4D Clinical Imaging for Dynamic CAD
McIntyre, Frederick
2013-01-01
A basic 4D imaging system to capture the jaw motion has been developed that produces high resolution 3D surface data. Fluorescent microspheres are brushed onto the areas of the upper and the lower arches to be imaged, producing a high-contrast random optical pattern. A hand-held imaging device operated at about 10 cm from the mouth captures time-based perspective images of the fluorescent areas. Each set of images, containing both upper and the lower arch data, is converted to a 3d point mesh using photogrammetry, thereby providing an instantaneous relative jaw position. Eight 3d positions per second are captured. Using one of the 3d frames as a reference, incremental transforms are derived to express the free body motion of the mandible. Conventional 3d models of the dentition are directly registered to the reference frame, allowing them to be animated using the derived transforms. PMID:24082882
4-D reconstruction for dynamic fluorescence diffuse optical tomography.
Liu, Xin; Zhang, Bin; Luo, Jianwen; Bai, Jing
2012-11-01
Dynamic fluorescence diffuse optical tomography (FDOT) is important for the research of drug delivery, medical diagnosis and treatment. Conventionally, dynamic tomographic images are reconstructed frame by frame, independently. This approach fails to account for the temporal correlations in measurement data. Ideally, the entire image sequence should be considered as a whole and a four-dimensional (4-D) reconstruction should be performed. However, the fully 4-D reconstruction is computationally intensive. In this paper, we propose a new 4-D reconstruction approach for dynamic FDOT, which is achieved by applying a temporal Karhunen-Loève (KL) transformation to the imaging equation. By taking advantage of the decorrelation and compression properties of the KL transformation, the complex 4-D optical reconstruction problem is greatly simplified. To evaluate the performance of the method, simulation, phantom, and in vivo experiments (N=7) are performed on a hybrid FDOT/x-ray computed tomography imaging system. The experimental results indicate that the reconstruction images obtained by the KL method provide good reconstruction quality. Additionally, by discarding high-order KL components, the computation time involved with fully 4-D reconstruction can be greatly reduced in contrast to the conventional frame-by-frame reconstruction.
4D Dynamic Required Navigation Performance Final Report
NASA Technical Reports Server (NTRS)
Finkelsztein, Daniel M.; Sturdy, James L.; Alaverdi, Omeed; Hochwarth, Joachim K.
2011-01-01
New advanced four dimensional trajectory (4DT) procedures under consideration for the Next Generation Air Transportation System (NextGen) require an aircraft to precisely navigate relative to a moving reference such as another aircraft. Examples are Self-Separation for enroute operations and Interval Management for in-trail and merging operations. The current construct of Required Navigation Performance (RNP), defined for fixed-reference-frame navigation, is not sufficiently specified to be applicable to defining performance levels of such air-to-air procedures. An extension of RNP to air-to-air navigation would enable these advanced procedures to be implemented with a specified level of performance. The objective of this research effort was to propose new 4D Dynamic RNP constructs that account for the dynamic spatial and temporal nature of Interval Management and Self-Separation, develop mathematical models of the Dynamic RNP constructs, "Required Self-Separation Performance" and "Required Interval Management Performance," and to analyze the performance characteristics of these air-to-air procedures using the newly developed models. This final report summarizes the activities led by Raytheon, in collaboration with GE Aviation and SAIC, and presents the results from this research effort to expand the RNP concept to a dynamic 4D frame of reference.
4D Dynamic RNP Annual Interim Report-Year 1
NASA Technical Reports Server (NTRS)
Finkelsztein, Daniel M.; Sturdy, James L.; Alaverdi, Omeed; Chung, William W.; Salvano, Daniel; Klooster, Joel; Hochwarth, Joachim K.
2010-01-01
This Annual Interim Report summarizes the activities led by Raytheon, in collaboration with GE Aviation and SAIC, and presents the results obtained during the first year of this research effort to expand the RNP concept to 4 dimensions relative to a dynamic frame of reference. Joint Program Development Office (JPDO)Concepts of Operations for the Next Generation Air Transportation System (NextGen) considers 4 Dimension Trajectory (4DT) procedures a key enabler to Trajectory Based Operations (TBO). The JPDO defines 4DT as a precise description of an aircraft path in space and time . While NextGen assumes that this path is defined within an Earth-reference frame, many 4DT procedure implementations will require an aircraft to precisely navigate relative to a moving reference such as another aircraft to form aggregate flows or a weather cell to allow for flows to shift. Current methods of implementing routes and flight paths rely on aircraft meeting a Required Navigation Performance (RNP) specification and being equipped with a monitoring and alerting capability to annunciate when the aircraft system is unable to meet the performance specification required for the operation. Since all aircraft today operate within the NAS relative to fixed reference points, the current RNP definition is deemed satisfactory. However, it is not well understood how the current RNP construct will support NextGen 4DT procedures where aircraft operate relative to each other or to other dynamic frames of reference. The objective of this research effort is to analyze candidate 4DT procedures from both an Air Navigation Service Provider (ANSP) and aircraft perspective, to identify their specific navigational requirements, assess the shortcomings of the current RNP construct to meet these requirements, to propose an extended 4 Dimensional Dynamic RNP (4D Dynamic RNP) construct that accounts for the dynamic spatial and temporal nature of the selected 4DT procedures, and finally, to design an
IMRT treatment planning on 4D geometries for the era of dynamic MLC tracking.
Suh, Yelin; Murray, Walter; Keall, Paul J
2014-12-01
The problem addressed here was to obtain optimal and deliverable dynamic multileaf collimator (MLC) leaf sequences from four-dimensional (4D) geometries for dynamic MLC tracking delivery. The envisaged scenario was where respiratory phase and position information of the target was available during treatment, from which the optimal treatment plan could be further adapted in real time. A tool for 4D treatment plan optimization was developed that integrates a commercially available treatment planning system and a general-purpose optimization system. The 4D planning method was applied to the 4D computed tomography planning scans of three lung cancer patients. The optimization variables were MLC leaf positions as a function of monitor units and respiratory phase. The objective function was the deformable dose-summed 4D treatment plan score. MLC leaf motion was constrained by the maximum leaf velocity between control points in terms of monitor units for tumor motion parallel to the leaf travel direction and between phases for tumor motion parallel to the leaf travel direction. For comparison and a starting point for the 4D optimization, three-dimensional (3D) optimization was performed on each of the phases. The output of the 4D IMRT planning process is a leaf sequence which is a function of both monitor unit and phase, which can be delivered to a patient whose breathing may vary between the imaging and treatment sessions. The 4D treatment plan score improved during 4D optimization by 34%, 4%, and 50% for Patients A, B, and C, respectively, indicating 4D optimization generated a better 4D treatment plan than the deformable sum of individually optimized phase plans. The dose-volume histograms for each phase remained similar, indicating robustness of the 4D treatment plan to respiratory variations expected during treatment delivery. In summary, 4D optimization for respiratory phase-dependent treatment planning with dynamic MLC motion tracking improved the 4D treatment plan
Atlas construction for dynamic (4D) PET using diffeomorphic transformations.
Bieth, Marie; Lombaert, Hervé; Reader, Andrew J; Siddiqi, Kaleem
2013-01-01
A novel dynamic (4D) PET to PET image registration procedure is proposed and applied to multiple PET scans acquired with the high resolution research tomograph (HRRT), the highest resolution human brain PET scanner available in the world. By extending the recent diffeomorphic log-demons (DLD) method and applying it to multiple dynamic [11C]raclopride scans from the HRRT, an important step towards construction of a PET atlas of unprecedented quality for [11C]raclopride imaging of the human brain has been achieved. Accounting for the temporal dimension in PET data improves registration accuracy when compared to registration of 3D to 3D time-averaged PET images. The DLD approach was chosen for its ease in providing both an intensity and shape template, through iterative sequential pair-wise registrations with fast convergence. The proposed method is applicable to any PET radiotracer, providing 4D atlases with useful applications in high accuracy PET data simulations and automated PET image analysis. PMID:24579121
The 4-D approach to visual control of autonomous systems
NASA Technical Reports Server (NTRS)
Dickmanns, Ernst D.
1994-01-01
Development of a 4-D approach to dynamic machine vision is described. Core elements of this method are spatio-temporal models oriented towards objects and laws of perspective projection in a foward mode. Integration of multi-sensory measurement data was achieved through spatio-temporal models as invariants for object recognition. Situation assessment and long term predictions were allowed through maintenance of a symbolic 4-D image of processes involving objects. Behavioral capabilities were easily realized by state feedback and feed-foward control.
4D measurement system for automatic location of anatomical structures
NASA Astrophysics Data System (ADS)
Witkowski, Marcin; Sitnik, Robert; Kujawińska, Małgorzata; Rapp, Walter; Kowalski, Marcin; Haex, Bart; Mooshake, Sven
2006-04-01
Orthopedics and neurosciences are fields of medicine where the analysis of objective movement parameters is extremely important for clinical diagnosis. Moreover, as there are significant differences between static and dynamic parameters, there is a strong need of analyzing the anatomical structures under functional conditions. In clinical gait analysis the benefits of kinematical methods are undoubted. In this paper we present a 4D (3D + time) measurement system capable of automatic location of selected anatomical structures by locating and tracing the structures' position and orientation in time. The presented system is designed to help a general practitioner in diagnosing selected lower limbs' dysfunctions (e.g. knee injuries) and also determine if a patient should be directed for further examination (e.g. x-ray or MRI). The measurement system components are hardware and software. For the hardware part we adapt the laser triangulation method. In this way we can evaluate functional and dynamic movements in a contact-free, non-invasive way, without the use of potentially harmful radiation. Furthermore, opposite to marker-based video-tracking systems, no preparation time is required. The software part consists of a data acquisition module, an image processing and point clouds (point cloud, set of points described by coordinates (x, y, z)) calculation module, a preliminary processing module, a feature-searching module and an external biomechanical module. The paper briefly presents the modules mentioned above with the focus on the feature-searching module. Also we present some measurement and analysis results. These include: parameters maps, landmarks trajectories in time sequence and animation of a simplified model of lower limbs.
Intelligent Vehicle Systems: A 4D/RCS Approach
Madhavan, Raj
2007-04-01
This book presents new research on autonomous mobility capabilities and shows how technological advances can be anticipated in the coming two decades. An in-depth description is presented on the theoretical foundations and engineering approaches that enable these capabilities. Chapter 1 provides a brief introduction to the 4D/RCS reference model architecture and design methodology that has proven successful in guiding the development of autonomous mobility systems. Chapters 2 through 7 provide more detailed descriptions of research that has been conducted and algorithms that have been developed to implement the various aspects of the 4D/RCS reference model architecture and design methodology. Chapters 8 and 9 discuss applications, performance measures, and standards. Chapter 10 provides a history of Army and DARPA research in autonomous ground mobility. Chapter 11 provides a perspective on the potential future developments in autonomous mobility.
4D Light Field Imaging System Using Programmable Aperture
NASA Technical Reports Server (NTRS)
Bae, Youngsam
2012-01-01
Complete depth information can be extracted from analyzing all angles of light rays emanated from a source. However, this angular information is lost in a typical 2D imaging system. In order to record this information, a standard stereo imaging system uses two cameras to obtain information from two view angles. Sometimes, more cameras are used to obtain information from more angles. However, a 4D light field imaging technique can achieve this multiple-camera effect through a single-lens camera. Two methods are available for this: one using a microlens array, and the other using a moving aperture. The moving-aperture method can obtain more complete stereo information. The existing literature suggests a modified liquid crystal panel [LC (liquid crystal) panel, similar to ones commonly used in the display industry] to achieve a moving aperture. However, LC panels cannot withstand harsh environments and are not qualified for spaceflight. In this regard, different hardware is proposed for the moving aperture. A digital micromirror device (DMD) will replace the liquid crystal. This will be qualified for harsh environments for the 4D light field imaging. This will enable an imager to record near-complete stereo information. The approach to building a proof-ofconcept is using existing, or slightly modified, off-the-shelf components. An SLR (single-lens reflex) lens system, which typically has a large aperture for fast imaging, will be modified. The lens system will be arranged so that DMD can be integrated. The shape of aperture will be programmed for single-viewpoint imaging, multiple-viewpoint imaging, and coded aperture imaging. The novelty lies in using a DMD instead of a LC panel to move the apertures for 4D light field imaging. The DMD uses reflecting mirrors, so any light transmission lost (which would be expected from the LC panel) will be minimal. Also, the MEMS-based DMD can withstand higher temperature and pressure fluctuation than a LC panel can. Robotics need
4D dynamic imaging of the eye using ultrahigh speed SS-OCT
NASA Astrophysics Data System (ADS)
Liu, Jonathan J.; Grulkowski, Ireneusz; Potsaid, Benjamin; Jayaraman, Vijaysekhar; Cable, Alex E.; Kraus, Martin F.; Hornegger, Joachim; Duker, Jay S.; Fujimoto, James G.
2013-03-01
Recent advances in swept-source / Fourier domain optical coherence tomography (SS-OCT) technology enable in vivo ultrahigh speed imaging, offering a promising technique for four-dimensional (4-D) imaging of the eye. Using an ultrahigh speed tunable vertical cavity surface emitting laser (VCSEL) light source based SS-OCT prototype system, we performed imaging of human eye dynamics in four different imaging modes: 1) Pupillary reaction to light at 200,000 axial scans per second and 9 μm resolution in tissue. 2) Anterior eye focusing dynamics at 100,000 axial scans per second and 9 μm resolution in tissue. 3) Tear film break up at 50,000 axial scans per second and 19 μm resolution in tissue. 4) Retinal blood flow at 800,000 axial scans per second and 12 μm resolution in tissue. The combination of tunable ultrahigh speeds and long coherence length of the VCSEL along with the outstanding roll-off performance of SS-OCT makes this technology an ideal tool for time-resolved volumetric imaging of the eye. Visualization and quantitative analysis of 4-D OCT data can potentially provide insight to functional and structural changes in the eye during disease progression. Ultrahigh speed imaging using SS-OCT promises to enable novel 4-D visualization of realtime dynamic processes of the human eye. Furthermore, this non-invasive imaging technology is a promising tool for research to characterize and understand a variety of visual functions.
4D rotational x-ray imaging of wrist joint dynamic motion
Carelsen, Bart; Bakker, Niels H.; Strackee, Simon D.; Boon, Sjirk N.; Maas, Mario; Sabczynski, Joerg; Grimbergen, Cornelis A.; Streekstra, Geert J.
2005-09-15
Current methods for imaging joint motion are limited to either two-dimensional (2D) video fluoroscopy, or to animated motions from a series of static three-dimensional (3D) images. 3D movement patterns can be detected from biplane fluoroscopy images matched with computed tomography images. This involves several x-ray modalities and sophisticated 2D to 3D matching for the complex wrist joint. We present a method for the acquisition of dynamic 3D images of a moving joint. In our method a 3D-rotational x-ray (3D-RX) system is used to image a cyclically moving joint. The cyclic motion is synchronized to the x-ray acquisition to yield multiple sets of projection images, which are reconstructed to a series of time resolved 3D images, i.e., four-dimensional rotational x ray (4D-RX). To investigate the obtained image quality parameters the full width at half maximum (FWHM) of the point spread function (PSF) via the edge spread function and the contrast to noise ratio between air and phantom were determined on reconstructions of a bullet and rod phantom, using 4D-RX as well as stationary 3D-RX images. The CNR in volume reconstructions based on 251 projection images in the static situation and on 41 and 34 projection images of a moving phantom were 6.9, 3.0, and 2.9, respectively. The average FWHM of the PSF of these same images was, respectively, 1.1, 1.7, and 2.2 mm orthogonal to the motion and parallel to direction of motion 0.6, 0.7, and 1.0 mm. The main deterioration of 4D-RX images compared to 3D-RX images is due to the low number of projection images used and not to the motion of the object. Using 41 projection images seems the best setting for the current system. Experiments on a postmortem wrist show the feasibility of the method for imaging 3D dynamic joint motion. We expect that 4D-RX will pave the way to improved assessment of joint disorders by detection of 3D dynamic motion patterns in joints.
Development of a dynamic 4D anthropomorphic breast phantom for contrast-based breast imaging
NASA Astrophysics Data System (ADS)
Kiarashi, Nooshin; Lin, Yuan; Segars, William P.; Ghate, Sujata V.; Ikejimba, Lynda; Chen, Baiyu; Lo, Joseph Y.; Dobbins, James T., III; Nolte, Loren W.; Samei, Ehsan
2012-03-01
Mammography is currently the most widely accepted tool for detection and diagnosis of breast cancer. However, the sensitivity of mammography is reduced in women with dense breast tissue due to tissue overlap, which may obscure lesions. Digital breast tomosynthesis with contrast enhancement reduces tissue overlap and provides additional functional information about lesions (i.e. morphology and kinetics), which in turn may improve lesion characterization. The performance of such techniques is highly dependent on the structural composition of the breast, which varies significantly across patients. Therefore, optimization of breast imaging systems should be done with respect to this patient versatility. Furthermore, imaging techniques that employ contrast require the inclusion of a temporally varying breast composition with respect to the contrast agent kinetics to enable the optimization of the system. To these ends, we have developed a dynamic 4D anthropomorphic breast phantom, which can be used for optimizing a breast imaging system by incorporating material characteristics. The presented dynamic phantom is based on two recently developed anthropomorphic breast phantoms, which can be representative of a whole population through their randomized anatomical feature generation and various compression levels. The 4D dynamic phantom is incorporated with the kinetics of contrast agent uptake in different tissues and can realistically model benign and malignant lesions. To demonstrate the utility of the proposed dynamic phantom, contrast-enhanced digital mammography and breast tomosynthesis were simulated where a ray-tracing algorithm emulated the projections, a filtered back projection algorithm was used for reconstruction, and dual-energy and temporal subtractions were performed and compared.
Dynamically accumulated dose and 4D accumulated dose for moving tumors
Li Heng; Li Yupeng; Zhang Xiaodong; Li Xiaoqiang; Liu Wei; Gillin, Michael T.; Zhu, X. Ronald
2012-12-15
Purpose: The purpose of this work was to investigate the relationship between dynamically accumulated dose (dynamic dose) and 4D accumulated dose (4D dose) for irradiation of moving tumors, and to quantify the dose uncertainty induced by tumor motion. Methods: The authors established that regardless of treatment modality and delivery properties, the dynamic dose will converge to the 4D dose, instead of the 3D static dose, after multiple deliveries. The bounds of dynamic dose, or the maximum estimation error using 4D or static dose, were established for the 4D and static doses, respectively. Numerical simulations were performed (1) to prove the principle that for each phase, after multiple deliveries, the average number of deliveries for any given time converges to the total number of fractions (K) over the number of phases (N); (2) to investigate the dose difference between the 4D and dynamic doses as a function of the number of deliveries for deliveries of a 'pulsed beam'; and (3) to investigate the dose difference between 4D dose and dynamic doses as a function of delivery time for deliveries of a 'continuous beam.' A Poisson model was developed to estimate the mean dose error as a function of number of deliveries or delivered time for both pulsed beam and continuous beam. Results: The numerical simulations confirmed that the number of deliveries for each phase converges to K/N, assuming a random starting phase. Simulations for the pulsed beam and continuous beam also suggested that the dose error is a strong function of the number of deliveries and/or total deliver time and could be a function of the breathing cycle, depending on the mode of delivery. The Poisson model agrees well with the simulation. Conclusions: Dynamically accumulated dose will converge to the 4D accumulated dose after multiple deliveries, regardless of treatment modality. Bounds of the dynamic dose could be determined using quantities derived from 4D doses, and the mean dose difference
4D tumor centroid tracking using orthogonal 2D dynamic MRI: Implications for radiotherapy planning
Tryggestad, Erik; Flammang, Aaron; Shea, Steven M.; Hales, Russell; Herman, Joseph; Lee, Junghoon; McNutt, Todd; Roland, Teboh; Wong, John
2013-09-15
Purpose: Current pretreatment, 4D imaging techniques are suboptimal in that they sample breathing motion over a very limited “snapshot” in time. Heretofore, long-duration, 4D motion characterization for radiotherapy planning, margin optimization, and validation have been impractical for safety reasons, requiring invasive markers imaged under x-ray fluoroscopy. To characterize 3D tumor motion and associated variability over durations more consistent with treatments, the authors have developed a practical dynamic MRI (dMRI) technique employing two orthogonal planes acquired in a continuous, interleaved fashion.Methods: 2D balanced steady-state free precession MRI was acquired continuously over 9–14 min at approximately 4 Hz in three healthy volunteers using a commercial 1.5 T system; alternating orthogonal imaging planes (sagittal, coronal, sagittal, etc.) were employed. The 2D in-plane pixel resolution was 2 × 2 mm{sup 2} with a 5 mm slice profile. Simultaneous with image acquisition, the authors monitored a 1D surrogate respiratory signal using a device available with the MRI system. 2D template matching-based anatomic feature registration, or tracking, was performed independently in each orientation. 4D feature tracking at the raw frame rate was derived using spline interpolation.Results: Tracking vascular features in the lung for two volunteers and pancreatic features in one volunteer, the authors have successfully demonstrated this method. Registration error, defined here as the difference between the sagittal and coronal tracking result in the SI direction, ranged from 0.7 to 1.6 mm (1σ) which was less than the acquired image resolution. Although the healthy volunteers were instructed to relax and breathe normally, significantly variable respiration was observed. To demonstrate potential applications of this technique, the authors subsequently explored the intrafraction stability of hypothetical tumoral internal target volumes and 3D spatial probability
Biglino, Giovanni; Cosentino, Daria; Steeden, Jennifer A.; De Nova, Lorenzo; Castelli, Matteo; Ntsinjana, Hopewell; Pennati, Giancarlo; Taylor, Andrew M.; Schievano, Silvia
2015-01-01
Computational fluid dynamics (CFD) can have a complementary predictive role alongside the exquisite visualization capabilities of 4D cardiovascular magnetic resonance (CMR) imaging. In order to exploit these capabilities (e.g., for decision-making), it is necessary to validate computational models against real world data. In this study, we sought to acquire 4D CMR flow data in a controllable, experimental setup and use these data to validate a corresponding computational model. We applied this paradigm to a case of congenital heart disease, namely, transposition of the great arteries (TGA) repaired with arterial switch operation. For this purpose, a mock circulatory loop compatible with the CMR environment was constructed and two detailed aortic 3D models (i.e., one TGA case and one normal aortic anatomy) were tested under realistic hemodynamic conditions, acquiring 4D CMR flow. The same 3D domains were used for multi-scale CFD simulations, whereby the remainder of the mock circulatory system was appropriately summarized with a lumped parameter network. Boundary conditions of the simulations mirrored those measured in vitro. Results showed a very good quantitative agreement between experimental and computational models in terms of pressure (overall maximum % error = 4.4% aortic pressure in the control anatomy) and flow distribution data (overall maximum % error = 3.6% at the subclavian artery outlet of the TGA model). Very good qualitative agreement could also be appreciated in terms of streamlines, throughout the cardiac cycle. Additionally, velocity vectors in the ascending aorta revealed less symmetrical flow in the TGA model, which also exhibited higher wall shear stress in the anterior ascending aorta. PMID:26697416
Analysis and dynamic 3D visualization of cerebral blood flow combining 3D and 4D MR image sequences
NASA Astrophysics Data System (ADS)
Forkert, Nils Daniel; Säring, Dennis; Fiehler, Jens; Illies, Till; Möller, Dietmar; Handels, Heinz
2009-02-01
In this paper we present a method for the dynamic visualization of cerebral blood flow. Spatio-temporal 4D magnetic resonance angiography (MRA) image datasets and 3D MRA datasets with high spatial resolution were acquired for the analysis of arteriovenous malformations (AVMs). One of the main tasks is the combination of the information of the 3D and 4D MRA image sequences. Initially, in the 3D MRA dataset the vessel system is segmented and a 3D surface model is generated. Then, temporal intensity curves are analyzed voxelwise in the 4D MRA image sequences. A curve fitting of the temporal intensity curves to a patient individual reference curve is used to extract the bolus arrival times in the 4D MRA sequences. After non-linear registration of both MRA datasets the extracted hemodynamic information is transferred to the surface model where the time points of inflow can be visualized color coded dynamically over time. The dynamic visualizations computed using the curve fitting method for the estimation of the bolus arrival times were rated superior compared to those computed using conventional approaches for bolus arrival time estimation. In summary the procedure suggested allows a dynamic visualization of the individual hemodynamic situation and better understanding during the visual evaluation of cerebral vascular diseases.
Dynamic real-time 4D cardiac MDCT image display using GPU-accelerated volume rendering.
Zhang, Qi; Eagleson, Roy; Peters, Terry M
2009-09-01
Intraoperative cardiac monitoring, accurate preoperative diagnosis, and surgical planning are important components of minimally-invasive cardiac therapy. Retrospective, electrocardiographically (ECG) gated, multidetector computed tomographical (MDCT), four-dimensional (3D + time), real-time, cardiac image visualization is an important tool for the surgeon in such procedure, particularly if the dynamic volumetric image can be registered to, and fused with the actual patient anatomy. The addition of stereoscopic imaging provides a more intuitive environment by adding binocular vision and depth cues to structures within the beating heart. In this paper, we describe the design and implementation of a comprehensive stereoscopic 4D cardiac image visualization and manipulation platform, based on the opacity density radiation model, which exploits the power of modern graphics processing units (GPUs) in the rendering pipeline. In addition, we present a new algorithm to synchronize the phases of the dynamic heart to clinical ECG signals, and to calculate and compensate for latencies in the visualization pipeline. A dynamic multiresolution display is implemented to enable the interactive selection and emphasis of volume of interest (VOI) within the entire contextual cardiac volume and to enhance performance, and a novel color and opacity adjustment algorithm is designed to increase the uniformity of the rendered multiresolution image of heart. Our system provides a visualization environment superior to noninteractive software-based implementations, but with a rendering speed that is comparable to traditional, but inferior quality, volume rendering approaches based on texture mapping. This retrospective ECG-gated dynamic cardiac display system can provide real-time feedback regarding the suspected pathology, function, and structural defects, as well as anatomical information such as chamber volume and morphology.
4D light-field sensing system for people counting
NASA Astrophysics Data System (ADS)
Hou, Guangqi; Zhang, Chi; Wang, Yunlong; Sun, Zhenan
2016-03-01
Counting the number of people is still an important task in social security applications, and a few methods based on video surveillance have been proposed in recent years. In this paper, we design a novel optical sensing system to directly acquire the depth map of the scene from one light-field camera. The light-field sensing system can count the number of people crossing the passageway, and record the direction and intensity of rays at a snapshot without any assistant light devices. Depth maps are extracted from the raw light-ray sensing data. Our smart sensing system is equipped with a passive imaging sensor, which is able to naturally discern the depth difference between the head and shoulders for each person. Then a human model is built. Through detecting the human model from light-field images, the number of people passing the scene can be counted rapidly. We verify the feasibility of the sensing system as well as the accuracy by capturing real-world scenes passing single and multiple people under natural illumination.
Teaching Tip: Managing Software Engineering Student Teams Using Pellerin's 4-D System
ERIC Educational Resources Information Center
Doman, Marguerite; Besmer, Andrew; Olsen, Anne
2015-01-01
In this article, we discuss the use of Pellerin's Four Dimension Leadership System (4-D) as a way to manage teams in a classroom setting. Over a 5-year period, we used a modified version of the 4-D model to manage teams within a senior level Software Engineering capstone course. We found that this approach for team management in a classroom…
Upgrade and benchmarking of a 4D treatment planning system for scanned ion beam therapy
Richter, D.; Schwarzkopf, A.; Trautmann, J.; Durante, M.; Kraemer, M.; Jaekel, O.; Bert, C.
2013-05-15
Purpose: Upgrade and benchmarking of a research 4D treatment planning system (4DTPS) suitable for realistic patient treatment planning and treatment simulations taking into account specific requirements for scanned ion beam therapy, i.e., modeling of dose heterogeneities due to interplay effects and range changes caused by patient motion and dynamic beam delivery. Methods: The 4DTPS integrates data interfaces to 4D computed tomography (4DCT), deformable image registration and clinically used motion monitoring devices. The authors implemented a novel data model for 4D image segmentation using Boolean mask volume datasets and developed an algorithm propagating a manually contoured reference contour dataset to all 4DCT phases. They further included detailed treatment simulation and dose reconstruction functionality, based on the irregular patient motion and the temporal structure of the beam delivery. The treatment simulation functionality was validated against experimental data from irradiation of moving radiographic films in air, 3D moving ionization chambers in a water phantom, and moving cells in a biological phantom with a scanned carbon ion beam. The performance of the program was compared to results obtained with predecessor programs. Results: The measured optical density distributions of the radiographic films were reproduced by the simulations to (-2 {+-} 12)%. Compared to earlier versions of the 4DTPS, the mean agreement improved by 2%, standard deviations were reduced by 7%. The simulated dose to the moving ionization chambers in water showed an agreement with the measured dose of (-1 {+-} 4)% for the typical beam configuration. The mean deviation of the simulated from the measured biologically effective dose determined via cell survival was (617 {+-} 538) mGy relative biological effectiveness corresponding to (10 {+-} 9)%. Conclusions: The authors developed a research 4DTPS suitable for realistic treatment planning on patient data and capable of simulating
Selective 4D modelling framework for spatial-temporal land information management system
NASA Astrophysics Data System (ADS)
Doulamis, Anastasios; Soile, Sofia; Doulamis, Nikolaos; Chrisouli, Christina; Grammalidis, Nikos; Dimitropoulos, Kosmas; Manesis, Charalambos; Potsiou, Chryssy; Ioannidis, Charalabos
2015-06-01
This paper introduces a predictive (selective) 4D modelling framework where only the spatial 3D differences are modelled at the forthcoming time instances, while regions of no significant spatial-temporal alterations remain intact. To accomplish this, initially spatial-temporal analysis is applied between 3D digital models captured at different time instances. So, the creation of dynamic change history maps is made. Change history maps indicate spatial probabilities of regions needed further 3D modelling at forthcoming instances. Thus, change history maps are good examples for a predictive assessment, that is, to localize surfaces within the objects where a high accuracy reconstruction process needs to be activated at the forthcoming time instances. The proposed 4D Land Information Management System (LIMS) is implemented using open interoperable standards based on the CityGML framework. CityGML allows the description of the semantic metadata information and the rights of the land resources. Visualization aspects are also supported to allow easy manipulation, interaction and representation of the 4D LIMS digital parcels and the respective semantic information. The open source 3DCityDB incorporating a PostgreSQL geo-database is used to manage and manipulate 3D data and their semantics. An application is made to detect the change through time of a 3D block of plots in an urban area of Athens, Greece. Starting with an accurate 3D model of the buildings in 1983, a change history map is created using automated dense image matching on aerial photos of 2010. For both time instances meshes are created and through their comparison the changes are detected.
4D optical coherence tomography of aortic valve dynamics in a murine mouse model ex vivo
NASA Astrophysics Data System (ADS)
Schnabel, Christian; Jannasch, Anett; Faak, Saskia; Waldow, Thomas; Koch, Edmund
2015-07-01
The heart and its mechanical components, especially the heart valves and leaflets, are under enormous strain during lifetime. Like all highly stressed materials, also these biological components undergo fatigue and signs of wear, which impinge upon cardiac output and in the end on health and living comfort of affected patients. Thereby pathophysiological changes of the aortic valve leading to calcific aortic valve stenosis (AVS) as most frequent heart valve disease in humans are of particular interest. The knowledge about changes of the dynamic behavior during the course of this disease and the possibility of early stage diagnosis could lead to the development of new treatment strategies and drug-based options of prevention or therapy. ApoE-/- mice as established model of AVS versus wildtype mice were introduced in an ex vivo artificially stimulated heart model. 4D optical coherence tomography (OCT) in combination with high-speed video microscopy were applied to characterize dynamic behavior of the murine aortic valve and to characterize dynamic properties during artificial stimulation. OCT and high-speed video microscopy with high spatial and temporal resolution represent promising tools for the investigation of dynamic behavior and their changes in calcific aortic stenosis disease models in mice.
Dynamics of chemical bonding mapped by energy-resolved 4D electron microscopy.
Carbone, Fabrizio; Kwon, Oh-Hoon; Zewail, Ahmed H
2009-07-10
Chemical bonding dynamics are fundamental to the understanding of properties and behavior of materials and molecules. Here, we demonstrate the potential of time-resolved, femtosecond electron energy loss spectroscopy (EELS) for mapping electronic structural changes in the course of nuclear motions. For graphite, it is found that changes of milli-electron volts in the energy range of up to 50 electron volts reveal the compression and expansion of layers on the subpicometer scale (for surface and bulk atoms). These nonequilibrium structural features are correlated with the direction of change from sp2 [two-dimensional (2D) graphene] to sp3 (3D-diamond) electronic hybridization, and the results are compared with theoretical charge-density calculations. The reported femtosecond time resolution of four-dimensional (4D) electron microscopy represents an advance of 10 orders of magnitude over that of conventional EELS methods. PMID:19589997
Simulations of 4D edge transport and dynamics using the TEMPEST gyro-kinetic code
NASA Astrophysics Data System (ADS)
Rognlien, T. D.; Cohen, B. I.; Cohen, R. H.; Dorr, M. R.; Hittinger, J. A. F.; Kerbel, G. D.; Nevins, W. M.; Xiong, Z.; Xu, X. Q.
2006-10-01
Simulation results are presented for tokamak edge plasmas with a focus on the 4D (2r,2v) option of the TEMPEST continuum gyro-kinetic code. A detailed description of a variety of kinetic simulations is reported, including neoclassical radial transport from Coulomb collisions, electric field generation, dynamic response to perturbations by geodesic acoustic modes, and parallel transport on open magnetic-field lines. Comparison is made between the characteristics of the plasma solutions on closed and open magnetic-field line regions separated by a magnetic separatrix, and simple physical models are used to qualitatively explain the differences observed in mean flow and electric-field generation. The status of extending the simulations to 5D turbulence will be summarized. The code structure used in this ongoing project is also briefly described, together with future plans.
A practical introduction to the hemodynamic analysis of the cardiovascular system with 4D Flow MRI.
Pineda Zapata, J A; Delgado de Bedout, J A; Rascovsky Ramírez, S; Bustamante, C; Mesa, S; Calvo Betancur, V D
2014-01-01
The 4D Flow MRI technique provides a three-dimensional representation of blood flow over time, making it possible to evaluate the hemodynamics of the cardiovascular system both qualitatively and quantitatively. In this article, we describe the application of the 4D Flow technique in a 3T scanner; in addition to the technical parameters, we discuss the advantages and limitations of the technique and its possible clinical applications. We used 4D Flow MRI to study different body areas (chest, abdomen, neck, and head) in 10 volunteers. We obtained 3D representations of the patterns of flow and quantitative hemodynamic measurements. The technique makes it possible to evaluate the pattern of blood flow in large and midsize vessels without the need for exogenous contrast agents.
NASA Astrophysics Data System (ADS)
Ishchenko, A. A.; Bagratashvili, V. N.; Avilov, A. S.
2011-09-01
Studies in the coupled 4D spatial and temporal continuum are necessary for understanding the dynamic features of molecular systems with a complex profile of the potential energy surface. The introduction of time sweep into diffraction methods and the development of principles for studying coherent processes have revealed new approaches to the analysis of the dynamics of wave packets, the intermediate products and the transition state of the reaction center, and short-lived compounds in gaseous and condensed media. The use of picosecond and femtosecond electron probe pulses, synchronized with excitation laser pulses, determined the development of ultrafast electron crystallography, time-resolved X-ray diffraction, and dynamic transmission electron microscopy (DTEM). One of the most promising applications of the developed diffraction methods is the characterization and visualization of the processes occurring upon the photoexcitation of free molecules and biological objects and the analysis of surface and thin films. The whole set of spectral and diffraction methods based on different physical principles, which are complementary and make it possible to perform the photoexcitation of nuclei and electrons and carry out diagnostics of their dynamics at ultrashort time sequences, reveal new possibilities for studies with the necessary integration of the "structure-dynamics-function" triad in chemistry, biology, and materials science.
Anderson, Jeff R; Diaz, Orlando; Klucznik, Richard; Zhang, Y Jonathan; Britz, Gavin W; Grossman, Robert G; Lv, Nan; Huang, Qinghai; Karmonik, Christof
2014-01-01
A new concept of rapid 3D prototyping was implemented using cost-effective 3D printing for creating anatomically correct replica of cerebral aneurysms. With a dedicated flow loop set-up in a full body human MRI scanner, flow measurements were performed using 4D phase contrast magnetic resonance imaging to visualize and quantify intra-aneurysmal flow patterns. Ultrashort TE sequences were employed to obtain high-resolution 3D image data to visualize the lumen inside the plastic replica. In-vitro results were compared with retrospectively obtained in-vivo data and results from computational fluid dynamics simulations (CFD). Rapid prototyping of anatomically realistic 3D models may have future impact in treatment planning, design of image acquisition methods for MRI and angiographic systems and for the design and testing of advanced image post-processing technologies.
Evaluation of the Elekta Symmetry ™ 4D IGRT system by using a moving lung phantom
NASA Astrophysics Data System (ADS)
Shin, Hun-Joo; Kim, Shin-Wook; Kay, Chul Seung; Seo, Jae-Hyuk; Lee, Gi-Woong; Kang, Ki-Mun; Jang, Hong Seok; Kang, Young-nam
2015-07-01
Purpose: 4D cone-beam computed tomography (CBCT) is a beneficial tool for the treatment of movable tumors because it can help us to understand where the tumors are actually located and it has a precise treatment plan. However, general CBCT images have a limitation in that they cannot perfectly perform a sophisticated registration. On the other hand, the Symmetry TM 4D image-guided radiation therapy (IGRT) system of Elekta offers a 4D CBCT registration option. In this study, we evaluated the usefulness of Symmetry TM . Method and Materials: Planning CT images of the CIRS moving lung phantom were acquired 4D multi-detector CT (MDCT), and the images were sorted as 10 phases from 0% phase to 90% phase. The thickness of the CT images was 1 mm. Acquired MDCT images were transferred to the contouring software, and a virtual target was generated. A one-arc volumetric-modulated arc therapy (VMAT) plan was performed by using the treatment planning system on the virtual target. Finally, the movement of the phantom was verified by using the XVI Symmetry TM system. Results: The physical movement of the CIRS moving lung phantom was ±10.0 mm in the superiorinferior direction, ±1.0 mm in the lateral direction, and ±2.5 mm in the anterior-posterior direction. The movement of the phantom was measured from the 4D MDCT registration as ±10.2 mm in the superior-inferior direction, ±0.9 mm in the lateral direction, and ±2.45 mm in the anterior-posterior direction. The movement of the phantom was measured from the SymmetryTM registration as ±10.1 mm in the superior-inferior direction, ±0.9 mm in the lateral direction, and ±2.4 mm in the anterior-posterior direction. Conclusion: We confirmed that 4D CBCT is a beneficial tool for the treatment of movable tumors, and that the 4D registration of SymmetryTM can increase the precision of the registration when a movable tumor is the target of radiation treatment.
Orbital-selective singlet dimer formation and suppression of double exchange in 4d and 5d systems
NASA Astrophysics Data System (ADS)
Streltsov, Sergey; Cao, Gang; Khomskii, Daniel
One of the main mechanisms of ferromagnetic ordering in conducting materials is the double exchange (DE). It is usually supposed in DE model that the Hund's coupling JH is much larger than electron hopping t; in this case one stabilizes the state with maximum spin per pair of ions, which finally leads to ferromagnetism in bulk systems. We show that in the dimerized 4 d / 5 d transition metal oxides for which JH is reduced and t is in contrast enhanced, another situation is possible, when formation of the spin-singlets on delocalized orbitals is more favorable. This leads to suppression of the DE and to a strong decrease of the total spin. The model calculations using the dynamical mean-field theory show that this effect survives even in the extended systems, not only for dimers. Such a situation is realized, e.g., in Y5Mo2O12, CrO2 under pressure and in many other 4 d / 5 d based materials. Another mechanism, which may suppress DE and which is also typical for 4 d / 5 d compounds is the spin-orbit coupling (SOC). We show on the example of Ba5AlIr2O11, that in this system it is the combination of molecular-orbital formation and SOC that strongly decreases magnetic moment on Ir. Civil Research and Development Foundation via FSCX-14-61025-0.
Wang, H.; Snell, G.; Hemmers, O.; Sant'Anna, M. M.; Sellin, I.; Berrah, N.; Lindle, D. W.; Deshmukh, P. C.; Haque, N.; Manson, S. T.
2001-09-17
Two decades ago, it was predicted [Y.S.Kim et al., Phys.Rev.Lett.46, 1326 (1981)] that relativistic effects should alter the dynamics of the photoionization process in the vicinity of Cooper minima. The present experimental and theoretical study of the angular distributions of Xe 4d{sub 3/2} and 4d{sub 5/2} photoelectrons demonstrates this effect for the first time. The results clearly imply that relativistic effects are likely to be important for intermediate-Z atoms at most energies.
Reilhac, Anthonin; Charil, Arnaud; Wimberley, Catriona; Angelis, Georgios; Hamze, Hasar; Callaghan, Paul; Garcia, Marie-Paule; Boisson, Frederic; Ryder, Will; Meikle, Steven R; Gregoire, Marie-Claude
2015-09-01
Quantitative measurements in dynamic PET imaging are usually limited by the poor counting statistics particularly in short dynamic frames and by the low spatial resolution of the detection system, resulting in partial volume effects (PVEs). In this work, we present a fast and easy to implement method for the restoration of dynamic PET images that have suffered from both PVE and noise degradation. It is based on a weighted least squares iterative deconvolution approach of the dynamic PET image with spatial and temporal regularization. Using simulated dynamic [(11)C] Raclopride PET data with controlled biological variations in the striata between scans, we showed that the restoration method provides images which exhibit less noise and better contrast between emitting structures than the original images. In addition, the method is able to recover the true time activity curve in the striata region with an error below 3% while it was underestimated by more than 20% without correction. As a result, the method improves the accuracy and reduces the variability of the kinetic parameter estimates calculated from the corrected images. More importantly it increases the accuracy (from less than 66% to more than 95%) of measured biological variations as well as their statistical detectivity. PMID:26080302
EarthScope imaging of 4D stress evolution of the San Andreas Fault System
NASA Astrophysics Data System (ADS)
Smith-Konter, B. R.; Del Pardo, C.
2011-12-01
EarthScope seismic and geodetic observations, combined with sophisticated computational models and powerful visualization tools, are now providing a critical ensemble of information about interseismic stressing rates along the San Andreas Fault System (SAFS). When combined with paleoseismic chronologies of earthquake ruptures spanning the last several hundreds of years, four-dimensional (4D) simulations of stress evolution spanning multiple earthquake cycles are now possible. To investigate stress variations at depth along the SAFS over multiple earthquake cycles, we use a 4D semi-analytic model that simulates interseismic strain accumulation, coseismic displacement, and post-seismic viscoelastic relaxation of the mantle. The model utilizes geologic estimates of fault locations and slip rates, as well as paleoseismic earthquake rupture histories, and is computed at a 500 m grid resolution to better resolve the sharp deformation gradients at creeping faults. Using EarthScope PBO and ALOS InSAR data, we tune the model locking depths and slip rates to compute the 4D stress accumulation within the seismogenic crust. 4D models show that stress accumulation and stress drop are a complex function of space and time. We use ParaView 3.10, an open-source multi-platform visualization package, for manipulation and visualization of 4D stress variations of fault segments at depth. We use ParaView to create a 3D meshed volume spanning a ~1000 x 1500 x 50 km region of the SAFS and present both volume and sliced views of stress from several viewpoints along the plate boundary. These models reveal pockets of stress concentrated at depth due to the interaction of neighboring fault segments and at fault segment branching junctions. We present several sensitivity tests that reveal the variation of stress at depth as a function of locking depth, slip rate, coefficient of friction, elastic plate thickness, and viscosity. These visualizations lay the groundwork for 4D time
The 4D area navigation system description and flight test results
NASA Technical Reports Server (NTRS)
Lee, H. Q.; Neuman, F.; Hardy, G. H.
1975-01-01
A 4D area navigation system was designed to guide aircraft along a prespecified flight path (reference path) such that the aircraft would arrive at the approach gate at a time specified by the ATC controller. Key components to achieve this requirement were: (1) stored reference trajectories; (2) a continuously recomputed capture trajectory to a selected waypoint on the reference trajectory so as to achieve the desired time of arrival; (3) electronic situation displays; and (4) a control system to follow the overall trajectory in space and time. The system was implemented in a digital integrated avionics system (STOLAND) installed on a CV-340 airplane. Although the 4D system was designed primarily for automatic operation, it was flight tested in a flight director mode (the pilot follows the flight director commands), because the CV-340 autopilot servos were not tied to the avionics system. The flight test showed that, even in the flight director mode, the pilot did achieve the objectives of path tracking and time of arrival control with only moderate workload. The system also permitted controlled delay of the time of arrival by path stretching, which takes advantage of the continuously changing capture trajectory to predict the time of arrival. Simulations in the automatic and manual modes were used to complement the flight data.
Three dimensional dose verification of VMAT plans using the Octavius 4D dosimetric system
NASA Astrophysics Data System (ADS)
Arumugam, Sankar; Xing, Aitang; Young, Tony; Thwaites, David; Holloway, Lois
2015-01-01
The Octavius 4D dosimetric system generates a 3D dose matrix based on a measured planar dose and user supplied Percentage Depth Dose (PDD) data. The accuracy of 3D dose matrices reconstructed by the Octavius 4D dosimetric system was systematically studied for an open static field, an open arc field and clinical VMAT plans. The Octavius reconstructed 3D dose matrices were compared with the Treatment Planning System (TPS) calculated 3D dose matrices using 3D gamma (γ) analysis with 2%/2mm and 3%/3mm tolerance criteria. The larger detector size in the 2D detector array of the Octavius system resulted in failed voxels in the high dose gradient regions. For the open arc fields mean (1σ) γ pass rates of 84.5(8.9) % and 94.2(4.5) % were observed with 2%/2mm and 3%/3mm tolerance criteria respectively and for clinical VMAT plans mean (1σ) γ pass rates of 86.8(3.5) % and 96.7(1.4) % were observed.
Semantic World Modelling and Data Management in a 4d Forest Simulation and Information System
NASA Astrophysics Data System (ADS)
Roßmann, J.; Hoppen, M.; Bücken, A.
2013-08-01
Various types of 3D simulation applications benefit from realistic forest models. They range from flight simulators for entertainment to harvester simulators for training and tree growth simulations for research and planning. Our 4D forest simulation and information system integrates the necessary methods for data extraction, modelling and management. Using modern methods of semantic world modelling, tree data can efficiently be extracted from remote sensing data. The derived forest models contain position, height, crown volume, type and diameter of each tree. This data is modelled using GML-based data models to assure compatibility and exchangeability. A flexible approach for database synchronization is used to manage the data and provide caching, persistence, a central communication hub for change distribution, and a versioning mechanism. Combining various simulation techniques and data versioning, the 4D forest simulation and information system can provide applications with "both directions" of the fourth dimension. Our paper outlines the current state, new developments, and integration of tree extraction, data modelling, and data management. It also shows several applications realized with the system.
NASA Astrophysics Data System (ADS)
Li, Wenqing; Chen, Ge; Kong, Qianqian; Wang, Zhenzhen; Qian, Chengcheng
2011-11-01
The development of the VR-Ocean system coincides with the first availability of more than 15 years (1992-2009) of the merged altimeter data from up to four concurrent satellite missions (Topex/Poseidon, ERS-1 and 2, ENVISAT, Jason-1, and Geosat Follow-On) and ETOPO1 Ice Surface data (1 arc-minute global relief model of the Earth's surface that integrates land topography and ocean bathymetry). In the polar-region-oriented VR-Ocean system, the seabed and continental topography data south of 45°S were organized in a circular area and rendered in the form of geometry clipmaps. Maps of Sea-Level Anomalies (MSLA) data for the same district were extracted and streamlined in time order. A memory-mapped file was used to accelerate file loading speed, and sea surfaces of different times were rendered in turn as a vertex buffer object (VBO) and accelerated by the graphic processing unit (GPU). As a result, roaming anywhere at any angle of view and geospatial analysis are interactively obtained and dynamically presented in real-time using the 4D VR-Ocean system. As an attempt, we did a case study on ice melting and sea-level rise around the Antarctic. This system is expected to make a significant contribution to the description, understanding, prediction, and demonstration of 4D information and properties on both regional and hemispheric scales in a virtual environment.
Biederer, Juergen Dinkel, Julien; Remmert, Gregor; Jetter, Siri; Nill, Simeon; Moser, Torsten; Bendl, Rolf; Thierfelder, Carsten; Fabel, Michael; Oelfke, Uwe; Bock, Michael; Plathow, Christian; Bolte, Hendrik; Welzel, Thomas; Hoffmann, Beata; Hartmann, Guenter; Schlegel, Wolfgang; Debus, Juergen; Heller, Martin
2009-03-01
Purpose: Four-dimensional (4D) imaging is a key to motion-adapted radiotherapy of lung tumors. We evaluated in a ventilated ex vivo system how size and displacement of artificial pulmonary nodules are reproduced with helical 4D-CT, 4D-MRI, and linac-integrated cone beam CT (CBCT). Methods and Materials: Four porcine lungs with 18 agarose nodules (mean diameters 1.3-1.9 cm), were ventilated inside a chest phantom at 8/min and subject to 4D-CT (collimation 24 x 1.2 mm, pitch 0.1, slice/increment 24x10{sup 2}/1.5/0.8 mm, pitch 0.1, temporal resolution 0.5 s), 4D-MRI (echo-shared dynamic three-dimensional-flash; repetition/echo time 2.13/0.72 ms, voxel size 2.7 x 2.7 x 4.0 mm, temporal resolution 1.4 s) and linac-integrated 4D-CBCT (720 projections, 3-min rotation, temporal resolution {approx}1 s). Static CT without respiration served as control. Three observers recorded lesion size (RECIST-diameters x/y/z) and axial displacement. Interobserver- and interphase-variation coefficients (IO/IP VC) of measurements indicated reproducibility. Results: Mean x/y/z lesion diameters in cm were equal on static and dynamic CT (1.88/1.87; 1.30/1.39; 1.71/1.73; p > 0.05), but appeared larger on MRI and CBCT (2.06/1.95 [p < 0.05 vs. CT]; 1.47/1.28 [MRI vs. CT/CBCT p < 0.05]; 1.86/1.83 [CT vs. CBCT p < 0.05]). Interobserver-VC for lesion sizes were 2.54-4.47% (CT), 2.29-4.48% (4D-CT); 5.44-6.22% (MRI) and 4.86-6.97% (CBCT). Interphase-VC for lesion sizes ranged from 2.28% (4D-CT) to 10.0% (CBCT). Mean displacement in cm decreased from static CT (1.65) to 4D-CT (1.40), CBCT (1.23) and MRI (1.16). Conclusions: Lesion sizes are exactly reproduced with 4D-CT but overestimated on 4D-MRI and CBCT with a larger variability due to limited temporal and spatial resolution. All 4D-modalities underestimate lesion displacement.
López-Castilla, Aracelys; Pons, Tirso; Pires, José R
2015-04-01
Q4D059 (UniProt accession number), is an 86-residue protein from Trypanosoma cruzi, conserved in the related kinetoplastid parasites Trypanosoma brucei and Leishmania major. These pathogens are the causal agents of the neglected diseases: Chagas, sleeping sickness and leishmaniases respectively and had recently their genomes sequenced. Q4D059 shows low sequence similarity with mammal proteins and because of its essentiality demonstrated in T. brucei, it is a potential target for anti-parasitic drugs. The 11 hypothetical proteins homologous to Q4D059 are all uncharacterized proteins of unknown function. Here, the solution structure of Q4D059 was solved by NMR and its backbone dynamics was characterized by (15)N relaxation parameters. The structure is composed by a parallel/anti-parallel three-stranded β-sheet packed against four helical regions. The structure is well defined by ca. 9 NOEs per residue and a backbone rmsd of 0.50±0.05 Å for the representative ensemble of 20 lowest-energy structures. The structure is overall rigid except for N-terminal residues A(9) to D(11) at the beginning of β1, K(38), V(39) at the end of helix H3 with rapid motion in the ps-ns timescale and G(25) (helix H2), I(68) (β2) and V(78) (loop 3) undergoing internal motion in the μs-ms timescale. Limited structural similarities were found in protein structures deposited in the PDB, therefore functional inferences based on protein structure information are not clear. Q4D059 adopts a α/β fold that is slightly similar to the ATPase sub-domain IIB of the heat-shock protein 70 (HSP70) and to the N-terminal domain of the ribosomal protein L11. PMID:25748338
Development of 4D jaw movement visualization system for dental diagnosis support
NASA Astrophysics Data System (ADS)
Aoki, Yoshimitsu; Terajima, Masahiko; Nakasima, Akihiko
2004-10-01
A person with an asymmetric morphology of maxillofacial skeleton reportedly possesses an asymmetric jaw function and the risk to express temporomandibular disorder is high. A comprehensive analysis from the point of view of both the morphology and the function such as maxillofacial or temporomandibular joint morphology, dental occlusion, and features of mandibular movement pathways is essential. In this study, the 4D jaw movement visualization system was developed to visually understand the characteristic jaw movement, 3D maxillofacial skeleton structure, and the alignment of the upper and lower teeth of a patient. For this purpose, the 3D reconstructed images of the cranial and mandibular bones, obtained by computed tomography, were measured using a non-contact 3D measuring device, and the obtained morphological images of teeth model were integrated and activated on the 6 DOF jaw movement data. This system was experimentally applied and visualized in a jaw deformity patient and its usability as a clinical diagnostic support system was verified.
A new 4-D dynamical modelling of the Moon orbital and rotational motion developed at POLAC
NASA Astrophysics Data System (ADS)
Bourgoin, A.; Le Poncin-Lafitte, C.; Bouquillon, S.; Francou, G.; Angonin, M.-C.
2015-12-01
Nowadays, General Relativity (GR) is very well tested within the Solar System using observables given by the tracking of spacecraft tep{2003Natur.425..374B}, Very Long Baseline Interferometry tep{2009A&A...499..331L,2011A&A...529A..70L} and Lunar Laser Ranging -LLR- tep{2010LRR....13....7M}. These tests are mainly based on two frameworks: the Parametrized Post Newtonian (PPN) and the search for a fifth force. However other frameworks are available and can be used to look for deviations from GR. In this context, we present the ongoing work concerning LLR performed at POLAC (Paris Observatory Lunar Analysis Center) in SYRTE, Paris Observatory. We focus on a new generation of software that simulates the observable (the round trip time of photons) from a given space-time metric tep{2012CQGra..29w5027H}. This flexible approach allows to perform simulations in any alternative metric theories of gravity. The output of these software provides templates of anomalous residuals that should show up in real data if the underlying theory of gravity is not GR. Those templates can be used to give a rough estimation of the constraints on the additional parameters involved in the alternative theory. To succeed, we are building a numerical lunar ephemeris which integrates the differential equations governing the orbital and rotational motion of bodies in the Solar System. In addition, we integrate the difference between the Terrestrial Time (TT) and the Barycentric Dynamical Time (TDB) to make the ephemeris self-consistent. Special attention is paid to the computation of partial derivatives since they are integrated numerically from the variational equations.
Dynamic Multiscale Boundary Conditions for 4D CT Images of Healthy and Emphysematous Rat
Jacob, Rick E.; Carson, James P.; Thomas, Mathew; Einstein, Daniel R.
2013-06-14
Changes in the shape of the lung during breathing determine the movement of airways and alveoli, and thus impact airflow dynamics. Modeling airflow dynamics in health and disease is a key goal for predictive multiscale models of respiration. Past efforts to model changes in lung shape during breathing have measured shape at multiple breath-holds. However, breath-holds do not capture hysteretic differences between inspiration and expiration resulting from the additional energy required for inspiration. Alternatively, imaging dynamically – without breath-holds – allows measurement of hysteretic differences. In this study, we acquire multiple micro-CT images per breath (4DCT) in live rats, and from these images we develop, for the first time, dynamic volume maps. These maps show changes in local volume across the entire lung throughout the breathing cycle and accurately predict the global pressure-volume (PV) hysteresis.
Heinz, Christian; Reiner, Michael; Belka, Claus; Walter, Franziska; Söhn, Matthias
2015-03-08
Respiratory monitoring systems are required to supply CT scanners with information on the patient's breathing during the acquisition of a respiration-correlated computer tomography (RCCT), also referred to as 4D CT. The information a respiratory monitoring system has to provide to the CT scanner depends on the specific scanner. The purpose of this study is to compare two different respiratory monitoring systems (Anzai Respiratory Gating System; C-RAD Sentinel) with respect to their applicability in combination with an Aquilion Large Bore CT scanner from Toshiba. The scanner used in our clinic does not make use of the full time dependent breathing signal, but only single trigger pulses indicating the beginning of a new breathing cycle. Hence the attached respiratory monitoring system is expected to deliver accurate online trigger pulse for each breathing cycle. The accuracy of the trigger pulses sent to the CT scanner has to be ensured by the selected respiratory monitoring system. Since a trigger pulse (output signal) of a respiratory monitoring system is a function of the measured breathing signal (input signal), the typical clinical range of the input signal is estimated for both examined respiratory monitoring systems. Both systems are analyzed based on the following parameters: time resolution, signal amplitude, noise, signal-to-noise ratio (SNR), signal linearity, trigger compatibility, and clinical examples. The Anzai system shows a better SNR (≥ 28 dB) than the Sentinel system (≥ 14.6 dB). In terms of compatibility with the cycle-based image sorting algorithm of the Toshiba CT scanner, the Anzai system benefits from the possibility to generate cycle-based triggers, whereas the Sentinel system is only able to generate amplitude-based triggers. In clinical practice, the combination of a Toshiba CT scanner and the Anzai system will provide better results due to the compatibility of the image sorting and trigger release methods.
Dynamic Multiscale Boundary Conditions for 4D CT of Healthy and Emphysematous Rats
Jacob, Richard E.; Carson, James P.; Thomas, Mathew; Einstein, Daniel R.
2013-01-01
Changes in the shape of the lung during breathing determine the movement of airways and alveoli, and thus impact airflow dynamics. Modeling airflow dynamics in health and disease is a key goal for predictive multiscale models of respiration. Past efforts to model changes in lung shape during breathing have measured shape at multiple breath-holds. However, breath-holds do not capture hysteretic differences between inspiration and expiration resulting from the additional energy required for inspiration. Alternatively, imaging dynamically – without breath-holds – allows measurement of hysteretic differences. In this study, we acquire multiple micro-CT images per breath (4DCT) in live rats, and from these images we develop, for the first time, dynamic volume maps. These maps show changes in local volume across the entire lung throughout the breathing cycle and accurately predict the global pressure-volume (PV) hysteresis. Male Sprague-Dawley rats were given either a full- or partial-lung dose of elastase or saline as a control. After three weeks, 4DCT images of the mechanically ventilated rats under anesthesia were acquired dynamically over the breathing cycle (11 time points, ≤100 ms temporal resolution, 8 cmH2O peak pressure). Non-rigid image registration was applied to determine the deformation gradient – a numerical description of changes to lung shape – at each time point. The registration accuracy was evaluated by landmark identification. Of 67 landmarks, one was determined misregistered by all three observers, and 11 were determined misregistered by two observers. Volume change maps were calculated on a voxel-by-voxel basis at all time points using both the Jacobian of the deformation gradient and the inhaled air fraction. The calculated lung PV hysteresis agrees with pressure-volume curves measured by the ventilator. Volume maps in diseased rats show increased compliance and ventilation heterogeneity. Future predictive multiscale models of rodent
Real-time dynamic display of registered 4D cardiac MR and ultrasound images using a GPU
NASA Astrophysics Data System (ADS)
Zhang, Q.; Huang, X.; Eagleson, R.; Guiraudon, G.; Peters, T. M.
2007-03-01
In minimally invasive image-guided surgical interventions, different imaging modalities, such as magnetic resonance imaging (MRI), computed tomography (CT), and real-time three-dimensional (3D) ultrasound (US), can provide complementary, multi-spectral image information. Multimodality dynamic image registration is a well-established approach that permits real-time diagnostic information to be enhanced by placing lower-quality real-time images within a high quality anatomical context. For the guidance of cardiac procedures, it would be valuable to register dynamic MRI or CT with intraoperative US. However, in practice, either the high computational cost prohibits such real-time visualization of volumetric multimodal images in a real-world medical environment, or else the resulting image quality is not satisfactory for accurate guidance during the intervention. Modern graphics processing units (GPUs) provide the programmability, parallelism and increased computational precision to begin to address this problem. In this work, we first outline our research on dynamic 3D cardiac MR and US image acquisition, real-time dual-modality registration and US tracking. Then we describe image processing and optimization techniques for 4D (3D + time) cardiac image real-time rendering. We also present our multimodality 4D medical image visualization engine, which directly runs on a GPU in real-time by exploiting the advantages of the graphics hardware. In addition, techniques such as multiple transfer functions for different imaging modalities, dynamic texture binding, advanced texture sampling and multimodality image compositing are employed to facilitate the real-time display and manipulation of the registered dual-modality dynamic 3D MR and US cardiac datasets.
NASA Astrophysics Data System (ADS)
Tong, Yubing; Udupa, Jayaram K.; Odhner, Dewey; Sin, Sanghun; Wagshul, Mark E.; Arens, Raanan
2014-03-01
There are several disease conditions that lead to upper airway restrictive disorders. In the study of these conditions, it is important to take into account the dynamic nature of the upper airway. Currently, dynamic MRI is the modality of choice for studying these diseases. Unfortunately, the contrast resolution obtainable in the images poses many challenges for an effective segmentation of the upper airway structures. No viable methods have been developed to date to solve this problem. In this paper, we demonstrate the adaptation of the iterative relative fuzzy connectedness (IRFC) algorithm for this application as a potential practical tool. After preprocessing to correct for background image non-uniformities and the non-standardness of MRI intensities, seeds are specified for the airway and its crucial background tissue components in only the 3D image corresponding to the first time instance of the 4D volume. Subsequently the process runs without human interaction and completes segmenting the whole 4D volume in 10 sec. Our evaluations indicate that the segmentations are of very good quality achieving true positive and false positive volume fractions and boundary distance with respect to reference manual segmentations of about 93%, 0.1%, and 0.5 mm, respectively.
Hönekopp, Johannes
2012-08-01
Prenatal testosterone (PT) effects have been proposed to increase systemizing (the drive to understand lawful input-output relationships), to decrease empathizing (the drive to understand others), and to cause autism via hypermasculinization of the brain. Digit ratio 2D:4D is a putative marker of PT effects in humans. An online study (n = 1896) into the relationship between the Reading the Mind in the Eyes Test (a widely used measure of empathizing) and self-measured 2D:4D in a nonclinical sample is reported. No evidence for a link between empathizing and 2D:4D in either females or males emerged. Further, three meta-analyses are presented that look into the relationships of 2D:4D with autism spectrum disorder (ASD), systemizing, and empathizing. 2D:4D was substantially lower (more masculine) in ASD-affected individuals than in normal controls (d = -0.58, P < 0.001). However, 2D:4D was found to be virtually unrelated to systemizing and empathizing in normal adults. The results support the idea that high PT is a risk factor for autism, but they challenge the view that PT substantially contributes to sex differences in systemizing and empathizing. Possibly, this pattern reflects an interaction effect, whereby PT drives ASD characteristic changes only in brains with a specific damage.
Akimoto, Mami; Nakamura, Mitsuhiro; Miyabe, Yuki; Mukumoto, Nobutaka; Yokota, Kenji; Mizowaki, Takashi; Hiraoka, Masahiro
2015-09-08
We assessed long-term stability of tracking accuracy using the Vero4DRT system. This metric was observed between September 2012 and March 2015. A programmable respiratory motion phantom, designed to move phantoms synchronously with respiratory surrogates, was used. The infrared (IR) markers moved in the anterior-posterior (AP) direction as respiratory surrogates, while a cube phantom with a steel ball at the center, representing the tumor, and with radiopaque markers around it moved in the superior-inferior (SI) direction with one-dimensional (1D) sinusoidal patterns. A correlation model between the tumor and IR marker motion (4D model) was created from the training data obtained for 20 s just before beam delivery. The irradiation field was set to 3 × 3 cm2 and 300 monitor units (MUs) of desired MV X-ray beam were delivered. The gantry and ring angles were set to 0° and 45°, respectively. During beam delivery, the system recorded approximately 60 electronic portal imaging device (EPID) images. We analyzed: 1) the predictive accuracy of the 4D model (EP), defined as the difference between the detected and predicted target positions during 4D model creation, and 2) the tracking accuracy (ET), defined as the difference between the center of the steel ball and the MV X-ray field on the EPID image. The median values of mean plus two standard deviations (SDs) for EP were 0.06, 0.35, and 0.06 mm in the left-right (LR), SI, and AP directions, respectively. The mean values of maximum deviation for ET were 0.38, 0.49, and 0.53 mm and the coefficients of variance (CV) were 0.16, 0.10, and 0.05 in lateral, longitudinal, and 2D directions, respectively. Consequently, the IR Tracking accuracy was consistent over a period of two years. Our proposed method assessed the overall tracking accuracy readily using real-time EPID images, and proved to be a useful QA tool for dynamic tumor tracking with the Vero4DRT system.
4d electron Ruthenate systems: their unique and new magnetic properties
NASA Astrophysics Data System (ADS)
Lee, Seungran; Shin, Yeongjae; Anwar, M. S.; Sugimoto, Yusuke; Lee, Mincheol; Kang, Sungjin; Yonezawa, Shingo; Maeno, Yoshiteru; Noh, Taewon
The Ruddlesden-Popper series (PR) of Srn+1RunO3n+1 has attract much interest of their unique physical properties. Among them, SrRuO3 (n = ∞) (SRO) is the only ferromagnetic metallic oxide especially in Ru 4d transition metal oxides. Bulk SRO has orthorhombic structure showing the Curie temperature (TC) ~ 160 K. It is well known that RuO6 octahedral distortion plays critical roles in its mangetic properties. In film systems, such RuO6 octahedra can be easily controlled by strain-engineering. In this talk, with high quality SRO films fully strained (-1.7%-1%) using various substrates, we systematically studied their structural changes and associated magnetic properties. Compared to theoretical predictions, the structural changes can be explained, while the magnetic property changes cannot be understood. Surprisingly, when SRO113 is grown on its PR series of Sr2RuO4 (n=1) (SRO214) single crystal, the exact substrate of SRO214 magnetization results in strongly enhanced magnetization (M > 3 μB/Ru, TC ~ 160 K), which has never found SRO113 (001) since the low-spin configuration of SRO113 prevent M never exceed 2 μB/Ru. The mystery of M in SRO113 (especially SRO113/SRO214) will be further discussed.
NASA Astrophysics Data System (ADS)
Xiang, Liangzhong; Wang, Bo; Ji, Lijun; Jiang, Huabei
2013-01-01
Photoacoustic tomography (PAT) offers three-dimensional (3D) structural and functional imaging of living biological tissue with label-free, optical absorption contrast. These attributes lend PAT imaging to a wide variety of applications in clinical medicine and preclinical research. Despite advances in live animal imaging with PAT, there is still a need for 3D imaging at centimeter depths in real-time. We report the development of four dimensional (4D) PAT, which integrates time resolutions with 3D spatial resolution, obtained using spherical arrays of ultrasonic detectors. The 4D PAT technique generates motion pictures of imaged tissue, enabling real time tracking of dynamic physiological and pathological processes at hundred micrometer-millisecond resolutions. The 4D PAT technique is used here to image needle-based drug delivery and pharmacokinetics. We also use this technique to monitor 1) fast hemodynamic changes during inter-ictal epileptic seizures and 2) temperature variations during tumor thermal therapy.
NASA Astrophysics Data System (ADS)
Carvajal Meneses, Carla C.
Pore pressure and CO2 saturation changes are important to detect and quantify for maximizing oil recovery in Delhi Field. Delhi Field is a enhanced oil recovery (EOR) project with active monitoring by 4D multicomponent seismic technologies. Dynamic rock physics modeling integrates the rich dataset of core, well logs, petrographic thin sections and facies providing a link between reservoir and elastic properties. The dynamic modeling in this high porosity sandstone reservoir shows that P-wave velocity is more sensitive to CO2 saturation while S-wave velocity is more sensitive to pore pressure changes. I use PP and PS seismic data to jointly invert for Vp=Vs ratio and acoustic impedance. This technique has the advantage of adding more information to the non-unique inversion problem. Combining the inversion results from the monitor surveys of June 2010 and August 2011 provides acoustic impedance and Vp=Vs percentage differences. The time-lapse inverted response enables dynamic characterization of the reservoir by fitting the predicted dynamic models (calibrated at the wells). Dynamic reservoir characterization adds value in this stratigraphic complex reservoir. The results indicate that reservoir heterogeneities and pore pressure gradients control the CO2 flow within the Paluxy reservoir. Injectors 148-2 and 140-1 showed CO2 is moving downdip following a distributary channel induced by differential pressure from an updip injector or a barrier caused by a heterogeneity in the reservoir. CO2 anomalies located above the Paluxy injector 148-2 indicates that CO2 is moving from the Paluxy up into the Tuscaloosa Formation. My work demonstrates that reservoir monitoring is necessary for reservoir management at Delhi Field.
