Critical Thinking and the Kinesthetic Connection

NASA Technical Reports Server (NTRS)

Shope, R. E., III

1996-01-01

Kinesthetic refers to movement, the movement of the body as it senses its suroundings and respons to its urgings to discover and experience the world...Kinesthetic teaching focuses on instructional approaches that engage the body to integrate concepts, information, thoughts, feelings, and ideas into a coherent structure of knowledge.

Strategy Shifts during Learning from Texts and Pictures

ERIC Educational Resources Information Center

Schnotz, Wolfgang; Ludewig, Ulrich; Ullrich, Mark; Horz, Holger; McElvany, Nele; Baumert, Jürgen

2014-01-01

Reading for learning frequently requires integrating text and picture information into coherent knowledge structures. This article presents an experimental study aimed at analyzing the strategies used by students for integrating text and picture information. Four combinations of texts and pictures (text-picture units) were selected from textbooks…

A scale-based connected coherence tree algorithm for image segmentation.

PubMed

Ding, Jundi; Ma, Runing; Chen, Songcan

2008-02-01

This paper presents a connected coherence tree algorithm (CCTA) for image segmentation with no prior knowledge. It aims to find regions of semantic coherence based on the proposed epsilon-neighbor coherence segmentation criterion. More specifically, with an adaptive spatial scale and an appropriate intensity-difference scale, CCTA often achieves several sets of coherent neighboring pixels which maximize the probability of being a single image content (including kinds of complex backgrounds). In practice, each set of coherent neighboring pixels corresponds to a coherence class (CC). The fact that each CC just contains a single equivalence class (EC) ensures the separability of an arbitrary image theoretically. In addition, the resultant CCs are represented by tree-based data structures, named connected coherence tree (CCT)s. In this sense, CCTA is a graph-based image analysis algorithm, which expresses three advantages: 1) its fundamental idea, epsilon-neighbor coherence segmentation criterion, is easy to interpret and comprehend; 2) it is efficient due to a linear computational complexity in the number of image pixels; 3) both subjective comparisons and objective evaluation have shown that it is effective for the tasks of semantic object segmentation and figure-ground separation in a wide variety of images. Those images either contain tiny, long and thin objects or are severely degraded by noise, uneven lighting, occlusion, poor illumination, and shadow.

Evidence on the coherence-pieces debate from the force concept inventory

NASA Astrophysics Data System (ADS)

Badagnani, D.; Petrucci, D.; Cappannini, O.

2018-01-01

We use force concept inventory (FCI) data to probe the consistency of commonsense physics as a knowledge system. The source of this data is the administration of the FCI to first-year science university students. Data quality was checked using item response theory and studying answer distributions for each question. We find apparently paradoxical results: depending on how the data is analysed, answers seem highly systematic or almost random-like. These results are compatible with others found in the literature and can be construed as arising either from a coherent knowledge system or from knowledge in pieces. We hypothesise as a possible source of this apparent contradiction that predictions and explanations use different resources: the former would use reflex, low-cost cognitive resources while the latter would involve conceptualisations. We show that the articulation of both resources may be crucial for expert thinking productivity (the ability to apply a theory to novel situations). We sketch some consequences of the proposed structure of commonsense thinking for teaching and further research.

What do children know and understand about universal gravitation? Structural and developmental aspects.

PubMed

Frappart, Sören; Raijmakers, Maartje; Frède, Valérie

2014-04-01

Children's understanding of universal gravitation starts at an early age but changes until adulthood, which makes it an interesting topic for studying the development and structure of knowledge. Children's understanding of gravitation was tested for a variety of contexts and across a wide age range (5-18 years, N=144). We analyzed children's predictions and justifications for the trajectory of a stone dropped on the earth, on the moon, in a spaceship orbiting the earth, on a planet with air, on a planet with no air, and in a lift (i.e., an elevator) in free fall. Results showed that performances were related to the context and to the children's age. U-shaped developmental curves were identified for predictions for three contexts. These curves could be explained by analyzing the structure of the children's knowledge using latent class analysis. We identified three coherent patterns of predictions that were related to specific justifications. With age, children produced more scientific predictions. Children's cognitive structures, as reflected in their predictions of dropped stone trajectories, seem to be coherently built given that there were only a limited number of prediction patterns. Even by Grade 12, students had not achieved a scientific understanding of universal gravitation. Copyright © 2013 Elsevier Inc. All rights reserved.

Fiber optic-based optical coherence tomography (OCT) for dental applications

NASA Astrophysics Data System (ADS)

Everett, Matthew J.; Colston, Bill W., Jr.; Da Silva, Luiz B.; Otis, Linda L.

1998-09-01

We have developed a hand-held fiber optic based optical coherence tomography (OCT) system for scanning of the oral cavity. We have produced, using this scanning device, in vivo cross-sectional images of hard and soft dental tissues in human volunteers. Clinically relevant anatomical structures, including the gingival margin, periodontal sulcus, and dento- enamel junction, were visible in all the images. The cemento- enamel junction and the alveolar bone were identified in approximately two thirds of the images. These images represent, or our knowledge, the first in vivo OCT images of human dental tissue.

