tomography scans were acquired for 22 patients. Gross tumor volumes were contoured, Clinical target volumes (CTVs) were generated. Geometric data for CTVs and lung volumes were extracted. The motion tracks of CTV centroids, and CTV edges along the cranio-caudal, anterior-posterior, and lateral directions were evaluated. The Pearson correlation coefficient for motion tracks along the cranio-caudal direction was determined for the entire respiratory cycle and for five phases about the end of expiration. Results: The largest motion extent was along the cranio-caudal direction. The intrafractional motion extent for five CTVs was <0.5 cm, the largest motion range was 3.59 cm. Three CTVs with respiration-induced displacement >0.5 cm did not exhibit the similarity of motion, and for 16 CTVs with motion >0.5 cm the correlation coefficient was >0.8. The lung volumes in corresponding phases for cases that demonstrated CTVs motion similarity were reproducible. No correlation between tumor size and mobility was found. Conclusion: Target motion reproducibility seems to be present in 87% of cases in our dataset. Three cases with dissimilar motion indicate that it is advisable to verify target motion during treatment. The adaptive adjustment to compensate the possible interfractional shifts in a target position should be incorporated as a routine policy for lung cancer radiotherapy.
Robust principal component analysis-based four-dimensional computed tomography.
Gao, Hao; Cai, Jian-Feng; Shen, Zuowei; Zhao, Hongkai
2011-06-01
The purpose of this paper for four-dimensional (4D) computed tomography (CT) is threefold. (1) A new spatiotemporal model is presented from the matrix perspective with the row dimension in space and the column dimension in time, namely the robust PCA (principal component analysis)-based 4D CT model. That is, instead of viewing the 4D object as a temporal collection of three-dimensional (3D) images and looking for local coherence in time or space independently, we perceive it as a mixture of low-rank matrix and sparse matrix to explore the maximum temporal coherence of the spatial structure among phases. Here the low-rank matrix corresponds to the 'background' or reference state, which is stationary over time or similar in structure; the sparse matrix stands for the 'motion' or time-varying component, e.g., heart motion in cardiac imaging, which is often either approximately sparse itself or can be sparsified in the proper basis. Besides 4D CT, this robust PCA-based 4D CT model should be applicable in other imaging problems for motion reduction or/and change detection with the least amount of data, such as multi-energy CT, cardiac MRI, and hyperspectral imaging. (2) A dynamic strategy for data acquisition, i.e. a temporally spiral scheme, is proposed that can potentially maintain similar reconstruction accuracy with far fewer projections of the data. The key point of this dynamic scheme is to reduce the total number of measurements, and hence the radiation dose, by acquiring complementary data in different phases while reducing redundant measurements of the common background structure. (3) An accurate, efficient, yet simple-to-implement algorithm based on the split Bregman method is developed for solving the model problem with sparse representation in tight frames. PMID:21540490
Chiral four-dimensional F-theory compactifications with SU(5) and multiple U(1)-factors
NASA Astrophysics Data System (ADS)
Cvetič, Mirjam; Grassi, Antonella; Klevers, Denis; Piragua, Hernan
2014-04-01
We develop geometric techniques to determine the spectrum and the chiral indices of matter multiplets for four-dimensional F-theory compactifications on elliptic Calabi-Yau fourfolds with rank two Mordell-Weil group. The general elliptic fiber is the Calabi-Yau onefold in dP 2. We classify its resolved elliptic fibrations over a general base B. The study of singularities of these fibrations leads to explicit matter representations, that we determine both for U(1) × U(1) and SU(5) × U(1) × U(1) constructions. We determine for the first time certain matter curves and surfaces using techniques involving prime ideals. The vertical cohomology ring of these fourfolds is calculated for both cases and general formulas for the Euler numbers are derived. Explicit calculations are presented for a specific base B = ℙ3. We determine the general G 4-flux that belongs to of the resolved Calabi-Yau fourfolds. As a by-product, we derive for the first time all conditions on G 4-flux in general F-theory compactifications with a non-holomorphic zero section. These conditions have to be formulated after a circle reduction in terms of Chern-Simons terms on the 3D Coulomb branch and invoke M-theory/F-theory duality. New Chern-Simons terms are generated by Kaluza-Klein states of the circle compactification. We explicitly perform the relevant field theory computations, that yield non-vanishing results precisely for fourfolds with a non-holomorphic zero section. Taking into account the new Chern-Simons terms, all 4D matter chiralities are determined via 3D M-theory/F-theory duality. We independently check these chiralities using the subset of matter surfaces we determined. The presented techniques are general and do not rely on toric data.
Do Human Fetuses Anticipate Self-Oriented Actions? A Study by Four-Dimensional (4D) Ultrasonography
ERIC Educational Resources Information Center
Myowa-Yamakoshi, Masako; Takeshita, Hideko
2006-01-01
Using four-dimensional (4D) ultrasonography, arm and hand movements toward the face were examined in 27 human fetuses at 19 to 35 weeks of gestation, thereby enabling the continuous monitoring of their faces and other surface features such as the extremities. More than half of the observed arm movements resulted in the hand touching the mouth…
Four-dimensional data assimilation applied to photochemical air quality modeling is used to suggest adjustments to the emissions inventory of the Atlanta, Georgia metropolitan area. In this approach, a three-dimensional air quality model, coupled with direct sensitivity analys...
O'Brien, Ricky T; Cooper, Benjamin J; Kipritidis, John; Shieh, Chun-Chien; Keall, Paul J
2014-02-01
Four dimensional cone beam computed tomography (4DCBCT) images suffer from angular under sampling and bunching of projections due to a lack of feedback between the respiratory signal and the acquisition system. To address this problem, respiratory motion guided 4DCBCT (RMG-4DCBCT) regulates the gantry velocity and projection time interval, in response to the patient's respiratory signal, with the aim of acquiring evenly spaced projections in a number of phase or displacement bins during the respiratory cycle. Our previous study of RMG-4DCBCT was limited to sinusoidal breathing traces. Here we expand on that work to provide a practical algorithm for the case of real patient breathing data. We give a complete description of RMG-4DCBCT including full details on how to implement the algorithms to determine when to move the gantry and when to acquire projections in response to the patient's respiratory signal. We simulate a realistic working RMG-4DCBCT system using 112 breathing traces from 24 lung cancer patients. Acquisition used phase-based binning and parameter settings typically used on commercial 4DCBCT systems (4 min acquisition time, 1200 projections across 10 respiratory bins), with the acceleration and velocity constraints of current generation linear accelerators. We quantified streaking artefacts and image noise for conventional and RMG-4DCBCT methods by reconstructing projection data selected from an oversampled set of Catphan phantom projections. RMG-4DCBCT allows us to optimally trade-off image quality, acquisition time and image dose. For example, for the same image quality and acquisition time as conventional 4DCBCT approximately half the imaging dose is needed. Alternatively, for the same imaging dose, the image quality as measured by the signal to noise ratio, is improved by 63% on average. C-arm cone beam computed tomography systems, with an acceleration up to 200°/s(2), a velocity up to 100°/s and the acquisition of 80 projections per second
High-quality four-dimensional cone-beam CT by deforming prior images
NASA Astrophysics Data System (ADS)
Wang, Jing; Gu, Xuejun
2013-01-01
Due to a limited number of projections at each phase, severe view aliasing artifacts are present in four-dimensional cone beam computed tomography (4D-CBCT) when reconstruction is performed using conventional algorithms. In this work, we aim to obtain high-quality 4D-CBCT of lung cancer patients in radiation therapy by deforming the planning CT. The deformation vector fields (DVF) to deform the planning CT are estimated through matching the forward projection of the deformed prior image and measured on-treatment CBCT projection. The estimation of the DVF is formulated as an unconstrained optimization problem, where the objective function to be minimized is the sum of the squared difference between the forward projection of the deformed planning CT and the measured 4D-CBCT projection. A nonlinear conjugate gradient method is used to solve the DVF. As the number of the variables in the DVF is much greater than the number of measurements, the solution to such a highly ill-posed problem is very sensitive to the initials during the optimization process. To improve the estimation accuracy of DVF, we proposed a new strategy to obtain better initials for the optimization. In this strategy, 4D-CBCT is first reconstructed by total variation minimization. Demons deformable registration is performed to register the planning CT and the 4D-CBCT reconstructed by total variation minimization. The resulted DVF from demons registration is then used as the initial parameters in the optimization process. A 4D nonuniform rotational B-spline-based cardiac-torso (NCAT) phantom and a patient 4D-CBCT are used to evaluate the algorithm. Image quality of 4D-CBCT is substantially improved by using the proposed strategy in both NCAT phantom and patient studies. The proposed method has the potential to improve the temporal resolution of 4D-CBCT. Improved 4D-CBCT can better characterize the motion of lung tumors and will be a valuable tool for image-guided adaptive radiation therapy.
Underberg, Rene; Lagerwaard, Frank J. . E-mail: fj.lagerwaard@vumc.nl; Cuijpers, Johan P.; Slotman, Ben J.; van Soernsen de Koste, John R.; Senan, Suresh
2004-11-15
Purpose: Hypofractionated stereotactic radiotherapy (SRT) for Stage I non-small-cell lung cancer requires that meticulous attention be paid toward ensuring optimal target definition. Two computed tomography (CT) scan techniques for defining internal target volumes (ITV) were evaluated. Methods and materials: Ten consecutive patients treated with SRT underwent six 'standard' rapid multislice CT scans to generate an ITV{sub 6CT} and one four-dimensional CT (4DCT) scan that generated volumetric datasets for 10 phases of the respiratory cycle, all of which were used to generate an ITV{sub 4DCT}. Geometric and dosimetric analyses were performed for (1) PTV{sub 4DCT}, derived from the ITV{sub 4DCT} with the addition of a 3-mm margin; (2) PTV{sub 6CT}, derived from the ITV{sub 6CT} with the addition of a 3-mm margin; and (3) 6 PTV{sub 10mm}, derived from each separate GTV{sub 6CT}, to which a three-dimensional margin of 10 mm was added. Results: The ITV{sub 4DCT} was not significantly different from the ITV{sub 6CT} in 8 patients, but was considerably larger in 2 patients whose tumors exhibited the greatest mobility. On average, the ITV{sub 6CT} missed on average 22% of the volume encompassing both ITVs, in contrast to a corresponding mean value of only 8.3% for ITV{sub 4DCT}. Plans based on PTV{sub 4DCT} resulted in coverage of the PTV{sub 6CT} by the 80% isodose in all patients. However, plans based on use of PTV{sub 6CT} led to a mean PTV{sub 4DCT} coverage of only 92.5%, with a minimum of 77.7% and 77.5% for the two most mobile tumors. PTVs derived from a single multislice CT expanded with a margin of 10 mm were on average twice the size of PTVs derived using the other methods, but still led to an underdosing in the two most mobile tumors. Conclusions: Individualized ITVs can improve target definition for SRT of Stage I non-small-cell lung cancer, and use of only a single CT scan with a 10-mm margin is inappropriate. A single 4D scan generates comparable or larger
Target-specific optimization of four-dimensional cone beam computed tomography
Ahmad, Moiz; Pan Tinsu
2012-09-15
Purpose: Under-sampling artifacts are a major problem in four-dimensional cone-beam computed tomography (4D-CBCT) and may compromise evaluation of target motion. Several studies have addressed scan parameter selection for minimizing under-sampling artifacts; however, the role of the target characteristics in scan parameter selection has not been investigated. In this work, the authors evaluated 4D-CBCT performance by assessing the accuracy of target motion measurements for various target sizes and motions. The results may serve as patient-specific guidelines for scan parameters selection in 4D-CBCT. Methods: The authors acquired 4D-CBCT scans of a moving phantom consisting of six water-filled sphere targets of sizes 10-37 mm, using various scan times ranging from 30 s to 3 min., setting the motion to 3-s and 6-s periods. The authors used automatic image registration to extract the target motion trajectories and evaluated these measurements for various target sizes and motions over various combinations of scan parameters including scan time, detector configuration, number of respiration phases, and reconstruction filters. Results: The most important object parameter to 4D-CBCT performance was the period of motion. Measurements for the 6-s motion were always systematically less accurate than measurements for the 3-s motion for 34 of 36 objects of various sizes and periods of motion. The 6-s motion required a greater scan time than the 3-s motion for equivalent measurement accuracy. The second most influential parameter was the target size. For the 3-s period of motion, objects larger than 13 mm were tracked with sub-millimeter accuracy with a 1-min scan time. For the 6-s period of motion, objects larger than 22-mm were tracked with sub-millimeter accuracy with a 1.5-min scan time. For all sizes and motions, temporal blurring was observed when the number of phases was fewer than 8. Offset detector configuration provided the same performance as centered detector except
Interfractional Reproducibility in Pancreatic Position Based on Four-Dimensional Computed Tomography
Shiinoki, Takehiro; Shibuya, Keiko; Nakamura, Mitsuhiro; Nakamura, Akira; Matsuo, Yukinori; Nakata, Manabu; Sawada, Akira; Mizowaki, Takashi; Itoh, Akio; Hiraoka, Masahiro
2011-08-01
Purpose: To assess the interfractional positional variation of the pancreas using four-dimensional computed tomography (4D-CT) and to determine the suitable phase of respiration for dose delivery methods to account for pancreatic tumor motion. Methods and Materials: Fifteen patients with pancreatic cancer were enrolled in this study. For each patient, 4D-CT scans were performed at CT simulation and three times during the course of treatment. Regions of interest were set to the intrapancreatic bile ducts as a surrogate for pancreatic position. The centroids of the regions of interest were calculated at end-inhalation and end-exhalation of the respiration phase. The ranges of respiratory motion and interfractional positional variation were evaluated in the left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions. Results: The medians of respiratory motion were 1.1 mm (range, 0.0-9.8 mm), 1.5 mm (range, 0.0-7.0 mm), and 5.0 mm (range, 0.0-12.5 mm) in the LR, AP, and SI directions, respectively. The means {+-} SDs of the interfractional positional variation at end-inhalation were 0.9 {+-} 5.1 mm (range, -9.2 to 15.6 mm), -1.9 {+-} 3.9 mm (range, -12.8 to 6.4 mm), and -1.3 {+-} 6.9 mm (range, -15.0 to 13.7 mm) and those at end-exhalation were 0.0 {+-} 3.1 mm (range, -7.0 to 5.3 mm), -1.2 {+-} 3.9 mm (range, -11.2 to 6.7 mm), and 0.1 {+-} 3.2 mm (range, -9.9 to 5.1 mm) in the LR, AP, and SI directions, respectively. The SDs of the interfractional positional variation in the LR and SI directions were significantly larger at end-inhalation than at end-exhalation (LR, p < 0.001; SI, p < 0.001). Conclusions: The ranges of respiratory motion during the course of treatment and the interfractional positional variation were not negligible. The interfractional positional reproducibility was higher at end-exhalation than at end-inhalation under free breathing.
GPU-based four-dimensional general-relativistic ray tracing
NASA Astrophysics Data System (ADS)
Kuchelmeister, Daniel; Müller, Thomas; Ament, Marco; Wunner, Günter; Weiskopf, Daniel
2012-10-01
This paper presents a new general-relativistic ray tracer that enables image synthesis on an interactive basis by exploiting the performance of graphics processing units (GPUs). The application is capable of visualizing the distortion of the stellar background as well as trajectories of moving astronomical objects orbiting a compact mass. Its source code includes metric definitions for the Schwarzschild and Kerr spacetimes that can be easily extended to other metric definitions, relying on its object-oriented design. The basic functionality features a scene description interface based on the scripting language Lua, real-time image output, and the ability to edit almost every parameter at runtime. The ray tracing code itself is implemented for parallel execution on the GPU using NVidia's Compute Unified Device Architecture (CUDA), which leads to performance improvement of an order of magnitude compared to a single CPU and makes the application competitive with small CPU cluster architectures. Program summary Program title: GpuRay4D Catalog identifier: AEMV_v1_0 Program summary URL: http://cpc.cs.qub.ac.uk/summaries/AEMV_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 73649 No. of bytes in distributed program, including test data, etc.: 1334251 Distribution format: tar.gz Programming language: C++, CUDA. Computer: Linux platforms with a NVidia CUDA enabled GPU (Compute Capability 1.3 or higher), C++ compiler, NVCC (The CUDA Compiler Driver). Operating system: Linux. RAM: 2 GB Classification: 1.5. External routines: OpenGL Utility Toolkit development files, NVidia CUDA Toolkit 3.2, Lua5.2 Nature of problem: Ray tracing in four-dimensional Lorentzian spacetimes. Solution method: Numerical integration of light rays, GPU-based parallel programming using CUDA, 3D
Four dimensional variational assimilation of in-situ and remote-sensing aerosol data
NASA Astrophysics Data System (ADS)
Nieradzik, L. P.; Elbern, H.
2012-04-01
Aerosols play an increasingly important role in atmospheric modelling. They have a strong influence on the radiative transfer balance and a significant impact on human health. Their origin is various and so are its effects. Most of the measurement sites in Europe account for an integrated aerosol load PMx (Particulate Matter of less than x μm in diameter) which does not give any qualitative information on the composition of the aerosol. Since very different constituents contribute to PMx, like e.g. mineral dust derived from desert storms or sea salt, it is necessary to make aerosol forecasts not only of load, but also type resolved. The method of four dimensional variational data assimilation (4Dvar) is a widely known technique to enhance forecast skills of CTMs (Chemistry-Transport-Models) by ingesting in-situ and, especially, remote-sensing measurements. The EURAD-IM (EURopean Air pollution Dispersion - Inverse Model), containing a full adjoint gas-phase model, has been expanded with an adjoint of the MADE (Modal Aerosol Dynamics model for Europe) to optimise initial and boundary values for aerosols using 4Dvar. A forward and an adjoint radiative transfer model is driven by the EURAD-IM as mapping between BLAOT (Boundary Layer Aerosol Optical Thickness) and internal aerosol species. Furthermore, its condensation scheme has been bypassed by an HDMR (High-Dimensional-Model-Representation) to ensure differentiability. In this study both in-situ measured PMx as well as satellite retrieved aerosol optical thicknesses have been assimilated and the effect on forecast performance has been investigated. The source of BLAOT is the aerosol retrieval system SYNAER (SYNergetic AErosol Retrieval) from DLR-DFD that retrieves AOT by making use of both AATSR/SCIAMACHY and AVHRR/GOME-2 data respectively. Its strengths are a large spatial coverage, near real-time availability, and the classification of five intrinsic aerosol species, namely water-solubles, water-insolubles, soot
Improved and Robust Detection of Cell Nuclei from Four Dimensional Fluorescence Images
Bashar, Md. Khayrul; Yamagata, Kazuo; Kobayashi, Tetsuya J.
2014-01-01
Segmentation-free direct methods are quite efficient for automated nuclei extraction from high dimensional images. A few such methods do exist but most of them do not ensure algorithmic robustness to parameter and noise variations. In this research, we propose a method based on multiscale adaptive filtering for efficient and robust detection of nuclei centroids from four dimensional (4D) fluorescence images. A temporal feedback mechanism is employed between the enhancement and the initial detection steps of a typical direct method. We estimate the minimum and maximum nuclei diameters from the previous frame and feed back them as filter lengths for multiscale enhancement of the current frame. A radial intensity-gradient function is optimized at positions of initial centroids to estimate all nuclei diameters. This procedure continues for processing subsequent images in the sequence. Above mechanism thus ensures proper enhancement by automated estimation of major parameters. This brings robustness and safeguards the system against additive noises and effects from wrong parameters. Later, the method and its single-scale variant are simplified for further reduction of parameters. The proposed method is then extended for nuclei volume segmentation. The same optimization technique is applied to final centroid positions of the enhanced image and the estimated diameters are projected onto the binary candidate regions to segment nuclei volumes.Our method is finally integrated with a simple sequential tracking approach to establish nuclear trajectories in the 4D space. Experimental evaluations with five image-sequences (each having 271 3D sequential images) corresponding to five different mouse embryos show promising performances of our methods in terms of nuclear detection, segmentation, and tracking. A detail analysis with a sub-sequence of 101 3D images from an embryo reveals that the proposed method can improve the nuclei detection accuracy by 9 over the previous methods
Park, Justin C.; Kim, Jin Sung; Park, Sung Ho; Webster, Matthew J.; Lee, Soyoung; Song, William Y.; Han, Youngyih
2014-01-01
Purpose To evaluate respiratory motion of a patient by generating four-dimensional digital tomosynthesis (4D DTS), extracting respiratory signal from patients' on-board projection data, and ensuring the feasibility of 4D DTS as a localization tool for the targets which have respiratory movement. Methods and Materials Four patients with lung and liver cancer were included to verify the feasibility of 4D-DTS with an on-board imager. CBCT acquisition (650–670 projections) was used to reconstruct 4D DTS images and the breath signal of the patients was generated by extracting the motion of diaphragm during data acquisition. Based on the extracted signal, the projection data was divided into four phases: peak-exhale phase, mid-inhale phase, peak-inhale phase, and mid-exhale phase. The binned projection data was then used to generate 4D DTS, where the total scan angle was assigned as ±22.5° from rotation center, centered on 0° and 180° for coronal “half-fan” 4D DTS, and 90° and 270° for sagittal “half-fan” 4D DTS. The result was then compared with 4D CBCT which we have also generated with the same phase distribution. Results The motion of the diaphragm was evident from the 4D DTS results for peak-exhale, mid-inhale, peak-inhale and mid-exhale phase assignment which was absent in 3D DTS. Compared to the result of 4D CBCT, the view aliasing effect due to arbitrary angle reconstruction was less severe. In addition, the severity of metal artifacts, the image distortion due to presence of metal, was less than that of the 4D CBCT results. Conclusion We have implemented on-board 4D DTS on patients data to visualize the movement of anatomy due to respiratory motion. The results indicate that 4D-DTS could be a promising alternative to 4D CBCT for acquiring the respiratory motion of internal organs just prior to radiotherapy treatment. PMID:25541710
Impact of motion velocity on four-dimensional target volumes: a phantom study.
Nakamura, Mitsuhiro; Narita, Yuichiro; Sawada, Akira; Matsugi, Kiyotomo; Nakata, Manabu; Matsuo, Yukinori; Mizowaki, Takashi; Hiraoka, Masahiro
2009-05-01
This study aims to assess the impact of motion velocity that may cause motion artifacts on target volumes (TVs) using a one-dimensional moving phantom. A 20 mm diameter spherical object embedded in a QUASAR phantom sinusoidally moved with approximately 5.0 or 10.0 mm amplitude (A) along the longitudinal axis of the computed tomography (CT) couch. The motion period was manually set in the range of 2.0-10.0 s at approximately 2.0 s interval. Four-dimensional (4D) CT images were acquired by a four-slice CT scanner (LightSpeed RT; General Electric Medical Systems, Waukesha, WI) with a slice thickness of 1.25 mm in axial cine mode. The minimum gantry rotation of 1.0 s was employed to achieve the maximum in-slice temporal resolution. Projection data over a full gantry rotation (1.0 s) were used for image reconstruction. Reflective marker position was recorded by the real-time positioning management system (Varian Medical Systems, Palo Alto, CA). ADVANTAGE 4D software exported ten respiratory phase volumes and the maximum intensity volume generated from all reconstructed data (MIV). The threshold to obtain static object volume (V0, 4.19 ml) was used to automatically segment TVs on CT images, and then the union of TVs on 4D CT images (TV(4D)) was constructed. TVs on MIV (TV(MIV)) were also segmented by the threshold that can determine the area occupied within the central slice of TV(MIV). The maximum motion velocity for each phase bin was calculated using the actual averaged motion period displayed on ADVANTAGE 4D software (T), the range of phases used to construct the target phase bin (phase range), and a mathematical model of sinusoidal function. Each volume size and the motion range of TV in the cranial-caudal (CC) direction were measured. Subsequently, cross-correlation coefficients between TV size and motion velocity as well as phase range were calculated. Both misalignment and motion-blurring artifacts were caused by high motion velocity, Less than 6% phase range was
Four-dimensional cone beam CT reconstruction and enhancement using a temporal nonlocal means method
Jia Xun; Tian Zhen; Lou Yifei; Sonke, Jan-Jakob; Jiang, Steve B.
2012-09-15
Purpose: Four-dimensional cone beam computed tomography (4D-CBCT) has been developed to provide respiratory phase-resolved volumetric imaging in image guided radiation therapy. Conventionally, it is reconstructed by first sorting the x-ray projections into multiple respiratory phase bins according to a breathing signal extracted either from the projection images or some external surrogates, and then reconstructing a 3D CBCT image in each phase bin independently using FDK algorithm. This method requires adequate number of projections for each phase, which can be achieved using a low gantry rotation or multiple gantry rotations. Inadequate number of projections in each phase bin results in low quality 4D-CBCT images with obvious streaking artifacts. 4D-CBCT images at different breathing phases share a lot of redundant information, because they represent the same anatomy captured at slightly different temporal points. Taking this redundancy along the temporal dimension into account can in principle facilitate the reconstruction in the situation of inadequate number of projection images. In this work, the authors propose two novel 4D-CBCT algorithms: an iterative reconstruction algorithm and an enhancement algorithm, utilizing a temporal nonlocal means (TNLM) method. Methods: The authors define a TNLM energy term for a given set of 4D-CBCT images. Minimization of this term favors those 4D-CBCT images such that any anatomical features at one spatial point at one phase can be found in a nearby spatial point at neighboring phases. 4D-CBCT reconstruction is achieved by minimizing a total energy containing a data fidelity term and the TNLM energy term. As for the image enhancement, 4D-CBCT images generated by the FDK algorithm are enhanced by minimizing the TNLM function while keeping the enhanced images close to the FDK results. A forward-backward splitting algorithm and a Gauss-Jacobi iteration method are employed to solve the problems. The algorithms implementation on
Liu, Yilin; Yin, Fang-Fang; Cai, Jing; Chen, Nan-kuei; Chu, Mei-Lan
2015-02-15
Purpose: Current four dimensional magnetic resonance imaging (4D-MRI) techniques lack sufficient temporal/spatial resolution and consistent tumor contrast. To overcome these limitations, this study presents the development and initial evaluation of a new strategy for 4D-MRI which is based on retrospective k-space reordering. Methods: We simulated a k-space reordered 4D-MRI on a 4D digital extended cardiac-torso (XCAT) human phantom. A 2D echo planar imaging MRI sequence [frame rate (F) = 0.448 Hz; image resolution (R) = 256 × 256; number of k-space segments (N{sub KS}) = 4] with sequential image acquisition mode was assumed for the simulation. Image quality of the simulated “4D-MRI” acquired from the XCAT phantom was qualitatively evaluated, and tumor motion trajectories were compared to input signals. In particular, mean absolute amplitude differences (D) and cross correlation coefficients (CC) were calculated. Furthermore, to evaluate the data sufficient condition for the new 4D-MRI technique, a comprehensive simulation study was performed using 30 cancer patients’ respiratory profiles to study the relationships between data completeness (C{sub p}) and a number of impacting factors: the number of repeated scans (N{sub R}), number of slices (N{sub S}), number of respiratory phase bins (N{sub P}), N{sub KS}, F, R, and initial respiratory phase at image acquisition (P{sub 0}). As a proof-of-concept, we implemented the proposed k-space reordering 4D-MRI technique on a T2-weighted fast spin echo MR sequence and tested it on a healthy volunteer. Results: The simulated 4D-MRI acquired from the XCAT phantom matched closely to the original XCAT images. Tumor motion trajectories measured from the simulated 4D-MRI matched well with input signals (D = 0.83 and 0.83 mm, and CC = 0.998 and 0.992 in superior–inferior and anterior–posterior directions, respectively). The relationship between C{sub p} and N{sub R} was found best represented by an exponential function
Four-dimensional optical multiband-OFDM for beyond 1.4 Tb/s serial optical transmission.
Djordjevic, Ivan; Batshon, Hussam G; Xu, Lei; Wang, Ting
2011-01-17
We propose a four-dimensional (4D) coded multiband-OFDM scheme suitable for beyond 1.4 Tb/s serial optical transport. The proposed scheme organizes the N-dimensional (ND) signal constellation points in the form of signal matrix; employs 2D-inverse FFT and 2D-FFT to perform modulation and demodulation, respectively; and exploits both orthogonal polarizations. This scheme can fully exploit advantages of OFDM to deal with chromatic dispersion, PMD and PDL effects; and multidimensional signal constellations to improve OSNR sensitivity of conventional optical OFDM. The improvement of 4D-OFDM over corresponding polarization-multiplexed QAM (with the same number of constellation points) ranges from 1.79 dB for 16 signal constellation point-four-dimensional-OFDM (16-4D-OFDM) up to 4.53 dB for 128-4D-OFDM. PMID:21263627
NASA Technical Reports Server (NTRS)
Makivic, Miloje S.
1996-01-01
This is the final technical report for the project entitled: "High-Performance Computing and Four-Dimensional Data Assimilation: The Impact on Future and Current Problems", funded at NPAC by the DAO at NASA/GSFC. First, the motivation for the project is given in the introductory section, followed by the executive summary of major accomplishments and the list of project-related publications. Detailed analysis and description of research results is given in subsequent chapters and in the Appendix.
Anciaux, Henri; Godoy, Yamile
2015-02-15
We give local, explicit representation formulas for n-dimensional spacelike submanifolds which are marginally trapped in the Minkowski space ℝ{sub 1}{sup n+2}, the de Sitter space dS{sup n+2}, the anti-de Sitter space AdS{sup n+2} and the Lorentzian products S{sup n+1} × ℝ and ℍ{sup n+1} × ℝ of the sphere and the hyperbolic space by the real line.
Ha, Hojin; Kim, Guk Bae; Kweon, Jihoon; Lee, Sang Joon; Kim, Young-Hak; Lee, Deok Hee
2016-01-01
Recent improvements have been made to the use of time-resolved, three-dimensional phase-contrast (PC) magnetic resonance imaging (MRI), which is also named four-dimensional (4D) PC-MRI or 4D flow MRI, in the investigation of spatial and temporal variations in hemodynamic features in cardiovascular blood flow. The present article reviews the principle and analytical procedures of 4D PC-MRI. Various fluid dynamic biomarkers for possible clinical usage are also described, including wall shear stress, turbulent kinetic energy, and relative pressure. Lastly, this article provides an overview of the clinical applications of 4D PC-MRI in various cardiovascular regions. PMID:27390537
Ha, Hojin; Kim, Guk Bae; Kweon, Jihoon; Lee, Sang Joon; Kim, Young-Hak; Lee, Deok Hee; Yang, Dong Hyun; Kim, Namkug
2016-01-01
Recent improvements have been made to the use of time-resolved, three-dimensional phase-contrast (PC) magnetic resonance imaging (MRI), which is also named four-dimensional (4D) PC-MRI or 4D flow MRI, in the investigation of spatial and temporal variations in hemodynamic features in cardiovascular blood flow. The present article reviews the principle and analytical procedures of 4D PC-MRI. Various fluid dynamic biomarkers for possible clinical usage are also described, including wall shear stress, turbulent kinetic energy, and relative pressure. Lastly, this article provides an overview of the clinical applications of 4D PC-MRI in various cardiovascular regions. PMID:27390537
NASA Technical Reports Server (NTRS)
Lax, F. M.
1975-01-01
A time-controlled navigation system applicable to the descent phase of flight for airline transport aircraft was developed and simulated. The design incorporates the linear discrete-time sampled-data version of the linearized continuous-time system describing the aircraft's aerodynamics. Using optimal linear quadratic control techniques, an optimal deterministic control regulator which is implementable on an airborne computer is designed. The navigation controller assists the pilot in complying with assigned times of arrival along a four-dimensional flight path in the presence of wind disturbances. The strategic air traffic control concept is also described, followed by the design of a strategic control descent path. A strategy for determining possible times of arrival at specified waypoints along the descent path and for generating the corresponding route-time profiles that are within the performance capabilities of the aircraft is presented. Using a mathematical model of the Boeing 707-320B aircraft along with a Boeing 707 cockpit simulator interfaced with an Adage AGT-30 digital computer, a real-time simulation of the complete aircraft aerodynamics was achieved. The strategic four-dimensional navigation controller for longitudinal dynamics was tested on the nonlinear aircraft model in the presence of 15, 30, and 45 knot head-winds. The results indicate that the controller preserved the desired accuracy and precision of a time-controlled aircraft navigation system.
Jiang, Steve B. Wolfgang, John; Mageras, Gig S.
2008-05-01
Compared with conventional three-dimensional (3D) conformal radiation therapy and intensity-modulated radiation therapy treatments, quality assurance (QA) for motion-adaptive radiation therapy involves various challenges because of the added temporal dimension. Here we discuss those challenges for three specific techniques related to motion-adaptive therapy: namely respiratory gating, breath holding, and four-dimensional computed tomography. Similar to the introduction of any other new technologies in clinical practice, typical QA measures should be taken for these techniques also, including initial testing of equipment and clinical procedures, as well as frequent QA examinations during the early stage of implementation. Here, rather than covering every QA aspect in depth, we focus on some major QA challenges. The biggest QA challenge for gating and breath holding is how to ensure treatment accuracy when internal target position is predicted using external surrogates. Recommended QA measures for each component of treatment, including simulation, planning, patient positioning, and treatment delivery and verification, are discussed. For four-dimensional computed tomography, some major QA challenges have also been discussed.
NASA Astrophysics Data System (ADS)
Gustafsson, N.; Bojarova, J.
2014-07-01
A four-dimensional ensemble variational (4D-En-Var) data assimilation has been developed for a limited area model. The integration of tangent linear and adjoint models, as applied in standard 4D-Var, is replaced with the use of an ensemble of non-linear model states to estimate four-dimensional background error covariances over the assimilation time window. The computational costs for 4D-En-Var are therefore significantly reduced in comparison with standard 4D-Var and the scalability of the algorithm is improved. The flow dependency of 4D-En-Var assimilation increments is demonstrated in single simulated observation experiments and compared with corresponding increments from standard 4D-Var and Hybrid 4D-Var ensemble assimilation experiments. Real observation data assimilation experiments carried out over a 6-week period show that 4D-En-Var outperforms standard 4D-Var as well as Hybrid 4D-Var ensemble data assimilation with regard to forecast quality measured by forecast verification scores.
NASA Astrophysics Data System (ADS)
Marchuk, G. I.; Zalesny, V. B.
2012-02-01
The problem of modeling the World Ocean circulation with the four-dimensional assimilation of temperature and salinity fields is considered. A mathematical model of the ocean general circulation and a numerical algorithm for its solution are formulated. The model equations are written in a σ coordinate system on the sphere with the North Pole shifted to the point of the continent (60° E, 60.5° N). The model has a flexible numerical structure and consists of two parts: the forward prognostic model and its adjoint analog. The numerical algorithm for solving the forward and adjoint problems is based on the method of multicomponent splitting. This method includes splitting with respect to physical processes and geometric coordinates. Three series of numerical experiments are performed: (1) a test solution to the problem of the four-dimensional variational assimilation, (2) modeling of the World Ocean circulation with the variational assimilation of climatic temperature and salinity fields, and (3) modeling of the World Ocean circulation with the variational assimilation of climatic temperature and salinity fields and the data of Argo buoys. The results of calculations demonstrate the expediency of using the model of World Ocean circulation with the procedure of assimilating observational data for a description of the general structure of thermohaline fields.
The four-dimensional data assimilation (FDDA) technique in the Weather Research and Forecasting (WRF) meteorological model has recently undergone an important update from the original version. Previous evaluation results have demonstrated that the updated FDDA approach in WRF pr...
NASA Astrophysics Data System (ADS)
Kizilirmak, Ganimet Mülazımoğlu
2015-12-01
The four-dimensional Ising model is simulated on the Creutz cellular automaton (CCA) near the infinite-lattice critical temperature for the lattice with the linear dimension 4 ⩽ L ⩽ 22. The temperature dependence of Binder parameter ( g L) are analyzed for the lattice with the linear dimension 4 ⩽ L ⩽ 22. In this study conducted highly detailed, two different types of behavior were determined as a result of varying linear lattice dimension. The infinite lattice critical temperatures are obtained to be T c = 6.6845 ± 0.0005 in interval 4 ⩽ L ⩽ 12 and T c = 6.6807 ± 0.0024 in interval 14 ⩽ L ⩽ 22. The finite and infinite lattice critical exponents for the order parameter, the magnetic susceptibility and the specific heat are computed from the results of simulations by using finite-size scaling relations. Critical linear lattice size have been identified as L = 14.
NASA Astrophysics Data System (ADS)
Zheng, Xiangyang; Mayerle, Roberto; Xing, Qianguo; Fernández Jaramillo, José Manuel
2016-08-01
In this paper, a data assimilation scheme based on the adjoint free Four-Dimensional Variational(4DVar) method is applied to an existing storm surge model of the German North Sea. To avoid the need of an adjoint model, an ensemble-like method to explicitly represent the linear tangent equation is adopted. Results of twin experiments have shown that the method is able to recover the contaminated low dimension model parameters to their true values. The data assimilation scheme was applied to a severe storm surge event which occurred in the North Sea in December 5, 2013. By adjusting wind drag coefficient, the predictive ability of the model increased significantly. Preliminary experiments have shown that an increase in the predictive ability is attained by narrowing the data assimilation time window.
NASA Technical Reports Server (NTRS)
Hsu, J. P.
1983-01-01
The foundation of the quantum field theory is changed by introducing a new universal probability principle into field operators: one single inherent and invariant probability distribution P(/k/) is postulated for boson and fermion field oscillators. This can be accomplished only when one treats the four-dimensional symmetry from a broad viewpoint. Special relativity is too restrictive to allow such a universal probability principle. A radical length, R, appears in physics through the probability distribution P(/k/). The force between two point particles vanishes when their relative distance tends to zero. This appears to be a general property for all forces and resembles the property of asymptotic freedom. The usual infinities in vacuum fluctuations and in local interactions, however complicated they may be, are all removed from quantum field theories. In appendix A a simple finite and unitary theory of unified electroweak interactions is discussed without assuming Higgs scalar bosons.
Atkins, Sharona M; Sprenger, Amber M; Colflesh, Gregory J H; Briner, Timothy L; Buchanan, Jacob B; Chavis, Sydnee E; Chen, Sy-Yu; Iannuzzi, Gregory L; Kashtelyan, Vadim; Dowling, Eamon; Harbison, J Isaiah; Bolger, Donald J; Bunting, Michael F; Dougherty, Michael R
2014-01-01
We developed a novel four-dimensional spatial task called Shapebuilder and used it to predict performance on a wide variety of cognitive tasks. In six experiments, we illustrate that Shapebuilder: (1) Loads on a common factor with complex working memory (WM) span tasks and that it predicts performance on quantitative reasoning tasks and Ravens Progressive Matrices (Experiment 1), (2) Correlates well with traditional complex WM span tasks (Experiment 2), predicts performance on the conditional go/no go task (Experiment 3) and N-back (Experiment 4), and showed weak or nonsignificant correlations with the Attention Networks Task (Experiment 5), and task switching (Experiment 6). Shapebuilder shows that it exhibits minimal skew and kurtosis, and shows good reliability. We argue that Shapebuilder has many advantages over existing measures of WM, including the fact that it is largely language independent, is not prone to ceiling effects, and take less than 6 min to complete on average. PMID:24962121
NASA Astrophysics Data System (ADS)
Zheng, Xiangyang; Mayerle, Roberto; Xing, Qianguo; Fernández Jaramillo, José Manuel
2016-06-01
In this paper, a data assimilation scheme based on the adjoint free Four-Dimensional Variational(4DVar) method is applied to an existing storm surge model of the German North Sea. To avoid the need of an adjoint model, an ensemble-like method to explicitly represent the linear tangent equation is adopted. Results of twin experiments have shown that the method is able to recover the contaminated low dimension model parameters to their true values. The data assimilation scheme was applied to a severe storm surge event which occurred in the North Sea in December 5, 2013. By adjusting wind drag coefficient, the predictive ability of the model increased significantly. Preliminary experiments have shown that an increase in the predictive ability is attained by narrowing the data assimilation time window.
A note on the temperature and energy of four-dimensional black holes from an entropic force
NASA Astrophysics Data System (ADS)
Liu, Yu-Xiao; Wang, Yong-Qiang; Wei, Shao-Wen
2010-09-01
We investigate the temperature and energy on holographic screens for four-dimensional black holes with the entropic force idea proposed by Verlinde. We find that the 'Unruh-Verlinde temperature' is equal to the Hawking temperature on the horizon, and can be considered as a generalized Hawking temperature on the holographic screen outside the horizons. The energy on the holographic screen is not the black hole mass M but the reduced mass M0, which is related to the black hole parameters. With the replacement of the black hole mass M by the reduced mass M0, the entropic force can be written as F=\\frac{GmM_0}{r^2}, which could be tested by experiments.
NASA Astrophysics Data System (ADS)
Gao, Chuan; Wu, Xinrong; Zhang, Rong-Hua
2016-07-01
A four-dimensional variational (4D-Var) data assimilation method is implemented in an improved intermediate coupled model (ICM) of the tropical Pacific. A twin experiment is designed to evaluate the impact of the 4D-Var data assimilation algorithm on ENSO analysis and prediction based on the ICM. The model error is assumed to arise only from the parameter uncertainty. The "observation" of the SST anomaly, which is sampled from a "truth" model simulation that takes default parameter values and has Gaussian noise added, is directly assimilated into the assimilation model with its parameters set erroneously. Results show that 4D-Var effectively reduces the error of ENSO analysis and therefore improves the prediction skill of ENSO events compared with the non-assimilation case. These results provide a promising way for the ICM to achieve better real-time ENSO prediction.
NASA Astrophysics Data System (ADS)
Saito, A.; Tsugawa, T.; Nagayama, S.; Iwasaki, S.; Odagi, Y.; Kumano, Y.; Yoshikawa, M.; Akiya, Y.; Takahashi, M.
2011-12-01
We are developing educational and public outreach programs of the earth and planetary science data using a four-dimensional digital globe system, Dagik Earth. Dagik Earth is a simple and affordable four dimensional (three dimension in space and one dimension in time) presentation system of the earth and planetary scientific results. It can display the Earth and planets in three-dimensional way without glasses, and the time variation of the scientific data can be displayed on the Earth and planets image. It is easier to handle and lower cost than similar systems such as Geocosmos by Miraikan museum, Japan and Science On a Sphere by NOAA. At first it was developed as a presentation tool for public outreach programs in universities and research institutes by earth scientists. And now it is used in classrooms of schools and science museums collaboration with school teachers and museum curators. The three dimensional display can show the Earth and planets in exact form without any distortion, which cannot be achieved with two-dimensional display. Furthermore it can provide a sense of reality. Several educational programs have been developed and carried out in high schools, junior high schools, elementary schools and science centers. Several research institutes have used Dagik Earth in their public outreach programs to demonstrate their novel scientific results to public in universities, research institutes and science cafe events. A community of users and developers of Dagik Earth is being formed in Japan. In the presentation, the outline of Dagik Earth and the educational programs using Dagik Earth will be presented.
Goldstein, Seth D.; Ford, Eric C.; Duhon, Mario; McNutt, Todd; Wong, John; Herman, Joseph M.
2010-02-01
Purpose: Respiratory-induced excursions of locally advanced pancreatic adenocarcinoma could affect dose delivery. This study quantified tumor motion and evaluated standard treatment margins. Methods and Materials: Respiratory-correlated four-dimensional computed tomography images were obtained on 30 patients with locally advanced pancreatic adenocarcinoma; 15 of whom underwent repeat scanning before cone-down treatment. Treatment planning software was used to contour the gross tumor volume (GTV), bilateral kidneys, and biliary stent. Excursions were calculated according to the centroid of the contoured volumes. Results: The mean +- standard deviation GTV excursion in the superoinferior (SI) direction was 0.55 +- 0.23 cm; an expansion of 1.0 cm adequately accounted for the GTV motion in 97% of locally advanced pancreatic adenocarcinoma patients. Motion GTVs were generated and resulted in a 25% average volume increase compared with the static GTV. Of the 30 patients, 17 had biliary stents. The mean SI stent excursion was 0.84 +- 0.32 cm, significantly greater than the GTV motion. The xiphoid process moved an average of 0.35 +- 0.12 cm, significantly less than the GTV. The mean SI motion of the left and right kidneys was 0.65 +- 0.27 cm and 0.77 +- 0.30 cm, respectively. At repeat scanning, no significant changes were seen in the mean GTV size (p = .8) or excursion (p = .3). Conclusion: These data suggest that an asymmetric expansion of 1.0, 0.7, and 0.6 cm along the respective SI, anteroposterior, and medial-lateral directions is recommended if a respiratory-correlated four-dimensional computed tomography scan is not available to evaluate the tumor motion during treatment planning. Surrogates of tumor motion, such as biliary stents or external markers, should be used with caution.
NASA Astrophysics Data System (ADS)
Yamamoto, Tokihiro; Kabus, Sven; Klinder, Tobias; Lorenz, Cristian; von Berg, Jens; Blaffert, Thomas; Loo, Billy W., Jr.; Keall, Paul J.
2011-04-01
A pulmonary ventilation imaging technique based on four-dimensional (4D) computed tomography (CT) has advantages over existing techniques. However, physiologically accurate 4D-CT ventilation imaging has not been achieved in patients. The purpose of this study was to evaluate 4D-CT ventilation imaging by correlating ventilation with emphysema. Emphysematous lung regions are less ventilated and can be used as surrogates for low ventilation. We tested the hypothesis: 4D-CT ventilation in emphysematous lung regions is significantly lower than in non-emphysematous regions. Four-dimensional CT ventilation images were created for 12 patients with emphysematous lung regions as observed on CT, using a total of four combinations of two deformable image registration (DIR) algorithms: surface-based (DIRsur) and volumetric (DIRvol), and two metrics: Hounsfield unit (HU) change (VHU) and Jacobian determinant of deformation (VJac), yielding four ventilation image sets per patient. Emphysematous lung regions were detected by density masking. We tested our hypothesis using the one-tailed t-test. Visually, different DIR algorithms and metrics yielded spatially variant 4D-CT ventilation images. The mean ventilation values in emphysematous lung regions were consistently lower than in non-emphysematous regions for all the combinations of DIR algorithms and metrics. VHU resulted in statistically significant differences for both DIRsur (0.14 ± 0.14 versus 0.29 ± 0.16, p = 0.01) and DIRvol (0.13 ± 0.13 versus 0.27 ± 0.15, p < 0.01). However, VJac resulted in non-significant differences for both DIRsur (0.15 ± 0.07 versus 0.17 ± 0.08, p = 0.20) and DIRvol (0.17 ± 0.08 versus 0.19 ± 0.09, p = 0.30). This study demonstrated the strong correlation between the HU-based 4D-CT ventilation and emphysema, which indicates the potential for HU-based 4D-CT ventilation imaging to achieve high physiologic accuracy. A further study is needed to confirm these results.
Ahmad, Moiz; Balter, Peter; Pan, Tinsu
2011-10-15
Purpose: Data sufficiency are a major problem in four-dimensional cone-beam computed tomography (4D-CBCT) on linear accelerator-integrated scanners for image-guided radiotherapy. Scan times must be in the range of 4-6 min to avoid undersampling artifacts. Various image reconstruction algorithms have been proposed to accommodate undersampled data acquisitions, but these algorithms are computationally expensive, may require long reconstruction times, and may require algorithm parameters to be optimized. The authors present a novel reconstruction method, 4D volume-of-interest (4D-VOI) reconstruction which suppresses undersampling artifacts and resolves lung tumor motion for undersampled 1-min scans. The 4D-VOI reconstruction is much less computationally expensive than other 4D-CBCT algorithms. Methods: The 4D-VOI method uses respiration-correlated projection data to reconstruct a four-dimensional (4D) image inside a VOI containing the moving tumor, and uncorrelated projection data to reconstruct a three-dimensional (3D) image outside the VOI. Anatomical motion is resolved inside the VOI and blurred outside the VOI. The authors acquired a 1-min. scan of an anthropomorphic chest phantom containing a moving water-filled sphere. The authors also used previously acquired 1-min scans for two lung cancer patients who had received CBCT-guided radiation therapy. The same raw data were used to test and compare the 4D-VOI reconstruction with the standard 4D reconstruction and the McKinnon-Bates (MB) reconstruction algorithms. Results: Both the 4D-VOI and the MB reconstructions suppress nearly all the streak artifacts compared with the standard 4D reconstruction, but the 4D-VOI has 3-8 times greater contrast-to-noise ratio than the MB reconstruction. In the dynamic chest phantom study, the 4D-VOI and the standard 4D reconstructions both resolved a moving sphere with an 18 mm displacement. The 4D-VOI reconstruction shows a motion blur of only 3 mm, whereas the MB reconstruction
Maeba, Satoru; Taguchi, Takahiro; Midorikawa, Hirofumi; Kanno, Megumu; Sueda, Taijiro
2013-01-01
OBJECTIVES Functional tricuspid regurgitation (FTR) is generally caused by the dilation of the tricuspid annulus (TA) and the tethering of tricuspid leaflets; however, it also occurs in patients without dilatation of the TA. The aim of this study was to develop and to use a four-dimensional tracking system, utilizing cardiac magnetic resonance imaging (MRI), and to assess TA flexibility in patients with early FTR without right ventricle dilation as a preliminary investigation for the mechanism of early FTR. METHODS The structure and movement of the TA were examined in 20 healthy subjects and 19 FTR patients whose right ventricle was not dilated. We analysed the short axis and longitudinal movement of a mid-septal point (S), a mid-lateral point (L), a mid-anterior point (A) and a mid-posterior point (P) on the TA throughout the cardiac cycle. The tethering distance of the tricuspid leaflets and the integrated orbiting volume of the TA were also measured. RESULTS The TA area (mm2) and AP and LS distances (mm) did not differ significantly between the two groups, but the longitudinally moving distances (mm) of the four points were significantly shorter in patients with FTR than in healthy subjects. Also, the mean tethering distance (mm) was significantly longer in patients with FTR than in healthy subjects (9.0 ± 1.5 vs 4.0 ± 1.3, respectively; P < 0.001), and the integrated volume (mm3) of the annular moving track, throughout the cardiac cycle, was significantly larger in healthy subjects than in patients with FTR (40 428 ± 10 951 vs 22 967 ± 6079, P < 0.001). CONCLUSIONS The longitudinal flexibility of the TA in FTR patients was significantly less than that in the healthy subjects, and the tethering of the tricuspid leaflets occurred in FTR patients despite the absence of TA and RV dilation, which can be one triggering factor of early FTR. Four-dimensional geometric assessment, using cardiac MRI and the tracking program that we have developed, is capable of
Lee, Youngone; Kang, Gungwon; Kim, Hyeong-Chan; Lee, Jungjai
2011-10-15
We investigate string or branelike solutions for four-dimensional vacuum Einstein equations in the presence of a cosmological constant. For the case of negative cosmological constant, the Banados-Teitelboim-Zanelli black string is the only warped stringlike solution. The general solutions for nonwarped branelike configurations are found and they are characterized by the Arnowitt-Deser-Misner mass density and two tensions. Interestingly, the sum of these tensions is equal to the minus of the mass density. Other than the well-known black string and soliton spacetimes, all the static solutions possess naked singularities. The time-dependent solutions can be regarded as the anti-de Sitter extension of the well-known Kasner solutions. The speciality of those static regular solutions and the implication of singular solutions are also discussed in the context of cylindrical matter collapse. For the case of positive cosmological constant, the Kasner-de Sitter spacetime appears as time-dependent solutions and all static solutions are found to be naked singular.