Suzuki, Naoki; Hattori, Asaki; Hayashibe, Mitsuhiro; Suzuki, Shigeyuki; Otake, Yoshito
2003-01-01
We have developed an imaging system for free and quantitative observation of human locomotion in a time-spatial domain by way of real time imaging. The system is equipped with 60 computer controlled video cameras to film human locomotion from all angles simultaneously. Images are installed into the main graphic workstation and translated into a 2D image matrix. Observation of the subject from optional directions is able to be performed by selecting the view point from the optimum image sequence in this image matrix. This system also possesses a function to reconstruct 4D models of the subject's moving human body by using 60 images taken from all directions at one particular time. And this system also has the capability to visualize inner structures such as the skeletal or muscular systems of the subject by compositing computer graphics reconstructed from the MRI data set. We are planning to apply this imaging system to clinical observation in the area of orthopedics, rehabilitation and sports science.
NASA Astrophysics Data System (ADS)
Dobson, Katherine J.; Coban, Sophia B.; McDonald, Samuel A.; Walsh, Joanna N.; Atwood, Robert C.; Withers, Philip J.
2016-07-01
A variable volume flow cell has been integrated with state-of-the-art ultra-high-speed synchrotron X-ray tomography imaging. The combination allows the first real-time (sub-second) capture of dynamic pore (micron)-scale fluid transport processes in 4-D (3-D + time). With 3-D data volumes acquired at up to 20 Hz, we perform in situ experiments that capture high-frequency pore-scale dynamics in 5-25 mm diameter samples with voxel (3-D equivalent of a pixel) resolutions of 2.5 to 3.8 µm. The data are free from motion artefacts and can be spatially registered or collected in the same orientation, making them suitable for detailed quantitative analysis of the dynamic fluid distribution pathways and processes. The methods presented here are capable of capturing a wide range of high-frequency nonequilibrium pore-scale processes including wetting, dilution, mixing, and reaction phenomena, without sacrificing significant spatial resolution. As well as fast streaming (continuous acquisition) at 20 Hz, they also allow larger-scale and longer-term experimental runs to be sampled intermittently at lower frequency (time-lapse imaging), benefiting from fast image acquisition rates to prevent motion blur in highly dynamic systems. This marks a major technical breakthrough for quantification of high-frequency pore-scale processes: processes that are critical for developing and validating more accurate multiscale flow models through spatially and temporally heterogeneous pore networks.
NASA Astrophysics Data System (ADS)
Neveu, Emilie; Moore, Andrew M.; Edwards, Christopher A.; Fiechter, Jérôme; Drake, Patrick; Crawford, William J.; Jacox, Michael G.; Nuss, Emma
2016-03-01
The Regional Ocean Modeling System (ROMS) 4-dimensional variational (4D-Var) data assimilation tool has been used to compute two sequences of circulation analyses for the U.S. west coast. One sequence of analyses spans the period 1980-2010 and is subject to surface forcing derived from relatively low resolution atmospheric products from the Cross-Calibrated Multi-Platform wind product (CCMP) and the European Centre for Medium Range Weather Forecasts (ECMWF) reanalysis project. The second sequence spans the shorter period 1999-2012 and is subject to forcing derived from a high resolution product from the Naval Research Laboratory Coupled Ocean Atmosphere Mesoscale Prediction System (COAMPS). The two analysis periods are divided into eight day windows, and all available satellite observations of sea surface temperature and sea surface height, as well as in situhydrographic profiles are assimilated into ROMS using 4D-Var. The performance of the system is monitored in terms of the cost function and the statistics of the innovations, and the impact of data assimilated on the circulation is assessed by comparing the posterior circulation estimates with the prior circulation and the circulation from a run of the model without data assimilation, with particular emphasis on eddy kinetic energy. This is part I of a two part series, and the circulation variability of the 4D-Var analyses will be documented in part II.
NASA Astrophysics Data System (ADS)
Ji, Youn-Sang; Dong, Kyung-Rae; Kim, Chang-Bok; Chung, Woon-Kwan; Cho, Jae-Hwan; Lee, Hae-Kag
2012-10-01
This study evaluated the gating-based 4-D conformal radiation therapy (4D-CT) treatment planning by a comparison with the common 3-D conformal radiation therapy (3D-CT) treatment planning and examined the change in treatment field size and dose to the tumors and adjacent normal tissues because an unnecessary dose is also included in the 3-D treatment planning for the radiation treatment of tumors in the chest and abdomen. The 3D-CT and gating-based 4D-CT images were obtained from patients who had undergone radiation treatment for chest and abdomen tumors in the oncology department. After establishing a treatment plan, the CT treatment and planning system were used to measure the change in field size for analysis. A dose volume histogram (DVH) was used to calculate the appropriate dose to planning target volume (PTV) tumors and adjacent normal tissue. The difference in the treatment volume of the chest was 0.6 and 0.83 cm on the X- and Y-axis, respectively, for the gross tumor volume (GTV). Accordingly, the values in the 4D-CT treatment planning were smaller and the dose was more concentrated by 2.7% and 0.9% on the GTV and clinical target volume (CTV), respectively. The normal tissues in the surrounding normal tissues were reduced by 3.0%, 7.2%, 0.4%, 1.7%, 2.6% and 0.2% in the bronchus, chest wall, esophagus, heart, lung and spinal cord, respectively. The difference in the treatment volume of the abdomen was 0.72 cm on the X-axis and 0.51 cm on the Y-axis for the GTV; and 1.06 cm on the X-axis and 1.85 cm on the Y-axis for the PTV. Therefore, the values in the 4D-CT treatment planning were smaller. The dose was concentrated by 6.8% and 4.3% on the GTV and PTV, respectively, whereas the adjacent normal tissues in the cord, Lt. kidney, Rt. kidney, small bowels and whole liver were reduced by 3.2%, 4.2%, 1.5%, 6.2% and 12.7%, respectively. The treatment field size was smaller in volume in the case of the 4D-CT treatment planning. In the DVH, the 4D-CT treatment
Kotasidis, F A; Mehranian, A; Zaidi, H
2016-05-01
Kinetic parameter estimation in dynamic PET suffers from reduced accuracy and precision when parametric maps are estimated using kinetic modelling following image reconstruction of the dynamic data. Direct approaches to parameter estimation attempt to directly estimate the kinetic parameters from the measured dynamic data within a unified framework. Such image reconstruction methods have been shown to generate parametric maps of improved precision and accuracy in dynamic PET. However, due to the interleaving between the tomographic and kinetic modelling steps, any tomographic or kinetic modelling errors in certain regions or frames, tend to spatially or temporally propagate. This results in biased kinetic parameters and thus limits the benefits of such direct methods. Kinetic modelling errors originate from the inability to construct a common single kinetic model for the entire field-of-view, and such errors in erroneously modelled regions could spatially propagate. Adaptive models have been used within 4D image reconstruction to mitigate the problem, though they are complex and difficult to optimize. Tomographic errors in dynamic imaging on the other hand, can originate from involuntary patient motion between dynamic frames, as well as from emission/transmission mismatch. Motion correction schemes can be used, however, if residual errors exist or motion correction is not included in the study protocol, errors in the affected dynamic frames could potentially propagate either temporally, to other frames during the kinetic modelling step or spatially, during the tomographic step. In this work, we demonstrate a new strategy to minimize such error propagation in direct 4D image reconstruction, focusing on the tomographic step rather than the kinetic modelling step, by incorporating time-of-flight (TOF) within a direct 4D reconstruction framework. Using ever improving TOF resolutions (580 ps, 440 ps, 300 ps and 160 ps), we demonstrate that direct 4D TOF image
NASA Astrophysics Data System (ADS)
Kotasidis, F. A.; Mehranian, A.; Zaidi, H.
2016-05-01
Kinetic parameter estimation in dynamic PET suffers from reduced accuracy and precision when parametric maps are estimated using kinetic modelling following image reconstruction of the dynamic data. Direct approaches to parameter estimation attempt to directly estimate the kinetic parameters from the measured dynamic data within a unified framework. Such image reconstruction methods have been shown to generate parametric maps of improved precision and accuracy in dynamic PET. However, due to the interleaving between the tomographic and kinetic modelling steps, any tomographic or kinetic modelling errors in certain regions or frames, tend to spatially or temporally propagate. This results in biased kinetic parameters and thus limits the benefits of such direct methods. Kinetic modelling errors originate from the inability to construct a common single kinetic model for the entire field-of-view, and such errors in erroneously modelled regions could spatially propagate. Adaptive models have been used within 4D image reconstruction to mitigate the problem, though they are complex and difficult to optimize. Tomographic errors in dynamic imaging on the other hand, can originate from involuntary patient motion between dynamic frames, as well as from emission/transmission mismatch. Motion correction schemes can be used, however, if residual errors exist or motion correction is not included in the study protocol, errors in the affected dynamic frames could potentially propagate either temporally, to other frames during the kinetic modelling step or spatially, during the tomographic step. In this work, we demonstrate a new strategy to minimize such error propagation in direct 4D image reconstruction, focusing on the tomographic step rather than the kinetic modelling step, by incorporating time-of-flight (TOF) within a direct 4D reconstruction framework. Using ever improving TOF resolutions (580 ps, 440 ps, 300 ps and 160 ps), we demonstrate that direct 4D TOF image
NASA Astrophysics Data System (ADS)
Bowen, S. R.; Nyflot, M. J.; Herrmann, C.; Groh, C. M.; Meyer, J.; Wollenweber, S. D.; Stearns, C. W.; Kinahan, P. E.; Sandison, G. A.
2015-05-01
Effective positron emission tomography / computed tomography (PET/CT) guidance in radiotherapy of lung cancer requires estimation and mitigation of errors due to respiratory motion. An end-to-end workflow was developed to measure patient-specific motion-induced uncertainties in imaging, treatment planning, and radiation delivery with respiratory motion phantoms and dosimeters. A custom torso phantom with inserts mimicking normal lung tissue and lung lesion was filled with [18F]FDG. The lung lesion insert was driven by six different patient-specific respiratory patterns or kept stationary. PET/CT images were acquired under motionless ground truth, tidal breathing motion-averaged (3D), and respiratory phase-correlated (4D) conditions. Target volumes were estimated by standardized uptake value (SUV) thresholds that accurately defined the ground-truth lesion volume. Non-uniform dose-painting plans using volumetrically modulated arc therapy were optimized for fixed normal lung and spinal cord objectives and variable PET-based target objectives. Resulting plans were delivered to a cylindrical diode array at rest, in motion on a platform driven by the same respiratory patterns (3D), or motion-compensated by a robotic couch with an infrared camera tracking system (4D). Errors were estimated relative to the static ground truth condition for mean target-to-background (T/Bmean) ratios, target volumes, planned equivalent uniform target doses, and 2%-2 mm gamma delivery passing rates. Relative to motionless ground truth conditions, PET/CT imaging errors were on the order of 10-20%, treatment planning errors were 5-10%, and treatment delivery errors were 5-30% without motion compensation. Errors from residual motion following compensation methods were reduced to 5-10% in PET/CT imaging, <5% in treatment planning, and <2% in treatment delivery. We have demonstrated that estimation of respiratory motion uncertainty and its propagation from PET/CT imaging to RT planning, and RT
Bowen, S R; Nyflot, M J; Hermann, C; Groh, C; Meyer, J; Wollenweber, S D; Stearns, C W; Kinahan, P E; Sandison, G A
2015-01-01
Effective positron emission tomography/computed tomography (PET/CT) guidance in radiotherapy of lung cancer requires estimation and mitigation of errors due to respiratory motion. An end-to-end workflow was developed to measure patient-specific motion-induced uncertainties in imaging, treatment planning, and radiation delivery with respiratory motion phantoms and dosimeters. A custom torso phantom with inserts mimicking normal lung tissue and lung lesion was filled with [18F]FDG. The lung lesion insert was driven by 6 different patient-specific respiratory patterns or kept stationary. PET/CT images were acquired under motionless ground truth, tidal breathing motion-averaged (3D), and respiratory phase-correlated (4D) conditions. Target volumes were estimated by standardized uptake value (SUV) thresholds that accurately defined the ground-truth lesion volume. Non-uniform dose-painting plans using volumetrically modulated arc therapy (VMAT) were optimized for fixed normal lung and spinal cord objectives and variable PET-based target objectives. Resulting plans were delivered to a cylindrical diode array at rest, in motion on a platform driven by the same respiratory patterns (3D), or motion-compensated by a robotic couch with an infrared camera tracking system (4D). Errors were estimated relative to the static ground truth condition for mean target-to-background (T/Bmean) ratios, target volumes, planned equivalent uniform target doses (EUD), and 2%-2mm gamma delivery passing rates. Relative to motionless ground truth conditions, PET/CT imaging errors were on the order of 10–20%, treatment planning errors were 5–10%, and treatment delivery errors were 5–30% without motion compensation. Errors from residual motion following compensation methods were reduced to 5–10% in PET/CT imaging, < 5% in treatment planning, and < 2% in treatment delivery. We have demonstrated that estimation of respiratory motion uncertainty and its propagation from PET/CT imaging to RT
Knight-Greenfield, Ashley; Jajamovich, Guido; Besa, Cecilia; Cui, Yong; Stalder, Aurélien; Markl, Michael; Taouli, Bachir
2015-01-01
Purpose To develop a highly accelerated phase-contrast cardiac-gated volume flow measurement (four-dimensional [4D] flow) magnetic resonance (MR) imaging technique based on spiral sampling and dynamic compressed sensing and to compare this technique with established phase-contrast imaging techniques for the quantification of blood flow in abdominal vessels. Materials and Methods This single-center prospective study was compliant with HIPAA and approved by the institutional review board. Ten subjects (nine men, one woman; mean age, 51 years; age range, 30–70 years) were enrolled. Seven patients had liver disease. Written informed consent was obtained from all participants. Two 4D flow acquisitions were performed in each subject, one with use of Cartesian sampling with respiratory tracking and the other with use of spiral sampling and a breath hold. Cartesian two-dimensional (2D) cine phase-contrast images were also acquired in the portal vein. Two observers independently assessed vessel conspicuity on phase-contrast three-dimensional angiograms. Quantitative flow parameters were measured by two independent observers in major abdominal vessels. Intertechnique concordance was quantified by using Bland-Altman and logistic regression analyses. Results There was moderate to substantial agreement in vessel conspicuity between 4D flow acquisitions in arteries and veins (κ = 0.71 and 0.61, respectively, for observer 1; κ = 0.71 and 0.44 for observer 2), whereas more artifacts were observed with spiral 4D flow (κ = 0.30 and 0.20). Quantitative measurements in abdominal vessels showed good equivalence between spiral and Cartesian 4D flow techniques (lower bound of the 95% confidence interval: 63%, 77%, 60%, and 64% for flow, area, average velocity, and peak velocity, respectively). For portal venous flow, spiral 4D flow was in better agreement with 2D cine phase-contrast flow (95% limits of agreement: −8.8 and 9.3 mL/sec, respectively) than was Cartesian 4D flow (95
A 4D-Ensemble-Variational System for Data Assimilation and Ensemble Initialization
NASA Astrophysics Data System (ADS)
Bowler, Neill; Clayton, Adam; Jardak, Mohamed; Lee, Eunjoo; Jermey, Peter; Lorenc, Andrew; Piccolo, Chiara; Pring, Stephen; Wlasak, Marek; Barker, Dale; Inverarity, Gordon; Swinbank, Richard
2016-04-01
The Met Office has been developing a four-dimensional ensemble variational (4DEnVar) data assimilation system over the past four years. The 4DEnVar system is intended both as data assimilation system in its own right and also an improved means of initializing the Met Office Global and Regional Ensemble Prediction System (MOGREPS). The global MOGREPS ensemble has been initialized by running an ensemble of 4DEnVars (En-4DEnVar). The scalability and maintainability of ensemble data assimilation methods make them increasingly attractive, and 4DEnVar may be adopted in the context of the Met Office's LFRic project to redevelop the technical infrastructure to enable its Unified Model (MetUM) to be run efficiently on massively parallel supercomputers. This presentation will report on the results of the 4DEnVar development project, including experiments that have been run using ensemble sizes of up to 200 members.
A 3D- and 4D-ESR imaging system for small animals.
Oikawa, K; Ogata, T; Togashi, H; Yokoyama, H; Ohya-Nishiguchi, H; Kamada, H
1996-01-01
A new version of in vivo ESR-CT system composed of custom-made 0.7 GHz ESR spectrometer, air-core magnet with a field-scanning coil, three field-gradient coils, and two computers enables up- and down-field, and rapid magnetic-field scanning linearly controlled by computer. 3D-pictures of distribution of nitroxide radicals injected in brains and livers of rats and mice were obtained in 1.5 min with resolution of 1 mm. We have also succeeded in obtaining spatial-time imagings of the animals.
4D modelling of the Alto Tiberina Fault system (Northern Apennines, Italy)
NASA Astrophysics Data System (ADS)
De Donatis, Mauro; Susini, Sara; Mirabella, Francesco; Lupattelli, Andrea; Barchi, Massimiliano
2014-05-01
The Alto Tiberina Fault (ATF) in the Northern Apennines of Italy is a low-angle normal fault dipping to the East and accommodating up to 10 km of extension. The fault is ~70 km long and is the detachment for the SW-dipping Gubbio normal fault. The ATF fault system has been dramatically exhumed and the ATF footwall has evolved in a horst bounded to the east by ATF synthetic faults and to the west by the Corciano west-dipping normal fault. The fault has been widely studied over the last years in order to understand its mechanical behaviour, its present-day deformation rate and its seismological role. By using a wide data-set including subsurface data (seismic reflection profiles and boreholes) and surface geological data (new maps of the CARG project of Italy), we have reconstructed the 3D geometry of both the fault and of the main lithostratigraphic boundaries at the fault hanging-wall and foot-wall. The CARG map data were integrated by local observations and mapping using mobile GIS software (BeeGIS) and Android app (Geopaparazzi). Surface data were combined with seismic reflection profiles and wells interpretation and other data from available literature. The large amount of information were combined in MOVE software (Midland Valley Exploration ltd). Our reconstruction allows to i) build up a three-dimensional geological model of the subsurface including the main faults and lithostratigraphic boundaries; ii) identify a set of east-west trending faults the role of which was previously underestimated; iii) test a 3D-restoration of extension for the visualization of the time evolution and for the validation of the structural reconstruction. The restored structures are the main normal faults in the region. The sequential restoration was performed by taking into account the timing of deformation as derived from the literature. The model was sequentially restored according to the following chronological order from the latest to the oldest: 1a) last deformational event
Yoo, Byung-Kuk; Su, Zixue; Thomas, John Meurig; Zewail, Ahmed H.
2016-01-01
Understanding the dynamical nature of the catalytic active site embedded in complex systems at the atomic level is critical to developing efficient photocatalytic materials. Here, we report, using 4D ultrafast electron microscopy, the spatiotemporal behaviors of titanium and oxygen in a titanosilicate catalytic material. The observed changes in Bragg diffraction intensity with time at the specific lattice planes, and with a tilted geometry, provide the relaxation pathway: the Ti4+=O2− double bond transformation to a Ti3+−O1− single bond via the individual atomic displacements of the titanium and the apical oxygen. The dilation of the double bond is up to 0.8 Å and occurs on the femtosecond time scale. These findings suggest the direct catalytic involvement of the Ti3+−O1− local structure, the significance of nonthermal processes at the reactive site, and the efficient photo-induced electron transfer that plays a pivotal role in many photocatalytic reactions. PMID:26729878
Cibis, Merih; Jarvis, Kelly; Markl, Michael; Rose, Michael; Rigsby, Cynthia; Barker, Alex J; Wentzel, Jolanda J
2015-09-18
Viscous dissipation inside Fontan circulation, a parameter associated with the exercise intolerance of Fontan patients, can be derived from computational fluid dynamics (CFD) or 4D flow MRI velocities. However, the impact of spatial resolution and measurement noise on the estimation of viscous dissipation is unclear. Our aim was to evaluate the influence of these parameters on viscous dissipation calculation. Six Fontan patients underwent whole heart 4D flow MRI. Subject-specific CFD simulations were performed. The CFD velocities were down-sampled to isotropic spatial resolutions of 0.5mm, 1mm, 2mm and to MRI resolution. Viscous dissipation was compared between (1) high resolution CFD velocities, (2) CFD velocities down-sampled to MRI resolution, (3) down-sampled CFD velocities with MRI mimicked noise levels, and (4) in-vivo 4D flow MRI velocities. Relative viscous dissipation between subjects was also calculated. 4D flow MRI velocities (15.6 ± 3.8 cm/s) were higher, although not significantly different than CFD velocities (13.8 ± 4.7 cm/s, p=0.16), down-sampled CFD velocities (12.3 ± 4.4 cm/s, p=0.06) and the down-sampled CFD velocities with noise (13.2 ± 4.2 cm/s, p=0.06). CFD-based viscous dissipation (0.81 ± 0.55 mW) was significantly higher than those based on down-sampled CFD (0.25 ± 0.19 mW, p=0.03), down-sampled CFD with noise (0.49 ± 0.26 mW, p=0.03) and 4D flow MRI (0.56 ± 0.28 mW, p=0.06). Nevertheless, relative viscous dissipation between different subjects was maintained irrespective of resolution and noise, suggesting that comparison of viscous dissipation between patients is still possible.
NASA Astrophysics Data System (ADS)
Schroeder, Walter; Schulze, Wolfram; Wetter, Thomas; Chen, Chi-Hsien
2008-08-01
Three-dimensional (3D) body surface reconstruction is an important field in health care. A popular method for this purpose is laser scanning. However, using Photometric Stereo (PS) to record lumbar lordosis and the surface contour of the back poses a viable alternative due to its lower costs and higher flexibility compared to laser techniques and other methods of three-dimensional body surface reconstruction. In this work, we extended the traditional PS method and proposed a new method for obtaining surface and volume data of a moving object. The principle of traditional Photometric Stereo uses at least three images of a static object taken under different light sources to obtain 3D information of the object. Instead of using normal light, the light sources in the proposed method consist of the RGB-Color-Model's three colors: red, green and blue. A series of pictures taken with a video camera can now be separated into the different color channels. Each set of the three images can then be used to calculate the surface normals as a traditional PS. This method waives the requirement that the object imaged must be kept still as in almost all the other body surface reconstruction methods. By putting two cameras opposite to a moving object and lighting the object with the colored light, the time-varying surface (4D) data can easily be calculated. The obtained information can be used in many medical fields such as rehabilitation, diabetes screening or orthopedics.
SU-E-J-194: Dynamic Tumor Tracking End-To-End Testing Using a 4D Thorax Phantom and EBT3 Films
Su, Z; Wu, J; Li, Z; Mamalui-Hunter, M
2014-06-01
Purpose: To quantify the Vero linac dosimetric accuracy of the tumor dynamic tracking treatment using EBT3 film embedded in a 4D thorax phantom. Methods: A dynamic thorax phantom with tissue equivalent materials and a film insert were used in this study. The thorax phantom was scanned in 4DCT mode with a viscoil embedded in its film insert composed of lung equivalent material. Dynamic tracking planning was performed using the 50% phase CT set with 5 conformal beams at gantry angles of 330, 15, 60, 105 and 150 degrees. Each field is a 3cm by 3cm square centered at viscoil since there was no solid mass target. Total 3 different 1–2cos4 motion profiles were used with varied motion magnitude and cycle frequency. Before treatment plan irradiation, a 4D motion model of the target was established using a series of acquired fluoroscopic images and infrared markers motion positions. During irradiation, fluoroscopic image monitoring viscoil motion was performed to verify model validity. The irradiated films were scanned and the dose maps were compared to the planned Monte Carlo dose distributions. Gamma analyses using 3%–3mm, 2%–3mm, 3%–2mm, 2%–2mm criteria were performed and presented. Results: For each motion pattern, a 4D motion model was built successfully and the target tracking performance was verified with fluoroscopic monitoring of the viscoil motion and its model predicted locations. The film gamma analysis showed the average pass rates among the 3 motion profiles are 98.14%, 96.2%, 91.3% and 85.61% for 3%–3mm, 2%–3mm, 3%–2mm, 2%–2mm criteria. Conclusion: Target dynamic tracking was performed using patient-like breathing patterns in a 4D thorax phantom with EBT3 film insert and a viscoil. There was excellent agreement between acquired and planned dose distributions for all three target motion patterns. This study performed end-to-end testing and verified the treatment accuracy of tumor dynamic tracking.
Impact of advanced technology microwave sounder data in the NCMRWF 4D-VAR data assimilation system
NASA Astrophysics Data System (ADS)
Rani, S. Indira; Srinivas, D.; Mallick, Swapan; George, John P.
2016-05-01
This study demonstrates the added benefits of assimilating the Advanced Technology Microwave Sounder (ATMS) radiances from the Suomi-NPP satellite in the NCMRWF Unified Model (NCUM). ATMS is a cross-track scanning microwave radiometer inherited the legacy of two very successful instrument namely, Advanced Microwave Sounding Unit-A (AMSU-A) and Microwave Humidity Sounder (MHS). ATMS has 22 channels: 11 temperature sounding channels around 50-60 GHz oxygen band and 6 moisture sounding channels around the 183GHz water vapour band in addition to 5 channels sensitive to the surface in clear conditions, or to water vapour, rain, and cloud when conditions are not clear (at 23, 31, 50, 51 and 89 GHz). Before operational assimilation of any new observation by NWP centres it is standard practice to assess data quality with respect to NWP model background (short-forecast) fields. Quality of all channels is estimated against the model background and the biases are computed and compared against that from the similar observations. The impact of the ATMS data on global analyses and forecasts is tested by adding the ATMS data in the NCUM Observation Processing system (OPS) and 4D-Var variational assimilation (VAR) system. This paper also discusses the pre-operational numerical experiments conducted to assess the impact of ATMS radiances in the NCUM assimilation system. It is noted that the performance of ATMS is stable and it contributes to the performance of the model, complimenting observations from other instruments.
NASA Astrophysics Data System (ADS)
Zhai, G.; Shirzaei, M.
2015-12-01
The Kilauea volcano, Hawaii Island, is one of the most active volcanoes worldwide. Its complex system, including magma reservoirs and rift zones, provides a unique opportunity to investigate the dynamics of magma transport and supply. The models explaining the system are yet limited to the first order analytical solutions with fixed geometry. To obtain a 4D map of the volume changes at the Kilauea summit magmatic system (KSMS), we implement a novel geometry-free time-dependent inverse modeling scheme, using a distribution of point center of dilatations (PCDs). The model is constrained using high resolution surface deformation data, which are obtained through InSAR time series analysis of well populated SAR data sets acquired at two overlapping tracks of Envisat satellite during 2003 and 2011. Principal Component Analysis (PCA) of the 4D maps of volume change identifies five major active reservoir beneath Kilauea caldera. The southern caldera reservoir (SCR) gains volume slowly till 2006 before its rapid inflation during 2006 - mid-2007, followed by deflation until the start of re-inflation in mid-2010. Other reservoirs show episodic temporal correlation and anti-correlation with SCR. We found that the top-down relation between reservoirs at the Kilauea summit is not necessarily valid at all time scales. Identifying statistically significant PCDs through Chi-square test, we develop and apply a boundary element modeling scheme to solve for the volume change time series and complex geometry of the summit magmatic system. Availability of such models allows realistic estimates of volume change and associated seismic hazard and enhance the forecast models.
NASA Astrophysics Data System (ADS)
Morecroft, John
System dynamics is an approach for thinking about and simulating situations and organisations of all kinds and sizes by visualising how the elements fit together, interact and change over time. This chapter, written by John Morecroft, describes modern system dynamics which retains the fundamentals developed in the 1950s by Jay W. Forrester of the MIT Sloan School of Management. It looks at feedback loops and time delays that affect system behaviour in a non-linear way, and illustrates how dynamic behaviour depends upon feedback loop structures. It also recognises improvements as part of the ongoing process of managing a situation in order to achieve goals. Significantly it recognises the importance of context, and practitioner skills. Feedback systems thinking views problems and solutions as being intertwined. The main concepts and tools: feedback structure and behaviour, causal loop diagrams, dynamics, are practically illustrated in a wide variety of contexts from a hot water shower through to a symphony orchestra and the practical application of the approach is described through several real examples of its use for strategic planning and evaluation.
Cibis, Merih; Jarvis, Kelly; Markl, Michael; Rose, Michael; Rigsby, Cynthia; Barker, Alex J; Wentzel, Jolanda J
2015-09-18
Viscous dissipation inside Fontan circulation, a parameter associated with the exercise intolerance of Fontan patients, can be derived from computational fluid dynamics (CFD) or 4D flow MRI velocities. However, the impact of spatial resolution and measurement noise on the estimation of viscous dissipation is unclear. Our aim was to evaluate the influence of these parameters on viscous dissipation calculation. Six Fontan patients underwent whole heart 4D flow MRI. Subject-specific CFD simulations were performed. The CFD velocities were down-sampled to isotropic spatial resolutions of 0.5mm, 1mm, 2mm and to MRI resolution. Viscous dissipation was compared between (1) high resolution CFD velocities, (2) CFD velocities down-sampled to MRI resolution, (3) down-sampled CFD velocities with MRI mimicked noise levels, and (4) in-vivo 4D flow MRI velocities. Relative viscous dissipation between subjects was also calculated. 4D flow MRI velocities (15.6 ± 3.8 cm/s) were higher, although not significantly different than CFD velocities (13.8 ± 4.7 cm/s, p=0.16), down-sampled CFD velocities (12.3 ± 4.4 cm/s, p=0.06) and the down-sampled CFD velocities with noise (13.2 ± 4.2 cm/s, p=0.06). CFD-based viscous dissipation (0.81 ± 0.55 mW) was significantly higher than those based on down-sampled CFD (0.25 ± 0.19 mW, p=0.03), down-sampled CFD with noise (0.49 ± 0.26 mW, p=0.03) and 4D flow MRI (0.56 ± 0.28 mW, p=0.06). Nevertheless, relative viscous dissipation between different subjects was maintained irrespective of resolution and noise, suggesting that comparison of viscous dissipation between patients is still possible. PMID:26298492
Constrained reconstructions for 4D intervention guidance.
Kuntz, J; Flach, B; Kueres, R; Semmler, W; Kachelriess, M; Bartling, S
2013-05-21
Image-guided interventions are an increasingly important part of clinical minimally invasive procedures. However, up to now they cannot be performed under 4D (3D + time) guidance due to the exceedingly high x-ray dose. In this work we investigate the applicability of compressed sensing reconstructions for highly undersampled CT datasets combined with the incorporation of prior images in order to yield low dose 4D intervention guidance. We present a new reconstruction scheme prior image dynamic interventional CT (PrIDICT) that accounts for specific image features in intervention guidance and compare it to PICCS and ASD-POCS. The optimal parameters for the dose per projection and the numbers of projections per reconstruction are determined in phantom simulations and measurements. In vivo experiments in six pigs are performed in a cone-beam CT; measured doses are compared to current gold-standard intervention guidance represented by a clinical fluoroscopy system. Phantom studies show maximum image quality for identical overall doses in the range of 14 to 21 projections per reconstruction. In vivo studies reveal that interventional materials can be followed in 4D visualization and that PrIDICT, compared to PICCS and ASD-POCS, shows superior reconstruction results and fewer artifacts in the periphery with dose in the order of biplane fluoroscopy. These results suggest that 4D intervention guidance can be realized with today's flat detector and gantry systems using the herein presented reconstruction scheme.
Constrained reconstructions for 4D intervention guidance
NASA Astrophysics Data System (ADS)
Kuntz, J.; Flach, B.; Kueres, R.; Semmler, W.; Kachelrieß, M.; Bartling, S.
2013-05-01
Image-guided interventions are an increasingly important part of clinical minimally invasive procedures. However, up to now they cannot be performed under 4D (3D + time) guidance due to the exceedingly high x-ray dose. In this work we investigate the applicability of compressed sensing reconstructions for highly undersampled CT datasets combined with the incorporation of prior images in order to yield low dose 4D intervention guidance. We present a new reconstruction scheme prior image dynamic interventional CT (PrIDICT) that accounts for specific image features in intervention guidance and compare it to PICCS and ASD-POCS. The optimal parameters for the dose per projection and the numbers of projections per reconstruction are determined in phantom simulations and measurements. In vivo experiments in six pigs are performed in a cone-beam CT; measured doses are compared to current gold-standard intervention guidance represented by a clinical fluoroscopy system. Phantom studies show maximum image quality for identical overall doses in the range of 14 to 21 projections per reconstruction. In vivo studies reveal that interventional materials can be followed in 4D visualization and that PrIDICT, compared to PICCS and ASD-POCS, shows superior reconstruction results and fewer artifacts in the periphery with dose in the order of biplane fluoroscopy. These results suggest that 4D intervention guidance can be realized with today’s flat detector and gantry systems using the herein presented reconstruction scheme.
Gelfond, O. A.; Vasiliev, M. A.
2015-03-15
Interactions of massless fields of all spins in four dimensions with currents of any spin are shown to result from a solution of the linear problem that describes a gluing between a rank-one (massless) system and a rank-two (current) system in the unfolded dynamics approach. Since the rank-two system is dual to a free rank-one higher-dimensional system that effectively describes conformal fields in six space-time dimensions, the constructed system can be interpreted as describing a mixture between linear conformal fields in four and six dimensions. An interpretation of the obtained results in the spirit of the AdS/CFT correspondence is discussed.
SU-D-207-03: Development of 4D-CBCT Imaging System with Dual Source KV X-Ray Tubes
Nakamura, M; Ishihara, Y; Matsuo, Y; Ueki, N; Iizuka, Y; Mizowaki, T; Hiraoka, M
2015-06-15
Purpose: The purposes of this work are to develop 4D-CBCT imaging system with orthogonal dual source kV X-ray tubes, and to determine the imaging doses from 4D-CBCT scans. Methods: Dual source kV X-ray tubes were used for the 4D-CBCT imaging. The maximum CBCT field of view was 200 mm in diameter and 150 mm in length, and the imaging parameters were 110 kV, 160 mA and 5 ms. The rotational angle was 105°, the rotational speed of the gantry was 1.5°/s, the gantry rotation time was 70 s, and the image acquisition interval was 0.3°. The observed amplitude of infrared marker motion during respiration was used to sort each image into eight respiratory phase bins. The EGSnrc/BEAMnrc and EGSnrc/DOSXYZnrc packages were used to simulate kV X-ray dose distributions of 4D-CBCT imaging. The kV X-ray dose distributions were calculated for 9 lung cancer patients based on the planning CT images with dose calculation grid size of 2.5 x 2.5 x 2.5 mm. The dose covering a 2-cc volume of skin (D2cc), defined as the inner 5 mm of the skin surface with the exception of bone structure, was assessed. Results: A moving object was well identified on 4D-CBCT images in a phantom study. Given a gantry rotational angle of 105° and the configuration of kV X-ray imaging subsystems, both kV X-ray fields overlapped at a part of skin surface. The D2cc for the 4D-CBCT scans was in the range 73.8–105.4 mGy. Linear correlation coefficient between the 1000 minus averaged SSD during CBCT scanning and D2cc was −0.65 (with a slope of −0.17) for the 4D-CBCT scans. Conclusion: We have developed 4D-CBCT imaging system with dual source kV X-ray tubes. The total imaging dose with 4D-CBCT scans was up to 105.4 mGy.
Advances in 4D radiation therapy for managing respiration: part I - 4D imaging.
Hugo, Geoffrey D; Rosu, Mihaela
2012-12-01
Techniques for managing respiration during imaging and planning of radiation therapy are reviewed, concentrating on free-breathing (4D) approaches. First, we focus on detailing the historical development and basic operational principles of currently-available "first generation" 4D imaging modalities: 4D computed tomography, 4D cone beam computed tomography, 4D magnetic resonance imaging, and 4D positron emission tomography. Features and limitations of these first generation systems are described, including necessity of breathing surrogates for 4D image reconstruction, assumptions made in acquisition and reconstruction about the breathing pattern, and commonly-observed artifacts. Both established and developmental methods to deal with these limitations are detailed. Finally, strategies to construct 4D targets and images and, alternatively, to compress 4D information into static targets and images for radiation therapy planning are described.
Advances in 4D Radiation Therapy for Managing Respiration: Part I – 4D Imaging
Hugo, Geoffrey D.; Rosu, Mihaela
2014-01-01
Techniques for managing respiration during imaging and planning of radiation therapy are reviewed, concentrating on free-breathing (4D) approaches. First, we focus on detailing the historical development and basic operational principles of currently-available “first generation” 4D imaging modalities: 4D computed tomography, 4D cone beam computed tomography, 4D magnetic resonance imaging, and 4D positron emission tomography. Features and limitations of these first generation systems are described, including necessity of breathing surrogates for 4D image reconstruction, assumptions made in acquisition and reconstruction about the breathing pattern, and commonly-observed artifacts. Both established and developmental methods to deal with these limitations are detailed. Finally, strategies to construct 4D targets and images and, alternatively, to compress 4D information into static targets and images for radiation therapy planning are described. PMID:22784929
NASA Astrophysics Data System (ADS)
Kwon, Oh-Hoon; Zewail, Ahmed H.
2010-06-01
Electron tomography provides three-dimensional (3D) imaging of noncrystalline and crystalline equilibrium structures, as well as elemental volume composition, of materials and biological specimens, including those of viruses and cells. We report the development of 4D electron tomography by integrating the fourth dimension (time resolution) with the 3D spatial resolution obtained from a complete tilt series of 2D projections of an object. The different time frames of tomograms constitute a movie of the object in motion, thus enabling studies of nonequilibrium structures and transient processes. The method was demonstrated using carbon nanotubes of a bracelet-like ring structure for which 4D tomograms display different modes of motion, such as breathing and wiggling, with resonance frequencies up to 30 megahertz. Applications can now make use of the full space-time range with the nanometer-femtosecond resolution of ultrafast electron tomography.
NASA Astrophysics Data System (ADS)
Sydney Gladman, A.; Matsumoto, Elisabetta A.; Nuzzo, Ralph G.; Mahadevan, L.; Lewis, Jennifer A.
2016-04-01
Shape-morphing systems can be found in many areas, including smart textiles, autonomous robotics, biomedical devices, drug delivery and tissue engineering. The natural analogues of such systems are exemplified by nastic plant motions, where a variety of organs such as tendrils, bracts, leaves and flowers respond to environmental stimuli (such as humidity, light or touch) by varying internal turgor, which leads to dynamic conformations governed by the tissue composition and microstructural anisotropy of cell walls. Inspired by these botanical systems, we printed composite hydrogel architectures that are encoded with localized, anisotropic swelling behaviour controlled by the alignment of cellulose fibrils along prescribed four-dimensional printing pathways. When combined with a minimal theoretical framework that allows us to solve the inverse problem of designing the alignment patterns for prescribed target shapes, we can programmably fabricate plant-inspired architectures that change shape on immersion in water, yielding complex three-dimensional morphologies.
Gladman, A Sydney; Matsumoto, Elisabetta A; Nuzzo, Ralph G; Mahadevan, L; Lewis, Jennifer A
2016-04-01
Shape-morphing systems can be found in many areas, including smart textiles, autonomous robotics, biomedical devices, drug delivery and tissue engineering. The natural analogues of such systems are exemplified by nastic plant motions, where a variety of organs such as tendrils, bracts, leaves and flowers respond to environmental stimuli (such as humidity, light or touch) by varying internal turgor, which leads to dynamic conformations governed by the tissue composition and microstructural anisotropy of cell walls. Inspired by these botanical systems, we printed composite hydrogel architectures that are encoded with localized, anisotropic swelling behaviour controlled by the alignment of cellulose fibrils along prescribed four-dimensional printing pathways. When combined with a minimal theoretical framework that allows us to solve the inverse problem of designing the alignment patterns for prescribed target shapes, we can programmably fabricate plant-inspired architectures that change shape on immersion in water, yielding complex three-dimensional morphologies.
Gladman, A Sydney; Matsumoto, Elisabetta A; Nuzzo, Ralph G; Mahadevan, L; Lewis, Jennifer A
2016-04-01
Shape-morphing systems can be found in many areas, including smart textiles, autonomous robotics, biomedical devices, drug delivery and tissue engineering. The natural analogues of such systems are exemplified by nastic plant motions, where a variety of organs such as tendrils, bracts, leaves and flowers respond to environmental stimuli (such as humidity, light or touch) by varying internal turgor, which leads to dynamic conformations governed by the tissue composition and microstructural anisotropy of cell walls. Inspired by these botanical systems, we printed composite hydrogel architectures that are encoded with localized, anisotropic swelling behaviour controlled by the alignment of cellulose fibrils along prescribed four-dimensional printing pathways. When combined with a minimal theoretical framework that allows us to solve the inverse problem of designing the alignment patterns for prescribed target shapes, we can programmably fabricate plant-inspired architectures that change shape on immersion in water, yielding complex three-dimensional morphologies. PMID:26808461
4-D OCT in Developmental Cardiology
NASA Astrophysics Data System (ADS)
Jenkins, Michael W.; Rollins, Andrew M.
Although strong evidence exists to suggest that altered cardiac function can lead to CHDs, few studies have investigated the influential role of cardiac function and biophysical forces on the development of the cardiovascular system due to a lack of proper in vivo imaging tools. 4-D imaging is needed to decipher the complex spatial and temporal patterns of biomechanical forces acting upon the heart. Numerous solutions over the past several years have demonstrated 4-D OCT imaging of the developing cardiovascular system. This chapter will focus on these solutions and explain their context in the evolution of 4-D OCT imaging. The first sections describe the relevant techniques (prospective gating, direct 4-D imaging, retrospective gating), while later sections focus on 4-D Doppler imaging and measurements of force implementing 4-D OCT Doppler. Finally, the techniques are summarized, and some possible future directions are discussed.
NASA Astrophysics Data System (ADS)
Ford, Steven J.; Deán-Ben, Xosé L.; Razansky, Daniel
2015-03-01
The fast heart rate (~7 Hz) of the mouse makes cardiac imaging and functional analysis difficult when studying mouse models of cardiovascular disease, and cannot be done truly in real-time and 3D using established imaging modalities. Optoacoustic imaging, on the other hand, provides ultra-fast imaging at up to 50 volumetric frames per second, allowing for acquisition of several frames per mouse cardiac cycle. In this study, we combined a recently-developed 3D optoacoustic imaging array with novel analytical techniques to assess cardiac function and perfusion dynamics of the mouse heart at high, 4D spatiotemporal resolution. In brief, the heart of an anesthetized mouse was imaged over a series of multiple volumetric frames. In another experiment, an intravenous bolus of indocyanine green (ICG) was injected and its distribution was subsequently imaged in the heart. Unique temporal features of the cardiac cycle and ICG distribution profiles were used to segment the heart from background and to assess cardiac function. The 3D nature of the experimental data allowed for determination of cardiac volumes at ~7-8 frames per mouse cardiac cycle, providing important cardiac function parameters (e.g., stroke volume, ejection fraction) on a beat-by-beat basis, which has been previously unachieved by any other cardiac imaging modality. Furthermore, ICG distribution dynamics allowed for the determination of pulmonary transit time and thus additional quantitative measures of cardiovascular function. This work demonstrates the potential for optoacoustic cardiac imaging and is expected to have a major contribution toward future preclinical studies of animal models of cardiovascular health and disease.
4D human body posture estimation based on a motion capture system and a multi-rigid link model.
Yoshikawa, Naoya; Suzuki, Yasuyuki; Ozaki, Wataru; Yamamoto, Tomohisa; Nomura, Taishin
2012-01-01
Human motion analysis in various fields such as neurophysiology, clinical medicine, and sports sciences utilizes a multi-rigid link model of a human body for considering kinetics by solving inverse dynamics of a motion, in which a motion capture system with reflective markers are often used to measure the motion, and then the obtained motion are mapped onto the multi-rigid link model. However, algorithms for such a mapping from spatio-temporal positions of the markers to the corresponding posture of the model are not always fully disclosed. Moreover, a common difficulty for such algorithms is an error caused by displacements of the markers attached on the body surface, referred to as the skin motion error. In this study, we developed a simple algorithm that maps positions of the markers to the corresponding posture of a rigid link model, and examined accuracy of the algorithm by evaluating quantitatively differences between the measured and the estimated posture. We also analyzed the skin motion error. It is shown that magnitude of the error was determined not only by the amplitude of the skin motion, but also by the direction of the marker displacement relative to the frame of reference attached to each segment of the body.
Vali, Faisal S; Hsi, Alex; Cho, Paul; Parsai, Homayon; Garver, Elizabeth; Garza, Richard
2008-11-06
The Calypso 4D Localization System records prostate motion continuously during radiation treatment. It stores the data across thousands of Excel files. We developed Javascript (JScript) libraries for Windows Script Host (WSH) that use ActiveX Data Objects, OLE Automation and SQL to statistically analyze the data and display the results as a comprehensible Excel table. We then leveraged these libraries in other research to perform vector math on data spread across multiple access databases.
Joint CO2 state and flux estimation with the 4D-Var system EURAD-IM
NASA Astrophysics Data System (ADS)
Klimpt, Johannes; Elbern, Hendrik
2016-04-01
Atmospheric CO2 inversion studies seek to improve CO2 surface-atmosphere fluxes with the usage of adjoint transport models and CO2 concentration measurements. Terrestrial CO2 fluxes -anthropogenic emissions, photosynthesis, and respiration- bear large spatial and temporal variability and are highly uncertain. Additionally to the high uncertainty of the three CO2 fluxes itself, regional inversion studies suffer from uncertainty of the boundary layer height and atmospheric transport especially during night, leading to uncertainty of atmospheric CO2 mixing ratios during sunrise. This study assesses the potential of the 4-dimensional variational (4D-Var) method to estimate CO2 fluxes and atmospheric CO2 concentrations jointly at each grid cell on a regional scale. Identical twin experiments are executed with the nested EURopean Air pollution Dispersion-Inverse Model (EURAD-IM) with 5 km resolution in Central Europe with synthetic half hourly measurements from eleven concentration towers. The assimilation window is chosen to start from sunrise for 12 hours. We find that joint estimation of CO2 fluxes and initial states requires a more careful balance of the background error covariance matrices but enables a more detailed analysis of atmospheric CO2 and the surface-atmosphere fluxes.
NASA Astrophysics Data System (ADS)
Köpken, Christina; Kelly, Graeme; Thépaut, Jean-Noël
2004-07-01
The direct assimilation of water vapour (WV) clear-sky radiances (CSRs) from geostationary satellites within the ECMWF four-dimensional variational assimilation (4D-Var) became operational on 9 April 2002 with the assimilation of radiances from Meteosat-7. To extend the coverage provided by geostationary radiances, the derivation of a similar CSR product from the Geostationary Operational Environmental Satellites GOES-W and GOES-E was initiated and since 14 January 2003 these data have been operationally assimilated as well. This paper discusses results from the pre-operational impact experiments using Meteosat-7 and the subsequent operational implementation of the WV radiance assimilation. The pre-operational data monitoring of the CSRs shows contamination of certain time slots caused by intruding solar stray light and a certain degree of cloud influence present in the CSR. Data quality control is introduced to exclude affected data. When assimilated, the Meteosat WV CSRs correct the upper-tropospheric humidity field in areas of known model problems. While the analysis draws well to Meteosat data, the fit to other conventional observations does not degrade, and the fit to other satellite observations is noticeably improved. This is visible in statistics for the assimilated HIRS-12 as well as for passive Advanced Microwave Sounding Unit B (AMSUB) radiances, both in the pre-operational experiments and in the operational assimilation cycle. The impact on forecast quality is slightly positive to neutral for different areas of the globe. In some experiments a positive impact on upper-level wind fields (around 200 hPa) is seen, especially in the tropics. A relatively large sensitivity is noted of the mean increments and also forecast scores to the bias correction.
NASA Astrophysics Data System (ADS)
Wang, Yang; Goldin, Jonathan G.; Abtin, Fereidoun G.; Brown, Matt; McNitt-Gray, Mike
2008-03-01
The purpose of this study is to test a new dynamic Perfusion-CT imaging protocol in an animal model and investigate the feasibility of quantifying perfusion of lung parenchyma to perform functional analysis from 4D CT image data. A novel perfusion-CT protocol was designed with 25 scanning time points: the first at baseline and 24 scans after a bolus injection of contrast material. Post-contrast CT scanning images were acquired with a high sampling rate before the first blood recirculation and then a relatively low sampling rate until 10 minutes after administrating contrast agent. Lower radiation techniques were used to keep the radiation dose to an acceptable level. 2 Yorkshire swine with pulmonary emboli underwent this perfusion- CT protocol at suspended end inspiration. The software tools were designed to measure the quantitative perfusion parameters (perfusion, permeability, relative blood volume, blood flow, wash-in & wash-out enhancement) of voxel or interesting area of lung. The perfusion values were calculated for further lung functional analysis and presented visually as contrast enhancement maps for the volume being examined. The results show increased CT temporal sampling rate provides the feasibility of quantifying lung function and evaluating the pulmonary emboli. Differences between areas with known perfusion defects and those without perfusion defects were observed. In conclusion, the techniques to calculate the lung perfusion on animal model have potential application in human lung functional analysis such as evaluation of functional effects of pulmonary embolism. With further study, these techniques might be applicable in human lung parenchyma characterization and possibly for lung nodule characterization.
Battaglia, Maurizio; Gottsmann, J.; Carbone, D.; Fernandez, J.
2008-01-01
Time-dependent gravimetric measurements can detect subsurface processes long before magma flow leads to earthquakes or other eruption precursors. The ability of gravity measurements to detect subsurface mass flow is greatly enhanced if gravity measurements are analyzed and modeled with ground-deformation data. Obtaining the maximum information from microgravity studies requires careful evaluation of the layout of network benchmarks, the gravity environmental signal, and the coupling between gravity changes and crustal deformation. When changes in the system under study are fast (hours to weeks), as in hydrothermal systems and restless volcanoes, continuous gravity observations at selected sites can help to capture many details of the dynamics of the intrusive sources. Despite the instrumental effects, mainly caused by atmospheric temperature, results from monitoring at Mt. Etna volcano show that continuous measurements are a powerful tool for monitoring and studying volcanoes.Several analytical and numerical mathematical models can beused to fit gravity and deformation data. Analytical models offer a closed-form description of the volcanic source. In principle, this allows one to readily infer the relative importance of the source parameters. In active volcanic sites such as Long Valley caldera (California, U.S.A.) and Campi Flegrei (Italy), careful use of analytical models and high-quality data sets has produced good results. However, the simplifications that make analytical models tractable might result in misleading volcanological inter-pretations, particularly when the real crust surrounding the source is far from the homogeneous/ isotropic assumption. Using numerical models allows consideration of more realistic descriptions of the sources and of the crust where they are located (e.g., vertical and lateral mechanical discontinuities, complex source geometries, and topography). Applications at Teide volcano (Tenerife) and Campi Flegrei demonstrate the
NASA Astrophysics Data System (ADS)
Munro, Rosemary; Köpken, Christina; Kelly, Graeme; Thépaut, Jean-Noël; Saunders, Roger
2004-07-01
This paper describes the direct assimilation of water vapour (WV) clear-sky radiance (CSR) data from geostationary satellites within the context of the ECMWF four-dimensional variational assimilation (4D-Var) system. The assimilation of Meteosat-7 WV CSR data became operational on 9 April 2002. As 4D-Var includes a time dimension, the high temporal resolution of the geostationary radiance data can be exploited to provide information not only on the upper-tropospheric humidity but also on the upper-tropospheric wind field. The data assimilated have a spatial resolution of approximately 80 km and a time resolution of 1 hour. Extensive pre-operational monitoring of the CSR data has been carried out, showing a systematic warm bias of approximately 2-3 K in the Meteosat WV CSR data compared to radiances simulated from model first-guess fields. The systematic biases between the brightness temperatures derived from the model and the observations are investigated and compared to other satellite radiance data. For assimilation purposes this is accounted for by using a bias correction based on a statistical regression. The monitoring also shows contamination of certain time slots caused by intruding solar stray light and a certain degree of residual cloud contamination present in the CSR. Data quality control is introduced to exclude affected data. Initial single-cycle 3D-Var with first guess at appropriate time and 4D-Var experiments demonstrate both the direct and indirect effects of the Meteosat WV CSR data on the model fields, particularly of humidity and wind. The operational implementation of the assimilation of the Meteosat WV CSR data, including results from pre-operational experiments and forecast impacts, is discussed in a companion paper.
Lins, Vilma S; Santos, Honório R; Gonçalves, Manoel C
2007-01-01
The use of herbicides is a common and intensive practice in no tillage systems. The herbicides can influence, directly or indirectly, the population of edaphic arthropods. Collembola is a group that functions as a bio-indicator of soil conditions. The degree of abundance and diversity of Collembola provides the level of soil disturbance provoked by agricultural practices. This experiment was designed to compare the influence of herbicides on the population fluctuation of Collembola in a no-till soil preparation system. The work was conducted in a non irrigated no-till area at the Núcleo Experimental de Ciências Agrárias of the Universidade Federal de Mato Grosso do Sul (UFMS), Campus de Dourados, in soil planted with corn as a surface covering, during the period of December, 2002 to December, 2003. The data were analyzed according to a completely randomized model, in a split plot design. The plots received four types of herbicides: glyphosate, atrazine, 2,4-D and nicosulfuron. A fifth plot did not receive any herbicide (control), for a total of five treatment types. The sub plots were represented by their collection times (10, 20, 30 and 40 days after the herbicide applications). Both the type of herbicide and the time of data sampling influenced the Collembola population fluctuaction. The treatments with atrazine and 2,4-D caused the most reduction of the population of Collembola, depending on the time of application.
Suzuki, Naoki; Hattori, Asaki
2012-01-01
Laparoscopic surgery has been used for various areas of abdominal cavity. However, the laparoscope has limitation of its field of view and mobility. Our aim is to develop a new video camera system that acquires multiple viewpoints in the abdominal cavity. We designed a camera array that consisted of eight small camera modules. The camera array can change its shape so that it can be inserted into the abdominal cavity through trocar. Surgeon can change the viewpoint by switching camera output without physically moving the camera. Using eight camera's images, we also tried to reconstruct 3D textured shape of the surgery field.
NASA Astrophysics Data System (ADS)
Bunz, S.; Hurter, S.; Plaza-Faverola, A. A.; Mienert, J.
2014-12-01
Active gas venting occurs on the Vestnesa Ridge, an elongated sediment drift north of the Molloy Transform and just east of the Molloy Ridge, one of the shortest segments of the slow spreading North-Atlantic Ridge system. The crest of the Vestnesa Ridge at water depth between 1200-1300 m is pierced with fluid-flow features. Seafloor pockmarks vary in size up to 1 km in diameter with significant morphological features consisting of small ridges, diapiric structures and small pits. Detailed hydro-acoustic surveying shows that gas mostly emanates from the small-scale pits, where also hydrates have been recovered by sediment sampling. High-resolution P-Cable 3D seismic data acquired in 2012 show vertical focused fluid flow features beneath the seafloor pockmarks. These co-called chimneys extend down to the free-gas zone underneath a bottom-simulating reflection (BSR). Here, they link up with small fault systems that might provide pathways to the deeper subsurface. The chimney features show a high variability in their acoustic characteristics with alternating blanked or masked zones and high-amplitude anomalies scattered through the whole vertical extent of the chimneys. The amplitude anomalies indicate high-impedance contrasts due to the likely presence of gas or a high-velocity material like gas hydrates or carbonates. In most cases, the high-amplitude anomalies line up along specific vertical pathways that connect nicely with the small-scale pits at the surface where gas bubbles seep from the seafloor. We re-acquired the 3D seismic survey in 2013 for time-lapse seismic studies in order to better understand the origin of the amplitude anomalies and in order to track potentially migrating gas fronts up along the chimney structure. The time-lapse seismic analysis indicates several areas, where gas migration may have led to changes in acoustic properties of the subsurface. These areas are located along chimney structures and the BSR. This work provides a basis for better
NASA Astrophysics Data System (ADS)
Bromiley, G.; Berg, M.; Le Godec, Y.; Mezouar, N.; Atwood, R. C.; Phillipe, J.
2015-12-01
Although core formation was a key stage in the evolution of terrestrial planets, the physical processes which resulted in segregation of iron and silicate remain poorly understood. Formation of a silicate magma oceans provides an obvious mechanism for segregation of core-forming liquids, although recent work has strengthened arguments for a complex, multi-stage model of core formation. Extreme pressure1 and the effects of deformation2 have both been shown to promote percolation of Fe-rich melts in a solid silicate matrix, providing mechanisms for early, low temperature core-formation. However, the efficiency of these processes remains untested and we lack meaningful experimental data on resulting melt segregation velocities. Arguments regarding the efficiency of core formation through percolation of Fe-rich melts in solid silicate are based on simple, empirical models. Here, we review textural evidence from recent experiments which supports early core formation driven by deformation-aided percolation of Fe-rich melts. We then present results of novel in-situ synchrotron studies designed to provide time-resolved 3-D microimaging of percolating melt in model systems under extreme conditions. Under low strain rates characteristic of deformation-aided core formation, segregation of metallic (core-forming) melts by percolation is driven by stress gradients. This is expected to ultimately result in channelization and efficient segregation of melts noted in high-strain, low pressure experiments3. In-situ visualization also demonstrates that percolation of viscous metallic melts is surprisingly rapid. A combination of melt channelization and hydraulic fracture results in rapid, episodic melt migration, even over the limited time scale of experiments. The efficiency of this process depends strongly on the geometry of the melt network and is scaled to grain size in the matrix. We use both in-situ visualization and high-resolution ex-situ analysis to provide accurate
Baker, Joseph; Kungl, Ann-Marie; Pabst, Jan; Strauß, Bernd; Büsch, Dirk; Schorer, Jörg
2013-01-01
Over the past decade a small evidence base has highlighted the potential importance of seemingly innocuous variables related to one's hands, such as hand dominance and the relative length of the second and fourth digits (2D:4D ratio), to success in sport. This study compared 2D:4D digit ratio and handedness among handball players selected to advance in a national talent development system with those not selected. Participants included 480 youth handball players (240 females and 240 males) being considered as part of the talent selection programme for the German Youth National team. Hand dominance and digit ratio were compared to age-matched control data using standard t-tests. There was a greater proportion of left-handers compared to the normal population in males but not in females. There was also a lower digit ratio in both females and males. However, there were no differences between those selected for the next stage of talent development and those not selected on either handedness or digit ratio. These results add support for general effects for both digit ratio and handedness in elite handball; however, these factors seem inadequate to explain talent selection decisions at this level.
Marants, R; Vandervoort, E; Cygler, J E
2014-08-15
Introduction: RADPOS 4D dosimetry system consists of a microMOSFET dosimeter combined with an electromagnetic positioning sensor, which allows for performing real-time dose and position measurements simultaneously. In this report the use of RADPOS as an independent quality assurance (QA) tool during CyberKnife 4D radiotherapy treatment is described. In addition to RADPOS, GAFCHROMIC® films were used for simultaneous dose measurement. Methods: RADPOS and films were calibrated in a Solid Water® phantom at 1.5 cm depth, SAD= 80 cm, using 60 mm cone. CT based treatment plan was created for a Solid Water® breast phantom containing metal fiducials and RADPOS probe. Dose calculations were performed using iPlan pencil beam algorithm. Before the treatment delivery, GAFCHROMIC® film was inserted inside the breast phantom, next to the RADPOS probe. Then the phantom was positioned on the chest platform of the QUASAR, to which Synchrony LED optical markers were also attached. Position logging began for RADPOS and the Synchrony tracking system, the QUASAR motion was initiated and the treatment was delivered. Results: RADPOS position measurements very closely matched the LED marker positions recorded by the Synchrony camera tracking system. The RADPOS measured dose was 2.5% higher than the average film measured dose, which is within the experimental uncertainties. Treatment plan calculated dose was 4.1 and 1.6% lower than measured by RADPOS and film, respectively. This is most likely due to the inferior nature of the dose calculation algorithm. Conclusions: Our study demonstrates that RADPOS system is a useful tool for independent QA of CyberKnife treatments.
NASA Astrophysics Data System (ADS)
Yumimoto, K.; Takemura, T.
2013-11-01
We present an aerosol data assimilation system based on a global aerosol climate model (SPRINTARS - Spectral Radiation-Transport Model for Aerosol Species) and a four-dimensional variational data assimilation method (4D-Var). Its main purposes are to optimize emission estimates, improve composites, and obtain the best estimate of the radiative effects of aerosols in conjunction with observations. To reduce the huge computational cost caused by the iterative integrations in the models, we developed an offline model and a corresponding adjoint model, which are driven by pre-calculated meteorological, land, and soil data. The offline and adjoint model shortened the computational time of the inner loop by more than 30%. By comparing the results with a 1 yr simulation from the original online model, the consistency of the offline model was verified, with correlation coefficient R > 0.97 and absolute value of normalized mean bias NMB < 7% for the natural aerosol emissions and aerosol optical thickness (AOT) of individual aerosol species. Deviations between the offline and original online models are mainly associated with the time interpolation of the input meteorological variables in the offline model; the smaller variability and difference in the wind velocity near the surface and relative humidity cause negative and positive biases in the wind-blown aerosol emissions and AOTs of hygroscopic aerosols, respectively. The feasibility and capability of the developed system for aerosol inverse modelling was demonstrated in several inversion experiments based on the observing system simulation experiment framework. In the experiments, we used the simulated observation data sets of fine- and coarse-mode AOTs from sun-synchronous polar orbits to investigate the impact of the observational frequency (number of satellites) and coverage (land and ocean), and assigned aerosol emissions to control parameters. Observations over land have a notably positive impact on the performance
Los Alamos National Laboratory 4D Database
Atencio, Julian J.
2014-05-02
4D is an integrated development platform - a single product comprised of the components you need to create and distribute professional applications. You get a graphical design environment, SQL database, a programming language, integrated PHP execution, HTTP server, application server, executable generator, and much more. 4D offers multi-platform development and deployment, meaning whatever you create on a Mac can be used on Windows, and vice-versa. Beyond productive development, 4D is renowned for its great flexibility in maintenance and modification of existing applications, and its extreme ease of implementation in its numerous deployment options. Your professional application can be put into production more quickly, at a lower cost, and will always be instantly scalable. 4D makes it easy, whether you're looking to create a classic desktop application, a client-server system, a distributed solution for Web or mobile clients - or all of the above!
4D Confocal Imaging of Yeast Organelles.
Day, Kasey J; Papanikou, Effrosyni; Glick, Benjamin S
2016-01-01
Yeast cells are well suited to visualizing organelles by 4D confocal microscopy. Typically, one or more cellular compartments are labeled with a fluorescent protein or dye, and a stack of confocal sections spanning the entire cell volume is captured every few seconds. Under appropriate conditions, organelle dynamics can be observed for many minutes with only limited photobleaching. Images are captured at a relatively low signal-to-noise ratio and are subsequently processed to generate movies that can be analyzed and quantified. Here, we describe methods for acquiring and processing 4D data using conventional scanning confocal microscopy. PMID:27631997
Abdominal and pancreatic motion correlation using 4D CT, 4D transponders, and a gating belt.
Betancourt, Ricardo; Zou, Wei; Plastaras, John P; Metz, James M; Teo, Boon-Keng; Kassaee, Alireza
2013-01-01
The correlation between the pancreatic and external abdominal motion due to respiration was investigated on two patients. These studies utilized four dimensional computer tomography (4D CT), a four dimensional (4D) electromagnetic transponder system, and a gating belt system. One 4D CT study was performed during simulation to quantify the pancreatic motion using computer tomography images at eight breathing phases. The motion under free breathing and breath-hold were analyzed for the 4D electromagnetic transponder system and the gating belt system during treatment. A linear curve was fitted for all data sets and correlation factors were evaluated between the 4D electromagnetic transponder system and the gating belt system data. The 4D CT study demonstrated a modest correlation between the external marker and the pancreatic motion with R-square values larger than 0.8 for the inferior-superior (inf-sup). Then, the relative pressure from the belt gating system correlated well with the 4D electromagnetic transponder system's motion in the anterior-posterior (ant-post) and the inf-post directions. These directions have a correlation value of -0.93 and 0.76, while the lateral only had a 0.03 correlation coefficient. Based on our limited study, external surrogates can be used as predictors of the pancreatic motion in the inf-sup and the ant-post directions. Although there is a low correlation on the lateral direction, its motion is significantly shorter. In conclusion, an appropriate treatment delivery can be used for pancreatic cancer when an internal tracking system, such as the 4D electromagnetic transponder system, is unavailable. PMID:23652242
Abdominal and pancreatic motion correlation using 4D CT, 4D transponders, and a gating belt.
Betancourt, Ricardo; Zou, Wei; Plastaras, John P; Metz, James M; Teo, Boon-Keng; Kassaee, Alireza
2013-05-06
The correlation between the pancreatic and external abdominal motion due to respiration was investigated on two patients. These studies utilized four dimensional computer tomography (4D CT), a four dimensional (4D) electromagnetic transponder system, and a gating belt system. One 4D CT study was performed during simulation to quantify the pancreatic motion using computer tomography images at eight breathing phases. The motion under free breathing and breath-hold were analyzed for the 4D electromagnetic transponder system and the gating belt system during treatment. A linear curve was fitted for all data sets and correlation factors were evaluated between the 4D electromagnetic transponder system and the gating belt system data. The 4D CT study demonstrated a modest correlation between the external marker and the pancreatic motion with R-square values larger than 0.8 for the inferior-superior (inf-sup). Then, the relative pressure from the belt gating system correlated well with the 4D electromagnetic transponder system's motion in the anterior-posterior (ant-post) and the inf-post directions. These directions have a correlation value of -0.93 and 0.76, while the lateral only had a 0.03 correlation coefficient. Based on our limited study, external surrogates can be used as predictors of the pancreatic motion in the inf-sup and the ant-post directions. Although there is a low correlation on the lateral direction, its motion is significantly shorter. In conclusion, an appropriate treatment delivery can be used for pancreatic cancer when an internal tracking system, such as the 4D electromagnetic transponder system, is unavailable.
NASA Astrophysics Data System (ADS)
Zhang, Kang; Kang, Jin U.
2011-03-01
We realized a real-time dual-mode standard/complex Fourier-domain optical coherence tomography (FD-OCT) system using graphics processing unit (GPU) accelerated 4D (3D+time) signal processing and visualization. For both standard and complex FD-OCT modes, the signal processing tasks were implemented on a dual-GPUs architecture that included λ-to-k spectral re-sampling, fast Fourier transform (FFT), modified Hilbert transform, logarithmic-scaling, and volume rendering. The maximum A-scan processing speeds achieved are >3,000,000 line/s for the standard 1024-pixel-FD-OCT, and >500,000 line/s for the complex 1024-pixel-FD-OCT. Multiple volumerendering of the same 3D data set were preformed and displayed with different view angles. The GPU-acceleration technique is highly cost-effective and can be easily integrated into most ultrahigh speed FD-OCT systems to overcome the 3D data processing and visualization bottlenecks.
Gokulan, Kuppan; Khare, Sangeeta; Rooney, Anthony W; Han, Jing; Lynne, Aaron M; Foley, Steven L
2013-01-01
Salmonella enterica serovar Heidelberg (S. Heidelberg) can cause foodborne illness in humans following the consumption of contaminated meat and poultry products. Recent studies from our laboratory have demonstrated that certain S. Heidelberg isolated from food-animal sources harbor multiple transmissible plasmids with genes that encode antimicrobial resistance, virulence and a VirB4/D4 type-IV secretion system. This study examines the potential role of these transmissible plasmids in bacterial uptake and survival in intestinal epithelial cells and macrophages, and the molecular basis of host immune system modulation that may be associated with disease progression. A series of transconjugant and transformant strains were developed with different combinations of the plasmids to determine the roles of the individual and combinations of plasmids on virulence. Overall the Salmonella strains containing the VirB/D4 T4SS plasmids entered and survived in epithelial cells and macrophages to a greater degree than those without the plasmid, even though they carried other plasmid types. During entry in macrophages, the VirB/D4 T4SS encoding genes are up-regulated in a time-dependent fashion. When the potential mechanisms for increased virulence were examined using an antibacterial Response PCR Array, the strain containing the T4SS down regulated several host innate immune response genes which likely contributed to the increased uptake and survival within macrophages and epithelial cells.