Management and leadership: analysis of nurse manager's knowledge.

PubMed

Lourenço, Maria Regina; Shinyashiki, Gilberto Tadeu; Trevizan, Maria Auxiliadora

2005-01-01

Nurses have assumed management positions in many health institutions. To properly accomplish the demands of this role, it is important that they be competent in both management and leadership. For appropriate performance, knowledge of management and supervision styles is a priority. Therefore, the goal of this investigation is to identify the nurse manager's knowledge regarding management and leadership. A structured questionnaire containing twenty-seven questions was applied to twelve Brazilian nurse managers of primary care center called "Family Basic Health Units". Data analysis suggested that the nurse manager lower knowledge in management and leadership is related to visionary leadership, management and leadership conceptual differences, leader's behavior, and situational leadership. And, nurse manager greater knowledge is related to power; team work, and coherence between values and attitudes.

Feasibility of spectral-domain phase-sensitive optical coherence tomography for middle ear vibrometry

PubMed Central

Nguyen-Huynh, Anh; Wang, Ruikang K.; Jacques, Steven L.; Choudhury, Niloy; Nuttall, Alfred L.

2012-01-01

Abstract. We describe a novel application of spectral-domain phase-sensitive optical coherence tomography (SD PS-OCT) to detect the tiny motions of the middle ear structures, such as the tympanic membrane and ossicular chain, and their morphological features for differential diagnosis of CHL. This technique has the potential to provide meaningful vibration of ossicles with a vibration sensitivity of ∼0.5  nm at 1 kHz of acoustic stimulation. To the best of our knowledge, this is the first demonstration of depth-resolved vibration imaging of ossicles with a PS-OCT system at a nanometer scale. PMID:22734728

Complete 360° circumferential gonioscopic optical coherence tomography imaging of the iridocorneal angle

PubMed Central

McNabb, Ryan P.; Challa, Pratap; Kuo, Anthony N.; Izatt, Joseph A.

2015-01-01

Clinically, gonioscopy is used to provide en face views of the ocular angle. The angle has been imaged with optical coherence tomography (OCT) through the corneoscleral limbus but is currently unable to image the angle from within the ocular anterior chamber. We developed a novel gonioscopic OCT system that images the angle circumferentially from inside the eye through a custom, radially symmetric, gonioscopic contact lens. We present, to our knowledge, the first 360° circumferential volumes (two normal subjects, two subjects with pathology) of peripheral iris and iridocorneal angle structures obtained via an internal approach not typically available in the clinic. PMID:25909021

Quantitative Imaging of Single Unstained Magnetotactic Bacteria by Coherent X-ray Diffraction Microscopy.

PubMed

Fan, Jiadong; Sun, Zhibin; Zhang, Jian; Huang, Qingjie; Yao, Shengkun; Zong, Yunbing; Kohmura, Yoshiki; Ishikawa, Tetsuya; Liu, Hong; Jiang, Huaidong

2015-06-16

Novel coherent diffraction microscopy provides a powerful lensless imaging method to obtain a better understanding of the microorganism at the nanoscale. Here we demonstrated quantitative imaging of intact unstained magnetotactic bacteria using coherent X-ray diffraction microscopy combined with an iterative phase retrieval algorithm. Although the signal-to-noise ratio of the X-ray diffraction pattern from single magnetotactic bacterium is weak due to low-scattering ability of biomaterials, an 18.6 nm half-period resolution of reconstructed image was achieved by using a hybrid input-output phase retrieval algorithm. On the basis of the quantitative reconstructed images, the morphology and some intracellular structures, such as nucleoid, polyβ-hydroxybutyrate granules, and magnetosomes, were identified, which were also confirmed by scanning electron microscopy and energy dispersive spectroscopy. With the benefit from the quantifiability of coherent diffraction imaging, for the first time to our knowledge, an average density of magnetotactic bacteria was calculated to be ∼1.19 g/cm(3). This technique has a wide range of applications, especially in quantitative imaging of low-scattering biomaterials and multicomponent materials at nanoscale resolution. Combined with the cryogenic technique or X-ray free electron lasers, the method could image cells in a hydrated condition, which helps to maintain their natural structure.

Coherence, competence, and confusion in narratives of middle childhood.

PubMed

Weinstein, Lissa; Shustorovich, Ellen

2011-01-01

Middle childhood is a pivotal time in character development during which enduring internal structures are formed. Fiction can offer insights into the cognitive and affective shifts of this developmental phase and how they are transformed in adulthood. While the success of beloved books for latency age children lies in the solutions they offer to the conflict between the pull toward independence and the pull back to the safety of childhood, the enduring stories for adults about children in their middle years can be seen as works of mourning for the relationship with the parents and the childhood self, but more importantly as attempts to transform their experience of middle childhood through the retrospective creation of a coherence that was initially absent. Thematic and structural elements distinguish two groups of stories for adults: the first appears to solve the conflicts of this period by importing adult knowledge and perspective into the narrative of childhood; the second describes the unconscious disorganizing aspects of this period, thereby offering readers a chance to reorganize their own memories, to make a coherent whole out of the fragmented, the confusing, and the unresolved.