NASA Astrophysics Data System (ADS)
Lee, Youngone; Kang, Gungwon; Kim, Hyeong-Chan; Lee, Jungjai
2011-10-01
We investigate string or branelike solutions for four-dimensional vacuum Einstein equations in the presence of a cosmological constant. For the case of negative cosmological constant, the Bañados-Teitelboim-Zanelli black string is the only warped stringlike solution. The general solutions for nonwarped branelike configurations are found and they are characterized by the Arnowitt-Deser-Misner mass density and two tensions. Interestingly, the sum of these tensions is equal to the minus of the mass density. Other than the well-known black string and soliton spacetimes, all the static solutions possess naked singularities. The time-dependent solutions can be regarded as the anti-de Sitter extension of the well-known Kasner solutions. The speciality of those static regular solutions and the implication of singular solutions are also discussed in the context of cylindrical matter collapse. For the case of positive cosmological constant, the Kasner-de Sitter spacetime appears as time-dependent solutions and all static solutions are found to be naked singular.
NASA Astrophysics Data System (ADS)
Coudert, L. H.
2015-01-01
Torsional control is studied theoretically using a four-dimensional (4D) model introduced recently [Phys. Rev. Lett. 107, 113004 (2011), 10.1103/PhysRevLett.107.113004 and Phys. Rev. A 87, 043403 (2013), 10.1103/PhysRevA.87.043403] for calculating energy levels and eigenfunctions of nonrigid biphenyl-like molecules undergoing internal rotation and subject to a strong electric field. The time-dependent Schrödinger equation is solved to determine the behavior of the molecule when submitted to a short laser pulse. Torsional alignment is investigated for four limiting hindering potentials and for several peak laser intensities. The results obtained with the 4D model are compared to those from already available 2D and 1D models. Similar results are found with the 4D and 2D model and are consistent with the molecule interacting the most with the electric field for the hindering potential displaying four minima with D2 d symmetry staggered equilibrium configurations. Molecular axis alignment is also investigated and it is found that the one arising with the 4D model starts deviating substantially from the one arising with a rigid rotator for a value of the peak laser intensity of 3 ×1013 W/cm 2.
Zhang, Yequn; Arabaci, Murat; Djordjevic, Ivan B
2012-04-01
Leveraging the advanced coherent optical communication technologies, this paper explores the feasibility of using four-dimensional (4D) nonbinary LDPC-coded modulation (4D-NB-LDPC-CM) schemes for long-haul transmission in future optical transport networks. In contrast to our previous works on 4D-NB-LDPC-CM which considered amplified spontaneous emission (ASE) noise as the dominant impairment, this paper undertakes transmission in a more realistic optical fiber transmission environment, taking into account impairments due to dispersion effects, nonlinear phase noise, Kerr nonlinearities, and stimulated Raman scattering in addition to ASE noise. We first reveal the advantages of using 4D modulation formats in LDPC-coded modulation instead of conventional two-dimensional (2D) modulation formats used with polarization-division multiplexing (PDM). Then we demonstrate that 4D LDPC-coded modulation schemes with nonbinary LDPC component codes significantly outperform not only their conventional PDM-2D counterparts but also the corresponding 4D bit-interleaved LDPC-coded modulation (4D-BI-LDPC-CM) schemes, which employ binary LDPC codes as component codes. We also show that the transmission reach improvement offered by the 4D-NB-LDPC-CM over 4D-BI-LDPC-CM increases as the underlying constellation size and hence the spectral efficiency of transmission increases. Our results suggest that 4D-NB-LDPC-CM can be an excellent candidate for long-haul transmission in next-generation optical networks. PMID:22513641
NASA Astrophysics Data System (ADS)
Hansis, Eberhard; Schomberg, Hermann; Erhard, Klaus; Dössel, Olaf; Grass, Michael
2009-02-01
The tomographic reconstruction of the beating heart requires dedicated methods. One possibility is gated reconstruction, where only data corresponding to a certain motion state are incorporated. Another one is motioncompensated reconstruction with a pre-computed motion vector field, which requires a preceding estimation of the motion. Here, results of a new approach are presented: simultaneous reconstruction of a three-dimensional object and its motion over time, yielding a fully four-dimensional representation. The object motion is modeled by a time-dependent elastic transformation. The reconstruction is carried out with an iterative gradient-descent algorithm which simultaneously optimizes the three-dimensional image and the motion parameters. The method was tested on a simulated rotational X-ray acquisition of a dynamic coronary artery phantom, acquired on a C-arm system with a slowly rotating C-arm. Accurate reconstruction of both absorption coefficient and motion could be achieved. First results from experiments on clinical rotational X-ray coronary angiography data are shown. The resulting reconstructions enable the analysis of both static properties, such as vessel geometry and cross-sectional areas, and dynamic properties, like magnitude, speed, and synchrony of motion during the cardiac cycle.
The quest for four-dimensional imaging in plant cell biology: it's just a matter of time
Domozych, David S.
2012-01-01
Background Analysis of plant cell dynamics over time, or four-dimensional imaging (4-DI), represents a major goal of plant science. The ability to resolve structures in the third dimension within the cell or tissue during developmental events or in response to environmental or experimental stresses (i.e. 4-DI) is critical to our understanding of gene expression, post-expression modulations of macromolecules and sub-cellular system interactions. Scope Microscopy-based technologies have been profoundly integral to this type of investigation, and new and refined microscopy technologies now allow for the visualization of cell dynamics with unprecedented resolution, contrast and experimental versatility. However, certain realities of light and electron microscopy, choice of specimen and specimen preparation techniques limit the scope of readily attaining 4-DI. Today, the plant microscopist must use a combinatorial strategy whereby multiple microscopy-based investigations are used. Modern fluorescence, confocal laser scanning, transmission electron and scanning electron microscopy provide effective conduits for synthesizing data detailing live cell dynamics and highly resolved snapshots of specific cell structures that will ultimately lead to 4-DI. This review provides a synopsis of such technologies available. PMID:22628381
NASA Astrophysics Data System (ADS)
Saito, Akinori; Yoshida, Daiki; Odagi, Yoko; Takahashi, Midori; Tsugawa, Takuya; Kumano, Yoshisuke
We developed an educational program of space science data and science data observed from the space using a digital globe system, Dagik Earth. Dagik Earth is a simple and affordable four dimensional (three dimension in space and one dimension in time) presentation system. The educational program using Dagik Earth has been carried out in classrooms of schools, science museums, and research institutes to show the scientific data of the earth and planets in an intuitive way. We are developing the hardware system, data contents, and education manuals in cooperation with teachers, museum staffs and scientists. The size of the globe used in this system is from 15cm to 2m in diameter. It is selected according to the environment of the presentation. The contents cover the space science, such as aurora and geomagnetic field, the earth science, such as global clouds and earthquakes, and planetary science. Several model class plans are ready to be used in high school and junior high school. In public outreach programs of universities, research institutes, and scientific meetings, special programs have been carried out. We are establishing a community to use and develop this program for the space science education.
NASA Astrophysics Data System (ADS)
Salisbury, Donald; Renn, Jürgen; Sundermeyer, Kurt
2016-02-01
Classical background independence is reflected in Lagrangian general relativity through covariance under the full diffeomorphism group. We show how this independence can be maintained in a Hamilton-Jacobi approach that does not accord special privilege to any geometric structure. Intrinsic space-time curvature-based coordinates grant equal status to all geometric backgrounds. They play an essential role as a starting point for inequivalent semiclassical quantizations. The scheme calls into question Wheeler’s geometrodynamical approach and the associated Wheeler-DeWitt equation in which 3-metrics are featured geometrical objects. The formalism deals with variables that are manifestly invariant under the full diffeomorphism group. Yet, perhaps paradoxically, the liberty in selecting intrinsic coordinates is precisely as broad as is the original diffeomorphism freedom. We show how various ideas from the past five decades concerning the true degrees of freedom of general relativity can be interpreted in light of this new constrained Hamiltonian description. In particular, we show how the Kuchař multi-fingered time approach can be understood as a means of introducing full four-dimensional diffeomorphism invariants. Every choice of new phase space variables yields new Einstein-Hamilton-Jacobi constraining relations, and corresponding intrinsic Schrödinger equations. We show how to implement this freedom by canonical transformation of the intrinsic Hamiltonian. We also reinterpret and rectify significant work by Dittrich on the construction of “Dirac observables.”
Carrasco-Zevallos, Oscar M; Keller, Brenton; Viehland, Christian; Shen, Liangbo; Seider, Michael I; Izatt, Joseph A; Toth, Cynthia A
2016-07-01
Magnification of the surgical field using the operating microscope facilitated profound innovations in retinal surgery in the 1970s, such as pars plana vitrectomy. Although surgical instrumentation and illumination techniques are continually developing, the operating microscope for vitreoretinal procedures has remained essentially unchanged and currently limits the surgeon's depth perception and assessment of subtle microanatomy. Optical coherence tomography (OCT) has revolutionized clinical management of retinal pathology, and its introduction into the operating suite may have a similar impact on surgical visualization and treatment. In this article, we review the evolution of OCT for retinal surgery, from perioperative analysis to live volumetric (four-dimensional, 4D) image-guided surgery. We begin by briefly addressing the benefits and limitations of the operating microscope, the progression of OCT technology, and OCT applications in clinical/perioperative retinal imaging. Next, we review intraoperative OCT (iOCT) applications using handheld probes during surgical pauses, two-dimensional (2D) microscope-integrated OCT (MIOCT) of live surgery, and volumetric MIOCT of live surgery. The iOCT discussion focuses on technological advancements, applications during human retinal surgery, translational difficulties and limitations, and future directions. PMID:27409495
Real-time volume rendering of four-dimensional images based on three-dimensional texture mapping.
Hwang, J; Kim, J S; Kim, J S; Kim, I Y; Kim, S I
2001-06-01
A four-dimensional (4-D) image consists of three-dimensional (3-D) volume data that varies with time. It is used to express a deforming or moving object in virtual surgery or 4-D ultrasound. It is difficult to obtain 4-D images by conventional ray-casting or shear-warp factorization methods because of their time-consuming rendering process and the pre-processing stage necessary whenever the volume data are changed. Even when 3-D texture mapping is used, repeated volume loading is time-consuming in 4-D image rendering. In this study, we propose a method to reduce data loading time using coherence between currently loaded volume and previously loaded volume in order to achieve real-time rendering based on 3-D texture mapping. Volume data are divided into small bricks and each brick being loaded is tested for similarity to one that was already loaded in memory. If the brick passes the test, it is defined as 3-D texture by OpenGL functions. Later, the texture slices of the brick are mapped into polygons and blended by OpenGL blending functions. All bricks undergo this test. Using continuous deforming, 50 volumes are rendered in interactive time with SGI ONYX. Realtime volume rendering based on 3-D texture mapping is currently available for personal computers. PMID:11442097
NASA Astrophysics Data System (ADS)
Zhang, Honghai; Walker, Nicholas; Mitchell, Steven C.; Thomas, Matthew; Wahle, Andreas; Scholz, Thomas; Sonka, Milan
2006-03-01
Conventional analysis of cardiac ventricular magnetic resonance images is performed using short axis images and does not guarantee completeness and consistency of the ventricle coverage. In this paper, a four-dimensional (4D, 3D+time) left and right ventricle statistical shape model was generated from the combination of the long axis and short axis images. Iterative mutual intensity registration and interpolation were used to merge the long axis and short axis images into isotropic 4D images and simultaneously correct existing breathing artifact. Distance-based shape interpolation and approximation were used to generate complete ventricle shapes from the long axis and short axis manual segmentations. Landmarks were automatically generated and propagated to 4D data samples using rigid alignment, distance-based merging, and B-spline transform. Principal component analysis (PCA) was used in model creation and analysis. The two strongest modes of the shape model captured the most important shape feature of Tetralogy of Fallot (TOF) patients, right ventricle enlargement. Classification of cardiac images into classes of normal and TOF subjects performed on 3D and 4D models showed 100% classification correctness rates for both normal and TOF subjects using k-Nearest Neighbor (k=1 or 3) classifier and the two strongest shape modes.
NASA Astrophysics Data System (ADS)
Zhang, Honghai; Thomas, Matthew T.; Walker, Nicholas E.; Stolpen, Alan H.; Wahle, Andreas; Scholz, Thomas D.; Sonka, Milan
2007-03-01
Conventional analysis of cardiac ventricular function from magnetic resonance images is typically relying on short axis image information only. Usually, two cardiac phases of the cardiac cycle are analyzed- the end-diastole and end-systole. Unfortunately, the short axis ventricular coverage is incomplete and inconsistent due to the lack of image information about the ventricular apex and base. In routine clinical images, this information is only available in long axis image planes. Additionally, the standard ventricular function indices such as ejection fraction are only based on a limited temporal information and therefore do not fully describe the four-dimensional (4D, 3D+time) nature of the heart's motion. We report a novel approach in which the long and short axis image data are fused to correct for respiratory motion and form a spatio-temporal 4D data sequence with cubic voxels. To automatically segment left and right cardiac ventricles, a 4D active appearance model was built. Applying the method to cardiac segmentation of tetralogy of Fallot (TOF) and normal hearts, our method achieved mostly subvoxel signed surface positioning errors of 0.2+/-1.1 voxels for normal left ventricle, 0.6+/-1.5 voxels for normal right ventricle, 0.5+/-2.1 voxels for TOF left ventricle, and 1.3+/-2.6 voxels for TOF right ventricle. Using the computer segmentation results, the cardiac shape and motion indices and volume-time curves were derived as novel indices describing the ventricular function in 4D.
Koorevaar, Rinco C T; Terluin, Berend; van 't Riet, Esther; Madden, Kim; Bulstra, Sjoerd K
2016-04-01
Psychological problems are common in shoulder patients. A validated psychological questionnaire measuring clinically relevant psychological symptoms (including distress, depression, anxiety, and somatization) in shoulder patients is lacking. The Four-Dimensional Symptom Questionnaire (4DSQ) is a self-report questionnaire to identify distress, depression, anxiety, and somatization which has been validated in primary care populations. The aim of this study was to validate the 4DSQ in orthopedic shoulder patients. We assessed whether the 4DSQ measures these four constructs the same way in an orthopedic population with shoulder problems compared to a general practice population. We also investigated the prevalence of psychological symptoms in shoulder patients. The shoulder group consisted of 200 consecutive patients and the general practice group comprised 368 patients, matched for gender and age. Differential item functioning analysis showed that the 4DSQ measures the different psychological symptoms in orthopedic shoulder patients the same way as in general practice patients. The shoulder patients tended to score higher on the somatization scale, resulting in a new cut-off point for somatization. The prevalence of distress, somatization, anxiety, and depression in the shoulder group was 23%, 14%, 10%, and 8%, respectively. It can be concluded from this study that the 4DSQ in orthopedic shoulder patients measures the same constructs as in general practice patients and can therefore be used in orthopedic practice to measure psychological symptoms in patients with shoulder complaints. PMID:26379216
Cao, Gaolong; Sun, Shuaishuai; Li, Zhongwen; Tian, Huanfang; Yang, Huaixin; Li, Jianqi
2015-01-01
Recent advances in the four-dimensional ultrafast transmission electron microscope (4D-UTEM) with combined spatial and temporal resolutions have made it possible to directly visualize structural dynamics of materials at the atomic level. Herein, we report on our development on a 4D-UTEM which can be operated properly on either the photo-emission or the thermionic mode. We demonstrate its ability to obtain sequences of snapshots with high spatial and temporal resolutions in the study of lattice dynamics of the multi-walled carbon nanotubes (MWCNTs). This investigation provides an atomic level description of remarkable anisotropic lattice dynamics at the picosecond timescales. Moreover, our UTEM measurements clearly reveal that distinguishable lattice relaxations appear in intra-tubular sheets on an ultrafast timescale of a few picoseconds and after then an evident lattice expansion along the radial direction. These anisotropic behaviors in the MWCNTs are considered arising from the variety of chemical bonding, i.e. the weak van der Waals bonding between the tubular planes and the strong covalent sp2-hybridized bonds in the tubular sheets. PMID:25672762
NASA Astrophysics Data System (ADS)
Xiao, C.; Groening, L.; Gerhard, P.; Maier, M.; Mickat, S.; Vormann, H.
2016-06-01
Knowledge of the transverse four-dimensional beam rms-parameters is essential for applications that involve lattice elements that couple the two transverse degrees of freedom (planes). Usually pepper-pots are used for measuring these beam parameters. However, for ions their application is limited to energies below 150 keV/u. This contribution is on measurements of the full transverse four-dimensional second-moments beam matrix of high intensity uranium ions at an energy of 11.4 MeV/u. The combination of skew quadrupoles with a slit/grid emittance measurement device has been successfully applied.
Patel, Abhijit A.; Wolfgang, John A.; Niemierko, Andrzej; Hong, Theodore S.; Yock, Torunn; Choi, Noah C.
2009-05-01
Purpose: To evaluate the respiratory motion of primary esophageal cancers and pathologic celiac-region lymph nodes using time-resolved four-dimensional computed tomography (4D CT). Methods and Materials: Respiration-synchronized 4D CT scans were obtained to quantify the motion of primary tumors located in the proximal, mid-, or distal thoracic esophagus, as well as any involved celiac-region lymph nodes. Respiratory motion was measured in the superior-inferior (SI), anterior-posterior (AP), and left-right (LR) directions and was analyzed for correlation with anatomic location. Recommended margin expansions were determined for both primary and nodal targets. Results: Thirty patients underwent 4D CT scans at Massachusetts General Hospital for planned curative treatment of esophageal cancer. Measurements of respiratory tumor motion were obtained for 1 proximal, 4 mid-, and 25 distal esophageal tumors, as well as 12 involved celiac-region lymph nodes. The mean (SD) peak-to-peak displacements of all primary tumors in the SI, AP, and LR dimensions were 0.80 (0.45) cm, 0.28 (0.20) cm, and 0.22 (0.23) cm, respectively. Distal tumors were found to have significantly greater SI and AP motion than proximal or mid-esophageal tumors. The mean (SD) SI, AP, and LR peak-to-peak displacements of the celiac-region lymph nodes were 0.92 (0.56) cm, 0.46 (0.27) cm, and 0.19 (0.26) cm, respectively. Conclusions: Margins of 1.5 cm SI, 0.75 cm AP, and 0.75 cm LR would account for respiratory tumor motion of >95% of esophageal primary tumors in the dataset. All celiac-region lymph nodes would be adequately covered with SI, AP, and LR margins of 2.25 cm, 1.0 cm, and 0.75 cm, respectively.
OBrien, R; Shieh, C; Kipritidis, J; Keall, P
2014-06-15
Purpose: Four dimensional cone beam computed tomography (4DCBCT) is an emerging image guidance strategy but it can suffer from poor image quality. To avoid repeating scans it is beneficial to make the best use of the imaging data obtained. For conventional 4DCBCT the location and size of respiratory bins is fixed and projections are allocated to the respiratory bin within which it falls. Strictly adhering to this rule is unnecessary and can compromise image quality. In this study we optimize the size and location of respiratory bins and allow projections to be sourced from adjacent phases of the respiratory cycle. Methods: A mathematical optimization framework using mixed integer quadratic programming has been developed that determines when to source projections from adjacent respiratory bins and optimizes the size and location of the bins. The method, which we will call projection sharing, runs in under 2 seconds of CPU time. Five 4DCBCT datasets of stage III-IV lung cancer patients were used to test the algorithm. The standard deviation of the angular separation between projections (SD-A) and the standard deviation in the volume of the reconstructed fiducial gold coil (SD-V) were used as proxies to measure streaking artefacts and motion blur respectively. Results: The SD-A using displacement binning and projection sharing was 30%–50% smaller than conventional phase based binning and 59%–76% smaller than conventional displacement binning indicating more uniformly spaced projections and fewer streaking artefacts. The SD-V was 20–90% smaller when using projection sharing than using conventional phase based binning suggesting more uniform marker segmentation and less motion blur. Conclusion: Image quality was visibly and significantly improved with projection sharing. Projection sharing does not require any modifications to existing hardware and offers a more robust replacement to phase based binning, or, an option if phase based reconstruction is not of a
NASA Astrophysics Data System (ADS)
Peng, G. S.; Hou, C. Y.; Rife, D. L.; Dattore, R.
2014-12-01
Wind energy cost models incur inaccuracies from uncertainty in ambient wind measurements and estimates. This inhibits the best possible investment in wind energy infrastructure and management systems. High-resolution temporal and spatial wind data needed for wind availability analysis—usually created with regional-scale models—have traditionally been proprietary and costly to obtain. Freely available global model data suffers from either lower spatial or temporal resolution, or both. Low spatial resolution fails to realistically represent wind speeds in complex terrain. Low temporal resolution fails to capture the full diurnal cycle of wind behavior. The NCAR Global Climate Four-Dimensional Data Assimilation (CFDDA) Hourly 40 km Reanalysis was developed in 2009-2010 by the Research Applications Laboratory (RAL) to provide the most accurate boundary layer wind estimates available at that time. CFDDA used 28 sigma levels, with 19 between the surface and 700 hPa, a four-fold improvement over the contemporary NWP models. The dataset spans 21 years, 1985-2005, providing hourly atmospheric parameters, including winds, on 28 vertical levels on a global 40 km grid. This presentation will introduce the modeling and assimilation strategy, highlight the available data content including the parameter set, and review the data access options available from the RDA. CFDDA project partners, Defense Threat Reduction Agency (DTRA), NCAR RAL and NCAR Mesoscale & Microscale Meteorology (MMM) divisions are offering this dataset to the public for free with minor restrictions. NCAR Research Data Archive (RDA), hosted by the Computational and Information Systems Laboratory, provides data support. It is available at http://rda.ucar.edu/datasets/ds604.0/
TH-A-19A-10: Fast Four Dimensional Monte Carlo Dose Computations for Proton Therapy of Lung Cancer
Mirkovic, D; Titt, U; Mohan, R; Yepes, P
2014-06-15
Purpose: To develop and validate a fast and accurate four dimensional (4D) Monte Carlo (MC) dose computation system for proton therapy of lung cancer and other thoracic and abdominal malignancies in which the delivered dose distributions can be affected by respiratory motion of the patient. Methods: A 4D computer tomography (CT) scan for a lung cancer patient treated with protons in our clinic was used to create a time dependent patient model using our in-house, MCNPX-based Monte Carlo system (“MC{sup 2}”). The beam line configurations for two passively scattered proton beams used in the actual treatment were extracted from the clinical treatment plan and a set of input files was created automatically using MC{sup 2}. A full MC simulation of the beam line was computed using MCNPX and a set of phase space files for each beam was collected at the distal surface of the range compensator. The particles from these phase space files were transported through the 10 voxelized patient models corresponding to the 10 phases of the breathing cycle in the 4DCT, using MCNPX and an accelerated (fast) MC code called “FDC”, developed by us and which is based on the track repeating algorithm. The accuracy of the fast algorithm was assessed by comparing the two time dependent dose distributions. Results: The error of less than 1% in 100% of the voxels in all phases of the breathing cycle was achieved using this method with a speedup of more than 1000 times. Conclusion: The proposed method, which uses full MC to simulate the beam line and the accelerated MC code FDC for the time consuming particle transport inside the complex, time dependent, geometry of the patient shows excellent accuracy together with an extraordinary speed.
Gui Minzhi; Feng Yuanming; Yi Byongyong; Dhople, Anil Arvind; Yu, Cedric
2010-05-15
Purpose: Planning for the delivery of intensity-modulated radiation therapy (IMRT) to a moving target, referred to as four-dimensional (4D) IMRT planning, is a crucial step for achieving the treatment objectives for sites that move during treatment delivery. The authors proposed a simplistic method that accounts for both rigid and nonrigid respiration-induced target motion based on 4D computed tomography (4DCT) data sets. Methods: A set of MLC apertures and weights was first optimized on a reference phase of a 4DCT data set. At each beam angle, the apertures were morphed from the reference phase to each of the remaining phases according to the relative shape changes in the beam's eye view of the target. Three different planning schemes were evaluated for two lung cases and one pancreas patient: (1) Individually optimizing each breathing phase; (2) optimizing the reference phase and shifting the optimized apertures to other breathing phases based on a rigid-body image registration; and (3) optimizing the reference phase and deforming the optimized apertures to the other phases based on the deformation and translation of target contours. Planning results using scheme 1 serves as the ''gold standard'' for plan quality assessment; scheme 2 is the method previously proposed in the literature; and scheme 3 is the method the authors proposed in this article. The optimization results were compared between the three schemes for all three cases. Results: The proposed scheme 3 is comparable to scheme 1 in plan quality, and provides improved target coverage and conformity with similar normal tissue dose compared with scheme 2. Conclusions: Direct aperture deformation method for 4D IMRT planning improves upon methods that only consider rigid-body motion and achieves a plan quality close to that optimized for each of the phases.
Development of a four-dimensional image-guided radiotherapy system with a gimbaled X-ray head
Kamino, Yuichiro . E-mail: daisaku_horiuchi@mhi.co.jp; Takayama, Kenji; Kokubo, Masaki; Narita, Yuichiro; Hirai, Etsuro; Kawawda, Noriyuki; Mizowaki, Takashi; Nagata, Yasushi; Nishidai, Takehiro; Hiraoka, Masahiro
2006-09-01
Purpose: To develop and evaluate a new four-dimensional image-guided radiotherapy system, which enables precise setup, real-time tumor tracking, and pursuit irradiation. Methods and Materials: The system has an innovative gimbaled X-ray head that enables small-angle ({+-}2.4{sup o}) rotations (pan and tilt) along the two orthogonal gimbals. This design provides for both accurate beam positioning at the isocenter by actively compensating for mechanical distortion and quick pursuit of the target. The X-ray head is composed of an ultralight C-band linear accelerator and a multileaf collimator. The gimbaled X-ray head is mounted on a rigid O-ring structure with an on-board imaging subsystem composed of two sets of kilovoltage X-ray tubes and flat panel detectors, which provides a pair of radiographs, cone beam computed tomography images useful for image guided setup, and real-time fluoroscopic monitoring for pursuit irradiation. Results: The root mean square accuracy of the static beam positioning was 0.1 mm for 360{sup o} of O-ring rotation. The dynamic beam response and positioning accuracy was {+-}0.6 mm for a 0.75 Hz, 40-mm stroke and {+-}0.4 mm for a 2.0 Hz, 8-mm stroke. The quality of the images was encouraging for using the tomography-based setup. Fluoroscopic images were sufficient for monitoring and tracking lung tumors. Conclusions: Key functions and capabilities of our new system are very promising for precise image-guided setup and for tracking and pursuit irradiation of a moving target.
Wang, Wei; Li, Jianbin; Zhang, Yingjie; Shao, Qian; Xu, Min; Guo, Bing; Shang, Dongping
2016-01-01
Purpose To investigate the correlation of gross tumor volume (GTV) motion with the structure of interest (SOI) motion and volume variation for middle and distal esophageal cancers using four-dimensional computed tomography (4DCT). Patients and methods Thirty-three patients with middle or distal esophageal carcinoma underwent 4DCT simulation scan during free breathing. All image sets were registered with 0% phase, and the GTV, apex of diaphragm, lung, and heart were delineated on each phase of the 4DCT data. The position of GTV and SOI was identified in all 4DCT phases, and the volume of lung and heart was also achieved. The phase relationship between the GTV and SOI was estimated through Pearson’s correlation test. Results The mean peak-to-peak displacement of all primary tumors in the lateral (LR), anteroposterior (AP), and superoinferior (SI) directions was 0.13 cm, 0.20 cm, and 0.30 cm, respectively. The SI peak-to-peak motion of the GTV was defined as the greatest magnitude of motion. The displacement of GTV correlated well with heart in three dimensions and significantly associated with bilateral lung in LR and SI directions. A significant correlation was found between the GTV and apex of the diaphragm in SI direction (rleft=0.918 and rright=0.928). A significant inverse correlation was found between GTV motion and varying lung volume, but the correlation was not significant with heart (rLR=−0.530, rAP=−0.531, and rSI=−0.588) during respiratory cycle. Conclusion For middle and distal esophageal cancers, GTV should expand asymmetric internal margins. The primary tumor motion has quite good correlation with diaphragm, heart, and lung. PMID:27382308
A four-dimensional data assimilation (FDDA) scheme based on Newtonian relaxation or nudging has been developed and evaluated in the Pennsylvania State University/National Center for Atmospheric Research (PSU/NCAR) Limited-Area Mesoscale Model. t was shown in Part I of this study ...
Sarrut, David; Boldea, Vlad; Miguet, Serge; Ginestet, Chantal
2006-03-15
Purpose: We propose to simulate an artificial four-dimensional (4-D) CT image of the thorax during breathing. It is performed by deformable registration of two CT scans acquired at inhale and exhale breath-hold. Materials and methods: Breath-hold images were acquired with the ABC (Active Breathing Coordinator) system. Dense deformable registrations were performed. The method was a minimization of the sum of squared differences (SSD) using an approximated second-order gradient. Gaussian and linear-elastic vector field regularizations were compared. A new preprocessing step, called a priori lung density modification (APLDM), was proposed to take into account lung density changes due to inspiration. It consisted of modulating the lung densities in one image according to the densities in the other, in order to make them comparable. Simulated 4-D images were then built by vector field interpolation and image resampling of the two initial CT images. A variation in the lung density was taken into account to generate intermediate artificial CT images. The Jacobian of the deformation was used to compute voxel values in Hounsfield units. The accuracy of the deformable registration was assessed by the spatial correspondence of anatomic landmarks located by experts. Results: APLDM produced statistically significantly better results than the reference method (registration without APLDM preprocessing). The mean (and standard deviation) of distances between automatically found landmark positions and landmarks set by experts were 2.7(1.1) mm with APLDM, and 6.3(3.8) mm without. Interexpert variability was 2.3(1.2) mm. The differences between Gaussian and linear elastic regularizations were not statistically significant. In the second experiment using 4-D images, the mean difference between automatic and manual landmark positions for intermediate CT images was 2.6(2.0) mm. Conclusion: The generation of 4-D CT images by deformable registration of inhale and exhale CT images is
Vinogradskiy, Yevgeniy Y.; Balter, Peter; Followill, David S.; Alvarez, Paola E.; White, R. Allen; Starkschall, George
2009-11-15
Purpose: Four-dimensional (4D) dose calculation algorithms, which explicitly incorporate respiratory motion in the calculation of doses, have the potential to improve the accuracy of dose calculations in thoracic treatment planning; however, they generally require greater computing power and resources than currently used for three-dimensional (3D) dose calculations. The purpose of this work was to quantify the increase in accuracy of 4D dose calculations versus 3D dose calculations. Methods: The accuracy of each dose calculation algorithm was assessed using measurements made with two phantoms. Specifically, the authors used a rigid moving anthropomorphic thoracic phantom and an anthropomorphic thoracic phantom with a deformable lung insert. To incorporate a clinically relevant range of scenarios, they programed the phantoms to move and deform with two motion patterns: A sinusoidal motion pattern and an irregular motion pattern that was extracted from an actual patient's breathing profile. For each combination of phantom and motion pattern, three plans were created: A single-beam plan, a multiple-beam plan, and an intensity-modulated radiation therapy plan. Doses were calculated using 4D dose calculation methods as well as conventional 3D dose calculation methods. The rigid moving and deforming phantoms were irradiated according to the three treatment plans and doses were measured using thermoluminescent dosimeters (TLDs) and radiochromic film. The accuracy of each dose calculation algorithm was assessed using measured-to-calculated TLD doses and a {gamma} analysis. Results: No significant differences were observed between the measured-to-calculated TLD ratios among 4D and 3D dose calculations. The {gamma} results revealed that 4D dose calculations had significantly greater percentage of pixels passing the 5%/3 mm criteria than 3D dose calculations. Conclusions: These results indicate no significant differences in the accuracy between the 4D and the 3D dose
Lu Wei; Parikh, Parag J.; El Naqa, Issam M.; Nystrom, Michelle M.; Hubenschmidt, James P.; Wahab, Sasha H.; Mutic, Sasa; Singh, Anurag K.; Christensen, Gary E.; Bradley, Jeffrey D.; Low, Daniel A.
2005-04-01
We have developed a four-dimensional computed tomography (4D CT) technique for mapping breathing motion in radiotherapy treatment planning. A multislice CT scanner (1.5 mm slices) operated in cine mode was used to acquire 12 contiguous slices in each couch position for 15 consecutive scans (0.5 s rotation, 0.25 s between scans) while the patient underwent simultaneous quantitative spirometry measurements to provide a sorting metric. The spirometry-sorted scans were used to reconstruct a 4D data set. A critical factor for 4D CT is quantifying the reconstructed data set quality which we measure by correlating the metric used relative to internal-object motion. For this study, the internal air content within the lung was used as a surrogate for internal motion measurements. Thresholding and image morphological operations were applied to delineate the air-containing tissues (lungs, trachea) from each CT slice. The Hounsfield values were converted to the internal air content (V). The relationship between the air content and spirometer-measured tidal volume ({nu}) was found to be quite linear throughout the lungs and was used to estimate the overall accuracy and precision of tidal volume-sorted 4D CT. Inspection of the CT-scan air content as a function of tidal volume showed excellent correlations (typically r>0.99) throughout the lung volume. Because of the discovered linear relationship, the ratio of internal air content to tidal volume was indicative of the fraction of air change in each couch position. Theoretically, due to air density differences within the lung and in room, the sum of these ratios would equal 1.11. For 12 patients, the mean value was 1.08{+-}0.06, indicating the high quality of spirometry-based image sorting. The residual of a first-order fit between {nu} and V was used to estimate the process precision. For all patients, the precision was better than 8%, with a mean value of 5.1%{+-}1.9%. This quantitative analysis highlights the value of using
SU-C-207-01: Four-Dimensional Inverse Geometry Computed Tomography: Concept and Its Validation
Kim, K; Kim, D; Kim, T; Kang, S; Cho, M; Shin, D; Suh, T
2015-06-15
Purpose: In past few years, the inverse geometry computed tomography (IGCT) system has been developed to overcome shortcomings of a conventional computed tomography (CT) system such as scatter problem induced from large detector size and cone-beam artifact. In this study, we intend to present a concept of a four-dimensional (4D) IGCT system that has positive aspects above all with temporal resolution for dynamic studies and reduction of motion artifact. Methods: Contrary to conventional CT system, projection data at a certain angle in IGCT was a group of fractionated narrow cone-beam projection data, projection group (PG), acquired from multi-source array which have extremely short time gap of sequential operation between each of sources. At this, for 4D IGCT imaging, time-related data acquisition parameters were determined by combining multi-source scanning time for collecting one PG with conventional 4D CBCT data acquisition sequence. Over a gantry rotation, acquired PGs from multi-source array were tagged time and angle for 4D image reconstruction. Acquired PGs were sorted into 10 phase and image reconstructions were independently performed at each phase. Image reconstruction algorithm based upon filtered-backprojection was used in this study. Results: The 4D IGCT had uniform image without cone-beam artifact on the contrary to 4D CBCT image. In addition, the 4D IGCT images of each phase had no significant artifact induced from motion compared with 3D CT. Conclusion: The 4D IGCT image seems to give relatively accurate dynamic information of patient anatomy based on the results were more endurable than 3D CT about motion artifact. From this, it will be useful for dynamic study and respiratory-correlated radiation therapy. This work was supported by the Industrial R&D program of MOTIE/KEIT [10048997, Development of the core technology for integrated therapy devices based on real-time MRI guided tumor tracking] and the Mid-career Researcher Program (2014R1A2A1A
Park, Justin C.; Kim, Jin Sung; Park, Sung Ho; Liu, Zhaowei; Song, Bongyong; Song, William Y.
2013-12-15
Purpose: Utilization of respiratory correlated four-dimensional cone-beam computed tomography (4DCBCT) has enabled verification of internal target motion and volume immediately prior to treatment. However, with current standard CBCT scan, 4DCBCT poses challenge for reconstruction due to the fact that multiple phase binning leads to insufficient number of projection data to reconstruct and thus cause streaking artifacts. The purpose of this study is to develop a novel 4DCBCT reconstruction algorithm framework called motion-map constrained image reconstruction (MCIR), that allows reconstruction of high quality and high phase resolution 4DCBCT images with no more than the imaging dose as well as projections used in a standard free breathing 3DCBCT (FB-3DCBCT) scan.Methods: The unknown 4DCBCT volume at each phase was mathematically modeled as a combination of FB-3DCBCT and phase-specific update vector which has an associated motion-map matrix. The motion-map matrix, which is the key innovation of the MCIR algorithm, was defined as the matrix that distinguishes voxels that are moving from stationary ones. This 4DCBCT model was then reconstructed with compressed sensing (CS) reconstruction framework such that the voxels with high motion would be aggressively updated by the phase-wise sorted projections and the voxels with less motion would be minimally updated to preserve the FB-3DCBCT. To evaluate the performance of our proposed MCIR algorithm, we evaluated both numerical phantoms and a lung cancer patient. The results were then compared with the (1) clinical FB-3DCBCT reconstructed using the FDK, (2) 4DCBCT reconstructed using the FDK, and (3) 4DCBCT reconstructed using the well-known prior image constrained compressed sensing (PICCS).Results: Examination of the MCIR algorithm showed that high phase-resolved 4DCBCT with sets of up to 20 phases using a typical FB-3DCBCT scan could be reconstructed without compromising the image quality. Moreover, in comparison with
Shieh, Chun-Chien; Kipritidis, John; O’Brien, Ricky T; Cooper, Benjamin J; Kuncic, Zdenka; Keall, Paul J
2015-01-01
Total-variation (TV) minimization reconstructions can significantly reduce noise and streaks in thoracic four-dimensional cone-beam computed tomography (4D CBCT) images compared to the Feldkamp-Davis-Kress (FDK) algorithm currently used in practice. TV minimization reconstructions are, however, prone to over-smoothing anatomical details and are also computationally inefficient. The aim of this study is to demonstrate a proof of concept that these disadvantages can be overcome by incorporating the general knowledge of the thoracic anatomy via anatomy segmentation into the reconstruction. The proposed method, referred as the anatomical-adaptive image regularization (AAIR) method, utilizes the adaptive-steepest-descent projection-onto-convex-sets (ASD-POCS) framework, but introduces an additional anatomy segmentation step in every iteration. The anatomy segmentation information is implemented in the reconstruction using a heuristic approach to adaptively suppress over-smoothing at anatomical structures of interest. The performance of AAIR depends on parameters describing the weighting of the anatomy segmentation prior and segmentation threshold values. A sensitivity study revealed that the reconstruction outcome is not sensitive to these parameters as long as they are chosen within a suitable range. AAIR was validated using a digital phantom and a patient scan, and was compared to FDK, ASD-POCS, and the prior image constrained compressed sensing (PICCS) method. For the phantom case, AAIR reconstruction was quantitatively shown to be the most accurate as indicated by the mean absolute difference and the structural similarity index. For the patient case, AAIR resulted in the highest signal-to-noise ratio (i.e. the lowest level of noise and streaking) and the highest contrast-to-noise ratios for the tumor and the bony anatomy (i.e. the best visibility of anatomical details). Overall, AAIR was much less prone to over-smoothing anatomical details compared to ASD-POCS, and
NASA Astrophysics Data System (ADS)
Shieh, Chun-Chien; Kipritidis, John; O'Brien, Ricky T.; Cooper, Benjamin J.; Kuncic, Zdenka; Keall, Paul J.
2015-01-01
Total-variation (TV) minimization reconstructions can significantly reduce noise and streaks in thoracic four-dimensional cone-beam computed tomography (4D CBCT) images compared to the Feldkamp-Davis-Kress (FDK) algorithm currently used in practice. TV minimization reconstructions are, however, prone to over-smoothing anatomical details and are also computationally inefficient. The aim of this study is to demonstrate a proof of concept that these disadvantages can be overcome by incorporating the general knowledge of the thoracic anatomy via anatomy segmentation into the reconstruction. The proposed method, referred as the anatomical-adaptive image regularization (AAIR) method, utilizes the adaptive-steepest-descent projection-onto-convex-sets (ASD-POCS) framework, but introduces an additional anatomy segmentation step in every iteration. The anatomy segmentation information is implemented in the reconstruction using a heuristic approach to adaptively suppress over-smoothing at anatomical structures of interest. The performance of AAIR depends on parameters describing the weighting of the anatomy segmentation prior and segmentation threshold values. A sensitivity study revealed that the reconstruction outcome is not sensitive to these parameters as long as they are chosen within a suitable range. AAIR was validated using a digital phantom and a patient scan and was compared to FDK, ASD-POCS and the prior image constrained compressed sensing (PICCS) method. For the phantom case, AAIR reconstruction was quantitatively shown to be the most accurate as indicated by the mean absolute difference and the structural similarity index. For the patient case, AAIR resulted in the highest signal-to-noise ratio (i.e. the lowest level of noise and streaking) and the highest contrast-to-noise ratios for the tumor and the bony anatomy (i.e. the best visibility of anatomical details). Overall, AAIR was much less prone to over-smoothing anatomical details compared to ASD-POCS and did
Wang, Wei; Li, Jianbin; Zhang, Yingjie; Shao, Qian; Xu, Min; Fan, Tingyong; Wang, Jinzhi
2016-01-01
Background and purpose To investigate the definition of planning target volumes (PTVs) based on four-dimensional computed tomography (4DCT) compared with conventional PTV definition and PTV definition using asymmetrical margins for thoracic primary esophageal cancer. Materials and methods Forty-three patients with esophageal cancer underwent 3DCT and 4DCT simulation scans during free breathing. The motions of primary tumors located in the proximal (group A), middle (group B), and distal (group C) thoracic esophagus were obtained from the 4DCT scans. PTV3D was defined on 3DCT using the tumor motion measured based on 4DCT, PTV conventional (PTVconv) was defined on 3DCT by adding a 1.0 cm margin to the clinical target volume, and PTV4D was defined as the union of the target volumes contoured on the ten phases of the 4DCT images. The centroid positions, volumetric differences, and dice similarity coefficients were evaluated for all PTVs. Results The median centroid shifts between PTV3D and PTV4D and between PTVconv and PTV4D in all three dimensions were <0.3 cm for the three groups. The median size ratios of PTV4D to PTV3D were 0.80, 0.88, and 0.71, and PTV4D to PTVconv were 0.67, 0.73, and 0.76 (χ2=−3.18, −2.98, and −3.06; P=0.001, 0.003, and 0.002) for groups A, B, and C, respectively. The dice similarity coefficients were 0.87, 0.90, and 0.81 between PTV4D and PTV3D and 0.80, 0.84, and 0.83 between PTV4D and PTVconv (χ2 =−3.18, −2.98, and −3.06; P=0.001, 0.003, and 0.002) for groups A, B, and C, respectively. The difference between the degree of inclusion of PTV4D in PTV3D and that of PTV4D in PTVconv was <2% for all groups. Compared with PTVconv, the amount of irradiated normal tissue for PTV3D was decreased by 11.81% and 11.86% in groups A and B, respectively, but was increased by 2.93% in group C. Conclusion For proximal and middle esophageal cancer, 3DCT-based PTV using asymmetrical margins provides good coverage of PTV4D; however, for distal
Kipritidis, John Keall, Paul J.; Hugo, Geoffrey; Weiss, Elisabeth; Williamson, Jeffrey
2015-03-15
Purpose: Adaptive ventilation guided radiation therapy could minimize the irradiation of healthy lung based on repeat lung ventilation imaging (VI) during treatment. However the efficacy of adaptive ventilation guidance requires that interfraction (e.g., week-to-week), ventilation changes are not washed out by intrafraction (e.g., pre- and postfraction) changes, for example, due to patient breathing variability. The authors hypothesize that patients undergoing lung cancer radiation therapy exhibit larger interfraction ventilation changes compared to intrafraction function changes. To test this, the authors perform the first comparison of interfraction and intrafraction lung VI pairs using four-dimensional cone beam CT ventilation imaging (4D-CBCT VI), a novel technique for functional lung imaging. Methods: The authors analyzed a total of 215 4D-CBCT scans acquired for 19 locally advanced non-small cell lung cancer (LA-NSCLC) patients over 4–6 weeks of radiation therapy. This set of 215 scans was sorted into 56 interfraction pairs (including first day scans and each of treatment weeks 2, 4, and 6) and 78 intrafraction pairs (including pre/postfraction scans on the same-day), with some scans appearing in both sets. VIs were obtained from the Jacobian determinant of the transform between the 4D-CBCT end-exhale and end-inhale images after deformable image registration. All VIs were deformably registered to their corresponding planning CT and normalized to account for differences in breathing effort, thus facilitating image comparison in terms of (i) voxelwise Spearman correlations, (ii) mean image differences, and (iii) gamma pass rates for all interfraction and intrafraction VI pairs. For the side of the lung ipsilateral to the tumor, we applied two-sided t-tests to determine whether interfraction VI pairs were more different than intrafraction VI pairs. Results: The (mean ± standard deviation) Spearman correlation for interfraction VI pairs was r{sup -}{sub Inter
Yamashiro, Tsuneo; Moriya, Hiroshi; Tsubakimoto, Maho; Matsuoka, Shin; Murayama, Sadayuki
2016-01-01
Purpose Four-dimensional dynamic-ventilation computed tomography (CT) imaging demonstrates continuous movement of the airways and lungs, which cannot be depicted with conventional CT. We aimed to investigate continuous changes in lung density and airway dimensions and to assess the correlation with spirometric values in smokers. Materials and methods This retrospective study was approved by the Institutional Review Board, and informed consent was waived. Twenty-one smokers including six patients with COPD underwent four-dimensional dynamic-ventilation CT during free breathing (160 mm in length). The mean lung density (MLD) of the scanned lung and luminal areas (Ai) of fixed points in the trachea and the right proximal bronchi (main bronchus, upper bronchus, bronchus intermedius, and lower bronchus) were continuously measured. Concordance between the time curve of the MLD and that of the airway Ai values was expressed by cross-correlation coefficients. The associations between these quantitative measurements and the forced expiratory volume in 1 second/forced vital capacity (FEV1/FVC) values were assessed by Spearman’s rank correlation analysis. Results On the time curve for the MLD, the Δ-MLD1.05 values between the peak inspiratory frame to the later third frame (1.05 seconds later) were strongly correlated with the FEV1/FVC (ρ=0.76, P<0.0001). The cross-correlation coefficients between the airway Ai and MLD values were significantly correlated with the FEV1/FVC (ρ=−0.56 to −0.66, P<0.01), except for the right upper bronchus. This suggested that the synchrony between the airway and lung movement was lost in patients with severe airflow limitation. Conclusion Respiratory changes in the MLD and synchrony between the airway Ai and the MLD measured with dynamic-ventilation CT were correlated with patient’s spirometric values. PMID:27110108
Wang He; Garden, Adam S.; Zhang Lifei; Wei Xiong; Ahamad, Anesa; Kuban, Deborah A.; Komaki, Ritsuko; O'Daniel, Jennifer; Zhang Yongbin; Mohan, Radhe; Dong Lei
2008-09-01
Purpose: Auto-propagation of anatomic regions of interest from the planning computed tomography (CT) scan to the daily CT is an essential step in image-guided adaptive radiotherapy. The goal of this study was to quantitatively evaluate the performance of the algorithm in typical clinical applications. Methods and Materials: We had previously adopted an image intensity-based deformable registration algorithm to find the correspondence between two images. In the present study, the regions of interest delineated on the planning CT image were mapped onto daily CT or four-dimensional CT images using the same transformation. Postprocessing methods, such as boundary smoothing and modification, were used to enhance the robustness of the algorithm. Auto-propagated contours for 8 head-and-neck cancer patients with a total of 100 repeat CT scans, 1 prostate patient with 24 repeat CT scans, and 9 lung cancer patients with a total of 90 four-dimensional CT images were evaluated against physician-drawn contours and physician-modified deformed contours using the volume overlap index and mean absolute surface-to-surface distance. Results: The deformed contours were reasonably well matched with the daily anatomy on the repeat CT images. The volume overlap index and mean absolute surface-to-surface distance was 83% and 1.3 mm, respectively, compared with the independently drawn contours. Better agreement (>97% and <0.4 mm) was achieved if the physician was only asked to correct the deformed contours. The algorithm was also robust in the presence of random noise in the image. Conclusion: The deformable algorithm might be an effective method to propagate the planning regions of interest to subsequent CT images of changed anatomy, although a final review by physicians is highly recommended.
Four-dimensional electron microscopy.
Zewail, Ahmed H
2010-04-01
The discovery of the electron over a century ago and the realization of its dual character have given birth to one of the two most powerful imaging instruments: the electron microscope. The electron microscope's ability to resolve three-dimensional (3D) structures on the atomic scale is continuing to affect different fields, including materials science and biology. In this Review, we highlight recent developments and inventions made by introducing the fourth dimension of time in electron microscopy. Today, ultrafast electron microscopy (4D UEM) enables a resolution that is 10 orders of magnitude better than that of conventional microscopes, which are limited by the video-camera rate of recording. After presenting the central concept involved, that of single-electron stroboscopic imaging, we discuss prototypical applications, which include the visualization of complex structures when unfolding on different length and time scales. The developed UEM variant techniques are several, and here we illucidate convergent-beam and near-field imaging, as well as tomography and scanning-pulse microscopy. We conclude with current explorations in imaging of nanomaterials and biostructures and an outlook on possible future directions in space-time, 4D electron microscopy. PMID:20378810
Four-Dimensional Electron Microscopy
NASA Astrophysics Data System (ADS)
Zewail, Ahmed H.
2010-04-01
The discovery of the electron over a century ago and the realization of its dual character have given birth to one of the two most powerful imaging instruments: the electron microscope. The electron microscope’s ability to resolve three-dimensional (3D) structures on the atomic scale is continuing to affect different fields, including materials science and biology. In this Review, we highlight recent developments and inventions made by introducing the fourth dimension of time in electron microscopy. Today, ultrafast electron microscopy (4D UEM) enables a resolution that is 10 orders of magnitude better than that of conventional microscopes, which are limited by the video-camera rate of recording. After presenting the central concept involved, that of single-electron stroboscopic imaging, we discuss prototypical applications, which include the visualization of complex structures when unfolding on different length and time scales. The developed UEM variant techniques are several, and here we illucidate convergent-beam and near-field imaging, as well as tomography and scanning-pulse microscopy. We conclude with current explorations in imaging of nanomaterials and biostructures and an outlook on possible future directions in space-time, 4D electron microscopy.