Stankovic, Zoran; Allen, Bradley D.; Garcia, Julio; Jarvis, Kelly B.
2014-01-01
Magnetic resonance imaging (MRI) has become an important tool for the clinical evaluation of patients with cardiovascular disease. Since its introduction in the late 1980s, 2-dimensional phase contrast MRI (2D PC-MRI) has become a routine part of standard-of-care cardiac MRI for the assessment of regional blood flow in the heart and great vessels. More recently, time-resolved PC-MRI with velocity encoding along all three flow directions and three-dimensional (3D) anatomic coverage (also termed ‘4D flow MRI’) has been developed and applied for the evaluation of cardiovascular hemodynamics in multiple regions of the human body. 4D flow MRI allows for the comprehensive evaluation of complex blood flow patterns by 3D blood flow visualization and flexible retrospective quantification of flow parameters. Recent technical developments, including the utilization of advanced parallel imaging techniques such as k-t GRAPPA, have resulted in reasonable overall scan times, e.g., 8-12 minutes for 4D flow MRI of the aorta and 10-20 minutes for whole heart coverage. As a result, the application of 4D flow MRI in a clinical setting has become more feasible, as documented by an increased number of recent reports on the utility of the technique for the assessment of cardiac and vascular hemodynamics in patient studies. A number of studies have demonstrated the potential of 4D flow MRI to provide an improved assessment of hemodynamics which might aid in the diagnosis and therapeutic management of cardiovascular diseases. The purpose of this review is to describe the methods used for 4D flow MRI acquisition, post-processing and data analysis. In addition, the article provides an overview of the clinical applications of 4D flow MRI and includes a review of applications in the heart, thoracic aorta and hepatic system. PMID:24834414
Zhang, Kang; Kang, Jin U
2010-05-24
We realized graphics processing unit (GPU) based real-time 4D (3D+time) signal processing and visualization on a regular Fourier-domain optical coherence tomography (FD-OCT) system with a nonlinear k-space spectrometer. An ultra-high speed linear spline interpolation (LSI) method for lambda-to-k spectral re-sampling is implemented in the GPU architecture, which gives average interpolation speeds of >3,000,000 line/s for 1024-pixel OCT (1024-OCT) and >1,400,000 line/s for 2048-pixel OCT (2048-OCT). The complete FD-OCT signal processing including lambda-to-k spectral re-sampling, fast Fourier transform (FFT) and post-FFT processing have all been implemented on a GPU. The maximum complete A-scan processing speeds are investigated to be 680,000 line/s for 1024-OCT and 320,000 line/s for 2048-OCT, which correspond to 1GByte processing bandwidth. In our experiment, a 2048-pixel CMOS camera running up to 70 kHz is used as an acquisition device. Therefore the actual imaging speed is camera- limited to 128,000 line/s for 1024-OCT or 70,000 line/s for 2048-OCT. 3D Data sets are continuously acquired in real time at 1024-OCT mode, immediately processed and visualized as high as 10 volumes/second (12,500 A-scans/volume) by either en face slice extraction or ray-casting based volume rendering from 3D texture mapped in graphics memory. For standard FD-OCT systems, a GPU is the only additional hardware needed to realize this improvement and no optical modification is needed. This technique is highly cost-effective and can be easily integrated into most ultrahigh speed FD-OCT systems to overcome the 3D data processing and visualization bottlenecks.
Zhang, Kang; Kang, Jin U
2010-05-24
We realized graphics processing unit (GPU) based real-time 4D (3D+time) signal processing and visualization on a regular Fourier-domain optical coherence tomography (FD-OCT) system with a nonlinear k-space spectrometer. An ultra-high speed linear spline interpolation (LSI) method for lambda-to-k spectral re-sampling is implemented in the GPU architecture, which gives average interpolation speeds of >3,000,000 line/s for 1024-pixel OCT (1024-OCT) and >1,400,000 line/s for 2048-pixel OCT (2048-OCT). The complete FD-OCT signal processing including lambda-to-k spectral re-sampling, fast Fourier transform (FFT) and post-FFT processing have all been implemented on a GPU. The maximum complete A-scan processing speeds are investigated to be 680,000 line/s for 1024-OCT and 320,000 line/s for 2048-OCT, which correspond to 1GByte processing bandwidth. In our experiment, a 2048-pixel CMOS camera running up to 70 kHz is used as an acquisition device. Therefore the actual imaging speed is camera- limited to 128,000 line/s for 1024-OCT or 70,000 line/s for 2048-OCT. 3D Data sets are continuously acquired in real time at 1024-OCT mode, immediately processed and visualized as high as 10 volumes/second (12,500 A-scans/volume) by either en face slice extraction or ray-casting based volume rendering from 3D texture mapped in graphics memory. For standard FD-OCT systems, a GPU is the only additional hardware needed to realize this improvement and no optical modification is needed. This technique is highly cost-effective and can be easily integrated into most ultrahigh speed FD-OCT systems to overcome the 3D data processing and visualization bottlenecks. PMID:20589038
NASA Astrophysics Data System (ADS)
Indira Rani, S.; Taylor, Ruth; George, John P.; Rajagopal, E. N.
2016-05-01
INSAT-3D, the first Indian geostationary satellite with sounding capability, provides valuable information over India and the surrounding oceanic regions which are pivotal to Numerical Weather Prediction. In collaboration with UK Met Office, NCMRWF developed the assimilation capability of INSAT-3D Clear Sky Brightness Temperature (CSBT), both from the sounder and imager, in the 4D-Var assimilation system being used at NCMRWF. Out of the 18 sounder channels, radiances from 9 channels are selected for assimilation depending on relevance of the information in each channel. The first three high peaking channels, the CO2 absorption channels and the three water vapor channels (channel no. 10, 11, and 12) are assimilated both over land and Ocean, whereas the window channels (channel no. 6, 7, and 8) are assimilated only over the Ocean. Measured satellite radiances are compared with that from short range forecasts to monitor the data quality. This is based on the assumption that the observed satellite radiances are free from calibration errors and the short range forecast provided by NWP model is free from systematic errors. Innovations (Observation - Forecast) before and after the bias correction are indicative of how well the bias correction works. Since the biases vary with air-masses, time, scan angle and also due to instrument degradation, an accurate bias correction algorithm for the assimilation of INSAT-3D sounder radiance is important. This paper discusses the bias correction methods and other quality controls used for the selected INSAT-3D sounder channels and the impact of bias corrected radiance in the data assimilation system particularly over India and surrounding oceanic regions.
NASA Astrophysics Data System (ADS)
Shabana, Ahmed A.
2005-05-01
Dynamics of Multibody Systems introduces multibody dynamics, with an emphasis on flexible body dynamics. Many common mechanisms such as automobiles, space structures, robots, and micro machines have mechanical and structural systems that consist of interconnected rigid and deformable components. The dynamics of these large-scale, multibody systems are highly nonlinear, presenting complex problems that in most cases can only be solved with computer-based techniques. The book begins with a review of the basic ideas of kinematics and the dynamics of rigid and deformable bodies before moving on to more advanced topics and computer implementation. This new edition includes important new developments relating to the problem of large deformations and numerical algorithms as applied to flexible multibody systems. The book's wealth of examples and practical applications will be useful to graduate students, researchers, and practicing engineers working on a wide variety of flexible multibody systems.
NASA Technical Reports Server (NTRS)
Pelc, Joanna S.; Todling, Ricardo; Akkraoui, Amal El
2014-01-01
The Global Modeling and Assimilation Offce (GMAO) is currently using an IAU-based 3D-Var data assimilation system. GMAO has been experimenting with a 3D-Var-hybrid version of its data assimilation system (DAS) for over a year now, which will soon become operational and it will rapidly progress toward a 4D-EnVar. Concurrently, the machinery to exercise traditional 4DVar is in place and it is desirable to have a comparison of the traditional 4D approach with the other available options, and evaluate their performance in the Goddard Earth Observing System (GEOS) DAS. This work will also explore the possibility for constructing a reduced order model (ROM) to make traditional 4D-Var computationally attractive for increasing model resolutions. Part of the research on ROM will be to search for a suitably acceptable space to carry on the corresponding reduction. This poster illustrates how the IAU-based 4D-Var assimilation compares with our currently used IAU-based 3D-Var.
Shadow-driven 4D haptic visualization.
Zhang, Hui; Hanson, Andrew
2007-01-01
Just as we can work with two-dimensional floor plans to communicate 3D architectural design, we can exploit reduced-dimension shadows to manipulate the higher-dimensional objects generating the shadows. In particular, by taking advantage of physically reactive 3D shadow-space controllers, we can transform the task of interacting with 4D objects to a new level of physical reality. We begin with a teaching tool that uses 2D knot diagrams to manipulate the geometry of 3D mathematical knots via their projections; our unique 2D haptic interface allows the user to become familiar with sketching, editing, exploration, and manipulation of 3D knots rendered as projected imageson a 2D shadow space. By combining graphics and collision-sensing haptics, we can enhance the 2D shadow-driven editing protocol to successfully leverage 2D pen-and-paper or blackboard skills. Building on the reduced-dimension 2D editing tool for manipulating 3D shapes, we develop the natural analogy to produce a reduced-dimension 3D tool for manipulating 4D shapes. By physically modeling the correct properties of 4D surfaces, their bending forces, and their collisions in the 3D haptic controller interface, we can support full-featured physical exploration of 4D mathematical objects in a manner that is otherwise far beyond the experience accessible to human beings. As far as we are aware, this paper reports the first interactive system with force-feedback that provides "4D haptic visualization" permitting the user to model and interact with 4D cloth-like objects.
4D Printing with Mechanically Robust, Thermally Actuating Hydrogels.
Bakarich, Shannon E; Gorkin, Robert; in het Panhuis, Marc; Spinks, Geoffrey M
2015-06-01
A smart valve is created by 4D printing of hydrogels that are both mechanically robust and thermally actuating. The printed hydrogels are made up of an interpenetrating network of alginate and poly(N-isopropylacrylamide). 4D structures are created by printing the "dynamic" hydrogel ink alongside other static materials. PMID:25864515
4D Printing with Mechanically Robust, Thermally Actuating Hydrogels.
Bakarich, Shannon E; Gorkin, Robert; in het Panhuis, Marc; Spinks, Geoffrey M
2015-06-01
A smart valve is created by 4D printing of hydrogels that are both mechanically robust and thermally actuating. The printed hydrogels are made up of an interpenetrating network of alginate and poly(N-isopropylacrylamide). 4D structures are created by printing the "dynamic" hydrogel ink alongside other static materials.
Interactive animation of 4D performance capture.
Casas, Dan; Tejera, Margara; Guillemaut, Jean-Yves; Hilton, Adrian
2013-05-01
A 4D parametric motion graph representation is presented for interactive animation from actor performance capture in a multiple camera studio. The representation is based on a 4D model database of temporally aligned mesh sequence reconstructions for multiple motions. High-level movement controls such as speed and direction are achieved by blending multiple mesh sequences of related motions. A real-time mesh sequence blending approach is introduced, which combines the realistic deformation of previous nonlinear solutions with efficient online computation. Transitions between different parametric motion spaces are evaluated in real time based on surface shape and motion similarity. Four-dimensional parametric motion graphs allow real-time interactive character animation while preserving the natural dynamics of the captured performance.
Interactive animation of 4D performance capture.
Casas, Dan; Tejera, Margara; Guillemaut, Jean-Yves; Hilton, Adrian
2013-05-01
A 4D parametric motion graph representation is presented for interactive animation from actor performance capture in a multiple camera studio. The representation is based on a 4D model database of temporally aligned mesh sequence reconstructions for multiple motions. High-level movement controls such as speed and direction are achieved by blending multiple mesh sequences of related motions. A real-time mesh sequence blending approach is introduced, which combines the realistic deformation of previous nonlinear solutions with efficient online computation. Transitions between different parametric motion spaces are evaluated in real time based on surface shape and motion similarity. Four-dimensional parametric motion graphs allow real-time interactive character animation while preserving the natural dynamics of the captured performance. PMID:23492379
NASA Technical Reports Server (NTRS)
Doolin, B. F.
1975-01-01
Classes of large scale dynamic systems were discussed in the context of modern control theory. Specific examples discussed were in the technical fields of aeronautics, water resources and electric power.
The 4D-TECS integration for NASA TSRV airplane
NASA Technical Reports Server (NTRS)
Kaminer, I.; Oshaughnessy, P. R.
1989-01-01
The integration of the Total Energy Control System (TECS) concept with 4D navigation is described. This integration was made to increase the operational capacity of modern aircraft and encourage incorporation of this increased capability with the evolving National Airspace System (NAS). Described herein is: 4D smoothing, the basic concepts of TECS, the spoiler integration concept, an algorithm for nulling out time error, speed and altitude profile modes, manual spoiler implementation, 4D logic, and the results of linear and nonlinear analysis.
Schwaab, Julia; Kurz, Christopher; Sarti, Cristina; Bongers, André; Schoenahl, Frédéric; Bert, Christoph; Debus, Jürgen; Parodi, Katia; Jenne, Jürgen Walter
2015-01-01
Target motion, particularly in the abdomen, due to respiration or patient movement is still a challenge in many diagnostic and therapeutic processes. Hence, methods to detect and compensate this motion are required. Diagnostic ultrasound (US) represents a non-invasive and dose-free alternative to fluoroscopy, providing more information about internal target motion than respiration belt or optical tracking. The goal of this project is to develop an US-based motion tracking for real-time motion correction in radiation therapy and diagnostic imaging, notably in 4D positron emission tomography (PET). In this work, a workflow is established to enable the transformation of US tracking data to the coordinates of the treatment delivery or imaging system - even if the US probe is moving due to respiration. It is shown that the US tracking signal is equally adequate for 4D PET image reconstruction as the clinically used respiration belt and provides additional opportunities in this concern. Furthermore, it is demonstrated that the US probe being within the PET field of view generally has no relevant influence on the image quality. The accuracy and precision of all the steps in the calibration workflow for US tracking-based 4D PET imaging are found to be in an acceptable range for clinical implementation. Eventually, we show in vitro that an US-based motion tracking in absolute room coordinates with a moving US transducer is feasible. PMID:26649277
Schwaab, Julia; Kurz, Christopher; Sarti, Cristina; Bongers, André; Schoenahl, Frédéric; Bert, Christoph; Debus, Jürgen; Parodi, Katia; Jenne, Jürgen Walter
2015-01-01
Target motion, particularly in the abdomen, due to respiration or patient movement is still a challenge in many diagnostic and therapeutic processes. Hence, methods to detect and compensate this motion are required. Diagnostic ultrasound (US) represents a non-invasive and dose-free alternative to fluoroscopy, providing more information about internal target motion than respiration belt or optical tracking. The goal of this project is to develop an US-based motion tracking for real-time motion correction in radiation therapy and diagnostic imaging, notably in 4D positron emission tomography (PET). In this work, a workflow is established to enable the transformation of US tracking data to the coordinates of the treatment delivery or imaging system – even if the US probe is moving due to respiration. It is shown that the US tracking signal is equally adequate for 4D PET image reconstruction as the clinically used respiration belt and provides additional opportunities in this concern. Furthermore, it is demonstrated that the US probe being within the PET field of view generally has no relevant influence on the image quality. The accuracy and precision of all the steps in the calibration workflow for US tracking-based 4D PET imaging are found to be in an acceptable range for clinical implementation. Eventually, we show in vitro that an US-based motion tracking in absolute room coordinates with a moving US transducer is feasible. PMID:26649277
Semipredictable dynamical systems
NASA Astrophysics Data System (ADS)
García-Morales, Vladimir
2016-10-01
A new class of deterministic dynamical systems, termed semipredictable dynamical systems, is presented. The spatiotemporal evolution of these systems have both predictable and unpredictable traits, as found in natural complex systems. We prove a general result: The dynamics of any deterministic nonlinear cellular automaton (CA) with p possible dynamical states can be decomposed at each instant of time in a superposition of N layers involving p0, p1, …, pN - 1 dynamical states each, where the pk ∈ N , k ∈ [ 0 , N - 1 ] are divisors of p. If the divisors coincide with the prime factors of p this decomposition is unique. Conversely, we also prove that N CA working on symbols p0, p1, …, pN - 1 can be composed to create a graded CA rule with N different layers. We then show that, even when the full spatiotemporal evolution can be unpredictable, certain traits (layers) can exactly be predicted. We present explicit examples of such systems involving compositions of Wolfram's 256 elementary CA and a more complex CA rule acting on a neighborhood of two sites and 12 symbols and whose rule table corresponds to the smallest Moufang loop M12(S3, 2).
NASA Astrophysics Data System (ADS)
Pumpe, Daniel; Greiner, Maksim; Müller, Ewald; Enßlin, Torsten A.
2016-07-01
Stochastic differential equations describe well many physical, biological, and sociological systems, despite the simplification often made in their derivation. Here the usage of simple stochastic differential equations to characterize and classify complex dynamical systems is proposed within a Bayesian framework. To this end, we develop a dynamic system classifier (DSC). The DSC first abstracts training data of a system in terms of time-dependent coefficients of the descriptive stochastic differential equation. Thereby the DSC identifies unique correlation structures within the training data. For definiteness we restrict the presentation of the DSC to oscillation processes with a time-dependent frequency ω (t ) and damping factor γ (t ) . Although real systems might be more complex, this simple oscillator captures many characteristic features. The ω and γ time lines represent the abstract system characterization and permit the construction of efficient signal classifiers. Numerical experiments show that such classifiers perform well even in the low signal-to-noise regime.
Pumpe, Daniel; Greiner, Maksim; Müller, Ewald; Enßlin, Torsten A
2016-07-01
Stochastic differential equations describe well many physical, biological, and sociological systems, despite the simplification often made in their derivation. Here the usage of simple stochastic differential equations to characterize and classify complex dynamical systems is proposed within a Bayesian framework. To this end, we develop a dynamic system classifier (DSC). The DSC first abstracts training data of a system in terms of time-dependent coefficients of the descriptive stochastic differential equation. Thereby the DSC identifies unique correlation structures within the training data. For definiteness we restrict the presentation of the DSC to oscillation processes with a time-dependent frequency ω(t) and damping factor γ(t). Although real systems might be more complex, this simple oscillator captures many characteristic features. The ω and γ time lines represent the abstract system characterization and permit the construction of efficient signal classifiers. Numerical experiments show that such classifiers perform well even in the low signal-to-noise regime.
Pumpe, Daniel; Greiner, Maksim; Müller, Ewald; Enßlin, Torsten A
2016-07-01
Stochastic differential equations describe well many physical, biological, and sociological systems, despite the simplification often made in their derivation. Here the usage of simple stochastic differential equations to characterize and classify complex dynamical systems is proposed within a Bayesian framework. To this end, we develop a dynamic system classifier (DSC). The DSC first abstracts training data of a system in terms of time-dependent coefficients of the descriptive stochastic differential equation. Thereby the DSC identifies unique correlation structures within the training data. For definiteness we restrict the presentation of the DSC to oscillation processes with a time-dependent frequency ω(t) and damping factor γ(t). Although real systems might be more complex, this simple oscillator captures many characteristic features. The ω and γ time lines represent the abstract system characterization and permit the construction of efficient signal classifiers. Numerical experiments show that such classifiers perform well even in the low signal-to-noise regime. PMID:27575101
Complexity in Dynamical Systems
NASA Astrophysics Data System (ADS)
Moore, Cristopher David
The study of chaos has shown us that deterministic systems can have a kind of unpredictability, based on a limited knowledge of their initial conditions; after a finite time, the motion appears essentially random. This observation has inspired a general interest in the subject of unpredictability, and more generally, complexity; how can we characterize how "complex" a dynamical system is?. In this thesis, we attempt to answer this question with a paradigm of complexity that comes from computer science, we extract sets of symbol sequences, or languages, from a dynamical system using standard methods of symbolic dynamics; we then ask what kinds of grammars or automata are needed a generate these languages. This places them in the Chomsky heirarchy, which in turn tells us something about how subtle and complex the dynamical system's behavior is. This gives us insight into the question of unpredictability, since these automata can also be thought of as computers attempting to predict the system. In the culmination of the thesis, we find a class of smooth, two-dimensional maps which are equivalent to the highest class in the Chomsky heirarchy, the turning machine; they are capable of universal computation. Therefore, these systems possess a kind of unpredictability qualitatively different from the usual "chaos": even if the initial conditions are known exactly, questions about the system's long-term dynamics are undecidable. No algorithm exists to answer them. Although this kind of unpredictability has been discussed in the context of distributed, many-degree-of -freedom systems (for instance, cellular automata) we believe this is the first example of such phenomena in a smooth, finite-degree-of-freedom system.
Advances in 4D radiation therapy for managing respiration: part II - 4D treatment planning.
Rosu, Mihaela; Hugo, Geoffrey D
2012-12-01
The development of 4D CT imaging technology made possible the creation of patient models that are reflective of respiration-induced anatomical changes by adding a temporal dimension to the conventional 3D, spatial-only, patient description. This had opened a new venue for treatment planning and radiation delivery, aimed at creating a comprehensive 4D radiation therapy process for moving targets. Unlike other breathing motion compensation strategies (e.g. breath-hold and gating techniques), 4D radiotherapy assumes treatment delivery over the entire respiratory cycle - an added bonus for both patient comfort and treatment time efficiency. The time-dependent positional and volumetric information holds the promise for optimal, highly conformal, radiotherapy for targets experiencing movements caused by respiration, with potentially elevated dose prescriptions and therefore higher cure rates, while avoiding the uninvolved nearby structures. In this paper, the current state of the 4D treatment planning is reviewed, from theory to the established practical routine. While the fundamental principles of 4D radiotherapy are well defined, the development of a complete, robust and clinically feasible process still remains a challenge, imposed by limitations in the available treatment planning and radiation delivery systems.
Advances in 4D Radiation Therapy for Managing Respiration: Part II – 4D Treatment Planning
Rosu, Mihaela; Hugo, Geoffrey D.
2014-01-01
The development of 4D CT imaging technology made possible the creation of patient models that are reflective of respiration-induced anatomical changes by adding a temporal dimension to the conventional 3D, spatial-only, patient description. This had opened a new venue for treatment planning and radiation delivery, aimed at creating a comprehensive 4D radiation therapy process for moving targets. Unlike other breathing motion compensation strategies (e.g. breath-hold and gating techniques), 4D radiotherapy assumes treatment delivery over the entire respiratory cycle – an added bonus for both patient comfort and treatment time efficiency. The time-dependent positional and volumetric information holds the promise for optimal, highly conformal, radiotherapy for targets experiencing movements caused by respiration, with potentially elevated dose prescriptions and therefore higher cure rates, while avoiding the uninvolved nearby structures. In this paper, the current state of the 4D treatment planning is reviewed, from theory to the established practical routine. While the fundamental principles of 4D radiotherapy are well defined, the development of a complete, robust and clinically feasible process still remains a challenge, imposed by limitations in the available treatment planning and radiation delivery systems. PMID:22796324
Impact of 4D image quality on the accuracy of target definition.
Nielsen, Tine Bjørn; Hansen, Christian Rønn; Westberg, Jonas; Hansen, Olfred; Brink, Carsten
2016-03-01
Delineation accuracy of target shape and position depends on the image quality. This study investigates whether the image quality on standard 4D systems has an influence comparable to the overall delineation uncertainty. A moving lung target was imaged using a dynamic thorax phantom on three different 4D computed tomography (CT) systems and a 4D cone beam CT (CBCT) system using pre-defined clinical scanning protocols. Peak-to-peak motion and target volume were registered using rigid registration and automatic delineation, respectively. A spatial distribution of the imaging uncertainty was calculated as the distance deviation between the imaged target and the true target shape. The measured motions were smaller than actual motions. There were volume differences of the imaged target between respiration phases. Imaging uncertainties of >0.4 cm were measured in the motion direction which showed that there was a large distortion of the imaged target shape. Imaging uncertainties of standard 4D systems are of similar size as typical GTV-CTV expansions (0.5-1 cm) and contribute considerably to the target definition uncertainty. Optimising and validating 4D systems is recommended in order to obtain the most optimal imaged target shape.
Pros and cons for C4d as a biomarker.
Cohen, Danielle; Colvin, Robert B; Daha, Mohamed R; Drachenberg, Cinthia B; Haas, Mark; Nickeleit, Volker; Salmon, Jane E; Sis, Banu; Zhao, Ming-Hui; Bruijn, Jan A; Bajema, Ingeborg M
2012-04-01
The introduction of C4d in daily clinical practice in the late nineties aroused an ever-increasing interest in the role of antibody-mediated mechanisms in allograft rejection. As a marker of classical complement activation, C4d made it possible to visualize the direct link between anti-donor antibodies and tissue injury at sites of antibody binding in a graft. With the expanding use of C4d worldwide several limitations of C4d were identified. For instance, in ABO-incompatible transplantations C4d is present in the majority of grafts but this seems to point at 'graft accommodation' rather than antibody-mediated rejection. C4d is now increasingly recognized as a potential biomarker in other fields where antibodies can cause tissue damage, such as systemic autoimmune diseases and pregnancy. In all these fields, C4d holds promise to detect patients at risk for the consequences of antibody-mediated disease. Moreover, the emergence of new therapeutics that block complement activation makes C4d a marker with potential to identify patients who may possibly benefit from these drugs. This review provides an overview of the past, present, and future perspectives of C4d as a biomarker, focusing on its use in solid organ transplantation and discussing its possible new roles in autoimmunity and pregnancy. PMID:22297669
Girardi, Cristobal; Nowak, Karolina M; Carranza-Diaz, Otoniel; Lewkow, Benjamín; Miltner, Anja; Gehre, Matthias; Schäffer, Andreas; Kästner, Matthias
2013-02-01
The persistence of chemicals is a key parameter for their environmental risk assessment. Extrapolating their biodegradability potential in aqueous systems to soil systems would improve the environmental impact assessment. This study compares the fate of (14/13)C-labelled 2,4-D (2,4-dichlorophenoxyacetic acid) and ibuprofen in OECD tests 301 (ready biodegradability in aqueous systems) and 307 (soil). 85% of 2,4-D and 68% of ibuprofen were mineralised in aqueous systems, indicating ready biodegradability, but only 57% and 45% in soil. Parent compounds and metabolites decreased to <2% of the spiked amounts in both systems. In soil, 36% of 2,4-D and 30% of ibuprofen were bound in non-extractable residues (NER). NER formation in the abiotic controls was half as high as in the biotic treatments. However, mineralisation, biodegradation and abiotic residue formation are competing processes. Assuming the same extent of abiotic NER formation in abiotic and biotic systems may therefore overestimate the abiotic contribution in the biotic systems. Mineralisation was described by a logistic model for the aquatic systems and by a two-pool first order degradation model for the soil systems. This agrees with the different abundance of microorganisms in the two systems, but precludes direct comparison of the fitted parameters. Nevertheless, the maximum mineralisable amounts determined by the models were similar in both systems, although the maximum mineralisation rate was about 3.5 times higher in the aqueous systems than in the soil system for both compounds; these parameters may thus be extrapolated from aqueous to soil systems. However, the maximum mineralisable amount is calculated by extrapolation to infinite times and includes intermediately formed biomass derived from the labelled carbon. The amount of labelled carbon within microbial biomass residues is higher in the soil system, resulting in lower degradation rates. Further evaluation of these relationships requires
4D electron microscopy: principles and applications.
Flannigan, David J; Zewail, Ahmed H
2012-10-16
achievable with short intense pulses containing a large number of electrons, however, are limited to tens of nanometers and nanoseconds, respectively. This is because Coulomb repulsion is significant in such a pulse, and the electrons spread in space and time, thus limiting the beam coherence. It is therefore not possible to image the ultrafast elementary dynamics of complex transformations. The challenge was to retain the high spatial resolution of a conventional TEM while simultaneously enabling the temporal resolution required to visualize atomic-scale motions. In this Account, we discuss the development of four-dimensional ultrafast electron microscopy (4D UEM) and summarize techniques and applications that illustrate the power of the approach. In UEM, images are obtained either stroboscopically with coherent single-electron packets or with a single electron bunch. Coulomb repulsion is absent under the single-electron condition, thus permitting imaging, diffraction, and spectroscopy, all with high spatiotemporal resolution, the atomic scale (sub-nanometer and femtosecond). The time resolution is limited only by the laser pulse duration and energy carried by the electron packets; the CCD camera has no bearing on the temporal resolution. In the regime of single pulses of electrons, the temporal resolution of picoseconds can be attained when hundreds of electrons are in the bunch. The applications given here are selected to highlight phenomena of different length and time scales, from atomic motions during structural dynamics to phase transitions and nanomechanical oscillations. We conclude with a brief discussion of emerging methods, which include scanning ultrafast electron microscopy (S-UEM), scanning transmission ultrafast electron microscopy (ST-UEM) with convergent beams, and time-resolved imaging of biological structures at ambient conditions with environmental cells.
NASA Astrophysics Data System (ADS)
Lauinger, Norbert
1999-08-01
Diffractive 3D phase gratings of spherical scatterers dense in hexagonal packing geometry represent adaptively tunable 4D-spatiotemporal filters with trichromatic resonance in visible spectrum. They are described in the (lambda) - chromatic and the reciprocal (nu) -aspects by reciprocal geometric translations of the lightlike Pythagoras theorem, and by the direction cosine for double cones. The most elementary resonance condition in the lightlike Pythagoras theorem is given by the transformation of the grating constants gx, gy, gz of the hexagonal 3D grating to (lambda) h1h2h3 equals (lambda) 111 with cos (alpha) equals 0.5. Through normalization of the chromaticity in the von Laue-interferences to (lambda) 111, the (nu) (lambda) equals (lambda) h1h2h3/(lambda) 111-factor of phase velocity becomes the crucial resonance factor, the 'regulating device' of the spatiotemporal interaction between 3D grating and light, space and time. In the reciprocal space equal/unequal weights and times in spectral metrics result at positions of interference maxima defined by hyperbolas and circles. A database becomes built up by optical interference for trichromatic image preprocessing, motion detection in vector space, multiple range data analysis, patchwide multiple correlations in the spatial frequency spectrum, etc.
NASA Technical Reports Server (NTRS)
Wisdom, Jack
2002-01-01
In these 18 years, the research has touched every major dynamical problem in the solar system, including: the effect of chaotic zones on the distribution of asteroids, the delivery of meteorites along chaotic pathways, the chaotic motion of Pluto, the chaotic motion of the outer planets and that of the whole solar system, the delivery of short period comets from the Kuiper belt, the tidal evolution of the Uranian arid Galilean satellites, the chaotic tumbling of Hyperion and other irregular satellites, the large chaotic variations of the obliquity of Mars, the evolution of the Earth-Moon system, and the resonant core- mantle dynamics of Earth and Venus. It has introduced new analytical and numerical tools that are in widespread use. Today, nearly every long-term integration of our solar system, its subsystems, and other solar systems uses algorithms that was invented. This research has all been primarily Supported by this sequence of PGG NASA grants. During this period published major investigations of tidal evolution of the Earth-Moon system and of the passage of the Earth and Venus through non-linear core-mantle resonances were completed. It has published a major innovation in symplectic algorithms: the symplectic corrector. A paper was completed on non-perturbative hydrostatic equilibrium.
Chaos in a 4D dissipative nonlinear fermionic model
NASA Astrophysics Data System (ADS)
Aydogmus, Fatma
2015-12-01
Gursey Model is the only possible 4D conformally invariant pure fermionic model with a nonlinear self-coupled spinor term. It has been assumed to be similar to the Heisenberg's nonlinear generalization of Dirac's equation, as a possible basis for a unitary description of elementary particles. Gursey Model admits particle-like solutions for the derived classical field equations and these solutions are instantonic in character. In this paper, the dynamical nature of damped and forced Gursey Nonlinear Differential Equations System (GNDES) are studied in order to get more information on spinor type instantons. Bifurcation and chaos in the system are observed by constructing the bifurcation diagrams and Poincaré sections. Lyapunov exponent and power spectrum graphs of GNDES are also constructed to characterize the chaotic behavior.
The Use of Gated and 4D CT Imaging in Planning for Stereotactic Body Radiation Therapy
D'Souza, Warren D. . E-mail: wdsou001@umaryland.edu; Nazareth, Daryl P.; Zhang Bin; Deyoung, Chad; Suntharalingam, Mohan; Kwok, Young; Yu, Cedric X.; Regine, William F.
2007-07-01
The localization of treatment targets is of utmost importance for patients receiving stereotactic body radiation therapy (SBRT), where the dose per fraction is large. While both setup or respiration-induced motion components affect the localization of the treatment volume, the purpose of this work is to describe our management of the intrafraction localization uncertainty induced by normal respiration. At our institution, we have implemented gated computed tomography (CT) acquisition with an active breathing control system (ABC), and 4-dimensional (4D) CT using a skin-based marker and retrospective respiration phase-based image sorting. During gated simulation, 3D CT images were acquired corresponding to end-inhalation and end-exhalation. For 4D CT imaging, 3D CT images were acquired corresponding to 8 phases of the respiratory cycle. In addition to gated or 4D CT images, we acquired a conventional free-breathing CT (FB). For both gated and 4D CT images, the target contours were registered to the FB scan in the planning system. These contours were then combined in the FB image set to form the internal target volume (ITV). Dynamic conformal arc treatment plans were generated for the ITV using the FB scan and the gated or 4D scans with an additional 7-mm margin for patient setup uncertainty. We have described our results for a pancreas and a lung tumor case. Plans were normalized so that the PTV received 95% of the prescription dose. The dose distribution for all the critical structures in the pancreas and lung tumor cases resulted in increased sparing when the ITV was defined using gated or 4D CT images than when the FB scan was used. Our results show that patient-specific target definition using gated or 4D CT scans lead to improved normal tissue sparing.
A dynamic 3D foot reconstruction system.
Thabet, Ali K; Trucco, Emanuele; Salvi, Joaquim; Wang, Weijie; Abboud, Rami J
2011-01-01
Foot problems are varied and range from simple disorders through to complex diseases and joint deformities. Wherever possible, the use of insoles, or orthoses, is preferred over surgery. Current insole design techniques are based on static measurements of the foot, despite the fact that orthoses are prevalently used in dynamic conditions while walking or running. This paper presents the design and implementation of a structured-light prototype system providing dense three dimensional (3D) measurements of the foot in motion, and its use to show that foot measurements in dynamic conditions differ significantly from their static counterparts. The input to the system is a video sequence of a foot during a single step; the output is a 3D reconstruction of the plantar surface of the foot for each frame of the input. Engineering and clinical tests were carried out for the validation of the system. The accuracy of the system was found to be 0.34 mm with planar test objects. In tests with real feet, the system proved repeatable, with reconstruction differences between trials one week apart averaging 2.44 mm (static case) and 2.81 mm (dynamic case). Furthermore, a study was performed to compare the effective length of the foot between static and dynamic reconstructions using the 4D system. Results showed an average increase of 9 mm for the dynamic case. This increase is substantial for orthotics design, cannot be captured by a static system, and its subject-specific measurement is crucial for the design of effective foot orthoses.
4D-DSA and 4D fluoroscopy: preliminary implementation
NASA Astrophysics Data System (ADS)
Mistretta, C. A.; Oberstar, E.; Davis, B.; Brodsky, E.; Strother, C. M.
2010-04-01
We have described methods that allow highly accelerated MRI using under-sampled acquisitions and constrained reconstruction. One is a hybrid acquisition involving the constrained reconstruction of time dependent information obtained from a separate scan of longer duration. We have developed reconstruction algorithms for DSA that allow use of a single injection to provide the temporal data required for flow visualization and the steady state data required for construction of a 3D-DSA vascular volume. The result is time resolved 3D volumes with typical resolution of 5123 at frame rates of 20-30 fps. Full manipulation of these images is possible during each stage of vascular filling thereby allowing for simplified interpretation of vascular dynamics. For intravenous angiography this time resolved 3D capability overcomes the vessel overlap problem that greatly limited the use of conventional intravenous 2D-DSA. Following further hardware development, it will be also be possible to rotate fluoroscopic volumes for use as roadmaps that can be viewed at arbitrary angles without a need for gantry rotation. The most precise implementation of this capability requires availability of biplane fluoroscopy data. Since the reconstruction of 3D volumes presently suppresses the contrast in the soft tissue, the possibility of using these techniques to derive complete indications of perfusion deficits based on cerebral blood volume (CBV), mean transit time (MTT) and time to peak (TTP) parameters requires further investigation. Using MATLAB post-processing, successful studies in animals and humans done in conjunction with both intravenous and intra-arterial injections have been completed. Real time implementation is in progress.
Dynamic Information Architecture System
1997-02-12
The Dynamic Information System (DIAS) is a flexible object-based software framework for concurrent, multidiscplinary modeling of arbitrary (but related) processes. These processes are modeled as interrelated actions caused by and affecting the collection of diverse real-world objects represented in a simulation. The DIAS architecture allows independent process models to work together harmoniously in the same frame of reference and provides a wide range of data ingestion and output capabilities, including Geographic Information System (GIS) typemore » map-based displays and photorealistic visualization of simulations in progress. In the DIAS implementation of the object-based approach, software objects carry within them not only the data which describe their static characteristics, but also the methods, or functions, which describe their dynamic behaviors. There are two categories of objects: (1) Entity objects which have real-world counterparts and are the actors in a simulation, and (2) Software infrastructure objects which make it possible to carry out the simulations. The Entity objects contain lists of Aspect objects, each of which addresses a single aspect of the Entity''s behavior. For example, a DIAS Stream Entity representing a section of a river can have many aspects correspondimg to its behavior in terms of hydrology (as a drainage system component), navigation (as a link in a waterborne transportation system), meteorology (in terms of moisture, heat, and momentum exchange with the atmospheric boundary layer), and visualization (for photorealistic visualization or map type displays), etc. This makes it possible for each real-world object to exhibit any or all of its unique behaviors within the context of a single simulation.« less
Dynamical systems theory for music dynamics
NASA Astrophysics Data System (ADS)
Boon, Jean Pierre; Decroly, Olivier
1995-09-01
We show that, when music pieces are cast in the form of time series of pitch variations, the concepts and tools of dynamical systems theory can be applied to the analysis of temporal dynamics in music. (i) Phase space portraits are constructed from the time series wherefrom the dimensionality is evaluated as a measure of the global dynamics of each piece. (ii) Spectral analysis of the time series yields power spectra (˜f-ν) close to red noise (ν˜2) in the low frequency range. (iii) We define an information entropy which provides a measure of the local dynamics in the musical piece; the entropy can be interpreted as an evaluation of the degree of complexity in the music, but there is no evidence of an analytical relation between local and global dynamics. These findings are based on computations performed on eighty sequences sampled in the music literature from the 18th to the 20th century.
Data Systems Dynamic Simulator
NASA Technical Reports Server (NTRS)
Rouff, Christopher; Clark, Melana; Davenport, Bill; Message, Philip
1993-01-01
The Data System Dynamic Simulator (DSDS) is a discrete event simulation tool. It was developed for NASA for the specific purpose of evaluating candidate architectures for data systems of the Space Station era. DSDS provides three methods for meeting this requirement. First, the user has access to a library of standard pre-programmed elements. These elements represent tailorable components of NASA data systems and can be connected in any logical manner. Secondly, DSDS supports the development of additional elements. This allows the more sophisticated DSDS user the option of extending the standard element set. Thirdly, DSDS supports the use of data streams simulation. Data streams is the name given to a technique that ignores packet boundaries, but is sensitive to rate changes. Because rate changes are rare compared to packet arrivals in a typical NASA data system, data stream simulations require a fraction of the CPU run time. Additionally, the data stream technique is considerably more accurate than another commonly-used optimization technique.
Dynamic Modeling of ALS Systems
NASA Technical Reports Server (NTRS)
Jones, Harry
2002-01-01
The purpose of dynamic modeling and simulation of Advanced Life Support (ALS) systems is to help design them. Static steady state systems analysis provides basic information and is necessary to guide dynamic modeling, but static analysis is not sufficient to design and compare systems. ALS systems must respond to external input variations and internal off-nominal behavior. Buffer sizing, resupply scheduling, failure response, and control system design are aspects of dynamic system design. We develop two dynamic mass flow models and use them in simulations to evaluate systems issues, optimize designs, and make system design trades. One model is of nitrogen leakage in the space station, the other is of a waste processor failure in a regenerative life support system. Most systems analyses are concerned with optimizing the cost/benefit of a system at its nominal steady-state operating point. ALS analysis must go beyond the static steady state to include dynamic system design. All life support systems exhibit behavior that varies over time. ALS systems must respond to equipment operating cycles, repair schedules, and occasional off-nominal behavior or malfunctions. Biological components, such as bioreactors, composters, and food plant growth chambers, usually have operating cycles or other complex time behavior. Buffer sizes, material stocks, and resupply rates determine dynamic system behavior and directly affect system mass and cost. Dynamic simulation is needed to avoid the extremes of costly over-design of buffers and material reserves or system failure due to insufficient buffers and lack of stored material.
NASA Astrophysics Data System (ADS)
Ohbayashi, K.; Choi, D.; Hiro-oka, H.; Kubota, A.; Ohno, T.; Ikeda, R.; Shimizu, K.
2011-03-01
Optical coherence tomography (OCT) has become a promising diagnostic method in many medical fields. Non-invasive real-time optical biopsy of internal organs is one of the most attractive applications of OCT enabling in-situ diagnostic of cancer in its early stage, i.e. optical biopsy. For the application, faster OCT methods are required to reduce the inspection time and motion artifacts in images. A criterion to satisfy the purpose is an endoscopic-OCT method capable to display volumetric tomography continuously in real-time at a rate of video movie like conventional endoscopes. In our previous work, we demonstrated ultra-high speed OCT at an A-scan rate of 60 MHz. However, movies were rendered after the data acquisition. In this work, we have developed an ultra-fast data processing system, installed it in the ultra-high speed OCT system, and enabled real time display of various 3D tomography images without limitation of diagnostic time, i.e. 4D OCT imaging, at an A-scan rate, B-scan rate and volume rate of 10 MHz, 4 kHz and 12 volumes/sec, respectively. Various image presentations in real-time are demonstrated such as continuous rendered 3D imaging and continuous 2D-slice scanning 3D imaging.
Landscape Construction in Dynamical Systems
NASA Astrophysics Data System (ADS)
Tang, Ying; Yuan, Ruoshi; Wang, Gaowei; Ao, Ping
The idea of landscape has been recently applied to study various of biological problems. We demonstrate that a dynamical structure built into nonlinear dynamical systems allows us to construct such a global optimization landscape, which serves as the Lyapunov function for the ordinary differential equation. We find exact constructions on the landscape for a class of dynamical systems, including a van der Pol type oscillator, competitive Lotka-Volterra systems, and a chaotic system. The landscape constructed provides a new angle for understanding and modelling biological network dynamics.
Rupasree, Y; Naushad, S M; Rajasekhar, L; Uma, A; Kutala, V K
2015-01-01
The rationale of this case-control study was to explore the association of Toll-like receptor 4 (TLR4) D299G, TLR4 T399I, TLR9 -1486 T>C, TIR-domain-containing adaptor protein (TIRAP) S180 L and tumor necrosis-α (TNF-α) promoter polymorphisms with susceptibility and phenotypic heterogeneity of systemic lupus erythematosus (SLE). PCR-RFLP, real-time PCR was used for the genetic analysis and expression studies and ELISA was used for the determination of specific autoantibodies. TLR4 D299G was associated with the risk for SLE (OR: 1.57, 95% CI: 1.08-2.28), while the TNF-α (-1031, -863, -857) CCC haplotype conferred protection. TLR4 and TIRAP polymorphisms were associated with reduced expression of HLA-DR. The presence of TLR4 and TLR9 polymorphisms increases the MHC2TA expression, while TIRAP polymorphism was associated with reduced expression. TLR4 D299 G showed an inverse association with pulmonary hypertension. TLR 4 T399I and TLR9 -1486 T>C showed a positive association with seizures and photosensitivity, respectively. TIRAP S180 L showed a positive association with alopecia and malar rashes, while an inverse association with psychosis was observed. TLR4 T399I (r = 0.14, p = 0.05) and TIRAP S180 L (r = 0.15, p = 0.03) showed a positive association with anti-Ro antibodies. On the other hand, TLR9 -1486 T>C showed an inverse association with anti-La antibodies (r = -0.20, p = 0.006). To conclude, TLR4 D299G increases the risk for SLE, while TNF-α CCC haplotype reduces the risk for SLE. All these polymorphisms contribute toward phenotypic heterogeneity. TLR4 T399I, TLR9 -1486 T>C and TIRAP S180 L influence specific autoantibody production in SLE.
Dynamical systems theory for music dynamics.
Boon, Jean Pierre; Decroly, Olivier
1995-09-01
We show that, when music pieces are cast in the form of time series of pitch variations, the concepts and tools of dynamical systems theory can be applied to the analysis of temporal dynamics in music. (i) Phase space portraits are constructed from the time series wherefrom the dimensionality is evaluated as a measure of the global dynamics of each piece. (ii) Spectral analysis of the time series yields power spectra ( approximately f(-nu)) close to red noise (nu approximately 2) in the low frequency range. (iii) We define an information entropy which provides a measure of the local dynamics in the musical piece; the entropy can be interpreted as an evaluation of the degree of complexity in the music, but there is no evidence of an analytical relation between local and global dynamics. These findings are based on computations performed on eighty sequences sampled in the music literature from the 18th to the 20th century. (c) 1995 American Institute of Physics. PMID:12780206
Killoran, Joseph H; Gerbaudo, Victor H; Mamede, Marcelo; Ionascu, Dan; Park, Sang-June; Berbeco, Ross
2011-11-15
For PET/CT, fast CT acquisition time can lead to errors in attenuation correction, particularly at the lung/diaphragm interface. Gated 4D PET can reduce motion artifacts, though residual artifacts may persist depending on the CT dataset used for attenuation correction. We performed phantom studies to evaluate 4D PET images of targets near a density interface using three different methods for attenuation correction: a single 3D CT (3D CTAC), an averaged 4D CT (CINE CTAC), and a fully phase matched 4D CT (4D CTAC). A phantom was designed with two density regions corresponding to diaphragm and lung. An 8 mL sphere phantom loaded with 18F-FDG was used to represent a lung tumor and background FDG included at an 8:1 ratio. Motion patterns of sin(x) and sin4(x) were used for dynamic studies. Image data was acquired using a GE Discovery DVCT-PET/CT scanner. Attenuation correction methods were compared based on normalized recovery coefficient (NRC), as well as a novel quantity "fixed activity volume" (FAV) introduced in our report. Image metrics were compared to those determined from a 3D PET scan with no motion present (3D STATIC). Values of FAV and NRC showed significant variation over the motion cycle when corrected by 3D CTAC images. 4D CTAC- and CINE CTAC-corrected PET images reduced these motion artifacts. The amount of artifact reduction is greater when the target is surrounded by lower density material and when motion was based on sin4(x). 4D CTAC reduced artifacts more than CINE CTAC for most scenarios. For a target surrounded by water equivalent material, there was no advantage to 4D CTAC over CINE CTAC when using the sin(x) motion pattern. Attenuation correction using both 4D CTAC or CINE CTAC can reduce motion artifacts in regions that include a tissue interface such as the lung/diaphragm border. 4D CTAC is more effective than CINE CTAC at reducing artifacts in some, but not all, scenarios.
Helical 4D CT and Comparison with Cine 4D CT
NASA Astrophysics Data System (ADS)
Pan, Tinsu
4D CT was one of the most important developments in radiation oncology in the last decade. Its early development in single slice CT and commercialization in multi-slice CT has radically changed our practice in radiation treatment of lung cancer, and has enabled the stereotactic radiosurgery of early stage lung cancer. In this chapter, we will document the history of 4D CT development, detail the data sufficiency condition governing the 4D CT data collection; present the design of the commercial helical 4D CTs from Philips and Siemens; compare the differences between the helical 4D CT and the GE cine 4D CT in data acquisition, slice thickness, acquisition time and work flow; review the respiratory monitoring devices; and understand the causes of image artifacts in 4D CT.
Semaphorin 4D Promotes Skeletal Metastasis in Breast Cancer.
Yang, Ying-Hua; Buhamrah, Asma; Schneider, Abraham; Lin, Yi-Ling; Zhou, Hua; Bugshan, Amr; Basile, John R
2016-01-01
Bone density is controlled by interactions between osteoclasts, which resorb bone, and osteoblasts, which deposit it. The semaphorins and their receptors, the plexins, originally shown to function in the immune system and to provide chemotactic cues for axon guidance, are now known to play a role in this process as well. Emerging data have identified Semaphorin 4D (Sema4D) as a product of osteoclasts acting through its receptor Plexin-B1 on osteoblasts to inhibit their function, tipping the balance of bone homeostasis in favor of resorption. Breast cancers and other epithelial malignancies overexpress Sema4D, so we theorized that tumor cells could be exploiting this pathway to establish lytic skeletal metastases. Here, we use measurements of osteoblast and osteoclast differentiation and function in vitro and a mouse model of skeletal metastasis to demonstrate that both soluble Sema4D and protein produced by the breast cancer cell line MDA-MB-231 inhibits differentiation of MC3T3 cells, an osteoblast cell line, and their ability to form mineralized tissues, while Sema4D-mediated induction of IL-8 and LIX/CXCL5, the murine homologue of IL-8, increases osteoclast numbers and activity. We also observe a decrease in the number of bone metastases in mice injected with MDA-MB-231 cells when Sema4D is silenced by RNA interference. These results are significant because treatments directed at suppression of skeletal metastases in bone-homing malignancies usually work by arresting bone remodeling, potentially leading to skeletal fragility, a significant problem in patient management. Targeting Sema4D in these cancers would not affect bone remodeling and therefore could elicit an improved therapeutic result without the debilitating side effects.
Semaphorin 4D Promotes Skeletal Metastasis in Breast Cancer
Yang, Ying-Hua; Buhamrah, Asma; Schneider, Abraham; Lin, Yi-Ling; Zhou, Hua; Bugshan, Amr; Basile, John R.
2016-01-01
Bone density is controlled by interactions between osteoclasts, which resorb bone, and osteoblasts, which deposit it. The semaphorins and their receptors, the plexins, originally shown to function in the immune system and to provide chemotactic cues for axon guidance, are now known to play a role in this process as well. Emerging data have identified Semaphorin 4D (Sema4D) as a product of osteoclasts acting through its receptor Plexin-B1 on osteoblasts to inhibit their function, tipping the balance of bone homeostasis in favor of resorption. Breast cancers and other epithelial malignancies overexpress Sema4D, so we theorized that tumor cells could be exploiting this pathway to establish lytic skeletal metastases. Here, we use measurements of osteoblast and osteoclast differentiation and function in vitro and a mouse model of skeletal metastasis to demonstrate that both soluble Sema4D and protein produced by the breast cancer cell line MDA-MB-231 inhibits differentiation of MC3T3 cells, an osteoblast cell line, and their ability to form mineralized tissues, while Sema4D-mediated induction of IL-8 and LIX/CXCL5, the murine homologue of IL-8, increases osteoclast numbers and activity. We also observe a decrease in the number of bone metastases in mice injected with MDA-MB-231 cells when Sema4D is silenced by RNA interference. These results are significant because treatments directed at suppression of skeletal metastases in bone-homing malignancies usually work by arresting bone remodeling, potentially leading to skeletal fragility, a significant problem in patient management. Targeting Sema4D in these cancers would not affect bone remodeling and therefore could elicit an improved therapeutic result without the debilitating side effects. PMID:26910109
The Role of 4D Ultrasound in the Assessment of Fetal Behaviour
Lebit, Dr. Florentina-Daniela; Vladareanu, Professor Dr. Radu
2011-01-01
ABSTRACT Fetal behavior is defined as any fetal action seen by the mother or fetus diagnosed by objective methods such as cardiotocography (CTG) or ultrasound. Analysis of the dynamics of the fetal behavior with morphological studies has lead to the conclusion that fetal behavior patterns are directly reflecting development and maturation of the central nervous system. The assessment of fetal behavior by 4D ultrasound could allow distinction between normal and abnormal fetal behavior patterns which might make possible the early recognition of fetal brain impairment. Aim: Assessment of fetal movements throughout the pregnancy using 4D ultrasound. Material and Method: The study group included 144 healthy pregnant women with single pregnancies between 7-38 weeks of gestation. For the first trimester of pregnancy we assessed eight types of fetal movements and for the second and third trimesters 14 types of fetal movements and facial expressions. The analyzed parameters for each trimester of pregnancy can be used for performing antenatal neurodevelopment test, used the first time by Professor Kurjak. Results: After 15-20 minutes 4D ultrasound examination, we found a pattern of fetal behavior for each trimester of pregnancy. Conclusions: Dynamic evaluation of fetal behavior reflects directly the processes of maturation and development of the central nervous system. This can make the difference between normal and abnormal brain development and may be used for early diagnosis of neurological disorders that become manifest in perinatal and postnatal periods. PMID:22205894
Phosphodiesterase4D (PDE4D)--A risk factor for atrial fibrillation and stroke?
Jørgensen, Carina; Yasmeen, Saiqa; Iversen, Helle K; Kruuse, Christina
2015-12-15
Mutations in the gene encoding phosphodiesterase 4D (PDE4D) enzyme are associated with ischemic stroke; however the functional implications of such mutations are not well understood. PDE4D is part of a complex protein family modulating intracellular signalling by cyclic nucleotides. The PDE4 family includes subtypes A-D, all of which show unique intracellular, cellular and tissue distribution. PDE4D is the major subtype expressed in human atrial myocytes and involved in the pathophysiology of arrhythmias, such as atrial fibrillation. The PDE4D enzyme hydrolyses cyclic adenosine monophosphate (cAMP). Though diverging results are reported, several population based studies describe association of various PDE4D single nucleotide polymorphisms (SNP) with cardio-embolic stroke in particular. Functionally, a down regulation of PDE4D variants has been reported in stroke patients. The anti-inflammatory and vasodilator properties of PDE4 inhibitors make them suitable for treatment of stroke and cardiovascular disease. PDE4D has recently been suggested as factor in atrial fibrillation. This review summarizes the possible function of PDE4D in the brain, heart, and vasculature. Further, association of the described SNPs, in particular, with cardioembolic stroke, is reviewed. Current findings on the PDE4D mutations suggest functionality involves an increased cardiac risk factor as well as augmented risk of atrial fibrillation. PMID:26671126
4-D ultrafast shear-wave imaging.
Gennisson, Jean-Luc; Provost, Jean; Deffieux, Thomas; Papadacci, Clément; Imbault, Marion; Pernot, Mathieu; Tanter, Mickael
2015-06-01
Over the last ten years, shear wave elastography (SWE) has seen considerable development and is now routinely used in clinics to provide mechanical characterization of tissues to improve diagnosis. The most advanced technique relies on the use of an ultrafast scanner to generate and image shear waves in real time in a 2-D plane at several thousands of frames per second. We have recently introduced 3-D ultrafast ultrasound imaging to acquire with matrix probes the 3-D propagation of shear waves generated by a dedicated radiation pressure transducer in a single acquisition. In this study, we demonstrate 3-D SWE based on ultrafast volumetric imaging in a clinically applicable configuration. A 32 × 32 matrix phased array driven by a customized, programmable, 1024-channel ultrasound system was designed to perform 4-D shear-wave imaging. A matrix phased array was used to generate and control in 3-D the shear waves inside the medium using the acoustic radiation force. The same matrix array was used with 3-D coherent plane wave compounding to perform high-quality ultrafast imaging of the shear wave propagation. Volumetric ultrafast acquisitions were then beamformed in 3-D using a delay-and-sum algorithm. 3-D volumetric maps of the shear modulus were reconstructed using a time-of-flight algorithm based on local multiscale cross-correlation of shear wave profiles in the three main directions using directional filters. Results are first presented in an isotropic homogeneous and elastic breast phantom. Then, a full 3-D stiffness reconstruction of the breast was performed in vivo on healthy volunteers. This new full 3-D ultrafast ultrasound system paves the way toward real-time 3-D SWE. PMID:26067040
Relative charge transfer cross section from Rb (4d)
NASA Astrophysics Data System (ADS)
Shah, M. H.; Camp, H. A.; Trachy, M. L.; Fléchard, X.; Gearba, M. A.; Nguyen, H.; Brédy, R.; Lundeen, S. R.; Depaola, B. D.
2005-08-01
Relative charge transfer cross section measurements for the excited state Rb(4d) with 7keV Na+ is reported. The specific channels reported are Na++Rb(4d5/2)→Na(nl)+Rb+ , where the dominant transfer cross sections channels were nl=3d and 4s . Using a combination of a magneto-optical trap and recoil ion momentum spectroscopy (MOTRIMS methodology), the cross sections were measured relative to the previously studied Na++Rb(5s,5p) systems at the same collision energy.
Relative charge transfer cross section from Rb(4d)
Shah, M.H.; Camp, H.A.; Trachy, M.L.; De Paola, B.D.; Flechard, X.; Gearba, M.A.; Nguyen, H.; Bredy, R.; Lundeen, S.R.
2005-08-15
Relative charge transfer cross section measurements for the excited state Rb(4d) with 7 keV Na{sup +} is reported. The specific channels reported are Na{sup +}+Rb(4d{sub 5/2}){yields}Na(nl)+Rb{sup +}, where the dominant transfer cross sections channels were nl=3d and 4s. Using a combination of a magneto-optical trap and recoil ion momentum spectroscopy (MOTRIMS methodology), the cross sections were measured relative to the previously studied Na{sup +}+Rb(5s,5p) systems at the same collision energy.
Dynamic granularity of imaging systems
Geissel, Matthias; Smith, Ian C.; Shores, Jonathon E.; Porter, John L.
2015-11-04
Imaging systems that include a specific source, imaging concept, geometry, and detector have unique properties such as signal-to-noise ratio, dynamic range, spatial resolution, distortions, and contrast. Some of these properties are inherently connected, particularly dynamic range and spatial resolution. It must be emphasized that spatial resolution is not a single number but must be seen in the context of dynamic range and consequently is better described by a function or distribution. We introduce the “dynamic granularity” Gdyn as a standardized, objective relation between a detector’s spatial resolution (granularity) and dynamic range for complex imaging systems in a given environment rathermore » than the widely found characterization of detectors such as cameras or films by themselves. We found that this relation can partly be explained through consideration of the signal’s photon statistics, background noise, and detector sensitivity, but a comprehensive description including some unpredictable data such as dust, damages, or an unknown spectral distribution will ultimately have to be based on measurements. Measured dynamic granularities can be objectively used to assess the limits of an imaging system’s performance including all contributing noise sources and to qualify the influence of alternative components within an imaging system. Our article explains the construction criteria to formulate a dynamic granularity and compares measured dynamic granularities for different detectors used in the X-ray backlighting scheme employed at Sandia’s Z-Backlighter facility.« less
Dynamic granularity of imaging systems
Geissel, Matthias; Smith, Ian C.; Shores, Jonathon E.; Porter, John L.
2015-11-04
Imaging systems that include a specific source, imaging concept, geometry, and detector have unique properties such as signal-to-noise ratio, dynamic range, spatial resolution, distortions, and contrast. Some of these properties are inherently connected, particularly dynamic range and spatial resolution. It must be emphasized that spatial resolution is not a single number but must be seen in the context of dynamic range and consequently is better described by a function or distribution. We introduce the “dynamic granularity” G_{dyn} as a standardized, objective relation between a detector’s spatial resolution (granularity) and dynamic range for complex imaging systems in a given environment rather than the widely found characterization of detectors such as cameras or films by themselves. We found that this relation can partly be explained through consideration of the signal’s photon statistics, background noise, and detector sensitivity, but a comprehensive description including some unpredictable data such as dust, damages, or an unknown spectral distribution will ultimately have to be based on measurements. Measured dynamic granularities can be objectively used to assess the limits of an imaging system’s performance including all contributing noise sources and to qualify the influence of alternative components within an imaging system. Our article explains the construction criteria to formulate a dynamic granularity and compares measured dynamic granularities for different detectors used in the X-ray backlighting scheme employed at Sandia’s Z-Backlighter facility.
The scientific value of 4D visualizations
NASA Astrophysics Data System (ADS)
Minster, J.; Olsen, K.; Day, S.; Moore, R.; Jordan, T. H.; Maechling, P.; Chourasia, A.
2006-12-01
Significant scientific insights derive from viewing measured, or calculated three-dimensional, time-dependent -- that is four-dimensional-- fields. This issue cuts across all disciplines of Earth Sciences. Addressing it calls for close collaborations between "domain" scientists and "IT" visualization specialists. Techniques to display such 4D fields in a intuitive way are a major challenge, especially when the relevant variables to be displayed are not scalars but tensors. This talk will illustrate some attempts to deal with this challenge, using seismic wave fields as specific objects to display. We will highlight how 4D displays can help address very difficult issues of significant scientific import.
Dynamic stability of maglev systems
Cai, Y.; Chen, S.S.; Mulcahy, T.M.; Rote, D.M.
1994-05-01
Because dynamic instabilities are not acceptable in any commercial maglev system, it is important to consider dynamic instability in the development of all maglev systems. This study considers the stability of maglev systems based on experimental data, scoping calculations, and simple mathematical models. Divergence and flutter are obtained for coupled vibration of a three-degree-of-freedom maglev vehicle on a guideway consisting of double L-shaped aluminum segments. The theory and analysis developed in this study provides basic stability characteristics and identifies future research needs for maglev systems.
Dynamic stability of maglev systems
Cai, Y.; Chen, S.S.; Mulcahy, T.M.; Rote, D.M.
1992-09-01
Since the occurrence of dynamic instabilities is not acceptable for any commercial maglev systems, it is important to consider the dynamic instability in the development of all maglev systems. This study is to consider the stability of maglev systems based on experimental data, scoping calculations and simple mathematical models. Divergence and flutter are obtained for coupled vibration of a three-degree-of-freedom maglev vehicle on the guideway which consists of double L-shaped aluminum segments attached to a rotating wheel. The theory and analysis developed in this study provides basic stability characteristics and identifies future research needs for maglev system.
Dynamic stability of maglev systems
Cai, Y.; Chen, S.S.; Mulcahy, T.M.; Rote, D.M.
1992-01-01
Since the occurrence of dynamic instabilities is not acceptable for any commercial maglev systems, it is important to consider the dynamic instability in the development of all maglev systems. This study is to consider the stability of maglev systems based on experimental data, scoping calculations and simple mathematical models. Divergence and flutter are obtained for coupled vibration of a three-degree-of-freedom maglev vehicle on the guideway which consists of double L-shaped aluminum segments attached to a rotating wheel. The theory and analysis developed in this study provides basic stability characteristics and identifies future research needs for maglev system.
Realization of dynamical electronic systems
NASA Astrophysics Data System (ADS)
Hammari, Elena; Catthoor, Francky; Iasemidis, Leonidas; Kjeldsberg, Per Gunnar; Huisken, Jos; Tsakalis, Konstantinos
2014-04-01
This article gives an overview of a methodology for building dynamical electronic systems. As an example a part of a system for epileptic seizure prediction is used, which monitors EEG signals and continuously calculates the largest short-term Lyapunov exponents. In dynamical electronic systems, the cost of exploitation, for instance energy consumption, may vary substantially with the values of input signals. In addition, the functions describing the variations are not known at the time the system is designed. As a result, the architecture of the system must accommodate for the worst case exploitation costs, which rapidly exceed the available resources (for instance battery life) when accumulated over time. The presented system scenario methodology solves these challenges by identifying at design time groups of possible exploitation costs, called system scenarios, and implementing a mechanism to detect system scenarios at run time and re-configure the system to cost-efficiently accommodate them. During reconfiguration, the optimized system architecture settings for the active system scenario are selected and the total exploitation cost is reduced. When the dynamic behavior is due to input data variables with a large number of possible values, current techniques for bottom-up scenario identification and detection becomes too complex. A new top-down technique, based on polygonal regions, is presented in this paper. The results for the example system indicate that with 10 system scenarios the average energy consumption of the system can be reduced by 28% and brought within 5% of the theoretically best solution.
NASA Technical Reports Server (NTRS)
Wisdom, Jack
1987-01-01
The rotational dynamics of irregularly shaped satellites and the origin of Kirkwood Gaps are discussed. The chaotic tumbling of Hyperion and the anomalously low eccentricity of Deimos are examined. The Digital Orrery is used to explore the phase space of the ellipic restricted three body problem near the principal commensurabilities (2/1, 5/2, 3/1, and 3/2). The results for the 3/1 commensurability are in close agreement with those found earlier with the algebraic mapping method. Large chaotic zones are associated with the 3/1, 2/1 and 5/2 resonances, where there are gaps in the distribution of asteroids. The region near the 3/2 resonance, where the Hilda group of asteroids is located, is largely devoid of chaotic behavior. Thus, there is a qualitative agreement between the character of the motion and the distribution of asteroids.
SU-C-9A-06: The Impact of CT Image Used for Attenuation Correction in 4D-PET
Cui, Y; Bowsher, J; Yan, S; Cai, J; Das, S; Yin, F
2014-06-01
Purpose: To evaluate the appropriateness of using 3D non-gated CT image for attenuation correction (AC) in a 4D-PET (gated PET) imaging protocol used in radiotherapy treatment planning simulation. Methods: The 4D-PET imaging protocol in a Siemens PET/CT simulator (Biograph mCT, Siemens Medical Solutions, Hoffman Estates, IL) was evaluated. CIRS Dynamic Thorax Phantom (CIRS Inc., Norfolk, VA) with a moving glass sphere (8 mL) in the middle of its thorax portion was used in the experiments. The glass was filled with {sup 18}F-FDG and was in a longitudinal motion derived from a real patient breathing pattern. Varian RPM system (Varian Medical Systems, Palo Alto, CA) was used for respiratory gating. Both phase-gating and amplitude-gating methods were tested. The clinical imaging protocol was modified to use three different CT images for AC in 4D-PET reconstruction: first is to use a single-phase CT image to mimic actual clinical protocol (single-CT-PET); second is to use the average intensity projection CT (AveIP-CT) derived from 4D-CT scanning (AveIP-CT-PET); third is to use 4D-CT image to do the phase-matched AC (phase-matching- PET). Maximum SUV (SUVmax) and volume of the moving target (glass sphere) with threshold of 40% SUVmax were calculated for comparison between 4D-PET images derived with different AC methods. Results: The SUVmax varied 7.3%±6.9% over the breathing cycle in single-CT-PET, compared to 2.5%±2.8% in AveIP-CT-PET and 1.3%±1.2% in phasematching PET. The SUVmax in single-CT-PET differed by up to 15% from those in phase-matching-PET. The target volumes measured from single- CT-PET images also presented variations up to 10% among different phases of 4D PET in both phase-gating and amplitude-gating experiments. Conclusion: Attenuation correction using non-gated CT in 4D-PET imaging is not optimal process for quantitative analysis. Clinical 4D-PET imaging protocols should consider phase-matched 4D-CT image if available to achieve better accuracy.
Biologically inspired dynamic material systems.
Studart, André R
2015-03-01
Numerous examples of material systems that dynamically interact with and adapt to the surrounding environment are found in nature, from hair-based mechanoreceptors in animals to self-shaping seed dispersal units in plants to remodeling bone in vertebrates. Inspired by such fascinating biological structures, a wide range of synthetic material systems have been created to replicate the design concepts of dynamic natural architectures. Examples of biological structures and their man-made counterparts are herein revisited to illustrate how dynamic and adaptive responses emerge from the intimate microscale combination of building blocks with intrinsic nanoscale properties. By using top-down photolithographic methods and bottom-up assembly approaches, biologically inspired dynamic material systems have been created 1) to sense liquid flow with hair-inspired microelectromechanical systems, 2) to autonomously change shape by utilizing plantlike heterogeneous architectures, 3) to homeostatically influence the surrounding environment through self-regulating adaptive surfaces, and 4) to spatially concentrate chemical species by using synthetic microcompartments. The ever-increasing complexity and remarkable functionalities of such synthetic systems offer an encouraging perspective to the rich set of dynamic and adaptive properties that can potentially be implemented in future man-made material systems.