Students' understanding of primary and secondary protein structure: drawing secondary protein structure reveals student understanding better than simple recognition of structures.

PubMed

Harle, Marissa; Towns, Marcy H

2013-01-01

The interdisciplinary nature of biochemistry courses requires students to use both chemistry and biology knowledge to understand biochemical concepts. Research that has focused on external representations in biochemistry has uncovered student difficulties in comprehending and interpreting external representations in addition to a fragmented understanding of fundamental biochemistry concepts. This project focuses on students' understanding of primary and secondary protein structure and drawings (representations) of hydrogen-bonding in alpha helices and beta sheets. Analysis demonstrated that students can recognize and identify primary protein structure concepts when given a polypeptide. However, when asked to draw alpha helices and beta sheets and explain the role of hydrogen bonding their drawings students exhibited a fragmented understanding that lacked coherence. Faculty are encouraged to have students draw molecular level representations to make their mental models more explicit, complete, and coherent. This is in contrast to recognition and identification tasks, which do not adequately probe mental models and molecular level understanding. © 2013 by The International Union of Biochemistry and Molecular Biology.

Event Schemas in Autism Spectrum Disorders: The Role of Theory of Mind and Weak Central Coherence

ERIC Educational Resources Information Center

Loth, Eva; Gomez, Juan Carlos; Happe, Francesca

2008-01-01

Event schemas (generalized knowledge of what happens at common real-life events, e.g., a birthday party) are an important cognitive tool for social understanding: They provide structure for social experiences while accounting for many variable aspects. Using an event narratives task, this study tested the hypotheses that theory of mind (ToM)…

Coherent structures: Comments on mechanisms

NASA Technical Reports Server (NTRS)

Hunt, J. C. R.

1987-01-01

There is now overwhelming evidence that in most turbulent flows there exist regions moving with the flow where the velocity and vorticity have a characteristic structure. These regions are called coherent structures because within them the large-scale distributions of velocity and/or vorticity remain coherent even as these structures move through the flow and interact with other structures. Since the flow enters and leaves the bounding surfaces of these structures, a useful definition for coherent structures is that they are open volumes with distinctive large-scale vorticity distributions. Possible fruitful directions for the study of the dynamics of coherent structures are suggested. Most coherent structures research to data was concentrated on measurement and kinematical analysis; there is now a welcome move to examine the dynamics of coherent structures, by a variety of different methods. A few of them will be described.

Using texts in science education: cognitive processes and knowledge representation.

PubMed

van den Broek, Paul

2010-04-23

Texts form a powerful tool in teaching concepts and principles in science. How do readers extract information from a text, and what are the limitations in this process? Central to comprehension of and learning from a text is the construction of a coherent mental representation that integrates the textual information and relevant background knowledge. This representation engenders learning if it expands the reader's existing knowledge base or if it corrects misconceptions in this knowledge base. The Landscape Model captures the reading process and the influences of reader characteristics (such as working-memory capacity, reading goal, prior knowledge, and inferential skills) and text characteristics (such as content/structure of presented information, processing demands, and textual cues). The model suggests factors that can optimize--or jeopardize--learning science from text.

Automated in vivo 3D high-definition optical coherence tomography skin analysis system.

PubMed

Ai Ping Yow; Jun Cheng; Annan Li; Srivastava, Ruchir; Jiang Liu; Wong, Damon Wing Kee; Hong Liang Tey

2016-08-01

The in vivo assessment and visualization of skin structures can be performed through the use of high resolution optical coherence tomography imaging, also known as HD-OCT. However, the manual assessment of such images can be exhaustive and time consuming. In this paper, we present an analysis system to automatically identify and quantify the skin characteristics such as the topography of the surface of the skin and thickness of the epidermis in HD-OCT images. Comparison of this system with manual clinical measurements demonstrated its potential for automatic objective skin analysis and diseases diagnosis. To our knowledge, this is the first report of an automated system to process and analyse HD-OCT skin images.

Fully Mechanically Controlled Automated Electron Microscopic Tomography

DOE PAGES

Liu, Jinxin; Li, Hongchang; Zhang, Lei; ...

2016-07-11

Knowledge of three-dimensional (3D) structures of each individual particles of asymmetric and flexible proteins is essential in understanding those proteins' functions; but their structures are difficult to determine. Electron tomography (ET) provides a tool for imaging a single and unique biological object from a series of tilted angles, but it is challenging to image a single protein for three-dimensional (3D) reconstruction due to the imperfect mechanical control capability of the specimen goniometer under both a medium to high magnification (approximately 50,000-160,000×) and an optimized beam coherence condition. Here, we report a fully mechanical control method for automating ET data acquisitionmore » without using beam tilt/shift processes. This method could reduce the accumulation of beam tilt/shift that used to compensate the error from the mechanical control, but downgraded the beam coherence. Our method was developed by minimizing the error of the target object center during the tilting process through a closed-loop proportional-integral (PI) control algorithm. The validations by both negative staining (NS) and cryo-electron microscopy (cryo-EM) suggest that this method has a comparable capability to other ET methods in tracking target proteins while maintaining optimized beam coherence conditions for imaging.« less

A Knowledge Discovery framework for Planetary Defense

NASA Astrophysics Data System (ADS)

Jiang, Y.; Yang, C. P.; Li, Y.; Yu, M.; Bambacus, M.; Seery, B.; Barbee, B.