Haitao, L; Dajun, Y; Kaifa, W; Xiuwu, B; Jiansen, S; Zongchen, Y
2005-06-30
The aim of this study was to explore the spatiotemporal development of cerebral oedema in the early stage of severe burn (50% TBSA, third degree), using a four-dimensional (4D) mathematical model. Twenty-six male mongrel dogs were randomly divided into control and 6, 12, 18, and 24 post-burn hour (PBH) groups. The manifestation of magnetic resonance imaging (MRI) and histopathology, changes of brain water content, and intracranial pressure were observed in each group respectively. A 4D mathematical model was established on the basis of the results of MRI scanning. Two turning points (6 and 18 PBH) and three phases of pathological change were displayed by the 4D mathematical model of cerebral oedema in the early stage of severe burn. The first phase was in the subclinical period, and effective treatment should therefore be performed as quickly as possible in order to prevent deterioration of post-burn cerebral oedema. The second phase (6-18 PBH), with pathological characteristics of cytotoxic cerebral oedema, was in the apoptosis period. The third stage (18-24 PBH) was the danger period of cerebral oedema. Intracranial pressure increased rapidly owing to the limitation of the cranial cavity. As a result, cerebral hernia could easily occur. An S-shape curve in the pathological process of cerebral oedema occurred in the early post-burn stage following severe burn. PMID:21990986
Ishimura, Shota; Kikuchi, Kazuro
2015-03-01
We apply the eight-state trellis-coded modulation (TCM) using signal constellations of four-dimensional M-ary quadrature-amplitude modulation (4D-MQAM) to optical communication systems for the first time to our knowledge. In the TCM scheme, the free distance of the trellis diagram is equal to the minimum distance between constellation points in partitioned subsets, which enlarges the coding gain effectively. In fact, its asymptotic power efficiency is 3-dB larger than that of the set-partitioned 4D-MQAM (SP-4D-MQAM) format, while their spectral efficiencies are the same. Such theoretical predictions are confirmed through computer simulations on eight-state TCM with constellations of 4D-4QAM (i.e., 4D quadrature phase-shift keying: 4D-QPSK) and 4D-16QAM. In particular, eight-state TCM with 4D-QPSK constellations is practically important because of its simple encoder structure, relatively low computational cost, and high coding gain against dual-polarization QPSK (DP-QPSK) and SP-4D-QPSK. Through measurements of its bit-error rate (BER) performance, we confirm that the coding gain against DP-QPSK is about 3 dB at BER=10(-3). PMID:25836886
NASA Astrophysics Data System (ADS)
Happel, Christoph M.; Thommes, Jan; Thrane, Lars; Männer, Jörg; Ortmaier, Tobias; Heimann, Bodo; Yelbuz, Talat Mesud
2011-09-01
We introduce a new method of rotational image acquisition for four-dimensional (4D) optical coherence tomography (OCT) of beating embryonic chick hearts. The rotational axis and the central A-scan of the OCT are identical. An out-of-phase image sequence covering multiple heartbeats is acquired at every angle of an incremental rotation of the deflection mirrors of the OCT system. Image acquisition is accomplished after a rotation of 180°. Comparison of a displayed live M-mode of the central A-scan with a reference M-mode allows instant detection of translational movements of the embryo. For calculation of 4D data sets, we apply an image-based retrospective gating algorithm using the phase information of the common central A-scan present in all acquired images. This leads to cylindrical three-dimensional data sets for every time step of the cardiac cycle that can be used for 4D visualization. We demonstrate this approach and provide a video of a beating Hamburger and Hamilton stage 16 embryonic chick heart generated from a 4D OCT data set using rotational image acquisition.
Haitao, L.; Dajun, Y.; Kaifa, W.; Xiuwu, B.; Jiansen, S.; Zongchen, Y.
2005-01-01
Summary The aim of this study was to explore the spatiotemporal development of cerebral oedema in the early stage of severe burn (50% TBSA, third degree), using a four-dimensional (4D) mathematical model. Twenty-six male mongrel dogs were randomly divided into control and 6, 12, 18, and 24 post-burn hour (PBH) groups. The manifestation of magnetic resonance imaging (MRI) and histopathology, changes of brain water content, and intracranial pressure were observed in each group respectively. A 4D mathematical model was established on the basis of the results of MRI scanning. Two turning points (6 and 18 PBH) and three phases of pathological change were displayed by the 4D mathematical model of cerebral oedema in the early stage of severe burn. The first phase was in the subclinical period, and effective treatment should therefore be performed as quickly as possible in order to prevent deterioration of post-burn cerebral oedema. The second phase (6-18 PBH), with pathological characteristics of cytotoxic cerebral oedema, was in the apoptosis period. The third stage (18-24 PBH) was the danger period of cerebral oedema. Intracranial pressure increased rapidly owing to the limitation of the cranial cavity. As a result, cerebral hernia could easily occur. An S-shape curve in the pathological process of cerebral oedema occurred in the early post-burn stage following severe burn. PMID:21990986
NASA Astrophysics Data System (ADS)
Schwinger, J.; Elbern, H.
2010-09-01
Chemical state analyses of the atmosphere based on data assimilation may be degraded by inconsistent covariances of background and observation errors. An efficient method to calculate consistency diagnostics for background and observation errors in observation space is applied to analyses of the four-dimensional variational stratospheric chemistry data assimilation system SACADA (Synoptic Analysis of Chemical Constituents by Advanced Data Assimilation). A background error covariance model for the assimilation of Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) ozone retrievals is set up and optimized. It is shown that a significant improvement of the assimilation system performance is attained through the use of this covariance model compared to a simple covariance formulation, which assumes background errors to be a fixed fraction of the field value. The forecast skill, measured by the distance between the model forecast and MIPAS observations, is shown to improve. Further, an evaluation of analyses with independent data from the Halogen Observation Experiment (HALOE), the Stratospheric Aerosol and Gas Experiment II (SAGE II), and ozone sondes reveals that the standard deviation of ozone analyses with respect to these instruments is reduced throughout the middle stratosphere. Compared to the impact of background error variances on analysis quality, it is found that the precise specification of spatial background error correlations appears to be less critical if observations are spatially and temporally dense. Results indicate that ozone forecast errors of a state of the art stratospheric chemistry assimilation system are of the same order of magnitude as MIPAS observation errors.
Sun, Jingya; Melnikov, Vasily A; Khan, Jafar I; Mohammed, Omar F
2015-10-01
In the fields of photocatalysis and photovoltaics, ultrafast dynamical processes, including carrier trapping and recombination on material surfaces, are among the key factors that determine the overall energy conversion efficiency. A precise knowledge of these dynamical events on the nanometer (nm) and femtosecond (fs) scales was not accessible until recently. The only way to access such fundamental processes fully is to map the surface dynamics selectively in real space and time. In this study, we establish a second generation of four-dimensional scanning ultrafast electron microscopy (4D S-UEM) and demonstrate the ability to record time-resolved images (snapshots) of material surfaces with 650 fs and ∼5 nm temporal and spatial resolutions, respectively. In this method, the surface of a specimen is excited by a clocking optical pulse and imaged using a pulsed primary electron beam as a probe pulse, generating secondary electrons (SEs), which are emitted from the surface of the specimen in a manner that is sensitive to the local electron/hole density. This method provides direct and controllable information regarding surface dynamics. We clearly demonstrate how the surface morphology, grains, defects, and nanostructured features can significantly impact the overall dynamical processes on the surface of photoactive-materials. In addition, the ability to access two regimes of dynamical probing in a single experiment and the energy loss of SEs in semiconductor-nanoscale materials will also be discussed. PMID:26722888
Shirato, Hiroki . E-mail: hshirato@radi.med.hokudai.ac.jp; Suzuki, Keishiro; Sharp, Gregory C.; Fujita, Katsuhisa R.T.; Onimaru, Rikiya; Fujino, Masaharu; Kato, Norio; Osaka, Yasuhiro; Kinoshita, Rumiko; Taguchi, Hiroshi; Onodera, Shunsuke; Miyasaka, Kazuo
2006-03-15
Background: To reduce the uncertainty of registration for lung tumors, we have developed a four-dimensional (4D) setup system using a real-time tumor-tracking radiotherapy system. Methods and Materials: During treatment planning and daily setup in the treatment room, the trajectory of the internal fiducial marker was recorded for 1 to 2 min at the rate of 30 times per second by the real-time tumor-tracking radiotherapy system. To maximize gating efficiency, the patient's position on the treatment couch was adjusted using the 4D setup system with fine on-line remote control of the treatment couch. Results: The trajectory of the marker detected in the 4D setup system was well visualized and used for daily setup. Various degrees of interfractional and intrafractional changes in the absolute amplitude and speed of the internal marker were detected. Readjustments were necessary during each treatment session, prompted by baseline shifting of the tumor position. Conclusion: The 4D setup system was shown to be useful for reducing the uncertainty of tumor motion and for increasing the efficiency of gated irradiation. Considering the interfractional and intrafractional changes in speed and amplitude detected in this study, intercepting radiotherapy is the safe and cost-effective method for 4D radiotherapy using real-time tracking technology.
Osuji, Leo C; Ayolagha, G; Obute, G C; Ohabuike, H C
2007-09-01
Four-dimensional (4D) seismic exploration, an improved geophysical technique for hydrocarbon-data acquisition, was applied for the first time in the Nembe Creek prospect area of Nigeria. The affected soils were slightly alkaline in situ when wet (pH 7.2), but extremely acidic when dry (pH 3.0). The organic carbon content (4.6-26.8%) and other physicochemical properties of soils and water (N, P, and heavy-metal contents, etc.) were higher than the baseline values obtained in 2001 before seismic profiling. Most values also exceeded the baseline compliance standards of the Department of Petroleum Resources (DPR), the World Health Organization (WHO), and the Federal Environmental Protection Agency (FEPA). Rehabilitation of the affected areas was achieved by stabilizing the mangrove floor by liming and appropriate application of nutrients, followed by replanting the cut seismic lines over a distance of 1,372 km with different mangrove species, including juvenile Rhizophora racemosa, R. mangle, and Avicennia species, which were transferred from nursery points. Quicker post-operational intervention is recommended for future 4D surveys, because the time lag between the end of seismic activity and post-impact investigation is critical in determining the relationship between activity and impact: the longer the intervening period, the more mooted the interaction. PMID:17886833
Yamashita, Hideomi; Okuma, Kae; Tada, Keiichiro; Shiraishi, Kenshiro; Takahashi, Wataru; Shibata-Mobayashi, Shino; Sakumi, Akira; Saotome, Naoya; Haga, Akihiro; Onoe, Tsuyoshi; Ino, Kenji; Akahane, Masaaki; Ohtomo, Kuni; Nakagawa, Keiichi
2012-10-01
Purpose: To study the three-dimensional movement of internal tumor bed fiducial and breast skin markers, using 320-multislice computed tomography (CT); and to analyze intrafractional errors for breast cancer patients undergoing breast irradiation. Methods and Materials: This study examined 280 markers on the skin of the breast (200 markers) and on the primary tumor bed (80 markers) of 20 patients treated by external-beam photon radiotherapy. Motion assessment was analyzed in 41 respiratory phases during 20 s of cine CT in the radiotherapy position. To assess intrafractional errors resulting from respiratory motion, four-dimensional CT scans were acquired for 20 patients. Results: Motion in the anterior-posterior (A/P) and superior-inferior (S/I) directions showed a strong correlation (|r| > 0.7) with the respiratory curve for most markers (79% and 70%, respectively). The average marker displacements between maximum and minimum value during 20 s for the 200 breast skin metal markers were 1.1 {+-} 0.3 mm, 2.1 {+-} 0.6 mm, and 1.6 {+-} 0.4 mm in the left-right, A/P, and S/I directions, respectively. For the 80 tumor bed clips, displacements were 0.9 {+-} 0.2 mm in left-right, 1.7 {+-} 0.5 mm in A/P, and 1.1 {+-} 0.3 mm in S/I. There was no significant difference in the motion between breast quadrant regions or between the primary site and the other regions. Conclusions: Motion in primary breast tumors was evaluated with 320-multislice CT. Very little change was detected during individual radiation treatment fractions.
Zhang Xiaodong; Zhao Kuaile; Guerrero, Thomas M.; Mcguire, Sean E.; Yaremko, Brian; Komaki, Ritsuko; Cox, James D.; Hui Zhouguang; Li Yupeng; Newhauser, Wayne D.; Mohan, Radhe; Liao Zhongxing
2008-09-01
Purpose: To compare three-dimensional (3D) and four-dimensional (4D) computed tomography (CT)-based treatment plans for proton therapy or intensity-modulated radiation therapy (IMRT) for esophageal cancer in terms of doses to the lung, heart, and spinal cord and variations in target coverage and normal tissue sparing. Methods and Materials: The IMRT and proton plans for 15 patients with distal esophageal cancer were designed from the 3D average CT scans and then recalculated on 10 4D CT data sets. Dosimetric data were compared for tumor coverage and normal tissue sparing. Results: Compared with IMRT, median lung volumes exposed to 5, 10, and 20 Gy and mean lung dose were reduced by 35.6%, 20.5%, 5.8%, and 5.1 Gy for a two-beam proton plan and by 17.4%, 8.4%, 5%, and 2.9 Gy for a three-beam proton plan. The greater lung sparing in the two-beam proton plan was achieved at the expense of less conformity to the target (conformity index [CI], 1.99) and greater irradiation of the heart (heart-V40, 41.8%) compared with the IMRT plan(CI, 1.55, heart-V40, 35.7%) or the three-beam proton plan (CI, 1.46, heart-V40, 27.7%). Target coverage differed by more than 2% between the 3D and 4D plans for patients with substantial diaphragm motion in the three-beam proton and IMRT plans. The difference in spinal cord maximum dose between 3D and 4D plans could exceed 5 Gy for the proton plans partly owing to variations in stomach gas filling. Conclusions: Proton therapy provided significantly better sparing of lung than did IMRT. Diaphragm motion and stomach gas-filling must be considered in evaluating target coverage and cord doses.
Geld, Ylanga G. van der; Triest, Baukelien van; Verbakel, Wilko; Soernsen de Koste, John R. van; Senan, Suresh; Slotman, Ben J.; Lagerwaard, Frank J.
2008-11-15
Purpose: To compare conformal radiotherapy (CRT), intensity-modulated radiotherapy (IMRT), and respiration-gated radiotherapy (RGRT) planning techniques for pancreatic cancer. All target volumes were determined using four-dimensional computed tomography scans (4D CT). Methods and Materials: The pancreatic tumor and enlarged regional lymph nodes were contoured on all 10 phases of a planning 4D CT scan for 10 patients, and the planning target volumes (PTV{sub allphases}) were generated. Three consecutive respiratory phases for RGRT delivery in both inspiration and expiration were identified, and the corresponding PTVs (PTV{sub inspiration} and PTV{sub expiration}) and organ at risk volumes created. Treatment plans using CRT and IMRT, with and without RGRT, were created for each PTV. Results: Compared with the CRT plans, IMRT significantly reduced the mean volume of right kidney exposed to 20 Gy from 27.7% {+-} 17.7% to 16.0% {+-} 18.2% (standard deviation) (p < 0.01), but this was not achieved for the left kidney (11.1% {+-} 14.2% to 5.7% {+-} 6.5%; p = 0.1). The IMRT plans also reduced the mean gastric, hepatic, and small bowel doses (p < 0.01). No additional reductions in the dose to the kidneys or other organs at risk were seen when RGRT plans were combined with either CRT or IMRT, and the findings for RGRT in end-expiration and end-inspiration were similar. Conclusion: 4D CT-based IMRT plans for pancreatic tumors significantly reduced the radiation doses to the right kidney, liver, stomach, and small bowel compared with CRT plans. The additional dosimetric benefits from RGRT appear limited in this setting.
Malinowski, Kathleen T.; Pantarotto, Jason R.; Senan, Suresh
2010-08-01
Purpose: To investigate the feasibility of modeling Stage III lung cancer tumor and node positions from anatomical surrogates. Methods and Materials: To localize their centroids, the primary tumor and lymph nodes from 16 Stage III lung cancer patients were contoured in 10 equal-phase planning four-dimensional (4D) computed tomography (CT) image sets. The centroids of anatomical respiratory surrogates (carina, xyphoid, nipples, mid-sternum) in each image set were also localized. The correlations between target and surrogate positions were determined, and ordinary least-squares (OLS) and partial least-squares (PLS) regression models based on a subset of respiratory phases (three to eight randomly selected) were created to predict the target positions in the remaining images. The three-phase image sets that provided the best predictive information were used to create models based on either the carina alone or all surrogates. Results: The surrogate most correlated with target motion varied widely. Depending on the number of phases used to build the models, mean OLS and PLS errors were 1.0 to 1.4 mm and 0.8 to 1.0 mm, respectively. Models trained on the 0%, 40%, and 80% respiration phases had mean ({+-} standard deviation) PLS errors of 0.8 {+-} 0.5 mm and 1.1 {+-} 1.1 mm for models based on all surrogates and carina alone, respectively. For target coordinates with motion >5 mm, the mean three-phase PLS error based on all surrogates was 1.1 mm. Conclusions: Our results establish the feasibility of inferring primary tumor and nodal motion from anatomical surrogates in 4D CT scans of Stage III lung cancer. Using inferential modeling to decrease the processing time of 4D CT scans may facilitate incorporation of patient-specific treatment margins.
Nakamoto, Takahiro; Arimura, Hidetaka; Nakamura, Katsumasa; Shioyama, Yoshiyuki; Mizoguchi, Asumi; Hirose, Taka-Aki; Honda, Hiroshi; Umezu, Yoshiyuki; Nakamura, Yasuhiko; Hirata, Hideki
2015-03-01
A computerized framework for monitoring four-dimensional (4D) dose distributions during stereotactic body radiation therapy based on a portal dose image (PDI)-based 2D/3D registration approach has been proposed in this study. Using the PDI-based registration approach, simulated 4D "treatment" CT images were derived from the deformation of 3D planning CT images so that a 2D planning PDI could be similar to a 2D dynamic clinical PDI at a breathing phase. The planning PDI was calculated by applying a dose calculation algorithm (a pencil beam convolution algorithm) to the geometry of the planning CT image and a virtual water equivalent phantom. The dynamic clinical PDIs were estimated from electronic portal imaging device (EPID) dynamic images including breathing phase data obtained during a treatment. The parameters of the affine transformation matrix were optimized based on an objective function and a gamma pass rate using a Levenberg-Marquardt (LM) algorithm. The proposed framework was applied to the EPID dynamic images of ten lung cancer patients, which included 183 frames (mean: 18.3 per patient). The 4D dose distributions during the treatment time were successfully obtained by applying the dose calculation algorithm to the simulated 4D "treatment" CT images. The mean±standard deviation (SD) of the percentage errors between the prescribed dose and the estimated dose at an isocenter for all cases was 3.25±4.43%. The maximum error for the ten cases was 14.67% (prescribed dose: 1.50Gy, estimated dose: 1.72Gy), and the minimum error was 0.00%. The proposed framework could be feasible for monitoring the 4D dose distribution and dose errors within a patient's body during treatment. PMID:25592290
Chung, Johnathan C.; Wang, Dingxin; Lewandowski, Robert J.; Tang, Richard; Chrisman, Howard B.; Vogelzang, Robert L.; Woloschak, Gayle E.; Larson, Andrew C.; Omary, Reed A.; Ryu, Robert K.
2010-01-01
Purpose To test the hypothesis that four-dimensional (4D) transcatheter intra-arterial perfusion (TRIP) MR imaging can measure uterine fibroid perfusion changes immediately before and after uterine artery embolization (UAE) in the rabbit VX2 tumor model. Materials and Methods Eight VX2 uterine tumors were grown in 6 rabbits. After positioning a catheter within the uterine artery, we performed 4D TRIP-MRI measurements with 3 mL injections of 2.5% gadopentetate dimeglumine. We used a dynamic 3D spoiled-GRE sequence with in vivo B1-field correction for improved accuracy during perfusion quantification. We performed UAE using 1 mL of gelatin microspheres (2×106 particles; diameter 40-120 μm). Two regions-of-interest were drawn within each tumor upon perfusion maps. Functional embolic endpoints were reported as the mean percent reduction in fibroid tumor perfusion. Measurements before and after UAE were compared using paired t-tests (α = 0.05). Results VX2 uterine tumor perfusion decreased significantly from 27.1 at baseline to 7.09 after UAE (mL/min/100 mL tissue, p < 0.0001). Overall perfusion reduction was 76.3% (95% CI: 66.3%-86.3%). Conclusion 4D TRIP MRI can objectively quantify uterine fibroid perfusion reductions during UAE in VX2 rabbits. This technique could be used clinically to potentially determine an optimal embolic endpoint with the long-term goals of improving UAE success rates and minimizing procedure-related ischemic pain. PMID:20432349
Chao, M; Lo, Y; Yuan, Y; Sheu, R; Rosenzweig, K
2014-06-01
Purpose: To develop a tumor motion model from four-dimensional computed tomography (4DCT) of thoracic patients and demonstrate its impact on 4D radiation therapy simulation. Methods: A regional deformable image registration algorithm was introduced to extract tumor motion out of patient's breathing cycle. The gross target volume (GTV) was manually delineated on a selected phase of 4DCT and a subregion with 10mm margin supplemented to the GTV was created on the Eclipse treatment planning system (Varian Medical Systems, Palo Alto, CA). Together with 4DCT the structures were exported into an inhouse research platform. A free form B-Spline deformable registration was carried out to map the subregion to other respiratory phases. The displacement vector fields were employed to propagate GTV contours with which the center of mass (CoM) of the GTV was computed for each breathing phase of 4DCT. The resultant GTV motion and its volumetric shape are utilized to facilitate 4D treatment planning. Five lung cancer patients undergoing stereotactic body radiation therapy were enrolled and their 4DCT sets were included in the study. Results: Application of the algorithm to five thoracic patients indicates that clinically satisfactory outcomes were achievable with a spatial accuracy better than 2mm for GTV contour propagation between adjacent phases, and 3mm between opposite phases. The GTV CoM was found to be in the range of 2.0mm through 2.5cm, depending upon the tumor location. Compared to the traditional whole image based registration, the computation of the regional model was found to be an order of magnitude more efficient. Conclusion: A regional deformable registration model was implemented to extract tumor motion. It will have widespread application in 4D radiation treatment planning in the future to maximally utilize the available spatial-tempo information.
Mori, Shinichiro; Yanagi, Takeshi; Hara, Ryusuke; Sharp, Gregory C.; Asakura, Hiroshi; Kumagai, Motoki; Kishimoto, Riwa; Yamada, Shigeru; Kato, Hirotoshi; Kandatsu, Susumu; Kamada, Tadashi
2010-01-15
Purpose: We compared respiratory-gated and respiratory-ungated treatment strategies using four-dimensional (4D) scattered carbon ion beam distribution in pancreatic 4D computed tomography (CT) datasets. Methods and Materials: Seven inpatients with pancreatic tumors underwent 4DCT scanning under free-breathing conditions using a rapidly rotating cone-beam CT, which was integrated with a 256-slice detector, in cine mode. Two types of bolus for gated and ungated treatment were designed to cover the planning target volume (PTV) using 4DCT datasets in a 30% duty cycle around exhalation and a single respiratory cycle, respectively. Carbon ion beam distribution for each strategy was calculated as a function of respiratory phase by applying the compensating bolus to 4DCT at the respective phases. Smearing was not applied to the bolus, but consideration was given to drill diameter. The accumulated dose distributions were calculated by applying deformable registration and calculating the dose-volume histogram. Results: Doses to normal tissues in gated treatment were minimized mainly on the inferior aspect, which thereby minimized excessive doses to normal tissues. Over 95% of the dose, however, was delivered to the clinical target volume at all phases for both treatment strategies. Maximum doses to the duodenum and pancreas averaged across all patients were 43.1/43.1 GyE (ungated/gated) and 43.2/43.2 GyE (ungated/gated), respectively. Conclusions: Although gated treatment minimized excessive dosing to normal tissue, the difference between treatment strategies was small. Respiratory gating may not always be required in pancreatic treatment as long as dose distribution is assessed. Any application of our results to clinical use should be undertaken only after discussion with oncologists, particularly with regard to radiotherapy combined with chemotherapy.
Mori, Shinichiro; Kanematsu, Nobuyuki; Asakura, Hiroshi; Sharp, Gregory C.; Kumagai, Motoki; Dobashi, Suguru; Nakajima, Mio; Yamamoto, Naoyoshi; Kandatsu, Susumu; Baba, Masayuki
2011-06-01
Purpose: We compared four-dimensional (4D) layer-stacking and conventional carbon ion beam distribution in the treatment of lung cancer between ungated and gated respiratory strategies using 4DCT data sets. Methods and Materials: Twenty lung patients underwent 4DCT imaging under free-breathing conditions. Using planning target volumes (PTVs) at respective respiratory phases, two types of compensating bolus were designed, a full single respiratory cycle for the ungated strategy and an approximately 30% duty cycle for the exhalation-gated strategy. Beams were delivered to the PTVs for the ungated and gated strategies, PTV(ungated) and PTV(gated), respectively, which were calculated by combining the respective PTV(Tn)s by layer-stacking and conventional irradiation. Carbon ion beam dose distribution was calculated as a function of respiratory phase by applying a compensating bolus to 4DCT. Accumulated dose distributions were calculated by applying deformable registration. Results: With the ungated strategy, accumulated dose distributions were satisfactorily provided to the PTV, with D95 values for layer-stacking and conventional irradiation of 94.0% and 96.2%, respectively. V20 for the lung and Dmax for the spinal cord were lower with layer-stacking than with conventional irradiation, whereas Dmax for the skin (14.1 GyE) was significantly lower (21.9 GyE). In addition, dose conformation to the GTV/PTV with layer-stacking irradiation was better with the gated than with the ungated strategy. Conclusions: Gated layer-stacking irradiation allows the delivery of a carbon ion beam to a moving target without significant degradation of dose conformity or the development of hot spots.
Nishii, Tatsuya; Kono, Atsushi K; Tani, Wakiko; Suehiro, Erina; Negi, Noriyuki; Takahashi, Satoru; Sugimura, Kazuro
2016-01-01
Backgrounds. This study examines the hypothesis that four-dimensional noise reduction (4DNR) with short interval times reduces noise in cardiac computed tomography (CCT) using "padding" phases. Furthermore, the capability of reducing the reduction dose in CCT using this post-processing technique was assessed. Methods. Using base and quarter radiation doses for CCT (456 and 114 mAs/rot with 120 kVp), a static phantom was scanned ten times with retrospective electrocardiogram gating, and 4DNR with short interval times (50 ms) was performed using a post-processing technique. Differences in the computed tomography (CT) attenuation, contrast-to-noise ratio (CNR) and spatial resolution with modulation transfer function in each dose image obtained with and without 4DNR were assessed by conducting a Tukey-Kramer's test and non-inferiority test. Results. For the base dose, by using 4DNR, the CNR was improved from 1.18 ± 0.15 to 2.08 ± 0.20 (P = 0.001), while the CT attenuation and spatial resolution of the image of 4DNR did not were significantly inferior to those of reference image (P < 0.001). CNRs of the quarter-dose image in 4DNR also improved to 1.28 ± 0.11, and were not inferior to those of the non-4DNR images of the base dose (P < 0.001). Conclusions. 4DNR with short interval times significantly reduced noise. Furthermore, applying this method to CCT would have the potential of reducing the radiation dose by 75%, while maintaining a similar image noise level. PMID:26893966
Irvine, D M; Cole, A J; Hanna, G G; McGarry, C K
2015-01-01
Objective: The aim of this study was to identify sources of anatomical misrepresentation owing to the location of camera mounting, tumour motion velocity and image processing artefacts in order to optimize the four-dimensional CT (4DCT) scan protocol and improve geometrical–temporal accuracy. Methods: A phantom with an imaging insert was driven with a sinusoidal superior–inferior motion of varying amplitude and period for 4DCT scanning. The length of a high-density cube within the insert was measured using treatment planning software to determine the accuracy of its spatial representation. Scan parameters were varied, including the tube rotation period and the cine time between reconstructed images. A CT image quality phantom was used to measure various image quality signatures under the scan parameters tested. Results: No significant difference in spatial accuracy was found for 4DCT scans carried out using the wall- or couch-mounted camera for sinusoidal target motion. Greater spatial accuracy was found for 4DCT scans carried out using a tube rotation speed of 0.5 s rather than 1.0 s. The reduction in image quality when using a faster rotation speed was not enough to require an increase in patient dose. Conclusion: The 4DCT accuracy may be increased by optimizing scan parameters, including choosing faster tube rotation speeds. Peak misidentification in the recorded breathing trace may lead to spatial artefacts, and this risk can be reduced by using a couch-mounted infrared camera. Advances in knowledge: This study explicitly shows that 4DCT scan accuracy is improved by scanning with a faster CT tube rotation speed. PMID:25470359
Kono, Atsushi K.; Tani, Wakiko; Suehiro, Erina; Negi, Noriyuki; Takahashi, Satoru; Sugimura, Kazuro
2016-01-01
Backgrounds. This study examines the hypothesis that four-dimensional noise reduction (4DNR) with short interval times reduces noise in cardiac computed tomography (CCT) using “padding” phases. Furthermore, the capability of reducing the reduction dose in CCT using this post-processing technique was assessed. Methods. Using base and quarter radiation doses for CCT (456 and 114 mAs/rot with 120 kVp), a static phantom was scanned ten times with retrospective electrocardiogram gating, and 4DNR with short interval times (50 ms) was performed using a post-processing technique. Differences in the computed tomography (CT) attenuation, contrast-to-noise ratio (CNR) and spatial resolution with modulation transfer function in each dose image obtained with and without 4DNR were assessed by conducting a Tukey–Kramer’s test and non-inferiority test. Results. For the base dose, by using 4DNR, the CNR was improved from 1.18 ± 0.15 to 2.08 ± 0.20 (P = 0.001), while the CT attenuation and spatial resolution of the image of 4DNR did not were significantly inferior to those of reference image (P < 0.001). CNRs of the quarter-dose image in 4DNR also improved to 1.28 ± 0.11, and were not inferior to those of the non-4DNR images of the base dose (P < 0.001). Conclusions. 4DNR with short interval times significantly reduced noise. Furthermore, applying this method to CCT would have the potential of reducing the radiation dose by 75%, while maintaining a similar image noise level. PMID:26893966
2016-01-01
Purpose: The goal of this study was to evaluate normal hiatal dimensions in the third trimester in nulliparous Thai pregnant women and to establish which biometric factors were associated with various pregnancy outcomes. Methods: Fifty-seven consecutive nulliparous pregnant Thai women in their third trimester were recruited on a voluntary basis from April to October 2014. All subjects underwent four-dimensional (4D) translabial ultrasonography. Hiatal biometric parameters were measured at rest, while performing a Valsalva maneuver, and during contraction. Information about the patients’ eventual deliveries was obtained from their medical records. Results: The mean values of the patients’ age, body mass index, and gestational age at the time of examination were 27.4±5.47 years, 26.7±3.48 kg/m2, and 36.6±1.49 weeks, respectively. No subjects had vaginal lumps or experienced prolapse greater than stage 1 of the Pelvic Organ Prolapse Quantification system. Ultrasonography showed that the mean values of the hiatal area at rest, while performing a Valsalva maneuver, and during contraction were 13.10±2.92 cm2, 17.50±4.81 cm2, and 9.69±2.09 cm2, respectively. The hiatal area at rest, the axial measurement at rest, and the axial measurement while performing a Valsalva maneuver were significantly associated with the route of delivery (P=0.02, P=0.04, and P=0.03, respectively). Conclusion: The route of delivery was associated with hiatal biometric values measured using 4D translabial ultrasonography, based on the results of nulliparous Thai women in the third trimester. PMID:26403960
Shimohigashi, Yoshinobu; Araki, Fujio; Maruyama, Masato; Nakaguchi, Yuji; Nakato, Kengo; Nagasue, Nozomu; Kai, Yudai
2015-01-01
Our purpose in this study was to evaluate the performance of four-dimensional computed tomography (4D-CBCT) and to optimize the acquisition parameters. We evaluated the relationship between the acquisition parameters of 4D-CBCT and the accuracy of the target motion trajectory using a dynamic thorax phantom. The target motion was created three dimensionally using target sizes of 2 and 3 cm, respiratory cycles of 4 and 8 s, and amplitudes of 1 and 2 cm. The 4D-CBCT data were acquired under two detector configurations: "small mode" and "medium mode". The projection data acquired with scan times ranging from 1 to 4 min were sorted into 2, 5, 10, and 15 phase bins. The accuracy of the measured target motion trajectories was evaluated by means of the root mean square error (RMSE) from the setup values. For the respiratory cycle of 4 s, the measured trajectories were within 2 mm of the setup values for all acquisition times and target sizes. Similarly, the errors for the respiratory cycle of 8 s were <4 mm. When we used 10 or more phase bins, the measured trajectory errors were within 2 mm of the setup values. The trajectory errors for the two detector configurations showed similar trends. The acquisition times for achieving an RMSE of 1 mm for target sizes of 2 and 3 cm were 2 and 1 min, respectively, for respiratory cycles of 4 s. The results obtained in this study enable optimization of the acquisition parameters for target size, respiratory cycle, and desired measurement accuracy. PMID:25287015
Guckenberger, Matthias Wilbert, Juergen; Krieger, Thomas; Richter, Anne; Baier, Kurt; Flentje, Michael
2009-06-01
Purpose: To evaluate the accuracy of direct reconstruction of mid-ventilation and peak-phase four-dimensional (4D) computed tomography (CT) frames based on the external breathing signal. Methods and Materials: For 11 patients with 15 pulmonary targets, a respiration-correlated CT study (4D CT) was acquired for treatment planning. After retrospective time-based sorting of raw projection data and reconstruction of eight CT frames equally distributed over the breathing cycle, mean tumor position (P{sub mean}), mid-ventilation frame, and breathing motion were evaluated based on the internal tumor trajectory. Analysis of the external breathing signal (pressure sensor around abdomen) with amplitude-based sorting of projections was performed for direct reconstruction of the mid-ventilation frame and frames at peak phases of the breathing cycle. Results: On the basis of the eight 4D CT frames equally spaced in time, tumor motion was largest in the craniocaudal direction, with 12 {+-} 7 mm on average. Tumor motion between the two frames reconstructed at peak phases was not different in the craniocaudal and anterior-posterior directions but was systematically smaller in the left-right direction by 1 mm on average. The 3-dimensional distance between P{sub mean} and the tumor position in the mid-ventilation frame based on the internal tumor trajectory was 1.2 {+-} 1 mm. Reconstruction of the mid-ventilation frame at the mean amplitude position of the external breathing signal resulted in tumor positions 2.0 {+-} 1.1 mm distant from P{sub mean}. Breathing-induced motion artifacts in mid-ventilation frames caused negligible changes in tumor volume and shape. Conclusions: Direct reconstruction of the mid-ventilation frame and frames at peak phases based on the external breathing signal was reliable. This makes the reconstruction of only three 4D CT frames sufficient for application of the mid-ventilation technique in clinical practice.
Guo, Bing; Li, Jian-Bin; Wang, Wei; Xu, Min; Li, Yan-Kang; Liu, Tong-Hai
2016-01-01
Purpose To investigate the potential dosimetric benefits from four-dimensional computed tomography (4DCT) compared with three-dimensional computed tomography (3DCT) in radiotherapy treatment planning for external-beam partial breast irradiation (EB-PBI). Patients and methods 3DCT and 4DCT scan sets were acquired for 20 patients who underwent EB-PBI. The volume of the tumor bed (TB) was determined based on seroma or surgical clips on 3DCT images (defined as TB3D) and the end inhalation (EI) and end exhalation (EE) phases of 4DCT images (defined as TBEI and TBEE, respectively). The clinical target volume (CTV) consisted of the TB plus a 1.0 cm margin. The planning target volume (PTV) was the CTV plus 0.5 cm (defined as PTV3D, PTVEI, and PTVEE). For each patient, a conventional 3D conformal plan (3D-CRT) was generated (defined as EB-PBI3D, EB-PBIEI, and EB-PBIEE). Results The PTV3D, PTVEI, and PTVEE were similar (P=0.549), but the PTV coverage of EB-PBI3D was significantly less than that of EB-PBIEI or EB-PBIEE (P=0.001 and P=0.025, respectively). There were no significant differences in the homogeneity or conformity indexes between the three treatment plans (P=0.125 and P=0.536, respectively). The EB-PBI3D plan resulted in the largest organs at risk dose. Conclusion There was a significant benefit for patients when using 3D-CRT based on 4DCT for EB-PBI with regard to reducing nontarget organ exposure. Respiratory motion did not affect the dosimetric distribution during free breathing, but might result in poor dose coverage when the PTV is determined using 3DCT. PMID:27099517
Mohammed, Nasiruddin; Kestin, Larry; Grills, Inga; Shah, Chirag; Glide-Hurst, Carri; Yan, Di; Ionascu, Dan
2012-03-15
Purpose: To investigate the impact of primary tumor and involved lymph node (LN) geometry (centroid, shape, volume) on internal target volume (ITV) throughout treatment for locally advanced non-small cell lung cancer using weekly four-dimensional computed tomography (4DCT). Methods and Materials: Eleven patients with advanced non-small cell lung cancer were treated using image-guided radiotherapy with acquisition of weekly 10-Phase 4DCTs (n = 51). Initial ITV was based on planning 4DCT. Master-ITV incorporated target geometry across the entire treatment (all 4DCTs). Geographic miss was defined as the % Master-ITV positioned outside of the initial planning ITV after registration is complete. Registration strategies considered were bony (B), primary tumor soft tissue alone (T), and registration based on primary tumor and involved LNs (T{sub L}N). Results: The % geographic miss for the primary tumor, mediastinal, and hilar lymph nodes based on each registration strategy were (1) B: 30%, 30%, 30%; (2) T: 21%, 40%, 36%; and (3) T{sub L}N: 26%, 26%, 27%. Mean geographic expansions to encompass 100% of the primary tumor and involved LNs were 1.2 {+-} 0.7 cm and 0.8 {+-} 0.3 cm, respectively, for B and T{sub L}N. Primary and involved LN expansions were 0.7 {+-} 0.5 cm and 1.1 {+-} 0.5 cm for T. Conclusion: T is best for solitary targets. When treatments include primary tumor and LNs, B and T{sub L}N provide more comprehensive geographic coverage. We have identified high % geographic miss when considering multiple registration strategies. The dosimetric implications are the subject of future study.
Zhang, Sheng; Chen, Weili; Tang, Huan; Han, Quan; Yan, Shenqiang; Zhang, Xiaocheng; Chen, Qingmeng; Parsons, Mark; Wang, Shaoshi; Lou, Min
2016-01-01
Objective Leptomeningeal collaterals, which affects tissue fate, are still challenging to assess. Four-dimensional CT angiography (4D CTA) originated from CT perfusion (CTP) provides the possibility of non-invasive and time-resolved assessment of leptomeningeal collateral flow. We sought to develop a comprehensive rating system to integrate the speed and extent of collateral flow on 4D CTA, and investigate its prognostic value for reperfusion therapy in acute ischemic stroke (AIS) patients. Methods We retrospectively studied 80 patients with M1 ± internal carotid artery (ICA) occlusion who had baseline CTP before intravenous thrombolysis. The velocity and extent of collaterals were evaluated by regional leptomeningeal collateral score on peak phase (rLMC-P) and temporally fused intensity projections (tMIP) (rLMC-M) on 4D CTA, respectively. The cutoffs of rLMC-P and rLMC-M score for predicting good outcome (mRS score ≤ 2) were integrated to develop the collateral grading scale (CGS) (rating from 0–2). Results The CGS score was correlated with 3-months mRS score (non-recanalizers: ρ = -0.495, p = 0.01; recanalizers: ρ = -0.671, p < 0.001). Patients with intermediate or good collaterals (CGS score of 1 and 2) who recanalized were more likely to have good outcome than those without recanalization (p = 0.038, p = 0.018), while there was no significant difference in outcome in patients with poor collaterals (CGS score of 0) stratified by recanalization (p = 0.227). Conclusions Identification of collaterals based on CGS may help to select good responders to reperfusion therapy in patients with large artery occlusion. PMID:27505435
Nakamura, Mitsuhiro; Sawada, Akira; Ishihara, Yoshitomo; Takayama, Kenji; Mizowaki, Takashi; Kaneko, Shuji; Yamashita, Mikiko; Tanabe, Hiroaki; Kokubo, Masaki; Hiraoka, Masahiro
2010-09-15
Purpose: To present the dosimetric characterization of a multileaf collimator (MLC) for a new four-dimensional image-guided radiotherapy system with a gimbaled x-ray head, MHI-TM2000. Methods: MHI-TM2000 has an x-ray head composed of an ultrasmall linear accelerator guide and a system-specific MLC. The x-ray head can rotate along the two orthogonal gimbals (pan and tilt rotations) up to {+-}2.5 deg., which swings the beam up to {+-}41.9 mm in each direction from the isocenter on the isocenter plane perpendicular to the beam. The MLC design is a single-focus type, has 30 pairs of 5 mm thick leaves at the isocenter, and produces a maximum field size of 150x150 mm{sup 2}. Leaf height and length are 110 and 260 mm, respectively. Each leaf end is circular, with a radius of curvature of 370 mm. The distance that each leaf passes over the isocenter is 77.5 mm. Radiation leakage between adjacent leaves is minimized by an interlocking tongue-and-groove (T and G) arrangement with the height of the groove part 55 mm. The dosimetric characterizations including field characteristics, leaf position accuracy, leakage, and T and G effect were evaluated using a well-commissioned 6 MV photon beam, EDR2 films (Kodak, Rochester, NY), and water-equivalent phantoms. Furthermore, the field characteristics and leaf position accuracy were evaluated under conditions of pan or tilt rotation. Results: The differences between nominal and measured field sizes were within {+-}0.5 mm. Although the penumbra widths were greater with wider field size, the maximum width was <5.5 mm even for the fully opened field. Compared to the results of field characteristics without pan or tilt rotation, the variation in field size, penumbra width, flatness, and symmetry was within {+-}1 mm/1% at the maximum pan or tilt rotational angle. The leaf position accuracy was 0.0{+-}0.1 mm, ranging from -0.3 to 0.2 mm at four gantry angles of 0 deg., 90 deg., 180 deg., and 270 deg. with and without pan or tilt rotation
Kamino, Yuichiro; Miura, Sadao; Kokubo, Masaki; Yamashita, Ichiro; Hirai, Etsuro; Hiraoka, Masahiro; Ishikawa, Junzo
2007-05-15
We are developing a four-dimensional image-guided radiotherapy system with a gimbaled x-ray head. It is capable of pursuing irradiation and delivering irradiation precisely with the help of an agile moving x-ray head on the gimbals. Requirements for the accelerator guide were established, system design was developed, and detailed design was conducted. An accelerator guide was manufactured and basic beam performance and leakage radiation from the accelerator guide were evaluated at a low pulse repetition rate. The accelerator guide including the electron gun is 38 cm long and weighs about 10 kg. The length of the accelerating structure is 24.4 cm. The accelerating structure is a standing wave type and is composed of the axial-coupled injector section and the side-coupled acceleration cavity section. The injector section is composed of one prebuncher cavity, one buncher cavity, one side-coupled half cavity, and two axial coupling cavities. The acceleration cavity section is composed of eight side-coupled nose reentrant cavities and eight coupling cavities. The electron gun is a diode-type gun with a cerium hexaboride (CeB{sub 6}) direct heating cathode. The accelerator guide can be operated without any magnetic focusing device. Output beam current was 75 mA with a transmission efficiency of 58%, and the average energy was 5.24 MeV. Beam energy was distributed from 4.95 to 5.6 MeV. The beam profile, measured 88 mm from the beam output hole on the axis of the accelerator guide, was 0.7 mmx0.9 mm full width at half maximum (FWHM) width. The beam loading line was 5.925 (MeV)-I{sub b} (mA)x0.00808 (MeV/mA), where I{sub b} is output beam current. The maximum radiation leakage of the accelerator guide at 100 cm from the axis of the accelerator guide was calculated as 0.33 cGy/min at the rated x-ray output of 500 cGy/min from the measured value. This leakage requires no radiation shielding for the accelerator guide itself per IEC 60601-2-1.
NASA Astrophysics Data System (ADS)
Kreylos, O.; Bawden, G. W.; Kellogg, L. H.
2007-12-01
In the context of the UC~Davis W. M. Keck Center for Active Visualization in the Earth Sciences (KeckCAVES, http://www.keckcaves.org), we are developing an immersive visualization application to display and interact with very large (billions of points) three- and four-dimensional point-position datasets, such that point groups from repeated airborne and ground based Light Detection And Ranging (LiDAR) surveys can be selected, measured, and analyzed for quality control and land surface change detection. One of the difficulties of analyzing dense 3D and 4D point-cloud data is that there are few software packages that can display and analyze the data at full resolution and in the natural 3D perspective in which it was collected. We developed an octree-based, multiresolution, point-set data representation that allows very large point cloud datasets to be displayed at the frame rates required to create immersion (between 60 Hz and 120 Hz). Data inside an observer's region of interest is shown in full detail, whereas data outside the field of view or far away from the observer is shown at reduced resolution to provide context. Users can navigate LiDAR data sets and accurately select related point groups in two or more point sets by sweeping space using 3D input devices provided by immersive display environments such as CAVEs. Users can then guide the software in deriving positional information from point groups to compute displacements between surveys, or to extract survey measurements. This software runs on UNIX-like operating systems and can be used on laptop or desktop computers, 3D display systems such as Geowalls, and in fully immersive environments such as CAVEs. It is available for download from http://www.keckcaves.org. Examples of the wide range of applications of the software for airborne and Tripod LiDAR (T-LiDAR) include: 1)~visualization of airborne LiDAR data from the southern San Andreas Fault; 2)~quality control assessment of ground based T-LiDAR from the
Kipritidis, J; Keall, P; Hugo, G; Weiss, E; Williamson, J
2014-06-15
Purpose: Four-dimensional cone beam CT ventilation imaging (4D-CBCT VI) is a novel functional lung imaging modality requiring validation. We hypothesize that 4D-CBCT VI satisfies a necessary condition for validity: that intrafraction variations (e.g. due to poor 4D-CBCT image quality) are substantially different to interfraction variations (e.g. due to changes in underlying function). We perform the first comparison of intrafraction (pre/post fraction) and interfraction (week-to-week) 4D-CBCT VIs for locally advanced non small cell lung cancer (LA NSCLC) patients undergoing radiation therapy. Methods: A total of 215 4D-CBCT scans were acquired for 19 LA NSCLC patients over 4-6 weeks of radiation therapy, including 75 pairs of pre-/post-fraction scans on the same day. 4D-CBCT VIs were obtained by applying state-of-the-art, B-spline deformable image registration to obtain the Jacobian determinant of deformation between the end-exhale and end-inhale phases. All VIs were deformably registered to the corresponding first day scan, normalized between the 10th and 90th percentile values and cropped to the ipsilateral lung only. Intrafraction variations were assessed by computing the mean and standard deviation of voxel-wise differences between all same-day pairs of pre-/post-fraction VIs. Interfraction differences were computed between first-day VIs and treatment weeks 2, 4 and 6 for all 19 patients. We tested the hypothesis by comparing cumulative distribution functions (CDFs) of intrafraction and interfraction ventilation differences using two-sided Kolmogorov-Smirnov goodness-of-fit tests. Results: The (mean ± std. dev.) of intrafraction differences was (−0.007 ± 0.079). Interfraction differences for weeks 2, 4 and 6 were (−0.035 ± 0.103), (−0.006 ± 0.094) and (−0.019 ± 0.127) respectively. For week 2, the changes in CDFs for intrafraction and interfraction differences approached statistical significance (p=0.099). Conclusion: We have shown that 4D-CBCT VI
Terluin, Berend; van Marwijk, Harm WJ; Adèr, Herman J; de Vet, Henrica CW; Penninx, Brenda WJH; Hermens, Marleen LM; van Boeijen, Christine A; van Balkom, Anton JLM; van der Klink, Jac JL; Stalman, Wim AB
2006-01-01
Background The Four-Dimensional Symptom Questionnaire (4DSQ) is a self-report questionnaire that has been developed in primary care to distinguish non-specific general distress from depression, anxiety and somatization. The purpose of this paper is to evaluate its criterion and construct validity. Methods Data from 10 different primary care studies have been used. Criterion validity was assessed by comparing the 4DSQ scores with clinical diagnoses, the GPs' diagnosis of any psychosocial problem for Distress, standardised psychiatric diagnoses for Depression and Anxiety, and GPs' suspicion of somatization for Somatization. ROC analyses and logistic regression analyses were used to examine the associations. Construct validity was evaluated by investigating the inter-correlations between the scales, the factorial structure, the associations with other symptom questionnaires, and the associations with stress, personality and social functioning. The factorial structure of the 4DSQ was assessed through confirmatory factor analysis (CFA). The associations with other questionnaires were assessed with Pearson correlations and regression analyses. Results Regarding criterion validity, the Distress scale was associated with any psychosocial diagnosis (area under the ROC curve [AUC] 0.79), the Depression scale was associated with major depression (AUC = 0.83), the Anxiety scale was associated with anxiety disorder (AUC = 0.66), and the Somatization scale was associated with the GPs' suspicion of somatization (AUC = 0.65). Regarding the construct validity, the 4DSQ scales appeared to have considerable inter-correlations (r = 0.35-0.71). However, 30–40% of the variance of each scale was unique for that scale. CFA confirmed the 4-factor structure with a comparative fit index (CFI) of 0.92. The 4DSQ scales correlated with most other questionnaires measuring corresponding constructs. However, the 4DSQ Distress scale appeared to correlate with some other depression scales more
Hsiao, Albert; Yousaf, Ufra; Alley, Marcus T.; Lustig, Michael; Chan, Frandics Pak; Newman, Beverley; Vasanawala, Shreyas S.