Self-Supervised Dynamical Systems
NASA Technical Reports Server (NTRS)
Zak, Michail
2003-01-01
Some progress has been made in a continuing effort to develop mathematical models of the behaviors of multi-agent systems known in biology, economics, and sociology (e.g., systems ranging from single or a few biomolecules to many interacting higher organisms). Living systems can be characterized by nonlinear evolution of probability distributions over different possible choices of the next steps in their motions. One of the main challenges in mathematical modeling of living systems is to distinguish between random walks of purely physical origin (for instance, Brownian motions) and those of biological origin. Following a line of reasoning from prior research, it has been assumed, in the present development, that a biological random walk can be represented by a nonlinear mathematical model that represents coupled mental and motor dynamics incorporating the psychological concept of reflection or self-image. The nonlinear dynamics impart the lifelike ability to behave in ways and to exhibit patterns that depart from thermodynamic equilibrium. Reflection or self-image has traditionally been recognized as a basic element of intelligence. The nonlinear mathematical models of the present development are denoted self-supervised dynamical systems. They include (1) equations of classical dynamics, including random components caused by uncertainties in initial conditions and by Langevin forces, coupled with (2) the corresponding Liouville or Fokker-Planck equations that describe the evolutions of probability densities that represent the uncertainties. The coupling is effected by fictitious information-based forces, denoted supervising forces, composed of probability densities and functionals thereof. The equations of classical mechanics represent motor dynamics that is, dynamics in the traditional sense, signifying Newton s equations of motion. The evolution of the probability densities represents mental dynamics or self-image. Then the interaction between the physical and
Dynamically reconfigurable photovoltaic system
Okandan, Murat; Nielson, Gregory N.
2016-05-31
A PV system composed of sub-arrays, each having a group of PV cells that are electrically connected to each other. A power management circuit for each sub-array has a communications interface and serves to connect or disconnect the sub-array to a programmable power grid. The power grid has bus rows and bus columns. A bus management circuit is positioned at a respective junction of a bus column and a bus row and is programmable through its communication interface to connect or disconnect a power path in the grid. As a result, selected sub-arrays are connected by selected power paths to be in parallel so as to produce a low system voltage, and, alternately in series so as to produce a high system voltage that is greater than the low voltage by at least a factor of ten.
4D flow mri post-processing strategies for neuropathologies
NASA Astrophysics Data System (ADS)
Schrauben, Eric Mathew
4D flow MRI allows for the measurement of a dynamic 3D velocity vector field. Blood flow velocities in large vascular territories can be qualitatively visualized with the added benefit of quantitative probing. Within cranial pathologies theorized to have vascular-based contributions or effects, 4D flow MRI provides a unique platform for comprehensive assessment of hemodynamic parameters. Targeted blood flow derived measurements, such as flow rate, pulsatility, retrograde flow, or wall shear stress may provide insight into the onset or characterization of more complex neuropathologies. Therefore, the thorough assessment of each parameter within the context of a given disease has important medical implications. Not surprisingly, the last decade has seen rapid growth in the use of 4D flow MRI. Data acquisition sequences are available to researchers on all major scanner platforms. However, the use has been limited mostly to small research trials. One major reason that has hindered the more widespread use and application in larger clinical trials is the complexity of the post-processing tasks and the lack of adequate tools for these tasks. Post-processing of 4D flow MRI must be semi-automated, fast, user-independent, robust, and reliably consistent for use in a clinical setting, within large patient studies, or across a multicenter trial. Development of proper post-processing methods coupled with systematic investigation in normal and patient populations pushes 4D flow MRI closer to clinical realization while elucidating potential underlying neuropathological origins. Within this framework, the work in this thesis assesses venous flow reproducibility and internal consistency in a healthy population. A preliminary analysis of venous flow parameters in healthy controls and multiple sclerosis patients is performed in a large study employing 4D flow MRI. These studies are performed in the context of the chronic cerebrospinal venous insufficiency hypothesis. Additionally, a
Managing Complex Dynamical Systems
ERIC Educational Resources Information Center
Cox, John C.; Webster, Robert L.; Curry, Jeanie A.; Hammond, Kevin L.
2011-01-01
Management commonly engages in a variety of research designed to provide insight into the motivation and relationships of individuals, departments, organizations, etc. This paper demonstrates how the application of concepts associated with the analysis of complex systems applied to such data sets can yield enhanced insights for managerial action.
Quintremil, Sebastián; Alberti, Carolina; Rivera, Matías; Medina, Fernando; Puente, Javier; Cartier, Luis; Ramírez, Eugenio; Tanaka, Yuetsu; Valenzuela, M Antonieta
2016-01-01
Human lymphotropic virus type 1 (HTLV-1) is a retrovirus causing HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a neurodegenerative central nervous system (CNS) axonopathy. This virus mainly infects CD4(+) T lymphocytes without evidence of neuronal infection. Viral Tax, secreted from infected lymphocytes infiltrated in the CNS, is proposed to alter intracellular pathways related to axonal cytoskeleton dynamics, producing neurological damage. Previous reports showed a higher proteolytic release of soluble Semaphorin 4D (sSEMA-4D) from CD4(+) T cells infected with HTLV-1. Soluble SEMA-4D binds to its receptor Plexin-B1, activating axonal growth collapse pathways in the CNS. In the current study, an increase was found in both SEMA-4D in CD4(+) T cells and sSEMA-4D released to the culture medium of peripheral blood mononuclear cells (PBMCs) from HAM/TSP patients compared to asymptomatic carriers and healthy donors. After a 16-h culture, infected PBMCs showed significantly higher levels of CRMP-2 phosphorylated at Ser(522). The effect was blocked either with anti-Tax or anti-SEMA-4D antibodies. The interaction of Tax and sSEMA-4D was found in secreted medium of PBMCs in patients, which might be associated with a leading role of Tax with the SEMA-4D-Plexin-B1 signaling pathway. In infected PBMCs, the migratory response after transwell assay showed that sSEMA-4D responding cells were CD4(+)Tax(+) T cells with a high CRMP-2 pSer(522) content. In the present study, the participation of Tax-sSEMA-4D in the reduction in neurite growth in PC12 cells produced by MT2 (HTLV-1-infected cell line) culture medium was observed. These results lead to the participation of plexins in the reported effects of infected lymphocytes on neuronal cells. PMID:26389656
Constrain static target kinetic iterative image reconstruction for 4D cardiac CT imaging
NASA Astrophysics Data System (ADS)
Alessio, Adam M.; La Riviere, Patrick J.
2011-03-01
Iterative image reconstruction offers improved signal to noise properties for CT imaging. A primary challenge with iterative methods is the substantial computation time. This computation time is even more prohibitive in 4D imaging applications, such as cardiac gated or dynamic acquisition sequences. In this work, we propose only updating the time-varying elements of a 4D image sequence while constraining the static elements to be fixed or slowly varying in time. We test the method with simulations of 4D acquisitions based on measured cardiac patient data from a) a retrospective cardiac-gated CT acquisition and b) a dynamic perfusion CT acquisition. We target the kinetic elements with one of two methods: 1) position a circular ROI on the heart, assuming area outside ROI is essentially static throughout imaging time; and 2) select varying elements from the coefficient of variation image formed from fast analytic reconstruction of all time frames. Targeted kinetic elements are updated with each iteration, while static elements remain fixed at initial image values formed from the reconstruction of data from all time frames. Results confirm that the computation time is proportional to the number of targeted elements; our simulations suggest that <30% of elements need to be updated in each frame leading to >3 times reductions in reconstruction time. The images reconstructed with the proposed method have matched mean square error with full 4D reconstruction. The proposed method is amenable to most optimization algorithms and offers the potential for significant computation improvements, which could be traded off for more sophisticated system models or penalty terms.
Experimenting with the GMAO 4D Data Assimilation
NASA Technical Reports Server (NTRS)
Todling, R.; El Akkraoui, A.; Errico, R. M.; Guo, J.; Kim, J.; Kliest, D.; Parrish, D. F.; Suarez, M.; Trayanov, A.; Tremolet, Yannick; Whitaker, J.
2012-01-01
The Global Modeling and Assimilation Office (GMAO) has been working to promote its prototype four-dimensional variational (4DVAR) system to a version that can be exercised at operationally desirable configurations. Beyond a general circulation model (GeM) and an analysis system, traditional 4DV AR requires availability of tangent linear (TL) and adjoint (AD) models of the corresponding GeM. The GMAO prototype 4DVAR uses the finite-volume-based GEOS GeM and the Grid-point Statistical Interpolation (GSI) system for the first two, and TL and AD models derived ITom an early version of the finite-volume hydrodynamics that is scientifically equivalent to the present GEOS nonlinear GeM but computationally rather outdated. Specifically, the TL and AD models hydrodynamics uses a simple (I-dimensional) latitudinal MPI domain decomposition, which has consequent low scalability and prevents the prototype 4DV AR ITom being used in realistic applications. In the near future, GMAO will be upgrading its operational GEOS GCM (and assimilation system) to use a cubed-sphere-based hydrodynamics. This versions of the dynamics scales to thousands of processes and has led to a decision to re-derive the TL and AD models for this more modern dynamics, thus taking advantage of a two-dimensional MPI decomposition and improved scalability properties. With the aid of the Transformation of Algorithms in FORTRAN (l'AF) automatic adjoint generation tool and some hand-coding, a version of the cubed-sphere-based TL and AD models, with a simplified vertical diffusion scheme, is now available, enabling multiple configurations of standard implementations of 4DV AR in GEOS. Concurrent to this development, collaboration with the National Centers for Environmental Prediction (NCEP) and the Earth System Research Laboratory (ESRL) has allowed GMAO to implement a hybrid-ensemble capability within the GEOS data assimilation system. Both 3Dand 4D-ensemble capabilities are presently available thus allowing
NASA Astrophysics Data System (ADS)
Price, G. J.; Marchant, T. E.; Parkhurst, J. M.; Sharrock, P. J.; Whitfield, G. A.; Moore, C. J.
2011-03-01
In image guided radiotherapy (IGRT) two of the most promising recent developments are four dimensional cone beam CT (4D CBCT) and dynamic optical metrology of patient surfaces. 4D CBCT is now becoming commercially available and finds use in treatment planning and verification, and whilst optical monitoring is a young technology, its ability to measure during treatment delivery without dose consequences has led to its uptake in many institutes. In this paper, we demonstrate the use of dynamic patient surfaces, simultaneously captured during CBCT acquisition using an optical sensor, to phase sort projection images for 4D CBCT volume reconstruction. The dual modality approach we describe means that in addition to 4D volumetric data, the system provides correlated wide field measurements of the patient's skin surface with high spatial and temporal resolution. As well as the value of such complementary data in verification and motion analysis studies, it introduces flexibility into the acquisition of the signal required for phase sorting. The specific technique used may be varied according to individual patient circumstances and the imaging target. We give details of three different methods of obtaining a suitable signal from the optical surfaces: simply following the motion of triangulation spots used to calibrate the surfaces' absolute height; monitoring the surface height in a single, arbitrarily selected, camera pixel; and tracking, in three dimensions, the movement of a surface feature. In addition to describing the system and methodology, we present initial results from a case study oesophageal cancer patient.
Nondipole Effects in Xe 4d Photoemission
Hemmers, O; Guillemin, R; Wolska, A; Lindle, D W; Rolles, D; Cheng, K T; Johnson, W R; Zhou, H L; Manson, S T
2004-07-14
We measured the nondipole parameters for the spin-orbit doublets Xe 4d{sub 5/2} and Xe 4d{sub 3/2} over a photon-energy range from 100 eV to 250 eV at beamline 8.0.1.3 of the Advanced Light Source at the Lawrence Berkeley National Laboratory. Significant nondipole effects are found at relatively low energies as a result of Cooper minima in dipole channels and interchannel coupling in quadrupole channels. Most importantly, sharp disagreement between experiment and theory, when otherwise excellent agreement was expected, has provided the first evidence of satellite two-electron quadrupole photoionization transitions, along with their crucial importance for a quantitatively accurate theory.
Waddington, Dynamic Systems, and Epigenetics
Tronick, Ed; Hunter, Richard G.
2016-01-01
Waddington coined the term “epigenetic” to attempt to explain the complex, dynamic interactions between the developmental environment and the genome that led to the production of phenotype. Waddington's thoughts on the importance of both adaptability and canalization of phenotypic development are worth recalling as well, as they emphasize the available range for epigenetic action and the importance of environmental feedback (or lack thereof) in the development of complex traits. We suggest that a dynamic systems view fits well with Waddington's conception of epigenetics in the developmental context, as well as shedding light on the study of the molecular epigenetic effects of the environment on brain and behavior. Further, the dynamic systems view emphasizes the importance of the multi-directional interchange between the organism, the genome and various aspects of the environment to the ultimate phenotype. PMID:27375447
Dynamics of Variable Mass Systems
NASA Technical Reports Server (NTRS)
Eke, Fidelis O.
1998-01-01
This report presents the results of an investigation of the effects of mass loss on the attitude behavior of spinning bodies in flight. The principal goal is to determine whether there are circumstances under which the motion of variable mass systems can become unstable in the sense that their transverse angular velocities become unbounded. Obviously, results from a study of this kind would find immediate application in the aerospace field. The first part of this study features a complete and mathematically rigorous derivation of a set of equations that govern both the translational and rotational motions of general variable mass systems. The remainder of the study is then devoted to the application of the equations obtained to a systematic investigation of the effect of various mass loss scenarios on the dynamics of increasingly complex models of variable mass systems. It is found that mass loss can have a major impact on the dynamics of mechanical systems, including a possible change in the systems stability picture. Factors such as nozzle geometry, combustion chamber geometry, propellant's initial shape, size and relative mass, and propellant location can all have important influences on the system's dynamic behavior. The relative importance of these parameters on-system motion are quantified in a way that is useful for design purposes.
SU-E-J-192: Verification of 4D-MRI Internal Target Volume Using Cine MRI
Lafata, K; Czito, B; Palta, M; Bashir, M; Yin, F; Cai, J
2014-06-01
Purpose: To investigate the accuracy of 4D-MRI in determining the Internal Target Volume (ITV) used in radiation oncology treatment planning of liver cancers. Cine MRI is used as the standard baseline in establishing the feasibility and accuracy of 4D-MRI tumor motion within the liver. Methods: IRB approval was obtained for this retrospective study. Analysis was performed on MR images from four patients receiving external beam radiation therapy for liver cancer at our institution. Eligible patients received both Cine and 4D-MRI scans before treatment. Cine images were acquired sagittally in real time at a slice bisecting the tumor, while 4D images were acquired volumetrically. Cine MR DICOM headers were manipulated such that each respiratory frame was assigned a unique slice location. This approach permitted the treatment planning system (Eclipse, Varian Medical Systems) to recognize a complete respiratory cycle as a “volume”, where the gross tumor was contoured temporally. Software was developed to calculate the union of all frame contours in the structure set, resulting in the corresponding plane of the ITV projecting through the middle of the tumor, defined as the Internal Target Area (ITA). This was repeated for 4D-MRI, at the corresponding slice location, allowing a direct comparison of ITAs obtained from each modality. Results: Four patients have been analyzed. ITAs contoured from 4D-MRI correlate with contours from Cine MRI. The mean error of 4D values relative to Cine values is 7.67 +/− 2.55 %. No single ITA contoured from 4D-MRI demonstrated more than 10.5 % error compared to its Cine MRI counterpart. Conclusion: Motion management is a significant aspect of treatment planning within dynamic environments such as the liver, where diaphragmatic and cardiac activity influence plan accuracy. This small pilot study suggests that 4D-MRI based ITA measurements agree with Cine MRI based measurements, an important step towards clinical implementation. NIH 1R21
Dynamic stability of maglev systems
Cai, Y.; Chen, S.S.; Mulcahy, T.M.; Rote, D.M.
1992-04-01
Because dynamic instability is not acceptable for any commercial maglev systems, it is important to consider this phenomenon in the development of all maglev systems. This study considers the stability of maglev systems based on experimental data, scoping calculations, and simple mathematical models. Divergence and flutter are obtained for coupled vibration of a three-degree-of-freedom maglev vehicle on a guideway consisting of double L-shaped aluminum segments attached to a rotating wheel. The theory and analysis developed in this study identifies basic stability characteristics and future research needs of maglev systems.
Dynamics of immune system vulnerabilities
NASA Astrophysics Data System (ADS)
Stromberg, Sean P.
The adaptive immune system can be viewed as a complex system, which adapts, over time, to reflect the history of infections experienced by the organism. Understanding its operation requires viewing it in terms of tradeoffs under constraints and evolutionary history. It typically displays "robust, yet fragile" behavior, meaning common tasks are robust to small changes but novel threats or changes in environment can have dire consequences. In this dissertation we use mechanistic models to study several biological processes: the immune response, the homeostasis of cells in the lymphatic system, and the process that normally prevents autoreactive cells from entering the lymphatic system. Using these models we then study the effects of these processes interacting. We show that the mechanisms that regulate the numbers of cells in the immune system, in conjunction with the immune response, can act to suppress autoreactive cells from proliferating, thus showing quantitatively how pathogenic infections can suppress autoimmune disease. We also show that over long periods of time this same effect can thin the repertoire of cells that defend against novel threats, leading to an age correlated vulnerability. This vulnerability is shown to be a consequence of system dynamics, not due to degradation of immune system components with age. Finally, modeling a specific tolerance mechanism that normally prevents autoimmune disease, in conjunction with models of the immune response and homeostasis we look at the consequences of the immune system mistakenly incorporating pathogenic molecules into its tolerizing mechanisms. The signature of this dynamic matches closely that of the dengue virus system.
Dynamical systems probabilistic risk assessment.
Denman, Matthew R.; Ames, Arlo Leroy
2014-03-01
Probabilistic Risk Assessment (PRA) is the primary tool used to risk-inform nuclear power regulatory and licensing activities. Risk-informed regulations are intended to reduce inherent conservatism in regulatory metrics (e.g., allowable operating conditions and technical specifications) which are built into the regulatory framework by quantifying both the total risk profile as well as the change in the risk profile caused by an event or action (e.g., in-service inspection procedures or power uprates). Dynamical Systems (DS) analysis has been used to understand unintended time-dependent feedbacks in both industrial and organizational settings. In dynamical systems analysis, feedback loops can be characterized and studied as a function of time to describe the changes to the reliability of plant Structures, Systems and Components (SSCs). While DS has been used in many subject areas, some even within the PRA community, it has not been applied toward creating long-time horizon, dynamic PRAs (with time scales ranging between days and decades depending upon the analysis). Understanding slowly developing dynamic effects, such as wear-out, on SSC reliabilities may be instrumental in ensuring a safely and reliably operating nuclear fleet. Improving the estimation of a plant's continuously changing risk profile will allow for more meaningful risk insights, greater stakeholder confidence in risk insights, and increased operational flexibility.
4D imaging of protein aggregation in live cells.
Spokoini, Rachel; Shamir, Maya; Keness, Alma; Kaganovich, Daniel
2013-01-01
ubiquitinated are diverted to the IPOD, where they are actively aggregated in a protective compartment. Up until this point, the methodological paradigm of live-cell fluorescence microscopy has largely been to label proteins and track their locations in the cell at specific time-points and usually in two dimensions. As new technologies have begun to grant experimenters unprecedented access to the submicron scale in living cells, the dynamic architecture of the cytosol has come into view as a challenging new frontier for experimental characterization. We present a method for rapidly monitoring the 3D spatial distributions of multiple fluorescently labeled proteins in the yeast cytosol over time. 3D timelapse (4D imaging) is not merely a technical challenge; rather, it also facilitates a dramatic shift in the conceptual framework used to analyze cellular structure. We utilize a cytosolic folding sensor protein in live yeast to visualize distinct fates for misfolded proteins in cellular aggregation quality control, using rapid 4D fluorescent imaging. The temperature sensitive mutant of the Ubc9 protein (Ubc9(ts)) is extremely effective both as a sensor of cellular proteostasis, and a physiological model for tracking aggregation quality control. As with most ts proteins, Ubc9(ts) is fully folded and functional at permissive temperatures due to active cellular chaperones. Above 30 ° C, or when the cell faces misfolding stress, Ubc9(ts) misfolds and follows the fate of a native globular protein that has been misfolded due to mutation, heat denaturation, or oxidative damage. By fusing it to GFP or other fluorophores, it can be tracked in 3D as it forms Stress Foci, or is directed to JUNQ or IPOD. PMID:23608881
Cai, Jing; Chang, Zheng; Wang, Zhiheng; Paul Segars, William; Yin, Fang-Fang
2011-01-01
Purpose: Four-dimensional computed tomography (4D-CT) has been widely used in radiation therapy to assess patient-specific breathing motion for determining individual safety margins. However, it has two major drawbacks: low soft-tissue contrast and an excessive imaging dose to the patient. This research aimed to develop a clinically feasible four-dimensional magnetic resonance imaging (4D-MRI) technique to overcome these limitations. Methods: The proposed 4D-MRI technique was achieved by continuously acquiring axial images throughout the breathing cycle using fast 2D cine-MR imaging, and then retrospectively sorting the images by respiratory phase. The key component of the technique was the use of body area (BA) of the axial MR images as an internal respiratory surrogate to extract the breathing signal. The validation of the BA surrogate was performed using 4D-CT images of 12 cancer patients by comparing the respiratory phases determined using the BA method to those determined clinically using the Real-time position management (RPM) system. The feasibility of the 4D-MRI technique was tested on a dynamic motion phantom, the 4D extended Cardiac Torso (XCAT) digital phantom, and two healthy human subjects. Results: Respiratory phases determined from the BA matched closely to those determined from the RPM: mean (±SD) difference in phase: −3.9% (±6.4%); mean (±SD) absolute difference in phase: 10.40% (±3.3%); mean (±SD) correlation coefficient: 0.93 (±0.04). In the motion phantom study, 4D-MRI clearly showed the sinusoidal motion of the phantom; image artifacts observed were minimal to none. Motion trajectories measured from 4D-MRI and 2D cine-MRI (used as a reference) matched excellently: the mean (±SD) absolute difference in motion amplitude: −0.3 (±0.5) mm. In the 4D-XCAT phantom study, the simulated “4D-MRI” images showed good consistency with the original 4D-XCAT phantom images. The motion trajectory of the hypothesized “tumor” matched
Vehicle systems: coupled and interactive dynamics analysis
NASA Astrophysics Data System (ADS)
Vantsevich, Vladimir V.
2014-11-01
This article formulates a new direction in vehicle dynamics, described as coupled and interactive vehicle system dynamics. Formalised procedures and analysis of case studies are presented. An analytical consideration, which explains the physics of coupled system dynamics and its consequences for dynamics of a vehicle, is given for several sets of systems including: (i) driveline and suspension of a 6×6 truck, (ii) a brake mechanism and a limited slip differential of a drive axle and (iii) a 4×4 vehicle steering system and driveline system. The article introduces a formal procedure to turn coupled system dynamics into interactive dynamics of systems. A new research direction in interactive dynamics of an active steering and a hybrid-electric power transmitting unit is presented and analysed to control power distribution between the drive axles of a 4×4 vehicle. A control strategy integrates energy efficiency and lateral dynamics by decoupling dynamics of the two systems thus forming their interactive dynamics.
Tai, A; Prior, P; Gore, E; Johnstone, C; Li, X
2015-06-15
Purpose: 4DCT has been widely used to generate internal tumor volume (ITV) for a lung tumor for treatment planning. However, lung tumors may show different respiratory motion on the treatment day. The purpose of this study is to evaluate 4D KV conebeam computed tomography (CBCT) for monitoring tumor interfractional motion variation between simulation and each fraction of stereotactic body radiation therapy (SBRT) for lung cancer. Methods: 4D KV CBCT was acquired with the Elekta XVI system. The accuracy of 4D KV CBCT for image-guided radiation therapy (IGRT) was tested with a dynamic thorax motion phantom (CIRS, Virginia) with a linear amplitude of 2 cm. In addition, an adult anthropomorphic phantom (Alderson, Rando) with optically stimulated luminescence (OSL) dosimeters embedded at the center and periphery of a slab of solid water was used to measure the dose of 4D KV CBCT and to compare it with the dose with 3D KV CBCT. The image registration was performed by aligning\\ each phase images of 4D KV CBCT to the planning images and the final couch shifts were calculated as a mean of all these individual shifts along each direction.A workflow was established based on these quality assurance tests for lung cancer patients. Results: 4D KV CBCT does not increase imaging dose in comparison to 3D KV CBCT. Acquisition of 4D KV CBCT is 4 minutes as compared to 2 minutes for 3D KV CBCT. Most of patients showed a small daily variation of tumor respiratory motion about 2 mm. However, some patients may have more than 5 mm variations of tumor respiratory motion. Conclusion: The radiation dose does not increase with 4D KV CBCT. 4D KV CBCT is a useful tool for monitoring interfractional variations of tumor respiratory motion before SBRT of lung cancer patients.
NASA Astrophysics Data System (ADS)
Ge, Qi; Dunn, Conner K.; Qi, H. Jerry; Dunn, Martin L.
2014-09-01
Recent advances in three dimensional (3D) printing technology that allow multiple materials to be printed within each layer enable the creation of materials and components with precisely controlled heterogeneous microstructures. In addition, active materials, such as shape memory polymers, can be printed to create an active microstructure within a solid. These active materials can subsequently be activated in a controlled manner to change the shape or configuration of the solid in response to an environmental stimulus. This has been termed 4D printing, with the 4th dimension being the time-dependent shape change after the printing. In this paper, we advance the 4D printing concept to the design and fabrication of active origami, where a flat sheet automatically folds into a complicated 3D component. Here we print active composites with shape memory polymer fibers precisely printed in an elastomeric matrix and use them as intelligent active hinges to enable origami folding patterns. We develop a theoretical model to provide guidance in selecting design parameters such as fiber dimensions, hinge length, and programming strains and temperature. Using the model, we design and fabricate several active origami components that assemble from flat polymer sheets, including a box, a pyramid, and two origami airplanes. In addition, we directly print a 3D box with active composite hinges and program it to assume a temporary flat shape that subsequently recovers to the 3D box shape on demand.
Hidden attractors in dynamical systems
NASA Astrophysics Data System (ADS)
Dudkowski, Dawid; Jafari, Sajad; Kapitaniak, Tomasz; Kuznetsov, Nikolay V.; Leonov, Gennady A.; Prasad, Awadhesh
2016-06-01
Complex dynamical systems, ranging from the climate, ecosystems to financial markets and engineering applications typically have many coexisting attractors. This property of the system is called multistability. The final state, i.e., the attractor on which the multistable system evolves strongly depends on the initial conditions. Additionally, such systems are very sensitive towards noise and system parameters so a sudden shift to a contrasting regime may occur. To understand the dynamics of these systems one has to identify all possible attractors and their basins of attraction. Recently, it has been shown that multistability is connected with the occurrence of unpredictable attractors which have been called hidden attractors. The basins of attraction of the hidden attractors do not touch unstable fixed points (if exists) and are located far away from such points. Numerical localization of the hidden attractors is not straightforward since there are no transient processes leading to them from the neighborhoods of unstable fixed points and one has to use the special analytical-numerical procedures. From the viewpoint of applications, the identification of hidden attractors is the major issue. The knowledge about the emergence and properties of hidden attractors can increase the likelihood that the system will remain on the most desirable attractor and reduce the risk of the sudden jump to undesired behavior. We review the most representative examples of hidden attractors, discuss their theoretical properties and experimental observations. We also describe numerical methods which allow identification of the hidden attractors.
A Workstation for Interactive Display and Quantitative Analysis of 3-D and 4-D Biomedical Images
Robb, R.A.; Heffeman, P.B.; Camp, J.J.; Hanson, D.P.
1986-01-01
The capability to extract objective and quantitatively accurate information from 3-D radiographic biomedical images has not kept pace with the capabilities to produce the images themselves. This is rather an ironic paradox, since on the one hand the new 3-D and 4-D imaging capabilities promise significant potential for providing greater specificity and sensitivity (i.e., precise objective discrimination and accurate quantitative measurement of body tissue characteristics and function) in clinical diagnostic and basic investigative imaging procedures than ever possible before, but on the other hand, the momentous advances in computer and associated electronic imaging technology which have made these 3-D imaging capabilities possible have not been concomitantly developed for full exploitation of these capabilities. Therefore, we have developed a powerful new microcomputer-based system which permits detailed investigations and evaluation of 3-D and 4-D (dynamic 3-D) biomedical images. The system comprises a special workstation to which all the information in a large 3-D image data base is accessible for rapid display, manipulation, and measurement. The system provides important capabilities for simultaneously representing and analyzing both structural and functional data and their relationships in various organs of the body. This paper provides a detailed description of this system, as well as some of the rationale, background, theoretical concepts, and practical considerations related to system implementation. ImagesFigure 5Figure 7Figure 8Figure 9Figure 10Figure 11Figure 12Figure 13Figure 14Figure 15Figure 16
From dynamical systems to renormalization
Menous, Frédéric
2013-09-15
In this paper we study logarithmic derivatives associated to derivations on completed graded Lie algebra, as well as the existence of inverses. These logarithmic derivatives, when invertible, generalize the exp-log correspondence between a Lie algebra and its Lie group. Such correspondences occur naturally in the study of dynamical systems when dealing with the linearization of vector fields and the non linearizability of a resonant vector fields corresponds to the non invertibility of a logarithmic derivative and to the existence of normal forms. These concepts, stemming from the theory of dynamical systems, can be rephrased in the abstract setting of Lie algebra and the same difficulties as in perturbative quantum field theory (pQFT) arise here. Surprisingly, one can adopt the same ideas as in pQFT with fruitful results such as new constructions of normal forms with the help of the Birkhoff decomposition. The analogy goes even further (locality of counter terms, choice of a renormalization scheme) and shall lead to more interactions between dynamical systems and quantum field theory.
From dynamical systems to renormalization
NASA Astrophysics Data System (ADS)
Menous, Frédéric
2013-09-01
In this paper we study logarithmic derivatives associated to derivations on completed graded Lie algebra, as well as the existence of inverses. These logarithmic derivatives, when invertible, generalize the exp-log correspondence between a Lie algebra and its Lie group. Such correspondences occur naturally in the study of dynamical systems when dealing with the linearization of vector fields and the non linearizability of a resonant vector fields corresponds to the non invertibility of a logarithmic derivative and to the existence of normal forms. These concepts, stemming from the theory of dynamical systems, can be rephrased in the abstract setting of Lie algebra and the same difficulties as in perturbative quantum field theory (pQFT) arise here. Surprisingly, one can adopt the same ideas as in pQFT with fruitful results such as new constructions of normal forms with the help of the Birkhoff decomposition. The analogy goes even further (locality of counter terms, choice of a renormalization scheme) and shall lead to more interactions between dynamical systems and quantum field theory.
Impact of incorporating visual biofeedback in 4D MRI.
To, David T; Kim, Joshua P; Price, Ryan G; Chetty, Indrin J; Glide-Hurst, Carri K
2016-05-08
Precise radiation therapy (RT) for abdominal lesions is complicated by respiratory motion and suboptimal soft tissue contrast in 4D CT. 4D MRI offers improved con-trast although long scan times and irregular breathing patterns can be limiting. To address this, visual biofeedback (VBF) was introduced into 4D MRI. Ten volunteers were consented to an IRB-approved protocol. Prospective respiratory-triggered, T2-weighted, coronal 4D MRIs were acquired on an open 1.0T MR-SIM. VBF was integrated using an MR-compatible interactive breath-hold control system. Subjects visually monitored their breathing patterns to stay within predetermined tolerances. 4D MRIs were acquired with and without VBF for 2- and 8-phase acquisitions. Normalized respiratory waveforms were evaluated for scan time, duty cycle (programmed/acquisition time), breathing period, and breathing regularity (end-inhale coefficient of variation, EI-COV). Three reviewers performed image quality assessment to compare artifacts with and without VBF. Respiration-induced liver motion was calculated via centroid difference analysis of end-exhale (EE) and EI liver contours. Incorporating VBF reduced 2-phase acquisition time (4.7 ± 1.0 and 5.4 ± 1.5 min with and without VBF, respectively) while reducing EI-COV by 43.8% ± 16.6%. For 8-phase acquisitions, VBF reduced acquisition time by 1.9 ± 1.6 min and EI-COVs by 38.8% ± 25.7% despite breathing rate remaining similar (11.1 ± 3.8 breaths/min with vs. 10.5 ± 2.9 without). Using VBF yielded higher duty cycles than unguided free breathing (34.4% ± 5.8% vs. 28.1% ± 6.6%, respectively). Image grading showed that out of 40 paired evaluations, 20 cases had equivalent and 17 had improved image quality scores with VBF, particularly for mid-exhale and EI. Increased liver excursion was observed with VBF, where superior-inferior, anterior-posterior, and left-right EE-EI displacements were 14.1± 5.8, 4.9 ± 2.1, and 1.5 ± 1.0 mm, respectively, with VBF compared to 11.9
Structural dynamics system model reduction
NASA Technical Reports Server (NTRS)
Chen, J. C.; Rose, T. L.; Wada, B. K.
1987-01-01
Loads analysis for structural dynamic systems is usually performed by finite element models. Because of the complexity of the structural system, the model contains large number of degree-of-freedom. The large model is necessary since details of the stress, loads and responses due to mission environments are computed. However, a simplified model is needed for other tasks such as pre-test analysis for modal testing, and control-structural interaction studies. A systematic method of model reduction for modal test analysis is presented. Perhaps it will be of some help in developing a simplified model for the control studies.
Dynamically controlled crystal growth system
NASA Technical Reports Server (NTRS)
Bray, Terry L. (Inventor); Kim, Larry J. (Inventor); Harrington, Michael (Inventor); DeLucas, Lawrence J. (Inventor)
2002-01-01
Crystal growth can be initiated and controlled by dynamically controlled vapor diffusion or temperature change. In one aspect, the present invention uses a precisely controlled vapor diffusion approach to monitor and control protein crystal growth. The system utilizes a humidity sensor and various interfaces under computer control to effect virtually any evaporation rate from a number of different growth solutions simultaneously by means of an evaporative gas flow. A static laser light scattering sensor can be used to detect aggregation events and trigger a change in the evaporation rate for a growth solution. A control/follower configuration can be used to actively monitor one chamber and accurately control replicate chambers relative to the control chamber. In a second aspect, the invention exploits the varying solubility of proteins versus temperature to control the growth of protein crystals. This system contains miniature thermoelectric devices under microcomputer control that change temperature as needed to grow crystals of a given protein. Complex temperature ramps are possible using this approach. A static laser light scattering probe also can be used in this system as a non-invasive probe for detection of aggregation events. The automated dynamic control system provides systematic and predictable responses with regard to crystal size. These systems can be used for microgravity crystallization projects, for example in a space shuttle, and for crystallization work under terrestial conditions. The present invention is particularly useful for macromolecular crystallization, e.g. for proteins, polypeptides, nucleic acids, viruses and virus particles.
ICT4D: A Computer Science Perspective
NASA Astrophysics Data System (ADS)
Sutinen, Erkki; Tedre, Matti
The term ICT4D refers to the opportunities of Information and Communication Technology (ICT) as an agent of development. Research in that field is often focused on evaluating the feasibility of existing technologies, mostly of Western or Far East Asian origin, in the context of developing regions. A computer science perspective is complementary to that agenda. The computer science perspective focuses on exploring the resources, or inputs, of a particular context and on basing the design of a technical intervention on the available resources, so that the output makes a difference in the development context. The modus operandi of computer science, construction, interacts with evaluation and exploration practices. An analysis of a contextualized information technology curriculum of Tumaini University in southern Tanzania shows the potential of the computer science perspective for designing meaningful information and communication technology for a developing region.
Taillandier-Thomas, Thibault; Roux, Stéphane; Hild, François
2016-07-01
Based on the assumption that the time evolution of a sample observed by computed tomography requires many less parameters than the definition of the microstructure itself, it is proposed to reconstruct these changes based on the initial state (using computed tomography) and very few radiographs acquired at fixed intervals of time. This Letter presents a proof of concept that for a fatigue cracked sample its kinematics can be tracked from no more than two radiographs in situations where a complete 3D view would require several hundreds of radiographs. This 2 order of magnitude gain opens the way to a "computed" 4D tomography, which complements the recent progress achieved in fast or ultrafast computed tomography, which is based on beam brightness, detector sensitivity, and signal acquisition technologies.
NASA Astrophysics Data System (ADS)
Taillandier-Thomas, Thibault; Roux, Stéphane; Hild, François
2016-07-01
Based on the assumption that the time evolution of a sample observed by computed tomography requires many less parameters than the definition of the microstructure itself, it is proposed to reconstruct these changes based on the initial state (using computed tomography) and very few radiographs acquired at fixed intervals of time. This Letter presents a proof of concept that for a fatigue cracked sample its kinematics can be tracked from no more than two radiographs in situations where a complete 3D view would require several hundreds of radiographs. This 2 order of magnitude gain opens the way to a "computed" 4D tomography, which complements the recent progress achieved in fast or ultrafast computed tomography, which is based on beam brightness, detector sensitivity, and signal acquisition technologies.
Development of the 4D Phantom for patient-specific, end-to-end radiation therapy QA
NASA Astrophysics Data System (ADS)
Malinowski, K.; Noel, C.; Lu, W.; Lechleiter, K.; Hubenschmidt, J.; Low, D.; Parikh, P.
2007-03-01
In many patients respiratory motion causes motion artifacts in CT images, thereby inhibiting precise treatment planning and lowering the ability to target radiation to tumors. The 4D Phantom, which includes a 3D stage and a 1D stage that each are capable of arbitrary motion and timing, was developed to serve as an end-to-end radiation therapy QA device that could be used throughout CT imaging, radiation therapy treatment planning, and radiation therapy delivery. The dynamic accuracy of the system was measured with a camera system. The positional error was found to be equally likely to occur in the positive and negative directions for each axis, and the stage was within 0.1 mm of the desired position 85% of the time. In an experiment designed to use the 4D Phantom's encoders to measure trial-to-trial precision of the system, the 4D Phantom reproduced the motion during variable bag ventilation of a transponder that had been bronchoscopically implanted in a canine lung. In this case, the encoder readout indicated that the stage was within 10 microns of the sent position 94% of the time and that the RMS error was 7 microns. Motion artifacts were clearly visible in 3D and respiratory-correlated (4D) CT scans of phantoms reproducing tissue motion. In 4D CT scans, apparent volume was found to be directly correlated to instantaneous velocity. The system is capable of reproducing individual patient-specific tissue trajectories with a high degree of accuracy and precision and will be useful for end-to-end radiation therapy QA.
Survivability of Deterministic Dynamical Systems
NASA Astrophysics Data System (ADS)
Hellmann, Frank; Schultz, Paul; Grabow, Carsten; Heitzig, Jobst; Kurths, Jürgen
2016-07-01
The notion of a part of phase space containing desired (or allowed) states of a dynamical system is important in a wide range of complex systems research. It has been called the safe operating space, the viability kernel or the sunny region. In this paper we define the notion of survivability: Given a random initial condition, what is the likelihood that the transient behaviour of a deterministic system does not leave a region of desirable states. We demonstrate the utility of this novel stability measure by considering models from climate science, neuronal networks and power grids. We also show that a semi-analytic lower bound for the survivability of linear systems allows a numerically very efficient survivability analysis in realistic models of power grids. Our numerical and semi-analytic work underlines that the type of stability measured by survivability is not captured by common asymptotic stability measures.
Survivability of Deterministic Dynamical Systems.
Hellmann, Frank; Schultz, Paul; Grabow, Carsten; Heitzig, Jobst; Kurths, Jürgen
2016-01-01
The notion of a part of phase space containing desired (or allowed) states of a dynamical system is important in a wide range of complex systems research. It has been called the safe operating space, the viability kernel or the sunny region. In this paper we define the notion of survivability: Given a random initial condition, what is the likelihood that the transient behaviour of a deterministic system does not leave a region of desirable states. We demonstrate the utility of this novel stability measure by considering models from climate science, neuronal networks and power grids. We also show that a semi-analytic lower bound for the survivability of linear systems allows a numerically very efficient survivability analysis in realistic models of power grids. Our numerical and semi-analytic work underlines that the type of stability measured by survivability is not captured by common asymptotic stability measures. PMID:27405955
Survivability of Deterministic Dynamical Systems
Hellmann, Frank; Schultz, Paul; Grabow, Carsten; Heitzig, Jobst; Kurths, Jürgen
2016-01-01
The notion of a part of phase space containing desired (or allowed) states of a dynamical system is important in a wide range of complex systems research. It has been called the safe operating space, the viability kernel or the sunny region. In this paper we define the notion of survivability: Given a random initial condition, what is the likelihood that the transient behaviour of a deterministic system does not leave a region of desirable states. We demonstrate the utility of this novel stability measure by considering models from climate science, neuronal networks and power grids. We also show that a semi-analytic lower bound for the survivability of linear systems allows a numerically very efficient survivability analysis in realistic models of power grids. Our numerical and semi-analytic work underlines that the type of stability measured by survivability is not captured by common asymptotic stability measures. PMID:27405955
Structural Dynamics of Electronic Systems
NASA Astrophysics Data System (ADS)
Suhir, E.
2013-03-01
The published work on analytical ("mathematical") and computer-aided, primarily finite-element-analysis (FEA) based, predictive modeling of the dynamic response of electronic systems to shocks and vibrations is reviewed. While understanding the physics of and the ability to predict the response of an electronic structure to dynamic loading has been always of significant importance in military, avionic, aeronautic, automotive and maritime electronics, during the last decade this problem has become especially important also in commercial, and, particularly, in portable electronics in connection with accelerated testing of various surface mount technology (SMT) systems on the board level. The emphasis of the review is on the nonlinear shock-excited vibrations of flexible printed circuit boards (PCBs) experiencing shock loading applied to their support contours during drop tests. At the end of the review we provide, as a suitable and useful illustration, the exact solution to a highly nonlinear problem of the dynamic response of a "flexible-and-heavy" PCB to an impact load applied to its support contour during drop testing.
NASA Astrophysics Data System (ADS)
Müller, Thomas
2011-06-01
The new version of the Motion4D-library now also includes the integration of a Sachs basis and the Jacobi equation to determine gravitational lensing of pointlike sources for arbitrary spacetimes.New version program summaryProgram title: Motion4D-libraryCatalogue identifier: AEEX_v3_0Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEEX_v3_0.htmlProgram obtainable from: CPC Program Library, Queen's University, Belfast, N. IrelandLicensing provisions: Standard CPC licence, http://cpc.cs.qub.ac.uk/licence/licence.htmlNo. of lines in distributed program, including test data, etc.: 219 441No. of bytes in distributed program, including test data, etc.: 6 968 223Distribution format: tar.gzProgramming language: C++Computer: All platforms with a C++ compilerOperating system: Linux, WindowsRAM: 61 MbytesClassification: 1.5External routines: Gnu Scientic Library (GSL) (http://www.gnu.org/software/gsl/)Catalogue identifier of previous version: AEEX_v2_0Journal reference of previous version: Comput. Phys. Comm. 181 (2010) 703Does the new version supersede the previous version?: YesNature of problem: Solve geodesic equation, parallel and Fermi-Walker transport in four-dimensional Lorentzian spacetimes. Determine gravitational lensing by integration of Jacobi equation and parallel transport of Sachs basis.Solution method: Integration of ordinary differential equations.Reasons for new version: The main novelty of the current version is the extension to integrate the Jacobi equation and the parallel transport of the Sachs basis along null geodesics. In combination, the change of the cross section of a light bundle and thus the gravitational lensing effect of a spacetime can be determined. Furthermore, we have implemented several new metrics.Summary of revisions: The main novelty of the current version is the integration of the Jacobi equation and the parallel transport of the Sachs basis along null geodesics. The corresponding set of equations readd2xμdλ2=-Γρ
Noise in Nonlinear Dynamical Systems
NASA Astrophysics Data System (ADS)
Moss, Frank; McClintock, P. V. E.
2009-08-01
List of contributors; Preface; Introduction to volume three; 1. The effects of coloured quadratic noise on a turbulent transition in liquid He II J. T. Tough; 2. Electrohydrodynamic instability of nematic liquid crystals: growth process and influence of noise S. Kai; 3. Suppression of electrohydrodynamic instabilities by external noise Helmut R. Brand; 4. Coloured noise in dye laser fluctuations R. Roy, A. W. Yu and S. Zhu; 5. Noisy dynamics in optically bistable systems E. Arimondo, D. Hennequin and P. Glorieux; 6. Use of an electronic model as a guideline in experiments on transient optical bistability W. Lange; 7. Computer experiments in nonlinear stochastic physics Riccardo Mannella; 8. Analogue simulations of stochastic processes by means of minimum component electronic devices Leone Fronzoni; 9. Analogue techniques for the study of problems in stochastic nonlinear dynamics P. V. E. McClintock and Frank Moss; Index.
NASA Astrophysics Data System (ADS)
Kotasidis, F. A.; Matthews, J. C.; Reader, A. J.; Angelis, G. I.; Zaidi, H.
2014-10-01
Parametric imaging in thoracic and abdominal PET can provide additional parameters more relevant to the pathophysiology of the system under study. However, dynamic data in the body are noisy due to the limiting counting statistics leading to suboptimal kinetic parameter estimates. Direct 4D image reconstruction algorithms can potentially improve kinetic parameter precision and accuracy in dynamic PET body imaging. However, construction of a common kinetic model is not always feasible and in contrast to post-reconstruction kinetic analysis, errors in poorly modelled regions may spatially propagate to regions which are well modelled. To reduce error propagation from erroneous model fits, we implement and evaluate a new approach to direct parameter estimation by incorporating a recently proposed kinetic modelling strategy within a direct 4D image reconstruction framework. The algorithm uses a secondary more general model to allow a less constrained model fit in regions where the kinetic model does not accurately describe the underlying kinetics. A portion of the residuals then is adaptively included back into the image whilst preserving the primary model characteristics in other well modelled regions using a penalty term that trades off the models. Using fully 4D simulations based on dynamic [15O]H2O datasets, we demonstrate reduction in propagation-related bias for all kinetic parameters. Under noisy conditions, reductions in bias due to propagation are obtained at the cost of increased noise, which in turn results in increased bias and variance of the kinetic parameters. This trade-off reflects the challenge of separating the residuals arising from poor kinetic modelling fits from the residuals arising purely from noise. Nonetheless, the overall root mean square error is reduced in most regions and parameters. Using the adaptive 4D image reconstruction improved model fits can be obtained in poorly modelled regions, leading to reduced errors potentially propagating
Opening the Black Box of ICT4D: Advancing Our Understanding of ICT4D Partnerships
ERIC Educational Resources Information Center
Park, Sung Jin
2013-01-01
The term, Information and Communication Technologies for Development (ICT4D), pertains to programs or projects that strategically use ICTs (e.g. mobile phones, computers, and the internet) as a means toward the socio-economic betterment for the poor in developing contexts. Gaining the political and financial support of the international community…
Dynamical habitability of planetary systems.
Dvorak, Rudolf; Pilat-Lohinger, Elke; Bois, Eric; Schwarz, Richard; Funk, Barbara; Beichman, Charles; Danchi, William; Eiroa, Carlos; Fridlund, Malcolm; Henning, Thomas; Herbst, Tom; Kaltenegger, Lisa; Lammer, Helmut; Léger, Alain; Liseau, René; Lunine, Jonathan; Paresce, Francesco; Penny, Alan; Quirrenbach, Andreas; Röttgering, Huub; Selsis, Frank; Schneider, Jean; Stam, Daphne; Tinetti, Giovanna; White, Glenn J
2010-01-01
The problem of the stability of planetary systems, a question that concerns only multiplanetary systems that host at least two planets, is discussed. The problem of mean motion resonances is addressed prior to discussion of the dynamical structure of the more than 350 known planets. The difference with regard to our own Solar System with eight planets on low eccentricity is evident in that 60% of the known extrasolar planets have orbits with eccentricity e > 0.2. We theoretically highlight the studies concerning possible terrestrial planets in systems with a Jupiter-like planet. We emphasize that an orbit of a particular nature only will keep a planet within the habitable zone around a host star with respect to the semimajor axis and its eccentricity. In addition, some results are given for individual systems (e.g., Gl777A) with regard to the stability of orbits within habitable zones. We also review what is known about the orbits of planets in double-star systems around only one component (e.g., gamma Cephei) and around both stars (e.g., eclipsing binaries).
Dynamical habitability of planetary systems.
Dvorak, Rudolf; Pilat-Lohinger, Elke; Bois, Eric; Schwarz, Richard; Funk, Barbara; Beichman, Charles; Danchi, William; Eiroa, Carlos; Fridlund, Malcolm; Henning, Thomas; Herbst, Tom; Kaltenegger, Lisa; Lammer, Helmut; Léger, Alain; Liseau, René; Lunine, Jonathan; Paresce, Francesco; Penny, Alan; Quirrenbach, Andreas; Röttgering, Huub; Selsis, Frank; Schneider, Jean; Stam, Daphne; Tinetti, Giovanna; White, Glenn J
2010-01-01
The problem of the stability of planetary systems, a question that concerns only multiplanetary systems that host at least two planets, is discussed. The problem of mean motion resonances is addressed prior to discussion of the dynamical structure of the more than 350 known planets. The difference with regard to our own Solar System with eight planets on low eccentricity is evident in that 60% of the known extrasolar planets have orbits with eccentricity e > 0.2. We theoretically highlight the studies concerning possible terrestrial planets in systems with a Jupiter-like planet. We emphasize that an orbit of a particular nature only will keep a planet within the habitable zone around a host star with respect to the semimajor axis and its eccentricity. In addition, some results are given for individual systems (e.g., Gl777A) with regard to the stability of orbits within habitable zones. We also review what is known about the orbits of planets in double-star systems around only one component (e.g., gamma Cephei) and around both stars (e.g., eclipsing binaries). PMID:20307181
Dynamics of complex multibody systems
NASA Astrophysics Data System (ADS)
Schiehlen, W. O.
The analysis of multibody-system (MBS) dynamics is discussed and demonstrated in a review of recent work. The early history of MBS studies is traced; the kinematic equations are derived for free, holonomic, and nonholonomic systems in both inertial and moving reference frames; the Newton-Euler equations are obtained by replacing the rigid bearings and supports by constraint forces and torques; equations of motion are found by means of D'Alembert's and Jourdain's principles; and generalized constraint forces and bearing and support clearances are considered. The computer derivation of equations of motion is demonstrated on a four-body moving-vehicle problem. The approach described is shown to use less computation time and memory space than techniques based on the Lagrange or Gibbs-Appell equations, while permitting the inclusion of contact and friction forces.
Functional organization of the human 4D Nucleome
Chen, Haiming; Chen, Jie; Muir, Lindsey A.; Ronquist, Scott; Meixner, Walter; Ljungman, Mats; Ried, Thomas; Smale, Stephen; Rajapakse, Indika
2015-01-01
The 4D organization of the interphase nucleus, or the 4D Nucleome (4DN), reflects a dynamical interaction between 3D genome structure and function and its relationship to phenotype. We present initial analyses of the human 4DN, capturing genome-wide structure using chromosome conformation capture and 3D imaging, and function using RNA-sequencing. We introduce a quantitative index that measures underlying topological stability of a genomic region. Our results show that structural features of genomic regions correlate with function with surprising persistence over time. Furthermore, constructing genome-wide gene-level contact maps aided in identifying gene pairs with high potential for coregulation and colocalization in a manner consistent with expression via transcription factories. We additionally use 2D phase planes to visualize patterns in 4DN data. Finally, we evaluated gene pairs within a circadian gene module using 3D imaging, and found periodicity in the movement of clock circadian regulator and period circadian clock 2 relative to each other that followed a circadian rhythm and entrained with their expression. PMID:26080430
Stability in dynamical systems I
Courant, E.D.; Ruth, R.D.; Weng, W.T.
1984-08-01
We have reviewed some of the basic techniques which can be used to analyze stability in nonlinear dynamical systems, particularly in circular particle accelerators. We have concentrated on one-dimensional systems in the examples in order to simply illustrate the general techniques. We began with a review of Hamiltonian dynamics and canonical transformations. We then reviewed linear equations with periodic coefficients using the basic techniques from accelerator theory. To handle nonlinear terms we developed a canonical perturbation theory. From this we calculated invariants and the amplitude dependence of the frequency. This led us to resonances. We studied the cubic resonance in detail by using a rotating coordinate system in phase space. We then considered a general isolated nonlinear resonance. In this case we calculated the width of the resonance and estimated the spacing of resonances in order to use the Chirikov criterion to restrict the validity of the analysis. Finally the resonance equation was reduced to the pendulum equation, and we examined the motion on a separatrix. This brought us to the beginnings of stochastic behavior in the neighborhood of the separatrix. It is this complex behavior in the neighborhood of the separatrix which causes the perturbation theory used here to diverge in many cases. In spite of this the methods developed here have been and are used quite successfully to study nonlinear effects in nearly integrable systems. When used with caution and in conjunction with numerical work they give tremendous insight into the nature of the phase space structure and the stability of nonlinear differential equations. 14 references.
Spatial Operator Algebra for multibody system dynamics
NASA Technical Reports Server (NTRS)
Rodriguez, G.; Jain, A.; Kreutz-Delgado, K.
1992-01-01
The Spatial Operator Algebra framework for the dynamics of general multibody systems is described. The use of a spatial operator-based methodology permits the formulation of the dynamical equations of motion of multibody systems in a concise and systematic way. The dynamical equations of progressively more complex grid multibody systems are developed in an evolutionary manner beginning with a serial chain system, followed by a tree topology system and finally, systems with arbitrary closed loops. Operator factorizations and identities are used to develop novel recursive algorithms for the forward dynamics of systems with closed loops. Extensions required to deal with flexible elements are also discussed.
Interactive 4D Visualization of Sediment Transport Models
NASA Astrophysics Data System (ADS)
Butkiewicz, T.; Englert, C. M.
2013-12-01
Coastal sediment transport models simulate the effects that waves, currents, and tides have on near-shore bathymetry and features such as beaches and barrier islands. Understanding these dynamic processes is integral to the study of coastline stability, beach erosion, and environmental contamination. Furthermore, analyzing the results of these simulations is a critical task in the design, placement, and engineering of coastal structures such as seawalls, jetties, support pilings for wind turbines, etc. Despite the importance of these models, there is a lack of available visualization software that allows users to explore and perform analysis on these datasets in an intuitive and effective manner. Existing visualization interfaces for these datasets often present only one variable at a time, using two dimensional plan or cross-sectional views. These visual restrictions limit the ability to observe the contents in the proper overall context, both in spatial and multi-dimensional terms. To improve upon these limitations, we use 3D rendering and particle system based illustration techniques to show water column/flow data across all depths simultaneously. We can also encode multiple variables across different perceptual channels (color, texture, motion, etc.) to enrich surfaces with multi-dimensional information. Interactive tools are provided, which can be used to explore the dataset and find regions-of-interest for further investigation. Our visualization package provides an intuitive 4D (3D, time-varying) visualization of sediment transport model output. In addition, we are also integrating real world observations with the simulated data to support analysis of the impact from major sediment transport events. In particular, we have been focusing on the effects of Superstorm Sandy on the Redbird Artificial Reef Site, offshore of Delaware Bay. Based on our pre- and post-storm high-resolution sonar surveys, there has significant scour and bedform migration around the
Localization of 4D gravity on pure geometrical thick branes
Barbosa-Cendejas, Nandinii; Herrera-Aguilar, Alfredo
2006-04-15
We consider the generation of thick brane configurations in a pure geometric Weyl integrable 5D spacetime which constitutes a non-Riemannian generalization of Kaluza-Klein (KK) theory. In this framework, we show how 4D gravity can be localized on a scalar thick brane which does not necessarily respect reflection symmetry, generalizing in this way several previous models based on the Randall-Sundrum (RS) system and avoiding both, the restriction to orbifold geometries and the introduction of the branes in the action by hand. We first obtain a thick brane solution that preserves 4D Poincare invariance and breaks Z{sub 2}-symmetry along the extra dimension which, indeed, can be either compact or extended, and supplements brane solutions previously found by other authors. In the noncompact case, this field configuration represents a thick brane with positive energy density centered at y=c{sub 2}, whereas pairs of thick branes arise in the compact case. Remarkably, the Weylian scalar curvature is nonsingular along the fifth dimension in the noncompact case, in contraposition to the RS thin brane system. We also recast the wave equations of the transverse traceless modes of the linear fluctuations of the classical background into a Schroedinger's equation form with a volcano potential of finite bottom in both the compact and the extended cases. We solve Schroedinger equation for the massless zero mode m{sup 2}=0 and obtain a single bound wave function which represents a stable 4D graviton. We also get a continuum gapless spectrum of KK states with m{sup 2}>0 that are suppressed at y=c{sub 2} and turn asymptotically into plane waves.
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76 FR 55814 - 2,4-D; Pesticide Tolerances
Federal Register 2010, 2011, 2012, 2013, 2014
2011-09-09
... AGENCY 40 CFR Part 180 2,4-D; Pesticide Tolerances AGENCY: Environmental Protection Agency (EPA). ACTION: Final rule. SUMMARY: This regulation establishes tolerances for residues of 2,4-D in or on teff, bran... 180.142 be amended by establishing a tolerance for residues of the herbicide 2,4-D...
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Dynamical Localization in Molecular Systems.
NASA Astrophysics Data System (ADS)
Wang, Xidi
In the first four chapters of this thesis we concentrate on the Davydov model which describes the vibrational energy quanta of Amide I bonds (C=O bonds on the alpha -helix) coupled to the acoustic phonon modes of the alpha-helix backbone in the form of a Frohlich Hamiltonian. Following a brief introduction in chapter one, in chapter two we formulate the dynamics of vibrational quanta at finite temperature by using coherent state products. The fluctuation-dissipation relation is derived. At zero temperature, in the continuum limit, we recover the original results of Davydov. We also achieve good agreement with numerical simulations. In chapter three, the net contraction of the lattice is calculated exactly at any temperature, and its relation to the so -call "topological stability" of the Davydov soliton is discussed. In the second section of the chapter three we calculate the overtone spectra of crystalline acetanilide (according to some opinions ACN provides experimental evidence for the existence of Davydov solitons). Good agreement with experimental data has been obtained. In chapter four we study the self-trapped vibrational excitations by the Quantum Monte Carlo technique. For a single excitation, the temperature dependence of different physical observables is calculated. The quasi-particle which resembles the Davydov soliton has been found to be fairly narrow using the most commonly used data for the alpha -helix; at temperatures above a few Kelvin, the quasi-particle reaches its smallest limit (extends over three sites), which implies diffusive motion of the small polaron-like quasi-particle at high temperatures. For the multi-excitation case, bound pairs and clusters of excitations are found at low temperatures; they gradually dissociate when the temperature of the system is increased as calculated from the density-density correlation function. In the last chapter of this thesis, we study a more general model of dynamical local modes in molecular systems
The GBT Dynamic Scheduling System
NASA Astrophysics Data System (ADS)
McCarty, M. T.; Balser, D. S.; Braatz, J.; Clark, M. H.; Condon, J.; Creager, R. E.; Maddalena, R. J.; Marganian, P.; O'Neil, K.; Sessoms, E.; Shelton, A. L.
2012-09-01
The Robert C. Byrd Green Bank Telescope (GBT) Dynamic Scheduling System (DSS), in use since September, 2009, was designed to maximize observing efficiency while preserving telescope flexibility and data quality without creating undue adversity for the observers. Using observing criteria; observer availability and qualifications for remote observing; three-dimensional weather forecasts; and telescope state, the DSS software optimally schedules observers 24 to 48 hours in advance for a telescope that has a wide-range of capabilities and a geographical location with variable weather patterns. The DSS project was closed October 28, 2011 and will now enter a continuing maintenance and enhancement phase. Recent improvements include a new resource calendar for incorporating telescope maintenance activities, a sensitivity calculator that leverages the scheduling algorithms to facilitate consistent tools for proposal preparation, improved support for monitoring observations, scheduling of high frequency continuum and spectral line observations for both sparse and fully sampled array receivers, and additional session parameters for observations having special requirements.
Yue, Yong Yang, Wensha; McKenzie, Elizabeth; Tuli, Richard; Wallace, Robert; Fraass, Benedick; Fan, Zhaoyang; Pang, Jianing; Deng, Zixin; Li, Debiao
2015-10-15
Purpose: MRI is increasingly being used for radiotherapy planning, simulation, and in-treatment-room motion monitoring. To provide more detailed temporal and spatial MR data for these tasks, we have recently developed a novel self-gated (SG) MRI technique with advantage of k-space phase sorting, high isotropic spatial resolution, and high temporal resolution. The current work describes the validation of this 4D-MRI technique using a MRI- and CT-compatible respiratory motion phantom and comparison to 4D-CT. Methods: The 4D-MRI sequence is based on a spoiled gradient echo-based 3D projection reconstruction sequence with self-gating for 4D-MRI at 3 T. Respiratory phase is resolved by using SG k-space lines as the motion surrogate. 4D-MRI images are reconstructed into ten temporal bins with spatial resolution 1.56 × 1.56 × 1.56 mm{sup 3}. A MRI-CT compatible phantom was designed to validate the performance of the 4D-MRI sequence and 4D-CT imaging. A spherical target (diameter 23 mm, volume 6.37 ml) filled with high-concentration gadolinium (Gd) gel is embedded into a plastic box (35 × 40 × 63 mm{sup 3}) and stabilized with low-concentration Gd gel. The phantom, driven by an air pump, is able to produce human-type breathing patterns between 4 and 30 respiratory cycles/min. 4D-CT of the phantom has been acquired in cine mode, and reconstructed into ten phases with slice thickness 1.25 mm. The 4D images sets were imported into a treatment planning software for target contouring. The geometrical accuracy of the 4D MRI and CT images has been quantified using target volume, flattening, and eccentricity. The target motion was measured by tracking the centroids of the spheres in each individual phase. Motion ground-truth was obtained from input signals and real-time video recordings. Results: The dynamic phantom has been operated in four respiratory rate (RR) settings, 6, 10, 15, and 20/min, and was scanned with 4D-MRI and 4D-CT. 4D-CT images have target
Biofluid Dynamics in Cardiovascular System
NASA Astrophysics Data System (ADS)
Chung, Hansol; Yoo, Su Jung; Kyung, Richard
2011-11-01
Biofluid dynamics is characterized by the study of fluids in biological systems. Common biofluid systems include blood flow in the cardiovascular system and airflow in the lungs. The mathematical modeling of blood flow through the complex geometry of a prosthetic heart valve is a difficult task. In such a problem the complex geometries of the valve must be modeled properly so that they can be studied numerically. The present analysis is performed on a disk-type prosthetic heart valve. The valve is assumed to be in the aortic position and observed the structure of the valve cage influence the flow field near an aortic valve. For the purpose of mathematical modeling, the laminar incompressible two-dimensional steady flow of a homogeneous Newtonian fluid with constant viscosity is assumed. The flow is considered during the greater part of systole when the valve is fully open. Convergent numerical solutions are obtained for Reynolds numbers of 30, 180, 900 and 4500. Stream function, horizontal velocity, vertical velocity and shear stress solutions are computed at every grid point.
Actively triggered 4d cone-beam CT acquisition
Fast, Martin F.; Wisotzky, Eric; Oelfke, Uwe; Nill, Simeon
2013-09-15
Purpose: 4d cone-beam computed tomography (CBCT) scans are usually reconstructed by extracting the motion information from the 2d projections or an external surrogate signal, and binning the individual projections into multiple respiratory phases. In this “after-the-fact” binning approach, however, projections are unevenly distributed over respiratory phases resulting in inefficient utilization of imaging dose. To avoid excess dose in certain respiratory phases, and poor image quality due to a lack of projections in others, the authors have developed a novel 4d CBCT acquisition framework which actively triggers 2d projections based on the forward-predicted position of the tumor.Methods: The forward-prediction of the tumor position was independently established using either (i) an electromagnetic (EM) tracking system based on implanted EM-transponders which act as a surrogate for the tumor position, or (ii) an external motion sensor measuring the chest-wall displacement and correlating this external motion to the phase-shifted diaphragm motion derived from the acquired images. In order to avoid EM-induced artifacts in the imaging detector, the authors devised a simple but effective “Faraday” shielding cage. The authors demonstrated the feasibility of their acquisition strategy by scanning an anthropomorphic lung phantom moving on 1d or 2d sinusoidal trajectories.Results: With both tumor position devices, the authors were able to acquire 4d CBCTs free of motion blurring. For scans based on the EM tracking system, reconstruction artifacts stemming from the presence of the EM-array and the EM-transponders were greatly reduced using newly developed correction algorithms. By tuning the imaging frequency independently for each respiratory phase prior to acquisition, it was possible to harmonize the number of projections over respiratory phases. Depending on the breathing period (3.5 or 5 s) and the gantry rotation time (4 or 5 min), between ∼90 and 145
Dynamical Signatures of Living Systems
NASA Technical Reports Server (NTRS)
Zak, M.
1999-01-01
One of the main challenges in modeling living systems is to distinguish a random walk of physical origin (for instance, Brownian motions) from those of biological origin and that will constitute the starting point of the proposed approach. As conjectured, the biological random walk must be nonlinear. Indeed, any stochastic Markov process can be described by linear Fokker-Planck equation (or its discretized version), only that type of process has been observed in the inanimate world. However, all such processes always converge to a stable (ergodic or periodic) state, i.e., to the states of a lower complexity and high entropy. At the same time, the evolution of living systems directed toward a higher level of complexity if complexity is associated with a number of structural variations. The simplest way to mimic such a tendency is to incorporate a nonlinearity into the random walk; then the probability evolution will attain the features of diffusion equation: the formation and dissipation of shock waves initiated by small shallow wave disturbances. As a result, the evolution never "dies:" it produces new different configurations which are accompanied by an increase or decrease of entropy (the decrease takes place during formation of shock waves, the increase-during their dissipation). In other words, the evolution can be directed "against the second law of thermodynamics" by forming patterns outside of equilibrium in the probability space. Due to that, a specie is not locked up in a certain pattern of behavior: it still can perform a variety of motions, and only the statistics of these motions is constrained by this pattern. It should be emphasized that such a "twist" is based upon the concept of reflection, i.e., the existence of the self-image (adopted from psychology). The model consists of a generator of stochastic processes which represents the motor dynamics in the form of nonlinear random walks, and a simulator of the nonlinear version of the diffusion
Complete valvular heart apparatus model from 4D cardiac CT.
Grbic, Sasa; Ionasec, Razvan; Vitanovski, Dime; Voigt, Ingmar; Wang, Yang; Georgescu, Bogdan; Navab, Nassir; Comaniciu, Dorin
2012-07-01
The cardiac valvular apparatus, composed of the aortic, mitral, pulmonary and tricuspid valves, is an essential part of the anatomical, functional and hemodynamic characteristics of the heart and the cardiovascular system as a whole. Valvular heart diseases often involve multiple dysfunctions and require joint assessment and therapy of the valves. In this paper, we propose a complete and modular patient-specific model of the cardiac valvular apparatus estimated from 4D cardiac CT data. A new constrained Multi-linear Shape Model (cMSM), conditioned by anatomical measurements, is introduced to represent the complex spatio-temporal variation of the heart valves. The cMSM is exploited within a learning-based framework to efficiently estimate the patient-specific valve parameters from cine images. Experiments on 64 4D cardiac CT studies demonstrate the performance and clinical potential of the proposed method. Our method enables automatic quantitative evaluation of the complete valvular apparatus based on non-invasive imaging techniques. In conjunction with existent patient-specific chamber models, the presented valvular model enables personalized computation modeling and realistic simulation of the entire cardiac system.
4D micro-CT using fast prospective gating
NASA Astrophysics Data System (ADS)
Guo, Xiaolian; Johnston, Samuel M.; Qi, Yi; Johnson, G. Allan; Badea, Cristian T.
2012-01-01
Micro-CT is currently used in preclinical studies to provide anatomical information. But, there is also significant interest in using this technology to obtain functional information. We report here a new sampling strategy for 4D micro-CT for functional cardiac and pulmonary imaging. Rapid scanning of free-breathing mice is achieved with fast prospective gating (FPG) implemented on a field programmable gate array. The method entails on-the-fly computation of delays from the R peaks of the ECG signals or the peaks of the respiratory signals for the triggering pulses. Projection images are acquired for all cardiac or respiratory phases at each angle before rotating to the next angle. FPG can deliver the faster scan time of retrospective gating (RG) with the regular angular distribution of conventional prospective gating for cardiac or respiratory gating. Simultaneous cardio-respiratory gating is also possible with FPG in a hybrid retrospective/prospective approach. We have performed phantom experiments to validate the new sampling protocol and compared the results from FPG and RG in cardiac imaging of a mouse. Additionally, we have evaluated the utility of incorporating respiratory information in 4D cardiac micro-CT studies with FPG. A dual-source micro-CT system was used for image acquisition with pulsed x-ray exposures (80 kVp, 100 mA, 10 ms). The cardiac micro-CT protocol involves the use of a liposomal blood pool contrast agent containing 123 mg I ml-1 delivered via a tail vein catheter in a dose of 0.01 ml g-1 body weight. The phantom experiment demonstrates that FPG can distinguish the successive phases of phantom motion with minimal motion blur, and the animal study demonstrates that respiratory FPG can distinguish inspiration and expiration. 4D cardiac micro-CT imaging with FPG provides image quality superior to RG at an isotropic voxel size of 88 µm and 10 ms temporal resolution. The acquisition time for either sampling approach is less than 5 min. The
Stability of Dynamical Systems with Discontinuous Motions:
NASA Astrophysics Data System (ADS)
Michel, Anthony N.; Hou, Ling
In this paper we present a stability theory for discontinuous dynamical systems (DDS): continuous-time systems whose motions are not necessarily continuous with respect to time. We show that this theory is not only applicable in the analysis of DDS, but also in the analysis of continuous dynamical systems (continuous-time systems whose motions are continuous with respect to time), discrete-time dynamical systems (systems whose motions are defined at discrete points in time) and hybrid dynamical systems (HDS) (systems whose descriptions involve simultaneously continuous-time and discrete-time). We show that the stability results for DDS are in general less conservative than the corresponding well-known classical Lyapunov results for continuous dynamical systems and discrete-time dynamical systems. Although the DDS stability results are applicable to general dynamical systems defined on metric spaces (divorced from any kind of description by differential equations, or any other kinds of equations), we confine ourselves to finite-dimensional dynamical systems defined by ordinary differential equations and difference equations, to make this paper as widely accessible as possible. We present only sample results, namely, results for uniform asymptotic stability in the large.