2016-12-01

Planetary Defense, a project funded by NASA Goddard and the NSF, is a multi-faceted effort focused on the mitigation of Near Earth Object (NEO) threats to our planet. Currently, there exists a dispersion of information concerning NEO's amongst different organizations and scientists, leading to a lack of a coherent system of information to be used for efficient NEO mitigation. In this paper, a planetary defense knowledge discovery engine is proposed to better assist the development and integration of a NEO responding system. Specifically, we have implemented an organized information framework by two means: 1) the development of a semantic knowledge base, which provides a structure for relevant information. It has been developed by the implementation of web crawling and natural language processing techniques, which allows us to collect and store the most relevant structured information on a regular basis. 2) the development of a knowledge discovery engine, which allows for the efficient retrieval of information from our knowledge base. The knowledge discovery engine has been built on the top of Elasticsearch, an open source full-text search engine, as well as cutting-edge machine learning ranking and recommendation algorithms. This proposed framework is expected to advance the knowledge discovery and innovation in planetary science domain.

In vivo high resolution human corneal imaging using full-field optical coherence tomography.

PubMed

Mazlin, Viacheslav; Xiao, Peng; Dalimier, Eugénie; Grieve, Kate; Irsch, Kristina; Sahel, José-Alain; Fink, Mathias; Boccara, A Claude

2018-02-01

We present the first full-field optical coherence tomography (FFOCT) device capable of in vivo imaging of the human cornea. We obtained images of the epithelial structures, Bowman's layer, sub-basal nerve plexus (SNP), anterior and posterior stromal keratocytes, stromal nerves, Descemet's membrane and endothelial cells with visible nuclei. Images were acquired with a high lateral resolution of 1.7 µm and relatively large field-of-view of 1.26 mm x 1.26 mm - a combination, which, to the best of our knowledge, has not been possible with other in vivo human eye imaging methods. The latter together with a contactless operation, make FFOCT a promising candidate for becoming a new tool in ophthalmic diagnostics.

The interaction of assessment format and sex in assessing the knowledge structure coherence of middle school students' understanding of the concept of force

NASA Astrophysics Data System (ADS)

Schleigh, Sharon

This study focuses on the impact of assessment format on the identification of students' ideas surrounding the concept of force and the consistency with which students apply those ideas across contexts. It is in response to the debate in conceptual change literature regarding students' knowledge structure coherence. Empirical studies in this field typically rely on an interview assessment format. The current study examined the potential of a constructed response assessment format as another possible instrument for data collection involving larger sample populations. The current study specifically compared how the two assessment formats (constructed response and interview assessment) assessed 45 students in the ninth grade in a single school in Arizona. The analysis explored possible biases and interactions by sex, order of assessment, and preference for assessment format because the literature suggests that these factors may potentially affect the performance and coding of assessments. Although small differences between the two assessments were found, the differences were not statistically significant overall or for any subgroup. More specifically, there were no apparent significant biases in the two formats with regard to one another and student sex. However it was found that girls are more likely to express multiple-best match meanings than boys in both assessments. This may be an influence in the diversity found in previous studies concerning students' knowledge structures. These findings suggest that the constructed response format could be administered on a larger scale to assist in the identification of factors contributing to the differences in findings across prior studies in this field. Additionally, these results suggest the potential of this constructed response format for helping teachers conduct formative assessments to guide instructional decisions.

Aligning the talent pathway: exploring the role and mechanisms of coherence in development.

PubMed

Webb, Vincent; Collins, Dave; Cruickshank, Andrew

2016-10-01

Although our understanding of psychological and social factors in talent development continues to expand, knowledge of the broader system that underpins the entire talent pathways is relatively limited. Indeed, little work has moved beyond the recognition that coherence in this system is important to consider how this may be achieved; particularly in relation to coherent coaching. As such, the aim of this article was to address gaps in talent development and coaching literature and explore principles and potential mechanisms of coherent coaching in sport organisations' talent pathways. After defining and contextualising coherence in whole talent pathways, including barriers to attainment, we discuss how an understanding of coach epistemology can provide a basis for integrating personal and collective coach coherence and therefore a coherent performer experience. With epistemology as our focal point, we then consider how coherent coaching may be supported through the strategic recruitment and placement of coaches, complimentary coach education and development and the use of change agents who can set and shape the coaching milieu, facilitate cross-level communication and enable epistemology-focused reflection and evaluation. Finally, we conclude with some brief recommendations for advancing practically-meaningful knowledge in this important area.