2016-01-01
Background Cardiac MRI is routinely performed for quantification of shunt flow in patients with anomalous pulmonary veins, but can be technically-challenging to perform. Four-dimensional phase-contrast (4D-PC) MRI has potential to simplify this exam. We sought to determine whether 4D-PC may be a viable clinical alternative to conventional 2D phase-contrast MR imaging. Methods With institutional review board approval and HIPAA-compliance, we retrospectively identified all patients with anomalous pulmonary veins who underwent cardiac MRI at either 1.5 Tesla (T) or 3T with parallel-imaging compressed-sensing (PI-CS) 4D-PC between April, 2011 and October, 2013. A total of 15 exams were included (10 male, 5 female). Algorithms for interactive streamline visualization were developed and integrated into in-house software. Blood flow was measured at the valves, pulmonary arteries and veins, cavae, and any associated shunts. Pulmonary veins were mapped to their receiving atrial chamber with streamlines. The intraobserver, interobserver, internal consistency of flow measurements, and consistency with conventional MRI were then evaluated with Pearson correlation and Bland-Altman analysis. Results Triplicate measurements of blood flow from 4D-PC were highly consistent, particularly at the aortic and pulmonary valves (cv 2–3%). Flow measurements were reproducible by a second observer (ρ = 0.986–0.999). Direct measurements of shunt volume from anomalous veins and intracardiac shunts matched indirect estimates from the outflow valves (ρ = 0.966). Measurements of shunt fraction using 4D-PC using any approach were more consistent with ventricular volumetric displacements than conventional 2D-PC (ρ = 0.972–0.991 versus 0.929). Conclusion Shunt flow may be reliably quantified with 4D-PC MRI, either indirectly or with detailed delineation of flow from multiple shunts. The 4D-PC may be a more accurate alternative to conventional MRI. PMID:25914149
Kamino, Yuichiro; Miura, Sadao; Kokubo, Masaki; Yamashita, Ichiro; Hirai, Etsuro; Hiraoka, Masahiro; Ishikawa, Junzo
2007-05-01
We are developing a four-dimensional image-guided radiotherapy system with a gimbaled x-ray head. It is capable of pursuing irradiation and delivering irradiation precisely with the help of an agile moving x-ray head on the gimbals. Requirements for the accelerator guide were established, system design was developed, and detailed design was conducted. An accelerator guide was manufactured and basic beam performance and leakage radiation from the accelerator guide were evaluated at a low pulse repetition rate. The accelerator guide including the electron gun is 38 cm long and weighs about 10 kg. The length of the accelerating structure is 24.4 cm. The accelerating structure is a standing wave type and is composed of the axial-coupled injector section and the side-coupled acceleration cavity section. The injector section is composed of one prebuncher cavity, one buncher cavity, one side-coupled half cavity, and two axial coupling cavities. The acceleration cavity section is composed of eight side-coupled nose reentrant cavities and eight coupling cavities. The electron gun is a diode-type gun with a cerium hexaboride (CeB6) direct heating cathode. The accelerator guide can be operated without any magnetic focusing device. Output beam current was 75 mA with a transmission efficiency of 58%, and the average energy was 5.24 MeV. Beam energy was distributed from 4.95 to 5.6 MeV. The beam profile, measured 88 mm from the beam output hole on the axis of the accelerator guide, was 0.7 mm X 0.9 mm full width at half maximum (FWHM) width. The beam loading line was 5.925 (MeV)-Ib (mA) X 0.00808 (MeV/mA), where Ib is output beam current. The maximum radiation leakage of the accelerator guide at 100 cm from the axis of the accelerator guide was calculated as 0.33 cGy/min at the rated x-ray output of 500 cGy/min from the measured value. This leakage requires no radiation shielding for the accelerator guide itself per IEC 60601-2-1. PMID:17555261
Taguenang, J; Algan, O; Ahmad, S; Ali, I
2014-06-01
Purpose: To investigate quantitatively the variations in dose-distributions induced by motion by measurements and modeling. A four-dimensional (4D) motion model of dose distributions that accounts for different motion parameters was developed. Methods: Variations in dose distributions induced by sinusoidal phantom motion were measured using a multiple-diode-array-detector (MapCheck2). MapCheck2 was mounted on a mobile platform that moves with adjustable calibrated motion patterns in the superior-inferior direction. Various plans including open and intensity-modulated fields were used to irradiate MapCheck2. A motion model was developed to predict spatial and temporal variations in the dose-distributions and dependence on the motion parameters using pencil-beam spread-out superposition function. This model used the superposition of pencil-beams weighted with a probability function extracted from the motion trajectory. The model was verified with measured dose-distributions obtained from MapCheck2. Results: Dose-distribution varied considerably with motion where in the regions between isocenter and 50% isodose-line, dose decreased with increase of the motion amplitude. Dose levels increased with increase in the motion amplitude in the region beyond 50% isodose-line. When the range of motion (ROM=twice amplitude) was smaller than the field length both central axis dose and the 50% isodose-line did not change with variation of motion amplitude and remained equal to the dose of stationary phantom. As ROM became larger than the field length, the dose level decreased at central axis dose and 50% isodose-line. Motion frequency and phase did not affect the dose distributions which were delivered over an extended time longer than few motion cycles, however, they played an important role for doses delivered with high-dose-rates within one motion cycle . Conclusion: A 4D-dose motion model was developed to predict and correct variations in dose distributions induced by one
Kang, S; Kim, D; Kim, T; Kim, K; Cho, M; Shin, D; Suh, T; Kim, S; Park, S
2015-06-15
Purpose: Respiratory motion in thoracic and abdominal region could lead to significant underdosing of target and increased dose to healthy tissues. The aim of this study is to evaluate the dosimetric effect of respiratory motion in conventional 3D dose by comparing 4D deformable dose in liver stereotactic body radiotherapy (SBRT). Methods: Five patients who had previously treated liver SBRT were included in this study. Four-dimensional computed tomography (4DCT) images with 10 phases for all patients were acquired on multi-slice CT scanner (Siemens, Somatom definition). Conventional 3D planning was performed using the average intensity projection (AIP) images. 4D dose accumulation was calculated by summation of dose distribution for all phase images of 4DCT using deformable image registration (DIR) . The target volume and normal organs dose were evaluated with the 4D dose and compared with those from 3D dose. And also, Index of achievement (IOA) which assesses the consistency between planned dose and prescription dose was used to compare target dose distribution between 3D and 4D dose. Results: Although the 3D dose calculation considered the moving target coverage, significant differences of various dosimetric parameters between 4D and 3D dose were observed in normal organs and PTV. The conventional 3D dose overestimated dose to PTV, however, there was no significant difference for GTV. The average difference of IOA which become ‘1’ in an ideal case was 3.2% in PTV. The average difference of liver and duodenum was 5% and 16% respectively. Conclusion: 4D dose accumulation which can provide dosimetric effect of respiratory motion has a possibility to predict the more accurate delivered dose to target and normal organs and improve treatment accuracy. This work was supported by the Radiation Technology R&D program (No. 2013M2A2A7043498) and the Mid-career Researcher Program (2014R1A2A1A10050270) through the National Research Foundation of Korea funded by the
Vedam, S.; Docef, A.; Fix, M.; Murphy, M.; Keall, P.
2005-06-15
The synchronization of dynamic multileaf collimator (DMLC) response with respiratory motion is critical to ensure the accuracy of DMLC-based four dimensional (4D) radiation delivery. In practice, however, a finite time delay (response time) between the acquisition of tumor position and multileaf collimator response necessitates predictive models of respiratory tumor motion to synchronize radiation delivery. Predicting a complex process such as respiratory motion introduces geometric errors, which have been reported in several publications. However, the dosimetric effect of such errors on 4D radiation delivery has not yet been investigated. Thus, our aim in this work was to quantify the dosimetric effects of geometric error due to prediction under several different conditions. Conformal and intensity modulated radiation therapy (IMRT) plans for a lung patient were generated for anterior-posterior/posterior-anterior (AP/PA) beam arrangements at 6 and 18 MV energies to provide planned dose distributions. Respiratory motion data was obtained from 60 diaphragm-motion fluoroscopy recordings from five patients. A linear adaptive filter was employed to predict the tumor position. The geometric error of prediction was defined as the absolute difference between predicted and actual positions at each diaphragm position. Distributions of geometric error of prediction were obtained for all of the respiratory motion data. Planned dose distributions were then convolved with distributions for the geometric error of prediction to obtain convolved dose distributions. The dosimetric effect of such geometric errors was determined as a function of several variables: response time (0-0.6 s), beam energy (6/18 MV), treatment delivery (3D/4D), treatment type (conformal/IMRT), beam direction (AP/PA), and breathing training type (free breathing/audio instruction/visual feedback). Dose difference and distance-to-agreement analysis was employed to quantify results. Based on our data, the
Xun, D.M.; Liu, Q.H.; Zhu, X.M.
2013-11-15
A generalization of Dirac’s canonical quantization scheme for a system with second-class constraints is proposed, in which the fundamental commutation relations are constituted by all commutators between positions, momenta and Hamiltonian, so they are simultaneously quantized in a self-consistent manner, rather than by those between merely positions and momenta which leads to ambiguous forms of the Hamiltonian and the momenta. The application of the generalized scheme to the quantum motion on a torus leads to a remarkable result: the quantum theory is inconsistent if built up in an intrinsic geometric manner, whereas it becomes consistent within an extrinsic examination of the torus as a submanifold in three dimensional flat space with the use of the Cartesian coordinate system. The geometric momentum and potential are then reasonably reproduced. -- Highlights: •A generalization of Dirac’s canonical quantization is proposed for a system with second-class constraints. •Quantum motion on torus surface is explicitly treated to show how Schrödinger formalism is complementary to the Dirac one. •The embedding effect in quantum mechanics is originated from the quantization.
Four-Dimensional Spatial Reasoning in Humans
ERIC Educational Resources Information Center
Aflalo, T. N.; Graziano, M. S. A.
2008-01-01
Human subjects practiced navigation in a virtual, computer-generated maze that contained 4 spatial dimensions rather than the usual 3. The subjects were able to learn the spatial geometry of the 4-dimensional maze as measured by their ability to perform path integration, a standard test of spatial ability. They were able to travel down a winding…
Four-dimensional ultrafast electron microscopy
Lobastov, Vladimir A.; Srinivasan, Ramesh; Zewail, Ahmed H.
2005-01-01
Electron microscopy is arguably the most powerful tool for spatial imaging of structures. As such, 2D and 3D microscopies provide static structures with subnanometer and increasingly with ångstrom-scale spatial resolution. Here we report the development of 4D ultrafast electron microscopy, whose capability imparts another dimension to imaging in general and to dynamics in particular. We demonstrate its versatility by recording images and diffraction patterns of crystalline and amorphous materials and images of biological cells. The electron packets, which were generated with femtosecond laser pulses, have a de Broglie wavelength of 0.0335 Å at 120 keV and have as low as one electron per pulse. With such few particles, doses of few electrons per square ångstrom, and ultrafast temporal duration, the long sought after but hitherto unrealized quest for ultrafast electron microscopy has been realized. Ultrafast electron microscopy should have an impact on all areas of microscopy, including biological imaging. PMID:15883380
Recent developments in four-dimensional supergravity
NASA Astrophysics Data System (ADS)
Sharpe, Eric
2011-10-01
I will summarize recent work on gauge theories in supergravity, specifically concerning the `Fayet-Iliopoulos' parameter. In rigidly supersymmetric gauge theories, this parameter also appears and can vary continuously. In supergravity old lore held that it should always vanish. I will discuss recent developments showing that in fact it can be nonzero, but is quantized, and will explore various ramifications of that result.
Respiratory gating and four-dimensional tomotherapy
NASA Astrophysics Data System (ADS)
Zhang, Tiezhi
Helical tomotherapy is a new IMRT delivery process developed at the University of Wisconsin and TomoTherapy Inc. Tomotherapy may be of advantage in lung cancer treatment due to its rational delivery mode. As with conventional IMRT delivery, however, intrafraction respiratory motion during a tomotherapy treatment causes unnecessary radiation to the healthy tissue. Possible solutions to these problems associated with intrafraction motion have been studied in this thesis. A spirometer is useful for monitoring breathing because of its direct correlation with lung volume changes. However, its inherent drift prevents its application in long term breathing monitoring. With a calibration and stabilization algorithm, a spirometer is able to provide accurate, long term lung volume change measurements. Such a spirometer system is most suited for Deep Inspiration Breath-Hold (DIBH) treatments. An improved laser-spirometer combined system has also been developed for target tracking in 4-D treatment. Spirometer signals are used to calibrate the displacement measurements into lung volume changes, thereby eliminating scaling errors from daily setup variations. The laser displacement signals may also be used to correct spirometer drifts during operation. A new 4-D treatment technique has been developed to account for intrafraction motion in treatment planning. The patient's breathing and beam delivery are synchronized, and the target motion/deformation is incorporated into treatment plan optimization. Results show that this new 4-D treatment technique significantly reduces motion effects and provides improved patient tolerance.
Sciarrone, Danilo; Pantò, Sebastiano; Tranchida, Peter Quinto; Dugo, Paola; Mondello, Luigi
2014-05-01
This study reports the recent evolution of a multidimensional GC-GC-GC preparative system, now combined with an online LC preseparation step, operated under normal phase conditions. It is herein shown that the four-dimensional instrument can collect sample components with a concentration lower than 10%, in a short time period, while maintaining a high level of analyte purity. The LC dimension allows (I) the injection of higher sample amounts, compared to "direct" GC injection; (II) a polarity-based preseparation, leading to the GC injection of simplified subsamples, and thus reducing the possibility of coelutions; (III) to eliminate the essential-oil "matrix", replacing it with the LC mobile phase (the GC system is more protected from potential contamination); (IV) the LC mobile phase is of much lower viscosity with respect to a pure, or highly concentrated essential oil, avoiding difficulties in the syringe sample withdrawal process, prior to GC injection. System optimization was performed by using standard solutions; in addition, a very complex sample, namely, vetiver essential oil, was subjected to the preparative process, with the scope of isolating two low-amount constituents (namely, α-amorphene and β-vetivone). The latter two sesquiterpenoids, which accounted for 1.7 and 4.0% of the sample (considering the volatiles), respectively, were successfully collected at the milligram level, in a one-day work period, with a purity degree in excess of 90%. PMID:24725161
NASA Astrophysics Data System (ADS)
Helmus, Jonathan J.; Nadaud, Philippe S.; Höfer, Nicole; Jaroniec, Christopher P.
2008-02-01
We describe three- and four-dimensional semiconstant-time transferred echo double resonance (SCT-TEDOR) magic-angle spinning solid-state nuclear magnetic resonance (NMR) experiments for the simultaneous measurement of multiple long-range N15-Cmethyl13 dipolar couplings in uniformly C13, N15-enriched peptides and proteins with high resolution and sensitivity. The methods take advantage of C13 spin topologies characteristic of the side-chain methyl groups in amino acids alanine, isoleucine, leucine, methionine, threonine, and valine to encode up to three distinct frequencies (N15-Cmethyl13 dipolar coupling, N15 chemical shift, and Cmethyl13 chemical shift) within a single SCT evolution period of initial duration ˜1/JCC1 (where JCC1≈35Hz, is the one-bond Cmethyl13-C13 J-coupling) while concurrently suppressing the modulation of NMR coherences due to C13-C13 and N15-C13 J-couplings and transverse relaxation. The SCT-TEDOR schemes offer several important advantages over previous methods of this type. First, significant (approximately twofold to threefold) gains in experimental sensitivity can be realized for weak N15-Cmethyl13 dipolar couplings (corresponding to structurally interesting, ˜3.5Å or longer, distances) and typical Cmethyl13 transverse relaxation rates. Second, the entire SCT evolution period can be used for Cmethyl13 and/or N15 frequency encoding, leading to increased spectral resolution with minimal additional coherence decay. Third, the experiments are inherently "methyl selective," which results in simplified NMR spectra and obviates the use of frequency-selective pulses or other spectral filtering techniques. Finally, the N15-C13 cross-peak buildup trajectories are purely dipolar in nature (i.e., not influenced by J-couplings or relaxation), which enables the straightforward extraction of N15-Cmethyl13 distances using an analytical model. The SCT-TEDOR experiments are demonstrated on a uniformly C13, N15-labeled peptide, N-acetyl-valine, and a 56
Peters, Kenneth E.; Magoon, Leslie B.; Lampe, Carolyn; Scheirer, Allegra Hosford; Lillis, Paul G.; Gautier, Donald L.
2008-01-01
A calibrated numerical model depicts the geometry and three-dimensional (3-D) evolution of petroleum systems through time (4-D) in a 249 x 309 km (155 x 192 mi) area covering all of the San Joaquin Basin Province of California. Model input includes 3-D structural and stratigraphic data for key horizons and maps of unit thickness, lithology, paleobathymetry, heat flow, original total organic carbon, and original Rock-Eval pyrolysis hydrogen index for each source rock. The four principal petroleum source rocks in the basin are the Miocene Antelope shale of Graham and Williams (1985; hereafter referred to as Antelope shale), the Eocene Kreyenhagen Formation, the Eocene Tumey formation of Atwill (1935; hereafter referred to as Tumey formation), and the Cretaceous to Paleocene Moreno Formation. Due to limited Rock-Eval/total organic carbon data, the Tumey formation was modeled using constant values of original total organic carbon and original hydrogen index. Maps of original total organic carbon and original hydrogen index were created for the other three source rocks. The Antelope shale was modeled using Type IIS kerogen kinetics, whereas Type II kinetics were used for the other source rocks. Four-dimensional modeling and geologic field evidence indicate that maximum burial of the three principal Cenozoic source rocks occurred in latest Pliocene to Holocene time. For example, a 1-D extraction of burial history from the 4-D model in the Tejon depocenter shows that the bottom of the Antelope shale source rock began expulsion (10 percent transformation ratio) about 4.6 Ma and reached peak expulsion (50 percent transformation ratio) about 3.6 Ma. Except on the west flank of the basin, where steep dips in outcrop and seismic data indicate substantial uplift, little or no section has been eroded. Most petroleum migration occurred during late Cenozoic time in distinct stratigraphic intervals along east-west pathways from pods of active petroleum source rock in the Tejon and
Four-dimensional computed tomography: image formation and clinical protocol.
Rietzel, Eike; Pan, Tinsu; Chen, George T Y
2005-04-01
Respiratory motion can introduce significant errors in radiotherapy. Conventional CT scans as commonly used for treatment planning can include severe motion artifacts that result from interplay effects between the advancing scan plane and object motion. To explicitly include organ/target motion in treatment planning and delivery, time-resolved CT data acquisition (4D Computed Tomography) is needed. 4DCT can be accomplished by oversampled CT data acquisition at each slice. During several CT tube rotations projection data are collected in axial cine mode for the duration of the patient's respiratory cycle (plus the time needed for a full CT gantry rotation). Multiple images are then reconstructed per slice that are evenly distributed over the acquisition time. Each of these images represents a different anatomical state during a respiratory cycle. After data acquisition at one couch position is completed, x rays are turned off and the couch advances to begin data acquisition again until full coverage of the scan length has been obtained. Concurrent to CT data acquisition the patient's abdominal surface motion is recorded in precise temporal correlation. To obtain CT volumes at different respiratory states, reconstructed images are sorted into different spatio-temporally coherent volumes based on respiratory phase as obtained from the patient's surface motion. During binning, phase tolerances are chosen to obtain complete volumetric information since images at different couch positions are reconstructed at different respiratory phases. We describe 4DCT image formation and associated experiments that characterize the properties of 4DCT. Residual motion artifacts remain due to partial projection effects. Temporal coherence within resorted 4DCT volumes is dominated by the number of reconstructed images per slice. The more images are reconstructed, the smaller phase tolerances can be for retrospective sorting. From phantom studies a precision of about 2.5 mm for quasiregular motion and typical respiratory periods could be concluded. A protocol for 4DCT scanning was evaluated and clinically implemented at the MGH. Patient data are presented to elucidate how additional patient specific parameters can impact 4DCT imaging. PMID:15895570
Four-dimensional computed tomography: Image formation and clinical protocol
Rietzel, Eike; Pan Tinsu; Chen, George T. Y.
2005-04-01
Respiratory motion can introduce significant errors in radiotherapy. Conventional CT scans as commonly used for treatment planning can include severe motion artifacts that result from interplay effects between the advancing scan plane and object motion. To explicitly include organ/target motion in treatment planning and delivery, time-resolved CT data acquisition (4D Computed Tomography) is needed. 4DCT can be accomplished by oversampled CT data acquisition at each slice. During several CT tube rotations projection data are collected in axial cine mode for the duration of the patient's respiratory cycle (plus the time needed for a full CT gantry rotation). Multiple images are then reconstructed per slice that are evenly distributed over the acquisition time. Each of these images represents a different anatomical state during a respiratory cycle. After data acquisition at one couch position is completed, x rays are turned off and the couch advances to begin data acquisition again until full coverage of the scan length has been obtained. Concurrent to CT data acquisition the patient's abdominal surface motion is recorded in precise temporal correlation. To obtain CT volumes at different respiratory states, reconstructed images are sorted into different spatio-temporally coherent volumes based on respiratory phase as obtained from the patient's surface motion. During binning, phase tolerances are chosen to obtain complete volumetric information since images at different couch positions are reconstructed at different respiratory phases. We describe 4DCT image formation and associated experiments that characterize the properties of 4DCT. Residual motion artifacts remain due to partial projection effects. Temporal coherence within resorted 4DCT volumes is dominated by the number of reconstructed images per slice. The more images are reconstructed, the smaller phase tolerances can be for retrospective sorting. From phantom studies a precision of about 2.5 mm for quasiregular motion and typical respiratory periods could be concluded. A protocol for 4DCT scanning was evaluated and clinically implemented at the MGH. Patient data are presented to elucidate how additional patient specific parameters can impact 4DCT imaging.
Four-dimensional Localization and the Iterative Ensemble Kalman Smoother
NASA Astrophysics Data System (ADS)
Bocquet, M.
2015-12-01
The iterative ensemble Kalman smoother (IEnKS) is a data assimilation method meant for efficiently tracking the state ofnonlinear geophysical models. It combines an ensemble of model states to estimate the errors similarly to the ensemblesquare root Kalman filter, with a 4D-variational analysis performed within the ensemble space. As such it belongs tothe class of ensemble variational methods. Recently introduced 4DEnVar or the 4D-LETKF can be seen as particular casesof the scheme. The IEnKS was shown to outperform 4D-Var, the ensemble Kalman filter (EnKF) and smoother, with low-ordermodels in all investigated dynamical regimes. Like any ensemble method, it could require the use of localization of theanalysis when the state space dimension is high. However, localization for the IEnKS is not as straightforward as forthe EnKF. Indeed, localization needs to be defined across time, and it needs to be as much as possible consistent withthe dynamical flow within the data assimilation variational window. We show that a Liouville equation governs the timeevolution of the localization operator, which is linked to the evolution of the error correlations. It is argued thatits time integration strongly depends on the forecast dynamics. Using either covariance localization or domainlocalization, we propose and test several localization strategies meant to address the issue: (i) a constant and uniformlocalization, (ii) the propagation through the window of a restricted set of dominant modes of the error covariancematrix, (iii) the approximate propagation of the localization operator using model covariant local domains. Theseschemes are illustrated on the one-dimensional Lorenz 40-variable model.
A four-dimensional photon detector for PET application
NASA Astrophysics Data System (ADS)
Morrocchi, M.; Ambrosi, G.; Bisogni, M. G.; Boretto, M.; Bosi, F.; Cerello, P.; Del Guerra, A.; Ionica, M.; Liu, B.; Pennazio, F.; Piliero, M. A.; Pirrone, G.; Postolache, V.; Wheadon, R.
2016-03-01
We analyzed a photon detector for positron emission tomography with high spatial resolution and depth of interaction capability. The detector is composed of a monolithic LYSO scintillator crystal coupled on top and bottom sides to two custom SiPM arrays. We investigated the ability to reconstruct the DOI of the 511 keV photon comparing the number of triggered SiPMs on the two sides of the module. Acquisitions were performed scanning the lateral surface of the crystal with a collimated 511 keV photon beam at different incident positions. A standard deviation of 1.5 mm in depth of interaction was obtained at the center of the module.
Photon gating in four-dimensional ultrafast electron microscopy
Hassan, Mohammed T.; Liu, Haihua; Baskin, John Spencer; Zewail, Ahmed H.
2015-01-01
Ultrafast electron microscopy (UEM) is a pivotal tool for imaging of nanoscale structural dynamics with subparticle resolution on the time scale of atomic motion. Photon-induced near-field electron microscopy (PINEM), a key UEM technique, involves the detection of electrons that have gained energy from a femtosecond optical pulse via photon–electron coupling on nanostructures. PINEM has been applied in various fields of study, from materials science to biological imaging, exploiting the unique spatial, energy, and temporal characteristics of the PINEM electrons gained by interaction with a “single” light pulse. The further potential of photon-gated PINEM electrons in probing ultrafast dynamics of matter and the optical gating of electrons by invoking a “second” optical pulse has previously been proposed and examined theoretically in our group. Here, we experimentally demonstrate this photon-gating technique, and, through diffraction, visualize the phase transition dynamics in vanadium dioxide nanoparticles. With optical gating of PINEM electrons, imaging temporal resolution was improved by a factor of 3 or better, being limited only by the optical pulse widths. This work enables the combination of the high spatial resolution of electron microscopy and the ultrafast temporal response of the optical pulses, which provides a promising approach to attain the resolution of few femtoseconds and attoseconds in UEM. PMID:26438835
Finite states in four-dimensional quantized gravity
NASA Astrophysics Data System (ADS)
Eyo Ita, Eyo, III
2008-06-01
This is the first in a series of papers outlining an algorithm to explicitly construct finite quantum states of the full theory of gravity in Ashtekar variables. The algorithm is based upon extending some properties of a special state, the Kodama state for pure gravity with cosmological term, to matter-coupled models. We then illustrate a prescription for nonperturbatively constructing the generalized Kodama states, in preparation for subsequent works in this series. We also introduce the concept of the semiclassical-quantum correspondence (SQC). We express the quantum constraints of the full theory as a system of equations to be solved for the constituents of the 'phase' of the wavefunction. Additionally, we provide a variety of representations of the generalized Kodama states including a generalization of the topological instanton term to include matter fields, for which we present arguments for the field-theoretical analogue of cohomology on infinite-dimensional spaces. We demonstrate that the Dirac, reduced phase space and geometric quantization procedures are all equivalent for these generalized Kodama states as a natural consequence of the SQC. We relegate the method of the solution to the constraints and other associated ramifications of the generalized Kodama states to separate works.
From the Hensen net toward four-dimensional biological oceanography
NASA Astrophysics Data System (ADS)
Wiebe, Peter H.; Benfield, Mark C.
2003-01-01
The development of quantitative zooplankton collecting systems began with Hensen (1887 Berichte der Kommssion wissenschaftlichen Untersuchung der deutschen Meere in Kiel5, 1-107; 1895 Ergebnisse der Plankton-Expedition der Humbolt-Stiftung. Kiel and Leipzig: Lipsius and Tischer ). Non-opening closing nets, opening closing nets (mostly messenger based), high-speed samplers, and planktobenthos net systems all had their start in his era - the late 1800s and early 1900s. This was also an era in which many of the fundamental questions about the structure and dynamics of the plankton in the worlds oceans were first posed. Fewer new systems were introduced between 1912 and 1950 apparently due in part to the two World Wars. The continuous plankton recorder stands out as a truly innovative device developed during this period ( Hardy 1926b Nature, London118, 630 ). Resurgence in development of mechanically-based instruments occurred during the 1950s and 1960s. A new lineage of high-speed samplers, the Gulf series, began in the 1950s and a number of variants were developed in the 1960s and 1970s. Net systems specifically designed to collect neuston first appeared in the late 1950s. During the 1960s, many focused field and experimental tank experiments were carried out to investigate the hydrodynamics of nets, and much of our knowledge concerning net design and construction criteria was developed. The advent of reliable electrical conducting cables and electrically-based control systems during this same period gave rise first to a variety of cod-end samplers and then to the precursors of the acoustically and electronically-controlled multi-net systems and environmental sensors, which appeared in the 1970s. The decade of the 1970s saw a succession of multi-net systems based both on the Bé multiple plankton sampler and on the Tucker trawl. The advent of the micro-computer stimulated and enabled the development of sophisticated control and data logging electronics for these systems in the 1980s. In the 1990s, acoustic and optical technologies gave rise to sensor systems that either complement multiple net systems or are deployed without nets. Multi-sensor systems with high data telemetry rates through electro-optical cable are now being deployed in towed bodies and on remotely operated vehicles. In the offing are new molecular technologies to identify species in situ, and realtime data analysis, image processing, and 3D/4D display. In the near future, it is likely that the use of multi-sensor systems deployed on autonomous vehicles will yield world wide coverage of the distribution and abundance of zooplankton.
Four-Dimensional Quantum Hall Effect with Ultracold Atoms
NASA Astrophysics Data System (ADS)
Price, H. M.; Zilberberg, O.; Ozawa, T.; Carusotto, I.; Goldman, N.
2015-11-01
We propose a realistic scheme to detect the 4D quantum Hall effect using ultracold atoms. Based on contemporary technology, motion along a synthetic fourth dimension can be accomplished through controlled transitions between internal states of atoms arranged in a 3D optical lattice. From a semiclassical analysis, we identify the linear and nonlinear quantized current responses of our 4D model, relating these to the topology of the Bloch bands. We then propose experimental protocols, based on current or center-of-mass-drift measurements, to extract the topological second Chern number. Our proposal sets the stage for the exploration of novel topological phases in higher dimensions.
String theory, supergravity and four-dimensional field theories
NASA Astrophysics Data System (ADS)
Burrington, Benjamin A.
In this dissertation I present some of the basic computations in string theory and supergravity with an eye for their use in AdS/CFT. I then go on to present several investigations centering around the framework of dualities between gauge theory and gravity systems. In chapters 2, 3, and 4 we consider several 10D solutions. Chapter 2 deals with the inclusion of D7 branes in a D3 brane background, which amounts to adding fundamental matter in the gauge theory dual. We consider including the gravitational backreaction of the D7 branes in these solutions. In chapter 3, we consider modifications to the 6D space transverse to a stack of D3 branes. The 6D spaces that we consider are cones over the so called Y p,q geometries. We consider a geometric deformation for each of these spaces which explicitly breaks a U(1) isometry. In chapter 4, the leading Regge behavior string states are examined. We calculate the effective coupling of such string states to the five form and metric in a flat space background, and obtain an effective Lagrangian. Using this Lagrangian, we examine the energy, spin and angular momentum of these states in the AdS 5 x S5 background which is then compared to the semiclassical analysis of the literature. In chapters 5 and 6, we turn to discussions of the AdS5 factor. The Karch Randall scenario, a brane world scenario based oil AdS4 slices of AdS5 naturally suggests considering transparent boundary conditions for the field theory in AdS4. In chapter 5 we show that with these boundary conditions, a mass is induced for the graviphoton, and that this mass is in the correct proportion to the graviton mass (studied in the literature) to preserve supersymmetry. In chapter 6 we examine black hole solutions in AdS5. The presence of the black hole breaks some of the global supersymmetries (present in pure AdS5) which we use to generate the superpartners to these black holes. Using boundary counter term techniques, we find the mass, angular momentum, and charge of these superpartners and use this to determine the representation of the AdS5 superalgebra that these black holes belong to. In chapter 7 and 8 we turn to the field theory side of AdS/CFT. Here, we consider certain discrete symmetries of these field theories. The discrete symmetries are dual to the number operators for certain wrapped branes. We find that the generators for these discrete symmetries do not commute. This feature of wrapped branes was uncovered in the literature for the field theory dual to S5/Z3 . In addition to generalizing this to certain classes of Yp,q geometries in chapter 7, we also find that the non conformal case admits a centrally extended Heisenberg group structure in chapter 8.
Hopf Bifurcation in a New Four-Dimensional Hyperchaotic System
NASA Astrophysics Data System (ADS)
Li, Xin; Yan, Zhen-Ya
2015-08-01
In this paper, the Hopf bifurcation in a new hyperchaotic system is studied. Based on the first Lyapunov coefficient theory and symbolic computation, the conditions of supercritical and subcritical bifurcation in the new hyperchaotic system are obtained. Numerical simulations are used to illustrate some main results. Supported by National Key Bsic Research Program of China under Grant No. 2011CB302400
Route planning in a four-dimensional environment
NASA Technical Reports Server (NTRS)
Slack, M. G.; Miller, D. P.
1987-01-01
Robots must be able to function in the real world. The real world involves processes and agents that move independently of the actions of the robot, sometimes in an unpredictable manner. A real-time integrated route planning and spatial representation system for planning routes through dynamic domains is presented. The system will find the safest most efficient route through space-time as described by a set of user defined evaluation functions. Because the route planning algorthims is highly parallel and can run on an SIMD machine in O(p) time (p is the length of a path), the system will find real-time paths through unpredictable domains when used in an incremental mode. Spatial representation, an SIMD algorithm for route planning in a dynamic domain, and results from an implementation on a traditional computer architecture are discussed.
Observational Needs for Four-Dimensional Air Quality Characterization
Surface-based monitoring programs provide the foundation for associating air pollution and causal effects in human health studies, and they support the development of air quality standards and the preparation of emission reduction strategies. While surface oriented networks remai...
Feasibility of four-dimensional conformal planning for robotic radiosurgery
Schlaefer, A.; Fisseler, J.; Dieterich, S.; Shiomi, H.; Cleary, K.; Schweikard, A.
2005-12-15
Organ motion can have a severe impact on the dose delivered by radiation therapy, and different procedures have been developed to address its effects. Conventional techniques include breath hold methods and gating. A different approach is the compensation for target motion by moving the treatment beams synchronously. Practical results have been reported for robot based radiosurgery, where a linear accelerator mounted on a robotic arm delivers the dose. However, not all organs move in the same way, which results in a relative motion of the beams with respect to the body and the tissues in the proximity of the tumor. This relative motion can severely effect the dose delivered to critical structures. We propose a method to incorporate motion in the treatment planning for robotic radiosurgery to avoid potential overdosing of organs surrounding the target. The method takes into account the motion of all considered volumes, which is discretized for dose calculations. Similarly, the beam motion is taken into account and the aggregated dose coefficient over all discrete steps is used for planning. We simulated the treatment of a moving target with three different planning methods. First, we computed beam weights based on a 3D planning situation and simulated treatment with organ motion and the beams moving synchronously to the target. Second, beam weights were computed by the 4D planning method incorporating the organ and beam motion and treatment was simulated for beams moving synchronously to the target. Third, the beam weights were determined by the 4D planning method with the beams fixed during planning and simulation. For comparison we also give results for the 3D treatment plan if there was no organ motion and when the plan is delivered by fixed beams in the presence of organ motion. The results indicate that the new 4D method is preferable and can further improve the overall conformality of motion compensated robotic radiosurgery.
Kikuchi ultrafast nanodiffraction in four-dimensional electron microscopy.
Yurtsever, Aycan; Zewail, Ahmed H
2011-02-22
Coherent atomic motions in materials can be revealed using time-resolved X-ray and electron Bragg diffraction. Because of the size of the beam used, typically on the micron scale, the detection of nanoscale propagating waves in extended structures hitherto has not been reported. For elastic waves of complex motions, Bragg intensities contain all polarizations and they are not straightforward to disentangle. Here, we introduce Kikuchi diffraction dynamics, using convergent-beam geometry in an ultrafast electron microscope, to selectively probe propagating transverse elastic waves with nanoscale resolution. It is shown that Kikuchi band shifts, which are sensitive only to the tilting of atomic planes, reveal the resonance oscillations, unit cell angular amplitudes, and the polarization directions. For silicon, the observed wave packet temporal envelope (resonance frequency of 33 GHz), the out-of-phase temporal behavior of Kikuchi's edges, and the magnitude of angular amplitude (0.3 mrad) and polarization elucidate the nature of the motion: one that preserves the mass density (i.e., no compression or expansion) but leads to sliding of planes in the antisymmetric shear eigenmode of the elastic waveguide. As such, the method of Kikuchi diffraction dynamics, which is unique to electron imaging, can be used to characterize the atomic motions of propagating waves and their interactions with interfaces, defects, and grain boundaries at the nanoscale. PMID:21245348
Four-dimensional multi-site two-photon excitation
NASA Astrophysics Data System (ADS)
Daria, Vincent R.; Stricker, Christian; Bowman, Richard; Bachor, Hans-A.; Redman, Stephen
2010-02-01
We use the holographic method to project an arbitrary array of diffraction-limited focal spots suitable for multi-site twophoton excitation. The spot array can be projected arbitrarily within a three-dimensional (3D) volume, while the fourth dimension in time is attributed to high temporal resolution via high-speed non-iterative calculation of the hologram using a video graphics accelerator board. We show that the spots have sufficient energy and spatiotemporal photon density for localized two-photon excitation at individual spots in the array. The significance of this work points to 3D microscopy, non-linear micro-fabrication, volume holographic optical storage and biomedical instrumentation. In neuroscience, timecritical release of neurotransmitters at multiple sites within complex dendritic trees of neurons can lead to insights on the mechanisms of information processing in the brain.
Four-Dimensional Entropy from Three-Dimensional Gravity.
Carlip, S
2015-08-14
At the horizon of a black hole, the action of (3+1)-dimensional loop quantum gravity acquires a boundary term that is formally identical to an action for three-dimensional gravity. I show how to use this correspondence to obtain the entropy of the (3+1)-dimensional black hole from well-understood conformal field theory computations of the entropy in (2+1)-dimensional de Sitter space. PMID:26317707
Four-dimensional space groups for pedestrians: composite structures.
Sun, Junliang; Lee, Stephen; Lin, Jianhua
2007-10-01
Higher-dimensional crystals have been studied for the last thirty years. However, most practicing chemists, materials scientists, and crystallographers continue to eschew the use of higher-dimensional crystallography in their work. Yet it has become increasingly clear in recent years that the number of higher-dimensional systems continues to grow from hundreds to as many as a thousand different compounds. Part of the problem has to do with the somewhat opaque language that has developed over the past decades to describe higher-dimensional systems. This language, while well-suited to the specialist, is too sophisticated for the neophyte wishing to enter the field, and as such can be an impediment. This Focus Review hopes to address this issue. The goal of this article is to show the regular chemist or materials scientist that knowledge of regular 3D crystallography is all that is really necessary to understand 4D crystal systems. To this end, we have couched higher-dimensional composite structures in the language of ordinary 3D crystals. In particular, we developed the principle of complementarity, which allows one to identify correctly 4D space groups solely from examination of the two 3D components that make up a typical 4D composite structure. PMID:17886829
Four-dimensional coronary morphology and computational hemodynamics
NASA Astrophysics Data System (ADS)
Wahle, Andreas; Mitchell, Steven C.; Ramaswamy, Sharan D.; Chandran, Krishnan B.; Sonka, Milan
2001-07-01
Conventional reconstructions from intravascular ultrasound (IVUS) stack the frames as acquired during the pullback of the catheter to form a straight three-dimensional volume, thus neglecting the vessel curvature and merging images from different heart phases. We are developing a comprehensive system for fusion of the IVUS data with the pullback path as determined from x-ray angiography, to create a geometrically accurate 4-D (3-D plus time) model of the coronary vasculature as basis for computational hemodynamics. The overall goal of our work is to correlate shear stress with plaque thickness. The IVUS data are obtained in a single pullback using an automated pullback device; the frames are afterwards assigned to their respective heart phases based upon the ECG signal. A set of 3-D models is reconstructed by fusion of IVUS and angiographic data corresponding to the same ECG-gated heart phase; methods of computational fluid dynamics (CFD) are applied to obtain important hemodynamic data. Combining these models yields the final 4-D reconstruction. Visualization is performed using the platform-independent VRML standard for a user-friendly manipulation of the scene. An extension for virtual angioscopy allows an easy assessment of the vessel features within their local context. Validation was successfully performed both in-vitro and in-vivo.
Four-dimensional multi-site photolysis of caged neurotransmitters
Go, Mary Ann; To, Minh-Son; Stricker, Christian; Redman, Stephen; Bachor, Hans-A.; Stuart, Greg J.; Daria, Vincent R.
2013-01-01
Neurons receive thousands of synaptic inputs that are distributed in space and time. The systematic study of how neurons process these inputs requires a technique to stimulate multiple yet highly targeted points of interest along the neuron's dendritic tree. Three-dimensional multi-focal patterns produced via holographic projection combined with two-photon photolysis of caged compounds can provide for highly localized release of neurotransmitters within each diffraction-limited focus, and in this way emulate simultaneous synaptic inputs to the neuron. However, this technique so far cannot achieve time-dependent stimulation patterns due to fundamental limitations of the hologram-encoding device and other factors that affect the consistency of controlled synaptic stimulation. Here, we report an advanced technique that enables the design and application of arbitrary spatio-temporal photostimulation patterns that resemble physiological synaptic inputs. By combining holographic projection with a programmable high-speed light-switching array, we have overcome temporal limitations with holographic projection, allowing us to mimic distributed activation of synaptic inputs leading to action potential generation. Our experiments uniquely demonstrate multi-site two-photon glutamate uncaging in three dimensions with submillisecond temporal resolution. Implementing this approach opens up new prospects for studying neuronal synaptic integration in four dimensions. PMID:24348330
GRAM-86 - FOUR DIMENSIONAL GLOBAL REFERENCE ATMOSPHERE MODEL
NASA Technical Reports Server (NTRS)
Johnson, D.
1994-01-01
The Four-D Global Reference Atmosphere program was developed from an empirical atmospheric model which generates values for pressure, density, temperature, and winds from surface level to orbital altitudes. This program can be used to generate altitude profiles of atmospheric parameters along any simulated trajectory through the atmosphere. The program was developed for design applications in the Space Shuttle program, such as the simulation of external tank re-entry trajectories. Other potential applications would be global circulation and diffusion studies, and generating profiles for comparison with other atmospheric measurement techniques, such as satellite measured temperature profiles and infrasonic measurement of wind profiles. The program is an amalgamation of two empirical atmospheric models for the low (25km) and the high (90km) atmosphere, with a newly developed latitude-longitude dependent model for the middle atmosphere. The high atmospheric region above 115km is simulated entirely by the Jacchia (1970) model. The Jacchia program sections are in separate subroutines so that other thermosphericexospheric models could easily be adapted if required for special applications. The atmospheric region between 30km and 90km is simulated by a latitude-longitude dependent empirical model modification of the latitude dependent empirical model of Groves (1971). Between 90km and 115km a smooth transition between the modified Groves values and the Jacchia values is accomplished by a fairing technique. Below 25km the atmospheric parameters are computed by the 4-D worldwide atmospheric model of Spiegler and Fowler (1972). This data set is not included. Between 25km and 30km an interpolation scheme is used between the 4-D results and the modified Groves values. The output parameters consist of components for: (1) latitude, longitude, and altitude dependent monthly and annual means, (2) quasi-biennial oscillations (QBO), and (3) random perturbations to partially simulate the variability due to synoptic, diurnal, planetary wave, and gravity wave variations. Quasi-biennial and random variation perturbations are computed from parameters determined by various empirical studies and are added to the monthly mean values. The UNIVAC version of GRAM is written in UNIVAC FORTRAN and has been implemented on a UNIVAC 1110 under control of EXEC 8 with a central memory requirement of approximately 30K of 36 bit words. The GRAM program was developed in 1976 and GRAM-86 was released in 1986. The monthly data files were last updated in 1986. The DEC VAX version of GRAM is written in FORTRAN 77 and has been implemented on a DEC VAX 11/780 under control of VMS 4.X with a central memory requirement of approximately 100K of 8 bit bytes. The GRAM program was originally developed in 1976 and later converted to the VAX in 1986 (GRAM-86). The monthly data files were last updated in 1986.
Solutions of minimal four-dimensional de Sitter supergravity
NASA Astrophysics Data System (ADS)
Gutowski, J. B.; Sabra, W. A.
2010-12-01
Pseudo-supersymmetric solutions of minimal N = 2, D = 4 de Sitter supergravity are classified using spinorial geometry techniques. We find three classes of solutions. The first class of solution consists of geometries which are fibrations over a three-dimensional manifold equipped with a Gauduchon-Tod structure. The second class of solution is the cosmological Majumdar-Papapetrou solution of Kastor and Traschen, and the third corresponds to gravitational waves propagating in the Nariai cosmology.
A Four Dimensional Spatio-Temporal Analysis of an Agricultural Dataset.
Donald, Margaret R; Mengersen, Kerrie L; Young, Rick R
2015-01-01
While a variety of statistical models now exist for the spatio-temporal analysis of two-dimensional (surface) data collected over time, there are few published examples of analogous models for the spatial analysis of data taken over four dimensions: latitude, longitude, height or depth, and time. When taking account of the autocorrelation of data within and between dimensions, the notion of closeness often differs for each of the dimensions. Here, we consider a number of approaches to the analysis of such a dataset, which arises from an agricultural experiment exploring the impact of different cropping systems on soil moisture. The proposed models vary in their representation of the spatial correlation in the data, the assumed temporal pattern and choice of conditional autoregressive (CAR) and other priors. In terms of the substantive question, we find that response cropping is generally more effective than long fallow cropping in reducing soil moisture at the depths considered (100 cm to 220 cm). Thus, if we wish to reduce the possibility of deep drainage and increased groundwater salinity, the recommended cropping system is response cropping. PMID:26513746
Lamata, Pablo; Pitcher, Alex; Krittian, Sebastian; Nordsletten, David; Bissell, Malenka M; Cassar, Thomas; Barker, Alex J; Markl, Michael; Neubauer, Stefan; Smith, Nicolas P
2014-01-01
Purpose To describe the assessment of the spatiotemporal distribution of relative aortic pressure quantifying the magnitude of its three major components. Methods Nine healthy volunteers and three patients with aortic disease (bicuspid aortic valve, dissection, and Marfan syndrome) underwent 4D-flow CMR. Spatiotemporal pressure maps were computed from the CMR flow fields solving the pressure Poisson equation. The individual components of pressure were separated into time-varying inertial (“transient”), spatially varying inertial (“convective”), and viscous components. Results Relative aortic pressure is primarily caused by transient effects followed by the convective and small viscous contributions (64.5, 13.6, and 0.3 mmHg/m, respectively, in healthy subjects), although regional analysis revealed prevalent convective effects in specific contexts, e.g., Sinus of Valsalva and aortic arch at instants of peak velocity. Patients showed differences in peak transient values and duration, and localized abrupt convective changes explained by abnormalities in aortic geometry, including the presence of an aneurysm, a pseudo-coarctation, the inlet of a dissection, or by complex flow patterns. Conclusion The evaluation of the three components of relative pressure enables the quantification of mechanistic information for understanding and stratifying aortic disease, with potential future implications for guiding therapy. Magn Reson Med 72:1162–1169, 2014. © 2013 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:24243444
Virtual four-dimensional imaging of lung parenchyma by optical coherence tomography in mice
NASA Astrophysics Data System (ADS)
Meissner, Sven; Tabuchi, Arata; Mertens, Michael; Kuebler, Wolfgang M.; Koch, Edmund
2010-05-01
In this feasibility study, we present a method for virtual 4-D imaging of healthy and injured subpleural lung tissue in the ventilated mouse. We use triggered swept source optical coherence tomography (OCT) with an A-scan frequency of 20 kHz to image murine subpleural alveoli during the inspiratory phase. The data acquisition is gated to the ventilation pressure to take single B-scans in each respiration cycle for different pressure levels. The acquired B-scans are combined off-line into one volume scan for each pressure level. The air fraction in healthy lungs and injured lungs is measured using 2-D OCT en-face images. Upon lung inspiration from 2 to 12 cmH2O ventilation pressure, the air fraction increases in healthy lungs by up to 11% and in injured lungs by 8%. This expansion correlates well with results of previous studies, reporting increased alveolar area with increased ventilation pressures. We demonstrate that OCT is a useful tool to investigate alveolar dynamics in spatial dimensions.
NASA Astrophysics Data System (ADS)
Széplaky, Dávid; Varga, Augustín
2016-06-01
The contribution describes the principle of the FENIX program operation, which was designed to determine the temperature field of the transit pipeline for the transportation of natural gas. The program itself consists of several modules which are reciprocally linked. The basis of the program is the elementary balance method by means of which the unsteady heat transfer is assigned in several layers in different directions. The first step was to assess both the pressure and temperature of the natural gas mode, the second step is to determine the heat transfer through the walls of the pipes, and the last one is to determine the distribution of the temperature field in the surroundings of the pipeline.
A four-dimensional X-ray tomographic microscopy study of bubble growth in basaltic foam.
Baker, Don R; Brun, Francesco; O'Shaughnessy, Cedrick; Mancini, Lucia; Fife, Julie L; Rivers, Mark
2012-01-01
Understanding the influence of bubble foams on magma permeability and strength is critical to investigations of volcanic eruption mechanisms. Increasing foam porosity decreases strength, enhancing the probability of an eruption. However, higher porosities lead to larger permeabilities, which can lessen the eruption hazard. Here we measure bubble size and wall thickness distributions, as well as connectivity, and calculate permeabilities and tensile strengths of basaltic foams imaged by synchrotron X-ray tomographic microscopy during bubble growth in hydrated basaltic melts. Rapid vesiculation produces porous foams whose fragmentation thresholds are only 5-6 MPa and whose permeabilities increase from approximately 1×10(-10) to 1×10(-9) m(2) between 10 and 14 s despite decreasing connectivity between bubbles. These results indicate that basaltic magmas are most susceptible to failure immediately upon vesiculation and at later times, perhaps only 10's of seconds later, permeability increases may lessen the hazard of explosive, basaltic, Plinian eruptions. PMID:23072805
Arthropod Distribution in a Tropical Rainforest: Tackling a Four Dimensional Puzzle
Basset, Yves; Cizek, Lukas; Cuénoud, Philippe; Didham, Raphael K.; Novotny, Vojtech; Ødegaard, Frode; Roslin, Tomas; Tishechkin, Alexey K.; Schmidl, Jürgen; Winchester, Neville N.; Roubik, David W.; Aberlenc, Henri-Pierre; Bail, Johannes; Barrios, Héctor; Bridle, Jonathan R.; Castaño-Meneses, Gabriela; Corbara, Bruno; Curletti, Gianfranco; Duarte da Rocha, Wesley; De Bakker, Domir; Delabie, Jacques H. C.; Dejean, Alain; Fagan, Laura L.; Floren, Andreas; Kitching, Roger L.; Medianero, Enrique; Gama de Oliveira, Evandro; Orivel, Jérôme; Pollet, Marc; Rapp, Mathieu; Ribeiro, Sérvio P.; Roisin, Yves; Schmidt, Jesper B.; Sørensen, Line; Lewinsohn, Thomas M.; Leponce, Maurice
2015-01-01
Quantifying the spatio-temporal distribution of arthropods in tropical rainforests represents a first step towards scrutinizing the global distribution of biodiversity on Earth. To date most studies have focused on narrow taxonomic groups or lack a design that allows partitioning of the components of diversity. Here, we consider an exceptionally large dataset (113,952 individuals representing 5,858 species), obtained from the San Lorenzo forest in Panama, where the phylogenetic breadth of arthropod taxa was surveyed using 14 protocols targeting the soil, litter, understory, lower and upper canopy habitats, replicated across seasons in 2003 and 2004. This dataset is used to explore the relative influence of horizontal, vertical and seasonal drivers of arthropod distribution in this forest. We considered arthropod abundance, observed and estimated species richness, additive decomposition of species richness, multiplicative partitioning of species diversity, variation in species composition, species turnover and guild structure as components of diversity. At the scale of our study (2km of distance, 40m in height and 400 days), the effects related to the vertical and seasonal dimensions were most important. Most adult arthropods were collected from the soil/litter or the upper canopy and species richness was highest in the canopy. We compared the distribution of arthropods and trees within our study system. Effects related to the seasonal dimension were stronger for arthropods than for trees. We conclude that: (1) models of beta diversity developed for tropical trees are unlikely to be applicable to tropical arthropods; (2) it is imperative that estimates of global biodiversity derived from mass collecting of arthropods in tropical rainforests embrace the strong vertical and seasonal partitioning observed here; and (3) given the high species turnover observed between seasons, global climate change may have severe consequences for rainforest arthropods. PMID:26633187
NASA Technical Reports Server (NTRS)
Takano, Kenji
1996-01-01
An oceanic data assimilation system which allows to utilize the forthcoming Tropical Rainfall Measuring Mission (TRMM) data has been developed and applied to the Pacific Ocean to produce the velocity field. The assimilated data will be indispensable to examine the effects of rainfall and its variability on the structure and circulation of the tropical oceans and to assess the impact of global warming due to the increase of carbon dioxide on the ocean circulation system and the marine pollution caused by oil spill and ocean damping of radionuclide. The data will also provide the verification for the oceanic and ocean-atmosphere coupled General Circulation Models (GCM's). The system consists of oceanic GCM, analysis scheme and data. In the system the flow field has been determined to be physically consistent with the observed density field and the sea surface winds derived from the Special Sensor Microwave Imagery (SSM/I) data which drive the ocean current. The time integration has been performed for five years until the flow field near the surface attained the steady state starting from the rest ocean with observed temperature and salinity fields, and the SSM/I surface wind velocity. The resultant flow field showed high producibility of the system. Especially the flow near the ocean surface agreed well with available observed data. The system, for the first time, succeeded to produce the eastward subtropical current which has been discovered in the joint investigation on Kuroshio current (CSK) in the 1960s. To verify the quality of the flow field a trajectory analysis has been carried out and compared with the Algos buoy data. BRIEF DESCRIPTION OF THE DATA ASSIMILATION SYSTEM ## Oceanic GCM and analysis scheme--The basic equations are much the same as used for the GCM's, except for the Newtonian damping terms introduced into the prediction equations for the potential temperature and salinity to maintain these fields as observed. The C grid of 2'lat. by 2'long. in horizontal and the 11 vertical levels are applied to the entire Pacific Ocean. At the east and west ocean boundaries the periodic boundary conditions are applied creating fictitious ocean there. The SMAC Method is used to increase the accuracy of mass conservation. * Data--The JODC temperature and salinity data obtained from 1906 to 1988 are used in the system between Long.100'E. and 60'W. The surface wind data are derived from the SSM/I data by Dr-R. Atlas of NASA/GSFC. The data set contains every 6 hours data from July 1987 to June 1989 on the grid of 2'lat. by 2.5'long. The averaged for the whole period and then interpolated into the 2'lat. by 2'long. grid data are used to force the system. The sea bottom topography data was based on the General Bathymetric Chart of the Ocean (GEBCO) supplied by the Canadian Hydrographic Service under contract with the International Hydrographic Organization and International Oceanographic Commission of UNESCO.