Geometric Mathematical Framework for Multibody System Dynamics
NASA Astrophysics Data System (ADS)
Terze, Zdravko; Vrdoljak, Milan; Zlatar, Dario
2010-09-01
The paper surveys geometric mathematical framework for computational modeling of multibody system dynamics. Starting with the configuration space of rigid body motion and analysis of it's Lie group structure, the elements of respective Lie algebra are addressed and basic relations pertinent to geometrical formulations of multibody system dynamics are surveyed. Dynamical model of multibody system on manifold introduced, along with the outline of geometric characteristics of holonomic and non-holonomic kinematical constraints.
Probing Invisible, Excited Protein States by Non-Uniformly Sampled Pseudo-4D CEST Spectroscopy.
Long, Dong; Delaglio, Frank; Sekhar, Ashok; Kay, Lewis E
2015-09-01
Chemical exchange saturation transfer (CEST) NMR spectroscopy is a powerful tool for studies of slow timescale protein dynamics. Typical experiments are based on recording a large number of 2D data sets and quantifying peak intensities in each of the resulting planes. A weakness of the method is that peaks must be resolved in 2D spectra, limiting applications to relatively small proteins. Resolution is significantly improved in 3D spectra but recording uniformly sampled data is time-prohibitive. Here we describe non-uniformly sampled HNCO-based pseudo-4D CEST that provides excellent resolution in reasonable measurement times. Data analysis is done through fitting in the time domain, without the need of reconstructing the frequency dimensions, exploiting previously measured accurate peak positions in reference spectra. The methodology is demonstrated on several protein systems, including a nascent form of superoxide dismutase that is implicated in neurodegenerative disease. PMID:26178142
Uncertain destination dynamics of delay coupled systems
NASA Astrophysics Data System (ADS)
Pal, Santinath; Poria, Swarup
2015-03-01
Certain dynamical systems exhibit sensitivity to initial conditions in which the asymptotic state is selected from multiple possible states. The associated uncertain destination dynamics can be analyzed by an appropriate reduction of the full system to a subsystem that explicitly yields the dynamics [1]. These types of systems are known as multistable systems. In this paper, a scheme for designing delay coupled multistable systems is proposed. The scheme considers delay coupled Lorenz-Stenflo systems. The scheme is based on Lyapunov's stability theorem. Numerical simulation results are presented to show the effectiveness of the proposed scheme.
Dynamical systems theory and applications
NASA Astrophysics Data System (ADS)
Awrejcewicz, Jan
2006-08-01
The 7th International Conference devoted to "Dynamical Systems-Theory and Applications" hold in 8-11 December, 2003 in Łódź, Poland, and it was organized by the staff of Department of Automatics and Biomechanics of the Technical University of Łódź. It was financially supported by the Rector of the Technical University of Łódź and the Department of Education and Physical Culture of the Łódź City Hall. The members of the International Scientific Committee included: Igor V. Andrianov (Dniepropetrovsk), Jan Awrejcewicz (Łódź), Iliya Blekhman (Sankt Petersburg), Roman Bogacz (Warszawa), Dick van Campen (Eindhoven), Zbigniew Engel (Kraków), Lothar Gaul (Stuttgart), Józef Giergiel (Kraków), Michał Kleiber (Warszawa), Vadim A. Krysko (Saratov), Włodzimierz Kurnik (Warszawa), Claude-Henri Lamarque (Lyon), Leonid I. Manevitch (Moscow), Jan Osiecki (Warszawa), Wiesaw Ostachowicz (Gdańsk), Ladislav Pust (Prague), Giuseppe Rega (Rome), Tsuneo Someya (Tokyo), Zbigniew Starczewski (Warszawa), Eugeniusz Świtoński (Gliwice), Andrzej Tylikowski (Warszawa), Tadeusz Uhl (Kraków), Aleksander F. Vakakis (Illinois), Józef Wojnarowski (Gliwice).
Single timepoint models of dynamic systems.
Sachs, K; Itani, S; Fitzgerald, J; Schoeberl, B; Nolan, G P; Tomlin, C J
2013-08-01
Many interesting studies aimed at elucidating the connectivity structure of biomolecular pathways make use of abundance measurements, and employ statistical and information theoretic approaches to assess connectivities. These studies often do not address the effects of the dynamics of the underlying biological system, yet dynamics give rise to impactful issues such as timepoint selection and its effect on structure recovery. In this work, we study conditions for reliable retrieval of the connectivity structure of a dynamic system, and the impact of dynamics on structure-learning efforts. We encounter an unexpected problem not previously described in elucidating connectivity structure from dynamic systems, show how this confounds structure learning of the system and discuss possible approaches to overcome the confounding effect. Finally, we test our hypotheses on an accurate dynamic model of the IGF signalling pathway. We use two structure-learning methods at four time points to contrast the performance and robustness of those methods in terms of recovering correct connectivity. PMID:24511382
Killing Weeds with 2,4-D. Extension Bulletin 389.
ERIC Educational Resources Information Center
Lee, Oliver C.
Discussed is the use of the herbicide 2,4-D. Though written for farmers and agricultural workers, the pamphlet considers turf weed control and use of 2,4-D near ornamental plants. Aspects of the use of this herbicide covered are: (1) the common forms of 2,4-D; (2) plant responses and tolerances to the herbicide; (3) dilution and concentration of…
Generation and preclinical characterization of an antibody specific for SEMA4D
Fisher, Terrence L.; Reilly, Christine A.; Winter, Laurie A.; Pandina, Tracy; Jonason, Alan; Scrivens, Maria; Balch, Leslie; Bussler, Holm; Torno, Sebold; Seils, Jennifer; Mueller, Loretta; Huang, He; Klimatcheva, Ekaterina; Howell, Alan; Kirk, Renee; Evans, Elizabeth; Paris, Mark; Leonard, John E.; Smith, Ernest S.; Zauderer, Maurice
2016-01-01
Semaphorin 4D (SEMA4D or CD100) is a member of the semaphorin family of proteins and an important mediator of the movement and differentiation of multiple cell types, including those of the immune, vascular, and nervous systems. Blocking the binding of SEMA4D to its receptors can result in physiologic changes that may have implications in cancer, autoimmune, and neurological disease. To study the effects of blocking SEMA4D, we generated, in SEMA4D-deficient mice, a panel of SEMA4D-specific hybridomas that react with murine, primate, and human SEMA4D. Utilizing the complementarity-determining regions from one of these hybridomas (mAb 67-2), we generated VX15/2503, a humanized IgG4 monoclonal antibody that is currently in clinical development for the potential treatment of various malignancies and neurodegenerative disorders, including multiple sclerosis and Huntington's disease. This work describes the generation and characterization of VX15/2503, including in vitro functional testing, epitope mapping, and an in vivo demonstration of efficacy in an animal model of rheumatoid arthritis. PMID:26431358
Dynamic sensitivity analysis of biological systems
Wu, Wu Hsiung; Wang, Feng Sheng; Chang, Maw Shang
2008-01-01
Background A mathematical model to understand, predict, control, or even design a real biological system is a central theme in systems biology. A dynamic biological system is always modeled as a nonlinear ordinary differential equation (ODE) system. How to simulate the dynamic behavior and dynamic parameter sensitivities of systems described by ODEs efficiently and accurately is a critical job. In many practical applications, e.g., the fed-batch fermentation systems, the system admissible input (corresponding to independent variables of the system) can be time-dependent. The main difficulty for investigating the dynamic log gains of these systems is the infinite dimension due to the time-dependent input. The classical dynamic sensitivity analysis does not take into account this case for the dynamic log gains. Results We present an algorithm with an adaptive step size control that can be used for computing the solution and dynamic sensitivities of an autonomous ODE system simultaneously. Although our algorithm is one of the decouple direct methods in computing dynamic sensitivities of an ODE system, the step size determined by model equations can be used on the computations of the time profile and dynamic sensitivities with moderate accuracy even when sensitivity equations are more stiff than model equations. To show this algorithm can perform the dynamic sensitivity analysis on very stiff ODE systems with moderate accuracy, it is implemented and applied to two sets of chemical reactions: pyrolysis of ethane and oxidation of formaldehyde. The accuracy of this algorithm is demonstrated by comparing the dynamic parameter sensitivities obtained from this new algorithm and from the direct method with Rosenbrock stiff integrator based on the indirect method. The same dynamic sensitivity analysis was performed on an ethanol fed-batch fermentation system with a time-varying feed rate to evaluate the applicability of the algorithm to realistic models with time
New directions in algebraic dynamical systems
NASA Astrophysics Data System (ADS)
Schmidt, Klaus; Verbitskiy, Evgeny
2011-02-01
The logarithmic Mahler measure of certain multivariate polynomials occurs frequently as the entropy or the free energy of solvable lattice models (especially dimer models). It is also known that the entropy of an algebraic dynamical system is the logarithmic Mahler measure of the defining polynomial. The connection between the lattice models and the algebraic dynamical systems is still rather mysterious.
Semicontinuity of attractors for impulsive dynamical systems
NASA Astrophysics Data System (ADS)
Bonotto, E. M.; Bortolan, M. C.; Collegari, R.; Czaja, R.
2016-10-01
In this paper we introduce the concept of collective tube conditions which assures a suitable behaviour for a family of dynamical systems close to impulsive sets. Using the collective tube conditions, we develop the theory of upper and lower semicontinuity of global attractors for a family of impulsive dynamical systems.
Systems-Dynamic Analysis for Neighborhood Study
Systems-dynamic analysis (or system dynamics (SD)) helps planners identify interrelated impacts of transportation and land-use policies on neighborhood-scale economic outcomes for households and businesses, among other applications. This form of analysis can show benefits and tr...
Nonlinear Dynamics of Parametrically Excited Gyroscopic Systems
Namachchivaya. N.S.
2001-06-01
The primary objective of this project is to determine how some of the powerful geometric methods of dynamical systems can be applied to study nonlinear gyroscopic systems. We proposed to develop techniques to predict local and global behavior and instability mechanisms and to analyze the interactions between noise, stability, and nonlinearities inherent in gyroscopic systems. In order to obtain these results we use the method of normal forms, global bifurcation techniques, and various other dynamical systems tools.
4D GPR Experiments--Towards the Virtual Lysimeter
NASA Astrophysics Data System (ADS)
Grasmueck, M.; Viggiano, D. A.; Day-Lewis, F. D.; Drasdis, J. B.; Kruse, S. E.; Or, D.
2006-05-01
data shows the shape and size of the imaged wet-bulb closely match the modeling and excavation results. Wetting front propagation was on the order of 0.2-0.5 m/hr. GPR detected retained water 17 hr after completion of the infiltration. In addition to pattern detection, attempts for establishing mass balance are underway. In summary, preliminary results from controlled field experiments show the 4D GPR method has the precision, resolution, and repeatability required for non-invasive detection of water-flow patterns and dynamics in the vadose zone, hence could potentially serve as a virtual lysimeter.
Improving homogeneity by dynamic speed limit systems.
van Nes, Nicole; Brandenburg, Stefan; Twisk, Divera
2010-05-01
Homogeneity of driving speeds is an important variable in determining road safety; more homogeneous driving speeds increase road safety. This study investigates the effect of introducing dynamic speed limit systems on homogeneity of driving speeds. A total of 46 subjects twice drove a route along 12 road sections in a driving simulator. The speed limit system (static-dynamic), the sophistication of the dynamic speed limit system (basic roadside, advanced roadside, and advanced in-car) and the situational condition (dangerous-non-dangerous) were varied. The homogeneity of driving speed, the rated credibility of the posted speed limit and the acceptance of the different dynamic speed limit systems were assessed. The results show that the homogeneity of individual speeds, defined as the variation in driving speed for an individual subject along a particular road section, was higher with the dynamic speed limit system than with the static speed limit system. The more sophisticated dynamic speed limit system tested within this study led to higher homogeneity than the less sophisticated systems. The acceptance of the dynamic speed limit systems used in this study was positive, they were perceived as quite useful and rather satisfactory.
Identification of dynamic systems, theory and formulation
NASA Technical Reports Server (NTRS)
Maine, R. E.; Iliff, K. W.
1985-01-01
The problem of estimating parameters of dynamic systems is addressed in order to present the theoretical basis of system identification and parameter estimation in a manner that is complete and rigorous, yet understandable with minimal prerequisites. Maximum likelihood and related estimators are highlighted. The approach used requires familiarity with calculus, linear algebra, and probability, but does not require knowledge of stochastic processes or functional analysis. The treatment emphasizes unification of the various areas in estimation in dynamic systems is treated as a direct outgrowth of the static system theory. Topics covered include basic concepts and definitions; numerical optimization methods; probability; statistical estimators; estimation in static systems; stochastic processes; state estimation in dynamic systems; output error, filter error, and equation error methods of parameter estimation in dynamic systems, and the accuracy of the estimates.
Discovering independent parameters in complex dynamical systems
Lainscsek, Claudia; Weyhenmeyer, Jonathan; Sejnowski, Terrence J.; Letellier, Christophe
2015-01-01
The transformation of a nonlinear dynamical system into a standard form by using one of its variables and its successive derivatives can be used to identify the relationships that may exist between the parameters of the original system such as the subset of the parameter space over which the dynamics is left invariant. We show how the size of the attractor or the time scale (the pseudo-period) can be varied without affecting the underlying dynamics. This is demonstrated for the Rössler and the Lorenz systems. We also consider the case when two Rössler systems are unidirectionally coupled and when a Lorenz system is driven by a Rössler system. In both cases, the dynamics of the coupled system is affected. PMID:25983399
Parallel Wavefront Analysis for a 4D Interferometer
NASA Technical Reports Server (NTRS)
Rao, Shanti R.
2011-01-01
This software provides a programming interface for automating data collection with a PhaseCam interferometer from 4D Technology, and distributing the image-processing algorithm across a cluster of general-purpose computers. Multiple instances of 4Sight (4D Technology s proprietary software) run on a networked cluster of computers. Each connects to a single server (the controller) and waits for instructions. The controller directs the interferometer to several images, then assigns each image to a different computer for processing. When the image processing is finished, the server directs one of the computers to collate and combine the processed images, saving the resulting measurement in a file on a disk. The available software captures approximately 100 images and analyzes them immediately. This software separates the capture and analysis processes, so that analysis can be done at a different time and faster by running the algorithm in parallel across several processors. The PhaseCam family of interferometers can measure an optical system in milliseconds, but it takes many seconds to process the data so that it is usable. In characterizing an adaptive optics system, like the next generation of astronomical observatories, thousands of measurements are required, and the processing time quickly becomes excessive. A programming interface distributes data processing for a PhaseCam interferometer across a Windows computing cluster. A scriptable controller program coordinates data acquisition from the interferometer, storage on networked hard disks, and parallel processing. Idle time of the interferometer is minimized. This architecture is implemented in Python and JavaScript, and may be altered to fit a customer s needs.
Four-dimensional (4D) PET/CT imaging of the thorax
Nehmeh, S.A.; Erdi, Y.E.; Pan, T.
2004-12-01
We have reported in our previous studies on the methodology, and feasibility of 4D-PET (Gated PET) acquisition, to reduce respiratory motion artifact in PET imaging of the thorax. In this study, we expand our investigation to address the problem of respiration motion in PET/CT imaging. The respiratory motion of four lung cancer patients were monitored by tracking external markers placed on the thorax. A 4D-CT acquisition was performed using a 'step-and-shoot' technique, in which computed tomography (CT) projection data were acquired over a complete respiratory cycle at each couch position. The period of each CT acquisition segment was time stamped with an 'x-ray ON' signal, which was recorded by the tracking system. 4D-CT data were then sorted into 10 groups, according to their corresponding phase of the breathing cycle. 4D-PET data were acquired in the gated mode, where each breathing cycle was divided into ten 0.5 s bins. For both CT and PET acquisitions, patients received audio prompting to regularize breathing. The 4D-CT and 4D-PET data were then correlated according to respiratory phase. The effect of 4D acquisition on improving the co-registration of PET and CT images, reducing motion smearing, and consequently increase the quantitation of the SUV, were investigated. Also, quantitation of the tumor motions in PET, and CT, were studied and compared. 4D-PET with matching phase 4D-CTAC showed an improved accuracy in PET-CT image co-registration of up to 41%, compared to measurements from 4D-PET with clinical-CTAC. Gating PET data in correlation with respiratory motion reduced motion-induced smearing, thereby decreasing the observed tumor volume, by as much as 43%. 4D-PET lesions volumes showed a maximum deviation of 19% between clinical CT and phase- matched 4D-CT attenuation corrected PET images. In CT, 4D acquisition resulted in increasing the tumor volume in two patients by up to 79%, and decreasing it in the other two by up to 35%. Consequently, these
Phosphodiesterase 4D Inhibitors Limit Prostate Cancer Growth Potential
Powers, Ginny L.; Hammer, Kimberly D.P.; Domenech, Maribella; Frantskevich, Katsiaryna; Malinowski, Rita L.; Bushman, Wade; Beebe, David J.; Marker, Paul C.
2014-01-01
Phosphodiesterase 4D (PDE4D) has recently been implicated as a proliferation-promoting factor in prostate cancer and is over-expressed in human prostate carcinoma. However, the effects of PDE4D inhibition using pharmacological inhibitors have not been examined in prostate cancer. These studies examined the effects of selective PDE4D inhibitors, NVP-ABE171 and cilomilast, as anti-prostate cancer therapies in both in vitro and in vivo models. The effects of PDE4D inhibitors on pathways that are critical in prostate cancer and/or downstream of cyclic AMP (cAMP) were examined. Both NVP-ABE171 and cilomilast decreased cell growth. In vitro, PDE4D inhibitors lead to decreased signaling of the sonic hedgehog (SHH), Androgen Receptor (AR), and MAPK pathways, but growth inhibition was best correlated to the sonic hedgehog pathway. PDE4D inhibition also reduced proliferation of epithelial cells induced by paracrine signaling from co-cultured stromal cells that had activated hedgehog signaling. In addition, PDE4D inhibitors decreased the weight of the prostate in wild-type mice. Prostate cancer xenografts grown in nude mice that were treated with cilomilast or NVP-ABE171 had decreased wet weight and increased apoptosis compared to vehicle treated controls. These studies suggest the pharmacological inhibition of PDE4D using small molecule inhibitors is an effective option for prostate cancer therapy. Implications PDE4D inhibitors decrease the growth of prostate cancer cells in vivo and in vitro, and PDE4D inhibition has therapeutic potential in prostate cancer. PMID:25149359
Biolabeling with 2,4-dichlorophenoxyacetic acid derivatives: the 2,4-D tag.
Bade, Steffen; Röckendorf, Niels; Franek, Milan; Gorris, Hans H; Lindner, Buko; Olivier, Verena; Schaper, Klaus-Jürgen; Frey, Andreas
2009-12-01
Many bioanalytic and diagnostic procedures rely on labels with which the molecule of interest can be tracked in or discriminated from accompanying like substances. Herein, we describe a new labeling and detection system based on derivatives of 2,4-dichlorophenoxyacetic acid (2,4-D) and anti-2,4-D antibodies. The 2,4-D system is highly sensitive with a K(D) of 7 x 10(-11) M for the hapten-antibody pair, can be used on a large variety of biomolecules such as proteins, peptides, carbohydrates, and nucleic acids, is not hampered by endogenous backgrounds because 2,4-D is a xenobiotic, and is robust because 2,4-D is a very stable compound that withstands the conditions of most reactions usually performed on biomolecules. With this unique blend of properties, the 2,4-D system compares favorably with its rivals digoxigenin (DIG)/anti-DIG and biotin/(strept)avidin and provides an interesting and powerful tool in biomolecular labeling.
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.
4D subject-specific inverse modeling of the chick embryonic heart outflow tract hemodynamics.
Goenezen, Sevan; Chivukula, Venkat Keshav; Midgett, Madeline; Phan, Ly; Rugonyi, Sandra
2016-06-01
Blood flow plays a critical role in regulating embryonic cardiac growth and development, with altered flow leading to congenital heart disease. Progress in the field, however, is hindered by a lack of quantification of hemodynamic conditions in the developing heart. In this study, we present a methodology to quantify blood flow dynamics in the embryonic heart using subject-specific computational fluid dynamics (CFD) models. While the methodology is general, we focused on a model of the chick embryonic heart outflow tract (OFT), which distally connects the heart to the arterial system, and is the region of origin of many congenital cardiac defects. Using structural and Doppler velocity data collected from optical coherence tomography, we generated 4D ([Formula: see text]) embryo-specific CFD models of the heart OFT. To replicate the blood flow dynamics over time during the cardiac cycle, we developed an iterative inverse-method optimization algorithm, which determines the CFD model boundary conditions such that differences between computed velocities and measured velocities at one point within the OFT lumen are minimized. Results from our developed CFD model agree with previously measured hemodynamics in the OFT. Further, computed velocities and measured velocities differ by [Formula: see text]15 % at locations that were not used in the optimization, validating the model. The presented methodology can be used in quantifications of embryonic cardiac hemodynamics under normal and altered blood flow conditions, enabling an in-depth quantitative study of how blood flow influences cardiac development.
Dynamical systems, attractors, and neural circuits.
Miller, Paul
2016-01-01
Biology is the study of dynamical systems. Yet most of us working in biology have limited pedagogical training in the theory of dynamical systems, an unfortunate historical fact that can be remedied for future generations of life scientists. In my particular field of systems neuroscience, neural circuits are rife with nonlinearities at all levels of description, rendering simple methodologies and our own intuition unreliable. Therefore, our ideas are likely to be wrong unless informed by good models. These models should be based on the mathematical theories of dynamical systems since functioning neurons are dynamic-they change their membrane potential and firing rates with time. Thus, selecting the appropriate type of dynamical system upon which to base a model is an important first step in the modeling process. This step all too easily goes awry, in part because there are many frameworks to choose from, in part because the sparsely sampled data can be consistent with a variety of dynamical processes, and in part because each modeler has a preferred modeling approach that is difficult to move away from. This brief review summarizes some of the main dynamical paradigms that can arise in neural circuits, with comments on what they can achieve computationally and what signatures might reveal their presence within empirical data. I provide examples of different dynamical systems using simple circuits of two or three cells, emphasizing that any one connectivity pattern is compatible with multiple, diverse functions.
Information Processing Capacity of Dynamical Systems
Dambre, Joni; Verstraeten, David; Schrauwen, Benjamin; Massar, Serge
2012-01-01
Many dynamical systems, both natural and artificial, are stimulated by time dependent external signals, somehow processing the information contained therein. We demonstrate how to quantify the different modes in which information can be processed by such systems and combine them to define the computational capacity of a dynamical system. This is bounded by the number of linearly independent state variables of the dynamical system, equaling it if the system obeys the fading memory condition. It can be interpreted as the total number of linearly independent functions of its stimuli the system can compute. Our theory combines concepts from machine learning (reservoir computing), system modeling, stochastic processes, and functional analysis. We illustrate our theory by numerical simulations for the logistic map, a recurrent neural network, and a two-dimensional reaction diffusion system, uncovering universal trade-offs between the non-linearity of the computation and the system's short-term memory. PMID:22816038
32 CFR 1645.4 - Exclusion from Class 4-D.
Code of Federal Regulations, 2010 CFR
2010-07-01
... MINISTERS OF RELIGION § 1645.4 Exclusion from Class 4-D. A registrant is excluded from Class 4-D when his... duly ordained minister of religion in accordance with the ceremonial rite or discipline of a church... principles of religion and administer the ordinances of public worship, as embodied in the creed...
32 CFR 1645.4 - Exclusion from Class 4-D.
Code of Federal Regulations, 2014 CFR
2014-07-01
... MINISTERS OF RELIGION § 1645.4 Exclusion from Class 4-D. A registrant is excluded from Class 4-D when his... duly ordained minister of religion in accordance with the ceremonial rite or discipline of a church... principles of religion and administer the ordinances of public worship, as embodied in the creed...
32 CFR 1645.4 - Exclusion from Class 4-D.
Code of Federal Regulations, 2012 CFR
2012-07-01
... MINISTERS OF RELIGION § 1645.4 Exclusion from Class 4-D. A registrant is excluded from Class 4-D when his... duly ordained minister of religion in accordance with the ceremonial rite or discipline of a church... principles of religion and administer the ordinances of public worship, as embodied in the creed...
32 CFR 1645.4 - Exclusion from Class 4-D.
Code of Federal Regulations, 2013 CFR
2013-07-01
... MINISTERS OF RELIGION § 1645.4 Exclusion from Class 4-D. A registrant is excluded from Class 4-D when his... duly ordained minister of religion in accordance with the ceremonial rite or discipline of a church... principles of religion and administer the ordinances of public worship, as embodied in the creed...
32 CFR 1645.4 - Exclusion from Class 4-D.
Code of Federal Regulations, 2011 CFR
2011-07-01
... MINISTERS OF RELIGION § 1645.4 Exclusion from Class 4-D. A registrant is excluded from Class 4-D when his... duly ordained minister of religion in accordance with the ceremonial rite or discipline of a church... principles of religion and administer the ordinances of public worship, as embodied in the creed...
TRADES: TRAnsits and Dynamics of Exoplanetary Systems
NASA Astrophysics Data System (ADS)
Borsato, Luca
2016-01-01
TRADES (TRAnsits and Dynamics of Exoplanetary Systems) simultaneously fits observed radial velocities and transit times data to determine the orbital parameters of exoplanetary systems from observational data. It uses a dynamical simulator for N-body systems that also fits the available data during the orbital integration and determines the best combination of the orbital parameters using grid search, χ2 minimization, genetic algorithms, particle swarm optimization, and bootstrap analysis.
Session 6: Dynamic Modeling and Systems Analysis
NASA Technical Reports Server (NTRS)
Csank, Jeffrey; Chapman, Jeffryes; May, Ryan
2013-01-01
These presentations cover some of the ongoing work in dynamic modeling and dynamic systems analysis. The first presentation discusses dynamic systems analysis and how to integrate dynamic performance information into the systems analysis. The ability to evaluate the dynamic performance of an engine design may allow tradeoffs between the dynamic performance and operability of a design resulting in a more efficient engine design. The second presentation discusses the Toolbox for Modeling and Analysis of Thermodynamic Systems (T-MATS). T-MATS is a Simulation system with a library containing the basic building blocks that can be used to create dynamic Thermodynamic Systems. Some of the key features include Turbo machinery components, such as turbines, compressors, etc., and basic control system blocks. T-MAT is written in the Matlab-Simulink environment and is open source software. The third presentation focuses on getting additional performance from the engine by allowing the limit regulators only to be active when a limit is danger of being violated. Typical aircraft engine control architecture is based on MINMAX scheme, which is designed to keep engine operating within prescribed mechanical/operational safety limits. Using a conditionally active min-max limit regulator scheme, additional performance can be gained by disabling non-relevant limit regulators
Seed conformal blocks in 4D CFT
NASA Astrophysics Data System (ADS)
Echeverri, Alejandro Castedo; Elkhidir, Emtinan; Karateev, Denis; Serone, Marco
2016-02-01
We compute in closed analytical form the minimal set of "seed" conformal blocks associated to the exchange of generic mixed symmetry spinor/tensor operators in an arbitrary representation ( ℓ, overline{ℓ} ) of the Lorentz group in four dimensional conformal field theories. These blocks arise from 4-point functions involving two scalars, one (0, | ℓ - overline{7ell;} |) and one (| ℓ - overline{ℓ} |, 0) spinors or tensors. We directly solve the set of Casimir equations, that can elegantly be written in a compact form for any ( ℓ, overline{ℓ} ), by using an educated ansatz and reducing the problem to an algebraic linear system. Various details on the form of the ansatz have been deduced by using the so called shadow formalism. The complexity of the conformal blocks depends on the value of p = | ℓ - overline{ℓ} | and grows with p, in analogy to what happens to scalar conformal blocks in d even space-time dimensions as d increases. These results open the way to bootstrap 4-point functions involving arbitrary spinor/tensor operators in four dimensional conformal field theories.
Partial Dynamical Symmetry in Nuclear Systems
Escher, J E
2003-06-02
Partial dynamical symmetry (PDS) extends and complements the concepts of exact and dynamical symmetry. It allows one to remove undesired constraints from an algebraic theory, while preserving some of the useful aspects of a dynamical symmetry, and to study the effects of symmetry breaking in a controlled manner. An example of a PDS in an interacting fermion system is presented. The associated PDS Hamiltonians are closely related with a realistic quadrupole-quadrupole interaction and provide new insights into this important interaction.
Categorizing dynamic textures using a bag of dynamical systems.
Ravichandran, Avinash; Chaudhry, Rizwan; Vidal, René
2013-02-01
We consider the problem of categorizing video sequences of dynamic textures, i.e., nonrigid dynamical objects such as fire, water, steam, flags, etc. This problem is extremely challenging because the shape and appearance of a dynamic texture continuously change as a function of time. State-of-the-art dynamic texture categorization methods have been successful at classifying videos taken from the same viewpoint and scale by using a Linear Dynamical System (LDS) to model each video, and using distances or kernels in the space of LDSs to classify the videos. However, these methods perform poorly when the video sequences are taken under a different viewpoint or scale. In this paper, we propose a novel dynamic texture categorization framework that can handle such changes. We model each video sequence with a collection of LDSs, each one describing a small spatiotemporal patch extracted from the video. This Bag-of-Systems (BoS) representation is analogous to the Bag-of-Features (BoF) representation for object recognition, except that we use LDSs as feature descriptors. This choice poses several technical challenges in adopting the traditional BoF approach. Most notably, the space of LDSs is not euclidean; hence, novel methods for clustering LDSs and computing codewords of LDSs need to be developed. We propose a framework that makes use of nonlinear dimensionality reduction and clustering techniques combined with the Martin distance for LDSs to tackle these issues. Our experiments compare the proposed BoS approach to existing dynamic texture categorization methods and show that it can be used for recognizing dynamic textures in challenging scenarios which could not be handled by existing methods. PMID:23257470
SIAM conference on applications of dynamical systems
Not Available
1992-01-01
A conference (Oct.15--19, 1992, Snowbird, Utah; sponsored by SIAM (Society for Industrial and Applied Mathematics) Activity Group on Dynamical Systems) was held that highlighted recent developments in applied dynamical systems. The main lectures and minisymposia covered theory about chaotic motion, applications in high energy physics and heart fibrillations, turbulent motion, Henon map and attractor, integrable problems in classical physics, pattern formation in chemical reactions, etc. The conference fostered an exchange between mathematicians working on theoretical issues of modern dynamical systems and applied scientists. This two-part document contains abstracts, conference program, and an author index.
Dynamic stability experiment of Maglev systems
Cai, Y.; Mulcahy, T.M.; Chen, S.S.
1995-04-01
This report summarizes the research performed on Maglev vehicle dynamic stability at Argonne National Laboratory during the past few years. It also documents magnetic-force data obtained from both measurements and calculations. Because dynamic instability is not acceptable for any commercial Maglev system, it is important to consider this phenomenon in the development of all Maglev systems. This report presents dynamic stability experiments on Maglev systems and compares their numerical simulation with predictions calculated by a nonlinear dynamic computer code. Instabilities of an electrodynamic system (EDS)-type vehicle model were obtained from both experimental observations and computer simulations for a five-degree-of-freedom Maglev vehicle moving on a guideway consisting of double L-shaped aluminum segments attached to a rotating wheel. The experimental and theoretical analyses developed in this study identify basic stability characteristics and future research needs of Maglev systems.
Functional systems with orthogonal dynamic covalent bonds.
Wilson, Adam; Gasparini, Giulio; Matile, Stefan
2014-03-21
This review summarizes the use of orthogonal dynamic covalent bonds to build functional systems. Dynamic covalent bonds are unique because of their dual nature. They can be as labile as non-covalent interactions or as permanent as covalent bonds, depending on conditions. Examples from nature, reaching from the role of disulfides in protein folding to thioester exchange in polyketide biosynthesis, indicate how dynamic covalent bonds are best used in functional systems. Several synthetic functional systems that employ a single type of dynamic covalent bonds have been reported. Considering that most functional systems make simultaneous use of several types of non-covalent interactions together, one would expect the literature to contain many examples in which different types of dynamic covalent bonds are similarly used in tandem. However, the incorporation of orthogonal dynamic covalent bonds into functional systems is a surprisingly rare and recent development. This review summarizes the available material comprehensively, covering a remarkably diverse collection of functions. However, probably more revealing than the specific functions addressed is that the questions asked are consistently quite unusual, very demanding and highly original, focusing on molecular systems that can self-sort, self-heal, adapt, exchange, replicate, transcribe, or even walk and "think" (logic gates). This focus on adventurous chemistry off the beaten track supports the promise that with orthogonal dynamic covalent bonds we can ask questions that otherwise cannot be asked. The broad range of functions and concepts covered should appeal to the supramolecular organic chemist but also to the broader community. PMID:24287608
Dynamical systems, attractors, and neural circuits
Miller, Paul
2016-01-01
Biology is the study of dynamical systems. Yet most of us working in biology have limited pedagogical training in the theory of dynamical systems, an unfortunate historical fact that can be remedied for future generations of life scientists. In my particular field of systems neuroscience, neural circuits are rife with nonlinearities at all levels of description, rendering simple methodologies and our own intuition unreliable. Therefore, our ideas are likely to be wrong unless informed by good models. These models should be based on the mathematical theories of dynamical systems since functioning neurons are dynamic—they change their membrane potential and firing rates with time. Thus, selecting the appropriate type of dynamical system upon which to base a model is an important first step in the modeling process. This step all too easily goes awry, in part because there are many frameworks to choose from, in part because the sparsely sampled data can be consistent with a variety of dynamical processes, and in part because each modeler has a preferred modeling approach that is difficult to move away from. This brief review summarizes some of the main dynamical paradigms that can arise in neural circuits, with comments on what they can achieve computationally and what signatures might reveal their presence within empirical data. I provide examples of different dynamical systems using simple circuits of two or three cells, emphasizing that any one connectivity pattern is compatible with multiple, diverse functions. PMID:27408709
TIME DELAY SYSTEMS WITH DISTRIBUTION DEPENDENT DYNAMICS
Banks, H. T.; Dediu, Sava; Nguyen, Hoan K.
2009-01-01
General delay dynamical systems in which uncertainty is present in the form of probability measure dependent dynamics are considered. Several motivating examples arising in biology are discussed. A functional analytic framework for investigating well–posedness (existence, uniqueness and continuous dependence of solutions), inverse problems, sensitivity analysis and approximations of the measures for computational purposes is surveyed. PMID:19865602
TIME DELAY SYSTEMS WITH DISTRIBUTION DEPENDENT DYNAMICS.
Banks, H T; Dediu, Sava; Nguyen, Hoan K
2007-01-01
General delay dynamical systems in which uncertainty is present in the form of probability measure dependent dynamics are considered. Several motivating examples arising in biology are discussed. A functional analytic framework for investigating well-posedness (existence, uniqueness and continuous dependence of solutions), inverse problems, sensitivity analysis and approximations of the measures for computational purposes is surveyed.
Dynamic testing of docking system hardware
NASA Technical Reports Server (NTRS)
Dorland, W. D.
1972-01-01
Extensive dynamic testing was conducted to verify the flight readiness of the Apollo docking hardware. Testing was performed on a unique six degree-of-freedom motion simulator controlled by a computer that calculated the associated spacecraft motions. The test system and the results obtained by subjecting flight-type docking hardware to actual impact loads and resultant spacecraft dynamics are described.
Infrared PINEM developed by diffraction in 4D UEM
Liu, Haihua; Baskin, John Spencer; Zewail, Ahmed H.
2016-01-01
The development of four-dimensional ultrafast electron microscopy (4D UEM) has enabled not only observations of the ultrafast dynamics of photon–matter interactions at the atomic scale with ultrafast resolution in image, diffraction, and energy space, but photon–electron interactions in the field of nanoplasmonics and nanophotonics also have been captured by the related technique of photon-induced near-field electron microscopy (PINEM) in image and energy space. Here we report a further extension in the ongoing development of PINEM using a focused, nanometer-scale, electron beam in diffraction space for measurements of infrared-light-induced PINEM. The energy resolution in diffraction mode is unprecedented, reaching 0.63 eV under the 200-keV electron beam illumination, and separated peaks of the PINEM electron-energy spectrum induced by infrared light of wavelength 1,038 nm (photon energy 1.2 eV) have been well resolved for the first time, to our knowledge. In a comparison with excitation by green (519-nm) pulses, similar first-order PINEM peak amplitudes were obtained for optical fluence differing by a factor of more than 60 at the interface of copper metal and vacuum. Under high fluence, the nonlinear regime of IR PINEM was observed, and its spatial dependence was studied. In combination with PINEM temporal gating and low-fluence infrared excitation, the PINEM diffraction method paves the way for studies of structural dynamics in reciprocal space and energy space with high temporal resolution. PMID:26848135
NASA Technical Reports Server (NTRS)
Dermott, Stanley F.
2002-01-01
The ongoing aim of the research is to investigate the dynamical and physical evolution of interplanetary dust particles in order to produce a detailed global model of the zodiacal cloud and its constituent components that is capable of predicting thermal fluxes in mid-infrared wave bands to an accuracy of 1% or better; with the additional aim of exploiting this research as a basis for predicting structure in exozodiacal clouds that may be signatures of unseen planets.
Constraint Embedding for Multibody System Dynamics
NASA Technical Reports Server (NTRS)
Jain, Abhinandan
2009-01-01
This paper describes a constraint embedding approach for the handling of local closure constraints in multibody system dynamics. The approach uses spatial operator techniques to eliminate local-loop constraints from the system and effectively convert the system into tree-topology systems. This approach allows the direct derivation of recursive O(N) techniques for solving the system dynamics and avoiding the expensive steps that would otherwise be required for handling the closedchain dynamics. The approach is very effective for systems where the constraints are confined to small-subgraphs within the system topology. The paper provides background on the spatial operator O(N) algorithms, the extensions for handling embedded constraints, and concludes with some examples of such constraints.
The investigation of tethered satellite system dynamics
NASA Technical Reports Server (NTRS)
Lorenzini, E.
1984-01-01
Tethered satellite system (TSS) dynamics were studied. The dynamic response of the TSS during the entire stationkeeping phase for the first electrodynamic mission was investigated. An out of plane swing amplitude and the tether's bowing were observed. The dynamics of the slack tether was studied and computer code, SLACK2, was improved both in capabilities and computational speed. Speed hazard related to tether breakage or plasma contactor failure was examined. Preliminary values of the potential difference after the failure and of the drop of the electric field along the tether axis have been computed. The update of the satellite rotational dynamics model is initiated.
Live 4D optical coherence tomography for early embryonic mouse cardiac phenotyping
NASA Astrophysics Data System (ADS)
Lopez, Andrew L.; Wang, Shang; Larin, Kirill V.; Overbeek, Paul A.; Larina, Irina V.
2016-03-01
Studying embryonic mouse development is important for our understanding of normal human embryogenesis and the underlying causes of congenital defects. Our research focuses on imaging early development in the mouse embryo to specifically understand cardiovascular development using optical coherence tomography (OCT). We have previously developed imaging approaches that combine static embryo culture, OCT imaging and advanced image processing to visualize the whole live mouse embryos and obtain 4D (3D+time) cardiodynamic datasets with cellular resolution. Here, we present the study of using 4D OCT for dynamic imaging of early embryonic heart in live mouse embryos to assess mutant cardiac phenotypes during development, including a cardiac looping defect. Our results indicate that the live 4D OCT imaging approach is an efficient phenotyping tool that can reveal structural and functional cardiac defects at very early stages. Further studies integrating live embryonic cardiodynamic phenotyping with molecular and genetic approaches in mouse mutants will help to elucidate the underlying signaling defects.
Dynamics and controls in MAGLEV systems
NASA Astrophysics Data System (ADS)
Cai, Y.; Chen, S. S.; Rote, D. M.
1992-09-01
The dynamic response of magnetically levitated (maglev) ground transportation systems has important consequences for safety and ride quality, guideway design, and system costs. Ride quality is determined by vehicle response and by environmental factors such as humidity and noise. The dynamic response of the vehicles is the key element in determining ride quality, and vehicle stability is an important safety-related element. To design a proper guideway that provides acceptable ride quality in the stable region, vehicle dynamics must be understood. Furthermore, the trade-off between guideway smoothness and the levitation and control systems must be considered if maglev systems are to be economically feasible. The link between the guideway and the other maglev components is vehicle dynamics. For a commercial maglev system, vehicle dynamics must be analyzed and tested in detail. In this study, the role of dynamics and controls in maglev vehicle/guideway interactions is discussed, and the literature on modeling the dynamic interactions of vehicle/guideway and suspension controls for ground vehicles is reviewed.
4D-fingerprints, universal QSAR and QSPR descriptors.
Senese, Craig L; Duca, J; Pan, D; Hopfinger, A J; Tseng, Y J
2004-01-01
An elusive goal in the field of chemoinformatics and molecular modeling has been the generation of a set of descriptors that, once calculated for a molecule, may be used in a wide variety of applications. Since such universal descriptors are generated free from external constraints, they are inherently independent of the data set in which they are employed. The realization of a set of universal descriptors would significantly streamline such chemoinformatics tasks as virtual high-throughout screening (VHTS) and toxicity profiling. The current study reports the derivation and validation of a potential set of universal descriptors, referred to as the 4D-fingerprints. The 4D-fingerprints are derived from the 4D-molecular similarity analysis. To evaluate the applicability of the 4D-fingerprints as universal descriptors, they are used to generate descriptive QSAR models for 5 independent training sets. Each of the training sets has been analyzed previously by several varying QSAR methods, and the results of the models generated using the 4D-fingerprints are compared to the results of the previous QSAR analyses. It was found that the models generated using the 4D-fingerprints are comparable in quality, based on statistical measures of fit and test set prediction, to the previously reported models for the other QSAR methods. This finding is particularly significant considering the 4D-fingerprints are generated independent of external constraints such as alignment, while the QSAR methods used for comparison all require an alignment analysis.
System Dynamics Models and Institutional Pricing Decisions.
ERIC Educational Resources Information Center
Chen, Fiona
1986-01-01
A system dynamics model for the pricing of tuition is presented, illustrating how such models enable decision-makers to anticipate cause-and-effect relationships and test alternative courses of action. (Author)
Constructing minimal models for complex system dynamics
NASA Astrophysics Data System (ADS)
Barzel, Baruch; Liu, Yang-Yu; Barabási, Albert-László
2015-05-01
One of the strengths of statistical physics is the ability to reduce macroscopic observations into microscopic models, offering a mechanistic description of a system's dynamics. This paradigm, rooted in Boltzmann's gas theory, has found applications from magnetic phenomena to subcellular processes and epidemic spreading. Yet, each of these advances were the result of decades of meticulous model building and validation, which are impossible to replicate in most complex biological, social or technological systems that lack accurate microscopic models. Here we develop a method to infer the microscopic dynamics of a complex system from observations of its response to external perturbations, allowing us to construct the most general class of nonlinear pairwise dynamics that are guaranteed to recover the observed behaviour. The result, which we test against both numerical and empirical data, is an effective dynamic model that can predict the system's behaviour and provide crucial insights into its inner workings.
Dynamic Impregnator Reactor System (Poster)
Not Available
2012-09-01
IBRF poster developed for the IBRF showcase. Describes the multifarious system designed for complex feedstock impregnation and processing. IBRF feedstock system has several unit operations combined into one robust system that provides for flexible and staged process configurations, such as spraying, soaking, low-severity pretreatment, enzymatic hydrolysis, fermentation, concentration/evaporation, and distillation.
Detecting Recurrence Domains of Dynamical Systems by Symbolic Dynamics
NASA Astrophysics Data System (ADS)
Graben, Peter beim; Hutt, Axel
2013-04-01
We propose an algorithm for the detection of recurrence domains of complex dynamical systems from time series. Our approach exploits the characteristic checkerboard texture of recurrence domains exhibited in recurrence plots. In phase space, recurrence plots yield intersecting balls around sampling points that could be merged into cells of a phase space partition. We construct this partition by a rewriting grammar applied to the symbolic dynamics of time indices. A maximum entropy principle defines the optimal size of intersecting balls. The final application to high-dimensional brain signals yields an optimal symbolic recurrence plot revealing functional components of the signal.
Dynamics and kinematics of simple neural systems
Rabinovich, M. |; Selverston, A.; Rubchinsky, L.; Huerta, R.
1996-09-01
The dynamics of simple neural systems is of interest to both biologists and physicists. One of the possible roles of such systems is the production of rhythmic patterns, and their alterations (modification of behavior, processing of sensory information, adaptation, control). In this paper, the neural systems are considered as a subject of modeling by the dynamical systems approach. In particular, we analyze how a stable, ordinary behavior of a small neural system can be described by simple finite automata models, and how more complicated dynamical systems modeling can be used. The approach is illustrated by biological and numerical examples: experiments with and numerical simulations of the stomatogastric central pattern generators network of the California spiny lobster. {copyright} {ital 1996 American Institute of Physics.}
Model systems for single molecule polymer dynamics
Latinwo, Folarin
2012-01-01
Double stranded DNA (dsDNA) has long served as a model system for single molecule polymer dynamics. However, dsDNA is a semiflexible polymer, and the structural rigidity of the DNA double helix gives rise to local molecular properties and chain dynamics that differ from flexible chains, including synthetic organic polymers. Recently, we developed single stranded DNA (ssDNA) as a new model system for single molecule studies of flexible polymer chains. In this work, we discuss model polymer systems in the context of “ideal” and “real” chain behavior considering thermal blobs, tension blobs, hydrodynamic drag and force–extension relations. In addition, we present monomer aspect ratio as a key parameter describing chain conformation and dynamics, and we derive dynamical scaling relations in terms of this molecular-level parameter. We show that asymmetric Kuhn segments can suppress monomer–monomer interactions, thereby altering global chain dynamics. Finally, we discuss ssDNA in the context of a new model system for single molecule polymer dynamics. Overall, we anticipate that future single polymer studies of flexible chains will reveal new insight into the dynamic behavior of “real” polymers, which will highlight the importance of molecular individualism and the prevalence of non-linear phenomena. PMID:22956980
Irreversible thermodynamics in multiscale stochastic dynamical systems.
Santillán, Moisés; Qian, Hong
2011-04-01
This work extends the results of a recently developed theory of a rather complete thermodynamic formalism for discrete-state, continuous-time Markov processes with and without detailed balance. We investigate whether and in what way the thermodynamic structure is invariant in a multiscale stochastic system, that is, whether the relations between thermodynamic functions of state and process variables remain unchanged when the system is viewed at different time scales and resolutions. Our results show that the dynamics on a fast time scale contribute an entropic term to the internal energy function u(S)(x) for the slow dynamics. Based on the conditional free energy u(S)(x), we can then treat the slow dynamics as if the fast dynamics is nonexistent. Furthermore, we show that the free energy, which characterizes the spontaneous organization in a system without detailed balance, is invariant with or without the fast dynamics: The fast dynamics is assumed to reach stationarity instantaneously on the slow time scale; it has no effect on the system's free energy. The same cannot be said for the entropy and the internal energy, both of which contain the same contribution from the fast dynamics. We also investigate the consequences of time-scale separation in connection to the concepts of quasi-stationarity and steady adiabaticity introduced in the phenomenological steady-state thermodynamics.
Dynamics and controls in maglev systems
Cai, Y.; Chen, S.S.; Rote, D.M.
1992-09-01
The dynamic response of magnetically levitated (maglev) ground transportation systems has important consequences for safety and ride quality, guideway design, and system costs. Ride quality is determined by vehicle response and by environmental factors such as humidity and noise. The dynamic response of the vehicles is the key element in determining ride quality, and vehicle stability is an important safety-related element. To design a proper guideway that provides acceptable ride quality in the stable region, vehicle dynamics must be understood. Furthermore the trade-off between guideway smoothness and the levitation and control systems must be considered if maglev systems are to be economically feasible. The link between the guideway and the other maglev components is vehicle dynamics. For a commercial maglev system, vehicle dynamics must be analyzed and tested in detail. In this study, the role of dynamics and controls in maglev vehicle/guideway interactions is discussed, and the literature on modeling the dynamic interactions of vehicle/guideway and suspension controls for ground vehicles is reviewed. Particular emphasis is placed on modeling vehicle/guideway interactions and response characteristics of maglev systems for a multicar, multiload vehicle traveling on a single- or doublespan flexible guideway, including coupling effects of vehicle/guideway, comparison of concentrated and distributed loads, and ride comfort. Different control-law designs are introduced into vehicle suspensions when a simple two-degree-of-freedom vehicle model is applied. Active and semiactive control designs for primary and secondary suspensions do improve the response of vehicle and provide acceptable ride comfort. Finally, future research associated with dynamics and controls of vehicle/guideway systems is identified.
Dynamic modeling of solar dynamic components and systems
NASA Astrophysics Data System (ADS)
Hochstein, John I.; Korakianitis, T.
1992-09-01
The purpose of this grant was to support NASA in modeling efforts to predict the transient dynamic and thermodynamic response of the space station solar dynamic power generation system. In order to meet the initial schedule requirement of providing results in time to support installation of the system as part of the initial phase of space station, early efforts were executed with alacrity and often in parallel. Initially, methods to predict the transient response of a Rankine as well as a Brayton cycle were developed. Review of preliminary design concepts led NASA to select a regenerative gas-turbine cycle using a helium-xenon mixture as the working fluid and, from that point forward, the modeling effort focused exclusively on that system. Although initial project planning called for a three year period of performance, revised NASA schedules moved system installation to later and later phases of station deployment. Eventually, NASA selected to halt development of the solar dynamic power generation system for space station and to reduce support for this project to two-thirds of the original level.
Dynamic Modeling of Solar Dynamic Components and Systems
NASA Technical Reports Server (NTRS)
Hochstein, John I.; Korakianitis, T.
1992-01-01
The purpose of this grant was to support NASA in modeling efforts to predict the transient dynamic and thermodynamic response of the space station solar dynamic power generation system. In order to meet the initial schedule requirement of providing results in time to support installation of the system as part of the initial phase of space station, early efforts were executed with alacrity and often in parallel. Initially, methods to predict the transient response of a Rankine as well as a Brayton cycle were developed. Review of preliminary design concepts led NASA to select a regenerative gas-turbine cycle using a helium-xenon mixture as the working fluid and, from that point forward, the modeling effort focused exclusively on that system. Although initial project planning called for a three year period of performance, revised NASA schedules moved system installation to later and later phases of station deployment. Eventually, NASA selected to halt development of the solar dynamic power generation system for space station and to reduce support for this project to two-thirds of the original level.
Fast X-ray micro-CT for real-time 4D observation
NASA Astrophysics Data System (ADS)
Takano, H.; Yoshida, K.; Tsuji, T.; Koyama, T.; Tsusaka, Y.; Kagoshima, Y.
2009-09-01
Fast X-ray computed tomography (CT) system with sub-second order measurement for single CT acquisition has been developed. The system, consisting of a high-speed sample rotation stage and a high-speed X-ray camera, is constructed at synchrotron radiation beamline in order to utilize fully intense X-rays. A time-resolving CT movie (i.e. 4D CT) can be available by operating the fast CT system continuously. Real-time observation of water absorbing process of super-absorbent polymer (SAP) has been successfully performed with the 4D CT operation.
Dynamic stability of electrodynamic maglev systems
Cai, Y.; Chen, S.S.; Mulcahy, T.M.; Rote, D.M.
1997-01-01
Because dynamic instabilities are not acceptable in any commercial maglev system, it is important to consider dynamic instability in the development of all maglev systems. This study considers the stability of maglev systems based on mathematical models and experimental data. Divergence and flutter are obtained for coupled vibration of a three-degree-of-freedom maglev vehicle on a guideway consisting of double L-shaped aluminum segments. The theory and analysis for motion-dependent magnetic-force-induced instability developed in this study provides basic stability characteristics and identifies future research needs for maglev systems.
Coupled dynamics analysis of wind energy systems
NASA Technical Reports Server (NTRS)
Hoffman, J. A.
1977-01-01
A qualitative description of all key elements of a complete wind energy system computer analysis code is presented. The analysis system addresses the coupled dynamics characteristics of wind energy systems, including the interactions of the rotor, tower, nacelle, power train, control system, and electrical network. The coupled dynamics are analyzed in both the frequency and time domain to provide the basic motions and loads data required for design, performance verification and operations analysis activities. Elements of the coupled analysis code were used to design and analyze candidate rotor articulation concepts. Fundamental results and conclusions derived from these studies are presented.
Multiple Bifurcations of a Cylindrical Dynamical System
NASA Astrophysics Data System (ADS)
Han, Ning; Cao, Qingjie
2016-03-01
This paper focuses on multiple bifurcations of a cylindrical dynamical system, which is evolved from a rotating pendulum with SD oscillator. The rotating pendulum system exhibits the coupling dynamics property of the bistable state and conventional pendulum with the ho- moclinic orbits of the first and second type. A double Andronov-Hopf bifurcation, two saddle-node bifurcations of periodic orbits and a pair of homoclinic bifurcations are detected by using analytical analysis and nu- merical calculation. It is found that the homoclinic orbits of the second type can bifurcate into a pair of rotational limit cycles, coexisting with the oscillating limit cycle. Additionally, the results obtained herein, are helpful to explore different types of limit cycles and the complex dynamic bifurcation of cylindrical dynamical system.
Modular interdependency in complex dynamical systems.
Watson, Richard A; Pollack, Jordan B
2005-01-01
Herbert A. Simon's characterization of modularity in dynamical systems describes subsystems as having dynamics that are approximately independent of those of other subsystems (in the short term). This fits with the general intuition that modules must, by definition, be approximately independent. In the evolution of complex systems, such modularity may enable subsystems to be modified and adapted independently of other subsystems, whereas in a nonmodular system, modifications to one part of the system may result in deleterious side effects elsewhere in the system. But this notion of modularity and its effect on evolvability is not well quantified and is rather simplistic. In particular, modularity need not imply that intermodule dependences are weak or unimportant. In dynamical systems this is acknowledged by Simon's suggestion that, in the long term, the dynamical behaviors of subsystems do interact with one another, albeit in an "aggregate" manner--but this kind of intermodule interaction is omitted in models of modularity for evolvability. In this brief discussion we seek to unify notions of modularity in dynamical systems with notions of how modularity affects evolvability. This leads to a quantifiable measure of modularity and a different understanding of its effect on evolvability. PMID:16197673
C4d staining as immunohistochemical marker in inflammatory myopathies.
Pytel, Peter
2014-10-01
The diagnosis of an inflammatory myopathy is often established based on basic histologic studies. Additional immunohistochemical studies are sometimes required to support the diagnosis and the classification of inflammatory myopathies. Staining for major histocompatibility complex 1 (MHC1) often shows increased sarcolemmal labeling in inflammatory myopathies. Endomysial capillary staining C5b-9 (membrane attack complex) is a feature that is reported as frequently associated with dermatomyositis. Immunohistochemical staining for C4d is widely used for various applications including the assessment of antibody-mediated rejection after solid organ transplantation. In the context of dermatomyositis, C4d staining has been described in skin biopsies but not in muscle biopsies. A total of 32 muscle biopsy specimens were examined. The hematoxylin and eosin-stained slides were reviewed, and immunohistochemical studies for MHC1, C5b-9, and C4d were conducted. The staining observed for C5b-9 and C4d was compared. Overall, the staining pattern for C4d mirrored the one observed for C5b-9 in the examined muscle biopsy specimens. There was high and statistically significant (P<0.0001) correlation between the staining seen with these 2 antibodies. Both antibodies labeled the cytoplasm of degenerating necrotic myofibers. In addition, both antibodies showed distinct endomysial capillary labeling in a subset of dermatomyositis. Areas with perifascicular atrophy often exhibited the most prominent vascular labeling for C4d and C5b-9. In conclusion, C4d and C5b-9 show similar expression patterns in muscle biopsies of patients with inflammatory myopathies and both highlight the presence of vascular labeling associated with dermatomyositis. C4d antibodies are widely used and may offer an alternative for C5b-9 staining.
Dynamics of Multibody Systems Near Lagrangian Points
NASA Astrophysics Data System (ADS)
Wong, Brian
This thesis examines the dynamics of a physically connected multi-spacecraft system in the vicinity of the Lagrangian points of a Circular Restricted Three-Body System. The spacecraft system is arranged in a wheel-spoke configuration with smaller and less massive satellites connected to a central hub using truss/beams or tether connectors. The kinematics of the system is first defined, and the kinetic, gravitational potential energy and elastic potential energy of the system are derived. The Assumed Modes Method is used to discretize the continuous variables of the system, and a general set of ordinary differential equations describing the dynamics of the connectors and the central hub are obtained using the Lagrangian method. The flexible body dynamics of the tethered and truss connected systems are examined using numerical simulations. The results show that these systems experienced only small elastic deflections when they are naturally librating or rotating at moderate angular velocities, and these deflections have relatively small effect on the attitude dynamics of the systems. Based on these results, it is determined that the connectors can be modeled as rigid when only the attitude dynamics of the system is of interest. The equations of motion of rigid satellites stationed at the Lagrangian points are linearized, and the stability conditions of the satellite are obtained from the linear equations. The required conditions are shown to be similar to those of geocentric satellites. Study of the linear equations also revealed the resonant conditions of rigid Lagrangian point satellites, when a librational natural frequency of the satellite matches the frequency of its station-keeping orbit leading to large attitude motions. For tethered satellites, the linear analysis shows that the tethers are in stable equilibrium when they lie along a line joining the two primary celestial bodies of the Three-Body System. Numerical simulations are used to study the long term
Substitutional 4d and 5d impurities in graphene.
Alonso-Lanza, Tomás; Ayuela, Andrés; Aguilera-Granja, Faustino
2016-08-21
We describe the structural and electronic properties of graphene doped with substitutional impurities of 4d and 5d transition metals. The adsorption energies and distances for 4d and 5d metals in graphene show similar trends for the later groups in the periodic table, which are also well-known characteristics of 3d elements. However, along earlier groups the 4d impurities in graphene show very similar adsorption energies, distances and magnetic moments to the 5d ones, which can be related to the influence of the 4d and 5d lanthanide contraction. Surprisingly, within the manganese group, the total magnetic moment of 3 μB for manganese is reduced to 1 μB for technetium and rhenium. We find that compared with 3d elements, the larger size of the 4d and 5d elements causes a high degree of hybridization with the neighbouring carbon atoms, reducing spin splitting in the d levels. It seems that the magnetic adjustment of graphene could be significantly different if 4d or 5d impurities are used instead of 3d impurities.
Substitutional 4d and 5d impurities in graphene.
Alonso-Lanza, Tomás; Ayuela, Andrés; Aguilera-Granja, Faustino
2016-08-21
We describe the structural and electronic properties of graphene doped with substitutional impurities of 4d and 5d transition metals. The adsorption energies and distances for 4d and 5d metals in graphene show similar trends for the later groups in the periodic table, which are also well-known characteristics of 3d elements. However, along earlier groups the 4d impurities in graphene show very similar adsorption energies, distances and magnetic moments to the 5d ones, which can be related to the influence of the 4d and 5d lanthanide contraction. Surprisingly, within the manganese group, the total magnetic moment of 3 μB for manganese is reduced to 1 μB for technetium and rhenium. We find that compared with 3d elements, the larger size of the 4d and 5d elements causes a high degree of hybridization with the neighbouring carbon atoms, reducing spin splitting in the d levels. It seems that the magnetic adjustment of graphene could be significantly different if 4d or 5d impurities are used instead of 3d impurities. PMID:27439363
Nonequilibrium quantum dynamics in optomechanical systems
NASA Astrophysics Data System (ADS)
Patil, Yogesh Sharad; Cheung, Hil F. H.; Shaffer, Airlia; Wang, Ke; Vengalattore, Mukund
2016-05-01
The thermalization dynamics of isolated quantum systems has so far been explored in the context of cold atomic systems containing a large number of particles and modes. Quantum optomechanical systems offer prospects of studying such dynamics in a qualitatively different regime - with few individually addressable modes amenable to continuous quantum measurement and thermalization times that vastly exceed those observed in cold atomic systems. We have experimentally realized a dynamical continuous phase transition in a quantum compatible nondegenerate mechanical parametric oscillator. This system is formally equivalent to the optical parametric amplifiers whose dynamics have been a subject of intense theoretical study. We experimentally verify its phase diagram and observe nonequilibrium behavior that was only theorized, but never directly observed, in the context of optical parametric amplifiers. We discuss prospects of using nonequilibrium protocols such as quenches in optomechanical systems to amplify weak nonclassical correlations and to realize macroscopic nonclassical states. This work was supported by the DARPA QuASAR program through a Grant from the ARO and the ARO MURI on non-equilibrium manybody dynamics.
Modiri, A; Gu, X; Sawant, A
2014-06-15
Purpose: We present a particle swarm optimization (PSO)-based 4D IMRT planning technique designed for dynamic MLC tracking delivery to lung tumors. The key idea is to utilize the temporal dimension as an additional degree of freedom rather than a constraint in order to achieve improved sparing of organs at risk (OARs). Methods: The target and normal structures were manually contoured on each of the ten phases of a 4DCT scan acquired from a lung SBRT patient who exhibited 1.5cm tumor motion despite the use of abdominal compression. Corresponding ten IMRT plans were generated using the Eclipse treatment planning system. These plans served as initial guess solutions for the PSO algorithm. Fluence weights were optimized over the entire solution space i.e., 10 phases × 12 beams × 166 control points. The size of the solution space motivated our choice of PSO, which is a highly parallelizable stochastic global optimization technique that is well-suited for such large problems. A summed fluence map was created using an in-house B-spline deformable image registration. Each plan was compared with a corresponding, internal target volume (ITV)-based IMRT plan. Results: The PSO 4D IMRT plan yielded comparable PTV coverage and significantly higher dose—sparing for parallel and serial OARs compared to the ITV-based plan. The dose-sparing achieved via PSO-4DIMRT was: lung Dmean = 28%; lung V20 = 90%; spinal cord Dmax = 23%; esophagus Dmax = 31%; heart Dmax = 51%; heart Dmean = 64%. Conclusion: Truly 4D IMRT that uses the temporal dimension as an additional degree of freedom can achieve significant dose sparing of serial and parallel OARs. Given the large solution space, PSO represents an attractive, parallelizable tool to achieve globally optimal solutions for such problems. This work was supported through funding from the National Institutes of Health and Varian Medical Systems. Amit Sawant has research funding from Varian Medical Systems, VisionRT Ltd. and Elekta.
Relations between static and dynamic exponents in nonlinear dynamical systems
NASA Astrophysics Data System (ADS)
Badii, R.; Broggi, G.
1990-01-01
The rules governing the evolution of nonlinear dynamical systems are systematically detected by constructing a hierarchical tree of symbol sequences. Relations between local partial dimensions and Lyapunov exponents are obtained from equations for the probabilities of symbol sequences on the logic tree. These relations are nonlinear and involve an open hierarchy of equations, which shows that the dimension spectrum f(α) cannot be obtained in closed form from the sole knowledge of the local Lyapunov exponents.
Similarity Metrics for Closed Loop Dynamic Systems
NASA Technical Reports Server (NTRS)
Whorton, Mark S.; Yang, Lee C.; Bedrossian, Naz; Hall, Robert A.
2008-01-01
To what extent and in what ways can two closed-loop dynamic systems be said to be "similar?" This question arises in a wide range of dynamic systems modeling and control system design applications. For example, bounds on error models are fundamental to the controller optimization with modern control design methods. Metrics such as the structured singular value are direct measures of the degree to which properties such as stability or performance are maintained in the presence of specified uncertainties or variations in the plant model. Similarly, controls-related areas such as system identification, model reduction, and experimental model validation employ measures of similarity between multiple realizations of a dynamic system. Each area has its tools and approaches, with each tool more or less suited for one application or the other. Similarity in the context of closed-loop model validation via flight test is subtly different from error measures in the typical controls oriented application. Whereas similarity in a robust control context relates to plant variation and the attendant affect on stability and performance, in this context similarity metrics are sought that assess the relevance of a dynamic system test for the purpose of validating the stability and performance of a "similar" dynamic system. Similarity in the context of system identification is much more relevant than are robust control analogies in that errors between one dynamic system (the test article) and another (the nominal "design" model) are sought for the purpose of bounding the validity of a model for control design and analysis. Yet system identification typically involves open-loop plant models which are independent of the control system (with the exception of limited developments in closed-loop system identification which is nonetheless focused on obtaining open-loop plant models from closed-loop data). Moreover the objectives of system identification are not the same as a flight test and
Parallel Infrastructure Modeling and Inversion Module for E4D
2014-10-09
Electrical resistivity tomography ERT is a method of imaging the electrical conductivity of the subsurface. Electrical conductivity is a useful metric for understanding the subsurface because it is governed by geomechanical and geochemical properties that drive subsurface systems. ERT works by injecting current into the subsurface across a pair of electrodes, and measuring the corresponding electrical potential response across another pair of electrodes. Many such measurements are strategically taken across an array of electrodes to produce an ERT data set. These data are then processed through a computationally demanding process known as inversion to produce an image of the subsurface conductivity structure that gave rise to the measurements. Data can be inverted to provide 2D images, 3D images, or in the case of time-lapse 3D imaging, 4D images. ERT is generally not well suited for environments with buried electrically conductive infrastructure such as pipes, tanks, or well casings, because these features tend to dominate and degrade ERT images. This reduces or eliminates the utility of ERT imaging where it would otherwise be highly useful for, for example, imaging fluid migration from leaking pipes, imaging soil contamination beneath leaking subusurface tanks, and monitoring contaminant migration in locations with dense network of metal cased monitoring wells. The location and dimension of buried metallic infrastructure is often known. If so, then the effects of the infrastructure can be explicitly modeled within the ERT imaging algorithm, and thereby removed from the corresponding ERT image. However,there are a number of obstacles limiting this application. 1) Metallic infrastructure cannot be accurately modeled with standard codes because of the large contrast in conductivity between the metal and host material. 2) Modeling infrastructure in true dimension requires the computational mesh to be highly refined near the metal inclusions, which increases
Dynamic stability experiment of Maglev systems
Cai, Y.; Chen, S.S.; Zhu, S.; Rote, D.M.
1995-12-31
This paper presents dynamic stability experiments on maglev systems and compares with predictions calculated by a nonlinear dynamic computer code. Instabilities of an electrodynamic system (EDS)-type vehicle model were obtained from both experimental observations and computer simulations for a five-degree-of-freedom maglev vehicle moving on a guideway consisting of double L-shaped aluminum segments attached to a rotating wheel. The experimental and theoretical analyses developed in this study identify basic stability characteristics and future research needs of maglev systems.
Solar dynamic space power system heat rejection
NASA Technical Reports Server (NTRS)
Carlson, A. W.; Gustafson, E.; Mclallin, K. L.
1986-01-01
A radiator system concept is described that meets the heat rejection requirements of the NASA Space Station solar dynamic power modules. The heat pipe radiator is a high-reliability, high-performance approach that is capable of erection in space and is maintainable on orbit. Results are present of trade studies that compare the radiator system area and weight estimates for candidate advanced high performance heat pipes. The results indicate the advantages of the dual-slot heat pipe radiator for high temperature applications as well as its weight-reduction potential over the range of temperatures to be encountered in the solar dynamic heat rejection systems.
Dimensionality reduction of dynamical systems with parameters
NASA Astrophysics Data System (ADS)
Welshman, Ch.; Brooke, J.
2013-01-01
We describe a method for reproducing the dynamical behaviour observed in systems of very high dimension in a state space of much lower dimension. The method is designed for systems where the solution evolves onto an attractor of dimension m which is much lower than that of the state space of the full system, n. Whitney's embedding theorem guarantees that the attractor can be embedded in a space of dimension d = 2m+1. We describe how such methods can be extended to reproducing the vector field on the attractor so that the dynamics of a parameterized family of attractors can be explored in the low dimensional space Rd.