The effect of directive tutor guidance on students' conceptual understanding of statistics in problem-based learning.

PubMed

Budé, Luc; van de Wiel, Margaretha W J; Imbos, Tjaart; Berger, Martijn P F

2011-06-01

Education is aimed at students reaching conceptual understanding of the subject matter, because this leads to better performance and application of knowledge. Conceptual understanding depends on coherent and error-free knowledge structures. The construction of such knowledge structures can only be accomplished through active learning and when new knowledge can be integrated into prior knowledge. The intervention in this study was directed at both the activation of students as well as the integration of knowledge. Undergraduate university students from an introductory statistics course, in an authentic problem-based learning (PBL) environment, were randomly assigned to conditions and measurement time points. In the PBL tutorial meetings, half of the tutors guided the discussions of the students in a traditional way. The other half guided the discussions more actively by asking directive and activating questions. To gauge conceptual understanding, the students answered open-ended questions asking them to explain and relate important statistical concepts. Results of the quantitative analysis show that providing directive tutor guidance improved understanding. Qualitative data of students' misconceptions seem to support this finding. Long-term retention of the subject matter seemed to be inadequate. ©2010 The British Psychological Society.

Semantic and Lexical Coherence.

ERIC Educational Resources Information Center

Fahnestock, Jeanne

Helping students understand coherence in terms of the lexical ties and semantic relations possible between clauses and sentences formalizes an area of writing instruction that has been somewhat vague before and makes the process of creating a coherent paragraph less mysterious. Many students do not have the intuitive knowledge base for absorbing…

In vivo imaging of raptor retina with ultra high resolution spectral domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Ruggeri, Marco; Major, James C., Jr.; McKeown, Craig; Wehbe, Hassan; Jiao, Shuliang; Puliafito, Carmen A.

2008-02-01

Among birds, raptors are well known for their exceptional eyesight, which is partly due to the unique structure of their retina. Because the raptor retina is the most advanced of any animal species, in vivo examination of its structure would be remarkable. Furthermore, a noticeable percentage of traumatic ocular injuries are identified in birds of prey presented to rehabilitation facilities. Injuries affecting the posterior segment have been considered as a major impact on raptor vision. Hence, in vivo examination of the structure of the posterior segment of the raptors would be helpful for the diagnosis of traumatized birds. The purpose of this study is to demonstrate the application of ultrahigh-resolution Spectral Domain Optical Coherence Tomography (SD-OCT) for non contact in vivo imaging of the retina of birds of prey, which to the best of our knowledge has never been attempted. For the first time we present high quality OCT images of the retina of two species of bird of prey, one diurnal hawk and one nocturnal owl.

A microgenetic study of learning about the molecular theory of matter and chemical reactions

NASA Astrophysics Data System (ADS)

Chinn, Clark Allen

This paper reports the results of an experimental microgenetic study of children learning complex knowledge from text and experiments. The study had two goals. The first was to investigate fine-grained, moment-to-moment changes in knowledge as middle-school students learned about molecules and chemical reactions over thirteen sessions. The second was to investigate the effects of two instructional treatments, one using implicit textbook explanations and one using explicit explanations developed according to a theory of how scientific knowledge is structured. In the study, 61 sixth- and seventh-graders worked one on one with undergraduate instructors in eleven sessions of about 50 to 80 minutes. The instructors guided the students in conducting experiments and thinking out loud about texts. Topics studied included molecules, states of matter, chemical reactions, and heat transfer. A dense array of questions provided a detailed picture of children's moment-to-moment and day-to-day changes in knowledge. Three results chapters address students' preinstructional knowledge, the effects of the experimental treatment at posttest, and five detailed case studies of students' step-by-step knowledge change over eleven sessions. The chapter on preinstructional knowledge discussed three aspects of global knowledge change: conceptual change, coherence, and entrenchment. Notably, this chapter provides systematic evidence that children's knowledge was fragmented and that consistency with general unifying principles did not guarantee a highly coherent body of knowledge. The experimental manipulation revealed a strong advantage for explicit explanations over implicit textbook explanations. Multiple explicit explanations (e.g., highly explicit explanations of three or four chemical reactions) appeared to be necessary for students to master key concepts. Microgenetic analyses of five cases addressed eight empirical issues that should be addressed by any theory of knowledge acquisition: (a) the nature of the overall knowledge change, (b) the progression of intermediate states during knowledge change, (c) initiators of knowledge change, (d) interactions of prior background knowledge and prior domain knowledge during knowledge changes, (e) the fate of old and new knowledge, (f) the relationship between belief and knowledge, (g) changes in meta-awareness, and (h) factors that influenced the course of knowledge change.

Identification of individual coherent sets associated with flow trajectories using coherent structure coloring

NASA Astrophysics Data System (ADS)

Schlueter-Kuck, Kristy L.; Dabiri, John O.