Multi-objective four-dimensional vehicle motion planning in large dynamic environments.
Wu, Paul P-Y; Campbell, Duncan; Merz, Torsten
2011-06-01
This paper presents Multi-Step A∗ (MSA∗), a search algorithm based on A∗ for multi-objective 4-D vehicle motion planning (three spatial and one time dimensions). The research is principally motivated by the need for offline and online motion planning for autonomous unmanned aerial vehicles (UAVs). For UAVs operating in large dynamic uncertain 4-D environments, the motion plan consists of a sequence of connected linear tracks (or trajectory segments). The track angle and velocity are important parameters that are often restricted by assumptions and a grid geometry in conventional motion planners. Many existing planners also fail to incorporate multiple decision criteria and constraints such as wind, fuel, dynamic obstacles, and the rules of the air. It is shown that MSA∗ finds a cost optimal solution using variable length, angle, and velocity trajectory segments. These segments are approximated with a grid-based cell sequence that provides an inherent tolerance to uncertainty. The computational efficiency is achieved by using variable successor operators to create a multiresolution memory-efficient lattice sampling structure. The simulation studies on the UAV flight planning problem show that MSA∗ meets the time constraints of online replanning and finds paths of equivalent cost but in a quarter of the time (on average) of a vector neighborhood-based A∗. PMID:20851795
FOUR-DIMENSIONAL TRANSPORT OF GALACTIC COSMIC RAYS IN THE OUTER HELIOSPHERE AND HELIOSHEATH
Florinski, V.; Pogorelov, N. V. E-mail: np0002@uah.edu
2009-08-10
2008 marked the beginning of sunspot cycle 24 in the inner heliosphere. Intensities of galactic hydrogen and helium measured by the Voyagers in 2008 were the highest ever recorded and believed to be approaching the interstellar values. We investigate transport of galactic cosmic ray (GCR) protons in the three-dimensional, asymmetric heliosphere, including the inner heliosheath region, by tracking stochastic phase-space trajectories of Parker equation under steady plasma background conditions. The latter is calculated from a three-dimensional MHD model of the global heliosphere that takes into account the effect of neutral hydrogen atoms. The model is applied to quiet solar wind (SW) conditions appropriate for the 2008-2009 solar minimum. Model-derived cosmic-ray spectra and radial gradients are reviewed in the context of Voyager observations in the heliosheath. It is shown that the heliosheath is an important modulation barrier for lower energy ions. Radial cosmic-ray gradients in the heliosheath are expected to be small in the directions of the Voyagers (1.5%-1.8% per AU at 180 MeV). In our model the termination shock does not accelerate GCR ions very efficiently, and their intensities in the heliosheath never exceed interstellar values. Analysis of cosmic-ray residence times in different parts in the heliosphere shows that, prior to their detection, ions spend 3-6 times longer transiting the heliosheath and the heliotail than they spend in the supersonic SW.
A proper fixed functional for four-dimensional Quantum Einstein Gravity
NASA Astrophysics Data System (ADS)
Demmel, Maximilian; Saueressig, Frank; Zanusso, Omar
2015-08-01
Realizing a quantum theory for gravity based on Asymptotic Safety hinges on the existence of a non-Gaussian fixed point of the theory's renormalization group flow. In this work, we use the functional renormalization group equation for the effective average action to study the fixed point underlying Quantum Einstein Gravity at the functional level including an infinite number of scale-dependent coupling constants. We formulate a list of guiding principles underlying the construction of a partial differential equation encoding the scale-dependence of f( R)-gravity. We show that this equation admits a unique, globally well-defined fixed functional describing the non-Gaussian fixed point at the level of functions of the scalar curvature. This solution is constructed explicitly via a numerical double-shooting method. In the UV, this solution is in good agreement with results from polynomial expansions including a finite number of coupling constants, while it scales proportional to R 2, dressed up with non-analytic terms, in the IR. We demonstrate that its structure is mainly governed by the conformal sector of the flow equation. The relation of our work to previous, partial constructions of similar scaling solutions is discussed.
On the localization of four-dimensional brane-world black holes
NASA Astrophysics Data System (ADS)
Kanti, P.; Pappas, N.; Zuleta, K.
2013-12-01
In the context of brane-world models, we pursue the question of the existence of five-dimensional solutions describing regular black holes localized close to the brane. Employing a perturbed Vaidya-type line-element embedded in a warped fifth dimension, we attempt to localize the extended black-string singularity, and to restore the regularity of the AdS spacetime at a finite distance from the brane by introducing an appropriate bulk energy-momentum tensor. As a source for this bulk matter, we are considering a variety of non-ordinary field-theory models of scalar fields either minimally coupled to gravity, but including non-canonical kinetic terms, mixing terms, derivative interactions and ghosts, or non-minimally coupled to gravity through a general coupling to the Ricci scalar. In all models considered, even in those characterized by a high degree of flexibility, a negative result was reached. Our analysis demonstrates how difficult the analytic construction of a localized brane-world black hole may be in the context of a well-defined field-theory model. Finally, with regard to the question of the existence or not of a static classical black-hole solution on the brane, our analysis suggests that such solutions could in principle exist; however, the associated field configuration itself has to be dynamic.
Efficient cross-modality cardiac four-dimensional active appearance model construction
NASA Astrophysics Data System (ADS)
Zhang, Honghai; Abiose, Ademola K.; Buettner, Elisabeth J.; Birrer, Emily K.; Sonka, Milan; Martins, James B.; Wahle, Andreas
2009-02-01
The efficiency of constructing an active appearance model (AAM) is limited by establishing the independent standard via time-consuming and tedious manual tracing. It is more challenging for 3D and 4D (3D+time) datasets as the smoothness of shape and motion is essential. In this paper, a three-stage pipeline is designed for efficient cross-modality model construction. It utilizes existing AAM and active shape model (ASM) of the left ventricle (LV) for magnetic resonance (MR) datasets to build 4D AAM of the LV for real-time 3D echocardiography (RT3DE) datasets. The first AAM fitting stage uses AAM for MR to fit valid shapes onto the intensity-transformed RT3DE data that resemble low-quality MR data. The fitting is implemented in a 3D phase-by-phase fashion to prevent introducing bias due to different motion patterns related to the two modalities and patient groups. The second global-scale editing stage adjusts fitted shapes by tuning modes of ASM for MR data. The third local-scale editing stage adjusts the fitted volumes at small local regions and produces the final accurate independent standard. By visual inspection, the AAM fitting stage successfully produces results that capture the LV motion - especially its base movement - within the cardiac cycle on 29 of the 32 RT3DE datasets tested. This multi-stage approach can reduce the human effort of the manual tracing by at least 50%. With the model built for a modality A available, this approach is generalizable to constructing the model of the same organ for any other modality B.
Classical and quantum analysis of repulsive singularities in four-dimensional extended supergravity
NASA Astrophysics Data System (ADS)
Gaida, I.; Hollmann, H. R.; Stewart, J. M.
1999-07-01
Non-minimal repulsive singularities (`repulsons') in extended supergravity theories are investigated. The short-distance antigravity properties of the repulsons are tested at the classical and the quantum level by a scalar test-particle. Using a partial wave expansion it is shown that the particle is totally reflected at the origin. A high-frequency incoming particle undergoes a phase shift of icons/Journals/Common/pi" ALT="pi" ALIGN="TOP"/>/2. However, the phase shift for a low-frequency particle depends upon the physical data of the repulson. The curvature singularity at a finite distance rh turns out to be transparent for the scalar test-particle and the coordinate singularity at the origin serves as the repulsive barrier to bounce back the particles.
Ultrashort electron pulses as a four-dimensional diagnosis of plasma dynamics.
Zhu, P F; Zhang, Z C; Chen, L; Li, R Z; Li, J J; Wang, X; Cao, J M; Sheng, Z M; Zhang, J
2010-10-01
We report an ultrafast electron imaging system for real-time examination of ultrafast plasma dynamics in four dimensions. It consists of a femtosecond pulsed electron gun and a two-dimensional single electron detector. The device has an unprecedented capability of acquiring a high-quality shadowgraph image with a single ultrashort electron pulse, thus permitting the measurement of irreversible processes using a single-shot scheme. In a prototype experiment of laser-induced plasma of a metal target under moderate pump intensity, we demonstrated its unique capability of acquiring high-quality shadowgraph images on a micron scale with a-few-picosecond time resolution. PMID:21034089
The pedagogical value of the four-dimensional picture: III. Solutions to Maxwell’s equations
NASA Astrophysics Data System (ADS)
Chubykalo, Andrew E.; Espinoza, Augusto; Kosyakov, B. P.
2016-07-01
We outline a regular way for solving Maxwell’s equations. We take, as the starting point, the notion of vector potentials. The rationale for introducing this notion in electrodynamics is that the set of Maxwell’s equations is seemingly overdetermined. We demonstrate the existence of two fundamental solutions to Maxwell’s equations whose linear combinations comprise the whole variety of classical electromagnetic field configurations.
POD/DEIM reduced-order strategies for efficient four dimensional variational data assimilation
Ştefănescu, R.; Sandu, A.; Navon, I.M.
2015-08-15
This work studies reduced order modeling (ROM) approaches to speed up the solution of variational data assimilation problems with large scale nonlinear dynamical models. It is shown that a key requirement for a successful reduced order solution is that reduced order Karush–Kuhn–Tucker conditions accurately represent their full order counterparts. In particular, accurate reduced order approximations are needed for the forward and adjoint dynamical models, as well as for the reduced gradient. New strategies to construct reduced order based are developed for proper orthogonal decomposition (POD) ROM data assimilation using both Galerkin and Petrov–Galerkin projections. For the first time POD, tensorial POD, and discrete empirical interpolation method (DEIM) are employed to develop reduced data assimilation systems for a geophysical flow model, namely, the two dimensional shallow water equations. Numerical experiments confirm the theoretical framework for Galerkin projection. In the case of Petrov–Galerkin projection, stabilization strategies must be considered for the reduced order models. The new reduced order shallow water data assimilation system provides analyses similar to those produced by the full resolution data assimilation system in one tenth of the computational time.
Emergence of four dimensional quantum mechanics from a deterministic theory in 11 dimensions
NASA Astrophysics Data System (ADS)
Doyen, G.; Drakova, D.
2015-07-01
We develop a deterministic theory which accounts for the coupling of a high dimensional continuum of environmental excitations (called gravonons) to massive particle in a very localized and very weak fashion. For the model presented Schrödinger's equation can be solved practically exactly in 11 spacetime dimensions and the result demonstrates that as a function of time an incoming matter wave incident on a screen extinguishes, except at a single interaction center on the detection screen. This transition is reminiscent of the wave - particle duality arising from the ’’collapse” (also called ’’process one”) postulated in the Copenhagen-von Neumann interpretation. In our theory it is replaced by a sticking process of the particle from the vacuum to the surface of the detection screen. This situation was verified in experiments by using massive molecules. In our theory this ”wave-particle transition” is connected to the different dimensionalities of the space for particle motion and the gravonon dynamics, the latter propagating in the hidden dimensions of 11 dimensional spacetime. The fact that the particle is detected at apparently statistically determined points on the screen is traced back to the weakness and locality of the interaction with the gravonons which allows coupling on the energy shell alone. Although the theory exhibits a completely deterministic ”chooser” mechanism for single site sticking, an apparent statistical character results, as it is found in the experiments, due to small heterogeneities in the atomic and gravonon structures.
NASA Technical Reports Server (NTRS)
Fox, Geoffrey C.; Ou, Chao-Wei
1997-01-01
The approach of this task was to apply leading parallel computing research to a number of existing techniques for assimilation, and extract parameters indicating where and how input/output limits computational performance. The following was used for detailed knowledge of the application problems: 1. Developing a parallel input/output system specifically for this application 2. Extracting the important input/output characteristics of data assimilation problems; and 3. Building these characteristics s parameters into our runtime library (Fortran D/High Performance Fortran) for parallel input/output support.
NASA Astrophysics Data System (ADS)
Ozawa, Tomoki; Price, Hannah M.; Goldman, Nathan; Zilberberg, Oded; Carusotto, Iacopo
2016-04-01
Recent technological advances in integrated photonics have spurred on the study of topological phenomena in engineered bosonic systems. Indeed, the controllability of silicon ring-resonator arrays has opened up new perspectives for building lattices for photons with topologically nontrivial bands and integrating them into photonic devices for practical applications. Here, we push these developments even further by exploiting the different modes of a silicon ring resonator as an extra dimension for photons. Tunneling along this synthetic dimension is implemented via an external time-dependent modulation that allows for the generation of engineered gauge fields. We show how this approach can be used to generate a variety of exciting topological phenomena in integrated photonics, ranging from a topologically-robust optical isolator in a spatially one-dimensional (1D) ring-resonator chain to a driven-dissipative analog of the 4D quantum Hall effect in a spatially 3D resonator lattice. Our proposal paves the way towards the use of topological effects in the design of novel photonic lattices supporting many frequency channels and displaying higher connectivities.
Systematic evaluation of four-dimensional hybrid depth scanning for carbon-ion lung therapy
Mori, Shinichiro; Furukawa, Takuji; Inaniwa, Taku; Zenklusen, Silvan; Nakao, Minoru; Shirai, Toshiyuki; Noda, Koji
2013-03-15
Purpose: Irradiation of a moving target with a scanning beam requires a comprehensive understanding of organ motion as well as a robust dose error mitigation technique. The authors studied the effects of intrafractional respiratory motion for carbon-ion pencil beam scanning with phase-controlled rescanning on dose distributions for lung tumors. To address density variations, they used 4DCT data. Methods: Dose distributions for various rescanning methods, such as simple layer rescanning (LR), volumetric rescanning, and phase-controlled rescanning (PCR), were calculated for a lung phantom and a lung patient studies. To ensure realism, they set the scanning parameters such as scanning velocity and energy variation time to be similar to those used at our institution. Evaluation metrics were determined with regard to clinical relevance, and consisted of (i) phase-controlled rescanning, (ii) sweep direction, (iii) target motion (direction and amplitude), (iv) respiratory cycle, and (v) prescribed dose. Spot weight maps were calculated by using a beam field-specific target volume, which takes account of range variations for respective respiratory phases. To emphasize the impact of intrafractional motion on the dose distribution, respiratory gating was not used. The accumulated dose was calculated by applying a B-spline-based deformable image registration, and the results for phase-controlled layered rescanning (PCR{sub L}) and phase-controlled volumetric rescanning (PCR{sub V}) were compared. Results: For the phantom study, simple LR was unable to improve the dose distributions for an increased number of rescannings. The phase-controlled technique without rescanning (1 Multiplication-Sign PCR{sub L} and 1 Multiplication-Sign PCR{sub V}) degraded dose conformity significantly due to a reduced scan velocity. In contrast, 4 Multiplication-Sign PCR{sub L} or more significantly and consistently improved dose distribution. PCR{sub V} showed interference effects, but in general also improved dose homogeneity with higher numbers of rescannings. Dose distributions with single PCR{sub L}/PCR{sub V} with a sweep direction perpendicular to motion direction showed large hot/cold spots; however, this effect vanished with higher numbers of rescannings for both methods. Similar observations were obtained for the other dose metrics, such as target motion (SI/AP), amplitude (6-22 mm peak-to-peak) and respiratory period (3.0-5.0 s). For four or more rescannings, both methods showed significantly better results, albeit that volumetric PCR was more affected by interference effects, which lead to severe degradation of a few dose distributions. The clinical example showed the same tendencies as the phantom study. Dose assessment metrics (D95, Dmax/Dmin, homogeneity index) were improved with an increasing number of PCR{sub L}/PCR{sub V}, but with PCR{sub L} being more robust. Conclusions: PCR{sub L} requires a longer treatment time than PCR{sub V} for high numbers of rescannings in the NIRS scanning system but is more robust. Although four or more rescans provided good dose homogeneity and conformity, the authors prefer to use more rescannings for clinical cases to further minimize dose degradation effects due to organ motion.
Four-Dimensional Patient Dose Reconstruction for Scanned Ion Beam Therapy of Moving Liver Tumors
Richter, Daniel; Saito, Nami; Chaudhri, Naved; Härtig, Martin; Ellerbrock, Malte; Jäkel, Oliver; Combs, Stephanie E.; Habermehl, Daniel; Herfarth, Klaus; Durante, Marco; Bert, Christoph
2014-05-01
Purpose: Estimation of the actual delivered 4-dimensional (4D) dose in treatments of patients with mobile hepatocellular cancer with scanned carbon ion beam therapy. Methods and Materials: Six patients were treated with 4 fractions to a total relative biological effectiveness (RBE)–weighted dose of 40 Gy (RBE) using a single field. Respiratory motion was addressed by dedicated margins and abdominal compression (5 patients) or gating (1 patient). 4D treatment dose reconstructions based on the treatment records and the measured motion monitoring data were performed for the single-fraction dose and a total of 17 fractions. To assess the impact of uncertainties in the temporal correlation between motion trajectory and beam delivery sequence, 3 dose distributions for varying temporal correlation were calculated per fraction. For 3 patients, the total treatment dose was formed from the fractional distributions using all possible combinations. Clinical target volume (CTV) coverage was analyzed using the volumes receiving at least 95% (V{sub 95}) and 107% (V{sub 107}) of the planned doses. Results: 4D dose reconstruction based on daily measured data is possible in a clinical setting. V{sub 95} and V{sub 107} values for the single fractions ranged between 72% and 100%, and 0% and 32%, respectively. The estimated total treatment dose to the CTV exhibited improved and more robust dose coverage (mean V{sub 95} > 87%, SD < 3%) and overdose (mean V{sub 107} < 4%, SD < 3%) with respect to the single-fraction dose for all analyzed patients. Conclusions: A considerable impact of interplay effects on the single-fraction CTV dose was found for most of the analyzed patients. However, due to the fractionated treatment, dose heterogeneities were substantially reduced for the total treatment dose. 4D treatment dose reconstruction for scanned ion beam therapy is technically feasible and may evolve into a valuable tool for dose assessment.
Yang, Juan; Cai, Jing; Wang, Hongjun; Chang, Zheng; Czito, Brian G.; Bashir, Mustafa R.; Yin, Fang-Fang
2014-03-15
Purpose: To evaluate the feasibility of a retrospective binning technique for 4-dimensional magnetic resonance imaging (4D-MRI) using body area (BA) as a respiratory surrogate. Methods and Materials: Seven patients with hepatocellular carcinoma (4 of 7) or liver metastases (3 of 7) were enrolled in an institutional review board-approved prospective study. All patients were simulated with both computed tomography (CT) and MRI to acquire 3-dimensinal and 4D images for treatment planning. Multiple-slice multiple-phase cine-MR images were acquired in the axial plane for 4D-MRI reconstruction. Image acquisition time per slice was set to 10-15 seconds. Single-slice 2-dimensinal cine-MR images were also acquired across the center of the tumor in orthogonal planes. Tumor motion trajectories from 4D-MRI, cine-MRI, and 4D-CT were analyzed in the superior–inferior (SI), anterior–posterior (AP), and medial–lateral (ML) directions, respectively. Their correlation coefficients (CC) and differences in tumor motion amplitude were determined. Tumor-to-liver contrast-to-noise ratio (CNR) was measured and compared between 4D-CT, 4D-MRI, and conventional T2-weighted fast spin echo MRI. Results: The means (±standard deviations) of CC comparing 4D-MRI with cine-MRI were 0.97 ± 0.03, 0.97 ± 0.02, and 0.99 ± 0.04 in SI, AP, and ML directions, respectively. The mean differences were 0.61 ± 0.17 mm, 0.32 ± 0.17 mm, and 0.14 ± 0.06 mm in SI, AP, and ML directions, respectively. The means of CC comparing 4D-MRI and 4D-CT were 0.95 ± 0.02, 0.94 ± 0.02, and 0.96 ± 0.02 in SI, AP, and ML directions, respectively. The mean differences were 0.74 ± 0.02 mm, 0.33 ± 0.13 mm, and 0.18 ± 0.07 mm in SI, AP, and ML directions, respectively. The mean tumor-to-tissue CNRs were 2.94 ± 1.51, 19.44 ± 14.63, and 39.47 ± 20.81 in 4D-CT, 4D-MRI, and T2-weighted MRI, respectively. Conclusions: The preliminary evaluation of our 4D-MRI technique results in oncologic patients demonstrates its potential usefulness to accurately measure tumor respiratory motion with improved tumor CNR compared with 4D-CT.
Development of the L-1011 four-dimensional flight management system
NASA Technical Reports Server (NTRS)
Lee, H. P.; Leffler, M. F.
1984-01-01
The development of 4-D guidance and control algorithms for the L-1011 Flight Management System is described. Four-D Flight Management is a concept by which an aircraft's flight is optimized along the 3-D path within the constraints of today's ATC environment, while its arrival time is controlled to fit into the air traffic flow without incurring or causing delays. The methods developed herein were designed to be compatible with the time-based en route metering techniques that were recently developed by the Dallas/Fort Worth and Denver Air Route Traffic Control Centers. The ensuing development of the 4-D guidance algorithms, the necessary control laws and the operational procedures are discussed. Results of computer simulation evaluation of the guidance algorithms and control laws are presented, along with a description of the software development procedures utilized.
Four-dimensional Monte Carlo investigation of organ motion in radiotherapy for lung cancer
NASA Astrophysics Data System (ADS)
Heath, Emily
A limitation of current dose calculation algorithms employed in radiotherapy treatment planning is the assumption that the patient's anatomy is static throughout the imaging, planning and delivery. 4D dose calculation methods employ non-linear image registration to determine the cumulative dose received in a deforming anatomy. In this work, we developed a 4D Monte Carlo dose calculation code, designated defDOSXYZ, which determines the dose received in a deforming voxel grid. Voxel deformations were determined from deformation vectors resulting from non-linear image registration between images of the reference and target states. The ANIMAL non-linear image registration algorithm was implemented for registration of thoracic 4D CT images. Modifications were performed to ANIMAL to minimize deformation vector discontinuities. A method for correcting artifacts in 4D CT images was developed which uses non-linear image registration to interpolate voxel intensities from temporally adjacent artifact-free images. Dose calculations in deforming phantoms and 4D CT patient data using defDOSXYZ were compared to conventional center-of-mass (COM) and trilinear (TL) dose remapping methods. defDOSXYZ calculations were determined to be accurate to within 1% by comparison with DOSXYZ calculations and internal consistency checks. Conventional dose remapping methods were found to underestimate the dose by 29% and 8%, on average, when remapping dose from Exhale to Inhale within simple deforming phantoms with voxel sizes of 1 cm and 0.5 cm, respectively. These discrepancies were reduced to 0.2% for voxel sizes of 0.25 cm and smaller, however dose errors of 20-30% still existed in regions of steep dose gradients. The accuracy of non-linear image registration between inhale and exhale images for 5 lung patients was found to be within 2 mm which was deemed acceptable for clinical dose calculations. Temporal interpolation using ANIMAL was demonstrated to improve image quality in 4D data sets containing motion artifacts. Comparison of dose remapping from Inhale to Exhale in an anatomical breathing phantom revealed that interpolation methods underestimate the dose in the penumbra and near the surface. defDOSXYZ calculations were also compared with two dose remapping methods in 4D CT patient data. Systematic offsets between the dose calculation methods were noted which were attributed to inconsistent handling of voxel mass conservation in the image registration and dose calculations. A mass-consistent comparison of defDOSXYZ calculations and remapping calculations for clinically relevant planning scenarios and dose grid sizes revealed discrepancies in regions of steep gradients which was consistent with the phantom studies. No clinically significant differences in planning volume doses were noted between all three dose calculation methods, although conventional dose remapping failed to predict certain details of the cumulative dose distribution which may be important for 4D conformal treatment planning.
Four-Dimensional Characterization of Paper Web at the Wet End
Goddard, JS
2001-02-28
This report presents a detailed description of a vision system whose purpose is to detect and to localize the nonuniformities that appear on the paper slurry (wood fiber and water mixture) at the wet end of a paper machine. Specifically, the system is capable of monitoring the paper slurry upon its exit from the headbox and alerting the operators of any event (e.g., streaks) that disrupts the otherwise homogeneous background. Such events are thought to affect crucial product properties such as formation, which if poor, results in thick and thin spots on the sheet and impacts its strength and printability. This report describes the vision system in terms of its hardware modules, as well as the image processing algorithms that it utilizes to perform its function. Basically, the system acquires both intensity and topographic information from the scene and uses texture-based features for the detection, and facet-based descriptors for the localization of the nonuniformities. In addition to being tested in a laboratory environment, a prototype of this system was constructed and deployed to a paper mill, where its performance was evaluated under realistic conditions. Installed on a fourdrinier paper machine, running at 480 m/min and producing linerboard material, the vision system was able to monitor an approximately 1-meter-wide area and to successfully detect and localize slurry streaks.
Four-dimensional in vivo X-ray microscopy with projection-guided gating.
Mokso, Rajmund; Schwyn, Daniel A; Walker, Simon M; Doube, Michael; Wicklein, Martina; Müller, Tonya; Stampanoni, Marco; Taylor, Graham K; Krapp, Holger G
2015-01-01
Visualizing fast micrometer scale internal movements of small animals is a key challenge for functional anatomy, physiology and biomechanics. We combine phase contrast tomographic microscopy (down to 3.3 μm voxel size) with retrospective, projection-based gating (in the order of hundreds of microseconds) to improve the spatiotemporal resolution by an order of magnitude over previous studies. We demonstrate our method by visualizing 20 three-dimensional snapshots through the 150 Hz oscillations of the blowfly flight motor. PMID:25762080
Four-dimensional inversion of resistivity monitoring data through Lp norm minimizations
NASA Astrophysics Data System (ADS)
Kim, Jung-Ho; Supper, Robert; Tsourlos, Panagiotis; Yi, Myeong-Jong
2013-12-01
A new 4-D inversion algorithm is developed so that any data misfits and model roughness in the space and time domains can be selectively minimized, in terms of either the L1 norm or the L2 norm. This study is motivated by the experience that a 4-D inversion adopting full L2 norm minimization may sometimes result in a model that is too smoothly varying with time. It is further encouraged by the realization that a particular criterion of either L1 or L2 norm cannot be universally optimal for accurately reconstructing the subsurface condition. In addition, we try to overcome difficulties of jointly choosing two optimal regularization parameters in space and time domains. To achieve this, we devise automatic determination methods, not only of the Lagrangian multipliers for the space-domain smoothness constraint, but also of the regularization parameter for penalizing the model roughness along the time axis. Both kinds of regularization parameters are actively updated at each iteration, according to variations in data misfit and model roughness. We conducted inversion experiments using synthetic and field monitoring data to test the proposed algorithms, and further to compare the performance of L1 and L2 norm minimizations. Both the synthetic and field data experiments demonstrated that the proposed automatic determination method produced ground changes that were more similar to the true changes than those of approaches using pre-determined parameter values. Inversion experiments showed that L1 norm minimization of the time-domain roughness could reduce the problem of overly smooth model changes when the subsurface changes are locally confined, but that the L2 norm approach would be more reasonable when the changes are expected to be widespread.
Four-dimensional modeling of recent vertical movements in the area of the southern california uplift
Vanicek, P.; Elliott, M.R.; Castle, R.O.
1979-01-01
This paper describes an analytical technique that utilizes scattered geodetic relevelings and tide-gauge records to portray Recent vertical crustal movements that may have been characterized by spasmodic changes in velocity. The technique is based on the fitting of a time-varying algebraic surface of prescribed degree to the geodetic data treated as tilt elements and to tide-gauge readings treated as point movements. Desired variations in time can be selected as any combination of powers of vertical movement velocity and episodic events. The state of the modeled vertical displacement can be shown for any number of dates for visual display. Statistical confidence limits of the modeled displacements, derived from the density of measurements in both space and time, line length, and accuracy of input data, are also provided. The capabilities of the technique are demonstrated on selected data from the region of the southern California uplift. ?? 1979.
Airborne Four-Dimensional Flight Management in a Time-based Air Traffic Control Environment
NASA Technical Reports Server (NTRS)
Williams, David H.; Green, Steven M.
1991-01-01
Advanced Air Traffic Control (ATC) systems are being developed which contain time-based (4D) trajectory predictions of aircraft. Airborne flight management systems (FMS) exist or are being developed with similar 4D trajectory generation capabilities. Differences between the ATC generated profiles and those generated by the airborne 4D FMS may introduce system problems. A simulation experiment was conducted to explore integration of a 4D equipped aircraft into a 4D ATC system. The NASA Langley Transport Systems Research Vehicle cockpit simulator was linked in real time to the NASA Ames Descent Advisor ATC simulation for this effort. Candidate procedures for handling 4D equipped aircraft were devised and traffic scenarios established which required time delays absorbed through speed control alone or in combination with path stretching. Dissimilarities in 4D speed strategies between airborne and ATC generated trajectories were tested in these scenarios. The 4D procedures and FMS operation were well received by airline pilot test subjects, who achieved an arrival accuracy at the metering fix of 2.9 seconds standard deviation time error. The amount and nature of the information transmitted during a time clearance were found to be somewhat of a problem using the voice radio communication channel. Dissimilarities between airborne and ATC-generated speed strategies were found to be a problem when the traffic remained on established routes. It was more efficient for 4D equipped aircraft to fly trajectories with similar, though less fuel efficient, speeds which conform to the ATC strategy. Heavy traffic conditions, where time delays forced off-route path stretching, were found to produce a potential operational benefit of the airborne 4D FMS.
Wang, Zhaohui; Witte, Russell S.
2015-01-01
Ultrasound current source density imaging (UCSDI), which has application to the heart and brain, exploits the acoustoelectric (AE) effect and Ohm's law to detect and map an electrical current distribution. In this study, we describe 4-D UCSDI simulations of a dipole field for comparison and validation with bench-top experiments. The simulations consider the properties of the ultrasound pulse as it passes through a conductive medium, the electric field of the injected dipole, and the lead field of the detectors. In the simulation, the lead fields of detectors and electric field of the dipole were calculated by the finite element (FE) method, and the convolution and correlation in the computation of the detected AE voltage signal were accelerated using 3-D fast Fourier transforms. In the bench-top experiment, an electric dipole was produced in a bath of 0.9% NaCl solution containing two electrodes, which injected an ac pulse (200 Hz, 3 cycles) ranging from 0 to 140 mA. Stimulating and recording electrodes were placed in a custom electrode chamber made on a rapid prototype printer. Each electrode could be positioned anywhere on an x-y grid (5 mm spacing) and individually adjusted in the depth direction for precise control of the geometry of the current sources and detecting electrodes. A 1-MHz ultrasound beam was pulsed and focused through a plastic film to modulate the current distribution inside the saline-filled tank. AE signals were simultaneously detected at a sampling frequency of 15 MHz on multiple recording electrodes. A single recording electrode is sufficient to form volume images of the current flow and electric potentials. The AE potential is sensitive to the distance from the dipole, but is less sensitive to the angle between the detector and the dipole. Multi-channel UCSDI potentially improves 4-D mapping of bioelectric sources in the body at high spatial resolution, which is especially important for diagnosing and guiding treatment of cardiac and neurologic disorders, including arrhythmia and epilepsy. PMID:24569247
The generalized Erlangen program and setting a geometry for four- dimensional conformal fields
Ne`eman, Y. |; Hehl, F.W.; Mielke, E.W.
1993-10-22
This is the text of a talk at the International Symposium on ``Mathematical Physics towards the XXI Century`` held in March 1993 at Beersheva, Israel. In the first part we attempt to summarize XXth Century Physics, in the light of Kelvin`s 1900 speech ``Dark Clouds over XIXth Century Physics.`` Contrary to what is usually said, Kelvin predicted that the ``clouds`` (relativity and quantum mechanics) would revolutionize physics and that one hundred years might be needed to harmonize them with classical physics. Quantum Gravity can be considered as a leftover from Kelvin`s program -- so are the problems with the interpretation of quantum mechanics. At the end of the XXth Century, the Standard Model is the new panoramic synthesis, drawn in gauge-geometric lines -- realizing the Erlangen program beyond F. Klein`s expectations. The hierarchy problem and the smallness of the cosmological constant are our ``clouds``, generations and the Higgs sector are to us what radioactivity was in 1900. In the second part we describe Metric-Affine spacetimes. We construct the Noether machinery and provide expressions for the conserved energy and hypermomentum. Superimposing conformal invariance over the affine structure induces the Virasoro-like infinite constraining algebra of diffeomorphisms, applied with constant parameters and opening the possibility of a 4DCFT, similar to 2DCFT.
Ultrafast dynamics. Four-dimensional imaging of carrier interface dynamics in p-n junctions.
Najafi, Ebrahim; Scarborough, Timothy D; Tang, Jau; Zewail, Ahmed
2015-01-01
The dynamics of charge transfer at interfaces are fundamental to the understanding of many processes, including light conversion to chemical energy. Here, we report imaging of charge carrier excitation, transport, and recombination in a silicon p-n junction, where the interface is well defined on the nanoscale. The recorded images elucidate the spatiotemporal behavior of carrier density after optical excitation. We show that carrier separation in the p-n junction extends far beyond the depletion layer, contrary to the expected results from the widely accepted drift-diffusion model, and that localization of carrier density across the junction takes place for up to tens of nanoseconds, depending on the laser fluence. The observations reveal a ballistic-type motion, and we provide a model that accounts for the spatiotemporal density localization across the junction. PMID:25574020
Effective Doses in Four-Dimensional Computed Tomography for Lung Radiotherapy Planning
Mori, Shinichiro Ko, Susumu; Ishii, Takayoshi; Nishizawa, Kanae
2009-04-01
The recent broad adoption of 4-D computed tomography (4DCT) scanning in radiotherapy has allowed the accurate determination of the target volume of tumors by minimizing image degradation caused by respiratory motion. Although the radiation exposure of the treatment beam is significantly greater than that of CT scans used for treatment planning, it is important to recognize and optimize the radiation exposure in 4DCT from the radiological protection point of view. Here, radiation exposure in 4DCT was measured with a 16 multidetector CT. Organ doses were measured using thermoluminescence radiation dosimeter chips inserted at respective anatomical sites of an anthropomorphic phantom. Results were compared with those with the helical CT scan mode. The effective dose measured for 4DCT was 24.7 mSv, approximately four times higher than that for helical CT. However, the increase in treatment accuracy afforded by 4DCT means its use in radiotherapy is inevitable. The patient exposure in the 4DCT could be of value by clarifying the advantage of the treatment planning using 4DCT.
Comparisons among a new soil index and other two- and four-dimensional vegetation indices
NASA Technical Reports Server (NTRS)
Wiegand, C. L.; Richardson, A. J. (Principal Investigator)
1982-01-01
The 2-D difference vegetation index (DVI) and perpendicular vegetation index (PVI), and the 4-D green vegetation index (GVI) are compared in LANDSAT MSS data from grain sorghum (Sorghum bicolor, L. Moench) fields for the years 1973 to 1977. PVI and DVI were more closely related to LAI than was GVI. A new 2-D soil line index (SLI), the vector distance from the soil line origin to the point of intersection of PVI with the soil line, is defined and compared with the 4-D soil brightness index, SBI. SLI (based on MSS and MSS7) and SL16 (based on MSS 5 and MSS 6) were smaller in magnitude than SBI but contained similar information about the soil background. These findings indicate that vegetation and soil indices calculated from the single visible and reflective infrared band sensor systems, such as the AVHRR of the TIROS-N polar orbiting series of satellites, will be meaningful for synoptic monitoring of renewable vegetation.
Comparisons among a new soil index and other two- and four-dimensional vegetation indices
NASA Technical Reports Server (NTRS)
Wiegand, C. L.; Richardson, A. J.
1982-01-01
The 2-D difference vegetation index (DVI) and perpendicular vegetation index (PVI), and the 4-D green vegetation index (GVI) are compared in Landsat MSS data from grain sorghum (Sorghum bicolor, L. Moench) fields for the years 1973 to 1977. PVI and DVI were more closely related to LAI than was GVI. A new 2-D soil line index (SLI), the vector distance from the soil line origin to the point of intersection of PVI with the soil line, is defined and compared with the 4-D soil brightness index, SBI. SLI (based on MSS and MSS7) and SL16 (based on MSS5 and MSS6) were smaller in magnitude than SBI but contained similar information about the soil background. These findings indicate that vegetation and soil indices calculated from the single visible and reflective infrared band sensor systems, such as the AVHRR of the TIROS-N polar orbiting series of satellites, will be meaningful for synoptic monitoring of renewable vegetation. Previously announced in STAR as N83-14567
Four-dimensional in vivo X-ray microscopy with projection-guided gating
NASA Astrophysics Data System (ADS)
Mokso, Rajmund; Schwyn, Daniel A.; Walker, Simon M.; Doube, Michael; Wicklein, Martina; Müller, Tonya; Stampanoni, Marco; Taylor, Graham K.; Krapp, Holger G.
2015-03-01
Visualizing fast micrometer scale internal movements of small animals is a key challenge for functional anatomy, physiology and biomechanics. We combine phase contrast tomographic microscopy (down to 3.3 μm voxel size) with retrospective, projection-based gating (in the order of hundreds of microseconds) to improve the spatiotemporal resolution by an order of magnitude over previous studies. We demonstrate our method by visualizing 20 three-dimensional snapshots through the 150 Hz oscillations of the blowfly flight motor.
Four-dimensional investigation of the 2nd order volume autocorrelation technique
NASA Astrophysics Data System (ADS)
Faucher, O.; Tzallas, P.; Benis, E. P.; Kruse, J.; Peralta Conde, A.; Kalpouzos, C.; Charalambidis, D.
2009-10-01
The 2nd order volume autocorrelation technique, widely utilized in directly measuring ultra-short light pulses durations, is examined in detail via model calculations that include three-dimensional integration over a large ionization volume, temporal delay and spatial displacement of the two beams of the autocorrelator at the focus. The effects of the inherent displacement to the 2nd order autocorrelation technique are demonstrated for short and long pulses, elucidating the appropriate implementation of the technique in tight focusing conditions. Based on the above investigations, a high accuracy 2nd order volume autocorrelation measurement of the duration of the 5th harmonic of a 50 fs long laser pulse, including the measurement of the carrier wavelength oscillation, is presented.
[Motion-compensated compressed sensing four-dimensional cone-beam CT reconstruction].
Yang, Xuan; Zhang, Hua; He, Ji; Zeng, Dong; Zhang, Xin-Yu; Bian, Zhao-Ying; Zhang, Jing; Ma, Jian-Hua
2016-06-20
Restriction by hardware caused the very low projection number at a single phase for 4-dimensional cone beam (4D-CBCT) CT imaging, and reconstruction using conventional reconstruction algorithms is thus constrained by serious streak artifacts and noises. To address this problem, we propose an approach to reconstructing 4D-CBCT images with multi-phase projections based on the assumption that the image at one phase can be viewed as the motion-compensated image at another phase. Specifically, we formulated a cost function using multi-phase projections to construct the fidelity term and the TV regularization method. For fidelity term construction, the projection data of the current phase and those at other phases were jointly used by reformulating the imaging model. The Gradient-Projection-Barzilai-Line search (GPBL) method was used to optimize the complex cost function. Physical phantom and patient data results showed that the proposed approach could effectively reduce the noise and artifacts, and the introduction of additional temporal correlation did not introduce new artifacts or motion blur. PMID:27435778
Gunasekera, R.C.; Foulger, G.R.; Julian, B.R.
2003-01-01
Intensive geothermal exploitation at The Geysers geothermal area, California, induces myriads of small-magnitude earthquakes that are monitored by a dense, permanent, local seismometer network. Using this network, tomographic inversions were performed for the three-dimensional Vp and Vp/Vs structure of the reservoir for April 1991, February 1993, December 1994, October 1996, and August 1998. The extensive low-Vp/Vs anomaly that occupies the reservoir grew in strength from a maximum of 9% to a maximum of 13.4% during the 7-year study period. This is attributed to depletion of pore liquid water in the reservoir and replacement with steam. This decreases Vp by increasing compressibility, and increases Vs because of reduction in pore pressure and the drying of argillaceous minerals, e.g., illite, which increase the shear modulus. These effects serendipitously combine to lower Vp/Vs, resulting in a strong overall effect that provides a convenient tool for monitoring reservoir depletion. Variations in the Vp and Vs fields indicate that water depletion is the dominant process in the central part of the exploited reservoir, and pressure reduction and mineral drying in the northwest and southeast parts of the reservoir. The rate at which the Vp/Vs anomaly grew in strength in the period 1991-1998 suggests most of the original anomaly was caused by exploitation. Continuous monitoring of Vp, Vs, and Vp/Vs is an effective geothermal reservoir depletion monitoring tool and can potentially provide information about depletion in parts of the reservoir that have not been drilled.
NASA Astrophysics Data System (ADS)
Haggard, Hal; Han, Muxin; Kaminski, Wojciech; Riello, Aldo
2016-03-01
Prominent approaches to quantum gravity struggle when it comes to incorporating a positive cosmological constant in their models. Using quantization of a complex SL(2,C) Chern-Simons theory we include a cosmological constant, of either sign, into a model of quantum gravity.
Medical prosthetic applications of growth simulations in four-dimensional facial morphology
NASA Astrophysics Data System (ADS)
Sadler, Lewis L.; Chen, Xiaoming; Fyler, Ann
1991-04-01
Growth data on the developing human face has been collected by scientists in a number ofdifferent disciplines for nearly one hundred years. Most of the work in this area has been the result of attempts to understand and quantify the growth process or in attempting to establish population norms or baseline standards for use in syndromology. Anthropologists geneticists ophthalmologists orthodontists otorhinolaryngologists pediatric syndromologists plastic surgeons radiologists have all contributed to the literature on facial development1. While this literature for facial assessment is very complete but its use and value in prediction has not been exploited to-date. The preliminary work presented in this paper uses the available literature to predict growth and development ofthe nose. These predictions were used in fabricating a series ofnasal prostheses that will be used to establish facial cosmesis during the growth years. This case involves a six year old male who had undergone a total rhinectomy and septectomy required a nose prosthesis to cover a severe facial defect and to effect cosmesis. Based on laser scan data from casts ofthe patient''s pre-surgical nose a selected series ofanthropometric landmarks were identified and scaled. Growth algorithms provided new positions for control points that simulated growth of the nose over time. The resulting series of geometric models were initially fabricated using stereolithography and later modeled in a medical grade silastic. Growth predictions used to simulate the morphological remodelling of facia
Mottola, E.
1993-01-01
After first reviewing the issue of vacuum energy (the cosmological constant problem) in the Einstein theory, the covariant path integral for gravity in four dimensions is constructed. The problem of vacuum energy requires determining the correct ground state of the quantum theory of gravity, and as such is an infrared problem, arising prior to and independently of the physics of the Planck scale. It is addressed in these lectures by studying the infrared fixed point of the low energy effective action of the conformal factor generated by the quantum trace anomaly in four dimensions. The infrared fixed point of this effective theory describes a conformally invariant phase of gravity with a vanishing effective cosmological term.
Mottola, E.
1993-03-01
After first reviewing the issue of vacuum energy (the cosmological constant problem) in the Einstein theory, the covariant path integral for gravity in four dimensions is constructed. The problem of vacuum energy requires determining the correct ground state of the quantum theory of gravity, and as such is an infrared problem, arising prior to and independently of the physics of the Planck scale. It is addressed in these lectures by studying the infrared fixed point of the low energy effective action of the conformal factor generated by the quantum trace anomaly in four dimensions. The infrared fixed point of this effective theory describes a conformally invariant phase of gravity with a vanishing effective cosmological term.
NASA Astrophysics Data System (ADS)
Jenkins, Michael W.; Peterson, Lindsy; Gu, Shi; Gargesha, Madhusudhana; Wilson, David L.; Watanabe, Michiko; Rollins, Andrew M.
2010-11-01
Hemodynamics is thought to play a major role in heart development, yet tools to quantitatively assess hemodynamics in the embryo are sorely lacking. The especially challenging analysis of hemodynamics in the early embryo requires new technology. Small changes in blood flow could indicate when anomalies are initiated even before structural changes can be detected. Furthermore, small changes in the early embryo that affect blood flow could lead to profound abnormalities at later stages. We present a demonstration of 4-D Doppler optical coherence tomography (OCT) imaging of structure and flow, and present several new hemodynamic measurements on embryonic avian hearts at early stages prior to the formation of the four chambers. Using 4-D data, pulsed Doppler measurements could accurately be attained in the inflow and outflow of the heart tube. Also, by employing an en-face slice from the 4-D Doppler image set, measurements of stroke volume and cardiac output are obtained without the need to determine absolute velocity. Finally, an image plane orthogonal to the blood flow is used to determine shear stress by calculating the velocity gradient normal to the endocardium. Hemodynamic measurements will be crucial to identifying genetic and environmental factors that lead to congenital heart defects.
Flight investigation of a four-dimensional terminal area guidance system for STOL aircraft
NASA Technical Reports Server (NTRS)
Neuman, F.; Hardy, G. H.
1981-01-01
A series of flight tests and fast-time simulations were conducted, using the augmentor wing jet STOL research aircraft and the STOLAND 4D-RNAV system to add to the growing data base of 4D-RNAV system performance capabilities. To obtain statistically meaningful data a limited amount of flight data were supplemented by a statistically significant amount of data obtained from fast-time simulation. The results of these tests are reported. Included are comparisons of the 4D-RNAV estimated winds with actual winds encountered in flight, as well as data on along-track navigation and guidance errors, and time-of-arrival errors at the final approach waypoint. In addition, a slight improvement of the STOLAND 4D-RNAV system is proposed and demonstrated, using the fast-time simulation.
Some aspects of the problem in the four-dimensional quantum Hall effect
NASA Astrophysics Data System (ADS)
Chern, Chyh-Hong
The remarkable Landau level structure can be generalized to 4-sphere with SU(2) magnetic monopole at the center of the 4-sphere. The bulk states reveal the relativistic nature if we maximally enlarge the gauge symmetry to the one of this system, which is SO(5). When the monopole strength S is less than or equal to 2, they describe the helicity states of massless particles of spin. Moreover, the effective field theory of the lowest Landau level is formulated on CP3, which is the level manifold of the lowest Landau level. The single particle Lagrangian is the Berry's phase over CP3. Using the flux attachment transformation, the hydrodynamic description of this model can be written as a 6+1 dimensional U(1) Chem-Simons theory. Locally, the system can be regarded as three independent 2-dimensional quantum Hall planes. Because the choice of the independent planes is arbitrary up to a gauge transformation, the interchanging phase between membranes can be defined on CP3 by moving one membrane around the other on a 2DQHE plane. They are the elementary excitations of the system and may obey fractional statistics, if the system is fractionally filled.
Arthropod Distribution in a Tropical Rainforest: Tackling a Four Dimensional Puzzle.
Basset, Yves; Cizek, Lukas; Cuénoud, Philippe; Didham, Raphael K; Novotny, Vojtech; Ødegaard, Frode; Roslin, Tomas; Tishechkin, Alexey K; Schmidl, Jürgen; Winchester, Neville N; Roubik, David W; Aberlenc, Henri-Pierre; Bail, Johannes; Barrios, Héctor; Bridle, Jonathan R; Castaño-Meneses, Gabriela; Corbara, Bruno; Curletti, Gianfranco; Duarte da Rocha, Wesley; De Bakker, Domir; Delabie, Jacques H C; Dejean, Alain; Fagan, Laura L; Floren, Andreas; Kitching, Roger L; Medianero, Enrique; Gama de Oliveira, Evandro; Orivel, Jérôme; Pollet, Marc; Rapp, Mathieu; Ribeiro, Sérvio P; Roisin, Yves; Schmidt, Jesper B; Sørensen, Line; Lewinsohn, Thomas M; Leponce, Maurice
2015-01-01
Quantifying the spatio-temporal distribution of arthropods in tropical rainforests represents a first step towards scrutinizing the global distribution of biodiversity on Earth. To date most studies have focused on narrow taxonomic groups or lack a design that allows partitioning of the components of diversity. Here, we consider an exceptionally large dataset (113,952 individuals representing 5,858 species), obtained from the San Lorenzo forest in Panama, where the phylogenetic breadth of arthropod taxa was surveyed using 14 protocols targeting the soil, litter, understory, lower and upper canopy habitats, replicated across seasons in 2003 and 2004. This dataset is used to explore the relative influence of horizontal, vertical and seasonal drivers of arthropod distribution in this forest. We considered arthropod abundance, observed and estimated species richness, additive decomposition of species richness, multiplicative partitioning of species diversity, variation in species composition, species turnover and guild structure as components of diversity. At the scale of our study (2 km of distance, 40 m in height and 400 days), the effects related to the vertical and seasonal dimensions were most important. Most adult arthropods were collected from the soil/litter or the upper canopy and species richness was highest in the canopy. We compared the distribution of arthropods and trees within our study system. Effects related to the seasonal dimension were stronger for arthropods than for trees. We conclude that: (1) models of beta diversity developed for tropical trees are unlikely to be applicable to tropical arthropods; (2) it is imperative that estimates of global biodiversity derived from mass collecting of arthropods in tropical rainforests embrace the strong vertical and seasonal partitioning observed here; and (3) given the high species turnover observed between seasons, global climate change may have severe consequences for rainforest arthropods. PMID:26633187
Interactive access and management for four-dimensional environmental data sets using McIDAS
NASA Technical Reports Server (NTRS)
Hibbard, William L.; Tripoli, Gregory J.
1991-01-01
Significant accomplishments in the following areas are presented: (1) enhancements to the visualization of 5-D data sets (VIS-5D); (2) development of the visualization of global images (VIS-GI) application; (3) design of the Visualization for Algorithm Development (VIS-AD) System; and (4) numerical modeling applications. The focus of current research and future research plans is presented and the following topics are addressed: (1) further enhancements to VIS-5D; (2) generalization and enhancement of the VIS-GI application; (3) the implementation of the VIS-AD System; and (4) plans for modeling applications.
Interactive access and management for four-dimensional environmental data sets using McIDAS
NASA Technical Reports Server (NTRS)
Hibbard, William L.; Tripoli, Gregory J.
1993-01-01
Significant accomplishments in the past year are presented and include the following: (1) enhancements to VIS-5D; (2) Implementation of the VIS AD System; and (3) numerical modeling applications. Focus of current research and plans for next year in the following areas are briefly discussed: (1) continued development and application of the VIS-AD system; (2) further enhancements to VIS-5D; and (3) plans for modeling applications.
Stationary axisymmetric four dimensional space-time endowed with Einstein metric
Hasanuddin; Azwar, A.; Gunara, B. E.
2015-04-16
In this paper, we construct Ernst equation from vacuum Einstein field equation for both zero and non-zero cosmological constant. In particular, we consider the case where the space-time admits axisymmetric using Boyer-Lindquist coordinates. This is called Kerr-Einstein solution describing a spinning black hole. Finally, we give a short discussion about the dynamics of photons on Kerr-Einstein space-time.
Validation of four-dimensional ultrasound for targeting in minimally-invasive beating-heart surgery
NASA Astrophysics Data System (ADS)
Pace, Danielle F.; Wiles, Andrew D.; Moore, John; Wedlake, Chris; Gobbi, David G.; Peters, Terry M.