Efficient dynamic models of tensegrity systems
NASA Astrophysics Data System (ADS)
Skelton, Robert
2009-03-01
The multi-body dynamics appear in a new form, as a matrix differential equation, rather than the traditional vector differential equation. The model has a constant mass matrix, and the equations are non-minimal. A specific focus of this paper is tensegrity systems. A tensegrity system requires prestress for stabilization of the configuration of rigid bodies and tensile members. This paper provides an efficient model for both static and dynamic behavior of such systems, specialized for the case when the rigid bodies are axi-symmetric rods.
Biomechanics of Posterior Dynamic Stabilization Systems
Erbulut, D. U.; Zafarparandeh, I.; Ozer, A. F.; Goel, V. K.
2013-01-01
Spinal rigid instrumentations have been used to fuse and stabilize spinal segments as a surgical treatment for various spinal disorders to date. This technology provides immediate stability after surgery until the natural fusion mass develops. At present, rigid fixation is the current gold standard in surgical treatment of chronic back pain spinal disorders. However, such systems have several drawbacks such as higher mechanical stress on the adjacent segment, leading to long-term degenerative changes and hypermobility that often necessitate additional fusion surgery. Dynamic stabilization systems have been suggested to address adjacent segment degeneration, which is considered to be a fusion-associated phenomenon. Dynamic stabilization systems are designed to preserve segmental stability, to keep the treated segment mobile, and to reduce or eliminate degenerative effects on adjacent segments. This paper aimed to describe the biomechanical aspect of dynamic stabilization systems as an alternative treatment to fusion for certain patients. PMID:23606975
A dynamic dosimetry system for prostate brachytherapy
NASA Astrophysics Data System (ADS)
Kuo, Nathanael; Dehghan, Ehsan; Deguet, Anton; Song, Danny Y.; Prince, Jerry L.; Lee, Junghoon
2013-03-01
The lack of dynamic dosimetry tools for permanent prostate brachytherapy causes otherwise avoidable problems in prostate cancer patient care. The goal of this work is to satisfy this need in a readily adoptable manner. Using the ubiquitous ultrasound scanner and mobile non-isocentric C-arm, we show that dynamic dosimetry is now possible with only the addition of an arbitrarily configured marker-based fiducial. Not only is the system easily configured from accessible hardware, but it is also simple and convenient, requiring little training from technicians. Furthermore, the proposed system is built upon robust algorithms of seed segmentation, fiducial detection, seed reconstruction, and image registration. All individual steps of the pipeline have been thoroughly tested, and the system as a whole has been validated on a study of 25 patients. The system has shown excellent results of accurately computing dose, and does so with minimal manual intervention, therefore showing promise for widespread adoption of dynamic dosimetry.
Stirling Convertor System Dynamic Model Developed
NASA Technical Reports Server (NTRS)
Lewandowski, Edward J.; Regan, Timothy F.
2005-01-01
Free-piston Stirling convertors are being developed for potential use on NASA exploration missions. In support of this effort, the NASA Glenn Research Center has developed the Stirling convertor System Dynamic Model (SDM). The SDM models the Stirling cycle thermodynamics; heat flow; gas, mechanical, and mounting dynamics; the linear alternator; and the controller. The SDM s scope extends from the thermal energy input to thermal, mechanical, and electrical energy output, allowing one to study complex system interactions among subsystems. Thermal, mechanical, fluid, magnetic, and electrical subsystems can be studied in one model. The SDM is a nonlinear time-domain model containing sub-cycle dynamics, which simulates transient and dynamic phenomena that other models cannot. The entire range of convertor operation is modeled, from startup to full-power conditions.
Reaction dynamics in polyatomic molecular systems
Miller, W.H.
1993-12-01
The goal of this program is the development of theoretical methods and models for describing the dynamics of chemical reactions, with specific interest for application to polyatomic molecular systems of special interest and relevance. There is interest in developing the most rigorous possible theoretical approaches and also in more approximate treatments that are more readily applicable to complex systems.
Modelling Information System Dynamics: A Perspective.
ERIC Educational Resources Information Center
Oswitch, Pauline
1983-01-01
Describes British Library's work on Systems Dynamics, a set of techniques for building simulation models based on analysis of information feedback loops. Highlights include macro-simulation modelling activities of social science disciplines, systems analyses and models of information retrieval processes and library services, policy models, and…
NASA Astrophysics Data System (ADS)
Stibal, M.; Bælum, J.; Holben, W. E.; Jacobsen, C. S.
2012-12-01
The surface of the Greenland ice sheet (GrIS) harbours a diverse community of heterotrophic microorganisms. Organic compounds of anthropogenic origin, including pesticides, are deposited on the GrIS; however, the fate of these compounds in the ice is currently unknown. In this study we determine the potential of the microbial community from the surface of the GrIS to mineralise the pesticide 2,4-dichlorophenoxyacetic acid (2,4-D). It is one of the most easily degraded compounds among the phenoxyacetic acid pesticides, and the ability to mineralise 2,4-D has been found to be widespread in microbial communities around the globe. Functional genes involved in the degradation pathway have also been characterised. Thus, 2,4-D represents a very suitable model compound to use in order to gain an insight into pollutant degradation dynamics in the rapidly changing Arctic region. We collected surface ice cores on the GrIS and incubated them for up to 529 days in microcosms simulating in situ conditions. We measured mineralisation of side-chain- and ring-labelled 14C-2,4-D in the samples and performed quantitative PCR targeting the tfdA gene, encoding an enzyme catalysing the first step in the degradation pathway of 2,4-D, in the DNA extracted from the ice after the experiments. We show that the microbial community on the surface of the GrIS is of low diversity, but contains microbes capable of degrading 2,4-D. The low diversity of the community and the similarity of the detected clones to those from other icy environment clones suggest that the bacterial community on the GrIS is selected from a pool of propagules deposited on the surface of the ice sheet, based on the level of adaptation to the conditions in the surface ice. The 2,4-D degraders are likely present in very low numbers, and they can mineralise 2,4-D at a rate of up to 1 nmol per m2 per day, equivalent to ~26 ng C m-2 d-1. We contend that the surface of the GrIS should not be considered to be a mere reservoir of
Dynamics, stability, and control of maglev systems
Cai, Y.; Chen, S.S.; Rote, D.M.; Coffey, H.T.
1993-01-01
The dynamic response of maglev systems is important in several respects: Safety and ride quality, guideway design, and system costs. The dynamic response of vehicles is the key element in the determination of ride quality, and vehicle stability is one of the important elements relative to safety. To design a proper guideway that provides acceptable ride quality in the stable region, the vehicle dynamics must be understood. The trade-off between guideway smoothness and the levitation and control systems must be considered if maglev systems are to be economically feasible. This paper is a summary of our previous work on dynamics, stability and control of maglev systems. First of all, the importance of dynamics of vehicle/guideway of maglev systems is discussed. Emphasis is placed on the modeling vehicle/guideway interactions of maglev systems with a multicar, or multiload vehicle traversing on a single or double-span flexible guideway. Coupled effects of vehicle/guideway interactions in wide range of vehicle speeds with various vehicle and guideway parameters for maglev systems are investigated. Secondly, the alternative control designs of maglev vehicle suspension systems are investigated in this study to achieve safe, stable operation and acceptable ride comfort requires some form of vehicle motion control. Active and semi-active control law designs are introduced into primary and secondary suspensions of maglev vehicles. Finally, this paper discusses the stability of maglev systems based on experimental data, scoping calculations, and simple mathematical models. Divergence and flutter are obtained for coupled vibration of a three-degree-of-freedom maglev vehicle on a guideway consisting of double L-shaped aluminum segments. The theory and analysis developed in this study provides basic stability characteristics and identifies future research needs for maglev systems.
Dynamics, stability, and control of maglev systems
Cai, Y.; Chen, S.S.; Rote, D.M.; Coffey, H.T.
1993-06-01
The dynamic response of maglev systems is important in several respects: Safety and ride quality, guideway design, and system costs. The dynamic response of vehicles is the key element in the determination of ride quality, and vehicle stability is one of the important elements relative to safety. To design a proper guideway that provides acceptable ride quality in the stable region, the vehicle dynamics must be understood. The trade-off between guideway smoothness and the levitation and control systems must be considered if maglev systems are to be economically feasible. This paper is a summary of our previous work on dynamics, stability and control of maglev systems. First of all, the importance of dynamics of vehicle/guideway of maglev systems is discussed. Emphasis is placed on the modeling vehicle/guideway interactions of maglev systems with a multicar, or multiload vehicle traversing on a single or double-span flexible guideway. Coupled effects of vehicle/guideway interactions in wide range of vehicle speeds with various vehicle and guideway parameters for maglev systems are investigated. Secondly, the alternative control designs of maglev vehicle suspension systems are investigated in this study to achieve safe, stable operation and acceptable ride comfort requires some form of vehicle motion control. Active and semi-active control law designs are introduced into primary and secondary suspensions of maglev vehicles. Finally, this paper discusses the stability of maglev systems based on experimental data, scoping calculations, and simple mathematical models. Divergence and flutter are obtained for coupled vibration of a three-degree-of-freedom maglev vehicle on a guideway consisting of double L-shaped aluminum segments. The theory and analysis developed in this study provides basic stability characteristics and identifies future research needs for maglev systems.
Solar dynamic power system definition study
NASA Technical Reports Server (NTRS)
Wallin, Wayne E.; Friefeld, Jerry M.
1988-01-01
The solar dynamic power system design and analysis study compared Brayton, alkali-metal Rankine, and free-piston Stirling cycles with silicon planar and GaAs concentrator photovoltaic power systems for application to missions beyond the Phase 2 Space Station level of technology for all power systems. Conceptual designs for Brayton and Stirling power systems were developed for 35 kWe and 7 kWe power levels. All power systems were designed for 7-year end-of-life conditions in low Earth orbit. LiF was selected for thermal energy storage for the solar dynamic systems. Results indicate that the Stirling cycle systems have the highest performance (lowest weight and area) followed by the Brayton cycle, with photovoltaic systems considerably lower in performance. For example, based on the performance assumptions used, the planar silicon power system weight was 55 to 75 percent higher than for the Stirling system. A technology program was developed to address areas wherein significant performance improvements could be realized relative to the current state-of-the-art as represented by Space Station. In addition, a preliminary evaluation of hardenability potential found that solar dynamic systems can be hardened beyond the hardness inherent in the conceptual designs of this study.
Near Identifiability of Dynamical Systems
NASA Technical Reports Server (NTRS)
Hadaegh, F. Y.; Bekey, G. A.
1987-01-01
Concepts regarding approximate mathematical models treated rigorously. Paper presents new results in analysis of structural identifiability, equivalence, and near equivalence between mathematical models and physical processes they represent. Helps establish rigorous mathematical basis for concepts related to structural identifiability and equivalence revealing fundamental requirements, tacit assumptions, and sources of error. "Structural identifiability," as used by workers in this field, loosely translates as meaning ability to specify unique mathematical model and set of model parameters that accurately predict behavior of corresponding physical system.
Evaluation of a 4D cone-beam CT reconstruction approach using a simulation framework.
Hartl, Alexander; Yaniv, Ziv
2009-01-01
Current image-guided navigation systems for thoracic abdominal interventions utilize three dimensional (3D) images acquired at breath-hold. As a result they can only provide guidance at a specific point in the respiratory cycle. The intervention is thus performed in a gated manner, with the physician advancing only when the patient is at the same respiratory cycle in which the 3D image was acquired. To enable a more continuous workflow we propose to use 4D image data. We describe an approach to constructing a set of 4D images from a diagnostic CT acquired at breath-hold and a set of intraoperative cone-beam CT (CBCT) projection images acquired while the patient is freely breathing. Our approach is based on an initial reconstruction of a gated 4D CBCT data set. The 3D CBCT images for each respiratory phase are then non-rigidly registered to the diagnostic CT data. Finally the diagnostic CT is deformed based on the registration results, providing a 4D data set with sufficient quality for navigation purposes. In this work we evaluate the proposed reconstruction approach using a simulation framework. A 3D CBCT dataset of an anthropomorphic phantom is deformed using internal motion data acquired from an animal model to create a ground truth 4D CBCT image. Simulated projection images are then created from the 4D image and the known CBCT scan parameters. Finally, the original 3D CBCT and the simulated X-ray images are used as input to our reconstruction method. The resulting 4D data set is then compared to the known ground truth by normalized cross correlation(NCC). We show that the deformed diagnostic CTs are of better quality than the gated reconstructions with a mean NCC value of 0.94 versus a mean 0.81 for the reconstructions. PMID:19964143
Mixing 4D-Equipped and Unequipped Aircraft in the Terminal Area
NASA Technical Reports Server (NTRS)
Tobias, L.; Erzberger, H.; Lee, H. Q.; Obrien, P. J.
1984-01-01
On-board 4D guidance systems, which predict and control the touchdown time of an aircraft to an accuracy of a few seconds throughout the descent, were developed and demonstrated in several flight test programs. However, in addition to refinements of the on board system, two important issues still need to be considered. First, in order to make effective use of these on-board systems, it is necessary to understand and develop the interactions of the airborne and air traffic control (ATC) system in the proposed advanced environment. Unless the total system is understood, the advanced on-board system may prove unusable from an ATC standpoint. Second, in planning for a future system in which all aircraft are 4D equipped, it is necessary to confront the transition situation in which some percentage of traffic must still be handled by conventional means. In terms of 4D, this means that some traffic must still be given radar vectors and speed clearances (that is, be spaced by conventional distance separation techniques), while the 4D-equipped aircraft need to be issued time assignments. These apparent differences are reconciled and efficient ATC operation is developed.
Soil matrix and macropore biodegradation of 2,4-D
Pivetz, B.E.; Steenhuis, T.S.
1995-07-01
Preferential flow of pesticides in macropores can lead to decreased travel times through the vadose zone and increased groundwater contamination. Macropores, however, may present a favorable environment for biodegradation because of greater oxygen, nutrient, and substrate supply, and higher microbial populations in earthworm burrows, compared to the soil matrix. The biodegradation of 2,4-dichlorophenoxyacetic acid (2,4-D) was measured in macropores and soil matrix of packed soil columns (7.0-cm diam., 10-cm length) and undisturbed cores contained as well-defined artificial macropore and the undisturbed cores contained earthworm-burrow macropores. A 50 {mu}g/L 2,4-D solution was continuously applied to the unsaturated soil surface and breakthrough curves (BTCs) indicating pesticide loss in the effluent were obtained from the soil matrix and macropore flow paths. Biodegradation rates were calculated separately for each flow path by comparing the BTCs to BTCs representing abiotic conditions, and dividing the 2,4-D loss by the travel time through each flow path. The biodegradation rates increased with time in both flow paths, and the final biodegradation rate in the macropore region surpassed that of the matrix, presumably because of increased microbial populations in the macropore. Complete loss of the 2,4-D in both flow paths was observed after continuous application of 2,4-D for 400 h, with maximum column-averaged 2,4-D loss rates of 0.879 {mu}g/(L h) in the matrix and 1.073 {mu}g/(L h) in the macropore. Biodegradation of 2,4-D was also observed in the macropore and matrix regions of the undisturbed soil cores. 19 refs., 7 figs., 2 tabs.
Human systems dynamics: Toward a computational model
NASA Astrophysics Data System (ADS)
Eoyang, Glenda H.
2012-09-01
A robust and reliable computational model of complex human systems dynamics could support advancements in theory and practice for social systems at all levels, from intrapersonal experience to global politics and economics. Models of human interactions have evolved from traditional, Newtonian systems assumptions, which served a variety of practical and theoretical needs of the past. Another class of models has been inspired and informed by models and methods from nonlinear dynamics, chaos, and complexity science. None of the existing models, however, is able to represent the open, high dimension, and nonlinear self-organizing dynamics of social systems. An effective model will represent interactions at multiple levels to generate emergent patterns of social and political life of individuals and groups. Existing models and modeling methods are considered and assessed against characteristic pattern-forming processes in observed and experienced phenomena of human systems. A conceptual model, CDE Model, based on the conditions for self-organizing in human systems, is explored as an alternative to existing models and methods. While the new model overcomes the limitations of previous models, it also provides an explanatory base and foundation for prospective analysis to inform real-time meaning making and action taking in response to complex conditions in the real world. An invitation is extended to readers to engage in developing a computational model that incorporates the assumptions, meta-variables, and relationships of this open, high dimension, and nonlinear conceptual model of the complex dynamics of human systems.
Practical Power System Aggregation Considering Dynamic Loads
NASA Astrophysics Data System (ADS)
Yamagishi, Yoshio; Komami, Shintaro
This paper presents a practical method for creating power system equivalents that can be used in power system stability analysis. The proposed method uses three branches to connect the boundary bus, generator, and load. The method is suitable to consider reactance from the boundary bus to the load for power system stability studies using a dynamic load model. Furthermore, this paper presents a practical procedure to determine the parameters of the aggregated generator, including control devices such as excitation systems, PSS (power system stabilizer), and speed governors. The quality of the various aggregation models is verified using power system stability simulations.
Dynamics Explorer Science Data Processing System
NASA Technical Reports Server (NTRS)
Smith, P. H.; Freeman, C. H.; Hoffman, R. A.
1981-01-01
The Dynamics Explorer project has acquired the ground data processing system from the Atmosphere Explorer project to provide a central computer facility for the data processing, data management and data analysis activities of the investigators. Access to this system is via remote terminals at the investigators' facilities, which provide ready access to the data sets derived from groups of instruments on both spacecraft. The original system has been upgraded with both new hardware and enhanced software systems. These new systems include color and grey scale graphics terminals, an augmentation computer, micrographics facility, a versatile data base with a directory and data management system, and graphics display software packages.
Stirling Engine Dynamic System Modeling
NASA Technical Reports Server (NTRS)
Nakis, Christopher G.
2004-01-01
The Thermo-Mechanical systems branch at the Glenn Research Center focuses a large amount time on Stirling engines. These engines will be used on missions where solar power is inefficient, especially in deep space. I work with Tim Regan and Ed Lewandowski who are currently developing and validating a mathematical model for the Stirling engines. This model incorporates all aspects of the system including, mechanical, electrical and thermodynamic components. Modeling is done through Simplorer, a program capable of running simulations of the model. Once created and then proven to be accurate, a model is used for developing new ideas for engine design. My largest specific project involves varying key parameters in the model and quantifying the results. This can all be done relatively trouble-free with the help of Simplorer. Once the model is complete, Simplorer will do all the necessary calculations. The more complicated part of this project is determining which parameters to vary. Finding key parameters depends on the potential for a value to be independently altered in the design. For example, a change in one dimension may lead to a proportional change to the rest of the model, and no real progress is made. Also, the ability for a changed value to have a substantial impact on the outputs of the system is important. Results will be condensed into graphs and tables with the purpose of better communication and understanding of the data. With the changing of these parameters, a more optimal design can be created without having to purchase or build any models. Also, hours and hours of results can be simulated in minutes. In the long run, using mathematical models can save time and money. Along with this project, I have many other smaller assignments throughout the summer. My main goal is to assist in the processes of model development, validation and testing.
Dynamical entropy for systems with stochastic perturbation
Ostruszka; Pakonski; Slomczynski; Zyczkowski
2000-08-01
Dynamics of deterministic systems perturbed by random additive noise is characterized quantitatively. Since for such systems the Kolmogorov-Sinai (KS) entropy diverges if the diameter of the partition tends to zero, we analyze the difference between the total entropy of a noisy system and the entropy of the noise itself. We show that this quantity is finite and non-negative and we call it the dynamical entropy of the noisy system. In the weak noise limit this quantity is conjectured to tend to the KS entropy of the deterministic system. In particular, we consider one-dimensional systems with noise described by a finite-dimensional kernel for which the Frobenius-Perron operator can be represented by a finite matrix.
Energy efficiency of a dynamic glazing system
Lollini, R.; Danza, L.; Meroni, I.
2010-04-15
The reduction of air-conditioning energy consumptions is one of the main indicators to act on when improving the energy efficiency in buildings. In the case of advanced technological buildings, a meaningful contribution to the thermal loads and the energy consumptions reduction could depend on the correct configuration and management of the envelope systems. In recent years, the architectural trend toward highly transparent all-glass buildings presents a unique challenge and opportunity to advance the market for emerging, smart, dynamic window and dimmable daylighting control technologies (). A prototype dynamic glazing system was developed and tested at ITC-CNR; it is aimed at actively responding to the external environmental loads. Both an experimental campaign and analyses by theoretical models were carried out, aimed at evaluating the possible configurations depending on different weather conditions in several possible places. Therefore, the analytical models of the building-plant system were defined by using a dynamic energy simulation software (EnergyPlus). The variables that determine the system performance, also influenced by the boundary conditions, were analysed, such as U- and g-value; they concern both the morphology of the envelope system, such as dimensions, shading and glazing type, gap airflow thickness, in-gap airflow rate, and management, in terms of control algorithm parameters tuning fan and shading systems, as a function of the weather conditions. The configuration able to provide the best performances was finally identified by also assessing such performances, integrating the dynamic system in several building types and under different weather conditions. The dynamic envelope system prototype has become a commercial product with some applications in facade systems, curtain walls and windows. The paper describes the methodological approach to prototype development and the main results obtained, including simulations of possible applications on
Dynamic-Type Ice Thermal Storage Systems
NASA Astrophysics Data System (ADS)
Ohira, Akiyoshi
This paper deals with reviews for research and development of a dynamic-type ice thermal storage system. This system has three main features. First, the ice thermal storage tank and the ice generator are separate. Second, ice is transported to the tank from the ice generator by water or air. Third, the ice making and melting processes are operated at the same time. Outlet water temperature from the dynamic-type ice thermal storage tank remains low for a longer time. In this paper, dynamic-Type ice thermal storage systems are divided into three parts: the ice making part, the ice transport part, and the cold energy release part. Each part is reviewed separately.
Geometric phases in discrete dynamical systems
NASA Astrophysics Data System (ADS)
Cartwright, Julyan H. E.; Piro, Nicolas; Piro, Oreste; Tuval, Idan
2016-10-01
In order to study the behaviour of discrete dynamical systems under adiabatic cyclic variations of their parameters, we consider discrete versions of adiabatically-rotated rotators. Parallelling the studies in continuous systems, we generalize the concept of geometric phase to discrete dynamics and investigate its presence in these rotators. For the rotated sine circle map, we demonstrate an analytical relationship between the geometric phase and the rotation number of the system. For the discrete version of the rotated rotator considered by Berry, the rotated standard map, we further explore this connection as well as the role of the geometric phase at the onset of chaos. Further into the chaotic regime, we show that the geometric phase is also related to the diffusive behaviour of the dynamical variables and the Lyapunov exponent.
Uncertain dynamical systems: A differential game approach
NASA Technical Reports Server (NTRS)
Gutman, S.
1976-01-01
A class of dynamical systems in a conflict situation is formulated and discussed, and the formulation is applied to the study of an important class of systems in the presence of uncertainty. The uncertainty is deterministic and the only assumption is that its value belongs to a known compact set. Asymptotic stability is fully discussed with application to variable structure and model reference control systems.
Spectral monitoring of power system dynamic performances
Ostojic, D.R. . School of Electrical Engineering)
1993-05-01
This paper presents a nonparametric method for the direct spectral analysis of power system dynamic performances after a disturbance. The developed monitoring technique uses a signal processing procedure for determining the time-frequency distribution of energy of electromechanical oscillations. The quantities obtained from this distribution enable a robust monitoring of frequency, damping, energy content and interaction mechanisms of system oscillatory modes. The performances of the proposed method are studied on the example of 10-machine, 39-bus test system.
Nonlinear Dynamics, Chaotic and Complex Systems
NASA Astrophysics Data System (ADS)
Infeld, E.; Zelazny, R.; Galkowski, A.
2011-04-01
Part I. Dynamic Systems Bifurcation Theory and Chaos: 1. Chaos in random dynamical systems V. M. Gunldach; 2. Controlling chaos using embedded unstable periodic orbits: the problem of optimal periodic orbits B. R. Hunt and E. Ott; 3. Chaotic tracer dynamics in open hydrodynamical flows G. Karolyi, A. Pentek, T. Tel and Z. Toroczkai; 4. Homoclinic chaos L. P. Shilnikov; Part II. Spatially Extended Systems: 5. Hydrodynamics of relativistic probability flows I. Bialynicki-Birula; 6. Waves in ionic reaction-diffusion-migration systems P. Hasal, V. Nevoral, I. Schreiber, H. Sevcikova, D. Snita, and M. Marek; 7. Anomalous scaling in turbulence: a field theoretical approach V. Lvov and I. Procaccia; 8. Abelian sandpile cellular automata M. Markosova; 9. Transport in an incompletely chaotic magnetic field F. Spineanu; Part III. Dynamical Chaos Quantum Physics and Foundations Of Statistical Mechanics: 10. Non-equilibrium statistical mechanics and ergodic theory L. A. Bunimovich; 11. Pseudochaos in statistical physics B. Chirikov; 12. Foundations of non-equilibrium statistical mechanics J. P. Dougherty; 13. Thermomechanical particle simulations W. G. Hoover, H. A. Posch, C. H. Dellago, O. Kum, C. G. Hoover, A. J. De Groot and B. L. Holian; 14. Quantum dynamics on a Markov background and irreversibility B. Pavlov; 15. Time chaos and the laws of nature I. Prigogine and D. J. Driebe; 16. Evolutionary Q and cognitive systems: dynamic entropies and predictability of evolutionary processes W. Ebeling; 17. Spatiotemporal chaos information processing in neural networks H. Szu; 18. Phase transitions and learning in neural networks C. Van den Broeck; 19. Synthesis of chaos A. Vanecek and S. Celikovsky; 20. Computational complexity of continuous problems H. Wozniakowski; Part IV. Complex Systems As An Interface Between Natural Sciences and Environmental Social and Economic Sciences: 21. Stochastic differential geometry in finance studies V. G. Makhankov; Part V. Conference Banquet
Tai, A; Ahunbay, E; Li, X
2014-06-01
Purpose: To develop a method to create ventilation CTs from daily 4D CTs or 4D KV conebeam CTs (4DCBCT) acquired during image-guided radiation therapy (IGRT) for thoracic tumors, and to explore the potential for using the ventilation CTs as a means for early detection of lung injury during radiation treatment. Methods: 4DCT acquired using an in-room CT (CTVision, Siemens) and 4DCBCT acquired using the X-ray Volume Imaging (XVI) system (Infinity, Elekta) for representative lung cancer patients were analyzed. These 4D data sets were sorted into 10 phase images. A newly-available deformable image registration tool (ADMIRE, Elekta) is used to deform the phase images at the end of exhale (EE) to the phase images at the end of inhale (EI). The lung volumes at EI and EE were carefully contoured using an intensity-based auto-contour tool and then manually edited. The ventilation images were calculated from the variations of CT numbers of those voxels masked by the lung contour at EI between the registered phase images. The deformable image registration is also performed between the daily 4D images and planning 4DCT, and the resulting deformable field vector (DFV) is used to deform the planning doses to the daily images by an in-house Matlab program. Results: The ventilation images were successfully created. The tide volumes calculated using the ventilation images agree with those measured through volume difference of contours at EE and EI, indicating the accuracy of ventilation images. The association between the delivered doses and the change of lung ventilation from the daily ventilation CTs is identified. Conclusions: A method to create the ventilation CT using daily 4DCTs or 4D KV conebeam CTs was developed and demonstrated.
NASA Astrophysics Data System (ADS)
Bouttier, Pierre-Antoine; Brankart, Jean-Michel; Candille, Guillem; Vidard, Arthur; Blayo, Eric; Verron, Jacques; Brasseur, Pierre
2015-04-01
In this project, the response of a variational data assimilation system based on NEMO and its linear tangent and adjoint model is investigated using a 4DVAR algorithm into a North-Atlantic model at eddy-permitting resolution. The assimilated data consist of Jason-2 and SARAL/AltiKA dataset collected during the 2013-2014 period. The main objective is to explore the robustness of the 4DVAR algorithm in the context of a realistic turbulent oceanic circulation at mid-latitude constrained by multi-satellite altimetry missions. This work relies on two previous studies. First, a study with similar objectives was performed based on academic double-gyre turbulent model and synthetic SARAL/AltiKA data, using the same DA experimental framework. Its main goal was to investigate the impact of turbulence on variational DA methods performance. The comparison with this previous work will bring to light the methodological and physical issues encountered by variational DA algorithms in a realistic context at similar, eddy-permitting spatial resolution. We also have demonstrated how a dataset mimicking future SWOT observations improves 4DVAR incremental performances at eddy-permitting resolution. Then, in the context of the OSTST and FP7 SANGOMA projects, an ensemble DA experiment based on the same model and observational datasets has been realized (see poster by Brasseur et al.). This work offers the opportunity to compare efficiency, pros and cons of both DA methods in the context of KA-band altimetric data, at spatial resolution commonly used today for research and operational applications. In this poster we will present the validation plan proposed to evaluate the skill of variational experiment vs. ensemble assimilation experiments covering the same period using independent observations (e.g. from Cryosat-2 mission).
New C4D Sensor with a Simulated Inductor
Lyu, Yingchao; Ji, Haifeng; Yang, Shijie; Huang, Zhiyao; Wang, Baoliang; Li, Haiqing
2016-01-01
A new capacitively coupled contactless conductivity detection (C4D) sensor with an improved simulated inductor is developed in this work. The improved simulated inductor is designed on the basis of the Riordan-type floating simulated inductor. With the improved simulated inductor, the negative influence of the coupling capacitances is overcome and the conductivity measurement is implemented by the series resonance principle. The conductivity measurement experiments are carried out in three pipes with different inner diameters of 3.0 mm, 4.6 mm and 6.4 mm, respectively. The experimental results show that the designs of the new C4D sensor and the improved simulated inductor are successful. The maximum relative error of the conductivity measurement is less than 5%. Compared with the C4D sensors using practical inductors, the measurement accuracy of the new C4D sensor is comparable. The research results also indicate that the adjustability of a simulated inductor can reduce the requirement for the AC source and guarantee the interchangeableness. Meanwhile, it is recommended that making the potential of one terminal of a simulated inductor stable is beneficial to the running stability. Furthermore, this work indirectly verifies the possibility and feasibility of the miniaturization of the C4D sensor by using the simulated inductor technique and lays a good foundation for future research work. PMID:26828493
Quantum Simulation for Open-System Dynamics
NASA Astrophysics Data System (ADS)
Wang, Dong-Sheng; de Oliveira, Marcos Cesar; Berry, Dominic; Sanders, Barry
2013-03-01
Simulations are essential for predicting and explaining properties of physical and mathematical systems yet so far have been restricted to classical and closed quantum systems. Although forays have been made into open-system quantum simulation, the strict algorithmic aspect has not been explored yet is necessary to account fully for resource consumption to deliver bounded-error answers to computational questions. An open-system quantum simulator would encompass classical and closed-system simulation and also solve outstanding problems concerning, e.g. dynamical phase transitions in non-equilibrium systems, establishing long-range order via dissipation, verifying the simulatability of open-system dynamics on a quantum Turing machine. We construct an efficient autonomous algorithm for designing an efficient quantum circuit to simulate many-body open-system dynamics described by a local Hamiltonian plus decoherence due to separate baths for each particle. The execution time and number of gates for the quantum simulator both scale polynomially with the system size. DSW funded by USARO. MCO funded by AITF and Brazilian agencies CNPq and FAPESP through Instituto Nacional de Ciencia e Tecnologia-Informacao Quantica (INCT-IQ). DWB funded by ARC Future Fellowship (FT100100761). BCS funded by AITF, CIFAR, NSERC and USARO.
Graph-based retrospective 4D image construction from free-breathing MRI slice acquisitions
NASA Astrophysics Data System (ADS)
Tong, Yubing; Udupa, Jayaram K.; Ciesielski, Krzysztof C.; McDonough, Joseph M.; Mong, Andrew; Campbell, Robert M.
2014-03-01
4D or dynamic imaging of the thorax has many potential applications [1, 2]. CT and MRI offer sufficient speed to acquire motion information via 4D imaging. However they have different constraints and requirements. For both modalities both prospective and retrospective respiratory gating and tracking techniques have been developed [3, 4]. For pediatric imaging, x-ray radiation becomes a primary concern and MRI remains as the de facto choice. The pediatric subjects we deal with often suffer from extreme malformations of their chest wall, diaphragm, and/or spine, as such patient cooperation needed by some of the gating and tracking techniques are difficult to realize without causing patient discomfort. Moreover, we are interested in the mechanical function of their thorax in its natural form in tidal breathing. Therefore free-breathing MRI acquisition is the ideal modality of imaging for these patients. In our set up, for each coronal (or sagittal) slice position, slice images are acquired at a rate of about 200-300 ms/slice over several natural breathing cycles. This produces typically several thousands of slices which contain both the anatomic and dynamic information. However, it is not trivial to form a consistent and well defined 4D volume from these data. In this paper, we present a novel graph-based combinatorial optimization solution for constructing the best possible 4D scene from such data entirely in the digital domain. Our proposed method is purely image-based and does not need breath holding or any external surrogates or instruments to record respiratory motion or tidal volume. Both adult and children patients' data are used to illustrate the performance of the proposed method. Experimental results show that the reconstructed 4D scenes are smooth and consistent spatially and temporally, agreeing with known shape and motion of the lungs.
Global dynamic modeling of a transmission system
NASA Technical Reports Server (NTRS)
Choy, F. K.; Qian, W.
1993-01-01
The work performed on global dynamic simulation and noise correlation of gear transmission systems at the University of Akron is outlined. The objective is to develop a comprehensive procedure to simulate the dynamics of the gear transmission system coupled with the effects of gear box vibrations. The developed numerical model is benchmarked with results from experimental tests at NASA Lewis Research Center. The modal synthesis approach is used to develop the global transient vibration analysis procedure used in the model. Modal dynamic characteristics of the rotor-gear-bearing system are calculated by the matrix transfer method while those of the gear box are evaluated by the finite element method (NASTRAN). A three-dimensional, axial-lateral coupled bearing model is used to couple the rotor vibrations with the gear box motion. The vibrations between the individual rotor systems are coupled through the nonlinear gear mesh interactions. The global equations of motion are solved in modal coordinates and the transient vibration of the system is evaluated by a variable time-stepping integration scheme. The relationship between housing vibration and resulting noise of the gear transmission system is generated by linear transfer functions using experimental data. A nonlinear relationship of the noise components to the fundamental mesh frequency is developed using the hypercoherence function. The numerically simulated vibrations and predicted noise of the gear transmission system are compared with the experimental results from the gear noise test rig at NASA Lewis Research Center. Results of the comparison indicate that the global dynamic model developed can accurately simulate the dynamics of a gear transmission system.
Global dynamic modeling of a transmission system
NASA Astrophysics Data System (ADS)
Choy, F. K.; Qian, W.
1993-04-01
The work performed on global dynamic simulation and noise correlation of gear transmission systems at the University of Akron is outlined. The objective is to develop a comprehensive procedure to simulate the dynamics of the gear transmission system coupled with the effects of gear box vibrations. The developed numerical model is benchmarked with results from experimental tests at NASA Lewis Research Center. The modal synthesis approach is used to develop the global transient vibration analysis procedure used in the model. Modal dynamic characteristics of the rotor-gear-bearing system are calculated by the matrix transfer method while those of the gear box are evaluated by the finite element method (NASTRAN). A three-dimensional, axial-lateral coupled bearing model is used to couple the rotor vibrations with the gear box motion. The vibrations between the individual rotor systems are coupled through the nonlinear gear mesh interactions. The global equations of motion are solved in modal coordinates and the transient vibration of the system is evaluated by a variable time-stepping integration scheme. The relationship between housing vibration and resulting noise of the gear transmission system is generated by linear transfer functions using experimental data. A nonlinear relationship of the noise components to the fundamental mesh frequency is developed using the hypercoherence function. The numerically simulated vibrations and predicted noise of the gear transmission system are compared with the experimental results from the gear noise test rig at NASA Lewis Research Center. Results of the comparison indicate that the global dynamic model developed can accurately simulate the dynamics of a gear transmission system.
Robust control synthesis for uncertain dynamical systems
NASA Technical Reports Server (NTRS)
Byun, Kuk-Whan; Wie, Bong; Sunkel, John
1989-01-01
This paper presents robust control synthesis techniques for uncertain dynamical systems subject to structured parameter perturbation. Both QFT (quantitative feedback theory) and H-infinity control synthesis techniques are investigated. Although most H-infinity-related control techniques are not concerned with the structured parameter perturbation, a new way of incorporating the parameter uncertainty in the robust H-infinity control design is presented. A generic model of uncertain dynamical systems is used to illustrate the design methodologies investigated in this paper. It is shown that, for a certain noncolocated structural control problem, use of both techniques results in nonminimum phase compensation.
Very Large System Dynamics Models - Lessons Learned
Jacob J. Jacobson; Leonard Malczynski
2008-10-01
This paper provides lessons learned from developing several large system dynamics (SD) models. System dynamics modeling practice emphasize the need to keep models small so that they are manageable and understandable. This practice is generally reasonable and prudent; however, there are times that large SD models are necessary. This paper outlines two large SD projects that were done at two Department of Energy National Laboratories, the Idaho National Laboratory and Sandia National Laboratories. This paper summarizes the models and then discusses some of the valuable lessons learned during these two modeling efforts.
FAST TRACK COMMUNICATION: Complexified dynamical systems
NASA Astrophysics Data System (ADS)
Bender, Carl M.; Holm, Darryl D.; Hook, Daniel W.
2007-08-01
Many dynamical systems, such as the Lotka-Volterra predator-prey model and the Euler equations for the free rotation of a rigid body, are {{\\cal P}}{{\\cal T}} symmetric. The standard and well-known real solutions to such dynamical systems constitute an infinitessimal subclass of the full set of complex solutions. This paper examines a subset of the complex solutions that contains the real solutions, namely those having {{\\cal P}}{{\\cal T}} symmetry. The condition of {{\\cal P}}{{\\cal T}} symmetry selects out complex solutions that are periodic.
Dynamics of biosonar systems in Horseshoe bats
NASA Astrophysics Data System (ADS)
Müller, R.
2015-12-01
Horseshoe bats have an active ultrasonic sonar system that allows the animals to navigate and hunt prey in structure-rich natural environments. The physical components of this biosonar system contain an unusual dynamics that could play a key role in achieving the animals' superior sensory performance. Horseshoe bat biosonar employs elaborate baffle shapes to diffract the outgoing and incoming ultrasonic wave packets; ultrasound is radiated from nostrils that are surrounded by noseleaves and received by large outer ears. Noseleaves and pinnae can be actuated while ultrasonic diffraction takes place. On the emission side, two noseleaf parts, the anterior leaf and the sella, have been shown to be in motion in synchrony with sound emission. On the reception side, the pinnae have been shown to change their shapes by up to 20% of their total length within ˜100 milliseconds. Due to these shape changes, diffraction of the incoming and outgoing waves is turned into a dynamic physical process. The dynamics of the diffraction process results in likewise dynamic device characteristics. If this additional dynamic dimension was found to enhance the encoding of sensory information substantially, horseshoe bat biosonar could be a model for the use of dynamic physical processes in sensing technology.
Improvement of the cine-CT based 4D-CT imaging
Pan Tinsu; Sun Xiaojun; Luo Dershan
2007-11-15
An improved 4D-CT utility has been developed on the GE LightSpeed multislice CT (MSCT) and Discovery PET/CT scanners, which have the cine CT scan capability. Two new features have been added in this 4D-CT over the commercial Advantage 4D-CT from GE. One feature was a new tool for disabling parts of the respiratory signal with irregular respiration and improving the accuracy of phase determination for the respiratory signal from the Varian real-time positioning and monitoring (RPM) system before sorting of the cine CT images into the 4D-CT images. The second feature was to allow generation of the maximum-intensity-projection (MIP), average (AVG) and minimum-intensity-projection (mip) CT images from the cine CT images without a respiratory signal. The implementation enables the assessment of tumor motion in treatment planning with the MIP, AVG, and mip CT images on the GE MSCT and PET/CT scanners without the RPM and the Advantage 4D-CT with a GE Advantage windows workstation. Several clinical examples are included to illustrate this new application.
Allowing for model error in strong constraint 4D-Var
NASA Astrophysics Data System (ADS)
Howes, Katherine; Lawless, Amos; Fowler, Alison
2016-04-01
Four dimensional variational data assimilation (4D-Var) can be used to obtain the best estimate of the initial conditions of an environmental forecasting model, namely the analysis. In practice, when the forecasting model contains errors, the analysis from the 4D-Var algorithm will be degraded to allow for errors later in the forecast window. This work focusses on improving the analysis at the initial time by allowing for the fact that the model contains error, within the context of strong constraint 4D-Var. The 4D-Var method developed acknowledges the presence of random error in the model at each time step by replacing the observation error covariance matrix with an error covariance matrix that includes both observation error and model error statistics. It is shown that this new matrix represents the correct error statistics of the innovations in the presence of model error. A method for estimating this matrix using innovation statistics, without requiring prior knowledge of the model error statistics, is presented. The method is demonstrated numerically using a non-linear chaotic system with erroneous parameter values. We show that that the new method works to reduce the analysis error covariance when compared with a standard strong constraint 4D-Var scheme. We discuss the fact that an improved analysis will not necessarily provide a better forecast.
Microfluidic systems for single DNA dynamics
Mai, Danielle J.; Brockman, Christopher
2012-01-01
Recent advances in microfluidics have enabled the molecular-level study of polymer dynamics using single DNA chains. Single polymer studies based on fluorescence microscopy allow for the direct observation of non-equilibrium polymer conformations and dynamical phenomena such as diffusion, relaxation, and molecular stretching pathways in flow. Microfluidic devices have enabled the precise control of model flow fields to study the non-equilibrium dynamics of soft materials, with device geometries including curved channels, cross-slots, and microfabricated obstacles and structures. This review explores recent microfluidic systems that have advanced the study of single polymer dynamics, while identifying new directions in the field that will further elucidate the relationship between polymer microstructure and bulk rheological properties. PMID:23139700
The investigation of tethered satellite system dynamics
NASA Technical Reports Server (NTRS)
Lorenzini, E.
1985-01-01
A progress report is presented that deals with three major topics related to Tethered Satellite System Dynamics. The SAO rotational dynamics computer code was updated. The program is now suitable to deal with inclined orbits. The output has been also modified in order to show the satellite Euler angles referred to the rotating orbital frame. The three-dimensional high resolution computer program SLACK3 was developed. The code simulates the three-dimensional dynamics of a tether going slack taking into account the effect produced by boom rotations. Preliminary simulations on the three-dimensional dynamics of a recoiling slack tether are shown in this report. A program to evaluate the electric potential around a severed tether is immersed in a plasma. The potential is computed on a three-dimensional grid axially symmetric with respect to the tether longitudinal axis. The electric potential variations due to the plasma are presently under investigation.
Constraint Embedding Technique for Multibody System Dynamics
NASA Technical Reports Server (NTRS)
Woo, Simon S.; Cheng, Michael K.
2011-01-01
Multibody dynamics play a critical role in simulation testbeds for space missions. There has been a considerable interest in the development of efficient computational algorithms for solving the dynamics of multibody systems. Mass matrix factorization and inversion techniques and the O(N) class of forward dynamics algorithms developed using a spatial operator algebra stand out as important breakthrough on this front. Techniques such as these provide the efficient algorithms and methods for the application and implementation of such multibody dynamics models. However, these methods are limited only to tree-topology multibody systems. Closed-chain topology systems require different techniques that are not as efficient or as broad as those for tree-topology systems. The closed-chain forward dynamics approach consists of treating the closed-chain topology as a tree-topology system subject to additional closure constraints. The resulting forward dynamics solution consists of: (a) ignoring the closure constraints and using the O(N) algorithm to solve for the free unconstrained accelerations for the system; (b) using the tree-topology solution to compute a correction force to enforce the closure constraints; and (c) correcting the unconstrained accelerations with correction accelerations resulting from the correction forces. This constraint-embedding technique shows how to use direct embedding to eliminate local closure-loops in the system and effectively convert the system back to a tree-topology system. At this point, standard tree-topology techniques can be brought to bear on the problem. The approach uses a spatial operator algebra approach to formulating the equations of motion. The operators are block-partitioned around the local body subgroups to convert them into aggregate bodies. Mass matrix operator factorization and inversion techniques are applied to the reformulated tree-topology system. Thus in essence, the new technique allows conversion of a system with
Cardea: Dynamic Access Control in Distributed Systems
NASA Technical Reports Server (NTRS)
Lepro, Rebekah
2004-01-01
Modern authorization systems span domains of administration, rely on many different authentication sources, and manage complex attributes as part of the authorization process. This . paper presents Cardea, a distributed system that facilitates dynamic access control, as a valuable piece of an inter-operable authorization framework. First, the authorization model employed in Cardea and its functionality goals are examined. Next, critical features of the system architecture and its handling of the authorization process are then examined. Then the S A M L and XACML standards, as incorporated into the system, are analyzed. Finally, the future directions of this project are outlined and connection points with general components of an authorization system are highlighted.
Operationalizing sustainability in urban coastal systems: a system dynamics analysis.
Mavrommati, Georgia; Bithas, Kostas; Panayiotidis, Panayiotis
2013-12-15
We propose a system dynamics approach for Ecologically Sustainable Development (ESD) in urban coastal systems. A systematic analysis based on theoretical considerations, policy analysis and experts' knowledge is followed in order to define the concept of ESD. The principles underlying ESD feed the development of a System Dynamics Model (SDM) that connects the pollutant loads produced by urban systems' socioeconomic activities with the ecological condition of the coastal ecosystem that it is delineated in operational terms through key biological elements defined by the EU Water Framework Directive. The receiving waters of the Athens Metropolitan area, which bears the elements of typical high population density Mediterranean coastal city but which currently has also new dynamics induced by the ongoing financial crisis, are used as an experimental system for testing a system dynamics approach to apply the concept of ESD. Systems' thinking is employed to represent the complex relationships among the components of the system. Interconnections and dependencies that determine the potentials for achieving ESD are revealed. The proposed system dynamics analysis can facilitate decision makers to define paths of development that comply with the principles of ESD. PMID:24200010
Solar dynamic power systems for space station
NASA Technical Reports Server (NTRS)
Irvine, Thomas B.; Nall, Marsha M.; Seidel, Robert C.
1986-01-01
The Parabolic Offset Linearly Actuated Reflector (POLAR) solar dynamic module was selected as the baseline design for a solar dynamic power system aboard the space station. The POLAR concept was chosen over other candidate designs after extensive trade studies. The primary advantages of the POLAR concept are the low mass moment of inertia of the module about the transverse boom and the compactness of the stowed module which enables packaging of two complete modules in the Shuttle orbiter payload bay. The fine pointing control system required for the solar dynamic module has been studied and initial results indicate that if disturbances from the station are allowed to back drive the rotary alpha joint, pointing errors caused by transient loads on the space station can be minimized. This would allow pointing controls to operate in bandwidths near system structural frequencies. The incorporation of the fine pointing control system into the solar dynamic module is fairly straightforward for the three strut concentrator support structure. However, results of structural analyses indicate that this three strut support is not optimum. Incorporation of a vernier pointing system into the proposed six strut support structure is being studied.
A 4D Hyperspherical Interpretation of q-Space
Hosseinbor, A. Pasha; Chung, Moo K.; Wu, Yu-Chien; Alexander, Andrew L.; Bendlin, Barbara B.
2014-01-01
3D q-space can be viewed as the surface of a 4D hypersphere. In this paper, we seek to develop a 4D hyperspherical interpretation of q-space by projecting it onto a hypersphere and subsequently modeling the q-space signal via 4D hyperspherical harmonics (HSH). Using this orthonormal basis, we analytically derive several quantitative indices and numerically estimate the diffusion ODF. Importantly, we derive the integral transform describing the relationship between the diffusion signal and propagator on a hypersphere. We also show that the HSH basis expends less fitting parameters than other well-established methods to achieve comparable signal and better ODF reconstructions. All in all, this work provides a new way of looking at q-space. PMID:24505799
2D:4D finger ratio positively correlates with total cerebral cortex in males.
Darnai, Gergely; Plózer, Enikő; Perlaki, Gábor; Orsi, Gergely; Nagy, Szilvia Anett; Horváth, Réka; Schwarcz, Attila; Kovács, Norbert; Altbäcker, Anna; Janszky, József; Clemens, Zsófia
2016-02-26
Although there is evidence that the ratio of 2nd-4th digit length (2D:4D) correlates with prenatal testosterone level, psychological and health traits only two studies have assessed the relationship with brain morphological features. Here we investigated the association between the 2D:4D ratio and several brain subvolumes. Seventy-five subjects between the ages of 18 and 30 were included in the study. The length of the 2nd and 4th digits were measured with an electronic vernier caliper while MRI measurements were performed on a Siemens Magnetom Trio Tim (3T) system. Freesurfer software suite was used for volumetric segmentation. Finger ratio significantly positively correlated with total cerebral cortex, total cerebellar white matter and total cerebellar cortex in males but not in females. Our results indicate that prenatal testosterone, as estimated by the 2D:4D ratio has an effect on adult brain morphology in males. PMID:26780566
Enhancing 4D PC-MRI in an aortic phantom considering numerical simulations
NASA Astrophysics Data System (ADS)
Kratzke, Jonas; Schoch, Nicolai; Weis, Christian; Müller-Eschner, Matthias; Speidel, Stefanie; Farag, Mina; Beller, Carsten J.; Heuveline, Vincent
2015-03-01
To date, cardiovascular surgery enables the treatment of a wide range of aortic pathologies. One of the current challenges in this field is given by the detection of high-risk patients for adverse aortic events, who should be treated electively. Reliable diagnostic parameters, which indicate the urge of treatment, have to be determined. Functional imaging by means of 4D phase contrast-magnetic resonance imaging (PC-MRI) enables the time-resolved measurement of blood flow velocity in 3D. Applied to aortic phantoms, three dimensional blood flow properties and their relation to adverse dynamics can be investigated in vitro. Emerging "in silico" methods of numerical simulation can supplement these measurements in computing additional information on crucial parameters. We propose a framework that complements 4D PC-MRI imaging by means of numerical simulation based on the Finite Element Method (FEM). The framework is developed on the basis of a prototypic aortic phantom and validated by 4D PC-MRI measurements of the phantom. Based on physical principles of biomechanics, the derived simulation depicts aortic blood flow properties and characteristics. The framework might help identifying factors that induce aortic pathologies such as aortic dilatation or aortic dissection. Alarming thresholds of parameters such as wall shear stress distribution can be evaluated. The combined techniques of 4D PC-MRI and numerical simulation can be used as complementary tools for risk-stratification of aortic pathology.
Emerging Applications of Abdominal 4D Flow MRI
Roldán-Alzate, Alejandro; Francois, Christopher J.; Wieben, Oliver; Reeder, Scott B.
2016-01-01
OBJECTIVE Comprehensive assessment of abdominal hemodynamics is crucial for many clinical diagnoses but is challenged by a tremendous complexity of anatomy, normal physiology, and a wide variety of pathologic abnormalities. This article introduces 4D flow MRI as a powerful technique for noninvasive assessment of the hemodynamics of abdominal vascular territories. CONCLUSION Four-dimensional flow MRI provides clinicians with a more extensive and straightforward approach to evaluate disorders that affect blood flow in the abdomen. This review presents a series of clinical cases to illustrate the utility of 4D flow MRI in the comprehensive assessment of the abdominal circulation. PMID:27187681
WELLTON GOVERNMENT CAMP, TEMPORARY RESIDENCE TYPE 4D. PLAN, SECTION, AND ...
WELLTON GOVERNMENT CAMP, TEMPORARY RESIDENCE TYPE 4D. PLAN, SECTION, AND ELEVATIONS. Drawing 50-308-4566, dated July 16, 1949. U.S. Department of the Interior, Bureau of Reclamation, Yuma, Arizona - Wellton-Mohawk Irrigation System, Building No. 6 A-B (Duplex), 30651 & 30653 Wellton-Mohawk Drive, Wellton, Yuma County, AZ
Constrained multibody system dynamics - An automated approach
NASA Astrophysics Data System (ADS)
Kamman, J. W.; Huston, R. L.
The governing equations for constrained multibody systems are formulated in a manner suitable for their automated, numerical development and solution. Specifically, the 'closed loop' problem of multibody chain systems is addressed. The governing equations are developed by modifying dynamical equations obtained from Lagrange's form of d'Alembert's principle. This modification, which is based upon a solution of the constraint equations obtained through a 'zero eigenvalues theorem', is, in effect, a contraction of the dynamical equations. It is observed that, for a system with n generalized coordinates and m constraint equations, the coefficients in the constraint equations may be viewed as 'constraint vectors' in n-dimensional space. Then, in this setting the system itself is free to move in the n-m directions which are 'orthogonal' to the constraint vectors.
Design tools for complex dynamic security systems.
Byrne, Raymond Harry; Rigdon, James Brian; Rohrer, Brandon Robinson; Laguna, Glenn A.; Robinett, Rush D. III; Groom, Kenneth Neal; Wilson, David Gerald; Bickerstaff, Robert J.; Harrington, John J.
2007-01-01
The development of tools for complex dynamic security systems is not a straight forward engineering task but, rather, a scientific task where discovery of new scientific principles and math is necessary. For years, scientists have observed complex behavior but have had difficulty understanding it. Prominent examples include: insect colony organization, the stock market, molecular interactions, fractals, and emergent behavior. Engineering such systems will be an even greater challenge. This report explores four tools for engineered complex dynamic security systems: Partially Observable Markov Decision Process, Percolation Theory, Graph Theory, and Exergy/Entropy Theory. Additionally, enabling hardware technology for next generation security systems are described: a 100 node wireless sensor network, unmanned ground vehicle and unmanned aerial vehicle.
Collisional and Dynamical Evolution of Planetary Systems
NASA Technical Reports Server (NTRS)
Weidenschilling, Stuart J.
2004-01-01
Senior Scientst S. J. Weidenschilling presents his final administrative report in the research program entitled "Collisional and Dynamical Evolution of Planetary Systems," on which he was the Principal Investigator. This research program produced the following publications: 1) "Jumping Jupiters" in binary star systems. F. Marzari, S. J. Weidenschilling, M. Barbieri and V. Granata. Astrophys. J., in press, 2005; 2) Formation of the cores of the outer planets. To appear in "The Outer Planets" (R. Kallenbach, ED), ISSI Conference Proceedings (Space Sci. Rev.), in press, 2005; 3) Accretion dynamics and timescales: Relation to chondrites. S. J. Weidenschilling and J. Cuzzi. In Meteorites and the Early Solar System LI (D. Lauretta et al., Eds.), Univ. of Arizona Press, 2005; 4) Asteroidal heating and thermal stratification of the asteroid belt. A. Ghosh, S. J.Weidenschilling, H. Y. McSween, Jr. and A. Rubin. In Meteorites and the Early Solar System I1 (D. Lauretta et al., Eds.), Univ. of Arizona Press, 2005.
Yue, Y; Fan, Z; Yang, W; Pang, J; McKenzie, E; Deng, Z; Tuli, R; Sandler, H; Li, D; Fraass, B
2014-06-15
Purpose: 4D-CT is often limited by motion artifacts, low temporal resolution, and poor phase-based target definition. We recently developed a novel k-space self-gated 4D-MRI technique with high spatial and temporal resolution. The goal here is to geometrically validate 4D-MRI using a MRI-CT compatible respiratory motion phantom and comparison to 4D-CT. Methods: 4D-MRI was acquired using 3T spoiled gradient echo-based 3D projection sequences. Respiratory phases were resolved using self-gated k-space lines as the motion surrogate. Images were reconstructed into 10 temporal bins with 1.56×1.56×1.56mm3. A MRI-CT compatible phantom was designed with a 23mm diameter ball target filled with highconcentration gadolinium(Gd) gel embedded in a 35×40×63mm3 plastic box stabilized with low-concentration Gd gel. The whole phantom was driven by an air pump. Human respiratory motion was mimicked using the controller from a commercial dynamic phantom (RSD). Four breathing settings (rates/depths: 10s/20mm, 6s/15mm, 4s/10mm, 3s/7mm) were scanned with 4D-MRI and 4D-CT (slice thickness 1.25mm). Motion ground-truth was obtained from input signals and real-time video recordings. Reconstructed images were imported into Eclipse(Varian) for target contouring. Volumes and target positions were compared with ground-truth. Initial human study was investigated on a liver patient. Results: 4D-MRI and 4D-CT scans for the different breathing cycles were reconstructed with 10 phases. Target volume in each phase was measured for both 4D-CT and 4D-MRI. Volume percentage difference for the 6.37ml target ranged from 6.67±5.33 to 11.63±5.57 for 4D-CT and from 1.47±0.52 to 2.12±1.60 for 4D-MRI. The Mann-Whitney U-test shows the 4D-MRI is significantly superior to 4D-CT (p=0.021) for phase-based target definition. Centroid motion error ranges were 1.35–1.25mm (4D-CT), and 0.31–0.12mm (4D-MRI). Conclusion: The k-space self-gated 4D-MRI we recently developed can accurately determine phase
Dynamical Systems Perspective of Wolfram's Cellular Automata
NASA Astrophysics Data System (ADS)
Courbage, M.; Kamiński, B.
2013-01-01
Leon Chua, following Wolfram, devoted a big effort to understand deeply the wealth of complexity of the rules of all elementary one-dimensional cellular automata from the point of view of the nonlinear dynamicist. Here we complete this point of view by a dynamical system perspective, extending them to the limit of infinite number of sites.
Induced topological pressure for topological dynamical systems
Xing, Zhitao; Chen, Ercai
2015-02-15
In this paper, inspired by the article [J. Jaerisch et al., Stochastics Dyn. 14, 1350016, pp. 1-30 (2014)], we introduce the induced topological pressure for a topological dynamical system. In particular, we prove a variational principle for the induced topological pressure.
Final Report Computational Analysis of Dynamical Systems
Guckenheimer, John
2012-05-08
This is the final report for DOE Grant DE-FG02-93ER25164, initiated in 1993. This grant supported research of John Guckenheimer on computational analysis of dynamical systems. During that period, seventeen individuals received PhD degrees under the supervision of Guckenheimer and over fifty publications related to the grant were produced. This document contains copies of these publications.
Computational dynamics of acoustically driven microsphere systems.
Glosser, Connor; Piermarocchi, Carlo; Li, Jie; Dault, Dan; Shanker, B
2016-01-01
We propose a computational framework for the self-consistent dynamics of a microsphere system driven by a pulsed acoustic field in an ideal fluid. Our framework combines a molecular dynamics integrator describing the dynamics of the microsphere system with a time-dependent integral equation solver for the acoustic field that makes use of fields represented as surface expansions in spherical harmonic basis functions. The presented approach allows us to describe the interparticle interaction induced by the field as well as the dynamics of trapping in counter-propagating acoustic pulses. The integral equation formulation leads to equations of motion for the microspheres describing the effect of nondissipative drag forces. We show (1) that the field-induced interactions between the microspheres give rise to effective dipolar interactions, with effective dipoles defined by their velocities and (2) that the dominant effect of an ultrasound pulse through a cloud of microspheres gives rise mainly to a translation of the system, though we also observe both expansion and contraction of the cloud determined by the initial system geometry. PMID:26871188
Invariant of dynamical systems: A generalized entropy
Meson, A.M.; Vericat, F. |
1996-09-01
In this work the concept of entropy of a dynamical system, as given by Kolmogorov, is generalized in the sense of Tsallis. It is shown that this entropy is an isomorphism invariant, being complete for Bernoulli schemes. {copyright} {ital 1996 American Institute of Physics.}
Detection of abrupt changes in dynamic systems
NASA Technical Reports Server (NTRS)
Willsky, A. S.
1984-01-01
Some of the basic ideas associated with the detection of abrupt changes in dynamic systems are presented. Multiple filter-based techniques and residual-based method and the multiple model and generalized likelihood ratio methods are considered. Issues such as the effect of unknown onset time on algorithm complexity and structure and robustness to model uncertainty are discussed.
Computational dynamics of acoustically driven microsphere systems.
Glosser, Connor; Piermarocchi, Carlo; Li, Jie; Dault, Dan; Shanker, B
2016-01-01
We propose a computational framework for the self-consistent dynamics of a microsphere system driven by a pulsed acoustic field in an ideal fluid. Our framework combines a molecular dynamics integrator describing the dynamics of the microsphere system with a time-dependent integral equation solver for the acoustic field that makes use of fields represented as surface expansions in spherical harmonic basis functions. The presented approach allows us to describe the interparticle interaction induced by the field as well as the dynamics of trapping in counter-propagating acoustic pulses. The integral equation formulation leads to equations of motion for the microspheres describing the effect of nondissipative drag forces. We show (1) that the field-induced interactions between the microspheres give rise to effective dipolar interactions, with effective dipoles defined by their velocities and (2) that the dominant effect of an ultrasound pulse through a cloud of microspheres gives rise mainly to a translation of the system, though we also observe both expansion and contraction of the cloud determined by the initial system geometry.
4D motion animation of coronary arteries from rotational angiography
NASA Astrophysics Data System (ADS)
Holub, Wolfgang; Rohkohl, Christopher; Schuldhaus, Dominik; Prümmer, Marcus; Lauritsch, Günter; Hornegger, Joachim
2011-03-01
Time-resolved 3-D imaging of the heart is a major research topic in the medical imaging community. Recent advances in the interventional cardiac 3-D imaging from rotational angiography (C-arm CT) are now also making 4-D imaging feasible during procedures in the catheter laboratory. State-of-the-art reconstruction algorithms try to estimate the cardiac motion and utilize the motion field to enhance the reconstruction of a stable cardiac phase (diastole). The available data offers a handful of opportunities during interventional procedures, e.g. the ECG-synchronized dynamic roadmapping or the computation and analysis of functional parameters. In this paper we will demonstrate that the motion vector field (MVF) that is output by motion compensated image reconstruction algorithms is in general not directly usable for animation and motion analysis. Dependent on the algorithm different defects are investigated. A primary issue is that the MVF needs to be inverted, i.e. the wrong direction of motion is provided. A second major issue is the non-periodicity of cardiac motion. In algorithms which compute a non-periodic motion field from a single rotation the in depth motion information along viewing direction is missing, since this cannot be measured in the projections. As a result, while the MVF improves reconstruction quality, it is insufficient for motion animation and analysis. We propose an algorithm to solve both problems, i.e. inversion and missing in-depth information in a unified framework. A periodic version of the MVF is approximated. The task is formulated as a linear optimization problem where a parametric smooth motion model based on B-splines is estimated from the MVF. It is shown that the problem can be solved using a sparse QR factorization within a clinical feasible time of less than one minute. In a phantom experiment using the publicly available CAVAREV platform, the average quality of a non-periodic animation could be increased by 39% by applying the
A dose error evaluation study for 4D dose calculations
NASA Astrophysics Data System (ADS)
Milz, Stefan; Wilkens, Jan J.; Ullrich, Wolfgang
2014-10-01
Previous studies have shown that respiration induced motion is not negligible for Stereotactic Body Radiation Therapy. The intrafractional breathing induced motion influences the delivered dose distribution on the underlying patient geometry such as the lung or the abdomen. If a static geometry is used, a planning process for these indications does not represent the entire dynamic process. The quality of a full 4D dose calculation approach depends on the dose coordinate transformation process between deformable geometries. This article provides an evaluation study that introduces an advanced method to verify the quality of numerical dose transformation generated by four different algorithms. The used transformation metric value is based on the deviation of the dose mass histogram (DMH) and the mean dose throughout dose transformation. The study compares the results of four algorithms. In general, two elementary approaches are used: dose mapping and energy transformation. Dose interpolation (DIM) and an advanced concept, so called divergent dose mapping model (dDMM), are used for dose mapping. The algorithms are compared to the basic energy transformation model (bETM) and the energy mass congruent mapping (EMCM). For evaluation 900 small sample regions of interest (ROI) are generated inside an exemplary lung geometry (4DCT). A homogeneous fluence distribution is assumed for dose calculation inside the ROIs. The dose transformations are performed with the four different algorithms. The study investigates the DMH-metric and the mean dose metric for different scenarios (voxel sizes: 8 mm, 4 mm, 2 mm, 1 mm 9 different breathing phases). dDMM achieves the best transformation accuracy in all measured test cases with 3-5% lower errors than the other models. The results of dDMM are reasonable and most efficient in this study, although the model is simple and easy to implement. The EMCM model also achieved suitable results, but the approach requires a more complex
Predicting lower mantle heterogeneity from 4-D Earth models
NASA Astrophysics Data System (ADS)
Flament, Nicolas; Williams, Simon; Müller, Dietmar; Gurnis, Michael; Bower, Dan J.
2016-04-01
basal layer ˜ 4% denser than ambient mantle. Increasing convective vigour (Ra ≈ 5 x 108) or decreasing the density of the basal layer decreases both the accuracy and sensitivity of the predicted lower mantle structure. References: D. J. Bower, M. Gurnis, N. Flament, Assimilating lithosphere and slab history in 4-D Earth models. Phys. Earth Planet. Inter. 238, 8-22 (2015). V. Lekic, S. Cottaar, A. Dziewonski, B. Romanowicz, Cluster analysis of global lower mantle tomography: A new class of structure and implications for chemical heterogeneity. Earth Planet. Sci. Lett. 357, 68-77 (2012).
Fast interactive exploration of 4D MRI flow data
NASA Astrophysics Data System (ADS)
Hennemuth, A.; Friman, O.; Schumann, C.; Bock, J.; Drexl, J.; Huellebrand, M.; Markl, M.; Peitgen, H.-O.
2011-03-01
1- or 2-directional MRI blood flow mapping sequences are an integral part of standard MR protocols for diagnosis and therapy control in heart diseases. Recent progress in rapid MRI has made it possible to acquire volumetric, 3-directional cine images in reasonable scan time. In addition to flow and velocity measurements relative to arbitrarily oriented image planes, the analysis of 3-dimensional trajectories enables the visualization of flow patterns, local features of flow trajectories or possible paths into specific regions. The anatomical and functional information allows for advanced hemodynamic analysis in different application areas like stroke risk assessment, congenital and acquired heart disease, aneurysms or abdominal collaterals and cranial blood flow. The complexity of the 4D MRI flow datasets and the flow related image analysis tasks makes the development of fast comprehensive data exploration software for advanced flow analysis a challenging task. Most existing tools address only individual aspects of the analysis pipeline such as pre-processing, quantification or visualization, or are difficult to use for clinicians. The goal of the presented work is to provide a software solution that supports the whole image analysis pipeline and enables data exploration with fast intuitive interaction and visualization methods. The implemented methods facilitate the segmentation and inspection of different vascular systems. Arbitrary 2- or 3-dimensional regions for quantitative analysis and particle tracing can be defined interactively. Synchronized views of animated 3D path lines, 2D velocity or flow overlays and flow curves offer a detailed insight into local hemodynamics. The application of the analysis pipeline is shown for 6 cases from clinical practice, illustrating the usefulness for different clinical questions. Initial user tests show that the software is intuitive to learn and even inexperienced users achieve good results within reasonable processing
Diagnosis of dynamical systems with fluctuating parameters
NASA Astrophysics Data System (ADS)
Ruelle, D.
1987-09-01
The applicability of mathematical models of chaos to physical, biological, and economic systems is discussed. The fundamental principles of the ergodic approach to chaos are briefly reviewed, and it is pointed out that in some natural phenomena the time evolution has adiabatically fluctuating parameters. It is suggested that these phenomena may be analyzable even though they are not represented by autonomous dynamical systems. The kinds of results to be expected from such an analysis are considered.
Earth and ocean dynamics satellites and systems
NASA Technical Reports Server (NTRS)
Vonbun, F. O.
1975-01-01
An overview is presented of the present state of satellite and ground systems making observations of the dynamics of the solid earth and the oceans. Emphasis is placed on applications of space technology for practical use. Topics discussed include: satellite missions and results over the last two decades in the areas of earth gravity field, polar motions, earth tides, magnetic anomalies, and satellite-to-satellite tracking; laser ranging systems; development of the Very Long Baseline Interferometer; and Skylab radar altimeter data applications.