2017-09-01

We present a method for identifying the coherent structures associated with individual Lagrangian flow trajectories even where only sparse particle trajectory data are available. The method, based on techniques in spectral graph theory, uses the Coherent Structure Coloring vector and associated eigenvectors to analyze the distance in higher-dimensional eigenspace between a selected reference trajectory and other tracer trajectories in the flow. By analyzing this distance metric in a hierarchical clustering, the coherent structure of which the reference particle is a member can be identified. This algorithm is proven successful in identifying coherent structures of varying complexities in canonical unsteady flows. Additionally, the method is able to assess the relative coherence of the associated structure in comparison to the surrounding flow. Although the method is demonstrated here in the context of fluid flow kinematics, the generality of the approach allows for its potential application to other unsupervised clustering problems in dynamical systems such as neuronal activity, gene expression, or social networks.

A New Perspective on Modeling Groundwater-Driven Health Risk With Subjective Information

NASA Astrophysics Data System (ADS)

Ozbek, M. M.

2003-12-01

Fuzzy rule-based systems provide an efficient environment for the modeling of expert information in the context of risk management for groundwater contamination problems. In general, their use in the form of conditional pieces of knowledge, has been either as a tool for synthesizing control laws from data (i.e., conjunction-based models), or in a knowledge representation and reasoning perspective in Artificial Intelligence (i.e., implication-based models), where only the latter may lead to coherence problems (e.g., input data that leads to logical inconsistency when added to the knowledge base). We implement a two-fold extension to an implication-based groundwater risk model (Ozbek and Pinder, 2002) including: 1) the implementation of sufficient conditions for a coherent knowledge base, and 2) the interpolation of expert statements to supplement gaps in knowledge. The original model assumes statements of public health professionals for the characterization of the exposed individual and the relation of dose and pattern of exposure to its carcinogenic effects. We demonstrate the utility of the extended model in that it: 1)identifies inconsistent statements and establishes coherence in the knowledge base, and 2) minimizes the burden of knowledge elicitation from the experts for utilizing existing knowledge in an optimal fashion.ÿÿ

Strengthening Research by Designing for Coherence and Connections to Practice

ERIC Educational Resources Information Center

Boerst, Timothy; Confrey, Jere; Heck, Daniel; Knuth, Eric; Lambdin, Diana V.; White, Dorothy; Baltzley, Patricia C.; Quander, Judith Reed

2010-01-01

The National Council of Teachers of Mathematics (NCTM) is committed to strengthening relations between research and practice and to the development of a coherent knowledge base that is usable in practice. The need to work toward connection and coherence is not unique to the field of mathematics education. Fields such as medicine, software…

A seismic coherency method using spectral amplitudes

NASA Astrophysics Data System (ADS)

Sui, Jing-Kun; Zheng, Xiao-Dong; Li, Yan-Dong

2015-09-01

Seismic coherence is used to detect discontinuities in underground media. However, strata with steeply dipping structures often produce false low coherence estimates and thus incorrect discontinuity characterization results. It is important to eliminate or reduce the effect of dipping on coherence estimates. To solve this problem, time-domain dip scanning is typically used to improve estimation of coherence in areas with steeply dipping structures. However, the accuracy of the time-domain estimation of dip is limited by the sampling interval. In contrast, the spectrum amplitude is not affected by the time delays in adjacent seismic traces caused by dipping structures. We propose a coherency algorithm that uses the spectral amplitudes of seismic traces within a predefined analysis window to construct the covariance matrix. The coherency estimates with the proposed algorithm is defined as the ratio between the dominant eigenvalue and the sum of all eigenvalues of the constructed covariance matrix. Thus, we eliminate the effect of dipping structures on coherency estimates. In addition, because different frequency bands of spectral amplitudes are used to estimate coherency, the proposed algorithm has multiscale features. Low frequencies are effective for characterizing large-scale faults, whereas high frequencies are better in characterizing small-scale faults. Application to synthetic and real seismic data show that the proposed algorithm can eliminate the effect of dip and produce better coherence estimates than conventional coherency algorithms in areas with steeply dipping structures.

Graph-based urban scene analysis using symbolic data

NASA Astrophysics Data System (ADS)

Moissinac, Henri; Maitre, Henri; Bloch, Isabelle

1995-07-01

A framework is presented for the interpretation of a urban landscape based on the analysis of aerial pictures. This method has been designed for the use of a priori knowledge provided by a geographic map in order to improve the image analysis stage. A coherent final interpretation of the studied area is proposed. It relies on a graph based data structure to modelize the urban landscape, and on a global uncertainty management to evaluate the final confidence we can have in the results presented. This structure and uncertainty management tend to reflect the hierarchy of the available data and the interpretation levels.

Discovering Coherent Structures Using Local Causal States

NASA Astrophysics Data System (ADS)

Rupe, Adam; Crutchfield, James P.; Kashinath, Karthik; Prabhat, Mr.