2009-02-01
Ultrasound is garnering significant interest as an imaging modality for surgical guidance, due to its affordability, real-time temporal resolution and ease of integration into the operating room. Minimally-invasive intracardiac surgery performed on the beating-heart prevents direct vision of the surgical target, and procedures such as mitral valve replacement and atrial septal defect closure would benefit from intraoperative ultrasound imaging. We propose that placing 4D ultrasound within an augmented reality environment, along with a patient-specific cardiac model and virtual representations of tracked surgical tools, will create a visually intuitive platform with sufficient image information to safely and accurately repair tissue within the beating heart. However, the quality of the imaging parameters, spatial calibration, temporal calibration and ECG-gating must be well characterized before any 4D ultrasound system can be used clinically to guide the treatment of moving structures. In this paper, we describe a comprehensive accuracy assessment framework that can be used to evaluate the performance of 4D ultrasound systems while imaging moving targets. We image a dynamic phantom that is comprised of a simple robot and a tracked phantom to which point-source, distance and spherical objects of known construction can be attached. We also follow our protocol to evaluate 4D ultrasound images generated in real-time by reconstructing ECG-gated 2D ultrasound images acquired from a tracked multiplanar transesophageal probe. Likewise, our evaluation framework allows any type of 4D ultrasound to be quantitatively assessed.
A Multiscale Four-Dimensional Data Assimilation System Applied in the Mexico City Valley
NASA Astrophysics Data System (ADS)
Parra, D.; Hernandez, F.; Gonzalez, J. I.; Ortiz, E.; Hoyos, L. F.
2007-05-01
Several modeling studies have shown that four-dimension data assimilation (FDDA) has the ability to improve the simulations of wind, temperature, moisture and mixed layer depth. These works concluded that modeling with FDDA can produce spatially consistent solutions without degrading important dynamical processes. Additionally, it is widely recognized that MM5 with FDDA can be used to develop realistic three-dimensional fields that are completely suited as inputs to air quality or diagnostic meteorological models. In this work, MM5 and FDDA were used to model the weather conditions in the Mexico City Metropolitan Area (MCMA). The surface information was obtained from "Red Automática de Monitoreo Atmosférico (RAMA)" data bases. Sounding data were obtained from "Servicio Meteorológico Nacional". Four simulation domains were used with spatial resolutions of 27, 9, 3, and 1 Km2 respectively. In this work, 15 surface weather stations and 30 sounding points were employed. With this technique, weather predictions have correlation levels higher than 80%. Additionally, these predictions were used as input of the photochemical model MCCM and an important influence on pollutants concentration and dispersion predictions was observed.
Wang, Zhaohui; Witte, Russell S
2014-03-01
Ultrasound current source density imaging (UCSDI), which has application to the heart and brain, exploits the acoustoelectric (AE) effect and Ohm's law to detect and map an electrical current distribution. In this study, we describe 4-D UCSDI simulations of a dipole field for comparison and validation with bench-top experiments. The simulations consider the properties of the ultrasound pulse as it passes through a conductive medium, the electric field of the injected dipole, and the lead field of the detectors. In the simulation, the lead fields of detectors and electric field of the dipole were calculated by the finite element (FE) method, and the convolution and correlation in the computation of the detected AE voltage signal were accelerated using 3-D fast Fourier transforms. In the bench-top experiment, an electric dipole was produced in a bath of 0.9% NaCl solution containing two electrodes, which injected an ac pulse (200 Hz, 3 cycles) ranging from 0 to 140 mA. Stimulating and recording electrodes were placed in a custom electrode chamber made on a rapid prototype printer. Each electrode could be positioned anywhere on an x-y grid (5 mm spacing) and individually adjusted in the depth direction for precise control of the geometry of the current sources and detecting electrodes. A 1-MHz ultrasound beam was pulsed and focused through a plastic film to modulate the current distribution inside the saline-filled tank. AE signals were simultaneously detected at a sampling frequency of 15 MHz on multiple recording electrodes. A single recording electrode is sufficient to form volume images of the current flow and electric potentials. The AE potential is sensitive to the distance from the dipole, but is less sensitive to the angle between the detector and the dipole. Multi-channel UCSDI potentially improves 4-D mapping of bioelectric sources in the body at high spatial resolution, which is especially important for diagnosing and guiding treatment of cardiac and neurologic disorders, including arrhythmia and epilepsy. PMID:24569247
NASA Astrophysics Data System (ADS)
Troch, Peter A.; Niu, Guo-Yue; Gevaert, Anouk; Teuling, Adriaan; Uijlenhoet, Remko; Pasetto, Damiano; Paniconi, Claudio; Putti, Mario
2014-05-01
The Landscape Evolution Observatory (LEO) at Biosphere 2-The University of Arizona consists of three identical, sloping, 333 m2 convergent landscapes inside a 5,000 m2 environmentally controlled facility. These engineered landscapes contain 1-meter depth of basaltic tephra, ground to homogenous loamy sand. Each landscape contains a spatially dense sensor and sampler network capable of resolving meter-scale lateral heterogeneity and sub-meter scale vertical heterogeneity in moisture, energy and carbon states and fluxes. The density of sensors and frequency at which they can be polled allows for data collection at spatial and temporal scales that are impossible in natural field settings. Each ~600 metric ton landscape has load cells embedded into the structure to measure changes in total system mass with 0.05% full-scale repeatability (equivalent to less than 1 cm of precipitation). This facilitates the real time accounting of hydrological partitioning at the hillslope scale. Each hillslope is equipped with an engineered rain system capable of raining at rates between 3 and 45 mm/hr in a range of spatial patterns. We observed the spatial and temporal evolution of the soil moisture content at 496 5-TM Decagon sensors distributed over 5 different depths during a low-intensity long-duration rainfall experiment in February 2013. This presentation will focus on our modeling efforts to reveal subsurface hydraulic heterogeneity required to explain observed rainfall-runoff dynamics at the hillslope scale.
Management and display of four-dimensional environmental data sets using McIDAS
NASA Technical Reports Server (NTRS)
Hibbard, William L.; Santek, David; Suomi, Verner E.
1990-01-01
Over the past four years, great strides have been made in the areas of data management and display of 4-D meteorological data sets. A survey was conducted of available and planned 4-D meteorological data sources. The data types were evaluated for their impact on the data management and display system. The requirements were analyzed for data base management generated by the 4-D data display system. The suitability of the existing data base management procedures and file structure were evaluated in light of the new requirements. Where needed, new data base management tools and file procedures were designed and implemented. The quality of the basic 4-D data sets was assured. The interpolation and extrapolation techniques of the 4-D data were investigated. The 4-D data from various sources were combined to make a uniform and consistent data set for display purposes. Data display software was designed to create abstract line graphic 3-D displays. Realistic shaded 3-D displays were created. Animation routines for these displays were developed in order to produce a dynamic 4-D presentation. A prototype dynamic color stereo workstation was implemented. A computer functional design specification was produced based on interactive studies and user feedback.
Wilson loop calculations in four-dimensional lattice gauge theory on the CDC cyber 205
NASA Astrophysics Data System (ADS)
Barkai, D.; Creutz, M.; Moriarty, K. J. M.
1983-07-01
Pure SU(4) gauge theory is simulated by Monte Carlo methods on an 8 4 lattice. The method of Metropolis et al. is used to equilibriate the space-time lattice. All Wilson loops up to size 4×4 are calculated. Because of memory requirements we work on the 2 Mword CDC CYBER 205 at Colorado State University and take full advantage of the parallel processing capabilities of this vector machine.
Extension of four-dimensional atmospheric models. [and cloud cover data bank
NASA Technical Reports Server (NTRS)
Fowler, M. G.; Lisa, A. S.; Tung, S. L.
1975-01-01
The cloud data bank, the 4-D atmospheric model, and a set of computer programs designed to simulate meteorological conditions for any location above the earth are described in turns of space vehicle design and simulation of vehicle reentry trajectories. Topics discussed include: the relationship between satellite and surface observed cloud cover using LANDSAT 1 photographs and including the effects of cloud shadows; extension of the 4-D model to the altitude of 52 km; and addition of the u and v wind components to the 4-D model of means and variances at 1 km levels from the surface to 25 km. Results of the cloud cover analysis are presented along with the stratospheric model and the tropospheric wind profiles.
On the localisation of four-dimensional brane-world black holes: II. The general case
NASA Astrophysics Data System (ADS)
Kanti, P.; Pappas, N.; Pappas, T.
2016-01-01
We perform a comprehensive analysis of a number of scalar field theories in an attempt to find analytically five-dimensional, localised-on-the-brane, black-hole solutions. Extending a previous analysis, we assume a generalised Vaidya ansatz for the five-dimensional metric tensor that allows for a time-dependent, non-trivial profile of the mass function in terms of the bulk coordinate and a deviation from the over-restricting Schwarzschild-type solution on the brane. In order to support such a solution, we study a variety of theories including single or multiple scalar fields, with canonical or non-canonical kinetic terms, minimally or non-minimally coupled to gravity. We demonstrate that for such a metric ansatz and for a carefully chosen energy-momentum tensor which is non-isotropic in five dimensions, solutions that have the form of a Schwarzschild-(anti)de Sitter or Reissner-Nordstrom type of solution do emerge. However, the resulting profile of the mass function along the bulk coordinate, when allowed, is not the correct one for eliminating bulk singularities.
Geoarchaeology, the four dimensional (4D) fluvial matrix and climatic causality
NASA Astrophysics Data System (ADS)
Brown, A. G.
2008-10-01
Geoarchaeology is the application of geological and geomorphological techniques to archaeology and the study of the interactions of hominins with the natural environment at a variety of temporal and spatial scales. Geoarchaeology in the UK over the last twenty years has flourished largely because it has gone beyond technological and scientific applications. Over the same period our ability to reconstruct the 3-dimensional stratigraphy of fluvial deposits and the matrix of fluvial sites has increased dramatically because of a number of technological advances. These have included the use of LiDAR (laser imaging) and radar to produce high-resolution digital surface models, the use of geophysics, particularly ground penetrating radar and electrical resistivity, to produce sediment depth models, and the use of GIS and data visualisation techniques to manipulate and display the data. These techniques along with more systematic and detailed sedimentological recording of exposed sections have allowed the construction of more precise 3-dimensional (volumetric) models of the matrix of artefacts within fluvial deposits. Additionally a revolution in dating techniques, particularly direct sediment dating by luminescence methods, has enabled the creation of 4-dimensional models of the creation and preservation of these sites. These 4-dimensional models have the ability to provide far more information about the processes of site creation, preservation and even destruction, and also allow the integration of these processes with independent data sources concerning cultural evolution and climatic change. All improvements in the precision of dating fluvial deposits have archaeological importance in our need to translate events from a sequential or geological timeframe to human timescales. This allows geoarchaeology to make a more direct contribution to cultural history through the recognition of agency at the individual or group level. This data can then form a component of biocomplexity or agent-based modelling which is becoming increasingly used in the natural sciences, particularly ecology and geomorphology and which can be used to test scenarios including the impact on, and response of, hominins to abrupt or catastrophic environmental change. Whilst catastrophic events clearly represent the atypical they can be illuminating in revealing cognitive processes resulting in abandonment, coping, mitigation and innovation. These points are exemplified using two in-depth case studies: one from the Holocene geoarchaeological record of the River Trent in Central England and the other from the Palaeolithic record from rivers in South West Britain. In the former the interaction between climate change and human activity is illustrated at the year to century timescale whilst in the other the timescale is millennial. These case studies have deliberately been chosen to be as different as possible in temporal and spatial scale with the aim of examining the applicability of methodological and theoretical aspects of geoarchaeology. Lastly the paper considers the problem of scale in geoarchaeology and concludes it is process-dependency, which ultimately affects the questions we can ask, and that questions of human response to climate change are fundamentally a product of materiality and cognitive processes. This demands an in-depth contextual approach to such questions rather than database-driven assertions of causality.
This paper addresses the need to increase the temporal and spatial resolution of meteorological data currently used in air quality simulation models, AQSMs. ransport and diffusion parameters including mixing heights and stability used in regulatory air quality dispersion models a...
Four-dimensional ultrasound current source density imaging of a dipole field
NASA Astrophysics Data System (ADS)
Wang, Z. H.; Olafsson, R.; Ingram, P.; Li, Q.; Qin, Y.; Witte, R. S.
2011-09-01
Ultrasound current source density imaging (UCSDI) potentially transforms conventional electrical mapping of excitable organs, such as the brain and heart. For this study, we demonstrate volume imaging of a time-varying current field by scanning a focused ultrasound beam and detecting the acoustoelectric (AE) interaction signal. A pair of electrodes produced an alternating current distribution in a special imaging chamber filled with a 0.9% NaCl solution. A pulsed 1 MHz ultrasound beam was scanned near the source and sink, while the AE signal was detected on remote recording electrodes, resulting in time-lapsed volume movies of the alternating current distribution.
Discrete optimal control approach to a four-dimensional guidance problem near terminal areas
NASA Technical Reports Server (NTRS)
Nagarajan, N.
1974-01-01
Description of a computer-oriented technique to generate the necessary control inputs to guide an aircraft in a given time from a given initial state to a prescribed final state subject to the constraints on airspeed, acceleration, and pitch and bank angles of the aircraft. A discrete-time mathematical model requiring five state variables and three control variables is obtained, assuming steady wind and zero sideslip. The guidance problem is posed as a discrete nonlinear optimal control problem with a cost functional of Bolza form. A solution technique for the control problem is investigated, and numerical examples are presented. It is believed that this approach should prove to be useful in automated air traffic control schemes near large terminal areas.
Assimilation of Satellite Altimeter Data With a Four Dimensional Model of the Japan Sea
NASA Technical Reports Server (NTRS)
Hirose, Naoki; Ichiro, Fukumori; Jong-Hwan, Yoon
1999-01-01
A data assimilation is carried out to detect the variability of the Japan Sea circulation in the range from a few days to several years and from eddy to basin scale. The model applied in this study is the same 1/6 degree GFDL MOM1 as Kim and Yoon (1999) but is driven by ECMWF daily wind stress, heat and fresh water fluxes. The satellite altimeter data of TOPEX/POSEIDON, ERS-1 (phase C and G) and -2 are assimilated by an approximate Kalman filter (Fukumori and M.Rizzoli, 1995). The approximation is made by seeking an asymptotic steady error covariance matrix (Fukumori et al., 1993) and by introducing a coarser grid model for the innovation (data-model misfit). The coarse grid model is defined on 1/2 degree horizontal resolution and consists of the barotropic stream function, first baroclinic displacement and velocity amplitudes. The assimilated estimates explain about 6cm sea level variability of the data (approximately 12cm in the southern part), which is much larger than the previous reduced-gravity model and TOPEX/POSEIDON altimeter data assimilation (Hirose et al., 1999). The impacts of the T/P and ERS data on the filtered estimates are comparable. The result also shows high correlation to subsurface water temperatures measured by CTD. Many of the mesoscale eddies/disturbances travel east-northeastward with the advection speed of 1-3cm/s though most of them generated in the western region can not pass over the Oki Spur. The quasi-biennial variability found by Hirose and Ostrovskii (1999) did not show clear propagation pattern. The shallow Oki Spur may work as a "western boundary" to this signal. This is more plausible estimation than by the R-G model which has no bottom topography.
A Four Dimensional Spatio-Temporal Analysis of an Agricultural Dataset
Donald, Margaret R.; Mengersen, Kerrie L.; Young, Rick R.
2015-01-01
While a variety of statistical models now exist for the spatio-temporal analysis of two-dimensional (surface) data collected over time, there are few published examples of analogous models for the spatial analysis of data taken over four dimensions: latitude, longitude, height or depth, and time. When taking account of the autocorrelation of data within and between dimensions, the notion of closeness often differs for each of the dimensions. Here, we consider a number of approaches to the analysis of such a dataset, which arises from an agricultural experiment exploring the impact of different cropping systems on soil moisture. The proposed models vary in their representation of the spatial correlation in the data, the assumed temporal pattern and choice of conditional autoregressive (CAR) and other priors. In terms of the substantive question, we find that response cropping is generally more effective than long fallow cropping in reducing soil moisture at the depths considered (100 cm to 220 cm). Thus, if we wish to reduce the possibility of deep drainage and increased groundwater salinity, the recommended cropping system is response cropping. PMID:26513746
NASA Technical Reports Server (NTRS)
Kindle, J. C.; Thompson, J. D.; Hurlburt, H. E.
1984-01-01
Numerical experiments using simulated altimeter data were conducted in order to examine the assimilation of altimeter-derived sea surface heights into numerical ocean circulation models. A reduced-gravity, primitive equation circulation model of the Gulf of Mexico was utilized; the Gulf of Mexico was chosen because of its amenability to modeling and the ability of low vertical-mode models to reproduce the observed dynamical features of the Gulf circulation. The simulated data were obtained by flying an imaginary altimeter over the model ocean and sampling the model sea surface just as real altimeter would observe the true ocean. The data were used to initialize the numerical model and the subsequent forecast was compared to the true numerical solution. Results indicate that for a stationary, circular eddy, approximately three to four tracks (either ascending or descending) across the eddy are sufficient to ensure adequate spatial resolution.
POD/DEIM reduced-order strategies for efficient four dimensional variational data assimilation
NASA Astrophysics Data System (ADS)
Ştefănescu, R.; Sandu, A.; Navon, I. M.
2015-08-01
This work studies reduced order modeling (ROM) approaches to speed up the solution of variational data assimilation problems with large scale nonlinear dynamical models. It is shown that a key requirement for a successful reduced order solution is that reduced order Karush-Kuhn-Tucker conditions accurately represent their full order counterparts. In particular, accurate reduced order approximations are needed for the forward and adjoint dynamical models, as well as for the reduced gradient. New strategies to construct reduced order based are developed for proper orthogonal decomposition (POD) ROM data assimilation using both Galerkin and Petrov-Galerkin projections. For the first time POD, tensorial POD, and discrete empirical interpolation method (DEIM) are employed to develop reduced data assimilation systems for a geophysical flow model, namely, the two dimensional shallow water equations. Numerical experiments confirm the theoretical framework for Galerkin projection. In the case of Petrov-Galerkin projection, stabilization strategies must be considered for the reduced order models. The new reduced order shallow water data assimilation system provides analyses similar to those produced by the full resolution data assimilation system in one tenth of the computational time.
NASA Astrophysics Data System (ADS)
Kleshneva, T.; Muzik, J.; Alber, M.
2006-08-01
Recently, several techniques have been developed to improve the quality of computed tomography (CT) images of the thoracic and abdominal region that are degraded by the interference of the scanning process and respiration. Several devices for respiratory-correlated CT are available for clinical usage. They are based on the synchronization of the acquired CT image data with the respiratory motion using a signal from an external respiratory monitoring system. In this work, some practical aspects of clinical implementation of the multi-slice 4D CT scanner Somatom Sensation Open (Siemens Medical Solutions, Erlangen, Germany) equipped with a respiratory gating system (RGS) AZ-733V (Anzai Medical, Tokyo, Japan) are discussed. A new algorithm developed for automatic respiratory phase determination needed for the reconstruction of the 4D CT images is presented.
Four-dimensional compression of fMRI using JPEG2000
NASA Astrophysics Data System (ADS)
Lalgudi, Hariharan G.; Bilgin, Ali; Marcellin, Michael W.; Tabesh, Ali; Nadar, Mariappan S.; Trouard, Theodore P.
2005-04-01
Many medical imaging techniques available today generate 4D data sets. One such technique is functional magnetic resonance imaging (fMRI) which aims to determine regions of the brain that are activated due to various cognitive and/or motor functions or sensory stimuli. These data sets often require substantial resources for storage and transmission and hence call for efficient compression algorithms. fMRI data can be seen as a time-series of 3D images of the brain. Many different strategies can be employed for compressing such data. One possibility is to treat each 2D slice independently. Alternatively, it is also possible to compress each 3D image independently. Such methods do not fully exploit the redundancy present in 4D data. In this work, methods using 4D wavelet transforms are proposed. They are compared to different 2D and 3D methods. The proposed schemes are based on JPEG2000, which is included in the DICOM standard as a transfer syntax. Methodologies to test the effects of lossy compression on the end result of fMRI analysis are introduced and used to compare different compression algorithms.
Interactive access and management for four-dimensional environmental data sets using McIDAS
NASA Technical Reports Server (NTRS)
Hibbard, William L.; Tripoli, Gregory J.
1995-01-01
This grant has fundamentally changed the way that meteorologists look at the output of their atmospheric models, through the development and wide distribution of the Vis5D system. The Vis5D system is also gaining acceptance among oceanographers and atmospheric chemists. Vis5D gives these scientists an interactive three-dimensional movie of their very large data sets that they can use to understand physical mechanisms and to trace problems to their sources. This grant has also helped to define the future direction of scientific visualization through the development of the VisAD system and its lattice data model. The VisAD system can be used to interactively steer and visualize scientific computations. A key element of this capability is the flexibility of the system's data model to adapt to a wide variety of scientific data, including the integration of several forms of scientific metadata.
NASA Astrophysics Data System (ADS)
Deán-Ben, Xosé Luís.; Ermolayev, Vladimir; Mandal, Subhamoy; Ntziachristos, Vasilis; Razansky, Daniel
2016-03-01
Imaging plays an increasingly important role in clinical management and preclinical studies of cancer. Application of optical molecular imaging technologies, in combination with highly specific contrast agent approaches, eminently contributed to understanding of functional and histological properties of tumors and anticancer therapies. Yet, optical imaging exhibits deterioration in spatial resolution and other performance metrics due to light scattering in deep living tissues. High resolution molecular imaging at the whole-organ or whole-body scale may therefore bring additional understanding of vascular networks, blood perfusion and microenvironment gradients of malignancies. In this work, we constructed a volumetric multispectral optoacoustic tomography (vMSOT) scanner for cancer imaging in preclinical models and explored its capacity for real-time 3D intravital imaging of whole breast cancer allografts in mice. Intrinsic tissue properties, such as blood oxygenation gradients, along with the distribution of externally administered liposomes carrying clinically-approved indocyanine green dye (lipo-ICG) were visualized in order to study vascularization, probe penetration and extravasation kinetics in different regions of interest within solid tumors. The use of v-MSOT along with the application of volumetric image analysis and perfusion tracking tools for studies of pathophysiological processes within microenvironment gradients of solid tumors demonstrated superior volumetric imaging system performance with sustained competitive resolution and imaging depth suitable for investigations in preclinical cancer models.
Four-dimensional guidance problem with control delays. [in air traffic control automation
NASA Technical Reports Server (NTRS)
Nagarajan, N.
1976-01-01
This paper, assuming steady wind and zero sideslip, presents a discrete-time mathematical model to obtain a control law and three-dimensional flight path to guide an aircraft in a given time from a given initial state (position, velocity and heading) to a prescribed final state subject to the constraints on airspeed acceleration, and pitch and bank angles of the aircraft. For ease in implementing the control law, the control inputs are assumed to be delayed and are applied in a sequential fashion. The guidance problem is formulated as a discrete nonlinear optimal control problem with time delays in dynamics and a cost functional of Bolza form. With a quadratic penalty function to handle terminal constraints on velocity and heading, a solution technique to the control problem based on conjugate gradient algorithm is investigated. Numerical examples are presented to illustrate the applicability of this approach to solution of a terminal area guidance problem in an automated air traffic control environment.
Gaugings of four-dimensional N =3 supergravity and AdS4/CFT3 holography
NASA Astrophysics Data System (ADS)
Karndumri, Parinya; Upathambhakul, Khem
2016-06-01
We study matter-coupled N =3 gauged supergravity in four dimensions with various semisimple gauge groups. When coupled to n vector multiplets, the gauged supergravity contains 3 +n vector fields and 3 n complex scalars parametrized by S U (3 ,n )/S U (3 )×S U (n )×U (1 ) coset manifold. Semisimple gauge groups take the form of G0×H ⊂S O (3 ,n )⊂S U (3 ,n ) with H being a compact subgroup of S O (n +3 -dim (G0)). The G0 groups considered in this paper are of the form S O (3 ), S O (3 ,1 ), S O (2 ,2 ), S L (3 ,R ) and S O (2 ,1 )×S O (2 ,2 ). We find that S O (3 )×S O (3 ), S O (3 ,1 ) and S L (3 ,R ) gauge groups admit a maximally supersymmetric AdS4 critical point. The S O (2 ,1 )×S O (2 ,2 ) gauge group admits a supersymmetric Minkowski vacuum while the remaining gauge groups admit both half-supersymmetric domain wall vacua and AdS4 vacua with completely broken supersymmetry. For the S O (3 )×S O (3 ) gauge group, there exists another supersymmetric N =3 AdS4 critical point with S O (3 )diag symmetry. We explicitly give a detailed study of various holographic RG flows between AdS4 critical points, flows to nonconformal theories, and supersymmetric domain walls in each gauge group. The results provide gravity duals of N =3 Chern-Simons-matter theories in three dimensions.
Four-Dimensional Continuum Gyrokinetic Code: Neoclassical Simulation of Fusion Edge Plasmas
NASA Astrophysics Data System (ADS)
Xu, X. Q.
2005-10-01
We are developing a continuum gyrokinetic code, TEMPEST, to simulate edge plasmas. Our code represents velocity space via a grid in equilibrium energy and magnetic moment variables, and configuration space via poloidal magnetic flux and poloidal angle. The geometry is that of a fully diverted tokamak (single or double null) and so includes boundary conditions for both closed magnetic flux surfaces and open field lines. The 4-dimensional code includes kinetic electrons and ions, and electrostatic field-solver options, and simulates neoclassical transport. The present implementation is a Method of Lines approach where spatial finite-differences (higher order upwinding) and implicit time advancement are used. We present results of initial verification and validation studies: transition from collisional to collisionless limits of parallel end-loss in the scrape-off layer, self-consistent electric field, and the effect of the real X-point geometry and edge plasma conditions on the standard neoclassical theory, including a comparison of our 4D code with other kinetic neoclassical codes and experiments.
Four-dimensional in vivo X-ray microscopy with projection-guided gating
Mokso, Rajmund; Schwyn, Daniel A.; Walker, Simon M.; Doube, Michael; Wicklein, Martina; Müller, Tonya; Stampanoni, Marco; Taylor, Graham K.; Krapp, Holger G.
2015-01-01
Visualizing fast micrometer scale internal movements of small animals is a key challenge for functional anatomy, physiology and biomechanics. We combine phase contrast tomographic microscopy (down to 3.3 μm voxel size) with retrospective, projection-based gating (in the order of hundreds of microseconds) to improve the spatiotemporal resolution by an order of magnitude over previous studies. We demonstrate our method by visualizing 20 three-dimensional snapshots through the 150 Hz oscillations of the blowfly flight motor. PMID:25762080
Kimple, Randall J; Wallen, Eric M; Pruthi, Raj; Marks, Lawrence B
2010-01-01
To retrospectively determine the proportion of prostate cancer patients who are appropriate candidates for prostate localization with Calypso (Calypso Medical, Seattle, WA); to assess the accuracy of surface anatomy in predicting prostate depth; and to describe a simple clinical algorithm predicting patient's appropriateness for Calypso localization. Medical records and archived CT scans of all patients treated for localized prostate cancer at our institution between 2006 and 2007 were reviewed. Association between the feasibility of Calypso use, the depth of the prostate from the anterior torso, and a variety of anatomic factors were assessed (ANOVA, linear regression, and ROC). Patients were appropriate for the Calypso system in 91% of cases (localize and track, 52%; localize only, 39%). Strong correlation between greater trochanter location and the posterior prostate was seen (r 2 = 0.91, mean difference 0.6 cm). The negative predictive value of the greater trochanter measurements was 31%. Thirty-one out of forty-five patients (69%) who were deemed inappropriate for Calypso based on greater trochanter to anterior torso measurements were eligible on the basis of CT-based measurements of prostate depth. Weight, BMI, waist circumference, and hip circumference correlated with distance from the prostate to the anterior torso and were predictive of Calypso appropriateness. All patients with weight
NASA Astrophysics Data System (ADS)
Rȩbilas, Krzysztof
2015-07-01
A deductive approach to the relativistic law of motion presented by Kosyakov (2014 Eur. J. Phys. 35 025012) is critically analysed. We point out that the Kosyakov argumentation is flawed and ineffective. On the other hand we show how an implicit assumption made by the author could be used to perform a successful reasoning. Also, another method to derive the relativistic equation of motion, in terms of Lorentz-invariant three-vectors, is recalled.
NASA Astrophysics Data System (ADS)
Kosyakov, B. P.
2014-03-01
A definition of the electromagnetic field can be neatly formulated by recognizing that the simplest form of the four-force is indeed feasible. We show that Maxwell’s equations almost entirely stem from the properties of spacetime, notably from the fact that our world has dimension d = 4. Their complete reconstruction requires three additional assumptions that are seemingly divorced from spacetime properties but which may, in fact, have much to do with their geometry.
Chen, Sun; Ren, Yunyun; Chen, Ping; Niu, Jianmei; Li, Cao; Sun, Kun
2016-01-01
Objective This study aimed at investigating the feasibility of using the spatiotemporal image correlation (STIC) technology for prenatal cardiac screening, finding factors that influence the offline evaluation of reconstructed fetal heart, and establishing an optimal acquisition scheme. Methods The study included 452 gravidae presenting for routine screening at 3 maternity centers at 20–38 gestational weeks. The factors influencing the quality of STIC volume data were evaluated using t test, chi-square test, and logistic regression analysis. The predictive power was evaluated using the receiver operating characteristic (ROC) curve. Results Among the 452 fetuses enrolled, 353 (78.1%) were identified as successful and 99 (21.9%) as failure of evaluation of the reconstructed fetal heart. The total success rate of qualified STIC images was 78.1%. The display rates of reconstructed cardiac views were 86.5% (four-chamber view), 92.5% (left ventricular outflow tract view), 92.7% (right ventricular outflow tract view), 89.9% (three-vessel trachea view), 63.9% (aortic arch view), 81.4% (ductal arch view), 81% (short-axis view of great vessels), 80.1% (long-cava view), and 86.9% (abdominal view). A logistic regression analysis showed that more than 28 gestational weeks [OR = 0.39 (CI 95% 0.16, 0.19), P = 0.035], frequent fetal movements [OR = 0.37 (CI 95% 0.16, 0.87), P = 0.022], shadowing [OR = 0.36 (CI 95% 0.19, 0.72), P = 0.004], spine location at 10–2 o’clock [OR = 0.08 (CI 95% 0.02, 0.27), P = 0.0], and original cardiac view [OR = 0.51 (0.25, 0.89), P = 0.019] had a significant impact on the quality of STIC. The area under the ROC curve was 0.775. Conclusions Fetal cardiac-STIC seems a feasible tool for prenatal screening of congenital heart diseases. The influence factors on the quality of STIC images included the intensity of training, gestational age, fetal conditions and parameter settings. The optimal acquisition scheme may improve the application and widespread use of cardiac STIC. PMID:27314236
Fehm, Thomas Felix; Razansky, Daniel; Deán-Ben, Xosé Luís
2014-10-27
Ultrasonography and optoacoustic imaging share powerful advantages related to the natural aptitude for real-time image rendering with high resolution, the hand-held operation, and lack of ionizing radiation. The two methods also possess very different yet highly complementary advantages of the mechanical and optical contrast in living tissues. Nonetheless, efficient integration of these modalities remains challenging owing to the fundamental differences in the underlying physical contrast, optimal signal acquisition, and image reconstruction approaches. We report on a method for hybrid acquisition and reconstruction of three-dimensional pulse-echo ultrasound and optoacoustic images in real time based on passive ultrasound generation with an optical absorber, thus avoiding the hardware complexity of active ultrasound generation. In this way, complete hybrid datasets are generated with a single laser interrogation pulse, resulting in simultaneous rendering of ultrasound and optoacoustic images at an unprecedented rate of 10 volumetric frames per second. Performance is subsequently showcased in phantom experiments and in-vivo measurements from a healthy human volunteer, confirming general clinical applicability of the method.
NASA Astrophysics Data System (ADS)
Fehm, Thomas Felix; Deán-Ben, Xosé Luís; Razansky, Daniel
2014-10-01
Ultrasonography and optoacoustic imaging share powerful advantages related to the natural aptitude for real-time image rendering with high resolution, the hand-held operation, and lack of ionizing radiation. The two methods also possess very different yet highly complementary advantages of the mechanical and optical contrast in living tissues. Nonetheless, efficient integration of these modalities remains challenging owing to the fundamental differences in the underlying physical contrast, optimal signal acquisition, and image reconstruction approaches. We report on a method for hybrid acquisition and reconstruction of three-dimensional pulse-echo ultrasound and optoacoustic images in real time based on passive ultrasound generation with an optical absorber, thus avoiding the hardware complexity of active ultrasound generation. In this way, complete hybrid datasets are generated with a single laser interrogation pulse, resulting in simultaneous rendering of ultrasound and optoacoustic images at an unprecedented rate of 10 volumetric frames per second. Performance is subsequently showcased in phantom experiments and in-vivo measurements from a healthy human volunteer, confirming general clinical applicability of the method.
NASA Technical Reports Server (NTRS)
Hasler, A. F.; Desjardins, M.; Shenk, W. E.
1979-01-01
Simultaneous Geosynchronous Operational Environmental Satellite (GOES) 1 km resolution visible image pairs can provide quantitative three dimensional measurements of clouds. These data have great potential for severe storms research and as a basic parameter measurement source for other areas of meteorology (e.g. climate). These stereo cloud height measurements are not subject to the errors and ambiguities caused by unknown cloud emissivity and temperature profiles that are associated with infrared techniques. This effort describes the display and measurement of stereo data using digital processing techniques.
NASA Astrophysics Data System (ADS)
Bateni, S. M.; Xu, T.
2015-12-01
Accurate estimation of water and heat fluxes is required for irrigation scheduling, weather prediction, and water resources planning and management. A weak-constraint variational data assimilation (WC-VDA) scheme is developed to estimate water and heat fluxes by assimilating sequences of land surface temperature (LST) observations. The commonly used strong-constraint VDA systems adversely affect the accuracy of water and heat flux estimates as they assume the model is perfect. The WC-VDA approach accounts for structural and model errors and generates more accurate results via adding a model error term into the surface energy balance equation. The two key unknown parameters of the WC-VDA system (i.e., CHN, the bulk heat transfer coefficient and EF, evaporative fraction) and the model error term are optimized by minimizing the cost function. The WC-VDA model was tested at two sites with contrasting hydrological and vegetative conditions: the Daman site (a wet site located in an oasis area and covered by seeded corn) and the Huazhaizi site (a dry site located in a desert area and covered by sparse grass) in middle stream of Heihe river basin, northwest China. Compared to the strong-constraint VDA system, the WC-VDA method generates more accurate estimates of water and energy fluxes over the desert and oasis sites with dry and wet conditions.
Qin, Yue; Zhang, Ying; Zhou, Xiaohang; Wang, Yu; Sun, Wei; Chen, Lizhu; Zhao, Dan; Zhan, Ying; Cai, Ailu
2014-07-01
The aim of this study was to evaluate the use of 4-D echocardiography with inversion mode and spatiotemporal image correlation (IM-STIC) in the detection of normal and abnormal fetal hearts. We retrospectively studied 112 normal fetuses and 16 fetuses with a confirmed diagnosis of congenital heart disease. Two volumes were acquired from each of the fetuses using transverse and sagittal sweeps. Volumes were reconstructed with IM-STIC. In normal fetuses, IM-STIC facilitated visualization of the interior structures of the fetal heart and great vessels. The visualization rates of intended planes obtained from IM-STIC 4D data ranged from 55% to 100%. In 16 fetuses with congenital heart disease, IM-STIC was able to display the cardiac malformations using digital casting. Some of the malformations were suspected during pre-natal 2-D echocardiography, and their pre-natal IM-STIC diagnoses were confirmed by post-natal echocardiography, surgery and/or autopsy. Hence, 4-D IM-STIC allows better visualization of complex congenital heart disease and should be considered a very useful addition to 2-D echocardiography. PMID:24785438
Platz, Timothy A; Kukar, Moshim; Elmarzouky, Rania; Cance, William; Abdelhalim, Ahmed
2014-09-28
Modification of 4-dimensional computed tomography (4D-CT) technique with volume rendering reconstructions and significant dose reduction is a safe and accurate method of pre-operative localization for primary hyperparathyroidism. Modified low dose 4D-CT with volume rendering reconstructions provides precise preoperative localization and is associated with a significant reduction in radiation exposure compared to classic preoperative localizing techniques. It should be considered the preoperative localization study of choice for primary hyperparathyroidism. PMID:25276315
Fast, J.D.; O`Steen, B.L.
1994-12-31
The results of this study indicate that the current data assimilation technique can have a positive impact on the mesoscale flow fields; however, care must be taken in its application to grids of relatively fine horizontal resolution. Continuous FDDA is a useful tool in producing high-resolution mesoscale analysis fields that can be used to (1) create a better initial conditions for mesoscale atmospheric models and (2) drive transport models for dispersion studies. While RAMS is capable of predicting the qualitative flow during this evening, additional experiments need to be performed to improve the prognostic forecasts made by RAMS and refine the FDDA procedure so that the overall errors are reduced even further. Despite the fact that a great deal of computational time is necessary in executing RAMS and LPDM in the configuration employed in this study, recent advances in workstations is making applications such as this more practical. As the speed of these machines increase in the next few years, it will become feasible to employ prognostic, three-dimensional mesoscale/transport models to routinely predict atmospheric dispersion of pollutants, even to highly complex terrain. For example, the version of RAMS in this study could be run in a ``nowcasting`` model that would continually assimilate local and regional observations as soon as they become available. The atmospheric physics in the model would be used to determine the wind field where no observations are available. The three-dimensional flow fields could be used as dynamic initial conditions for a model forecast. The output from this type of modeling system will have to be compared to existing diagnostic, mass-consistent models to determine whether the wind field and dispersion forecasts are significantly improved.
Castillo, S; Castillo, R; Castillo, E; Pan, T; Ibbott, G; Balter, P; Hobbs, B; Dai, J; Guerrero, T
2014-06-15
Purpose: Artifacts arising from the 4D CT acquisition and post-processing methods add systematic uncertainty to the treatment planning process. We propose an alternate cine 4D CT acquisition and post-processing method to consistently reduce artifacts, and explore patient parameters indicative of image quality. Methods: In an IRB-approved protocol, 18 patients with primary thoracic malignancies received a standard cine 4D CT acquisition followed by an oversampling 4D CT that doubled the number of images acquired. A second cohort of 10 patients received the clinical 4D CT plus 3 oversampling scans for intra-fraction reproducibility. The clinical acquisitions were processed by the standard phase sorting method. The oversampling acquisitions were processed using Dijkstras algorithm to optimize an artifact metric over available image data. Image quality was evaluated with a one-way mixed ANOVA model using a correlation-based artifact metric calculated from the final 4D CT image sets. Spearman correlations and a linear mixed model tested the association between breathing parameters, patient characteristics, and image quality. Results: The oversampling 4D CT scans reduced artifact presence significantly by 27% and 28%, for the first cohort and second cohort respectively. From cohort 2, the inter-replicate deviation for the oversampling method was within approximately 13% of the cross scan average at the 0.05 significance level. Artifact presence for both clinical and oversampling methods was significantly correlated with breathing period (ρ=0.407, p-value<0.032 clinical, ρ=0.296, p-value<0.041 oversampling). Artifact presence in the oversampling method was significantly correlated with amount of data acquired, (ρ=-0.335, p-value<0.02) indicating decreased artifact presence with increased breathing cycles per scan location. Conclusion: The 4D CT oversampling acquisition with optimized sorting reduced artifact presence significantly and reproducibly compared to the phase-sorted clinical acquisition.
Nakaoka, Kazutoshi; Hamada, Yoshiki; Nakatani, Hayaki; Shigeta, Yuko; Hirai, Shinya; Ikawa, Tomoko; Mishima, Akira; Ogawa, Takumi
2015-01-01
Objectives: The surgical target of Masticatory muscle tendon-aponeurosis hyperplasia (MMTAH) is the masseter or temporal muscle. In our clinic, the 4-dimentional muscle model (4DMM) has been used to decide if we should approach to the masseter or temporal muscle. The aim of this study is validate the clinical usefulness of 4DMM on the basis of the surgical results. Methods: The 4DMM was constructed from the digital data of 3D-CT and 4-dimentional mandibular movements of the patients. It made us to able to visually observe the expansion rate of masticatory muscles at maximum mouth opening comparing to their length at closed mouth position. Fifteen patients were applied the 4DMM before the surgical treatment and 2 healthy volunteers were enrolled as control group. Results: The expansion rate of temporal muscle at the maximum mouth opening in the patient group was significantly less than that in the control group (P < 0.05). On the other hand, the masseter muscles of all patients were expanded as same as the control group. Therefore the main cause of limitation of mouth-opening was suggested to be a contracture of the temporal muscle. Consequently, we performed successful bilateral coronoidectomy with no surgical intervention to the masseter muscles in all patients. Conclusion: The present 4DMM would be valuable modality to decide the target muscle of surgical treatment for patients with MMTAH. In this pathology, contracture of the temporal muscle seems to be main cause of limited mouth opening. PMID:26352365
Deán-Ben, Xosé Luís; Ford, Steven James; Razansky, Daniel
2015-01-01
Functional imaging of mouse models of cardiac health and disease provides a major contribution to our fundamental understanding of the mammalian heart. However, imaging murine hearts presents significant challenges due to their small size and rapid heart rate. Here we demonstrate the feasibility of high-frame-rate, noninvasive optoacoustic imaging of the murine heart. The temporal resolution of 50 three-dimensional frames per second provides functional information at important phases of the cardiac cycle without the use of gating or other motion-reduction methods. Differentiation of the blood oxygenation state in the heart chambers was enabled by exploiting the wavelength dependence of optoacoustic signals. Real-time volumetric tracking of blood perfusion in the cardiac chambers was also evaluated using indocyanine green. Taken together, the newly-discovered capacities offer a unique tool set for in-vivo structural and functional imaging of the whole heart with high spatio-temporal resolution in all three dimensions. PMID:26130401
NASA Astrophysics Data System (ADS)
Chung, Kyung Tae; Lee, Jong Woo
1989-08-01
A connection which is both Einstein and semisymmetric is called an SE connection, and a generalized n-dimensional Riemannian manifold on which the differential geometric structure is imposed by g λμ through an SE connection is called an n-dimensional SE manifold and denoted by SEXn. This paper is a direct continuation of earlier work. In this paper, we derive the generalized fundamental equations for the hypersubmanifold of SEXn, including generalized Gauss formulas, generalized Weingarten equations, and generalized Gauss-Codazzi equations.
NASA Astrophysics Data System (ADS)
Pinnington, Ewan; Casella, Eric; Dance, Sarah; Lawless, Amos; Morison, James; Nichols, Nancy; Wilkinson, Matthew; Quaife, Tristan
2016-04-01
Forest ecosystems play an important role in sequestering human emitted carbon-dioxide from the atmosphere and therefore greatly reduce the effect of anthropogenic induced climate change. For that reason understanding their response to climate change is of great importance. Efforts to implement variational data assimilation routines with functional ecology models and land surface models have been limited, with sequential and Markov chain Monte Carlo data assimilation methods being prevalent. When data assimilation has been used with models of carbon balance, background "prior" errors and observation errors have largely been treated as independent and uncorrelated. Correlations between background errors have long been known to be a key aspect of data assimilation in numerical weather prediction. More recently, it has been shown that accounting for correlated observation errors in the assimilation algorithm can considerably improve data assimilation results and forecasts. In this paper we implement a 4D-Var scheme with a simple model of forest carbon balance, for joint parameter and state estimation and assimilate daily observations of Net Ecosystem CO2 Exchange (NEE) taken at the Alice Holt forest CO2 flux site in Hampshire, UK. We then investigate the effect of specifying correlations between parameter and state variables in background error statistics and the effect of specifying correlations in time between observation error statistics. The idea of including these correlations in time is new and has not been previously explored in carbon balance model data assimilation. In data assimilation, background and observation error statistics are often described by the background error covariance matrix and the observation error covariance matrix. We outline novel methods for creating correlated versions of these matrices, using a set of previously postulated dynamical constraints to include correlations in the background error statistics and a Gaussian correlation function to include time correlations in the observation error statistics. The methods used in this paper will allow the inclusion of time correlations between many different observation types in the assimilation algorithm, meaning that previously neglected information can be accounted for. In our experiments we compared the results using our new correlated background and observation error covariance matrices and those using diagonal covariance matrices. We found that using the new correlated matrices reduced the root mean square error in the 14 year forecast of daily NEE by 44 % decreasing from 4.22 g C m‑2 day‑1 to 2.38 g C m‑2 day‑1.
Johnson, Tim; Versteeg, Roelof; Thomle, Jon; Hammond, Glenn; Chen, Xingyuan; Zachara, John
2015-08-01
Our paper describes and demonstrates two methods of providing a priori information to the surface-based time-lapse three-dimensional electrical resistivity tomography (ERT) problem for monitoring stage-driven or tide-driven surface water intrusion into aquifers. First, a mesh boundary is implemented that conforms to the known location of the water table through time, thereby enabling the inversion to place a sharp bulk conductivity contrast at that boundary without penalty. Moreover, a nonlinear inequality constraint is used to allow only positive or negative transient changes in EC to occur within the saturated zone, dependent on the relative contrast in fluid electrical conductivity between surface water and groundwater. A 3-D field experiment demonstrates that time-lapse imaging results using traditional smoothness constraints are unable to delineate river water intrusion. The water table and inequality constraints provide the inversion with the additional information necessary to resolve the spatial extent of river water intrusion through time.
NASA Astrophysics Data System (ADS)
Lundquist, J. K.; Banta, R. M.; Pichugina, Y.; Brewer, A.; Alvarez, R. J.; Sandberg, S. P.; Kelley, N. D.; Aitken, M.; Clifton, A.; Mirocha, J. D.
2011-12-01
To support substantial deployment of renewably-generated electricity from the wind, critical information about the variability of wind turbine wakes in the real atmosphere from multi-MW turbines is required. The assessment of the velocity deficit and turbulence associated with industrial-scale turbines is a major issue for wind farm design, particularly with respect to the optimization of the spacing between turbines. The significant velocity deficit and turbulence generated by upstream turbines can reduce the power production and produce harmful vibrations in downstream turbines, which can lead to excess maintenance costs. The complexity of wake effects depends on many factors arising from both hardware (turbine size, rotor speed, and blade geometry, etc.) and from meteorological considerations such as wind velocity, gradients of wind across the turbine rotor disk, atmospheric stability, and atmospheric turbulence. To characterize the relationships between the meteorological inflow and turbine wakes, a collaborative field campaign was designed and carried out at the Department of Energy's National Wind Technology Center (NREL/NWTC) in south Boulder, Colorado, in spring 2011. This site often experiences channeled flow with a consistent wind direction, enabling robust statistics of wake velocity deficits and turbulence enhancements. Using both in situ and remote sensing instrumentation, measurements upwind and downwind of multi-megawatt wind turbine in complex terrain quantified the variability of wind turbine inflow and wakes from an industrial-scale turbine. The turbine of interest has a rated power of 2.3 MW, a rotor diameter of 100m, and a hub height of 80m. In addition to several meteorological towers, one extending to hub height (80m) and another extending above the top of the rotor disk (135m), a Triton mini-sodar and a Windcube lidar characterized the inflow to the turbine and the variability across the site. The centerpiece instrument of the TWICS campaign was the NOAA High Resolution Doppler lidar (HRDL), a scanning lidar which captured three-dimensional images of the turbine inflow and wake. Over several weeks, 48+ hours of HRDL observations during a variety of wind speed and atmospheric stability conditions were collected using three scanning strategies. Wake features such as lofting, meandering, intersection with the ground, and expansion factors are identified and discussed. Observations of a remarkably long-distance wake are presented and compared with existing wake models.
Johnson, Tim; Versteeg, Roelof; Thomle, Jon; Hammond, Glenn; Chen, Xingyuan; Zachara, John
2015-08-01
Our paper describes and demonstrates two methods of providing a priori information to the surface-based time-lapse three-dimensional electrical resistivity tomography (ERT) problem for monitoring stage-driven or tide-driven surface water intrusion into aquifers. First, a mesh boundary is implemented that conforms to the known location of the water table through time, thereby enabling the inversion to place a sharp bulk conductivity contrast at that boundary without penalty. Moreover, a nonlinear inequality constraint is used to allow only positive or negative transient changes in EC to occur within the saturated zone, dependent on the relative contrast in fluid electrical conductivity between surfacemore » water and groundwater. A 3-D field experiment demonstrates that time-lapse imaging results using traditional smoothness constraints are unable to delineate river water intrusion. The water table and inequality constraints provide the inversion with the additional information necessary to resolve the spatial extent of river water intrusion through time.« less
NASA Astrophysics Data System (ADS)
Borowski, A.; Kühn, O.
2008-05-01
Quantum dynamics simulations are performed for a diatomics-in-molecules based model of Br 2 in solid Ar which incorporates four nuclear degrees of freedom and four electronic states. The nuclear motions comprise two large amplitude coordinates describing the Br 2 bond distance and an effective symmetry-preserving matrix mode. Two symmetry-lowering harmonic modes are added in the spirit of linear vibronic coupling theory. Initiating the dynamics on the B state by means of an ultrafast laser pulse, nonadiabatic transitions to the two degenerate C states are monitored and the effect of vibrational preexcitation in the electronic ground state is investigated.
Redmond, Kristin J.; Song, Danny Y.; Fox, Jana L.; Zhou, Jessica; Rosenzweig, C. Nicole; Ford, Eric
2009-12-01
Purpose: To determine whether lung tumor respiratory excursion at simulation is predictive of excursion during radiation and whether phase offsets between tumor and surrogate markers are constant throughout treatment. Methods and Materials: Respiration-correlated CT scans and two rescans (using a Brilliance Big Bore spiral CT simulator; Philips, Inc.) were obtained from 20 patients at simulation. Gross tumor volume (GTV) was contoured on 10 phases of the respiratory cycle, and excursions were calculated. Diaphragm and xyphoid motion were quantified. Phase offsets, DELTAPHI, were calculated for patients with a GTV motion of >3 mm. Interfraction differences in excursions between simulation and rescans and magnitudes of variation in phase offset between fractions were evaluated. Results: Mean GTV excursions at simulation in superior-inferior, anterior-posterior, and medial-lateral directions were 0.67, 0.29, and 0.21 cm, respectively. The magnitude of superior-inferior GTV excursion correlated with tumor location (upper vs. lower lobe, p = 0.011). GTV excursions between simulation and rescan 1 (p = 0.115) and between simulation and rescan 2 (p = 0.071) were stable. Fourteen patients were analyzed for variations in phase offsets. GTV-xyphoid phase offset changed significantly between simulation and rescan 1 (p = 0.007) and simulation and rescan 2 (p = 0.008), with mean DELTAPHI values of 13.2% (rescan 1) and 14.3% (rescan 2). Xyphoid-diaphragm offset changed between simulation and rescan 1 (p = 0.004) and between simulation and rescan 2 (p = 0.012), with mean DELTAPHI values of 14.5% (rescan 1) and 7.6% (rescan 2). Conclusions: Interfraction consistency in tumor excursion suggests tumor excursion at simulation may direct therapy. Significant variations in phase lag between GTV and other anatomic structures throughout treatment have important implications for techniques that rely on surrogate structures to predict tumor motion
Lin, Chao; Shen, Xueju; Li, Baochen
2014-08-25
We demonstrate that all parameters of optical lightwave can be simultaneously designed as keys in security system. This multi-dimensional property of key can significantly enlarge the key space and further enhance the security level of the system. The single-shot off-axis digital holography with orthogonal polarized reference waves is employed to perform polarization state recording on object wave. Two pieces of polarization holograms are calculated and fabricated to be arranged in reference arms to generate random amplitude and phase distribution respectively. When reconstruction, original information which is represented with QR code can be retrieved using Fresnel diffraction with decryption keys and read out noise-free. Numerical simulation results for this cryptosystem are presented. An analysis on the key sensitivity and fault tolerance properties are also provided. PMID:25321276
ERIC Educational Resources Information Center
de Freitas, Sara; Rebolledo-Mendez, Genaro; Liarokapis, Fotis; Magoulas, George; Poulovassilis, Alexandra
2010-01-01
Traditional approaches to learning have often focused upon knowledge transfer strategies that have centred on textually-based engagements with learners, and dialogic methods of interaction with tutors. The use of virtual worlds, with text-based, voice-based and a feeling of "presence" naturally is allowing for more complex social interactions and…
Hu, E; Lasio, G; Yi, B
2014-06-01
Purpose: The Iterative Subtraction Algorithm (ISA) method generates retrospectively a pre-selected motion phase cone-beam CT image from the full motion cone-beam CT acquired at standard rotation speed. This work evaluates ISA method with real lung patient data. Methods: The goal of the ISA algorithm is to extract motion and no- motion components form the full reconstruction CBCT. The workflow consists of subtracting from the full CBCT all of the undesired motion phases and obtain a motion de-blurred single-phase CBCT image, followed by iteration of this subtraction process. ISA is realized as follows: 1) The projections are sorted to various phases, and from all phases, a full reconstruction is performed to generate an image CTM. 2) Generate forward projections of CTM at the desired phase projection angles, the subtraction of projection and the forward projection will reconstruct a CTSub1, which diminishes the desired phase component. 3) By adding back the CTSub1 to CTm, no motion CBCT, CTS1, can be computed. 4) CTS1 still contains residual motion component. 5) This residual motion component can be further reduced by iteration.The ISA 4DCBCT technique was implemented using Varian Trilogy accelerator OBI system. To evaluate the method, a lung patient CBCT dataset was used. The reconstruction algorithm is FDK. Results: The single phase CBCT reconstruction generated via ISA successfully isolates the desired motion phase from the full motion CBCT, effectively reducing motion blur. It also shows improved image quality, with reduced streak artifacts with respect to the reconstructions from unprocessed phase-sorted projections only. Conclusion: A CBCT motion de-blurring algorithm, ISA, has been developed and evaluated with lung patient data. The algorithm allows improved visualization of a single phase motion extracted from a standard CBCT dataset. This study has been supported by National Institute of Health through R01CA133539.