Automated Design of Complex Dynamic Systems
Hermans, Michiel; Schrauwen, Benjamin; Bienstman, Peter; Dambre, Joni
2014-01-01
Several fields of study are concerned with uniting the concept of computation with that of the design of physical systems. For example, a recent trend in robotics is to design robots in such a way that they require a minimal control effort. Another example is found in the domain of photonics, where recent efforts try to benefit directly from the complex nonlinear dynamics to achieve more efficient signal processing. The underlying goal of these and similar research efforts is to internalize a large part of the necessary computations within the physical system itself by exploiting its inherent non-linear dynamics. This, however, often requires the optimization of large numbers of system parameters, related to both the system's structure as well as its material properties. In addition, many of these parameters are subject to fabrication variability or to variations through time. In this paper we apply a machine learning algorithm to optimize physical dynamic systems. We show that such algorithms, which are normally applied on abstract computational entities, can be extended to the field of differential equations and used to optimize an associated set of parameters which determine their behavior. We show that machine learning training methodologies are highly useful in designing robust systems, and we provide a set of both simple and complex examples using models of physical dynamical systems. Interestingly, the derived optimization method is intimately related to direct collocation a method known in the field of optimal control. Our work suggests that the application domains of both machine learning and optimal control have a largely unexplored overlapping area which envelopes a novel design methodology of smart and highly complex physical systems. PMID:24497969
Dynamic Analysis of Nuclear Energy System Strategies
Den Durpel, Luc Van
2004-06-17
DANESS is an integrated process model for nuclear energy systems allowing the simulation of multiple reactors and fuel cycles in a continuously changing nuclear reactor park configuration. The model is energy demand driven and simulates all nuclear fuel cycle facilites, up to 10 reactors and fuels. Reactor and fuel cycle facility history are traced and the cost of generating energy is calculated per reactor and for total nuclear energy system. The DANESS model aims at performing dynamic systems analysis of nuclear energy development used for integrated analysis of development paths for nuclear energy, parameter scoping for new nuclear energy systems, economic analysis of nuclear energy, government role analysis, and education.
Nonlinear dynamic macromodeling techniques for audio systems
NASA Astrophysics Data System (ADS)
Ogrodzki, Jan; Bieńkowski, Piotr
2015-09-01
This paper develops a modelling method and a models identification technique for the nonlinear dynamic audio systems. Identification is performed by means of a behavioral approach based on a polynomial approximation. This approach makes use of Discrete Fourier Transform and Harmonic Balance Method. A model of an audio system is first created and identified and then it is simulated in real time using an algorithm of low computational complexity. The algorithm consists in real time emulation of the system response rather than in simulation of the system itself. The proposed software is written in Python language using object oriented programming techniques. The code is optimized for a multithreads environment.
Stability precision dynamic testing system on artillery
NASA Astrophysics Data System (ADS)
Wang, Chunyan; Li, Bo
2014-12-01
Dynamic feature of Weapon equipments is one of important performance index for evaluating the performance of the whole weapon system. The construction of target range in our country in fire control dynamic testing is relatively backward; therefore, it has greatly influenced the evaluation on the fire control system. In order to solve this problem, it's urgent to develop a new testing instrument so as to adjust to the armament research process and promote weapon system working more efficiently and thereby meeting the needs of modernization in national defense. This paper proposes a new measure which is used to test the stability precision of the fire control system, and it is installed on the moving base. Using the method, we develop a testing system which can test the stability precision of the fire control system and achieve a high precision results after testing. The innovation of the system is we can receive the image not only by CCD, but our eyes. It also adopts digital image-forming and image processing technique for real-time measurement and storing of the target information; it simultaneously adopts the method adjusting the platform and the corresponding fixture mounted on a sample to measure the stable precision and the precision of corner of stabilizator. In this paper, we make a description on the construction of the system and the idea of the designing of the optical system. Finally, we introduce the actual application of the system and testing results.
A robotic approach to 4D real-time tumor tracking for radiotherapy
NASA Astrophysics Data System (ADS)
Buzurovic, I.; Huang, K.; Yu, Y.; Podder, T. K.
2011-03-01
Respiratory and cardiac motions induce displacement and deformation of the tumor volumes in various internal organs. To accommodate this undesired movement and other errors, physicians incorporate a large margin around the tumor to delineate the planning target volume, so that the clinical target volume receives the prescribed radiation dose under any scenario. Consequently, a large volume of healthy tissue is irradiated and sometimes it is difficult to spare critical organs adjacent to the tumor. In this study we have proposed a novel approach to the 4D active tracking and dynamic delivery incorporating the tumor motion prediction technique. This method has been applied to the two commercially available robotic treatment couches. The proposed algorithm can predict the tumor position and the robotic systems are able to continuously track the tumor during radiation dose delivery. Therefore a precise dose is given to a moving target while the dose to the nearby critical organs is reduced to improve the patient treatment outcome. The efficacy of the proposed method has been investigated by extensive computer simulation. The tumor tracking method is simulated for two couches: HexaPOD robotic couch and ELEKTA Precise Table. The comparison results have been presented in this paper. In order to assess the clinical significance, dosimetric effects of the proposed method have been analyzed.
Effects of 2,4-D and DCP on the DHT-induced androgenic action in human prostate cancer cells.
Kim, Hyun-Jung; Park, Young In; Dong, Mi-Sook
2005-11-01
2,4-Dichlorophenoxyacetic acid (2,4-D) and its metabolite 2,4-dichlorophenol (DCP) are used extensively in agriculture as herbicides, and are suspected of potential endocrine disruptor activity. In a previous study, we showed that these compounds exhibited synergistic androgenic effects by co-treatment with testosterone in the Hershberger assay. To elucidate the mechanisms of the synergistic effects of these compounds on the androgenicity of testosterone, the androgenic action of 2,4-D and DCP was characterized using a mammalian detection system in prostate cancer cell lines. In in vitro assay systems, while 2,4-D or DCP alone did not show androgenic activity, 2,4-D or DCP with 5alpha-dihydroxytestosterone (DHT) exhibited synergistic androgenic activities. Co-treatment of 10 nM 2,4-D or DCP with 10 nM DHT was shown to stimulate the cell proliferation by 1.6-fold, compared to 10 nM DHT alone. In addition, in transient transfection assays, androgen-induced transactivation was also increased to a maximum of 32-fold or 1.28-fold by co-treatment of 2,4-D or DCP with DHT, respectively. However, 2,4-D and DCP exerted no effects on either mRNA or protein levels of AR. In a competitive AR binding assay, 2,4-D and DCP inhibited androgen binding to AR, up to 50% at concentrations of approximately 0.5 microM for both compounds. The nuclear translocation of green fluorescent protein-AR fusion protein in the presence of DHT was promoted as the result of the addition of 2,4-D and DCP. Collectively, these results that 2,4-D and DCP enhanced DHT-induced AR transcriptional activity might be attributable, at least in part, to the promotion of AR nuclear translocation.
Bütschli dynamic droplet system.
Armstrong, Rachel; Hanczyc, Martin
2013-01-01
Dynamical oil-water systems such as droplets display lifelike properties and may lend themselves to chemical programming to perform useful work, specifically with respect to the built environment. We present Bütschli water-in-oil droplets as a model for further investigation into the development of a technology with living properties. Otto Bütschli first described the system in 1898, when he used alkaline water droplets in olive oil to initiate a saponification reaction. This simple recipe produced structures that moved and exhibited characteristics that resembled, at least superficially, the amoeba. We reconstructed the Bütschli system and observed its life span under a light microscope, observing chemical patterns and droplet behaviors in nearly three hundred replicate experiments. Self-organizing patterns were observed, and during this dynamic, embodied phase the droplets provided a means of introducing temporal and spatial order in the system with the potential for chemical programmability. The authors propose that the discrete formation of dynamic droplets, characterized by their lifelike behavior patterns, during a variable window of time (from 30 s to 30 min after the addition of alkaline water to the oil phase), qualify this system as an example of living technology. The analysis of the Bütschli droplets suggests that a set of conditions may precede the emergence of lifelike characteristics and exemplifies the richness of this rudimentary chemical system, not only for artificial life investigations but also for possible real-world applications in architectural practice. PMID:23834593
Online reinforcement learning for dynamic multimedia systems.
Mastronarde, Nicholas; van der Schaar, Mihaela
2010-02-01
In our previous work, we proposed a systematic cross-layer framework for dynamic multimedia systems, which allows each layer to make autonomous and foresighted decisions that maximize the system's long-term performance, while meeting the application's real-time delay constraints. The proposed solution solved the cross-layer optimization offline, under the assumption that the multimedia system's probabilistic dynamics were known a priori, by modeling the system as a layered Markov decision process. In practice, however, these dynamics are unknown a priori and, therefore, must be learned online. In this paper, we address this problem by allowing the multimedia system layers to learn, through repeated interactions with each other, to autonomously optimize the system's long-term performance at run-time. The two key challenges in this layered learning setting are: (i) each layer's learning performance is directly impacted by not only its own dynamics, but also by the learning processes of the other layers with which it interacts; and (ii) selecting a learning model that appropriately balances time-complexity (i.e., learning speed) with the multimedia system's limited memory and the multimedia application's real-time delay constraints. We propose two reinforcement learning algorithms for optimizing the system under different design constraints: the first algorithm solves the cross-layer optimization in a centralized manner and the second solves it in a decentralized manner. We analyze both algorithms in terms of their required computation, memory, and interlayer communication overheads. After noting that the proposed reinforcement learning algorithms learn too slowly, we introduce a complementary accelerated learning algorithm that exploits partial knowledge about the system's dynamics in order to dramatically improve the system's performance. In our experiments, we demonstrate that decentralized learning can perform equally as well as centralized learning, while
Construction of 4D high-definition cortical surface atlases of infants: Methods and applications.
Li, Gang; Wang, Li; Shi, Feng; Gilmore, John H; Lin, Weili; Shen, Dinggang
2015-10-01
In neuroimaging, cortical surface atlases play a fundamental role for spatial normalization, analysis, visualization, and comparison of results across individuals and different studies. However, existing cortical surface atlases created for adults are not suitable for infant brains during the first two postnatal years, which is the most dynamic period of postnatal structural and functional development of the highly-folded cerebral cortex. Therefore, spatiotemporal cortical surface atlases for infant brains are highly desired yet still lacking for accurate mapping of early dynamic brain development. To bridge this significant gap, leveraging our infant-dedicated computational pipeline for cortical surface-based analysis and the unique longitudinal infant MRI dataset acquired in our research center, in this paper, we construct the first spatiotemporal (4D) high-definition cortical surface atlases for the dynamic developing infant cortical structures at seven time points, including 1, 3, 6, 9, 12, 18, and 24 months of age, based on 202 serial MRI scans from 35 healthy infants. For this purpose, we develop a novel method to ensure the longitudinal consistency and unbiasedness to any specific subject and age in our 4D infant cortical surface atlases. Specifically, we first compute the within-subject mean cortical folding by unbiased groupwise registration of longitudinal cortical surfaces of each infant. Then we establish longitudinally-consistent and unbiased inter-subject cortical correspondences by groupwise registration of the geometric features of within-subject mean cortical folding across all infants. Our 4D surface atlases capture both longitudinally-consistent dynamic mean shape changes and the individual variability of cortical folding during early brain development. Experimental results on two independent infant MRI datasets show that using our 4D infant cortical surface atlases as templates leads to significantly improved accuracy for spatial normalization
Quantum dynamics of hydrogen atoms on graphene. I. System-bath modeling
Bonfanti, Matteo; Jackson, Bret; Hughes, Keith H.; Burghardt, Irene
2015-09-28
An accurate system-bath model to investigate the quantum dynamics of hydrogen atoms chemisorbed on graphene is presented. The system comprises a hydrogen atom and the carbon atom from graphene that forms the covalent bond, and it is described by a previously developed 4D potential energy surface based on density functional theory ab initio data. The bath describes the rest of the carbon lattice and is obtained from an empirical force field through inversion of a classical equilibrium correlation function describing the hydrogen motion. By construction, model building easily accommodates improvements coming from the use of higher level electronic structure theory for the system. Further, it is well suited to a determination of the system-environment coupling by means of ab initio molecular dynamics. This paper details the system-bath modeling and shows its application to the quantum dynamics of vibrational relaxation of a chemisorbed hydrogen atom, which is here investigated at T = 0 K with the help of the multi-configuration time-dependent Hartree method. Paper II deals with the sticking dynamics.
2,4-Dichlorophenoxyacetic acid (2,4-D)
Integrated Risk Information System (IRIS)
2,4 - Dichlorophenoxyacetic acid ( 2,4 - D ) ; CASRN 94 - 75 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Asses
Enterococcus faecalis promotes osteoclastogenesis and semaphorin 4D expression.
Wang, Shuai; Deng, Zuhui; Seneviratne, Chaminda J; Cheung, Gary S P; Jin, Lijian; Zhao, Baohong; Zhang, Chengfei
2015-10-01
Enterococcus faecalis is considered a major bacterial pathogen implicated in endodontic infections and contributes considerably to periapical periodontitis. This study aimed to investigate the potential mechanisms by which E. faecalis accounts for the bone destruction in periapical periodontitis in vitro. Osteoclast precursor RAW264.7 cells were treated with E. faecalis ATCC 29212 and a wild strain of E. faecalis derived clinically from an infected root canal. The results showed that, to some extent, E. faecalis induced the RAW264.7 cells to form tartrate-resistant acid phosphatase (TRAP)-positive multinucleated osteoclast-like cells. This pathogen markedly stimulated RAW264.7 cells to express semaphorin 4D (Sema4D), which inhibits bone formation. Once RAW264.7 cells were primed by low-dose receptor activator of nuclear factor-kappa B ligand (RANKL), E. faecalis could significantly increase the production of TRAP-positive multinucleated cells and up-regulate the expression of osteoclast-specific markers, including NFATc1, TRAP and cathepsin K. Both p38 and ERK1/2 MAPK signaling pathways were activated by E. faecalis in RANKL-primed RAW264.7 cells, and meanwhile the expression of Sema4D was highly increased. In conclusion, E. faecalis may greatly contribute to the bone resorption in periapical periodontitis by promoting RANKL-dependent osteoclastogenesis and expression of Sema4D through activation of p38 and ERK1/2 MAPK signaling pathways.
A method for deriving a 4D-interpolated balanced planning target for mobile tumor radiotherapy
Roland, Teboh; Hales, Russell; McNutt, Todd; Wong, John; Simari, Patricio; Tryggestad, Erik
2012-01-15
resulting from the new approach was quantified. Results: Analysis of the 4D dose distributions from all five patients showed that while achieving tumor coverage comparable to the ITV approach, the new planning target definition resulted in reductions of lung V{sub 10}, V{sub 20}, and V{sub 30} of 6.3% {+-} 1.7%, 10.6% {+-} 3.9%, and 12.9% {+-} 5.5%, respectively, as well as reductions in mean lung dose, mean dose to the GTV-ring and mean heart dose of 8.8% {+-} 2.5%, 7.2% {+-} 2.5%, and 10.6% {+-} 3.6%, respectively. Conclusions: The authors have developed a simple and systematic approach to generate a 4D-interpolated balanced planning target volume that implicitly incorporates the dynamics of respiratory-organ motion without requiring 4D-dose computation or optimization. Preliminary results based on 4D-CT data of five previously treated lung patients showed that this new planning target approach may improve normal tissue sparing without sacrificing tumor coverage.
Nonlinear dynamical system approaches towards neural prosthesis
Torikai, Hiroyuki; Hashimoto, Sho
2011-04-19
An asynchronous discrete-state spiking neurons is a wired system of shift registers that can mimic nonlinear dynamics of an ODE-based neuron model. The control parameter of the neuron is the wiring pattern among the registers and thus they are suitable for on-chip learning. In this paper an asynchronous discrete-state spiking neuron is introduced and its typical nonlinear phenomena are demonstrated. Also, a learning algorithm for a set of neurons is presented and it is demonstrated that the algorithm enables the set of neurons to reconstruct nonlinear dynamics of another set of neurons with unknown parameter values. The learning function is validated by FPGA experiments.
Preparation of dynamic gravity testing system
NASA Astrophysics Data System (ADS)
Bowin, Carl
Bowin's interest at WHOI is to obtain the most accurate gravity and gravity gradient measurements possible. The Navy's interest is to have the most accurate navigation possible. Neither can have one without the other. Through Zarak Corporation, Bowin has proposed to the Navy Air System Command to develop a dynamic navigational gravity/gravity gradient (NAV/GRAV) system utilizing superconducting squid gravity and tensor gravity gradient sensors for high precision performance. The proposed system development incorporates that inter-dependency, not only to provide the best estimates of both, but also to provide estimates of the quality of the results obtained. Zarak is pursuing funds for the development of superconducting gravity and gravity gradient sensors. Such sensors, when available, will then be utilized in this palletized system for higher accuracy navigation, gravity and gravity gradient determination. It is desired that initial testing utilize Vibrating String Accelerometers (VSA) gravity sensors and readout systems available at WHOI. This way the development and testing of the NAV/GRAV system can proceed using the VSA sensors while the superconducting gravity sensors are being fabricated. Initial dynamic systems tests will be in a van vehicle for convenience and practicality. The system units will be palletized, and therefore they shall be easily transferable, and thus also be usable in aircraft and ships. It is planned that WHOI will have loan of prototype systems for about two months each year for earth research use.
GRAM 88 - 4D GLOBAL REFERENCE ATMOSPHERE MODEL-1988
NASA Technical Reports Server (NTRS)
Johnson, D. L.
1994-01-01
the Jacchia values. 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. GRAM-88 incorporates a hydrostatic/gas law check in the 0-30 km altitude range to flag and change any bad data points. Between 5km 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 GRAM-88 program is for batch execution on the IBM 3084. It is written in STANDARD FORTRAN 77 under the MVS/XA operating system. The IBM DISPLA graphics routines are necessary for graphical output. The program was developed in 1988.
Advances in 4D Treatment Planning for Scanned Particle Beam Therapy — Report of Dedicated Workshops
Bert, Christoph; Graeff, Christian; Riboldi, Marco; Nill, Simeon; Baroni, Guido; Knopf, Antje-Christin
2014-01-01
We report on recent progress in the field of mobile tumor treatment with scanned particle beams, as discussed in the latest editions of the 4D treatment planning workshop. The workshop series started in 2009, with about 20 people from 4 research institutes involved, all actively working on particle therapy delivery and development. The first workshop resulted in a summary of recommendations for the treatment of mobile targets, along with a list of requirements to apply these guidelines clinically. The increased interest in the treatment of mobile tumors led to a continuously growing number of attendees: the 2012 edition counted more than 60 participants from 20 institutions and commercial vendors. The focus of research discussions among workshop participants progressively moved from 4D treatment planning to complete 4D treatments, aiming at effective and safe treatment delivery. Current research perspectives on 4D treatments include all critical aspects of time resolved delivery, such as in-room imaging, motion detection, beam application, and quality assurance techniques. This was motivated by the start of first clinical treatments of hepato cellular tumors with a scanned particle beam, relying on gating or abdominal compression for motion mitigation. Up to date research activities emphasize significant efforts in investigating advanced motion mitigation techniques, with a specific interest in the development of dedicated tools for experimental validation. Potential improvements will be made possible in the near future through 4D optimized treatment plans that require upgrades of the currently established therapy control systems for time resolved delivery. But since also these novel optimization techniques rely on the validity of the 4DCT, research focusing on alternative 4D imaging technique, such as MRI based 4DCT generation will continue. PMID:24354749
The internal dynamics of international migration systems.
Waldorf, B
1996-04-01
"In this paper I provide a conceptualization of international migration networks, which can be used to identify and integrate the internal components of migration systems, and formalize the relationships in an analytic model of the internal network dynamic. With the use of the operationalized model, and microlevel and macrolevel data for guestworkers in Germany during the period 1970 to 1989, we can empirically test the relative influence of internal network variables versus external forces on the attraction of immigrants over time. The empirical results suggest that--as the system matures--network variables have an increasing impact on the attraction of immigrants, while the impact of economic factors declines. The research is concluded with a series of simulations that further highlight the internal dynamic of international migration systems."
Dynamic graph system for a semantic database
Mizell, David
2015-01-27
A method and system in a computer system for dynamically providing a graphical representation of a data store of entries via a matrix interface is disclosed. A dynamic graph system provides a matrix interface that exposes to an application program a graphical representation of data stored in a data store such as a semantic database storing triples. To the application program, the matrix interface represents the graph as a sparse adjacency matrix that is stored in compressed form. Each entry of the data store is considered to represent a link between nodes of the graph. Each entry has a first field and a second field identifying the nodes connected by the link and a third field with a value for the link that connects the identified nodes. The first, second, and third fields represent the rows, column, and elements of the adjacency matrix.
Stability threshold approach for complex dynamical systems
NASA Astrophysics Data System (ADS)
Klinshov, Vladimir V.; Nekorkin, Vladimir I.; Kurths, Jürgen
2016-01-01
A new measure to characterize the stability of complex dynamical systems against large perturbations is suggested, the stability threshold (ST). It quantifies the magnitude of the weakest perturbation capable of disrupting the system and switch it to an undesired dynamical regime. In the phase space, the ST corresponds to the ‘thinnest site’ of the attraction basin and therefore indicates the most ‘dangerous’ direction of perturbations. We introduce a computational algorithm for quantification of the ST and demonstrate that the suggested approach is effective and provides important insights. The generality of the obtained results defines their vast potential for application in such fields as engineering, neuroscience, power grids, Earth science and many others where the robustness of complex systems is studied.
Dynamic graph system for a semantic database
Mizell, David
2016-04-12
A method and system in a computer system for dynamically providing a graphical representation of a data store of entries via a matrix interface is disclosed. A dynamic graph system provides a matrix interface that exposes to an application program a graphical representation of data stored in a data store such as a semantic database storing triples. To the application program, the matrix interface represents the graph as a sparse adjacency matrix that is stored in compressed form. Each entry of the data store is considered to represent a link between nodes of the graph. Each entry has a first field and a second field identifying the nodes connected by the link and a third field with a value for the link that connects the identified nodes. The first, second, and third fields represent the rows, column, and elements of the adjacency matrix.
Keystroke Dynamics-Based Credential Hardening Systems
NASA Astrophysics Data System (ADS)
Bartlow, Nick; Cukic, Bojan
abstract Keystroke dynamics are becoming a well-known method for strengthening username- and password-based credential sets. The familiarity and ease of use of these traditional authentication schemes combined with the increased trustworthiness associated with biometrics makes them prime candidates for application in many web-based scenarios. Our keystroke dynamics system uses Breiman’s random forests algorithm to classify keystroke input sequences as genuine or imposter. The system is capable of operating at various points on a traditional ROC curve depending on application-specific security needs. As a username/password authentication scheme, our approach decreases the system penetration rate associated with compromised passwords up to 99.15%. Beyond presenting results demonstrating the credential hardening effect of our scheme, we look into the notion that a user’s familiarity to components of a credential set can non-trivially impact error rates.
4D MR imaging using robust internal respiratory signal
NASA Astrophysics Data System (ADS)
Hui, CheukKai; Wen, Zhifei; Stemkens, Bjorn; Tijssen, R. H. N.; van den Berg, C. A. T.; Hwang, Ken-Pin; Beddar, Sam
2016-05-01
The purpose of this study is to investigate the feasibility of using internal respiratory (IR) surrogates to sort four-dimensional (4D) magnetic resonance (MR) images. The 4D MR images were constructed by acquiring fast 2D cine MR images sequentially, with each slice scanned for more than one breathing cycle. The 4D volume was then sorted retrospectively using the IR signal. In this study, we propose to use multiple low-frequency components in the Fourier space as well as the anterior body boundary as potential IR surrogates. From these potential IR surrogates, we used a clustering algorithm to identify those that best represented the respiratory pattern to derive the IR signal. A study with healthy volunteers was performed to assess the feasibility of the proposed IR signal. We compared this proposed IR signal with the respiratory signal obtained using respiratory bellows. Overall, 99% of the IR signals matched the bellows signals. The average difference between the end inspiration times in the IR signal and bellows signal was 0.18 s in this cohort of matching signals. For the acquired images corresponding to the other 1% of non-matching signal pairs, the respiratory motion shown in the images was coherent with the respiratory phases determined by the IR signal, but not the bellows signal. This suggested that the IR signal determined by the proposed method could potentially correct the faulty bellows signal. The sorted 4D images showed minimal mismatched artefacts and potential clinical applicability. The proposed IR signal therefore provides a feasible alternative to effectively sort MR images in 4D.
4D/RCS: a reference model architecture for intelligent unmanned ground vehicles
NASA Astrophysics Data System (ADS)
Albus, James S.
2002-07-01
4D/RCS consists of a multi-layered multi-resolutional hierarchy of computational nodes each containing elements of sensory processing (SP), world modeling (WM), value judgment (VJ), and behavior generation (BG). At the lower levels, these elements generate goal-seeking reactive behavior. At higher levels, they enable goal-defining deliberative behavior. At low levels, range in space and time is short and resolution is high. At high levels, distance and time are long and resolution is low. This enables high-precision fast-action response over short intervals of time and space at low levels, while long-range plans and abstract concepts are being formulated over broad regions of time and space at high levels. 4D/RCS closes feedback loops at every level. SP processes focus attention (i.e., window regions of space or time), group (i.e., segment regions into entities), compute entity attributes, estimate entity state, and assign entities to classes at every level. WM processes maintain a rich and dynamic database of knowledge about the world in the form of images, maps, entities, events, and relationships at every level. Other WM processes use that knowledge to generate estimates and predictions that support perception, reasoning, and planning at every level. 4D/RCS was developed for the Army Research Laboratory Demo III program. To date, only the lower levels of the 4D/RCS architecture have been fully implemented, but the results have been extremely positive. It seems clear that the theoretical basis of 4D/RCS is sound and the architecture is capable of being extended to support much higher levels of performance.
The dynamical crossover in attractive colloidal systems.
Mallamace, Francesco; Corsaro, Carmelo; Stanley, H Eugene; Mallamace, Domenico; Chen, Sow-Hsin
2013-12-01
We study the dynamical arrest in an adhesive hard-sphere colloidal system. We examine a micellar suspension of the Pluronic-L64 surfactant in the temperature (T) and volume fraction (φ) phase diagram. According to mode-coupling theory (MCT), this system is characterized by a cusp-like singularity and two glassy phases: an attractive glass (AG) phase and a repulsive glass (RG) phase. The T - φ phase diagram of this system as confirmed by a previous series of scattering data also exhibits a Percolation Threshold (PT) line, a reentrant behavior (AG-liquid-RG), and a glass-to-glass transition. The AG phase can be generated out of the liquid phase by using T and φ as control parameters. We utilize viscosity and nuclear magnetic resonance (NMR) techniques. NMR data confirm all the characteristic properties of the colloidal system phase diagram and give evidence of the onset of a fractal-like percolating structure at a precise threshold. The MCT scaling laws used to study the shear viscosity as a function of φ and T show in both cases a fragile-to-strong liquid glass-forming dynamic crossover (FSC) located near the percolation threshold where the clustering process is fully developed. These results suggest a larger thermodynamic generality for this phenomenon, which is usually studied only as a function of the temperature. We also find that the critical values of the control parameters, coincident with the PT line, define the locus of the FSC. In the region between the FSC and the glass transition lines the system dynamics are dominated by clustering effects. We thus demonstrate that it is possible, using the conceptual framework provided by extended mode-coupling theory, to describe the way a system approaches dynamic arrest, taking into account both cage and hopping effects.
The dynamical crossover in attractive colloidal systems
Mallamace, Francesco; Corsaro, Carmelo; Stanley, H. Eugene; Mallamace, Domenico; Chen, Sow-Hsin
2013-12-07
We study the dynamical arrest in an adhesive hard-sphere colloidal system. We examine a micellar suspension of the Pluronic-L64 surfactant in the temperature (T) and volume fraction (ϕ) phase diagram. According to mode-coupling theory (MCT), this system is characterized by a cusp-like singularity and two glassy phases: an attractive glass (AG) phase and a repulsive glass (RG) phase. The T − ϕ phase diagram of this system as confirmed by a previous series of scattering data also exhibits a Percolation Threshold (PT) line, a reentrant behavior (AG-liquid-RG), and a glass-to-glass transition. The AG phase can be generated out of the liquid phase by using T and ϕ as control parameters. We utilize viscosity and nuclear magnetic resonance (NMR) techniques. NMR data confirm all the characteristic properties of the colloidal system phase diagram and give evidence of the onset of a fractal-like percolating structure at a precise threshold. The MCT scaling laws used to study the shear viscosity as a function of ϕ and T show in both cases a fragile-to-strong liquid glass-forming dynamic crossover (FSC) located near the percolation threshold where the clustering process is fully developed. These results suggest a larger thermodynamic generality for this phenomenon, which is usually studied only as a function of the temperature. We also find that the critical values of the control parameters, coincident with the PT line, define the locus of the FSC. In the region between the FSC and the glass transition lines the system dynamics are dominated by clustering effects. We thus demonstrate that it is possible, using the conceptual framework provided by extended mode-coupling theory, to describe the way a system approaches dynamic arrest, taking into account both cage and hopping effects.
Overcoming Dynamic Disturbances in Imaging Systems
NASA Technical Reports Server (NTRS)
Young, Eric W.; Dente, Gregory C.; Lyon, Richard G.; Chesters, Dennis; Gong, Qian
2000-01-01
We develop and discuss a methodology with the potential to yield a significant reduction in complexity, cost, and risk of space-borne optical systems in the presence of dynamic disturbances. More robust systems almost certainly will be a result as well. Many future space-based and ground-based optical systems will employ optical control systems to enhance imaging performance. The goal of the optical control subsystem is to determine the wavefront aberrations and remove them. Ideally reducing an aberrated image of the object under investigation to a sufficiently clear (usually diffraction-limited) image. Control will likely be distributed over several elements. These elements may include telescope primary segments, telescope secondary, telescope tertiary, deformable mirror(s), fine steering mirror(s), etc. The last two elements, in particular, may have to provide dynamic control. These control subsystems may become elaborate indeed. But robust system performance will require evaluation of the image quality over a substantial range and in a dynamic environment. Candidate systems for improvement in the Earth Sciences Enterprise could include next generation Landsat systems or atmospheric sensors for dynamic imaging of individual, severe storms. The technology developed here could have a substantial impact on the development of new systems in the Space Science Enterprise; such as the Next Generation Space Telescope(NGST) and its follow-on the Next NGST. Large Interferometric Systems of non-zero field, such as Planet Finder and Submillimeter Probe of the Evolution of Cosmic Structure, could benefit. These systems most likely will contain large, flexible optormechanical structures subject to dynamic disturbance. Furthermore, large systems for high resolution imaging of planets or the sun from space may also benefit. Tactical and Strategic Defense systems will need to image very small targets as well and could benefit from the technology developed here. We discuss a novel
Overcoming Dynamic Disturbances in Imaging Systems
NASA Technical Reports Server (NTRS)
Young, Eric W.; Dente, Gregory C.; Lyon, Richard G.; Chesters, Dennis; Gong, Qian
2000-01-01
We develop and discuss a methodology with the potential to yield a significant reduction in complexity, cost, and risk of space-borne optical systems in the presence of dynamic disturbances. More robust systems almost certainly will be a result as well. Many future space-based and ground-based optical systems will employ optical control systems to enhance imaging performance. The goal of the optical control subsystem is to determine the wavefront aberrations and remove them. Ideally reducing an aberrated image of the object under investigation to a sufficiently clear (usually diffraction-limited) image. Control will likely be distributed over several elements. These elements may include telescope primary segments, telescope secondary, telescope tertiary, deformable mirror(s), fine steering mirror(s), etc. The last two elements, in particular, may have to provide dynamic control. These control subsystems may become elaborate indeed. But robust system performance will require evaluation of the image quality over a substantial range and in a dynamic environment. Candidate systems for improvement in the Earth Sciences Enterprise could include next generation Landsat systems or atmospheric sensors for dynamic imaging of individual, severe storms. The technology developed here could have a substantial impact on the development of new systems in the Space Science Enterprise; such as the Next Generation Space Telescope(NGST) and its follow-on the Next NGST. Large Interferometric Systems of non-zero field, such as Planet Finder and Submillimeter Probe of the Evolution of Cosmic Structure, could benefit. These systems most likely will contain large, flexible optomechanical structures subject to dynamic disturbance. Furthermore, large systems for high resolution imaging of planets or the sun from space may also benefit. Tactical and Strategic Defense systems will need to image very small targets as well and could benefit from the technology developed here. We discuss a novel
Passive dynamic controllers for nonlinear mechanical systems
NASA Technical Reports Server (NTRS)
Juang, Jer-Nan; Wu, Shih-Chin; Phan, Minh; Longman, Richard W.
1991-01-01
A methodology for model-independant controller design for controlling large angular motion of multi-body dynamic systems is outlined. The controlled system may consist of rigid and flexible components that undergo large rigid body motion and small elastic deformations. Control forces/torques are applied to drive the system and at the same time suppress the vibration due to flexibility of the components. The proposed controller consists of passive second-order systems which may be designed with little knowledge of the system parameter, even if the controlled system is nonlinear. Under rather general assumptions, the passive design assures that the closed loop system has guaranteed stability properties. Unlike positive real controller design, stabilization can be accomplished without direct velocity feedback. In addition, the second-order passive design allows dynamic feedback controllers with considerable freedom to tune for desired system response, and to avoid actuator saturation. After developing the basic mathematical formulation of the design methodology, simulation results are presented to illustrate the proposed approach to a flexible six-degree-of-freedom manipulator.
NASA Astrophysics Data System (ADS)
Davis, Brian; Oberstar, Erick; Royalty, Kevin; Schafer, Sebastian; Strother, Charles; Mistretta, Charles
2015-03-01
Static C-Arm CT 3D FDK baseline reconstructions (3D-DSA) are unable to provide temporal information to radiologists. 4D-DSA provides a time series of 3D volumes implementing a constrained image, thresholded 3D-DSA, reconstruction utilizing temporal dynamics in the 2D projections. Volumetric limiting spatial resolution (VLSR) of 4DDSA is quantified and compared to a 3D-DSA reconstruction using the same 3D-DSA parameters. Investigated were the effects of varying over significant ranges the 4D-DSA parameters of 2D blurring kernel size applied to the projection and threshold applied to the 3D-DSA when generating the constraining image of a scanned phantom (SPH) and an electronic phantom (EPH). The SPH consisted of a 76 micron tungsten wire encased in a 47 mm O.D. plastic radially concentric thin walled support structure. An 8-second/248-frame/198° scan protocol acquired the raw projection data. VLSR was determined from averaged MTF curves generated from each 2D transverse slice of every (248) 4D temporal frame (3D). 4D results for SPH and EPH were compared to the 3D-DSA. Analysis of the 3D-DSA resulted in a VLSR of 2.28 and 1.69 lp/mm for the EPH and SPH respectively. Kernel (2D) sizes of either 10x10 or 20x20 pixels with a threshold of 10% of the 3D-DSA as a constraining image provided 4D-DSA VLSR nearest to the 3D-DSA. 4D-DSA algorithms yielded 2.21 and 1.67 lp/mm with a percent error of 3.1% and 1.2% for the EPH and SPH respectively as compared to the 3D-DSA. This research indicates 4D-DSA is capable of retaining the resolution of the 3D-DSA.
Evans, Elizabeth E; Jonason, Alan S; Bussler, Holm; Torno, Sebold; Veeraraghavan, Janaki; Reilly, Christine; Doherty, Michael A; Seils, Jennifer; Winter, Laurie A; Mallow, Crystal; Kirk, Renee; Howell, Alan; Giralico, Susan; Scrivens, Maria; Klimatcheva, Katya; Fisher, Terrence L; Bowers, William J; Paris, Mark; Smith, Ernest S; Zauderer, Maurice
2015-06-01
Semaphorin 4D (SEMA4D, CD100) and its receptor plexin-B1 (PLXNB1) are broadly expressed in murine and human tumors, and their expression has been shown to correlate with invasive disease in several human tumors. SEMA4D normally functions to regulate the motility and differentiation of multiple cell types, including those of the immune, vascular, and nervous systems. In the setting of cancer, SEMA4D-PLXNB1 interactions have been reported to affect vascular stabilization and transactivation of ERBB2, but effects on immune-cell trafficking in the tumor microenvironment (TME) have not been investigated. We describe a novel immunomodulatory function of SEMA4D, whereby strong expression of SEMA4D at the invasive margins of actively growing tumors influences the infiltration and distribution of leukocytes in the TME. Antibody neutralization of SEMA4D disrupts this gradient of expression, enhances recruitment of activated monocytes and lymphocytes into the tumor, and shifts the balance of cells and cytokines toward a proinflammatory and antitumor milieu within the TME. This orchestrated change in the tumor architecture was associated with durable tumor rejection in murine Colon26 and ERBB2(+) mammary carcinoma models. The immunomodulatory activity of anti-SEMA4D antibody can be enhanced by combination with other immunotherapies, including immune checkpoint inhibition and chemotherapy. Strikingly, the combination of anti-SEMA4D antibody with antibody to CTLA-4 acts synergistically to promote complete tumor rejection and survival. Inhibition of SEMA4D represents a novel mechanism and therapeutic strategy to promote functional immune infiltration into the TME and inhibit tumor progression. PMID:25614511
Evans, Elizabeth E; Jonason, Alan S; Bussler, Holm; Torno, Sebold; Veeraraghavan, Janaki; Reilly, Christine; Doherty, Michael A; Seils, Jennifer; Winter, Laurie A; Mallow, Crystal; Kirk, Renee; Howell, Alan; Giralico, Susan; Scrivens, Maria; Klimatcheva, Katya; Fisher, Terrence L; Bowers, William J; Paris, Mark; Smith, Ernest S; Zauderer, Maurice
2015-06-01
Semaphorin 4D (SEMA4D, CD100) and its receptor plexin-B1 (PLXNB1) are broadly expressed in murine and human tumors, and their expression has been shown to correlate with invasive disease in several human tumors. SEMA4D normally functions to regulate the motility and differentiation of multiple cell types, including those of the immune, vascular, and nervous systems. In the setting of cancer, SEMA4D-PLXNB1 interactions have been reported to affect vascular stabilization and transactivation of ERBB2, but effects on immune-cell trafficking in the tumor microenvironment (TME) have not been investigated. We describe a novel immunomodulatory function of SEMA4D, whereby strong expression of SEMA4D at the invasive margins of actively growing tumors influences the infiltration and distribution of leukocytes in the TME. Antibody neutralization of SEMA4D disrupts this gradient of expression, enhances recruitment of activated monocytes and lymphocytes into the tumor, and shifts the balance of cells and cytokines toward a proinflammatory and antitumor milieu within the TME. This orchestrated change in the tumor architecture was associated with durable tumor rejection in murine Colon26 and ERBB2(+) mammary carcinoma models. The immunomodulatory activity of anti-SEMA4D antibody can be enhanced by combination with other immunotherapies, including immune checkpoint inhibition and chemotherapy. Strikingly, the combination of anti-SEMA4D antibody with antibody to CTLA-4 acts synergistically to promote complete tumor rejection and survival. Inhibition of SEMA4D represents a novel mechanism and therapeutic strategy to promote functional immune infiltration into the TME and inhibit tumor progression.
Coupled Ocean-Atmosphere 4D-Var: Formulation and Sensitivity Analysis Results
NASA Astrophysics Data System (ADS)
Ngodock, Hans; Carrier, Matthew; Xu, Liang; Amerault, Clark; Campbell, Tim; Rowley, Clark
2016-04-01
The US Navy is currently developing the first coupled ocean-atmosphere four-dimensional variational (4D-Var) data assimilation system to be used for short-term regional forecasting. This project merges the 4D-Var capabilities of the atmospheric component of the Coupled Ocean/Atmospheric Mesoscale Prediction System (COAMPS©) with the Navy Coastal Ocean Model (NCOM) through the Earth System Modeling Framework (ESMF). This will provide the coupled ocean-atmosphere forecast with a fully balanced analysis that accounts for all combined observations in both primary fluids (i.e. ocean and atmosphere). In this present work, the formulation of the system is presented in detail along with a series of adjoint sensitivity analysis results using the coupled ocean-atmosphere adjoint model. The sensitivity of the atmosphere (ocean) to each ocean (atmosphere) model variable is analyzed in detail in order to illustrate the usefulness of this approach in the coupled data assimilation system.
Micrographia of the twenty-first century: from camera obscura to 4D microscopy
Zewail, Ahmed H.
2010-01-01
In this paper, the evolutionary and revolutionary developments of microscopic imaging are overviewed with a perspective on origins. From Alhazen’s camera obscura, to Hooke and van Leeuwenhoek’s two-dimensional optical micrography, and on to three- and four-dimensional (4D) electron microscopy, these developments over a millennium have transformed humans’ scope of visualization. The changes in the length and time scales involved are unimaginable, beginning with the visible shadows of candles at the centimetre and second scales, and ending with invisible atoms with space and time dimensions of sub-nanometre and femtosecond. With these advances it has become possible to determine the structures of matter and to observe their elementary dynamics as they unfold in real time. Such observations provide the means for visualizing materials behaviour and biological function, with the aim of understanding emergent phenomena in complex systems. PMID:20123754
Dynamics of vaccination strategies via projected dynamical systems.
Cojocaru, Monica-Gabriela; Bauch, Chris T; Johnston, Matthew D
2007-07-01
Previous game theoretical analyses of vaccinating behaviour have underscored the strategic interaction between individuals attempting to maximise their health states, in situations where an individual's health state depends upon the vaccination decisions of others due to the presence of herd immunity. Here, we extend such analyses by applying the theories of variational inequalities (VI) and projected dynamical systems (PDS) to vaccination games. A PDS provides a dynamics that gives the conditions for existence, uniqueness and stability properties of Nash equilibria. In this paper, it is used to analyse the dynamics of vaccinating behaviour in a population consisting of distinct social groups, where each group has different perceptions of vaccine and disease risks. In particular, we study populations with two groups, where the size of one group is strictly larger than the size of the other group (a majority/minority population). We find that a population with a vaccine-inclined majority group and a vaccine-averse minority group exhibits higher average vaccine coverage than the corresponding homogeneous population, when the vaccine is perceived as being risky relative to the disease. Our model also reproduces a feature of real populations: In certain parameter regimes, it is possible to have a majority group adopting high vaccination rates and simultaneously a vaccine-averse minority group adopting low vaccination rates. Moreover, we find that minority groups will tend to exhibit more extreme changes in vaccinating behaviour for a given change in risk perception, in comparison to majority groups. These results emphasise the important role played by social heterogeneity in vaccination behaviour, while also highlighting the valuable role that can be played by PDS and VI in mathematical epidemiology.
Network Physiology: How Organ Systems Dynamically Interact.
Bartsch, Ronny P; Liu, Kang K L; Bashan, Amir; Ivanov, Plamen Ch
2015-01-01
We systematically study how diverse physiologic systems in the human organism dynamically interact and collectively behave to produce distinct physiologic states and functions. This is a fundamental question in the new interdisciplinary field of Network Physiology, and has not been previously explored. Introducing the novel concept of Time Delay Stability (TDS), we develop a computational approach to identify and quantify networks of physiologic interactions from long-term continuous, multi-channel physiological recordings. We also develop a physiologically-motivated visualization framework to map networks of dynamical organ interactions to graphical objects encoded with information about the coupling strength of network links quantified using the TDS measure. Applying a system-wide integrative approach, we identify distinct patterns in the network structure of organ interactions, as well as the frequency bands through which these interactions are mediated. We establish first maps representing physiologic organ network interactions and discover basic rules underlying the complex hierarchical reorganization in physiologic networks with transitions across physiologic states. Our findings demonstrate a direct association between network topology and physiologic function, and provide new insights into understanding how health and distinct physiologic states emerge from networked interactions among nonlinear multi-component complex systems. The presented here investigations are initial steps in building a first atlas of dynamic interactions among organ systems. PMID:26555073
Network Physiology: How Organ Systems Dynamically Interact
Bartsch, Ronny P.; Liu, Kang K. L.; Bashan, Amir; Ivanov, Plamen Ch.
2015-01-01
We systematically study how diverse physiologic systems in the human organism dynamically interact and collectively behave to produce distinct physiologic states and functions. This is a fundamental question in the new interdisciplinary field of Network Physiology, and has not been previously explored. Introducing the novel concept of Time Delay Stability (TDS), we develop a computational approach to identify and quantify networks of physiologic interactions from long-term continuous, multi-channel physiological recordings. We also develop a physiologically-motivated visualization framework to map networks of dynamical organ interactions to graphical objects encoded with information about the coupling strength of network links quantified using the TDS measure. Applying a system-wide integrative approach, we identify distinct patterns in the network structure of organ interactions, as well as the frequency bands through which these interactions are mediated. We establish first maps representing physiologic organ network interactions and discover basic rules underlying the complex hierarchical reorganization in physiologic networks with transitions across physiologic states. Our findings demonstrate a direct association between network topology and physiologic function, and provide new insights into understanding how health and distinct physiologic states emerge from networked interactions among nonlinear multi-component complex systems. The presented here investigations are initial steps in building a first atlas of dynamic interactions among organ systems. PMID:26555073
Dynamics of Coulombic and gravitational periodic systems.
Kumar, Pankaj; Miller, Bruce N
2016-04-01
We study the dynamics and the phase-space structures of Coulombic and self-gravitating versions of the classical one-dimensional three-body system with periodic boundary conditions. We demonstrate that such a three-body system may be reduced isomorphically to a spatially periodic system of a single particle experiencing a two-dimensional potential on a rhombic plane. For the case of both Coulombic and gravitational versions, exact expressions of the Hamiltonian have been derived in rhombic coordinates. We simulate the phase-space evolution through an event-driven algorithm that utilizes analytic solutions to the equations of motion. The simulation results show that the motion exhibits chaotic, quasiperiodic, and periodic behaviors in segmented regions of the phase space. While there is no evidence of global chaos in either the Coulombic or the gravitational system, the former exhibits a transition from a completely nonchaotic phase space at low energies to a mixed behavior. Gradual yet striking transitions from mild to intense chaos are indicated with changing energy, a behavior that differentiates the spatially periodic systems studied in this Rapid Communication from the well-understood free-boundary versions of the three-body problem. Our treatment of the three-body systems opens avenues for analysis of the dynamical properties exhibited by spatially periodic versions of various classes of systems studied in plasma and gravitational physics as well as in cosmology. PMID:27176238
Dynamics of Coulombic and gravitational periodic systems
NASA Astrophysics Data System (ADS)
Kumar, Pankaj; Miller, Bruce N.
2016-04-01
We study the dynamics and the phase-space structures of Coulombic and self-gravitating versions of the classical one-dimensional three-body system with periodic boundary conditions. We demonstrate that such a three-body system may be reduced isomorphically to a spatially periodic system of a single particle experiencing a two-dimensional potential on a rhombic plane. For the case of both Coulombic and gravitational versions, exact expressions of the Hamiltonian have been derived in rhombic coordinates. We simulate the phase-space evolution through an event-driven algorithm that utilizes analytic solutions to the equations of motion. The simulation results show that the motion exhibits chaotic, quasiperiodic, and periodic behaviors in segmented regions of the phase space. While there is no evidence of global chaos in either the Coulombic or the gravitational system, the former exhibits a transition from a completely nonchaotic phase space at low energies to a mixed behavior. Gradual yet striking transitions from mild to intense chaos are indicated with changing energy, a behavior that differentiates the spatially periodic systems studied in this Rapid Communication from the well-understood free-boundary versions of the three-body problem. Our treatment of the three-body systems opens avenues for analysis of the dynamical properties exhibited by spatially periodic versions of various classes of systems studied in plasma and gravitational physics as well as in cosmology.
4D model generator of the human lung, "Lung4Cer".
Kitaoka, Hiroko; Koc, Salim; Tetsumoto, Satoshi; Koumo, Satoshi; Hirata, Haruhiko; Kijima, Takashi
2013-01-01
We have developed a free software applications which generates 4D (= 3D + time) lung models for the purpose of studying lung anatomy, physiology, and pathophysiology. The coinage of 4C is originated from Japanese words, Catachi (= shape, structure) and Calacli (= machine, function). Lung4Cer makes 4D finite element models from the trachea to alveoli, which allow airflow simulation by means of computational fluid dynamics. Visualization of the generated models is expected to use a popular free software application, ParaView. There are several versions of Lung4Cer from basic lung morphology to advanced airflow computations simulating various clinical pulmonary function tests (PFT4Cer). All versions are designed so as to be operated on a common PC. Users can select model types and the element number according to their purposes and available computer resources.
Crustal evolution of an ore district illustrated - 4D-animation from the Skellefte district, Sweden
NASA Astrophysics Data System (ADS)
Skyttä, Pietari
2012-11-01
This paper exemplifies how the dynamic crustal evolution within geologically complex areas, such as the Palaeoproterozoic VMS-hosting Skellefte district in northern Sweden, may be illustrated by 4D-animations. Furthermore, the paper gives a brief description on how the animation was constructed. The modeled steps through the geological evolution include crustal extension accommodated by normal faults, synchronous volcanism and VMS deposition, block rotations and erosion post-dating the volcanism, deposition of post-volcanic sediments and, finally, inversion of the early normal faults and the related development of upright folds. Specific emphasis is put on illustrating how the originally stratabound VMS sheets were transposed into contrasting geometries depending on erosional features and variations in the tectonic overprint. Summing up, 4D-animations provide a powerful tool for sharing the scientific results and for use in educational purposes.
Bone scaffolds loaded with siRNA-Semaphorin4d for the treatment of osteoporosis related bone defects
Zhang, Yufeng; Wei, Lingfei; Miron, Richard J.; Shi, Bin; Bian, Zhuan
2016-01-01
Osteoporosis is a prominent disorder affecting over 200 million people worldwide. Recently, semaphorins have been implicated in the cell-cell communication between osteoclasts and osteoblasts and have been associated with the progression of osteoporosis. Previously, we demonstrated that knockdown of semaphorin4d (Sema4d) using siRNA delivered with a bone-targeting system prevented bone loss in an osteoporotic animal model. Here, we used this bone-specific technology containing siRNA-Sema4d and fabricated a PLLA scaffold capable of enhancing bone repair following fracture. We investigated the ability of the implant to release siRNA-Sema4d into the surrounding tissues over time and to influence new bone formation in a 3 mm femur osteoporotic defect model in ovariectomized rats. Delivery of the bone-targeting system released from PLLA scaffolds began 2 hours post-implantation, peaked at 1 day, and was sustained over a 21 day period. μCT analysis demonstrated a significantly higher bone volume/total volume bone mineral density and number of osteoblasts in the rats that were transplanted with scaffolds loaded with siRNA-Sema4d. These results confirm the specific role of Sema4d in bone remodeling and demonstrate that significant increases in the speed and quality of new bone formation occur when siRNA-Sema4d is delivered via a PLLA scaffold. PMID:27254469
Dynamically variable spot size laser system
NASA Technical Reports Server (NTRS)
Gradl, Paul R. (Inventor); Hurst, John F. (Inventor); Middleton, James R. (Inventor)
2012-01-01
A Dynamically Variable Spot Size (DVSS) laser system for bonding metal components includes an elongated housing containing a light entry aperture coupled to a laser beam transmission cable and a light exit aperture. A plurality of lenses contained within the housing focus a laser beam from the light entry aperture through the light exit aperture. The lenses may be dynamically adjusted to vary the spot size of the laser. A plurality of interoperable safety devices, including a manually depressible interlock switch, an internal proximity sensor, a remotely operated potentiometer, a remotely activated toggle and a power supply interlock, prevent activation of the laser and DVSS laser system if each safety device does not provide a closed circuit. The remotely operated potentiometer also provides continuous variability in laser energy output.
A dynamical system for interacting flapping swimmers
NASA Astrophysics Data System (ADS)
Oza, Anand; Ramananarivo, Sophie; Ristroph, Leif; Shelley, Michael
2015-11-01
We present the results of a theoretical investigation into the dynamics of interacting flapping swimmers. Our study is motivated by the recent experiments of Becker et al., who studied a one-dimensional array of self-propelled flapping wings that swim within each other's wakes in a water tank. They discovered that the system adopts certain ``schooling modes'' characterized by specific spatial phase relationships between swimmers. To rationalize these phenomena, we develop a discrete dynamical system in which the swimmers are modeled as heaving airfoils that shed point vortices during each flapping cycle. We then apply our model to recent experiments in the Applied Math Lab, in which two tandem flapping airfoils are free to choose both their speed and relative positions. We expect that our model may be used to understand how schooling behavior is influenced by hydrodynamics in more general contexts. Thanks to the NSF for its support.
Systemic risk: the dynamics of model banking systems
May, Robert M.; Arinaminpathy, Nimalan
2010-01-01
The recent banking crises have made it clear that increasingly complex strategies for managing risk in individual banks have not been matched by corresponding attention to overall systemic risks. We explore some simple mathematical caricatures for ‘banking ecosystems’, with emphasis on the interplay between the characteristics of individual banks (capital reserves in relation to total assets, etc.) and the overall dynamical behaviour of the system. The results are discussed in relation to potential regulations aimed at reducing systemic risk. PMID:19864264
Code System for Static and Dynamic Piping System Analysis.
2000-07-07
EPIPE is used for design or design evaluation of complex large piping systems. The piping systems can be viewed as a network of straight pipe elements (or tangents) and curved elements (pipe bends) interconnected at joints (or nodes) with intermediate supports and anchors. The system may be subject to static loads such as thermal, dead weight, internal pressure, or dynamic loads such as earthquake motions and flow-induced vibrations, or any combination of these.
Model-driven physiological assessment of the mitral valve from 4D TEE
NASA Astrophysics Data System (ADS)
Voigt, Ingmar; Ionasec, Razvan Ioan; Georgescu, Bogdan; Houle, Helene; Huber, Martin; Hornegger, Joachim; Comaniciu, Dorin
2009-02-01
Disorders of the mitral valve are second most frequent, cumulating 14 percent of total number of deaths caused by Valvular Heart Disease each year in the United States and require elaborate clinical management. Visual and quantitative evaluation of the valve is an important step in the clinical workflow according to experts as knowledge about mitral morphology and dynamics is crucial for interventional planning. Traditionally this involves examination and metric analysis of 2D images comprising potential errors being intrinsic to the method. Recent commercial solutions are limited to specific anatomic components, pathologies and a single phase of cardiac 4D acquisitions only. This paper introduces a novel approach for morphological and functional quantification of the mitral valve based on a 4D model estimated from ultrasound data. A physiological model of the mitral valve, covering the complete anatomy and eventual shape variations, is generated utilizing parametric spline surfaces constrained by topological and geometrical prior knowledge. The 4D model's parameters are estimated for each patient using the latest discriminative learning and incremental searching techniques. Precise evaluation of the anatomy using model-based dynamic measurements and advanced visualization are enabled through the proposed approach in a reliable, repeatable and reproducible manner. The efficiency and accuracy of the method is demonstrated through experiments and an initial validation based on clinical research results. To the best of our knowledge this is the first time such a patient specific 4D mitral valve model is proposed, covering all of the relevant anatomies and enabling to model the common pathologies at once.
Genome constraint through sexual reproduction: application of 4D-Genomics in reproductive biology.
Horne, Steven D; Abdallah, Batoul Y; Stevens, Joshua B; Liu, Guo; Ye, Karen J; Bremer, Steven W; Heng, Henry H Q
2013-06-01
Assisted reproductive technologies have been used to achieve pregnancies since the first successful test tube baby was born in 1978. Infertile couples are at an increased risk for multiple miscarriages and the application of current protocols are associated with high first-trimester miscarriage rates. Among the contributing factors of these higher rates is a high incidence of fetal aneuploidy. Numerous studies support that protocols including ovulation-induction, sperm cryostorage, density-gradient centrifugation, and embryo culture can induce genome instability, but the general mechanism is less clear. Application of the genome theory and 4D-Genomics recently led to the establishment of a new paradigm for sexual reproduction; sex primarily constrains genome integrity that defines the biological system rather than just providing genetic diversity at the gene level. We therefore propose that application of assisted reproductive technologies can bypass this sexual reproduction filter as well as potentially induce additional system instability. We have previously demonstrated that a single-cell resolution genomic approach, such as spectral karyotyping to trace stochastic genome level alterations, is effective for pre- and post-natal analysis. We propose that monitoring overall genome alteration at the karyotype level alongside the application of assisted reproductive technologies will improve the efficacy of the techniques while limiting stress-induced genome instability. The development of more single-cell based cytogenomic technologies are needed in order to better understand the system dynamics associated with infertility and the potential impact that assisted reproductive technologies have on genome instability. Importantly, this approach will be useful in studying the potential for diseases to arise as a result of bypassing the filter of sexual reproduction.
Entropic Fluctuations in Gaussian Dynamical Systems
NASA Astrophysics Data System (ADS)
Jakšić, V.; Pillet, C.-A.; Shirikyan, A.
2016-06-01
We study nonequilibrium statistical mechanics of a Gaussian dynamical system and compute in closed form the large deviation functionals describing the fluctuations of the entropy production observable with respect to the reference state and the nonequilibrium steady state. The entropy production observable of this model is an unbounded function on the phase space, and its large deviation functionals have a surprisingly rich structure. We explore this structure in some detail.
Tidal Dynamics of Transiting Extrasolar Planetary Systems
NASA Astrophysics Data System (ADS)
Fabrycky, Daniel C.
2008-05-01
The transits of extrasolar planets have revealed a wealth of information about their structures and atmospheres. Because of increased transit likelihood, these planets have small semi-major axes; therefore the planets we know the best are those which are tidally evolved. Transiting planets have not yet been found in multiple-planet systems, but will eventually be an excellent probe of their dynamics. This talk addresses both sides of the coin: theories of tidal dynamics on the one side, clever observations to constrain those theories on the other. On the theory side: Small orbits may be established via eccentricity pumping by a third body (e.g., Kozai cycles) plus tidal dissipation; (b) Oblique spins (Cassini states) may be created and maintained through a secular resonance between orbital precession and spin precession; and (c) Second planets may evolve out of coorbital configurations (near Lagrange points) and mean motion resonance (e.g., the Laplace resonance among Jupiter's satellites) by tidal dissipation. On the observation side: (a) Spectroscopic transit measurements assess the spin orientation of the host star relative to the orbit of the transiting planet; (b) Transit timing measurements can discover second planets and characterize the dynamics of resonant planetary systems; (c) The instantaneous orbital configuration of two-planet systems can indicate the precession rate of the transiting planet, yielding its Love number and probing its internal structure. I gratefully acknowledge funding by the Michelson Fellowship, supported by the National Aeronautics and Space Administration and administered by the Michelson Science Center.
Prediction of dynamical systems by symbolic regression.
Quade, Markus; Abel, Markus; Shafi, Kamran; Niven, Robert K; Noack, Bernd R
2016-07-01
We study the modeling and prediction of dynamical systems based on conventional models derived from measurements. Such algorithms are highly desirable in situations where the underlying dynamics are hard to model from physical principles or simplified models need to be found. We focus on symbolic regression methods as a part of machine learning. These algorithms are capable of learning an analytically tractable model from data, a highly valuable property. Symbolic regression methods can be considered as generalized regression methods. We investigate two particular algorithms, the so-called fast function extraction which is a generalized linear regression algorithm, and genetic programming which is a very general method. Both are able to combine functions in a certain way such that a good model for the prediction of the temporal evolution of a dynamical system can be identified. We illustrate the algorithms by finding a prediction for the evolution of a harmonic oscillator based on measurements, by detecting an arriving front in an excitable system, and as a real-world application, the prediction of solar power production based on energy production observations at a given site together with the weather forecast. PMID:27575130
Prediction of dynamical systems by symbolic regression
NASA Astrophysics Data System (ADS)
Quade, Markus; Abel, Markus; Shafi, Kamran; Niven, Robert K.; Noack, Bernd R.
2016-07-01
We study the modeling and prediction of dynamical systems based on conventional models derived from measurements. Such algorithms are highly desirable in situations where the underlying dynamics are hard to model from physical principles or simplified models need to be found. We focus on symbolic regression methods as a part of machine learning. These algorithms are capable of learning an analytically tractable model from data, a highly valuable property. Symbolic regression methods can be considered as generalized regression methods. We investigate two particular algorithms, the so-called fast function extraction which is a generalized linear regression algorithm, and genetic programming which is a very general method. Both are able to combine functions in a certain way such that a good model for the prediction of the temporal evolution of a dynamical system can be identified. We illustrate the algorithms by finding a prediction for the evolution of a harmonic oscillator based on measurements, by detecting an arriving front in an excitable system, and as a real-world application, the prediction of solar power production based on energy production observations at a given site together with the weather forecast.
Increasingly automated procedure acquisition in dynamic systems
NASA Technical Reports Server (NTRS)
Mathe, Nathalie; Kedar, Smadar
1992-01-01
Procedures are widely used by operators for controlling complex dynamic systems. Currently, most development of such procedures is done manually, consuming a large amount of paper, time, and manpower in the process. While automated knowledge acquisition is an active field of research, not much attention has been paid to the problem of computer-assisted acquisition and refinement of complex procedures for dynamic systems. The Procedure Acquisition for Reactive Control Assistant (PARC), which is designed to assist users in more systematically and automatically encoding and refining complex procedures. PARC is able to elicit knowledge interactively from the user during operation of the dynamic system. We categorize procedure refinement into two stages: diagnosis - diagnose the failure and choose a repair - and repair - plan and perform the repair. The basic approach taken in PARC is to assist the user in all steps of this process by providing increased levels of assistance with layered tools. We illustrate the operation of PARC in refining procedures for the control of a robot arm.
Prediction of dynamical systems by symbolic regression.
Quade, Markus; Abel, Markus; Shafi, Kamran; Niven, Robert K; Noack, Bernd R
2016-07-01
We study the modeling and prediction of dynamical systems based on conventional models derived from measurements. Such algorithms are highly desirable in situations where the underlying dynamics are hard to model from physical principles or simplified models need to be found. We focus on symbolic regression methods as a part of machine learning. These algorithms are capable of learning an analytically tractable model from data, a highly valuable property. Symbolic regression methods can be considered as generalized regression methods. We investigate two particular algorithms, the so-called fast function extraction which is a generalized linear regression algorithm, and genetic programming which is a very general method. Both are able to combine functions in a certain way such that a good model for the prediction of the temporal evolution of a dynamical system can be identified. We illustrate the algorithms by finding a prediction for the evolution of a harmonic oscillator based on measurements, by detecting an arriving front in an excitable system, and as a real-world application, the prediction of solar power production based on energy production observations at a given site together with the weather forecast.
Exome sequencing identifies PDE4D mutations in acrodysostosis.
Lee, Hane; Graham, John M; Rimoin, David L; Lachman, Ralph S; Krejci, Pavel; Tompson, Stuart W; Nelson, Stanley F; Krakow, Deborah; Cohn, Daniel H
2012-04-01
Acrodysostosis is a dominantly-inherited, multisystem disorder characterized by skeletal, endocrine, and neurological abnormalities. To identify the molecular basis of acrodysostosis, we performed exome sequencing on five genetically independent cases. Three different missense mutations in PDE4D, which encodes cyclic AMP (cAMP)-specific phosphodiesterase 4D, were found to be heterozygous in three of the cases. Two of the mutations were demonstrated to have occurred de novo, providing strong genetic evidence of causation. Two additional cases were heterozygous for de novo missense mutations in PRKAR1A, which encodes the cAMP-dependent regulatory subunit of protein kinase A and which has been recently reported to be the cause of a form of acrodysostosis resistant to multiple hormones. These findings demonstrate that acrodysostosis is genetically heterogeneous and underscore the exquisite sensitivity of many tissues to alterations in cAMP homeostasis. PMID:22464252
Brain tissue segmentation in 4D CT using voxel classification
NASA Astrophysics Data System (ADS)
van den Boom, R.; Oei, M. T. H.; Lafebre, S.; Oostveen, L. J.; Meijer, F. J. A.; Steens, S. C. A.; Prokop, M.; van Ginneken, B.; Manniesing, R.
2012-02-01
A method is proposed to segment anatomical regions of the brain from 4D computer tomography (CT) patient data. The method consists of a three step voxel classification scheme, each step focusing on structures that are increasingly difficult to segment. The first step classifies air and bone, the second step classifies vessels and the third step classifies white matter, gray matter and cerebrospinal fluid. As features the time averaged intensity value and the temporal intensity change value were used. In each step, a k-Nearest-Neighbor classifier was used to classify the voxels. Training data was obtained by placing regions of interest in reconstructed 3D image data. The method has been applied to ten 4D CT cerebral patient data. A leave-one-out experiment showed consistent and accurate segmentation results.
4D embryonic cardiography using gated optical coherence tomography
NASA Astrophysics Data System (ADS)
Jenkins, M. W.; Rothenberg, F.; Roy, D.; Nikolski, V. P.; Hu, Z.; Watanabe, M.; Wilson, D. L.; Efimov, I. R.; Rollins, A. M.
2006-01-01
Simultaneous imaging of very early embryonic heart structure and function has technical limitations of spatial and temporal resolution. We have developed a gated technique using optical coherence tomography (OCT) that can rapidly image beating embryonic hearts in four-dimensions (4D), at high spatial resolution (10-15 μm), and with a depth penetration of 1.5 - 2.0 mm that is suitable for the study of early embryonic hearts. We acquired data from paced, excised, embryonic chicken and mouse hearts using gated sampling and employed image processing techniques to visualize the hearts in 4D and measure physiologic parameters such as cardiac volume, ejection fraction, and wall thickness. This technique is being developed to longitudinally investigate the physiology of intact embryonic hearts and events that lead to congenital heart defects.
4D flow cardiovascular magnetic resonance consensus statement.
Dyverfeldt, Petter; Bissell, Malenka; Barker, Alex J; Bolger, Ann F; Carlhäll, Carl-Johan; Ebbers, Tino; Francios, Christopher J; Frydrychowicz, Alex; Geiger, Julia; Giese, Daniel; Hope, Michael D; Kilner, Philip J; Kozerke, Sebastian; Myerson, Saul; Neubauer, Stefan; Wieben, Oliver; Markl, Michael
2015-01-01
Pulsatile blood flow through the cavities of the heart and great vessels is time-varying and multidirectional. Access to all regions, phases and directions of cardiovascular flows has formerly been limited. Four-dimensional (4D) flow cardiovascular magnetic resonance (CMR) has enabled more comprehensive access to such flows, with typical spatial resolution of 1.5×1.5×1.5 - 3×3×3 mm(3), typical temporal resolution of 30-40 ms, and acquisition times in the order of 5 to 25 min. This consensus paper is the work of physicists, physicians and biomedical engineers, active in the development and implementation of 4D Flow CMR, who have repeatedly met to share experience and ideas. The paper aims to assist understanding of acquisition and analysis methods, and their potential clinical applications with a focus on the heart and greater vessels. We describe that 4D Flow CMR can be clinically advantageous because placement of a single acquisition volume is straightforward and enables flow through any plane across it to be calculated retrospectively and with good accuracy. We also specify research and development goals that have yet to be satisfactorily achieved. Derived flow parameters, generally needing further development or validation for clinical use, include measurements of wall shear stress, pressure difference, turbulent kinetic energy, and intracardiac flow components. The dependence of measurement accuracy on acquisition parameters is considered, as are the uses of different visualization strategies for appropriate representation of time-varying multidirectional flow fields. Finally, we offer suggestions for more consistent, user-friendly implementation of 4D Flow CMR acquisition and data handling with a view to multicenter studies and more widespread adoption of the approach in routine clinical investigations. PMID:26257141
Phosphodiesterase 4D gene polymorphisms in sudden sensorineural hearing loss.
Chien, Chen-Yu; Tai, Shu-Yu; Wang, Ling-Feng; Hsi, Edward; Chang, Ning-Chia; Wang, Hsun-Mo; Wu, Ming-Tsang; Ho, Kuen-Yao
2016-09-01
The phosphodiesterase 4D (PDE4D) gene has been reported as a risk gene for ischemic stroke. The vascular factors are between the hypothesized etiologies of sudden sensorineural hearing loss (SSNHL), and this genetic effect might be attributed for its role in SSNHL. We hypothesized that genetic variants of the PDE4D gene are associated with susceptibility to SSNHL. We conducted a case-control study with 362 SSNHL cases and 209 controls. Three single nucleotide polymorphisms (SNPs) were selected. The genotypes were determined using TaqMan technology. Hardy-Weinberg equilibrium (HWE) was tested for each SNP, and genetic effects were evaluated according to three inheritance modes. We carried out sex-specific analysis to analyze the overall data. All three SNPs were in HWE. When subjects were stratified by sex, the genetic effect was only evident in females but not in males. The TT genotype of rs702553 exhibited an adjusted odds ratio (OR) of 3.83 (95 % confidence interval = 1.46-11.18) (p = 0.006) in female SSNHL. The TT genotype of SNP rs702553 was associated with female SSNHL under the recessive model (p = 0.004, OR 3.70). In multivariate logistic regression analysis, TT genotype of rs702553 was significantly associated with female SSNHL (p = 0.0043, OR 3.70). These results suggest that PDE4D gene polymorphisms influence the susceptibility for the development of SSNHL in the southern Taiwanese female population.
Solar System dynamics with the Gaia mission
NASA Astrophysics Data System (ADS)
Hestroffer, D.; Berthier, J.; Carry, B.; David, P.; Lainey, V.; Rambaux, N.; Thuillot, W.; Arlot, J.-E.; Bancelin, D.; Colas, F.; Desmars, J.; Devillepoix, H.; Fouchard, M.; Ivantsov, A.; Kovalenko, I.; Robert, V.