2017-11-01

Coherent structures were introduced in the study of fluid dynamics and were initially defined as regions characterized by high levels of coherent vorticity, i.e. regions where instantaneously space and phase correlated vorticity are high. In a more general spatiotemporal setting, coherent structures can be seen as localized broken symmetries which persist in time. Building off the computational mechanics framework, which integrates tools from computation and information theory to capture pattern and structure in nonlinear dynamical systems, we introduce a theory of coherent structures, in the more general sense. Central to computational mechanics is the causal equivalence relation, and a local spatiotemporal generalization of it is used to construct the local causal states, which are utilized to uncover a system's spatiotemporal symmetries. Coherent structures are then identified as persistent, localized deviations from these symmetries. We illustrate how novel patterns and structures can be discovered in cellular automata and outline the path from them to laminar, transitional and turbulent flows. Funded by Intel through the Big Data Center at LBNL and the IPCC at UC Davis.

Challenges in Scale-Resolving Simulations of turbulent wake flows with coherent structures

NASA Astrophysics Data System (ADS)

Pereira, Filipe S.; Eça, Luís; Vaz, Guilherme; Girimaji, Sharath S.

2018-06-01

The objective of this work is to investigate the challenges encountered in Scale-Resolving Simulations (SRS) of turbulent wake flows driven by spatially-developing coherent structures. SRS of practical interest are expressly intended for efficiently computing such flows by resolving only the most important features of the coherent structures and modelling the remainder as stochastic field. The success of SRS methods depends upon three important factors: i) ability to identify key flow mechanisms responsible for the generation of coherent structures; ii) determine the optimum range of resolution required to adequately capture key elements of coherent structures; and iii) ensure that the modelled part is comprised nearly exclusively of fully-developed stochastic turbulence. This study considers the canonical case of the flow around a circular cylinder to address the aforementioned three key issues. It is first demonstrated using experimental evidence that the vortex-shedding instability and flow-structure development involves four important stages. A series of SRS computations of progressively increasing resolution (decreasing cut-off length) are performed. An a priori basis for locating the origin of the coherent structures development is proposed and examined. The criterion is based on the fact that the coherent structures are generated by the Kelvin-Helmholtz (KH) instability. The most important finding is that the key aspects of coherent structures can be resolved only if the effective computational Reynolds number (based on total viscosity) exceeds the critical value of the KH instability in laminar flows. Finally, a quantitative criterion assessing the nature of the unresolved field based on the strain-rate ratio of mean and unresolved fields is examined. The two proposed conditions and rationale offer a quantitative basis for developing "good practice" guidelines for SRS of complex turbulent wake flows with coherent structures.

Words and possible words in early language acquisition.

PubMed

Marchetto, Erika; Bonatti, Luca L

2013-11-01

In order to acquire language, infants must extract its building blocks-words-and master the rules governing their legal combinations from speech. These two problems are not independent, however: words also have internal structure. Thus, infants must extract two kinds of information from the same speech input. They must find the actual words of their language. Furthermore, they must identify its possible words, that is, the sequences of sounds that, being morphologically well formed, could be words. Here, we show that infants' sensitivity to possible words appears to be more primitive and fundamental than their ability to find actual words. We expose 12- and 18-month-old infants to an artificial language containing a conflict between statistically coherent and structurally coherent items. We show that 18-month-olds can extract possible words when the familiarization stream contains marks of segmentation, but cannot do so when the stream is continuous. Yet, they can find actual words from a continuous stream by computing statistical relationships among syllables. By contrast, 12-month-olds can find possible words when familiarized with a segmented stream, but seem unable to extract statistically coherent items from a continuous stream that contains minimal conflicts between statistical and structural information. These results suggest that sensitivity to word structure is in place earlier than the ability to analyze distributional information. The ability to compute nontrivial statistical relationships becomes fully effective relatively late in development, when infants have already acquired a considerable amount of linguistic knowledge. Thus, mechanisms for structure extraction that do not rely on extensive sampling of the input are likely to have a much larger role in language acquisition than general-purpose statistical abilities. Copyright © 2013. Published by Elsevier Inc.

Text Coherence in Translation

ERIC Educational Resources Information Center

Zheng, Yanping

2009-01-01

In the thesis a coherent text is defined as a continuity of senses of the outcome of combining concepts and relations into a network composed of knowledge space centered around main topics. And the author maintains that in order to obtain the coherence of a target language text from a source text during the process of translation, a translator can…

Sustaining Tunisian SMEs' Competitiveness in the Knowledge Society

NASA Astrophysics Data System (ADS)

Del Vecchio, Pasquale; Elia, Gianluca; Secundo, Giustina

The paper aims to contribute to the debate about knowledge and digital divide affecting countries' competitiveness in the knowledge society. A survey based on qualitative and quantitative data collection has been performed to analyze the level of ICTs and e-Business adoption of the Tunisian SMEs. The results shows that to increase the SMEs competitiveness is necessary to invest in all the components of Intellectual capital: human capital (knowledge, skills, and the abilities of people for using the ICTs), structural capital (supportive infrastructure such as buildings, software, processes, patents, and trademarks, proprietary databases) and social capital (relations and collaboration inside and outside the company). At this purpose, the LINCET "Laboratoire d'Innovation Numerique pour la Competitivité de l'Entreprise Tunisienne" project is finally proposed as a coherent proposition to foster the growth of all the components of the Intellectual Capital for the benefits of competitiveness of Tunisian SMEs.