Nakano, M; Kida, S; Masutani, Y; Shiraki, T; Yamamoto, K; Shiraishi, K; Nakagawa, K; Haga, A
2014-06-01
Purpose: In the previous study, we developed time-ordered fourdimensional (4D) cone-beam CT (CBCT) technique to visualize nonperiodic organ motion, such as peristaltic motion of gastrointestinal organs and adjacent area, using half-scan reconstruction method. One important obstacle was that truncation of projection was caused by asymmetric location of flat-panel detector (FPD) in order to cover whole abdomen or pelvis in one rotation. In this study, we propose image mosaicing to extend projection data to make possible to reconstruct full field-of-view (FOV) image using half-scan reconstruction. Methods: The projections of prostate cancer patients were acquired using the X-ray Volume Imaging system (XVI, version 4.5) on Synergy linear accelerator system (Elekta, UK). The XVI system has three options of FOV, S, M and L, and M FOV was chosen for pelvic CBCT acquisition, with a FPD panel 11.5 cm offset. The method to produce extended projections consists of three main steps: First, normal three-dimensional (3D) reconstruction which contains whole pelvis was implemented using real projections. Second, virtual projections were produced by reprojection process of the reconstructed 3D image. Third, real and virtual projections in each angle were combined into one extended mosaic projection. Then, 4D CBCT images were reconstructed using our inhouse reconstruction software based on Feldkamp, Davis and Kress algorithm. The angular range of each reconstruction phase in the 4D reconstruction was 180 degrees, and the range moved as time progressed. Results: Projection data were successfully extended without discontinuous boundary between real and virtual projections. Using mosaic projections, 4D CBCT image sets were reconstructed without artifacts caused by the truncation, and thus, whole pelvis was clearly visible. Conclusion: The present method provides extended projections which contain whole pelvis. The presented reconstruction method also enables time-ordered 4D CBCT reconstruction of organs with non-periodic motion with full FOV without projection-truncation artifacts. This work was partly supported by the JSPS Core-to-Core Program(No. 23003). This work was partly supported by JSPS KAKENHI 24234567.
NASA Astrophysics Data System (ADS)
Kane, Gordon
2015-12-01
String/M-theory is an exciting framework within which we try to understand our universe and its properties. Compactified string/M-theories address and offer solutions to almost every important question and issue in particle physics and particle cosmology. But earlier goals of finding a top-down “vacuum selection” principle and deriving the 4D theory have not yet been realized. Does that mean we should stop trying, as nearly all string theorists have? Or can we proceed in the historical way to make a few generic, robust assumptions not closely related to observables, and follow where they lead to testable predictions and explanations? Making only very generic assumptions is a significant issue. I discuss how to try to proceed with this approach, particularly in M-theory compactified on a 7D manifold of G2 holonomy. One goal is to understand our universe as a string/M-theory vacuum for its own sake, in the long tradition of trying to understand our world, and what that implies. In addition, understanding our vacuum may be a prelude to understanding its connection to the multiverse.
Dowdell, Stephen; Paganetti, Harald; Grassberger, Clemens
2013-12-15
Purpose: To compare motion effects in intensity modulated proton therapy (IMPT) lung treatments with different levels of intensity modulation.Methods: Spot scanning IMPT treatment plans were generated for ten lung cancer patients for 2.5Gy(RBE) and 12Gy(RBE) fractions and two distinct energy-dependent spot sizes (σ∼8–17 mm and ∼2–4 mm). IMPT plans were generated with the target homogeneity of each individual field restricted to <20% (IMPT{sub 20%}). These plans were compared to full IMPT (IMPT{sub full}), which had no restriction on the single field homogeneity. 4D Monte Carlo simulations were performed upon the patient 4DCT geometry, including deformable image registration and incorporating the detailed timing structure of the proton delivery system. Motion effects were quantified via comparison of the results of the 4D simulations (4D-IMPT{sub 20%}, 4D-IMPT{sub full}) with those of a 3D Monte Carlo simulation (3D-IMPT{sub 20%}, 3D-IMPT{sub full}) upon the planning CT using the equivalent uniform dose (EUD), V{sub 95} and D{sub 1}-D{sub 99}. The effects in normal lung were quantified using mean lung dose (MLD) and V{sub 90%}.Results: For 2.5Gy(RBE), the mean EUD for the large spot size is 99.9%± 2.8% for 4D-IMPT{sub 20%} compared to 100.1%± 2.9% for 4D-IMPT{sub full}. The corresponding values are 88.6%± 8.7% (4D-IMPT{sub 20%}) and 91.0%± 9.3% (4D-IMPT{sub full}) for the smaller spot size. The EUD value is higher in 69.7% of the considered deliveries for 4D-IMPT{sub full}. The V{sub 95} is also higher in 74.7% of the plans for 4D-IMPT{sub full}, implying that IMPT{sub full} plans experience less underdose compared to IMPT{sub 20%}. However, the target dose homogeneity is improved in the majority (67.8%) of plans for 4D-IMPT{sub 20%}. The higher EUD and V{sub 95} suggests that the degraded homogeneity in IMPT{sub full} is actually due to the introduction of hot spots in the target volume, perhaps resulting from the sharper in-target dose gradients. The greatest variations between the IMPT{sub 20%} and IMPT{sub full} deliveries are observed for patients with the largest motion amplitudes. These patients would likely be treated using gating or another motion mitigation technique, which was not the focus of this study.Conclusions: For the treatment parameters considered in this study, the differences between IMPT{sub full} and IMPT{sub 20%} are only likely to be clinically significant for patients with large (>20 mm) motion amplitudes.
Hennig, Carsten; Schmatz, Stefan
2005-06-15
The exothermic gas-phase bimolecular nucleophilic substitution (S{sub N}2) reaction Cl{sup -}+CH{sub 3}Br ({upsilon}{sub 1}{sup '},{upsilon}{sub 2}{sup '},{upsilon}{sub 3}{sup '}){yields}ClCH{sub 3} ({upsilon}{sub 1},{upsilon}{sub 2},{upsilon}{sub 3})+Br{sup -} and the corresponding endothermic reverse reaction have been studied by time-independent quantum scattering calculations in hyperspherical coordinates on a coupled-cluster potential-energy surface. The dimensionality-reduced model takes four degrees of freedom into account [Cl-C and C-Br stretching modes (quantum numbers {upsilon}{sub 3}{sup '} and {upsilon}{sub 3}); totally symmetric modes of the methyl group, i.e., C-H stretching ({upsilon}{sub 1}{sup '} and {upsilon}{sub 1}) and umbrella bending vibrations ({upsilon}{sub 2}{sup '} and {upsilon}{sub 2})]. Diagonalization of the Hamiltonian was performed employing the Lanczos algorithm with a variation of partial reorthogonalization. A narrow grid in the total energy was employed so that long-living resonance states could be resolved and extracted. While excitation of the reactant umbrella bending mode already leads to a considerable enhancement of the reaction probability, its combination with vibrational excitation of the broken C-Br bond, (0, 1, 1), results in a strong synergic effect that can be rationalized by the similarity with the classical transitional normal mode. Exciting the C-H stretch has a non-negligible effect on the reaction probability, while for larger translational energies this mode follows the expected spectatorlike behavior. Combination of C-Br stretch and symmetric C-H, (1,0,1), stretch does not show a cooperative effect. Contrary to the spectator mode concept, energy originally stored in the C-H stretching mode is by no means conserved, but almost completely released in other modes of the reaction products. Products are most likely formed in states with a high degree of excitation in the new C-Cl bond, while the internal modes of the methyl group are less important. Reactants with combined umbrella/C-Br stretch excitation, (0, 1, 1), may yield products with two quanta in the umbrella mode.
Sindoni, Alessandro; Minutoli, Fabio; Pontoriero, Antonio; Iatì, Giuseppe; Baldari, Sergio; Pergolizzi, Stefano
2016-06-01
In the past decade, Positron Emission Tomography (PET) has become a routinely used methodology for the assessment of solid tumors, which can detect functional abnormalities even before they become morphologically evident on conventional imaging. PET imaging has been reported to be useful in characterizing solitary pulmonary nodules, guiding biopsy, improving lung cancer staging, guiding therapy, monitoring treatment response and predicting outcome. This review focuses on the most relevant and recent literature findings, highlighting the current role of PET/CT and the evaluation of 4D-PET/CT modality for radiation therapy planning applications. Current evidence suggests that gross tumor volume delineation based on 4D-PET/CT information may be the best approach currently available for its delineation in thoracic cancers (lung and non-lung lesions). In our opinion, its use in this clinical setting is strongly encouraged, as it may improve patient treatment outcome in the setting of radiation therapy for cancers of the thoracic region, not only involving lung, but also lymph nodes and esophageal tissue. Literature results warrants further investigation in future prospective studies, especially in the setting of dose escalation. PMID:27133755
Johnson, Timothy C.; Versteeg, Roelof; Thomle, Jonathan N.; Hammond, Glenn E.; Chen, Xingyuan; Zachara, John M.
2015-08-01
This paper describes and demonstrates two methods of providing a-priori information to a surface-based time-lapse three-dimensional electrical resistivity tomography (ERT) problem for monitoring stage-driven river bank storage along the Columbia River in the state of Washington, USA. First, a transient warping mesh boundary is implemented that conforms to the known location of the water table boundary through time, thereby enabling the inversion to place a sharp bulk-conductivity contrast at that boundary without penalty. Second, because river water specific conductance is less than groundwater specific conductance, a non-linear inequality constraint is used to allow only negative transient changes in bulk conductivity to occur within the saturated zone during periods of elevated river stage with respect to baseline conditions. Whereas time-lapse imaging results using traditional smoothness constraints are unable to delineate river bank storage, the water table and inequality constraints provide the inversion with the additional information necessary to resolve the spatial extent of river water intrusion through time. A surface based ERT array of 352 electrodes was used to autonomously produce four images per day of changes in bulk conductivity associated with river water intrusion over an area of approximately 300 m2 from April through October of 2013. Results are validated by comparing changes in bulk conductivity time series with corresponding changes in fluid specific conductance at several inland monitoring wells.
Sawant, A
2015-06-15
Purpose: Respiratory correlated 4DCT images are generated under the assumption of a regular breathing cycle. This study evaluates the error in 4DCT-based target position estimation in the presence of irregular respiratory motion. Methods: A custom-made programmable externally-and internally-deformable lung motion phantom was placed inside the CT bore. An abdominal pressure belt was placed around the phantom to mimic clinical 4DCT acquisitio and the motion platform was programmed with a sinusoidal (±10mm, 10 cycles per minute) motion trace and 7 motion traces recorded from lung cancer patients. The same setup and motion trajectories were repeated in the linac room and kV fluoroscopic images were acquired using the on-board imager. Positions of 4 internal markers segmented from the 4DCT volumes were overlaid upon the motion trajectories derived from the fluoroscopic time series to calculate the difference between estimated (4DCT) and “actual” (kV fluoro) positions. Results: With a sinusoidal trace, absolute errors of the 4DCT estimated markers positions vary between 0.78mm and 5.4mm and RMS errors are between 0.38mm to 1.7mm. With irregular patient traces, absolute errors of the 4DCT estimated markers positions increased significantly by 100 to 200 percent, while the corresponding RMS error values have much smaller changes. Significant mismatches were frequently found at peak-inhale or peak-exhale phase. Conclusion: As expected, under conditions of well-behaved, periodic sinusoidal motion, the 4DCT yielded much better estimation of marker positions. When an actual patient trace is used 4DCT-derived positions showed significant mismatches with the fluoroscopic trajectories, indicating the potential for geometric and therefore dosimetric errors in the presence of cycle-to-cycle respiratory variations.
NASA Astrophysics Data System (ADS)
Johnson, Tim; Versteeg, Roelof; Thomle, Jon; Hammond, Glenn; Chen, Xingyuan; Zachara, John
2015-08-01
This paper describes and demonstrates two methods of providing a priori information to the surface-based time-lapse three-dimensional electrical resistivity tomography (ERT) problem for monitoring stage-driven or tide-driven surface water intrusion into aquifers. First, a mesh boundary is implemented that conforms to the known location of the water table through time, thereby enabling the inversion to place a sharp bulk conductivity contrast at that boundary without penalty. Second, a nonlinear inequality constraint is used to allow only positive or negative transient changes in EC to occur within the saturated zone, dependent on the relative contrast in fluid electrical conductivity between surface water and groundwater. A 3-D field experiment demonstrates that time-lapse imaging results using traditional smoothness constraints are unable to delineate river water intrusion. The water table and inequality constraints provide the inversion with the additional information necessary to resolve the spatial extent of river water intrusion through time.
Black diamonds at brane junctions
NASA Astrophysics Data System (ADS)
Chamblin, Andrew; Csáki, Csaba; Erlich, Joshua; Hollowood, Timothy J.
2000-08-01
We discuss the properties of black holes in brane-world scenarios where our Universe is viewed as a four-dimensional sub-manifold of some higher-dimensional spacetime. We consider in detail such a model where four-dimensional spacetime lies at the junction of several domain walls in a higher dimensional anti-de Sitter spacetime. In this model there may be any number p of infinitely large extra dimensions transverse to the brane-world. We present an exact solution describing a black p-brane which will induce on the brane-world the Schwarzschild solution. This exact solution is unstable to the Gregory-Laflamme instability, whereby long-wavelength perturbations cause the extended horizon to fragment. We therefore argue that at late times a non-rotating uncharged black hole in the brane-world is described by a deformed event horizon in p+4 dimensions which will induce, to good approximation, the Schwarzschild solution in the four-dimensional brane world. When p=2, this deformed horizon resembles a black diamond and more generally for p>2, a polyhedron.
Black diamonds at brane junctions
Chamblin, Andrew; Csaki, Csaba; Erlich, Joshua; Hollowood, Timothy J.; Department of Physics, University of Wales Swansea, Swansea, SA2 8PP,
2000-08-15
We discuss the properties of black holes in brane-world scenarios where our Universe is viewed as a four-dimensional sub-manifold of some higher-dimensional spacetime. We consider in detail such a model where four-dimensional spacetime lies at the junction of several domain walls in a higher dimensional anti-de Sitter spacetime. In this model there may be any number p of infinitely large extra dimensions transverse to the brane-world. We present an exact solution describing a black p-brane which will induce on the brane-world the Schwarzschild solution. This exact solution is unstable to the Gregory-Laflamme instability, whereby long-wavelength perturbations cause the extended horizon to fragment. We therefore argue that at late times a non-rotating uncharged black hole in the brane-world is described by a deformed event horizon in p+4 dimensions which will induce, to good approximation, the Schwarzschild solution in the four-dimensional brane world. When p=2, this deformed horizon resembles a black diamond and more generally for p>2, a polyhedron. (c) 2000 The American Physical Society.
Phase topology of one irreducible integrable problem in the dynamics of a rigid body
NASA Astrophysics Data System (ADS)
Ryabov, P. E.
2013-08-01
We consider the integrable system with three degrees of freedom for which V. V. Sokolov and A. V. Tsiganov specified the Lax pair. The Lax representation generalizes the L-A pair found by A. G. Reyman and M. A. Semenov-Tian-Shansky for the Kovalevskaya gyrostat in a double field. We give explicit formulas for the additional first integrals K and G (independent almost everywhere), which are functionally related to the coefficients of the spectral curve for the Sokolov-Tsiganov L-A pair. Using this form of the additional integrals K and G and the Kharlamov parametric reduction, we analytically present two invariant four-dimensional submanifolds where the induced dynamical system is Hamiltonian (almost everywhere) with two degrees of freedom. The system of equations specifying one of the invariant submanifolds is a generalization of the invariant relations for the integrable Bogoyavlensky case (rotation of a magnetized rigid body in homogeneous gravitational and magnetic fields). We use the method of critical subsystems to describe the phase topology of the whole system. For each subsystem, we construct the bifurcation diagrams and specify the bifurcations of the Liouville tori both inside the subsystems and in the whole system.
World-volume effective theory for higher-dimensional black holes.
Emparan, Roberto; Harmark, Troels; Niarchos, Vasilis; Obers, Niels A
2009-05-15
We argue that the main feature behind novel properties of higher-dimensional black holes, compared to four-dimensional ones, is that their horizons can have two characteristic lengths of very different size. We develop a long-distance world-volume effective theory that captures the black hole dynamics at scales much larger than the short scale. In this limit the black hole is regarded as a blackfold: a black brane (possibly boosted locally) whose world volume spans a curved submanifold of the spacetime. This approach reveals black objects with novel horizon geometries and topologies more complex than the black ring, but more generally it provides a new organizing framework for the dynamics of higher-dimensional black holes. PMID:19518938
A Class of Dust-Like Self-Similar Solutions of the Massless Einstein-Vlasov System
NASA Astrophysics Data System (ADS)
Rendall, Alan D.; Velázquez, Juan J. L.
2011-07-01
In this paper the existence of a class of self-similar solutions of the Einstein-Vlasov system is proved. The initial data for these solutions are not smooth, with their particle density being supported in a submanifold of codimension one. They can be thought of as intermediate between smooth solutions of the Einstein-Vlasov system and dust. The motivation for studying them is to obtain insights into possible violation of weak cosmic censorship by solutions of the Einstein-Vlasov system. By assuming a suitable form of the unknowns it is shown that the existence question can be reduced to that of the existence of a certain type of solution of a four-dimensional system of ordinary differential equations depending on two parameters. This solution starts at a particular point $P_0$ and converges to a stationary solution $P_1$ as the independent variable tends to infinity. The existence proof is based on a shooting argument and involves relating the dynamics of solutions of the four-dimensional system to that of solutions of certain two- and three-dimensional systems obtained from it by limiting processes.
Harvey, R. W.; Petrov, Yu. V.
2013-12-03
Within the US Department of Energy/Office of Fusion Energy magnetic fusion research program, there is an important whole-plasma-modeling need for a radio-frequency/neutral-beam-injection (RF/NBI) transport-oriented finite-difference Fokker-Planck (FP) code with combined capabilities for 4D (2R2V) geometry near the fusion plasma periphery, and computationally less demanding 3D (1R2V) bounce-averaged capabilities for plasma in the core of fusion devices. Demonstration of proof-of-principle achievement of this goal has been carried out in research carried out under Phase I of the SBIR award. Two DOE-sponsored codes, the CQL3D bounce-average Fokker-Planck code in which CompX has specialized, and the COGENT 4D, plasma edge-oriented Fokker-Planck code which has been constructed by Lawrence Livermore National Laboratory and Lawrence Berkeley Laboratory scientists, where coupled. Coupling was achieved by using CQL3D calculated velocity distributions including an energetic tail resulting from NBI, as boundary conditions for the COGENT code over the two-dimensional velocity space on a spatial interface (flux) surface at a given radius near the plasma periphery. The finite-orbit-width fast ions from the CQL3D distributions penetrated into the peripheral plasma modeled by the COGENT code. This combined code demonstrates the feasibility of the proposed 3D/4D code. By combining these codes, the greatest computational efficiency is achieved subject to present modeling needs in toroidally symmetric magnetic fusion devices. The more efficient 3D code can be used in its regions of applicability, coupled to the more computationally demanding 4D code in higher collisionality edge plasma regions where that extended capability is necessary for accurate representation of the plasma. More efficient code leads to greater use and utility of the model. An ancillary aim of the project is to make the combined 3D/4D code user friendly. Achievement of full-coupling of these two Fokker-Planck codes will advance computational modeling of plasma devices important to the USDOE magnetic fusion energy program, in particular the DIII-D tokamak at General Atomics, San Diego, the NSTX spherical tokamak at Princeton, New Jersey, and the MST reversed-field-pinch Madison, Wisconsin. The validation studies of the code against the experiments will improve understanding of physics important for magnetic fusion, and will increase our design capabilities for achieving the goals of the International Tokamak Experimental Reactor (ITER) project in which the US is a participant and which seeks to demonstrate at least a factor of five in fusion power production divided by input power.
Ali, I; Ahmad, S; Alsbou, N
2015-06-15
Purpose: To develop 4D-cone-beam CT (CBCT) algorithm by motion modeling that extracts actual length, CT numbers level and motion amplitude of a mobile target retrospective to image reconstruction by motion modeling. Methods: The algorithm used three measurable parameters: apparent length and blurred CT number distribution of a mobile target obtained from CBCT images to determine actual length, CT-number value of the stationary target, and motion amplitude. The predictions of this algorithm were tested with mobile targets that with different well-known sizes made from tissue-equivalent gel which was inserted into a thorax phantom. The phantom moved sinusoidally in one-direction to simulate respiratory motion using eight amplitudes ranging 0–20mm. Results: Using this 4D-CBCT algorithm, three unknown parameters were extracted that include: length of the target, CT number level, speed or motion amplitude for the mobile targets retrospective to image reconstruction. The motion algorithms solved for the three unknown parameters using measurable apparent length, CT number level and gradient for a well-defined mobile target obtained from CBCT images. The motion model agreed with measured apparent lengths which were dependent on the actual target length and motion amplitude. The gradient of the CT number distribution of the mobile target is dependent on the stationary CT number level, actual target length and motion amplitude. Motion frequency and phase did not affect the elongation and CT number distribution of the mobile target and could not be determined. Conclusion: A 4D-CBCT motion algorithm was developed to extract three parameters that include actual length, CT number level and motion amplitude or speed of mobile targets directly from reconstructed CBCT images without prior knowledge of the stationary target parameters. This algorithm provides alternative to 4D-CBCT without requirement to motion tracking and sorting of the images into different breathing phases which has potential applications in diagnostic CT imaging and radiotherapy.
Yang Xiaocheng; Han-Oh, Sarah; Gui Minzhi; Niu Ying; Yu, Cedric X.; Yi Byongyong
2012-09-15
Purpose: Dose-rate-regulated tracking (DRRT) is a tumor tracking strategy that programs the MLC to track the tumor under regular breathing and adapts to breathing irregularities during delivery using dose rate regulation. Constant-dose-rate tracking (CDRT) is a strategy that dynamically repositions the beam to account for intrafractional 3D target motion according to real-time information of target location obtained from an independent position monitoring system. The purpose of this study is to illustrate the differences in the effectiveness and delivery accuracy between these two tracking methods in the presence of breathing irregularities. Methods: Step-and-shoot IMRT plans optimized at a reference phase were extended to remaining phases to generate 10-phased 4D-IMRT plans using segment aperture morphing (SAM) algorithm, where both tumor displacement and deformation were considered. A SAM-based 4D plan has been demonstrated to provide better plan quality than plans not considering target deformation. However, delivering such a plan requires preprogramming of the MLC aperture sequence. Deliveries of the 4D plans using DRRT and CDRT tracking approaches were simulated assuming the breathing period is either shorter or longer than the planning day, for 4 IMRT cases: two lung and two pancreatic cases with maximum GTV centroid motion greater than 1 cm were selected. In DRRT, dose rate was regulated to speed up or slow down delivery as needed such that each planned segment is delivered at the planned breathing phase. In CDRT, MLC is separately controlled to follow the tumor motion, but dose rate was kept constant. In addition to breathing period change, effect of breathing amplitude variation on target and critical tissue dose distribution is also evaluated. Results: Delivery of preprogrammed 4D plans by the CDRT method resulted in an average of 5% increase in target dose and noticeable increase in organs at risk (OAR) dose when patient breathing is either 10% faster or slower than the planning day. In contrast, DRRT method showed less than 1% reduction in target dose and no noticeable change in OAR dose under the same breathing period irregularities. When {+-}20% variation of target motion amplitude was present as breathing irregularity, the two delivery methods show compatible plan quality if the dose distribution of CDRT delivery is renormalized. Conclusions: Delivery of 4D-IMRT treatment plans, stemmed from 3D step-and-shoot IMRT and preprogrammed using SAM algorithm, is simulated for two dynamic MLC-based real-time tumor tracking strategies: with and without dose-rate regulation. Comparison of cumulative dose distribution indicates that the preprogrammed 4D plan is more accurately and efficiently conformed using the DRRT strategy, as it compensates the interplay between patient breathing irregularity and tracking delivery without compromising the segment-weight modulation.
Self-adjointness of the Fourier expansion of quantized interaction field Lagrangians
Paneitz, S. M.; Segal, I. E.
1983-01-01
Regularity properties significantly stronger than were previously known are developed for four-dimensional non-linear conformally invariant quantized fields. The Fourier coefficients of the interaction Lagrangian in the interaction representation—i.e., evaluated after substitution of the associated quantized free field—is a densely defined operator on the associated free field Hilbert space K. These Fourier coefficients are with respect to a natural basis in the universal cosmos ˜M, to which such fields canonically and maximally extend from Minkowski space-time M0, which is covariantly a submanifold of ˜M. However, conformally invariant free fields over M0 and ˜M are canonically identifiable. The kth Fourier coefficient of the interaction Lagrangian has domain inclusive of all vectors in K to which arbitrary powers of the free hamiltonian in ˜M are applicable. Its adjoint in the rigorous Hilbert space sense is a-k in the case of a hermitian Lagrangian. In particular (k = 0) the leading term in the perturbative expansion of the S-matrix for a conformally invariant quantized field in M0 is a self-adjoint operator. Thus, e.g., if ϕ(x) denotes the free massless neutral scalar field in M0, then ∫M0:ϕ(x)4:d4x is a self-adjoint operator. No coupling constant renormalization is involved here. PMID:16593346
Multiscale Geometry of the Olsen Model and Non-classical Relaxation Oscillations
NASA Astrophysics Data System (ADS)
Kuehn, Christian; Szmolyan, Peter
2015-06-01
We study the Olsen model for the peroxidase-oxidase reaction. The dynamics is analyzed using a geometric decomposition based on multiple timescales. The Olsen model is four-dimensional, not in a standard form required by geometric singular perturbation theory and contains multiple small parameters. These three obstacles are the main challenges we resolve by our analysis. Scaling and the blow-up method are used to identify several subsystems. The results presented here provide a rigorous analysis for two oscillatory modes. In particular, we prove the existence of non-classical relaxation oscillations in two cases. The analysis is based on desingularization of lines of transcritical and submanifolds of fold singularities in combination with an integrable relaxation phase. In this context, our analysis also explains an assumption that has been utilized, based purely on numerical reasoning, in a previous bifurcation analysis by Desroches et al. (Discret Contin Dyn Syst S 2(4):807-827, 2009). Furthermore, the geometric decomposition we develop forms the basis to prove the existence of mixed-mode and chaotic oscillations in the Olsen model, which will be discussed in more detail in future work.
NASA Astrophysics Data System (ADS)
Garrett, Daniel S.; Gronenborn, Angela M.; Marius Clore, G.
2011-12-01
The Contour Approach to Peak Picking was developed to aid in the analysis and interpretation and of multidimensional NMR spectra of large biomolecules. In essence, it comprises an interactive graphics software tool to computationally select resonance positions in heteronuclear, 3- and 4D spectra.
The geometry of electron wave functions
Aminov, Yurii A
2013-02-28
To each wave function we assign a codimension-two submanifold in Euclidean space. We study the case of the wave function of a single electron in the hydrogen atom or other hydrogen-type atoms with quantum numbers n, l, m in detail. We prove theorems describing the behaviour of the scalar and sectional curvature of the constructed submanifold, depending on the quantum numbers. We also consider the external geometry of the submanifold. Bibliography: 9 titles.
High speed infrared imaging system and method
Zehnder, Alan T.; Rosakis, Ares J.; Ravichandran, G.
2001-01-01
A system and method for radiation detection with an increased frame rate. A semi-parallel processing configuration is used to process a row or column of pixels in a focal-plane array in parallel to achieve a processing rate up to and greater than 1 million frames per second.
Numerical tools to validate stationary points of SO(8)-gauged N=8D=4 supergravity
NASA Astrophysics Data System (ADS)
Fischbacher, Thomas
2012-03-01
Until recently, the preferred strategy to identify stationary points in the scalar potential of SO(8)-gauged N=8 supergravity in D=4 has been to consider truncations of the potential to sub-manifolds of E/SU(8) that are invariant under some postulated residual gauge group G⊂SO(8). As powerful alternative strategies have been shown to exist that allow one to go far beyond what this method can achieve — and in particular have produced numerous solutions that break the SO(8) gauge group to no continuous residual symmetry — independent verification of results becomes a problem due to both the complexity of the scalar potential and the large number of new solutions. This article introduces a conceptually simple self-contained piece of computer code that allows independent numerical validation of claims on the locations of newly discovered stationary points. Program summaryProgram title: e7-vacua Catalogue identifier: AELB_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AELB_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.html No. of lines in distributed program, including test data, etc.: 4447 No. of bytes in distributed program, including test data, etc.: 281 689 Distribution format: tar.gz Programming language: Python Computer: Any Operating system: Unix/Linux RAM: 1 Giga-byte Classification: 1.5, 11.1 External routines: Scientific Python (SciPy) ( http://www.scipy.org/), NumPy ( http://numpy.scipy.org) Nature of problem: This code allows numerical validation of claims about the existence of critical points in the scalar potential of four-dimensional SO(8)-gauged N=8 supergravity. Solution method: Tensor algebra. Running time: Full analysis of a solution (including scalar mass matrices): about 15 minutes. Otherwise, about 1-2 minutes.
Design of a Low-Light-Level Image Sensor with On-Chip Sigma-Delta Analog-to- Digital Conversion
NASA Technical Reports Server (NTRS)
Mendis, Sunetra K.; Pain, Bedabrata; Nixon, Robert H.; Fossum, Eric R.
1993-01-01
The design and projected performance of a low-light-level active-pixel-sensor (APS) chip with semi-parallel analog-to-digital (A/D) conversion is presented. The individual elements have been fabricated and tested using MOSIS* 2 micrometer CMOS technology, although the integrated system has not yet been fabricated. The imager consists of a 128 x 128 array of active pixels at a 50 micrometer pitch. Each column of pixels shares a 10-bit A/D converter based on first-order oversampled sigma-delta (Sigma-Delta) modulation. The 10-bit outputs of each converter are multiplexed and read out through a single set of outputs. A semi-parallel architecture is chosen to achieve 30 frames/second operation even at low light levels. The sensor is designed for less than 12 e^- rms noise performance.
A new parallel simulation technique
NASA Astrophysics Data System (ADS)
Blanco-Pillado, Jose J.; Olum, Ken D.; Shlaer, Benjamin
2012-01-01
We develop a "semi-parallel" simulation technique suggested by Pretorius and Lehner, in which the simulation spacetime volume is divided into a large number of small 4-volumes that have only initial and final surfaces. Thus there is no two-way communication between processors, and the 4-volumes can be simulated independently and potentially at different times. This technique allows us to simulate much larger volumes than we otherwise could, because we are not limited by total memory size. No processor time is lost waiting for other processors. We compare a cosmic string simulation we developed using the semi-parallel technique with our previous MPI-based code for several test cases and find a factor of 2.6 improvement in the total amount of processor time required to accomplish the same job for strings evolving in the matter-dominated era.
Persistent homology analysis of phase transitions
NASA Astrophysics Data System (ADS)
Donato, Irene; Gori, Matteo; Pettini, Marco; Petri, Giovanni; De Nigris, Sarah; Franzosi, Roberto; Vaccarino, Francesco
2016-05-01
Persistent homology analysis, a recently developed computational method in algebraic topology, is applied to the study of the phase transitions undergone by the so-called mean-field XY model and by the ϕ4 lattice model, respectively. For both models the relationship between phase transitions and the topological properties of certain submanifolds of configuration space are exactly known. It turns out that these a priori known facts are clearly retrieved by persistent homology analysis of dynamically sampled submanifolds of configuration space.
Properties of a parameterization of radon projection by the reconstruction on circular disc
NASA Astrophysics Data System (ADS)
Tischenko, O.; Schegerer, A.; Xu, Y.; Hoeschen, C.
2010-04-01
An angular parameterization of parallel Radon projections referred to in this paper as ψ-parameterization is discussed in relevance to the efficiency of reconstruction from fan data. The fact that the ψ-parameterization coincides with the equiangular fan beam parameterization allows us to develop a simple and efficient approach useful for the reconstruction from fan data. Within this approach parallel projections are approximated by groups of semi-parallel rays. The reconstruction is carried out directly, i.e. without any modification of original data, at the speed which is comparable or even higher than that of the parallel Filtered Back Projection (FBP) algorithm.
Extendability of parallel sections in vector bundles
NASA Astrophysics Data System (ADS)
Kirschner, Tim
2016-01-01
I address the following question: Given a differentiable manifold M, what are the open subsets U of M such that, for all vector bundles E over M and all linear connections ∇ on E, any ∇-parallel section in E defined on U extends to a ∇-parallel section in E defined on M? For simply connected manifolds M (among others) I describe the entirety of all such sets U which are, in addition, the complement of a C1 submanifold, boundary allowed, of M. This delivers a partial positive answer to a problem posed by Antonio J. Di Scala and Gianni Manno (2014). Furthermore, in case M is an open submanifold of Rn, n ≥ 2, I prove that the complement of U in M, not required to be a submanifold now, can have arbitrarily large n-dimensional Lebesgue measure.
String fluid in local equilibrium
NASA Astrophysics Data System (ADS)
Schubring, Daniel; Vanchurin, Vitaly
2014-10-01
We study the solutions of string fluid equations under the assumption of a local equilibrium which was previously obtained in the context of the kinetic theory. We show that the fluid can be foliated into noninteracting submanifolds whose equations of motion are exactly that of the wiggly strings considered previously by Vilenkin and Carter. In a special case of negligible statistical variance in either the left- or the right-moving directions of microscopic strings, the submanifolds are described by the action of a null-current-carrying chiral string. When both variances vanish the submanifolds are described by the Nambu-Goto action and the string fluid reduces to the string dust introduced by Stachel.
Curvature and geometric modules of noncommutative spheres and tori
Arnlind, Joakim
2014-04-15
When considered as submanifolds of Euclidean space, the Riemannian geometry of the round sphere and the Clifford torus may be formulated in terms of Poisson algebraic expressions involving the embedding coordinates, and a central object is the projection operator, projecting tangent vectors in the ambient space onto the tangent space of the submanifold. In this note, we point out that there exist noncommutative analogues of these projection operators, which implies a very natural definition of noncommutative tangent spaces as particular projective modules. These modules carry an induced connection from Euclidean space, and we compute its scalar curvature.
Curvature and geometric modules of noncommutative spheres and tori
NASA Astrophysics Data System (ADS)
Arnlind, Joakim
2014-04-01
When considered as submanifolds of Euclidean space, the Riemannian geometry of the round sphere and the Clifford torus may be formulated in terms of Poisson algebraic expressions involving the embedding coordinates, and a central object is the projection operator, projecting tangent vectors in the ambient space onto the tangent space of the submanifold. In this note, we point out that there exist noncommutative analogues of these projection operators, which implies a very natural definition of noncommutative tangent spaces as particular projective modules. These modules carry an induced connection from Euclidean space, and we compute its scalar curvature.
Anti-holomorphic involutive isometry of hyper-Kähler manifolds and branes
NASA Astrophysics Data System (ADS)
Biswas, Indranil; Wilkin, Graeme
2015-02-01
We study complex Lagrangian submanifolds of a compact hyper-Kähler manifold and prove two results: (a) that an involution of a hyper-Kähler manifold which is antiholomorphic with respect to one complex structure and which acts non-trivially on the corresponding symplectic form always has a fixed point locus which is complex Lagrangian with respect to one of the other complex structures, and (b) there exist Lagrangian submanifolds which are complex with respect to one complex structure and are not the fixed point locus of any involution which is anti-holomorphic with respect to one of the other complex structures.
Hidden symmetry of hyperbolic monopole motion
NASA Astrophysics Data System (ADS)
Gibbons, G. W.; Warnick, C. M.
2007-10-01
Hyperbolic monopole motion is studied for well separated monopoles. It is shown that the motion of a hyperbolic monopole in the presence of one or more fixed monopoles is equivalent to geodesic motion on a particular submanifold of the full moduli space. The metric on this submanifold is found to be a generalisation of the multi-centre Taub-NUT metric introduced by LeBrun. The one centre case is analysed in detail as a special case of a class of systems admitting a conserved Runge-Lenz vector. The two centre problem is also considered. An integrable classical string motion is exhibited.
Nonmaximality of known extremal metrics on torus and Klein bottle
Karpukhin, M A
2013-12-31
The El Soufi-Ilias theorem establishes a connection between minimal submanifolds of spheres and extremal metrics for eigenvalues of the Laplace-Beltrami operator. Recently, this connection was used to provide several explicit examples of extremal metrics. We investigate the properties of these metrics and prove that none of them is maximal. Bibliography: 24 titles.
A quantum modification of relative cohomology
NASA Astrophysics Data System (ADS)
Zhang, Dong; Chen, Bohui; Du, Cheng-Yong
2015-12-01
In this paper, we give a quantum modification of the relative cup product on H*(X, S;ℝ) by using Gromov-Witten invariants when S is a compact codimension 2k symplectic submanifold of the compact symplectic manifold (X, ω).
Concentration of Laplace Eigenfunctions and Stabilization of Weakly Damped Wave Equation
NASA Astrophysics Data System (ADS)
Burq, N.; Zuily, C.
2016-08-01
In this article, we prove some universal bounds on the speed of concentration on small (frequency-dependent) neighbourhoods of sub-manifolds of L 2-norms of quasi modes for Laplace operators on compact manifolds. We deduce new results on the rate of decay of weakly damped wave equations.
NASA Astrophysics Data System (ADS)
Erkekog˜lu, Fazilet
2016-02-01
This is a survey of the principal results about the geodesic completeness of nondegenerate hypersurfaces in Lorentzian manifolds from a structural point of view. Some of these results retain their validity in the case of semi-Riemannian submanifolds in semi-Euclidean spaces, as well.
Separation of variables for some systems with a fourth-order integral of motion
NASA Astrophysics Data System (ADS)
Grigoryev, Yu. A.; Khudobakhshov, V. A.; Tsiganov, A. V.
2013-12-01
We construct separation variables for Yehia's integrable deformations of the Kovalevskaya top and the Chaplygin system on a sphere. In the general case, the corresponding quadratures are given by the Abel-Jacobi map on a two-dimensional submanifold of the Jacobian of a genus-three algebraic curve, which is not hyperelliptic.
Klimov, V S
2001-02-28
A version of the Poincare-Hopf theorem is established for multivalued vector fields on submanifolds of a reflexive space. The connection between the critical values and homological characteristics of the Lebesgue sets of Lipschitz functionals is studied. Applications to the theory of operator inclusions with parameters are indicated.
A new generic approach for optoelectronic hardware realizations of neural networks models
Agranat, A.; Neugebauer, C.F.; Yariv, A.
1988-09-01
A new generic approach for realizing neural networks (NN) is presented. The underlying principle of the new approach is to take advantage of the fact that signal processing in silicon is an advanced and mature technology, and to incorporate optics where silicon fails, namely in the interconnectivity problem. The basic idea is described. The system consists of two main subassemblies: a 2D Spatial Light Modulator (SLM) and an integrated circuit to which the authors shall henceforth refer to as the Neural Processor (NP). The synaptic efficacies matrix W is stored in the SLM. Thus by imaging the SLM contents onto an array detector which serves as the input unit of the NP, W is loaded in parallel into the NP. The NP then updates the state of the network in parallel/semiparallel-synchronous/asynchronous manner (depending on the structure of the NP).
Active-Pixel Image Sensor With Analog-To-Digital Converters
NASA Technical Reports Server (NTRS)
Fossum, Eric R.; Mendis, Sunetra K.; Pain, Bedabrata; Nixon, Robert H.
1995-01-01
Proposed single-chip integrated-circuit image sensor contains 128 x 128 array of active pixel sensors at 50-micrometer pitch. Output terminals of all pixels in each given column connected to analog-to-digital (A/D) converter located at bottom of column. Pixels scanned in semiparallel fashion, one row at time; during time allocated to scanning row, outputs of all active pixel sensors in row fed to respective A/D converters. Design of chip based on complementary metal oxide semiconductor (CMOS) technology, and individual circuit elements fabricated according to 2-micrometer CMOS design rules. Active pixel sensors designed to operate at video rate of 30 frames/second, even at low light levels. A/D scheme based on first-order Sigma-Delta modulation.
Graphics Processing Unit Enhanced Parallel Document Flocking Clustering
Cui, Xiaohui; Potok, Thomas E; ST Charles, Jesse Lee
2010-01-01
Analyzing and clustering documents is a complex problem. One explored method of solving this problem borrows from nature, imitating the flocking behavior of birds. One limitation of this method of document clustering is its complexity O(n2). As the number of documents grows, it becomes increasingly difficult to generate results in a reasonable amount of time. In the last few years, the graphics processing unit (GPU) has received attention for its ability to solve highly-parallel and semi-parallel problems much faster than the traditional sequential processor. In this paper, we have conducted research to exploit this archi- tecture and apply its strengths to the flocking based document clustering problem. Using the CUDA platform from NVIDIA, we developed a doc- ument flocking implementation to be run on the NVIDIA GEFORCE GPU. Performance gains ranged from thirty-six to nearly sixty times improvement of the GPU over the CPU implementation.
The Use of Computational Diagrams and Nomograms in Higher Education.
ERIC Educational Resources Information Center
Brandenburg, Richard K.; Simpson, William A.
1984-01-01
The use of computational diagrams and nomographs for the calculations that frequently occur in college administration is examined. Steps in constructing a nomograph and a four-dimensional computational diagram are detailed, and uses of three- and four-dimensional diagrams are covered. Diagrams and nomographs are useful in the following cases: (1)…
ERIC Educational Resources Information Center
Kwon, Hyungil Harry; Pyun, Do Young; Han, Siwan; Ogasawara, Etsuko
2011-01-01
The objective of this study was to provide empirical evidence to support psychometric properties of a modified four-dimensional model of the Leadership Scale for Sports (LSS). The study tested invariance of all parameters (i.e., factor loadings, error variances, and factor variances-covariances) in the four-dimensional measurement model between…
On Energy-Momentum Transfer of Quantum Fields
NASA Astrophysics Data System (ADS)
Herdegen, Andrzej
2014-10-01
We prove the following theorem on bounded operators in quantum field theory: if , then , where D( x) is a function weakly decaying in spacelike directions, are creation/annihilation parts of an appropriate time derivative of B, G is any positive, bounded, non-increasing function in , and is any finite complex Borel measure; creation/annihilation operators may be also replaced by with . We also use the notion of energy-momentum scaling degree of B with respect to a submanifold (Steinmann-type, but in momentum space, and applied to the norm of an operator). These two tools are applied to the analysis of singularities of . We prove, among others, the following statement (modulo some more specific assumptions): outside p = 0 the only allowed contributions to this functional which are concentrated on a submanifold (including the trivial one—a single point) are Dirac measures on hypersurfaces (if the decay of D is not to slow).
Numerical integration of ordinary differential equations on manifolds
NASA Astrophysics Data System (ADS)
Crouch, P. E.; Grossman, R.
1993-12-01
This paper is concerned with the problem of developing numerical integration algorithms for differential equations that, when viewed as equations in some Euclidean space, naturally evolve on some embedded submanifold. It is desired to construct algorithms whose iterates also evolve on the same manifold. These algorithms can therefore be viewed as integrating ordinary differential equations on manifolds. The basic method “decouples” the computation of flows on the submanifold from the numerical integration process. It is shown that two classes of single-step and multistep algorithms can be posed and analyzed theoretically, using the concept of “freezing” the coefficients of differential operators obtained from the defining vector field. Explicit third-order algorithms are derived, with additional equations augmenting those of their classical counterparts, obtained from “obstructions” defined by nonvanishing Lie brackets.
Exact moduli space metrics for hyperbolic vortex polygons
Krusch, S.; Speight, J. M.
2010-02-15
Exact metrics on some totally geodesic submanifolds of the moduli space of static hyperbolic N-vortices are derived. These submanifolds, denoted as {sigma}{sub n,m}, are spaces of C{sub n}-invariant vortex configurations with n single vortices at the vertices of a regular polygon and m=N-n coincident vortices at the polygon's center. The geometric properties of {sigma}{sub n,m} are investigated, and it is found that {sigma}{sub n,n-1} is isometric to the hyperbolic plane of curvature -(3{pi}n){sup -1}. The geodesic flow on {sigma}{sub n,m} and a geometrically natural variant of geodesic flow recently proposed by Collie and Tong ['The dynamics of Chern-Simons vortices', Phys. Rev. D Part. Fields Gravit. Cosmol. 78, 065013 (2008);e-print arXiv:hep-th/0805.0602] are analyzed in detail.
Domain structure of black hole space-times
Harmark, Troels
2009-07-15
We introduce the domain structure for stationary black hole space-times. The domain structure lives on the submanifold of fixed points of the Killing vector fields. Depending on which Killing vector field has fixed points the submanifold is naturally divided into domains. The domain structure provides invariants of the space-time, both topological and continuous. It is defined for any space-time dimension and any number of Killing vector fields. We examine the domain structure for asymptotically flat space-times and find a canonical form for the metric of such space-times. The domain structure generalizes the rod structure introduced for space-times with D-2 commuting Killing vector fields. We analyze in detail the domain structure for Minkowski space, the Schwarzschild-Tangherlini black hole and the Myers-Perry black hole in six and seven dimensions. Finally, we consider the possible domain structures for asymptotically flat black holes in six and seven dimensio0008.
Invariants from classical field theory
Diaz, Rafael; Leal, Lorenzo
2008-06-15
We introduce a method that generates invariant functions from perturbative classical field theories depending on external parameters. By applying our methods to several field theories such as Abelian BF, Chern-Simons, and two-dimensional Yang-Mills theory, we obtain, respectively, the linking number for embedded submanifolds in compact varieties, the Gauss' and the second Milnor's invariant for links in S{sup 3}, and invariants under area-preserving diffeomorphisms for configurations of immersed planar curves.
Internal or shape coordinates in the {ital n}-body problem
Littlejohn, R.G.; Reinsch, M.
1995-09-01
The construction of global shape coordinates for the {ital n}-body problem is considered. Special attention is given to the three- and four-body problems. Quantities, including candidates for coordinates, are organized according to their transformation properties under so-called democracy transformations (orthogonal transformations of Jacobi vectors). Important submanifolds of shape space are identified and their topology studied, including the manifolds upon which shapes are coplanar or collinear, and the manifolds upon which the moment of inertia tensor is degenerate.
NASA Astrophysics Data System (ADS)
Stepanov, Sergey E.; Jukl, Marek; Mikeš, Josef
2014-03-01
Conformal Killing forms are a natural generalization of conformal Killing vector fields. These forms have applications in physics related to hidden symmetries, conserved quantities, symmetry operators, or separation of variables. In this paper, we prove two vanishing theorems of conformal Killing forms on a space-like totally umbilical submanifold of a Lorentzian manifold. Finally, we show an application of these results to electrodynamics in the General Relativity Theory.
Covariant hyperbolization of force-free electrodynamics
NASA Astrophysics Data System (ADS)
Carrasco, F. L.; Reula, O. A.
2016-04-01
Force-free electrodynamics (FFE) is a nonlinear system of equations modeling the evolution of the electromagnetic field, in the presence of a magnetically dominated relativistic plasma. This configuration arises on several astrophysical scenarios which represent exciting laboratories to understand physics in extreme regimes. We show that this system, when restricted to the correct constraint submanifold, is symmetric hyperbolic. In numerical applications, it is not feasible to keep the system in that submanifold, and so it is necessary to analyze its structure first in the tangent space of that submanifold and then in a whole neighborhood of it. As has been shown [1], a direct (or naive) formulation of this system (in the whole tangent space) results in a weakly hyperbolic system of evolution equations for which well-posedness for the initial value formulation does not follow. Using the generalized symmetric hyperbolic formalism of Geroch [2], we introduce here a covariant hyperbolization for the FFE system. In fact, in analogy to the usual Maxwell case, a complete family of hyperbolizers is found, both for the restricted system on the constraint submanifold as well as for a suitably extended system defined in a whole neighborhood of it. A particular symmetrizer among the family is then used to write down the pertaining evolution equations, in a generic (3 +1 ) decomposition on a background spacetime. Interestingly, it turns out that for a particular choice of the lapse and shift functions of the foliation, our symmetrized system reduces to the one found in [1]. Finally, we analyze the characteristic structure of the resulting evolution system.
NASA Astrophysics Data System (ADS)
Bonatti, Ch.; Díaz, L. J.
We study diffeomorphisms f with heterodimensional cycles, that is, heteroclinic cycles associated to saddles p and q with different indices. Such a cycle is called fragile if there is no diffeomorphism close to f with a robust cycle associated to hyperbolic sets containing the continuations of p and q. We construct a codimension one submanifold of Diff(S×S) that consists of diffeomorphisms with fragile heterodimensional cycles. Our construction holds for any manifold of dimension ⩾4.
Integrable systems of partial differential equations determined by structure equations and Lax pair
NASA Astrophysics Data System (ADS)
Bracken, Paul
2010-01-01
It is shown how a system of evolution equations can be developed both from the structure equations of a submanifold embedded in three-space as well as from a matrix SO(6) Lax pair. The two systems obtained this way correspond exactly when a constraint equation is selected and imposed on the system of equations. This allows for the possibility of selecting the coefficients in the second fundamental form in a general way.