2014-12-01
The Gaia mission is to be launched on December 19th, 2013 by the European Space Agency (ESA). Solar System science is well covered by the mission and has been included since the early stages of its concept and development. We present here some aspects on the astrometry and dynamics of Solar System Objects (SSO) - in particular asteroids, comets and satellites - as well as ground-based support. We also touch upon the future of SSO astrometry that will be achieved indirectly, after mission completion, from the Gaia astrometric catalogue.
Testing relativity with solar system dynamics
NASA Technical Reports Server (NTRS)
Hellings, R. W.
1984-01-01
A major breakthrough is described in the accuracy of Solar System dynamical tests of relativistic gravity. The breakthrough was achieved by factoring in ranging data from Viking Landers 1 and 2 from the surface of Mars. Other key data sources included optical transit circle observations, lunar laser ranging, planetary radar, and spacecraft (Mariner 9 to Mars and Mariner 10 to Mercury). The Solar System model which is used to fit the data and the process by which such fits are performed are explained and results are discussed. The results are fully consistent with the predictions of General Relativity.
Exceptional points in coupled dissipative dynamical systems.
Ryu, Jung-Wan; Son, Woo-Sik; Hwang, Dong-Uk; Lee, Soo-Young; Kim, Sang Wook
2015-05-01
We study the transient behavior in coupled dissipative dynamical systems based on the linear analysis around the steady state. We find that the transient time is minimized at a specific set of system parameters and show that at this parameter set, two eigenvalues and two eigenvectors of the Jacobian matrix coalesce at the same time; this degenerate point is called the exceptional point. For the case of coupled limit-cycle oscillators, we investigate the transient behavior into the amplitude death state, and clarify that the exceptional point is associated with a critical point of frequency locking, as well as the transition of the envelope oscillation.
Soloneski, Sonia; González, Norma V; Reigosa, Miguel A; Larramendy, Marcelo L
2007-11-01
The genotoxic effects of 2,4-D and its commercial derivative 2,4-D DMA were studied by measuring sister chromatid exchange (SCE), cell-cycle progression and mitotic index in human whole blood (WBC) and plasma leukocyte cultures (PLC). Concentrations of 10, 25, 50 and 100 microg herbicide/ml were used during 72 h. In WBC, a significant increase in SCE frequency was observed within the 10-50 microg 2,4-D/ml and 25-100 microg 2,4-D DMA/ml dose range. Contrarily, in PLC, none of the concentrations employed affected the SCEs frequency. A significant delay in cell proliferation was observed in WBC after treatments with 25 and 50 microg 2,4-D/ml and 50 and 100 microg 2,4-D DMA/ml. In PLC, only 100.0 microg 2,4-D/ml altered cell-cycle progression. For both chemicals, a progressive dose-related inhibition of mitotic activity was observed. The results demonstrated that the presence of erythrocytes in the culture system modulated the DNA and cellular damage inflicted by 2,4-D and 2,4-D DMA into human lymphocytes in vitro as well as both 2,4-D and 2,4-D DMA were more potent genotoxic agents in the presence of human red cells.
A 4D Hyperspherical Interpretation of q-Space
Hosseinbor, A. Pasha; Chung, Moo K.; Wu, Yu-Chien; Bendlin, Barbara B.; Alexander, Andrew L.
2015-01-01
3D q-space can be viewed as the surface of a 4D hypersphere. In this paper, we seek to develop a 4D hyperspherical interpretation of q-space by projecting it onto a hypersphere and subsequently modeling the q-space signal via 4D hyperspherical harmonics (HSH). Using this orthonormal basis, we derive several well-established q-space indices and numerically estimate the diffusion orientation distribution function (dODF). We also derive the integral transform describing the relationship between the diffusion signal and propagator on a hypersphere. Most importantly, we will demonstrate that for hybrid diffusion imaging (HYDI) acquisitions low order linear expansion of the HSH basis is sufficient to characterize diffusion in neural tissue. In fact, the HSH basis achieves comparable signal and better dODF reconstructions than other well-established methods, such as Bessel Fourier orientation reconstruction (BFOR), using fewer fitting parameters. All in all, this work provides a new way of looking at q-space. PMID:25624043
4D-Flow validation, numerical and experimental framework
NASA Astrophysics Data System (ADS)
Sansom, Kurt; Liu, Haining; Canton, Gador; Aliseda, Alberto; Yuan, Chun
2015-11-01
This work presents a group of assessment metrics of new 4D MRI flow sequences, an imaging modality that allows for visualization of three-dimensional pulsatile flow in the cardiovascular anatomy through time-resolved three-dimensional blood velocity measurements from cardiac-cycle synchronized MRI acquisition. This is a promising tool for clinical assessment but lacks a robust validation framework. First, 4D-MRI flow in a subject's stenotic carotid bifurcation is compared with a patient-specific CFD model using two different boundary condition methods. Second, Particle Image Velocimetry in a patient-specific phantom is used as a benchmark to compare the 4D-MRI in vivo measurements and CFD simulations under the same conditions. Comparison of estimated and measureable flow parameters such as wall shear stress, fluctuating velocity rms, Lagrangian particle residence time, will be discussed, with justification for their biomechanics relevance and the insights they can provide on the pathophysiology of arterial disease: atherosclerosis and intimal hyperplasia. Lastly, the framework is applied to a new sequence to provide a quantitative assessment. A parametric analysis on the carotid bifurcation pulsatile flow conditions will be presented and an accuracy assessment provided.
[Effects of EDTA on the Reductive Dechlorination of 2,4-D by Pd/Fe].
Zhou, Hong-yi; Nie, Ya-zhong; Chen, Yong; Lei, Shuang-jian
2016-02-15
In Pd/Fe system, zero-valent iron (ZVI) passivation layer is easily formed on the particle surface during the catalytic reductive dechlorination of chlorinated organics, hindering further dechlorination of target contaminants. In this paper, the passivation layer on the Pd/Fe particle surfaces could be eliminated by the chelation of disodium edetate (EDTA) with Fe2+, Fe3+, making the reductive dechlorination continue. The experiment investigated the effects of EDTA addition manner and dosage, pH, Pd loading and temperature on dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) by Pd/Fe. The conclusions can be summarized as follows: (1) Phenoxyacetic acid (PA) generation ratio reached 90. 7% within 20 min with EDTA concentration of 25.0 mmol x L(-1) and flow rate of 20 mL x h(-1), while it was only 74.5% after 210 min in the system without EDTA. (2) The EDTA could chelate the Fe2+ and Fe3+ generated from the process of 2,4-D dechlorination by Pd/Fe, preventing or slowing down the formation of passivation layer, and accelerating the reduction efficiency. (3) The appropriate experimental parameters for 2,4-D removal were as follows: EDTA flow rate of 20 mL x h(-1), CEDTA of 25.0 mmol x L(-1), Pd loading of 0.050%, 200 r x min(-1), pH 4.2 and 30.0 degrees C. The removal percentage of 20.0 mg x L(-1) 2,4-D reached nearly up to 100% within 210 min under these conditions. (4) The intermediates of 2, 4-D catalytic dechlorination included 2-chlorophenoxvacetic acid (2-CPA) and trace 4-chloronhenoxyacetic acid (4-CPA), and the end product was PA.
[Effects of EDTA on the Reductive Dechlorination of 2,4-D by Pd/Fe].
Zhou, Hong-yi; Nie, Ya-zhong; Chen, Yong; Lei, Shuang-jian
2016-02-15
In Pd/Fe system, zero-valent iron (ZVI) passivation layer is easily formed on the particle surface during the catalytic reductive dechlorination of chlorinated organics, hindering further dechlorination of target contaminants. In this paper, the passivation layer on the Pd/Fe particle surfaces could be eliminated by the chelation of disodium edetate (EDTA) with Fe2+, Fe3+, making the reductive dechlorination continue. The experiment investigated the effects of EDTA addition manner and dosage, pH, Pd loading and temperature on dechlorination of 2,4-dichlorophenoxyacetic acid (2,4-D) by Pd/Fe. The conclusions can be summarized as follows: (1) Phenoxyacetic acid (PA) generation ratio reached 90. 7% within 20 min with EDTA concentration of 25.0 mmol x L(-1) and flow rate of 20 mL x h(-1), while it was only 74.5% after 210 min in the system without EDTA. (2) The EDTA could chelate the Fe2+ and Fe3+ generated from the process of 2,4-D dechlorination by Pd/Fe, preventing or slowing down the formation of passivation layer, and accelerating the reduction efficiency. (3) The appropriate experimental parameters for 2,4-D removal were as follows: EDTA flow rate of 20 mL x h(-1), CEDTA of 25.0 mmol x L(-1), Pd loading of 0.050%, 200 r x min(-1), pH 4.2 and 30.0 degrees C. The removal percentage of 20.0 mg x L(-1) 2,4-D reached nearly up to 100% within 210 min under these conditions. (4) The intermediates of 2, 4-D catalytic dechlorination included 2-chlorophenoxvacetic acid (2-CPA) and trace 4-chloronhenoxyacetic acid (4-CPA), and the end product was PA. PMID:27363149
Introduction to Dynamical Systems and Geometric Mechanics
NASA Astrophysics Data System (ADS)
Maruskin, Jared M.
2012-01-01
Introduction to Dynamical Systems and Geometric Mechanics provides a comprehensive tour of two fields that are intimately entwined: dynamical systems is the study of the behavior of physical systems that may be described by a set of nonlinear first-order ordinary differential equations in Euclidean space, whereas geometric mechanics explores similar systems that instead evolve on differentiable manifolds. In the study of geometric mechanics, however, additional geometric structures are often present, since such systems arise from the laws of nature that govern the motions of particles, bodies, and even galaxies. In the first part of the text, we discuss linearization and stability of trajectories and fixed points, invariant manifold theory, periodic orbits, PoincarÃ© maps, Floquet theory, the PoincarÃ©-Bendixson theorem, bifurcations, and chaos. The second part of the text begins with a self-contained chapter on differential geometry that introduces notions of manifolds, mappings, vector fields, the Jacobi-Lie bracket, and differential forms. The final chapters cover Lagrangian and Hamiltonian mechanics from a modern geometric perspective, mechanics on Lie groups, and nonholonomic mechanics via both moving frames and fiber bundle decompositions. The text can be reasonably digested in a single-semester introductory graduate-level course. Each chapter concludes with an application that can serve as a springboard project for further investigation or in-class discussion.
Visualization of system dynamics using phasegrams
Herbst, Christian T.; Herzel, Hanspeter; Švec, Jan G.; Wyman, Megan T.; Fitch, W. Tecumseh
2013-01-01
A new tool for visualization and analysis of system dynamics is introduced: the phasegram. Its application is illustrated with both classical nonlinear systems (logistic map and Lorenz system) and with biological voice signals. Phasegrams combine the advantages of sliding-window analysis (such as the spectrogram) with well-established visualization techniques from the domain of nonlinear dynamics. In a phasegram, time is mapped onto the x-axis, and various vibratory regimes, such as periodic oscillation, subharmonics or chaos, are identified within the generated graph by the number and stability of horizontal lines. A phasegram can be interpreted as a bifurcation diagram in time. In contrast to other analysis techniques, it can be automatically constructed from time-series data alone: no additional system parameter needs to be known. Phasegrams show great potential for signal classification and can act as the quantitative basis for further analysis of oscillating systems in many scientific fields, such as physics (particularly acoustics), biology or medicine. PMID:23697715
Functional Network Dynamics of the Language System
Chai, Lucy R.; Mattar, Marcelo G.; Blank, Idan Asher; Fedorenko, Evelina; Bassett, Danielle S.
2016-01-01
During linguistic processing, a set of brain regions on the lateral surfaces of the left frontal, temporal, and parietal cortices exhibit robust responses. These areas display highly correlated activity while a subject rests or performs a naturalistic language comprehension task, suggesting that they form an integrated functional system. Evidence suggests that this system is spatially and functionally distinct from other systems that support high-level cognition in humans. Yet, how different regions within this system might be recruited dynamically during task performance is not well understood. Here we use network methods, applied to fMRI data collected from 22 human subjects performing a language comprehension task, to reveal the dynamic nature of the language system. We observe the presence of a stable core of brain regions, predominantly located in the left hemisphere, that consistently coactivate with one another. We also observe the presence of a more flexible periphery of brain regions, predominantly located in the right hemisphere, that coactivate with different regions at different times. However, the language functional ROIs in the angular gyrus and the anterior temporal lobe were notable exceptions to this trend. By highlighting the temporal dimension of language processing, these results suggest a trade-off between a region's specialization and its capacity for flexible network reconfiguration. PMID:27550868
Literature Review on Dynamic Cellular Manufacturing System
NASA Astrophysics Data System (ADS)
Nouri Houshyar, A.; Leman, Z.; Pakzad Moghadam, H.; Ariffin, M. K. A. M.; Ismail, N.; Iranmanesh, H.
2014-06-01
In previous decades, manufacturers faced a lot of challenges because of globalization and high competition in markets. These problems arise from shortening product life cycle, rapid variation in demand of products, and also rapid changes in manufcaturing technologies. Nowadays most manufacturing companies expend considerable attention for improving flexibility and responsiveness in order to overcome these kinds of problems and also meet customer's needs. By considering the trend toward the shorter product life cycle, the manufacturing environment is towards manufacturing a wide variety of parts in small batches [1]. One of the major techniques which are applied for improving manufacturing competitiveness is Cellular Manufacturing System (CMS). CMS is type of manufacturing system which tries to combine flexibility of job shop and also productivity of flow shop. In addition, Dynamic cellular manufacturing system which considers different time periods for the manufacturing system becomes an important topic and attracts a lot of attention to itself. Therefore, this paper made attempt to have a brief review on this issue and focused on all published paper on this subject. Although, this topic gains a lot of attention to itself during these years, none of previous researchers focused on reviewing the literature of that which can be helpful and useful for other researchers who intend to do the research on this topic. Therefore, this paper is the first study which has focused and reviewed the literature of dynamic cellular manufacturing system.
Obstacle penetrating dynamic radar imaging system
Romero, Carlos E.; Zumstein, James E.; Chang, John T.; Leach, Jr.. Richard R.
2006-12-12
An obstacle penetrating dynamic radar imaging system for the detection, tracking, and imaging of an individual, animal, or object comprising a multiplicity of low power ultra wideband radar units that produce a set of return radar signals from the individual, animal, or object, and a processing system for said set of return radar signals for detection, tracking, and imaging of the individual, animal, or object. The system provides a radar video system for detecting and tracking an individual, animal, or object by producing a set of return radar signals from the individual, animal, or object with a multiplicity of low power ultra wideband radar units, and processing said set of return radar signals for detecting and tracking of the individual, animal, or object.
Dynamic Analysis of Nuclear Energy System Strategies
2004-06-17
DANESS is an integrated process model for nuclear energy systems allowing the simulation of multiple reactors and fuel cycles in a continuously changing nuclear reactor park configuration. The model is energy demand driven and simulates all nuclear fuel cycle facilites, up to 10 reactors and fuels. Reactor and fuel cycle facility history are traced and the cost of generating energy is calculated per reactor and for total nuclear energy system. The DANESS model aims atmore » performing dynamic systems analysis of nuclear energy development used for integrated analysis of development paths for nuclear energy, parameter scoping for new nuclear energy systems, economic analysis of nuclear energy, government role analysis, and education.« less
Mathematical simulation of Earth system dynamics
NASA Astrophysics Data System (ADS)
Dymnikov, V. P.; Lykosov, V. N.; Volodin, E. M.
2015-05-01
The mathematical simulation of the Earth system, the dynamics of which depends on physical, chemical, biological, and other processes and which requires interdisciplinary approaches to studying this problem, is considered. The term "the Earth system" extends the concept "the climatic system," since additional geospheres (lithosphere, heliosphere, etc.) are taken into account and a wider range of physical, chemical, biological, and social interactions is described. The present-day level of climate modeling is discussed, and some data obtained at the Institute of Numerical Mathematics, Russian Academy of Sciences (INM RAS), are presented for this purpose. The prospects for further development of climate models toward the creation of the Earth system models based on a seamless approach, according to which a unified model is used to make short-term (several days) and long-term (climatic) prediction, are considered.
Dynamically programmable electronic pill dispenser system.
Boquete, Luciano; Rodriguez-Ascariz, Jose Manuel; Artacho, Irene; Cantos-Frontela, Joaquin; Peixoto, Nathalia
2010-06-01
Compliance in medicine dispensation has proven critical for dosage control, diagnosis, and treatment. We have designed, manufactured, and characterized a novel dynamically programmable e-pill dispensing system. Our system is initially programmed remotely through a cell phone. After programming, the system may be reconfigured in order to adapt pill dispensation to new conditions. In this paper we describe the mechanics, electronics, control, and communication protocols implemented. Our dyn-e-pill devices can be actuated for over 350 h with two pill retrievals per hour. We challenged the charging circuit and demonstrated that the system has a lifetime longer than 6 h with a 30 min charging cycle, while it lasts for 14 h of uninterrupted use with a full charge. PMID:20503621
Persistent topological features of dynamical systems.
Maletić, Slobodan; Zhao, Yi; Rajković, Milan
2016-05-01
Inspired by an early work of Muldoon et al., Physica D 65, 1-16 (1993), we present a general method for constructing simplicial complex from observed time series of dynamical systems based on the delay coordinate reconstruction procedure. The obtained simplicial complex preserves all pertinent topological features of the reconstructed phase space, and it may be analyzed from topological, combinatorial, and algebraic aspects. In focus of this study is the computation of homology of the invariant set of some well known dynamical systems that display chaotic behavior. Persistent homology of simplicial complex and its relationship with the embedding dimensions are examined by studying the lifetime of topological features and topological noise. The consistency of topological properties for different dynamic regimes and embedding dimensions is examined. The obtained results shed new light on the topological properties of the reconstructed phase space and open up new possibilities for application of advanced topological methods. The method presented here may be used as a generic method for constructing simplicial complex from a scalar time series that has a number of advantages compared to the mapping of the same time series to a complex network.
Zeno dynamics in quantum open systems
Zhang, Yu-Ran; Fan, Heng
2015-01-01
Quantum Zeno effect shows that frequent observations can slow down or even stop the unitary time evolution of an unstable quantum system. This effect can also be regarded as a physical consequence of the statistical indistinguishability of neighboring quantum states. The accessibility of quantum Zeno dynamics under unitary time evolution can be quantitatively estimated by quantum Zeno time in terms of Fisher information. In this work, we investigate the accessibility of quantum Zeno dynamics in quantum open systems by calculating noisy Fisher information when a trace preserving and completely positive map is assumed. We firstly study the consequences of non-Markovian noise on quantum Zeno effect and give the exact forms of the dissipative Fisher information and the quantum Zeno time. Then, for the operator-sum representation, an achievable upper bound of the quantum Zeno time is given with the help of the results in noisy quantum metrology. It is of significance that the noise reducing the accuracy in the entanglement-enhanced parameter estimation can conversely be favorable for the accessibility of quantum Zeno dynamics of entangled states. PMID:26099840
Computation in Dynamically Bounded Asymmetric Systems
Rutishauser, Ueli; Slotine, Jean-Jacques; Douglas, Rodney
2015-01-01
Previous explanations of computations performed by recurrent networks have focused on symmetrically connected saturating neurons and their convergence toward attractors. Here we analyze the behavior of asymmetrical connected networks of linear threshold neurons, whose positive response is unbounded. We show that, for a wide range of parameters, this asymmetry brings interesting and computationally useful dynamical properties. When driven by input, the network explores potential solutions through highly unstable ‘expansion’ dynamics. This expansion is steered and constrained by negative divergence of the dynamics, which ensures that the dimensionality of the solution space continues to reduce until an acceptable solution manifold is reached. Then the system contracts stably on this manifold towards its final solution trajectory. The unstable positive feedback and cross inhibition that underlie expansion and divergence are common motifs in molecular and neuronal networks. Therefore we propose that very simple organizational constraints that combine these motifs can lead to spontaneous computation and so to the spontaneous modification of entropy that is characteristic of living systems. PMID:25617645
Persistent topological features of dynamical systems
NASA Astrophysics Data System (ADS)
Maletić, Slobodan; Zhao, Yi; Rajković, Milan
2016-05-01
Inspired by an early work of Muldoon et al., Physica D 65, 1-16 (1993), we present a general method for constructing simplicial complex from observed time series of dynamical systems based on the delay coordinate reconstruction procedure. The obtained simplicial complex preserves all pertinent topological features of the reconstructed phase space, and it may be analyzed from topological, combinatorial, and algebraic aspects. In focus of this study is the computation of homology of the invariant set of some well known dynamical systems that display chaotic behavior. Persistent homology of simplicial complex and its relationship with the embedding dimensions are examined by studying the lifetime of topological features and topological noise. The consistency of topological properties for different dynamic regimes and embedding dimensions is examined. The obtained results shed new light on the topological properties of the reconstructed phase space and open up new possibilities for application of advanced topological methods. The method presented here may be used as a generic method for constructing simplicial complex from a scalar time series that has a number of advantages compared to the mapping of the same time series to a complex network.
Zeno dynamics in quantum open systems.
Zhang, Yu-Ran; Fan, Heng
2015-06-23
Quantum Zeno effect shows that frequent observations can slow down or even stop the unitary time evolution of an unstable quantum system. This effect can also be regarded as a physical consequence of the statistical indistinguishability of neighboring quantum states. The accessibility of quantum Zeno dynamics under unitary time evolution can be quantitatively estimated by quantum Zeno time in terms of Fisher information. In this work, we investigate the accessibility of quantum Zeno dynamics in quantum open systems by calculating noisy Fisher information when a trace preserving and completely positive map is assumed. We firstly study the consequences of non-Markovian noise on quantum Zeno effect and give the exact forms of the dissipative Fisher information and the quantum Zeno time. Then, for the operator-sum representation, an achievable upper bound of the quantum Zeno time is given with the help of the results in noisy quantum metrology. It is of significance that the noise reducing the accuracy in the entanglement-enhanced parameter estimation can conversely be favorable for the accessibility of quantum Zeno dynamics of entangled states.
Pseudorotational Dynamics of Small Molecular Systems
NASA Astrophysics Data System (ADS)
Hagelberg, Frank
2001-03-01
A variety of dynamic effects related to the pseudorotation of triatomic singly charged species is explored using the Electron Nuclear Dynamics(END)Theory. The concepts relevant to the motion studied are developed through the analysis of the simplest polyatomic molecule, namely H3+. It is shown that the limiting situation of circular pseudorotation is unattainable for this case. This observation is explained by the anisotropy of the ground state potential energy surface caused by the interaction between the D3h ground state of the molecule and its twofold degenerate first excited state. Further, pseudorotational motion is demonstrated to induce a rotational mode which in turn couples the two shape oscillation modes by action of the Coriolis force. Analogous phenomena are found for Li3+. The Jahn-Teller system C3+ exhibits a range of new motional effects. Particularly, a characteristic frequency shift between the two shape oscillation modes is obtained, resulting from the anisotropy in the curvature of the C2v minimum of C3+. The Jahn-Teller parameters of the system are determined from Electron Nuclear Dynamics simulations.
NASA Astrophysics Data System (ADS)
Hazer, Dilana; Finol, Ender A.; Kostrzewa, Michael; Kopaigorenko, Maria; Richter, Götz-M.; Dillmann, Rüdiger
2009-02-01
Cardiovascular disease results from pathological biomechanical conditions and fatigue of the vessel wall. Image-based computational modeling provides a physical and realistic insight into the patient-specific biomechanics and enables accurate predictive simulations of development, growth and failure of cardiovascular disease. An experimental validation is necessary for the evaluation and the clinical implementation of such computational models. In the present study, we have implemented dynamic Computed-Tomography (4D-CT) imaging and catheter-based in vivo measured pressures to numerically simulate and experimentally evaluate the biomechanics of the porcine aorta. The computations are based on the Finite Element Method (FEM) and simulate the arterial wall response to the transient pressure-based boundary condition. They are evaluated by comparing the numerically predicted wall deformation and that calculated from the acquired 4D-CT data. The dynamic motion of the vessel is quantified by means of the hydraulic diameter, analyzing sequences at 5% increments over the cardiac cycle. Our results show that accurate biomechanical modeling is possible using FEM-based simulations. The RMS error of the computed hydraulic diameter at five cross-sections of the aorta was 0.188, 0.252, 0.280, 0.237 and 0.204 mm, which is equivalent to 1.7%, 2.3%, 2.7%, 2.3% and 2.0%, respectively, when expressed as a function of the time-averaged hydraulic diameter measured from the CT images. The present investigation is a first attempt to simulate and validate vessel deformation based on realistic morphological data and boundary conditions. An experimentally validated system would help in evaluating individual therapies and optimal treatment strategies in the field of minimally invasive endovascular surgery.
A dynamical system view of cerebellar function
NASA Astrophysics Data System (ADS)
Keeler, James D.
1990-06-01
First some previous theories of cerebellar function are reviewed, and deficiencies in how they map onto the neurophysiological structure are pointed out. I hypothesize that the cerebellar cortex builds an internal model, or prediction, of the dynamics of the animal. A class of algorithms for doing prediction based on local reconstruction of attractors are described, and it is shown how this class maps very well onto the structure of the cerebellar cortex. I hypothesize that the climbing fibers multiplex between different trajectories corresponding to different modes of operation. Then the vestibulo-ocular reflex is examined, and experiments to test the proposed model are suggested. The purpose of the presentation here is twofold: (1) To enlighten physiologists to the mathematics of a class of prediction algorithms that map well onto cerebellar architecture. (2) To enlighten dynamical system theorists to the physiological and anatomical details of the cerebellum.
On Mean Field Limits for Dynamical Systems
NASA Astrophysics Data System (ADS)
Boers, Niklas; Pickl, Peter
2016-07-01
We present a purely probabilistic proof of propagation of molecular chaos for N-particle systems in dimension 3 with interaction forces scaling like 1/\\vert q\\vert ^{3λ - 1} with λ smaller but close to one and cut-off at q = N^{-1/3}. The proof yields a Gronwall estimate for the maximal distance between exact microscopic and approximate mean-field dynamics. This can be used to show weak convergence of the one-particle marginals to solutions of the respective mean-field equation without cut-off in a quantitative way. Our results thus lead to a derivation of the Vlasov equation from the microscopic N-particle dynamics with force term arbitrarily close to the physically relevant Coulomb- and gravitational forces.
Robust optimization with transiently chaotic dynamical systems
NASA Astrophysics Data System (ADS)
Sumi, R.; Molnár, B.; Ercsey-Ravasz, M.
2014-05-01
Efficiently solving hard optimization problems has been a strong motivation for progress in analog computing. In a recent study we presented a continuous-time dynamical system for solving the NP-complete Boolean satisfiability (SAT) problem, with a one-to-one correspondence between its stable attractors and the SAT solutions. While physical implementations could offer great efficiency, the transiently chaotic dynamics raises the question of operability in the presence of noise, unavoidable on analog devices. Here we show that the probability of finding solutions is robust to noise intensities well above those present on real hardware. We also developed a cellular neural network model realizable with analog circuits, which tolerates even larger noise intensities. These methods represent an opportunity for robust and efficient physical implementations.
System and mathematical modeling of quadrotor dynamics
NASA Astrophysics Data System (ADS)
Goodman, Jacob M.; Kim, Jinho; Gadsden, S. Andrew; Wilkerson, Stephen A.
2015-05-01
Unmanned aerial systems (UAS) are becoming increasingly visible in our daily lives; and range in operation from search and rescue, monitoring hazardous environments, and to the delivery of goods. One of the most popular UAS are based on a quad-rotor design. These are typically small devices that rely on four propellers for lift and movement. Quad-rotors are inherently unstable, and rely on advanced control methodologies to keep them operating safely and behaving in a predictable and desirable manner. The control of these devices can be enhanced and improved by making use of an accurate dynamic model. In this paper, we examine a simple quadrotor model, and note some of the additional dynamic considerations that were left out. We then compare simulation results of the simple model with that of another comprehensive model.
Dynamically stable magnetic suspension/bearing system
Post, R.F.
1996-02-27
A magnetic bearing system contains magnetic subsystems which act together to support a rotating element in a state of dynamic equilibrium. However, owing to the limitations imposed by Earnshaw`s Theorem, the magnetic bearing systems to be described do not possess a stable equilibrium at zero rotational speed. Therefore, mechanical stabilizers are provided, in each case, to hold the suspended system in equilibrium until its speed has exceeded a low critical speed where dynamic effects take over, permitting the achievement of a stable equilibrium for the rotating object. A state of stable equilibrium is achieved above a critical speed by use of a collection of passive elements using permanent magnets to provide their magnetomotive excitation. The magnetic forces exerted by these elements, when taken together, levitate the rotating object in equilibrium against external forces, such as the force of gravity or forces arising from accelerations. At the same time, this equilibrium is made stable against displacements of the rotating object from its equilibrium position by using combinations of elements that possess force derivatives of such magnitudes and signs that they can satisfy the conditions required for a rotating body to be stably supported by a magnetic bearing system over a finite range of those displacements. 32 figs.
Dynamically stable magnetic suspension/bearing system
Post, Richard F.
1996-01-01
A magnetic bearing system contains magnetic subsystems which act together to support a rotating element in a state of dynamic equilibrium. However, owing to the limitations imposed by Earnshaw's Theorem, the magnetic bearing systems to be described do not possess a stable equilibrium at zero rotational speed. Therefore, mechanical stabilizers are provided, in each case, to hold the suspended system in equilibrium until its speed has exceeded a low critical speed where dynamic effects take over, permitting the achievement of a stable equilibrium for the rotating object. A state of stable equilibrium is achieved above a critical speed by use of a collection of passive elements using permanent magnets to provide their magnetomotive excitation. The magnetic forces exerted by these elements, when taken together, levitate the rotating object in equilibrium against external forces, such as the force of gravity or forces arising from accelerations. At the same time, this equilibrium is made stable against displacements of the rotating object from its equilibrium position by using combinations of elements that possess force derivatives of such magnitudes and signs that they can satisfy the conditions required for a rotating body to be stably supported by a magnetic bearing system over a finite range of those displacements.
Han, Kyu Lee; Webb, Tonya J.
2016-01-01
One of the mechanisms by which malignancies can induce immune suppression is through the production of cytokines that affect the maturation and differentiation of inflammatory cells in the tumor microenvironment. Semaphorin 4D (Sema4D) is a proangiogenic cytokine produced by several malignancies, which has been described in the regulation of the immune system. In the present study, we examined the role of human head and neck squamous cell carcinoma (HNSCC)–secreted Sema4D on myeloid cell differentiation. CD33+ cells cultured in HNSCC cell line–derived conditioned medium differentiated into myeloid derived suppressor cells (MDSC) (CD33+CD11b+HLA-DR−/low). The addition of anti-Sema4D Ab to HNSCC conditioned medium significantly reduced the expansion of the MDSC population. Similarly, knockdown of Sema4D in an HNSCC cell line resulted in a loss of MDSC function as shown by a decrease in the production of the immune-suppressive cytokines arginase-1, TGF-β, and IL-10 by MDSC, concomitant with recovery of T cell proliferation and IFN-γ production following stimulation of CD3/CD28. Importantly, CD33+ myeloid and T cells cultured in conditioned medium of HNSCC cells in which Sema4D was knocked down promoted antitumor inflammatory profile, through recovery of the effector T cells (CD4+T-bet+ and CD8+T-bet+), as well as a decrease in regulatory T cells (CD4+CD25+FOXP3+). We also showed that Sema4D was comparable to GM-CSF in its induction of MDSC. Collectively, this study describes a novel immunosuppressive role for Sema4D in HNSCC through induction of MDSC, and it highlights Sema4D as a therapeutic target for future studies to enhance the antitumorigenic inflammatory response in HNSCC and other epithelial malignancies. PMID:26740106
A dynamical systems view of network centrality
Grindrod, Peter; Higham, Desmond J.
2014-01-01
To gain insights about dynamic networks, the dominant paradigm is to study discrete snapshots, or timeslices, as the interactions evolve. Here, we develop and test a new mathematical framework where network evolution is handled over continuous time, giving an elegant dynamical systems representation for the important concept of node centrality. The resulting system allows us to track the relative influence of each individual. This new setting is natural in many digital applications, offering both conceptual and computational advantages. The novel differential equations approach is convenient for modelling and analysis of network evolution and gives rise to an interesting application of the matrix logarithm function. From a computational perspective, it avoids the awkward up-front compromises between accuracy, efficiency and redundancy required in the prevalent discrete-time setting. Instead, we can rely on state-of-the-art ODE software, where discretization takes place adaptively in response to the prevailing system dynamics. The new centrality system generalizes the widely used Katz measure, and allows us to identify and track, at any resolution, the most influential nodes in terms of broadcasting and receiving information through time-dependent links. In addition to the classical static network notion of attenuation across edges, the new ODE also allows for attenuation over time, as information becomes stale. This allows ‘running measures’ to be computed, so that networks can be monitored in real time over arbitrarily long intervals. With regard to computational efficiency, we explain why it is cheaper to track good receivers of information than good broadcasters. An important consequence is that the overall broadcast activity in the network can also be monitored efficiently. We use two synthetic examples to validate the relevance of the new measures. We then illustrate the ideas on a large-scale voice call network, where key features are discovered that are
Technology reviews: Dynamic curtain wall systems
Schuman, J.; Rubinstein, F.; Papamichael, K.; Beltran, L.; Lee, E.S.; Selkowitz, S.
1992-09-01
We present a representative review of existing, emerging, and future technology options in each of five hardware and systems areas in envelope and lighting technologies: lighting systems, glazing systems, shading systems, daylighting optical systems, and dynamic curtain wall systems. The term technology is used here to describe any design choice for energy efficiency, ranging from individual components to more complex systems to general design strategies. The purpose of this task is to characterize die state of the art in envelope and lighting technologies in order to identify those with promise for advanced integrated systems, with an emphasis on California commercial buildings. For each technology category, the following activities have been attempted to the extent possible: Identify key performance characteristics and criteria for each technology. Determine the performance range of available technologies. Identify the most promising technologies and promising trends in technology advances. Examine market forces and market trends. Develop a continuously growing in-house database to be used throughout the project. A variety of information sources have been used in these technology characterizations, including miscellaneous periodicals, manufacturer catalogs and cut sheets, other research documents, and data from previous computer simulations. We include these different sources in order to best show the type and variety of data available, however publication here does not imply our guarantee of these data. Within each category, several broad classes are identified, and within each class we examine the generic individual technologies that fall into that class.
Description of the grout system dynamic simulation
Zimmerman, B.D.
1993-07-01
The grout system dynamic computer simulation was created to allow investigation of the ability of the grouting system to meet established milestones, for various assumed system configurations and parameters. The simulation simulates the movement of tank waste through the system versus time, from initial storage tanks, through feed tanks and the grout plant, then finally to a grout vault. The simulation properly accounts for the following (1) time required to perform various actions or processes, (2) delays involved in gaining regulatory approval, (3) random system component failures, (4) limitations on equipment capacities, (5) available parallel components, and (6) different possible strategies for vault filling. The user is allowed to set a variety of system parameters for each simulation run. Currently, the output of a run primarily consists of a plot of projected grouting campaigns completed versus time, for comparison with milestones. Other outputs involving any model component can also be quickly created or deleted as desired. In particular, sensitivity runs where the effect of varying a model parameter (flow rates, delay times, number of feed tanks available, etc.) on the ability of the system to meet milestones can be made easily. The grout system simulation was implemented using the ITHINK* simulation language for Macintosh** computers.
Stuart, J.G.; Wright, A.D.; Butterfield, C.P.
1996-10-01
Mitigating the effects of damaging wind turbine loads and responses extends the lifetime of the turbine and, consequently, reduces the associated Cost of Energy (COE). Active control of aerodynamic devices is one option for achieving wind turbine load mitigation. Generally speaking, control system design and analysis requires a reasonable dynamic model of {open_quotes}plant,{close_quotes} (i.e., the system being controlled). This paper extends the wind turbine aileron control research, previously conducted at the National Wind Technology Center (NWTC), by presenting a more detailed development of the wind turbine dynamic model. In prior research, active aileron control designs were implemented in an existing wind turbine structural dynamics code, FAST (Fatigue, Aerodynamics, Structures, and Turbulence). In this paper, the FAST code is used, in conjunction with system identification, to generate a wind turbine dynamic model for use in active aileron control system design. The FAST code is described and an overview of the system identification technique is presented. An aileron control case study is used to demonstrate this modeling technique. The results of the case study are then used to propose ideas for generalizing this technique for creating dynamic models for other wind turbine control applications.
Extensions to Dynamic System Simulation of Fissile Solution Systems
Klein, Steven Karl; Bernardin, John David; Kimpland, Robert Herbert; Spernjak, Dusan
2015-08-24
Previous reports have documented the results of applying dynamic system simulation (DSS) techniques to model a variety of fissile solution systems. The SUPO (Super Power) aqueous homogeneous reactor (AHR) was chosen as the benchmark for comparison of model results to experimental data for steadystate operation.1 Subsequently, DSS was applied to additional AHR to verify results obtained for SUPO and extend modeling to prompt critical excursions, ramp reactivity insertions of various magnitudes and rate, and boiling operations in SILENE and KEWB (Kinetic Experiment Water Boiler).2 Additional models for pressurized cores (HRE: Homogeneous Reactor Experiment), annular core geometries, and accelerator-driven subcritical systems (ADAHR) were developed and results reported.3 The focus of each of these models is core dynamics; neutron kinetics, thermal hydraulics, radiolytic gas generation and transport are coupled to examine the time-based evolution of these systems from start-up through transition to steady-state. A common characteristic of these models is the assumption that (a) core cooling system inlet temperature and flow and (b) plenum gas inlet pressure and flow are held constant; no external (to core) component operations that may result in dynamic change to these parameters are considered. This report discusses extension of models to include explicit reference to cooling structures and radiolytic gas handling. The accelerator-driven subcritical generic system model described in References 3 and 4 is used as a basis for this extension.
Dynamic Systems Analysis for Turbine Based Aero Propulsion Systems
NASA Technical Reports Server (NTRS)
Csank, Jeffrey T.
2016-01-01
The aircraft engine design process seeks to optimize the overall system-level performance, weight, and cost for a given concept. Steady-state simulations and data are used to identify trade-offs that should be balanced to optimize the system in a process known as systems analysis. These systems analysis simulations and data may not adequately capture the true performance trade-offs that exist during transient operation. Dynamic systems analysis provides the capability for assessing the dynamic tradeoffs at an earlier stage of the engine design process. The dynamic systems analysis concept, developed tools, and potential benefit are presented in this paper. To provide this capability, the Tool for Turbine Engine Closed-loop Transient Analysis (TTECTrA) was developed to provide the user with an estimate of the closed-loop performance (response time) and operability (high pressure compressor surge margin) for a given engine design and set of control design requirements. TTECTrA along with engine deterioration information, can be used to develop a more generic relationship between performance and operability that can impact the engine design constraints and potentially lead to a more efficient engine.
Electron Dynamics in Finite Quantum Systems
NASA Astrophysics Data System (ADS)
McDonald, Christopher R.
The multiconfiguration time-dependent Hartree-Fock (MCTDHF) and multiconfiguration time-dependent Hartree (MCTDH) methods are employed to investigate nonperturbative multielectron dynamics in finite quantum systems. MCTDHF is a powerful tool that allows for the investigation of multielectron dynamics in strongly perturbed quantum systems. We have developed an MCTDHF code that is capable of treating problems involving three dimensional (3D) atoms and molecules exposed to strong laser fields. This code will allow for the theoretical treatment of multielectron phenomena in attosecond science that were previously inaccessible. These problems include complex ionization processes in pump-probe experiments on noble gas atoms, the nonlinear effects that have been observed in Ne atoms in the presence of an x-ray free-electron laser (XFEL) and the molecular rearrangement of cations after ionization. An implementation of MCTDH that is optimized for two electrons, each moving in two dimensions (2D), is also presented. This implementation of MCTDH allows for the efficient treatment of 2D spin-free systems involving two electrons; however, it does not scale well to 3D or to systems containing more that two electrons. Both MCTDHF and MCTDH were used to treat 2D problems in nanophysics and attosecond science. MCTDHF is used to investigate plasmon dynamics and the quantum breathing mode for several electrons in finite lateral quantum dots. MCTDHF is also used to study the effects of manipulating the potential of a double lateral quantum dot containing two electrons; applications to quantum computing are discussed. MCTDH is used to examine a diatomic model molecular system exposed to a strong laser field; nonsequential double ionization and high harmonic generation are studied and new processes identified and explained. An implementation of MCTDHF is developed for nonuniform tensor product grids; this will allow for the full 3D implementation of MCTDHF and will provide a means to
Intrinsic information carriers in combinatorial dynamical systems.
Harmer, Russ; Danos, Vincent; Feret, Jérôme; Krivine, Jean; Fontana, Walter
2010-09-01
Many proteins are composed of structural and chemical features--"sites" for short--characterized by definite interaction capabilities, such as noncovalent binding or covalent modification of other proteins. This modularity allows for varying degrees of independence, as the behavior of a site might be controlled by the state of some but not all sites of the ambient protein. Independence quickly generates a startling combinatorial complexity that shapes most biological networks, such as mammalian signaling systems, and effectively prevents their study in terms of kinetic equations-unless the complexity is radically trimmed. Yet, if combinatorial complexity is key to the system's behavior, eliminating it will prevent, not facilitate, understanding. A more adequate representation of a combinatorial system is provided by a graph-based framework of rewrite rules where each rule specifies only the information that an interaction mechanism depends on. Unlike reactions, which deal with molecular species, rules deal with patterns, i.e., multisets of molecular species. Although the stochastic dynamics induced by a collection of rules on a mixture of molecules can be simulated, it appears useful to capture the system's average or deterministic behavior by means of differential equations. However, expansion of the rules into kinetic equations at the level of molecular species is not only impractical, but conceptually indefensible. If rules describe bona fide patterns of interaction, molecular species are unlikely to constitute appropriate units of dynamics. Rather, we must seek aggregate variables reflective of the causal structure laid down by the rules. We call these variables "fragments" and the process of identifying them "fragmentation." Ideally, fragments are aspects of the system's microscopic population that the set of rules can actually distinguish on average; in practice, it may only be feasible to identify an approximation to this. Most importantly, fragments are
Droplet Dynamics of a Flowing Emulsion System
NASA Astrophysics Data System (ADS)
Cypull, Olivia; Feitosa, Klebert
The inner workings of glassy systems have long been a topic of interest for soft material scientists. Similarities between the jamming behavior of emulsions and the glass transition of glassy systems have prompted the conjecture that they might share the same underlying mechanism. Here we study a dense oil-in-water emulsion system forced to flow through a narrow microchannel. By matching the index of refraction of the two phases, we image the internal dynamics of the droplets in a confocal microscope. At low velocity speeds, we find that the velocity along the edge of the microchannel was not significantly different than then the average droplet velocity in the bulk suggesting a near plug flow. By contrast the droplets near the edge experienced more movement perpendicular to the flow indicating the fluidization effect of the confining walls.
Systems approaches to study root architecture dynamics
Cuesta, Candela; Wabnik, Krzysztof; Benková, Eva
2013-01-01
The plant root system is essential for providing anchorage to the soil, supplying minerals and water, and synthesizing metabolites. It is a dynamic organ modulated by external cues such as environmental signals, water and nutrients availability, salinity and others. Lateral roots (LRs) are initiated from the primary root post-embryonically, after which they progress through discrete developmental stages which can be independently controlled, providing a high level of plasticity during root system formation. Within this review, main contributions are presented, from the classical forward genetic screens to the more recent high-throughput approaches, combined with computer model predictions, dissecting how LRs and thereby root system architecture is established and developed. PMID:24421783
Dynamics and Habitability in Binary Star Systems
NASA Astrophysics Data System (ADS)
Eggl, Siegfried; Georgakarakos, Nikolaos; Pilat-Lohinger, Elke
2014-07-01
Determining planetary habitability is a complex matter, as the interplay between a planet's physical and atmospheric properties with stellar insolation has to be studied in a self consistent manner. Standardized atmospheric models for Earth-like planets exist and are commonly accepted as a reference for estimates of Habitable Zones. In order to define Habitable Zone boundaries, circular orbital configurations around main sequence stars are generally assumed. In gravitationally interacting multibody systems, such as double stars, however, planetary orbits are forcibly becoming non circular with time. Especially in binary star systems even relatively small changes in a planet's orbit can have a large impact on habitability. Hence, we argue that a minimum model for calculating Habitable Zones in binary star systems has to include dynamical interactions.
Structural system identification: Structural dynamics model validation
Red-Horse, J.R.
1997-04-01
Structural system identification is concerned with the development of systematic procedures and tools for developing predictive analytical models based on a physical structure`s dynamic response characteristics. It is a multidisciplinary process that involves the ability (1) to define high fidelity physics-based analysis models, (2) to acquire accurate test-derived information for physical specimens using diagnostic experiments, (3) to validate the numerical simulation model by reconciling differences that inevitably exist between the analysis model and the experimental data, and (4) to quantify uncertainties in the final system models and subsequent numerical simulations. The goal of this project was to develop structural system identification techniques and software suitable for both research and production applications in code and model validation.
4D numerical observer for lesion detection in respiratory-gated PET
Lorsakul, Auranuch; Li, Quanzheng; Trott, Cathryn M.; Hoog, Christopher; Petibon, Yoann; Ouyang, Jinsong; Laine, Andrew F.; El Fakhri, Georges
2014-01-01
compared to the conventional 3D approach applied on the nongated and motion-corrected images. Results: On average, the proposed 4D numerical observer improved the detection SNR by 48.6% (p < 0.005), whereas the 3D methods on motion-corrected images improved by 31.0% (p < 0.005) as compared to the nongated method. For all different conditions of the lesions, the relative SNR measurement (Gain = SNRObserved/SNRNongated) of the 4D method was significantly higher than one from the motion-corrected 3D method by 13.8% (p < 0.02), where Gain4D was 1.49 ± 0.21 and Gain3D was 1.31 ± 0.15. For the lesion with the highest amplitude of motion, the 4D numerical observer yielded the highest observer-performance improvement (176%). For the lesion undergoing the smallest motion amplitude, the 4D method provided superior lesion detectability compared with the 3D method, which provided a detection SNR close to the nongated method. The investigation on a structure of the 4D numerical observer showed that a Laguerre–Gaussian channel matrix with a volumetric 3D function yielded higher lesion-detection performance than one with a 2D-stack-channelized function, whereas a different kind of channels that have the ability to mimic the human visual system, i.e., difference-of-Gaussian, showed similar performance in detecting uniform and spherical lesions. The investigation of the detection performance when increasing noise levels yielded decreasing detection SNR by 27.6% and 41.5% for the nongated and gated methods, respectively. The investigation of lesion contrast and diameter showed that the proposed 4D observer preserved the linearity property of an optimal-linear observer while the motion was present. Furthermore, the investigation of the iteration and subset numbers of the OSEM algorithm demonstrated that these parameters had impact on the lesion detectability and the selection of the optimal parameters could provide the maximum lesion-detection performance. The proposed 4D numerical
4D numerical observer for lesion detection in respiratory-gated PET
Lorsakul, Auranuch; Li, Quanzheng; Ouyang, Jinsong; El Fakhri, Georges; Trott, Cathryn M.; Hoog, Christopher; Petibon, Yoann; Laine, Andrew F.
2014-10-15
compared to the conventional 3D approach applied on the nongated and motion-corrected images. Results: On average, the proposed 4D numerical observer improved the detection SNR by 48.6% (p < 0.005), whereas the 3D methods on motion-corrected images improved by 31.0% (p < 0.005) as compared to the nongated method. For all different conditions of the lesions, the relative SNR measurement (Gain = SNR{sub Observed}/SNR{sub Nongated}) of the 4D method was significantly higher than one from the motion-corrected 3D method by 13.8% (p < 0.02), where Gain{sub 4D} was 1.49 ± 0.21 and Gain{sub 3D} was 1.31 ± 0.15. For the lesion with the highest amplitude of motion, the 4D numerical observer yielded the highest observer-performance improvement (176%). For the lesion undergoing the smallest motion amplitude, the 4D method provided superior lesion detectability compared with the 3D method, which provided a detection SNR close to the nongated method. The investigation on a structure of the 4D numerical observer showed that a Laguerre–Gaussian channel matrix with a volumetric 3D function yielded higher lesion-detection performance than one with a 2D-stack-channelized function, whereas a different kind of channels that have the ability to mimic the human visual system, i.e., difference-of-Gaussian, showed similar performance in detecting uniform and spherical lesions. The investigation of the detection performance when increasing noise levels yielded decreasing detection SNR by 27.6% and 41.5% for the nongated and gated methods, respectively. The investigation of lesion contrast and diameter showed that the proposed 4D observer preserved the linearity property of an optimal-linear observer while the motion was present. Furthermore, the investigation of the iteration and subset numbers of the OSEM algorithm demonstrated that these parameters had impact on the lesion detectability and the selection of the optimal parameters could provide the maximum lesion-detection performance. The
Indirect learning control for nonlinear dynamical systems
NASA Technical Reports Server (NTRS)
Ryu, Yeong Soon; Longman, Richard W.
1993-01-01
In a previous paper, learning control algorithms were developed based on adaptive control ideas for linear time variant systems. The learning control methods were shown to have certain advantages over their adaptive control counterparts, such as the ability to produce zero tracking error in time varying systems, and the ability to eliminate repetitive disturbances. In recent years, certain adaptive control algorithms have been developed for multi-body dynamic systems such as robots, with global guaranteed convergence to zero tracking error for the nonlinear system euations. In this paper we study the relationship between such adaptive control methods designed for this specific class of nonlinear systems, and the learning control problem for such systems, seeking to converge to zero tracking error in following a specific command repeatedly, starting from the same initial conditions each time. The extension of these methods from the adaptive control problem to the learning control problem is seen to be trivial. The advantages and disadvantages of using learning control based on such adaptive control concepts for nonlinear systems, and the use of other currently available learning control algorithms are discussed.
VMAT QA: Measurement-guided 4D dose reconstruction on a patient
Nelms, Benjamin E.; Opp, Daniel; Robinson, Joshua; Wolf, Theresa K.; Zhang, Geoffrey; Moros, Eduardo; Feygelman, Vladimir
2012-07-15
Purpose: To develop and validate a volume-modulated arc therapy (VMAT) quality assurance (QA) tool that takes as input a time-resolved, low-density ({approx}10 mm) cylindrical surface dose map from a commercial helical diode array, and outputs a high density, volumetric, time-resolved dose matrix on an arbitrary patient dataset. This first validation study is limited to a homogeneous 'patient.'Methods: A VMAT treatment is delivered to a diode array phantom (ARCCHECK, Sun Nuclear Corp., Melbourne, FL). 3DVH software (Sun Nuclear) derives the high-density volumetric dose using measurement-guided dose reconstruction (MGDR). MGDR cylindrical phantom results are then used to perturb the three-dimensional (3D) treatment planning dose on the patient dataset, producing a semiempirical volumetric dose grid. Four-dimensional (4D) dose reconstruction on the patient is also possible by morphing individual sub-beam doses instead of the composite. For conventional (3D) dose comparison two methods were developed, using the four plans (Multi-Target, C-shape, Mock Prostate, and Head and Neck), including their structures and objectives, from the AAPM TG-119 report. First, 3DVH and treatment planning system (TPS) cumulative point doses were compared to ion chamber in a cube water-equivalent phantom ('patient'). The shape of the phantom is different from the ARCCHECK and furthermore the targets were placed asymmetrically. Second, coronal and sagittal absolute film dose distributions in the cube were compared with 3DVH and TPS. For time-resolved (4D) comparisons, three tests were performed. First, volumetric dose differences were calculated between the 3D MGDR and cumulative time-resolved patient (4D MGDR) dose at the end of delivery, where they ideally should be identical. Second, time-resolved (10 Hz sampling rate) ion chamber doses were compared to cumulative point dose vs time curves from 4D MGDR. Finally, accelerator output was varied to assess the linearity of the 4D MGDR with
Overview of the GRC Stirling Convertor System Dynamic Model
NASA Technical Reports Server (NTRS)
Lewandowski, Edward J.; Regan, Timothy F.
2004-01-01
A Stirling Convertor System Dynamic Model has been developed at the Glenn Research Center for controls, dynamics, and systems development of free-piston convertor power systems. It models the Stirling cycle thermodynamics, heat flow, gas, mechanical, and mounting dynamics, the linear alternator, and the controller. The model's scope extends from the thermal energy input to thermal, mechanical dynamics, and electrical energy out, allowing one to study complex system interactions among subsystems. The model is a non-linear time-domain model containing sub-cycle dynamics, allowing it to simulate transient and dynamic phenomena that other models cannot. The model details and capability are discussed.
Interval modeling of dynamics for multibody systems
NASA Astrophysics Data System (ADS)
Auer, Ekaterina
2007-02-01
Modeling of multibody systems is an important though demanding field of application for interval arithmetic. Interval modeling of dynamics is particularly challenging, not least because of the differential equations which have to be solved in the process. Most modeling tools transform these equations into a (non-autonomous) initial value problem, interval algorithms for solving of which are known. The challenge then consists in finding interfaces between these algorithms and the modeling tools. This includes choosing between "symbolic" and "numerical" modeling environments, transforming the usually non-autonomous resulting system into an autonomous one, ensuring conformity of the new interval version to the old numerical, etc. In this paper, we focus on modeling multibody systems' dynamics with the interval extension of the "numerical" environment MOBILE, discuss the techniques which make the uniform treatment of interval and non-interval modeling easier, comment on the wrapping effect, and give reasons for our choice of MOBILE by comparing the results achieved with its help with those obtained by analogous symbolic tools.
High temporal and high spatial resolution MR angiography (4D-MRA).
Hadizadeh, D R; Marx, C; Gieseke, J; Schild, H H; Willinek, W A
2014-09-01
In the first decade of the twenty-first century, whole-body magnetic resonance scanners with high field strengths (and thus potentially better signal-to-noise ratios) were developed. At the same time, parallel imaging and "echo-sharing" techniques were refined to allow for increasingly high spatial and temporal resolution in dynamic magnetic resonance angiography ("time-resolved" = TR-MRA). This technological progress facilitated tracking the passage of intra-venously administered contrast agent boluses as well as the acquisition of volume data sets at high image refresh rates ("4D-MRA"). This opened doors for many new applications in non-invasive vascular imaging, including simultaneous anatomic and functional analysis of many vascular pathologies including arterio-venous malformations. Different methods were established to acquire 4D-MRA using various strategies to acquire k-space trajectories over time in order to optimize imaging according to clinical needs. These include "keyhole"-based techniques (e. g. 4D-TRAK), TRICKS - both with and without projection - and HYPR-reconstruction, TREAT, and TWIST. Some of these techniques were first introduced in the 1980 s and 1990 s, were later enhanced and modified, and finally implemented in the products of major vendors. In the last decade, a large number of studies on the clinical applications of TR-MRA was published. This manuscript provides an overview of the development of TR-MRA methods and the 4D-MRA techniques as they are currently used in the diagnosis, treatment and follow-up of vascular diseases in various parts of the body. PMID:24955647
Architectural Analysis of Dynamically Reconfigurable Systems
NASA Technical Reports Server (NTRS)
Lindvall, Mikael; Godfrey, Sally; Ackermann, Chris; Ray, Arnab; Yonkwa, Lyly
2010-01-01
oTpics include: the problem (increased flexibility of architectural styles decrease analyzability, behavior emerges and varies depending on the configuration, does the resulting system run according to the intended design, and architectural decisions can impede or facilitate testing); top down approach to architecture analysis, detection of defects and deviations, and architecture and its testability; currently targeted projects GMSEC and CFS; analyzing software architectures; analyzing runtime events; actual architecture recognition; GMPUB in Dynamic SAVE; sample output from new approach; taking message timing delays into account; CFS examples of architecture and testability; some recommendations for improved testablity; and CFS examples of abstract interfaces and testability; CFS example of opening some internal details.
Dynamic data filtering system and method
Bickford, Randall L; Palnitkar, Rahul M
2014-04-29
A computer-implemented dynamic data filtering system and method for selectively choosing operating data of a monitored asset that modifies or expands a learned scope of an empirical model of normal operation of the monitored asset while simultaneously rejecting operating data of the monitored asset that is indicative of excessive degradation or impending failure of the monitored asset, and utilizing the selectively chosen data for adaptively recalibrating the empirical model to more accurately monitor asset aging changes or operating condition changes of the monitored asset.
Rupture dynamics in model polymer systems.
Borah, Rupam; Debnath, Pallavi
2016-05-11
In this paper we explore the rupture dynamics of a model polymer system to capture the microscopic mechanism during relative motion of surfaces at the single polymer level. Our model is similar to the model for friction introduced by Filippov, Klafter, and Urbakh [Filippov et al., Phys. Rev. Lett., 2004, 92, 135503]; but with an important generalization to a flexible transducer (modelled as a bead spring polymer) which is attached to a fixed rigid planar substrate by interconnecting bonds (modelled as harmonic springs), and pulled by a constant force FT. Bonds are allowed to rupture stochastically. The model is simulated, and the results for a certain set of parameters exhibit a sequential rupture mechanism resulting in rupture fronts. A mean field formalism is developed to study these rupture fronts and the possible propagating solutions for the coupled bead and bond dynamics, where the coupling excludes an exact analytical treatment. Numerical solutions to mean field equations are obtained by standard numerical techniques, and they agree well with the simulation results which show sequential rupture. Within a travelling wave formalism based on the Tanh method, we show that the velocity of the rupture front can be obtained in closed form. The derived expression for the rupture front velocity gives good agreement with the stochastic and mean field results, when the rupture is sequential, while propagating solutions for bead and bond dynamics are shown to agree under certain conditions. PMID:27087684
Qualitative theory of p-adic dynamical systems
NASA Astrophysics Data System (ADS)
Zelenov, E. I.
2014-02-01
We consider a class of dynamical systems over the p-adic number field: hierarchical dynamical systems. We prove a strong variant of the Poincaré theorem on the number of returns for such systems and show that hierarchical systems do not admit mixing. We describe hierarchical dynamical systems over the projective line and present an example of a nonhierarchical p-adic system that admits mixing: the p-adic baker's transformation.
4D Proton treatment planning strategy for mobile lung tumors
Kang Yixiu; Zhang Xiaodong; Chang, Joe Y.; Wang He; Wei Xiong; Liao Zhongxing; Komaki, Ritsuko; Cox, James D.; Balter, Peter A.; Liu, Helen; Zhu, X. Ronald; Mohan, Radhe; Dong Lei . E-mail: ldong@mdanderson.org
2007-03-01
Purpose: To investigate strategies for designing compensator-based 3D proton treatment plans for mobile lung tumors using four-dimensional computed tomography (4DCT) images. Methods and Materials: Four-dimensional CT sets for 10 lung cancer patients were used in this study. The internal gross tumor volume (IGTV) was obtained by combining the tumor volumes at different phases of the respiratory cycle. For each patient, we evaluated four planning strategies based on the following dose calculations: (1) the average (AVE) CT; (2) the free-breathing (FB) CT; (3) the maximum intensity projection (MIP) CT; and (4) the AVE CT in which the CT voxel values inside the IGTV were replaced by a constant density (AVE{sub R}IGTV). For each strategy, the resulting cumulative dose distribution in a respiratory cycle was determined using a deformable image registration method. Results: There were dosimetric differences between the apparent dose distribution, calculated on a single CT dataset, and the motion-corrected 4D dose distribution, calculated by combining dose distributions delivered to each phase of the 4DCT. The AVE{sub R}IGTV plan using a 1-cm smearing parameter had the best overall target coverage and critical structure sparing. The MIP plan approach resulted in an unnecessarily large treatment volume. The AVE and FB plans using 1-cm smearing did not provide adequate 4D target coverage in all patients. By using a larger smearing value, adequate 4D target coverage could be achieved; however, critical organ doses were increased. Conclusion: The AVE{sub R}IGTV approach is an effective strategy for designing proton treatment plans for mobile lung tumors.
Phase and amplitude binning for 4D-CT imaging
NASA Astrophysics Data System (ADS)
Abdelnour, A. F.; Nehmeh, S. A.; Pan, T.; Humm, J. L.; Vernon, P.; Schöder, H.; Rosenzweig, K. E.; Mageras, G. S.; Yorke, E.; Larson, S. M.; Erdi, Y. E.
2007-07-01
We compare the consistency and accuracy of two image binning approaches used in 4D-CT imaging. One approach, phase binning (PB), assigns each breathing cycle 2π rad, within which the images are grouped. In amplitude binning (AB), the images are assigned bins according to the breathing signal's full amplitude. To quantitate both approaches we used a NEMA NU2-2001 IEC phantom oscillating in the axial direction and at random frequencies and amplitudes, approximately simulating a patient's breathing. 4D-CT images were obtained using a four-slice GE Lightspeed CT scanner operating in cine mode. We define consistency error as a measure of ability to correctly bin over repeated cycles in the same field of view. Average consistency error μe ± σe in PB ranged from 18% ± 20% to 30% ± 35%, while in AB the error ranged from 11% ± 14% to 20% ± 24%. In PB nearly all bins contained sphere slices. AB was more accurate, revealing empty bins where no sphere slices existed. As a proof of principle, we present examples of two non-small cell lung carcinoma patients' 4D-CT lung images binned by both approaches. While AB can lead to gaps in the coronal images, depending on the patient's breathing pattern, PB exhibits no gaps but suffers visible artifacts due to misbinning, yielding images that cover a relatively large amplitude range. AB was more consistent, though often resulted in gaps when no data existed due to patients' breathing pattern. We conclude AB is more accurate than PB. This has important consequences to treatment planning and diagnosis.
Non-spherical particle generation from 4D optofluidic fabrication.
Paulsen, Kevin S; Chung, Aram J
2016-08-01
Particles with non-spherical shapes can exhibit properties which are not available from spherical shaped particles. Complex shaped particles can provide unique benefits for areas such as drug delivery, tissue engineering, structural materials, and self-assembly building blocks. Current methods of creating complex shaped particles such as 3D printing, photolithography, and imprint lithography are limited by either slow speeds, shape limitations, or expensive processes. Previously, we presented a novel microfluidic flow lithography fabrication scheme combined with fluid inertia called optofluidic fabrication for the creation of complex shaped three-dimensional (3D) particles. This process was able to address the aforementioned limits and overcome two-dimensional shape limitations faced by traditional flow lithography methods; however, all of the created 3D particle shapes displayed top-down symmetry. Here, by introducing the time dimension into our existing optofluidic fabrication process, we break this top-down symmetry, generating fully asymmetric 3D particles where we termed the process: four-dimensional (4D) optofluidic fabrication. This 4D optofluidic fabrication is comprised of three sequential procedures. First, density mismatched precursor fluids flow past pillars within fluidic channels to manipulate the flow cross sections via fluid inertia. Next, the time dimension is incorporated by stopping the flow and allowing the denser fluids to settle by gravity to create asymmetric flow cross sections. Finally, the fluids are exposed to patterned ultraviolet (UV) light in order to polymerize fully asymmetric 3D-shaped particles. By varying inertial flow shaping, gravity-induced flow shaping, and UV light patterns, 4D optofluidic fabrication can create an infinite set of complex shaped asymmetric particles. PMID:27092661
Non-spherical particle generation from 4D optofluidic fabrication.
Paulsen, Kevin S; Chung, Aram J
2016-08-01
Particles with non-spherical shapes can exhibit properties which are not available from spherical shaped particles. Complex shaped particles can provide unique benefits for areas such as drug delivery, tissue engineering, structural materials, and self-assembly building blocks. Current methods of creating complex shaped particles such as 3D printing, photolithography, and imprint lithography are limited by either slow speeds, shape limitations, or expensive processes. Previously, we presented a novel microfluidic flow lithography fabrication scheme combined with fluid inertia called optofluidic fabrication for the creation of complex shaped three-dimensional (3D) particles. This process was able to address the aforementioned limits and overcome two-dimensional shape limitations faced by traditional flow lithography methods; however, all of the created 3D particle shapes displayed top-down symmetry. Here, by introducing the time dimension into our existing optofluidic fabrication process, we break this top-down symmetry, generating fully asymmetric 3D particles where we termed the process: four-dimensional (4D) optofluidic fabrication. This 4D optofluidic fabrication is comprised of three sequential procedures. First, density mismatched precursor fluids flow past pillars within fluidic channels to manipulate the flow cross sections via fluid inertia. Next, the time dimension is incorporated by stopping the flow and allowing the denser fluids to settle by gravity to create asymmetric flow cross sections. Finally, the fluids are exposed to patterned ultraviolet (UV) light in order to polymerize fully asymmetric 3D-shaped particles. By varying inertial flow shaping, gravity-induced flow shaping, and UV light patterns, 4D optofluidic fabrication can create an infinite set of complex shaped asymmetric particles.
Robust segmentation of 4D cardiac MRI-tagged images via spatio-temporal propagation
NASA Astrophysics Data System (ADS)
Qian, Zhen; Huang, Xiaolei; Metaxas, Dimitris N.; Axel, Leon
2005-04-01
In this paper we present a robust method for segmenting and tracking cardiac contours and tags in 4D cardiac MRI tagged images via spatio-temporal propagation. Our method is based on two main techniques: the Metamorphs Segmentation for robust boundary estimation, and the tunable Gabor filter bank for tagging lines enhancement, removal and myocardium tracking. We have developed a prototype system based on the integration of these two techniques, and achieved efficient, robust segmentation and tracking with minimal human interaction.
4D atlas of the mouse embryo for precise morphological staging.
Wong, Michael D; van Eede, Matthijs C; Spring, Shoshana; Jevtic, Stefan; Boughner, Julia C; Lerch, Jason P; Henkelman, R Mark
2015-10-15
After more than a century of research, the mouse remains the gold-standard model system, for it recapitulates human development and disease and is quickly and highly tractable to genetic manipulations. Fundamental to the power and success of using a mouse model is the ability to stage embryonic mouse development accurately. Past staging systems were limited by the technologies of the day, such that only surface features, visible with a light microscope, could be recognized and used to define stages. With the advent of high-throughput 3D imaging tools that capture embryo morphology in microscopic detail, we now present the first 4D atlas staging system for mouse embryonic development using optical projection tomography and image registration methods. By tracking 3D trajectories of every anatomical point in the mouse embryo from E11.5 to E14.0, we established the first 4D atlas compiled from ex vivo 3D mouse embryo reference images. The resulting 4D atlas comprises 51 interpolated 3D images in this gestational range, resulting in a temporal resolution of 72 min. From this 4D atlas, any mouse embryo image can be subsequently compared and staged at the global, voxel and/or structural level. Assigning an embryonic stage to each point in anatomy allows for unprecedented quantitative analysis of developmental asynchrony among different anatomical structures in the same mouse embryo. This comprehensive developmental data set offers developmental biologists a new, powerful staging system that can identify and compare differences in developmental timing in wild-type embryos and shows promise for localizing deviations in mutant development.
Founding Gravitation in 4D Euclidean Space-Time Geometry
Winkler, Franz-Guenter
2010-11-24
The Euclidean interpretation of special relativity which has been suggested by the author is a formulation of special relativity in ordinary 4D Euclidean space-time geometry. The natural and geometrically intuitive generalization of this view involves variations of the speed of light (depending on location and direction) and a Euclidean principle of general covariance. In this article, a gravitation model by Jan Broekaert, which implements a view of relativity theory in the spirit of Lorentz and Poincare, is reconstructed and shown to fulfill the principles of the Euclidean approach after an appropriate reinterpretation.
CMT4D (NDRG1 mutation): genotype-phenotype correlations.
Ricard, Emilie; Mathis, Stéphane; Magdelaine, Corinne; Delisle, Marie-Bernadette; Magy, Laurent; Funalot, Benoît; Vallat, Jean-Michel
2013-09-01
Charcot-Marie-Tooth (CMT) disease is a heterogeneous condition with a large number of clinical, electrophysiological and pathological phenotypes. More than 40 genes are involved. We report a child of gypsy origin with an autosomal recessive demyelinating phenotype. Clinical data, familial history, and electrophysiological studies were in favor of a CMT4 sub-type. The characteristic N-Myc downstream-regulated gene 1 (NDRG1) mutation responsible for this CMT4D phenotype was confirmed: p.R148X. The exact molecular function of the NDRG1 protein has yet to be elucidated.
Multicolor 4D Fluorescence Microscopy using Ultrathin Bessel Light Sheets.
Zhao, Teng; Lau, Sze Cheung; Wang, Ying; Su, Yumian; Wang, Hao; Cheng, Aifang; Herrup, Karl; Ip, Nancy Y; Du, Shengwang; Loy,