Adaptive unsupervised slow feature analysis for feature extraction
NASA Astrophysics Data System (ADS)
Gu, Xingjian; Liu, Chuancai; Wang, Sheng
2015-03-01
Slow feature analysis (SFA) extracts slowly varying features out of the input data and has been successfully applied on pattern recognition. However, SFA heavily relies on the constructed time series when SFA is applied on databases that neither have obvious temporal structure nor have label information. Traditional SFA constructs time series based on k-nearest neighborhood (k-NN) criterion. Specifically, the time series set constructed by k-NN criterion is likely to include noisy time series or lose suitable time series because the parameter k is difficult to determine. To overcome these problems, a method called adaptive unsupervised slow feature analysis (AUSFA) is proposed. First, AUSFA designs an adaptive criterion to generate time series for characterizing submanifold. The constructed time series have two properties: (1) two points of time series lie on the same submanifold and (2) the submanifold of the time series is smooth. Second, AUSFA seeks projections that simultaneously minimize the slowness scatter and maximize the fastness scatter to extract slow discriminant features. Extensive experimental results on three benchmark face databases demonstrate the effectiveness of our proposed method.
On gauge enhancement and singular limits in G 2 compactifications of M-theory
NASA Astrophysics Data System (ADS)
Halverson, James; Morrison, David R.
2016-04-01
We study the physics of singular limits of G 2 compactifications of M-theory, which are necessary to obtain a compactification with non-abelian gauge symmetry or massless charged particles. This is more difficult than for Calabi-Yau compactifications, due to the absence of calibrated two-cycles that would have allowed for direct control of W-boson masses as a function of moduli. Instead, we study the relationship between gauge enhancement and singular limits in G 2 moduli space where an associative or coassociative submanifold shrinks to zero size; this involves the physics of topological defects and sometimes gives indirect control over particle masses, even though they are not BPS. We show how a lemma of Joyce associates the class of a three-cycle to any U(1) gauge theory in a smooth G 2 compactification. If there is an appropriate associative submanifold in this class then in the limit of nonabelian gauge symmetry it may be interpreted as a gauge theory worldvolume and provides the location of the singularities associated with non-abelian gauge or matter fields. We identify a number of gauge enhancement scenarios related to calibrated submanifolds, including Coulomb branches and non-isolated conifolds, and also study examples that realize them.
Time and dark matter from the conformal symmetries of Euclidean space
NASA Astrophysics Data System (ADS)
Hazboun, Jeffrey S.; Wheeler, James T.
2014-11-01
Starting with the conformal symmetries of Euclidean space, we construct a manifold where time manifests as a part of the geometry. Though there is no matter present in the geometry studied here, geometric terms analogous to dark energy and dark matter appear when we write down the Einstein tensor. Specifically, the quotient of the conformal group of Euclidean four-space by its Weyl subgroup results in a geometry possessing many of the properties of relativistic phase space, including both a natural symplectic form and non-degenerate Killing metric. We show that the general solution posesses orthogonal Lagrangian submanifolds, with the induced metric and the spin connection on the submanifolds necessarily Lorentzian, despite the Euclidean starting point. Using an orthonormal frame adapted to the phase space properties, we also find two new tensor fields not present in Riemannian geometry. The first is a combination of the Weyl vector with the scale factor on the metric, and determines the timelike directions on the submanifolds. The second comes from the components of the spin connection, symmetric with respect to the new metric. Though this field comes from the spin connection, it transforms homogeneously. Finally, we show that in the absence of Cartan curvature and sources, the configuration space has geometric terms equivalent to a perfect fluid and a cosmological constant.
Is the Higgs boson a sign of extra dimensions?
NASA Astrophysics Data System (ADS)
So, Hiroto; Takenaga, Kazunori
2013-07-01
We introduce a four-dimensional cutoff in the scenario of gauge-Higgs unification to control the ultraviolet behavior. A one-loop effective potential for a Higgs field and the Higgs mass are obtained with the cutoff. We find an interrelation between the four-dimensional cutoff and the scale of extra dimensions, which is concretized through the Higgs mass. Combining this interrelation and the recently discovered Higgs boson at the LHC, we obtain an interesting constraint for the four-dimensional cutoff and the extra-dimensional scale.
A six-dimensional (Z2)3 symmetric model with warped physical space
NASA Astrophysics Data System (ADS)
Sahabandu, Chetiya; Suranyi, Peter; Rohana Wijewardhana, L. C.; Vaz, Cenalo
2008-08-01
The Randall-Sundrum model is studied in six dimension with AdS4 or dS4 metric in the physical four-dimensional space. Two solutions are found, one with induced five-dimensional gravity terms added to the induced cosmological constant terms. We study the graviton modes in both solutions by transforming the mass eigenvalue equation to a Schrodinger equation with a volcano potential. The spectrum of gravitational excitations depends on the input parameters of the theory, the six-dimensional and the effective four-dimensional cosmological constants. The model gives a physically acceptable spectrum if the four-dimensional cosmological constant is sufficiently small.
Annual review of biophysics and biophysical chemistry. Volume 20, 1991
Engelman, D.M. ); Cantor, C.R. ); Pollard, T.D. . School of Medicine)
1991-01-01
This book covers: statistical methods and insights for protein and DNA sequences; the biochemistry of genetic recombination; and two- three- and four-dimensional NMR methods for obtaining 3-D structures of proteins in solution; as well as other topics.
Diffraction and pulse slippage in the Boeing 1 kW FEL oscillator
Blau, J.; Wong, R.K.; Colson, W.B.
1995-12-31
A four-dimensional simulation in x, y, z, and t, including betatron motion of the electrons, is used to study the combined effects of diffraction, pulse slippage and desynchronism in the Boeing 1 kW FEL oscillator.
Table-lookup algorithm for pattern recognition: ELLTAB (Elliptical Table)
NASA Technical Reports Server (NTRS)
Jones, W. C., III; Eppler, W. G.
1975-01-01
Remotely sensed unit is assigned to category by merely looking up its channel readings in four-dimensional table. Approach makes it possible to process multispectral scanner data using a minicomputer.
Poisson structures for lifts and periodic reductions of integrable lattice equations
NASA Astrophysics Data System (ADS)
Kouloukas, Theodoros E.; Tran, Dinh T.
2015-02-01
We introduce and study suitable Poisson structures for four-dimensional maps derived as lifts and specific periodic reductions of integrable lattice equations. These maps are Poisson with respect to these structures and the corresponding integrals are in involution.
NASA Astrophysics Data System (ADS)
Essén, Hanno; Nordmark, Arne B.
2016-09-01
The canonical Poisson bracket algebra of four-dimensional relativistic mechanics is used to derive the equation of motion for a charged particle, with the Lorentz force, and the homogeneous Maxwell equations.
Escape to a New Dimension: A Journey through Space with a Square, a Cube, and a Tesseract
ERIC Educational Resources Information Center
Camp, Dane R.
2006-01-01
This article, a play designed around an imaginary conversation between geometric objects, summarizes various approaches to visualizing a tesseract (a.k.a. hypercube--a four-dimensional analog of a cube).
Note on cosmological Levi-Civita spacetimes in higher dimensions
Sarioglu, Oezguer; Tekin, Bayram
2009-04-15
We find a class of solutions to cosmological Einstein equations that generalizes the four dimensional cylindrically symmetric spacetimes to higher dimensions. The AdS soliton is a special member of this class with a unique singularity structure.
A Lorentz covariant holoraumy-induced "gadget" from minimal off-shell 4D, N=1 supermultiplets
NASA Astrophysics Data System (ADS)
Gates, S. James; Grover, Tyler; Miller-Dickson, Miles David; Mondal, Benedict A.; Oskoui, Amir; Regmi, Shirash; Ross, Ethan; Shetty, Rajath
2015-11-01
Starting from three minimal off-shell 4D, N=1 supermultiplets, using constructions solely defined within the confines of the four dimensional field theory we show the existence of a "gadget" — a member of a class of metrics on the representation space of the supermultiplets — whose values directly and completely correspond to the values of a metric defined on the 1d, N = 4 adinkra networks adjacency matrices corresponding to the projections of the four dimensional supermultiplets.
Effects of Strings in Inflation and Reheating
NASA Astrophysics Data System (ADS)
Frey, Andrew R.
We argue that many models of inflation in string theory require the usual ten-dimensional compactification geometry to be modified during inflation. Based on arguments from the four-dimensional effective theory, we propose a modified ten-dimensional geometry in which the four-dimensional effective theory is just consistent. We also discuss the implications of the light modes in reheating, following inflation. (Based on work in progress with Anupam Mazumdar and Robert Myers.)
Cosmological string solutions by dimensional reduction
Behrndt, K.; Foerste, S.
1993-12-01
We obtain cosmological four dimensional solutions of the low energy effective string theory by reducing a five dimensional black hole, and black hole-de Sitter solution of the Einstein gravity down to four dimensions. The appearance of a cosmological constant in the five dimensional Einstein-Hilbert produces a special dilaton potential in the four dimensional effective string action. Cosmological scenarios implement by our solutions are discussed.
Introduction to Causal Dynamical Triangulations
NASA Astrophysics Data System (ADS)
Görlich, Andrzej
The method of causal dynamical triangulations is a non-perturbative and background-independent approach to quantum theory of gravity. In this review we present recent results obtained within the four dimensional model of causal dynamical triangulations. We describe the phase structure of the model and demonstrate how a macroscopic four-dimensional de Sitter universe emerges dynamically from the full gravitational path integral. We show how to reconstruct the effective action describing scale factor fluctuations from Monte Carlo data.
NASA Astrophysics Data System (ADS)
Hazboun, Jeffrey Shafiq
2014-10-01
Cartan geometry provides a rich formalism from which to look at various geometrically motivated extensions to general relativity. In this manuscript, we start by motivating reasons to extend the theory of general relativity. We then introduce the reader to our technique, called the quotient manifold method, for extending the geometry of spacetime. We will specifically look at the class of theories formed from the various quotients of the conformal group. Starting with the conformal symmetries of Euclidean space, we construct a manifold where time manifests as a part of the geometry. Though there is no matter present in the geome- try studied here, geometric terms analogous to dark energy and dark matter appear when we write down the Einstein tensor. Specifically, the quotient of the conformal group of Euclidean four-space by its Weyl subgroup results in a geometry possessing many of the properties of relativistic phase space, including both a natural symplectic form and nondegenerate Killing metric. We show the general solution possesses orthogonal Lagrangian submanifolds, with the induced metric and the spin connection on the submanifolds necessarily Lorentzian, despite the Euclidean starting point. By examining the structure equations of the biconformal space in an orthonormal frame adapted to its phase space properties, we also find two new tensor fields exist in this geometry, not present in Riemannian geometry. The first is a combination of the Weyl vector with the scale factor on the metric, and determines the time-like directions on the submanifolds. The second comes from the components of the spin connection, symmetric with respect to the new metric. Though this field comes from the spin connection, it transforms ho- mogeneously. Finally, we show in the absence of Cartan curvature or sources, the configuration space has geometric terms equivalent to a perfect fluid and a cosmological constant. We complete the analysis of this homogeneous space by
Arjhangmehr, A.; Feghhi, S. A. H.
2016-01-01
Understanding radiation performance of nanocrystalline Zr-based alloys is essential to develop internal components and external cladding materials with self-healing capabilities for longer and safer life cycles in harsh reactor environments. However, the precise role of interfaces in modifying defect production and evolution in α-Zr is not yet determined. Using atomistic simulation methods, we investigate the influence of different atomic grain boundaries (GBs) in thermodynamic and kinetic properties of defects on short timescales. We observe that the sink efficiency and sink strength of interfaces vary significantly with the boundary structures, with a preference to absorb interstitials (vacancies) when the GBs are semi-parallel (semi-perpendicular) relative to the basal planes. Further, we identify three distinct primary cascade geometries, and find that the residual defect clustering in grain interiors depends on how the atomic GBs modify the spatial distribution of defects within the crystal structure. Finally, we explain and discuss the dynamic results in terms of energetic and kinetic behaviors of defects near the pristine and damaged boundaries. Eventually, these will provide a microscopic reference for further improving the radiation response of Zr by using fine grains or by introducing a high density of dispersoids in material metallurgy. PMID:27004606
High-performance monolithic CMOS detectors for space applications
NASA Astrophysics Data System (ADS)
Saint-Pe, Olivier; Tulet, Michel; Davancens, Robert; Larnaudie, Franck; Vignon, Bruno; Magnan, Pierre; Farre, Jean A.; Corbiere, Franck; Martin-Gonthier, Philippe
2001-12-01
During the last 10 years, research about CMOS image sensors (also called APS - Active Pixel Sensors) has been intensively carried out, in order to offer an alternative to CCDs as image sensors. This is particularly the case for space applications as CMOS image sensors feature characteristics which are obviously of interest for flight hardware: parallel or semi-parallel architecture, on chip control and processing electronics, low power dissipation, high level of radiation tolerance... Many image sensor companies, institutes and laboratories have demonstrated the compatibility of CMOS image sensors with consumer applications: micro-cameras, video-conferencing, digital- still cameras. And recent designs have shown that APS is getting closer to the CCD in terms of performance level. However, he large majority of the existing products do not offer the specific features which are required for many space applications. ASTRIUM and SUPAERO/CIMI have decided to work together in view of developing CMOS image sensors dedicated to space business. After a brief presentation of the team organization for space image sensor design and production, the latest results of a high performances 512 X 512 pixels CMOS device characterization are presented with emphasis on the achieved electro-optical performance. Finally, the on going and short-term coming activities of the team are discussed.
Communication library for run-time visualization of distributed, asynchronous data
Rowlan, J.; Wightman, B.T.
1994-04-01
In this paper we present a method for collecting and visualizing data generated by a parallel computational simulation during run time. Data distributed across multiple processes is sent across parallel communication lines to a remote workstation, which sorts and queues the data for visualization. We have implemented our method in a set of tools called PORTAL (for Parallel aRchitecture data-TrAnsfer Library). The tools comprise generic routines for sending data from a parallel program (callable from either C or FORTRAN), a semi-parallel communication scheme currently built upon Unix Sockets, and a real-time connection to the scientific visualization program AVS. Our method is most valuable when used to examine large datasets that can be efficiently generated and do not need to be stored on disk. The PORTAL source libraries, detailed documentation, and a working example can be obtained by anonymous ftp from info.mcs.anl.gov from the file portal.tar.Z from the directory pub/portal.
Geology of the undeveloped oil and gas fields of Central Offshore Santa Maria Basin, California
Milton, J.D. ); Edwards, E.B. ); Heck, R.G. )
1996-01-01
Two prominent subsurface structural features of the Central Offshore Santa Maria Basin are the Hosgri fault system and the associated anticlinal fold trend. Exploratory drilling and 3D seismic mapping have delineated a series of oil and gas fields along this trend which underlie four federal units and one non-unitized lease. The units are named after local geography and are called the Lion Rock, Point Sal, Purisima Point and Santa Maria Units. The individual lease, OCS P-0409, overlies the San Miguel field. The Hosgri fault system trends northwest-southeast and effectively forms the eastern boundary of the oil and gas province. Lying semi-parallel with the fault are several anticlinal culminations which have trapped large volumes of oil and gas in the fractured Montery Formation. The Monterey is both source and reservoir rock, averaging 300 meters n thickness throughout the Central Basin. Development of the Monterey Formation as a reservoir rock was through diagensis and tectonism with resulting porosities-from 15 to 20% and permeability up to one Darcy. These parameters coupled with a high geothermal gradient facilitate the inflow rates of the viscous Monterey oil. Some 24 exploration and delineation wells have been drilled in this area and tested at rates ranging from a few hundred to several thousand barrels per day. Estimated oil reserves in the Central Offshore Santa Maria Basin total approximately 1 billion barrels.
Geology of the undeveloped oil and gas fields of Central Offshore Santa Maria Basin, California
Milton, J.D.; Edwards, E.B.; Heck, R.G.
1996-12-31
Two prominent subsurface structural features of the Central Offshore Santa Maria Basin are the Hosgri fault system and the associated anticlinal fold trend. Exploratory drilling and 3D seismic mapping have delineated a series of oil and gas fields along this trend which underlie four federal units and one non-unitized lease. The units are named after local geography and are called the Lion Rock, Point Sal, Purisima Point and Santa Maria Units. The individual lease, OCS P-0409, overlies the San Miguel field. The Hosgri fault system trends northwest-southeast and effectively forms the eastern boundary of the oil and gas province. Lying semi-parallel with the fault are several anticlinal culminations which have trapped large volumes of oil and gas in the fractured Montery Formation. The Monterey is both source and reservoir rock, averaging 300 meters n thickness throughout the Central Basin. Development of the Monterey Formation as a reservoir rock was through diagensis and tectonism with resulting porosities-from 15 to 20% and permeability up to one Darcy. These parameters coupled with a high geothermal gradient facilitate the inflow rates of the viscous Monterey oil. Some 24 exploration and delineation wells have been drilled in this area and tested at rates ranging from a few hundred to several thousand barrels per day. Estimated oil reserves in the Central Offshore Santa Maria Basin total approximately 1 billion barrels.
Protected air-cooled condenser for the Clinch River Breeder Reactor Plant
Louison, R.; Boardman, C.E.
1981-05-29
The long term residual heat removal for the Clinch River Breeder Reactor Plant (CRBRP) is accomplished through the use of three protected air-cooled condensers (PACC's) each rated at 15M/sub t/ following a normal or emergency shutdown of the reactor. Steam is condensed by forcing air over the finned and coiled condenser tubes located above the steam drums. The steam flow is by natural convection. It is drawn to the PACC tube bundle for the steam drum by the lower pressure region in the tube bundle created from the condensing action. The concept of the tube bundle employs a unique patented configuration which has been commercially available through CONSECO Inc. of Medfore, Wisconsin. The concept provides semi-parallel flow that minimizes subcooling and reduces steam/condensate flow instabilities that have been observed on other similar heat transfer equipment such as moisture separator reheaters (MSRS). The improved flow stability will reduce temperature cycling and associated mechanical fatigue. The PACC is being designed to operate during and following the design basis earthquake, depressurization from the design basis tornado and is housed in protective building enclosure which is also designed to withstand the above mentioned events.
NASA Astrophysics Data System (ADS)
Arjhangmehr, A.; Feghhi, S. A. H.
2016-03-01
Understanding radiation performance of nanocrystalline Zr-based alloys is essential to develop internal components and external cladding materials with self-healing capabilities for longer and safer life cycles in harsh reactor environments. However, the precise role of interfaces in modifying defect production and evolution in α-Zr is not yet determined. Using atomistic simulation methods, we investigate the influence of different atomic grain boundaries (GBs) in thermodynamic and kinetic properties of defects on short timescales. We observe that the sink efficiency and sink strength of interfaces vary significantly with the boundary structures, with a preference to absorb interstitials (vacancies) when the GBs are semi-parallel (semi-perpendicular) relative to the basal planes. Further, we identify three distinct primary cascade geometries, and find that the residual defect clustering in grain interiors depends on how the atomic GBs modify the spatial distribution of defects within the crystal structure. Finally, we explain and discuss the dynamic results in terms of energetic and kinetic behaviors of defects near the pristine and damaged boundaries. Eventually, these will provide a microscopic reference for further improving the radiation response of Zr by using fine grains or by introducing a high density of dispersoids in material metallurgy.
Arjhangmehr, A; Feghhi, S A H
2016-01-01
Understanding radiation performance of nanocrystalline Zr-based alloys is essential to develop internal components and external cladding materials with self-healing capabilities for longer and safer life cycles in harsh reactor environments. However, the precise role of interfaces in modifying defect production and evolution in α-Zr is not yet determined. Using atomistic simulation methods, we investigate the influence of different atomic grain boundaries (GBs) in thermodynamic and kinetic properties of defects on short timescales. We observe that the sink efficiency and sink strength of interfaces vary significantly with the boundary structures, with a preference to absorb interstitials (vacancies) when the GBs are semi-parallel (semi-perpendicular) relative to the basal planes. Further, we identify three distinct primary cascade geometries, and find that the residual defect clustering in grain interiors depends on how the atomic GBs modify the spatial distribution of defects within the crystal structure. Finally, we explain and discuss the dynamic results in terms of energetic and kinetic behaviors of defects near the pristine and damaged boundaries. Eventually, these will provide a microscopic reference for further improving the radiation response of Zr by using fine grains or by introducing a high density of dispersoids in material metallurgy. PMID:27004606
Spatial and Lorentzian surfaces in Robertson-Walker space times
NASA Astrophysics Data System (ADS)
Chen, Bang-Yen; Van der Veken, Joeri
2007-07-01
Let L14(f,c)=(I×fS,gfc) be a Robertson-Walker space time which does not contain any open subset of constant curvature. In this paper, we provide a general study of nondegenerate surfaces in L14(f,c). First, we prove the nonexistence of marginally trapped surfaces with positive relative nullity. Then, we classify totally geodesic submanifolds. Finally, we classify the family of surfaces with parallel second fundamental form and the family of totally umbilical surfaces with parallel mean curvature vector.
Canonical deformations of surfaces of equilibrium states in thermodynamic phase space
Jurkowski
2000-08-01
Deformations of submanifolds of thermodynamic equilibrium states introduced by continuous contact maps on a phase-space manifold are considered in terms of the geometrical formulation of thermodynamics. The notion of a contact Hamiltonian is recalled in order to give some possible physical interpretations of such a function in terms of statistical quantities describing initial and deformed systems. Using contact flows we propose a very efficient method for constructing continuous families of thermodynamic systems. A few examples show the possible advantages of using contact Hamiltonians. PMID:11088641
NASA Astrophysics Data System (ADS)
Arzano, Michele; Kowalski-Glikman, Jerzy
2016-09-01
We construct discrete symmetry transformations for deformed relativistic kinematics based on group valued momenta. We focus on the specific example of κ-deformations of the Poincaré algebra with associated momenta living on (a sub-manifold of) de Sitter space. Our approach relies on the description of quantum states constructed from deformed kinematics and the observable charges associated with them. The results we present provide the first step towards the analysis of experimental bounds on the deformation parameter κ to be derived via precision measurements of discrete symmetries and CPT.
A numerical method for finding sign-changing solutions of superlinear Dirichlet problems
Neuberger, J.M.
1996-12-31
In a recent result it was shown via a variational argument that a class of superlinear elliptic boundary value problems has at least three nontrivial solutions, a pair of one sign and one which sign changes exactly once. These three and all other nontrivial solutions are saddle points of an action functional, and are characterized as local minima of that functional restricted to a codimension one submanifold of the Hilbert space H-0-1-2, or an appropriate higher codimension subset of that manifold. In this paper, we present a numerical Sobolev steepest descent algorithm for finding these three solutions.
NASA Astrophysics Data System (ADS)
Raza, Muhammad; Myrzakulov, Kairat; Momeni, Davood; Myrzakulov, Ratbay
2016-05-01
In this paper,we investigate the mathematical modeling for the cosmological attractors propagated in mimetic gravity upon which an interacting dark energy-dark matter is supposed to be existed. The average value of the interaction of these percentages, namely Γ i say, may be used to investigate generally the modeling of an attractor; the actual value could only be determined by data in any particular case. We have seen, for example, that it was led to investigate the subject of initially invariant submanifolds.
Hamiltonian dynamics of the parametrized electromagnetic field
NASA Astrophysics Data System (ADS)
Barbero G, J. Fernando; Margalef-Bentabol, Juan; Villaseñor, Eduardo J. S.
2016-06-01
We study the Hamiltonian formulation for a parametrized electromagnetic field with the purpose of clarifying the interplay between parametrization and gauge symmetries. We use a geometric approach which is tailor-made for theories where embeddings are part of the dynamical variables. Our point of view is global and coordinate free. The most important result of the paper is the identification of sectors in the primary constraint submanifold in the phase space of the model where the number of independent components of the Hamiltonian vector fields that define the dynamics changes. This explains the non-trivial behavior of the system and some of its pathologies.
Stability of Fermi surfaces and K theory.
Horava, Petr
2005-07-01
Nonrelativistic Fermi liquids in d+1 dimensions exhibit generalized Fermi surfaces: (d-p)-dimensional submanifolds in the (k,omega)-space supporting gapless excitations. We show that the universality classes of stable Fermi surfaces are classified by K theory, with the pattern of stability determined by Bott periodicity. The Atiyah-Bott-Shapiro construction implies that the low-energy modes near a Fermi surface exhibit relativistic invariance in the transverse p+1 dimensions. This suggests an intriguing parallel between nonrelativistic Fermi liquids and D-branes of string theory. PMID:16090638
NASA Astrophysics Data System (ADS)
Bracken, Paul
2010-04-01
A system of evolution equations can be developed from the structure equations for a submanifold embedded in a three-dimensional space. It is seen how these same equations can be obtained from a generalized matrix Lax pair provided a single constraint equation is imposed. This can be done in Euclidean space as well as in Minkowski space. The integrable systems which result from this process can be thought of as generalizing the SO(3) and SO(2,1) Lax pairs which have been studied previously.
A Heisenberg Algebra Bundle of a Vector Field in Three-Space and its Weyl Quantization
Binz, Ernst; Pods, Sonja
2006-01-04
In these notes we associate a natural Heisenberg group bundle Ha with a singularity free smooth vector field X = (id,a) on a submanifold M in a Euclidean three-space. This bundle yields naturally an infinite dimensional Heisenberg group H{sub X}{sup {infinity}}. A representation of the C*-group algebra of H{sub X}{sup {infinity}} is a quantization. It causes a natural Weyl-deformation quantization of X. The influence of the topological structure of M on this quantization is encoded in the Chern class of a canonical complex line bundle inside Ha.
Gravity, two times, tractors, Weyl invariance, and six-dimensional quantum mechanics
Bonezzi, R.; Latini, E.; Waldron, A.
2010-09-15
Fefferman and Graham showed some time ago that four-dimensional conformal geometries could be analyzed in terms of six-dimensional, ambient, Riemannian geometries admitting a closed homothety. Recently, it was shown how conformal geometry provides a description of physics manifestly invariant under local choices of unit systems. Strikingly, Einstein's equations are then equivalent to the existence of a parallel scale tractor (a six-component vector subject to a certain first order covariant constancy condition at every point in four-dimensional spacetime). These results suggest a six-dimensional description of four-dimensional physics, a viewpoint promulgated by the 2 times physics program of Bars. The Fefferman-Graham construction relies on a triplet of operators corresponding, respectively, to a curved six-dimensional light cone, the dilation generator and the Laplacian. These form an sp(2) algebra which Bars employs as a first class algebra of constraints in a six-dimensional gauge theory. In this article four-dimensional gravity is recast in terms of six-dimensional quantum mechanics by melding the 2 times and tractor approaches. This parent formulation of gravity is built from an infinite set of six-dimensional fields. Successively integrating out these fields yields various novel descriptions of gravity including a new four-dimensional one built from a scalar doublet, a tractor-vector multiplet and a conformal class of metrics.
Davis, M. J.; Tomlin, A. S.; Chemical Sciences and Engineering Division; Univ. of Leeds
2008-08-28
The spatial dynamics of steady, one-dimensional premixed H{sub 2}/O{sub 2} flames are studied. The emphasis in this Article is the geometry of the phase space of the dynamical system describing the steady flames. It is shown that steady flames are described by trajectories on the stable manifolds of saddle fixed points. The saddle fixed points correspond to equilibrium points of time-dependent chemical-kinetic systems that are adiabatic and isobaric and whose constant enthalpy matches the asymptotic enthalpy of the flames. The dimensions of the stable manifolds match the dimensions of the chemical-kinetic systems under most conditions, although the dynamics on them are different. It is further shown that the stable manifolds have low-dimensional attractive submanifolds near the saddlepoint. An algorithm for generating trajectories over the spatial domain of these flames is proposed, and it is used to study individual trajectories and trajectory ensembles, whose collective behavior suggests that there are low-dimensional submanifolds away from the saddlepoint.
Spectrum of quantum transfer matrices via classical many-body systems
NASA Astrophysics Data System (ADS)
Gorsky, A.; Zabrodin, A.; Zotov, A.
2014-01-01
In this paper we clarify the relationship between inhomogeneous quantum spin chains and classical integrable many-body systems. It provides an alternative (to the nested Bethe ansatz) method for computation of spectra of the spin chains. Namely, the spectrum of the quantum transfer matrix for the inhomogeneous n -invariant XXX spin chain on N sites with twisted boundary conditions can be found in terms of velocities of particles in the rational N -body Ruijsenaars-Schneider model. The possible values of the velocities are to be found from intersection points of two Lagrangian submanifolds in the phase space of the classical model. One of them is the Lagrangian hyperplane corresponding to fixed coordinates of all N particles and the other one is an N -dimensional Lagrangian submanifold obtained by fixing levels of N classical Hamiltonians in involution. The latter are determined by eigenvalues of the twist matrix. To support this picture, we give a direct proof that the eigenvalues of the Lax matrix for the classical Ruijsenaars-Schneider model, where velocities of particles are substituted by eigenvalues of the spin chain Hamiltonians, calculated through the Bethe equations, coincide with eigenvalues of the twist matrix, with certain multiplicities. We also prove a similar statement for the n Gaudin model with N marked points (on the quantum side) and the Calogero-Moser system with N particles (on the classical side). The realization of the results obtained in terms of branes and supersymmetric gauge theories is also discussed.
Multi-stream portrait of the Cosmic web
NASA Astrophysics Data System (ADS)
Ramachandra, Nesar; Shandarin, Sergei
2016-03-01
We report the results of the first study of the multi-stream environment of dark matter haloes in cosmological N-body simulations in the ΛCDM cosmology. The full dynamical state of dark matter can be described as a three-dimensional sub-manifold in six-dimensional phase space - the dark matter sheet. In our study we use a Lagrangian sub-manifold x = x (q , t) (where x and q are co-moving Eulerian and Lagrangian coordinates respectively), which is dynamically equivalent to the dark matter sheet but is more convenient for numerical analysis. Our major results can be summarized as follows. At the resolution of the simulation, the cosmic web represents a hierarchical structure: each halo is embedded in the filamentary framework of the web predominantly at the filament crossings, and each filament is embedded in the wall like fabric of the web at the wall crossings. Locally, each halo or sub-halo is a peak in the number of streams field. The number of streams in the neighbouring filaments is higher than in the neighbouring walls. The walls are regions where number of streams is equal to three or a few. Voids are uniquely defined by the local condition requiring to be a single-stream flow region.
Model reduction by manifold boundaries.
Transtrum, Mark K; Qiu, Peng
2014-08-29
Understanding the collective behavior of complex systems from their basic components is a difficult yet fundamental problem in science. Existing model reduction techniques are either applicable under limited circumstances or produce "black boxes" disconnected from the microscopic physics. We propose a new approach by translating the model reduction problem for an arbitrary statistical model into a geometric problem of constructing a low-dimensional, submanifold approximation to a high-dimensional manifold. When models are overly complex, we use the observation that the model manifold is bounded with a hierarchy of widths and propose using the boundaries as submanifold approximations. We refer to this approach as the manifold boundary approximation method. We apply this method to several models, including a sum of exponentials, a dynamical systems model of protein signaling, and a generalized Ising model. By focusing on parameters rather than physical degrees of freedom, the approach unifies many other model reduction techniques, such as singular limits, equilibrium approximations, and the renormalization group, while expanding the domain of tractable models. The method produces a series of approximations that decrease the complexity of the model and reveal how microscopic parameters are systematically "compressed" into a few macroscopic degrees of freedom, effectively building a bridge between the microscopic and the macroscopic descriptions. PMID:25216014
Human pose tracking from monocular video by traversing an image motion mapped body pose manifold
NASA Astrophysics Data System (ADS)
Basu, Saurav; Poulin, Joshua; Acton, Scott T.
2010-01-01
Tracking human pose from monocular video sequences is a challenging problem due to the large number of independent parameters affecting image appearance and nonlinear relationships between generating parameters and the resultant images. Unlike the current practice of fitting interpolation functions to point correspondences between underlying pose parameters and image appearance, we exploit the relationship between pose parameters and image motion flow vectors in a physically meaningful way. Change in image appearance due to pose change is realized as navigating a low dimensional submanifold of the infinite dimensional Lie group of diffeomorphisms of the two dimensional sphere S2. For small changes in pose, image motion flow vectors lie on the tangent space of the submanifold. Any observed image motion flow vector field is decomposed into the basis motion vector flow fields on the tangent space and combination weights are used to update corresponding pose changes in the different dimensions of the pose parameter space. Image motion flow vectors are largely invariant to style changes in experiments with synthetic and real data where the subjects exhibit variation in appearance and clothing. The experiments demonstrate the robustness of our method (within +/-4° of ground truth) to style variance.
Wilson lines and Chern-Simons flux in explicit heterotic Calabi-Yau compactifications
NASA Astrophysics Data System (ADS)
Apruzzi, Fabio; Gautason, Fridrik Freyr; Parameswaran, Susha; Zagermann, Marco
2015-02-01
We study to what extent Wilson lines in heterotic Calabi-Yau compactifications lead to non-trivial H-flux via Chern-Simons terms. Wilson lines are basic ingredients for Standard Model constructions but their induced H-flux may affect the consistency of the leading order background geometry and of the two-dimensional worldsheet theory. Moreover H-flux in heterotic compactifications would play an important role for moduli stabilization and could strongly constrain the supersymmetry breaking scale. We show how to compute H-flux and the corresponding superpotential, given an explicit complete intersection Calabi-Yau compactification and choice of Wilson lines. We do so by identifying large classes of special Lagrangian submanifolds in the Calabi-Yau, understanding how the Wilson lines project onto these submanifolds, and computing their Chern-Simons invariants. We illustrate our procedure with the quintic hypersurface as well as the split-bicubic, which can provide a potentially realistic three generation model.
Model Reduction by Manifold Boundaries
Transtrum, Mark K.; Qiu, Peng
2015-01-01
Understanding the collective behavior of complex systems from their basic components is a difficult yet fundamental problem in science. Existing model reduction techniques are either applicable under limited circumstances or produce “black boxes” disconnected from the microscopic physics. We propose a new approach by translating the model reduction problem for an arbitrary statistical model into a geometric problem of constructing a low-dimensional, submanifold approximation to a high-dimensional manifold. When models are overly complex, we use the observation that the model manifold is bounded with a hierarchy of widths and propose using the boundaries as submanifold approximations. We refer to this approach as the manifold boundary approximation method. We apply this method to several models, including a sum of exponentials, a dynamical systems model of protein signaling, and a generalized Ising model. By focusing on parameters rather than physical degrees of freedom, the approach unifies many other model reduction techniques, such as singular limits, equilibrium approximations, and the renormalization group, while expanding the domain of tractable models. The method produces a series of approximations that decrease the complexity of the model and reveal how microscopic parameters are systematically “compressed” into a few macroscopic degrees of freedom, effectively building a bridge between the microscopic and the macroscopic descriptions. PMID:25216014
Relativistic Euler's three-body problem, optical geometry, and the golden ratio
NASA Astrophysics Data System (ADS)
Coelho, Flávio S.; Herdeiro, Carlos A. R.
2009-11-01
A Weyl solution describing two Schwarzschild black holes is considered. We focus on the Z2 invariant solution, with Arnowitt-Deser-Misner mass MADM=2MK, where MK is the Komar mass of each black hole. For this solution the set of fixed points of the discrete symmetry is a totally geodesic submanifold. The existence and radii of circular photon orbits in this submanifold are studied, as functions of the distance 2L between the two black holes. For L→0 there are two such orbits, corresponding to r=3MADM and r=2MADM in Schwarzschild coordinates. As the distance increases, it is shown that the two photon orbits approach one another and merge when MK=φL, where φ is the golden ratio. Beyond this distance there exist no circular photon orbits. The two null orbits delimit a forbidden band for timelike circular orbits, which is interpreted in terms of optical geometry. For large L, timelike circular orbits are allowed everywhere, as in the analogous Newtonian problem. The analysis is generalized by considering a Z2 invariant Weyl solution with an array of N black holes and also by charging the black holes, which connects the Weyl solution to a Majumdar-Papapetrou spacetime.
Solution of a braneworld big crunch/big bang cosmology
McFadden, Paul L.; Turok, Neil; Steinhardt, Paul J.
2007-11-15
We solve for the cosmological perturbations in a five-dimensional background consisting of two separating or colliding boundary branes, as an expansion in the collision speed V divided by the speed of light c. Our solution permits a detailed check of the validity of four-dimensional effective theory in the vicinity of the event corresponding to the big crunch/big bang singularity. We show that the four-dimensional description fails at the first nontrivial order in (V/c){sup 2}. At this order, there is nontrivial mixing of the two relevant four-dimensional perturbation modes (the growing and decaying modes) as the boundary branes move from the narrowly separated limit described by Kaluza-Klein theory to the well-separated limit where gravity is confined to the positive-tension brane. We comment on the cosmological significance of the result and compute other quantities of interest in five-dimensional cosmological scenarios.
Cosmological and wormhole solutions in low-energy effective string theory
Cadoni, M. INFN, Sezione di Cagliari, Via Ada Negri 18, I---09127 Cagliari ); Cavaglia, M. INFN, Sezione di Cagliari, Via Ada Negri 18, I-09127 Cagliari )
1994-11-15
We derive and study a class of cosmological and wormhole solutions of low-energy effective string field theory. We consider a general four-dimensional string effective action where moduli of the compactified manifold and the electromagnetic field are present. The cosmological solutions of the two-dimensional effective theory obtained by dimensional reduction of the former are discussed. In particular we demonstrate that the two-dimensional theory possesses a scale-factor duality invariance. Eucidean four-dimensional instantons describing the nucleation of the baby universes are found and the probability amplitude for the nucleation process given.
Gravity and antigravity in a brane world with metastable gravitons
NASA Astrophysics Data System (ADS)
Gregory, R.; Rubakov, V. A.; Sibiryakov, S. M.
2000-09-01
In the framework of a five-dimensional three-brane model with quasi-localized gravitons we evaluate metric perturbations induced on the positive tension brane by matter residing thereon. We find that at intermediate distances, the effective four-dimensional theory coincides, up to small corrections, with General Relativity. This is in accord with Csaki, Erlich and Hollowood and in contrast to Dvali, Gabadadze and Porrati. We show, however, that at ultra-large distances this effective four-dimensional theory becomes dramatically different: conventional tensor gravity changes into scalar anti-gravity.
Abelian tensor hierarchy in 4D, N = 1 superspace
NASA Astrophysics Data System (ADS)
Becker, Katrin; Becker, Melanie; Linch, William D.; Robbins, Daniel
2016-03-01
With the goal of constructing the supersymmetric action for all fields, massless and massive, obtained by Kaluza-Klein compactification from type II theory or M-theory in a closed form, we embed the (Abelian) tensor hierarchy of p-forms in four-dimensional, N =1superspaceandconstructitsChern-Simons-likeinvariants. Whenspecializedtothe case in which the tensors arise from a higher-dimensional theory, the invariants may be interpreted as higher-dimensional Chern-Simons forms reduced to four dimensions. As an application of the formalism, we construct the eleven-dimensional Chern-Simons form in terms of four-dimensional, N = 1 superfields.
The edge of supersymmetry: Stability walls in heterotic theory
Anderson, Lara B.; Gray, James; Lukas, Andre; Ovrut, Burt
2009-05-15
We explicitly describe, in the language of four-dimensional N = 1 supersymmetric field theory, what happens when the moduli of a heterotic Calabi-Yau compactification change so as to make the internal non-Abelian gauge fields non-supersymmetric. At the edge of the region in Kähler moduli space where supersymmetry can be preserved, an additional anomalous U(1) gauge symmetry appears in the four-dimensional theory. The D-term contribution to the scalar potential associated to this U(1) attempts to force the system back into a supersymmetric configuration and provides a consistent low-energy description of gauge bundle stability.
Entropy of 4D extremal black holes
NASA Astrophysics Data System (ADS)
Johnson, Clifford V.; Khuri, Ramzi R.; Myers, Robert C.
1996-02-01
We derive the Bekenstein-Hawking entropy formula for four-dimensional Reissner-Nordström extremal black holes in type II string theory. The derivation is performed in two separate (T-dual) weak coupling pictures. One uses a type IIB bound state problem of D5- and D1-branes, while the other uses a bound state problem of D0- and D4-branes with macroscopic fundamental type IIA strings. In both cases, the D-brane systems are also bound to a Kaluza-Klein monopole, which then yields the four-dimensional black hole at strong coupling.
Dilatation symmetry in higher dimensions and the vanishing of the cosmological constant.
Wetterich, C
2009-04-10
A wide class of dilatation symmetric effective actions in higher dimensions leads to a vanishing four-dimensional cosmological constant. This requires no tuning of parameters and results from the absence of an allowed potential for the scalar dilaton field. The field equations admit many solutions with flat four-dimensional space and nonvanishing gauge couplings. In a more general setting, these are candidates for asymptotic states of cosmological runaway solutions, where dilatation symmetry is realized dynamically if a fixed point is approached as time goes to infinity. Dilatation anomalies during the runaway can lift the degeneracy of solutions and lead to an observable dynamical dark energy. PMID:19392424
Ghezelbash, A. M.
2010-02-15
We construct nonstationary exact solutions to five-dimensional Einstein-Maxwell-Chern-Simons theory with positive cosmological constant. The solutions are based on four-dimensional Atiyah-Hitchin space. In asymptotic regions, the solutions approach Gibbons-Perry-Sorkin monopole solutions. On the other hand, near the four-dimensional bolt of Atiyah-Hitchin space, our solutions show a bolt structure in five dimensions. The c function for the solutions shows monotonic increase in time, in agreement with the general expected behavior of the c function in asymptotically de Sitter spacetimes.
NASA Astrophysics Data System (ADS)
Stange, Kurt Martin; van Balen, Ronald; Vandenberghe, Jef; Peña, Jose Luis; Sancho, Carlos
2013-08-01
Focusing on climatic- and structural (tectonic) controls, we aim to determine their relative importance for the (Pliocene to Quaternary) fluvial landscape evolution in the Southern Pyrenees foreland. We investigate the Segre River, which is one of the major streams of the Southern Pyrenees that drains the elevated chain towards the Ebro foreland basin. Along its course, the Segre River has a flight of fluvial cut-and-fill (and strath-type) terraces preserved that have been mapped based on DEM's and geomorphological fieldwork. This paper presents the first results of our study and reports on the Segre terrace staircase, which is characterized by seven major Quaternary terrace levels with elevations up to more than 110 m above the modern floodplain. At the upper and middle reaches, the semi-parallel terraces of the Segre River occasionally show anomalies featuring extensive gravel thickness and deformation caused by faulting, folding and local subsidence. The longitudinal correlations of terrace levels reveal increased vertical terrace spacing in the foreland, which could originate from enhanced fluvial erosion after the Mid-Pleistocene climate transition in combination with base level lowering controlled by the progressive downcutting of the Catalan Coastal Range. Since the Ebro Basin opening (Late Miocene), the Catalan Coastal Range, which borders the Ebro foreland basin to the Mediterranean Sea, was progressively cut down and the exorheic drainage system gradually adjusted to sea level. The Segre longitudinal terrace profiles and the Ebro gorge morphology at the Catalan Coastal Range indicate a base-level of about 200 m.s.l. at the beginning of (Pleistocene) terrace formation, which implies that the Catalan Coastal Range might have functioned as a local base-level upstream of the sea outlet, presumably until the Late Pleistocene. Alternatively, a yet unknown tectonic process might have caused base level lowering and the preservation of terrace staircases at the
Merriam, D.F.
2005-01-01
Plains-type folds are local, subtle anticlines formed in the thin sedimentary package overlying a shallow, crystalline basement on the craton. They are small in areal extent (usually less than 1-3 km 2 [0.4-1.2 mi2]), and their amplitude increases with depth (usually tens of meters), which is mainly the result of differential compaction of sediments (usually clastic units) over tilted, rigid, basement fault blocks. The development of these structural features by continuous but intermittent movement of the basement fault blocks in the late Paleozoic in the United States mid-continent is substantiated by a record of stratigraphic and sedimentological evidence. The recurrent structural movement, which reflects adjustment to external stresses, is expressed by the change in thickness of stratigraphic units over the crest of the fold compared to the flanks. By plotting the change in thickness for different stratigraphic units of anticlines on different fault blocks, it is possible to determine the timing of movement of the blocks that reflect structural adjustment. These readjustments are confirmed by sedimentological evidence, such as convolute, soft-sediment deformation features and small intraformational faults. The stratigraphic interval change in thickness for numerous structures in the Cherokee, Forest City, and Salina basins and on the Nemaha anticline of the mid-continent United States was determined and compared for location and timing of the adjustments. Most of the adjustment occurred during and after time of deposition of the Permian-Pennsylvanian clastic units, which, in turn, reflect tectonic disturbance in adjacent areas, and the largest amount of movement on the plains-type structures occurred on those nearest and semiparallel to major positive features, such as the Nemaha anticline. Depending on the time of origin and development of plains-type folds, they may control the entrapment and occurrence of oil and gas. Copyright ??2005. The American
FLOCKING-BASED DOCUMENT CLUSTERING ON THE GRAPHICS PROCESSING UNIT [Book Chapter
Charles, J S; Patton, R M; Potok, T E; Cui, X
2008-01-01
Analyzing and grouping documents by content is a complex problem. One explored method of solving this problem borrows from nature, imitating the fl ocking behavior of birds. Each bird represents a single document and fl ies toward other documents that are similar to it. One limitation of this method of document clustering is its complexity O(n2). As the number of documents grows, it becomes increasingly diffi cult to receive results in a reasonable amount of time. However, fl ocking behavior, along with most naturally inspired algorithms such as ant colony optimization and particle swarm optimization, are highly parallel and have experienced improved performance on expensive cluster computers. In the last few years, the graphics processing unit (GPU) has received attention for its ability to solve highly-parallel and semi-parallel problems much faster than the traditional sequential processor. Some applications see a huge increase in performance on this new platform. The cost of these high-performance devices is also marginal when compared with the price of cluster machines. In this paper, we have conducted research to exploit this architecture and apply its strengths to the document flocking problem. Our results highlight the potential benefi t the GPU brings to all naturally inspired algorithms. Using the CUDA platform from NVIDIA®, we developed a document fl ocking implementation to be run on the NVIDIA® GEFORCE 8800. Additionally, we developed a similar but sequential implementation of the same algorithm to be run on a desktop CPU. We tested the performance of each on groups of news articles ranging in size from 200 to 3,000 documents. The results of these tests were very signifi cant. Performance gains ranged from three to nearly fi ve times improvement of the GPU over the CPU implementation. This dramatic improvement in runtime makes the GPU a potentially revolutionary platform for document clustering algorithms.
Khan, Shadab; Manwaring, Preston; Borsic, Andrea; Halter, Ryan
2015-04-01
Electrical impedance tomography (EIT) is used to image the electrical property distribution of a tissue under test. An EIT system comprises complex hardware and software modules, which are typically designed for a specific application. Upgrading these modules is a time-consuming process, and requires rigorous testing to ensure proper functioning of new modules with the existing ones. To this end, we developed a modular and reconfigurable data acquisition (DAQ) system using National Instruments' (NI) hardware and software modules, which offer inherent compatibility over generations of hardware and software revisions. The system can be configured to use up to 32-channels. This EIT system can be used to interchangeably apply current or voltage signal, and measure the tissue response in a semi-parallel fashion. A novel signal averaging algorithm, and 512-point fast Fourier transform (FFT) computation block was implemented on the FPGA. FFT output bins were classified as signal or noise. Signal bins constitute a tissue's response to a pure or mixed tone signal. Signal bins' data can be used for traditional applications, as well as synchronous frequency-difference imaging. Noise bins were used to compute noise power on the FPGA. Noise power represents a metric of signal quality, and can be used to ensure proper tissue-electrode contact. Allocation of these computationally expensive tasks to the FPGA reduced the required bandwidth between PC, and the FPGA for high frame rate EIT. In 16-channel configuration, with a signal-averaging factor of 8, the DAQ frame rate at 100 kHz exceeded 110 frames s (-1), and signal-to-noise ratio exceeded 90 dB across the spectrum. Reciprocity error was found to be for frequencies up to 1 MHz. Static imaging experiments were performed on a high-conductivity inclusion placed in a saline filled tank; the inclusion was clearly localized in the reconstructions obtained for both absolute current and voltage mode data. PMID:25376037
STUDY OF TWO SUCCESSIVE THREE-RIBBON SOLAR FLARES ON 2012 JULY 6
Wang, Haimin; Liu, Chang; Deng, Na; Xu, Yan; Jing, Ju; Zeng, Zhicheng; Cao, Wenda
2014-01-20
This Letter reports two rarely observed three-ribbon flares (M1.9 and C9.2) on 2012 July 6 in NOAA AR 11515, which we found using Hα observations of 0.''1 resolution from the New Solar Telescope and Ca II H images from Hinode. The flaring site is characterized by an intriguing ''fish-bone-like'' morphology evidenced by both Hα images and a nonlinear force-free field (NLFFF) extrapolation, where two semi-parallel rows of low-lying, sheared loops connect an elongated, parasitic negative field with the sandwiching positive fields. The NLFFF model also shows that the two rows of loops are asymmetric in height and have opposite twists, and are enveloped by large-scale field lines including open fields. The two flares occurred in succession within half an hour and are located at the two ends of the flaring region. The three ribbons of each flare run parallel to the magnetic polarity inversion line, with the outer two lying in the positive field and the central one in the negative field. Both flares show surge-like flows in Hα apparently toward the remote region, while the C9.2 flare is also accompanied by EUV jets possibly along the open field lines. Interestingly, the 12-25 keV hard X-ray sources of the C9.2 flare first line up with the central ribbon then shift to concentrate on the top of the higher branch of loops. These results are discussed in favor of reconnection along the coronal null line, producing the three flare ribbons and the associated ejections.
Flocking-based Document Clustering on the Graphics Processing Unit
Cui, Xiaohui; Potok, Thomas E; Patton, Robert M; ST Charles, Jesse Lee
2008-01-01
Abstract?Analyzing and grouping documents by content is a complex problem. One explored method of solving this problem borrows from nature, imitating the flocking behavior of birds. Each bird represents a single document and flies toward other documents that are similar to it. One limitation of this method of document clustering is its complexity O(n2). As the number of documents grows, it becomes increasingly difficult to receive results in a reasonable amount of time. However, flocking behavior, along with most naturally inspired algorithms such as ant colony optimization and particle swarm optimization, are highly parallel and have found increased performance on expensive cluster computers. In the last few years, the graphics processing unit (GPU) has received attention for its ability to solve highly-parallel and semi-parallel problems much faster than the traditional sequential processor. Some applications see a huge increase in performance on this new platform. The cost of these high-performance devices is also marginal when compared with the price of cluster machines. In this paper, we have conducted research to exploit this architecture and apply its strengths to the document flocking problem. Our results highlight the potential benefit the GPU brings to all naturally inspired algorithms. Using the CUDA platform from NIVIDA? we developed a document flocking implementation to be run on the NIVIDA?GEFORCE 8800. Additionally, we developed a similar but sequential implementation of the same algorithm to be run on a desktop CPU. We tested the performance of each on groups of news articles ranging in size from 200 to 3000 documents. The results of these tests were very significant. Performance gains ranged from three to nearly five times improvement of the GPU over the CPU implementation. This dramatic improvement in runtime makes the GPU a potentially revolutionary platform for document clustering algorithms.
Einstein-Yang-Mills theory: Asymptotic symmetries
NASA Astrophysics Data System (ADS)
Barnich, Glenn; Lambert, Pierre-Henry
2013-11-01
Asymptotic symmetries of the Einstein-Yang-Mills system with or without cosmological constant are explicitly worked out in a unified manner. In agreement with a recent conjecture, one finds a Virasoro-Kac-Moody type algebra not only in three dimensions but also in the four-dimensional asymptotically flat case.