Coherent structures shed by multiscale cut-in trailing edge serrations on lifting wings

NASA Astrophysics Data System (ADS)

Prigent, S. L.; Buxton, O. R. H.; Bruce, P. J. K.

2017-07-01

This experimental study presents the effect of multiscale cut-in trailing edge serrations on the coherent structures shed into the wake of a lifting wing. Two-probe span-wise hot-wire traverses are performed to study spectra, coherence, and phase shift. In addition, planar particle image velocimetry is used to study the spatio-temporal structure of the vortices shed by the airfoils. Compared with a single tone sinusoidal serration, the multiscale ones reduce the vortex shedding energy as well as the span-wise coherence. Results indicate that the vortex shedding is locked into an arch-shaped cell structure. This structure is weakened by the multiscale patterns, which explains the reduction in both shedding energy and coherence.

Relaxation, Structure and Properties of Semi-coherent Interfaces

DOE PAGES

Shao, Shuai; Wang, Jian

2015-11-05

Materials containing high density of interfaces are promising candidates for future energy technologies, because interfaces acting as sources, sinks, and barriers for defects can improve mechanical and irradiation properties of materials. Semi-coherent interface widely occurring in various materials is composed of a network of misfit dislocations and coherent regions separated by misfit dislocations. Lastly, in this article, we review relaxation mechanisms, structure and properties of (111) semi-coherent interfaces in face centered cubic structures.

Phylogeny-Based Systematization of Arabidopsis Proteins with Histone H1 Globular Domain1[OPEN

PubMed Central

Knizewski, Lukasz; Schmidt, Anja; Ginalski, Krzysztof

2017-01-01

H1 (or linker) histones are basic nuclear proteins that possess an evolutionarily conserved nucleosome-binding globular domain, GH1. They perform critical functions in determining the accessibility of chromatin DNA to trans-acting factors. In most metazoan species studied so far, linker histones are highly heterogenous, with numerous nonallelic variants cooccurring in the same cells. The phylogenetic relationships among these variants as well as their structural and functional properties have been relatively well established. This contrasts markedly with the rather limited knowledge concerning the phylogeny and structural and functional roles of an unusually diverse group of GH1-containing proteins in plants. The dearth of information and the lack of a coherent phylogeny-based nomenclature of these proteins can lead to misunderstandings regarding their identity and possible relationships, thereby hampering plant chromatin research. Based on published data and our in silico and high-throughput analyses, we propose a systematization and coherent nomenclature of GH1-containing proteins of Arabidopsis (Arabidopsis thaliana [L.] Heynh) that will be useful for both the identification and structural and functional characterization of homologous proteins from other plant species. PMID:28298478

Phylogeny-Based Systematization of Arabidopsis Proteins with Histone H1 Globular Domain.

PubMed

Kotliński, Maciej; Knizewski, Lukasz; Muszewska, Anna; Rutowicz, Kinga; Lirski, Maciej; Schmidt, Anja; Baroux, Célia; Ginalski, Krzysztof; Jerzmanowski, Andrzej

2017-05-01

H1 (or linker) histones are basic nuclear proteins that possess an evolutionarily conserved nucleosome-binding globular domain, GH1. They perform critical functions in determining the accessibility of chromatin DNA to trans-acting factors. In most metazoan species studied so far, linker histones are highly heterogenous, with numerous nonallelic variants cooccurring in the same cells. The phylogenetic relationships among these variants as well as their structural and functional properties have been relatively well established. This contrasts markedly with the rather limited knowledge concerning the phylogeny and structural and functional roles of an unusually diverse group of GH1-containing proteins in plants. The dearth of information and the lack of a coherent phylogeny-based nomenclature of these proteins can lead to misunderstandings regarding their identity and possible relationships, thereby hampering plant chromatin research. Based on published data and our in silico and high-throughput analyses, we propose a systematization and coherent nomenclature of GH1-containing proteins of Arabidopsis ( Arabidopsis thaliana [L.] Heynh) that will be useful for both the identification and structural and functional characterization of homologous proteins from other plant species. © 2017 American Society of Plant Biologists. All Rights Reserved.

Cortical thickness as a contributor to abnormal oscillations in schizophrenia?

PubMed

Edgar, J Christopher; Chen, Yu-Han; Lanza, Matthew; Howell, Breannan; Chow, Vivian Y; Heiken, Kory; Liu, Song; Wootton, Cassandra; Hunter, Michael A; Huang, Mingxiong; Miller, Gregory A; Cañive, José M

2014-01-01

Although brain rhythms depend on brain structure (e.g., gray and white matter), to our knowledge associations between brain oscillations and structure have not been investigated in healthy controls (HC) or in individuals with schizophrenia (SZ). Observing function-structure relationships, for example establishing an association between brain oscillations (defined in terms of amplitude or phase) and cortical gray matter, might inform models on the origins of psychosis. Given evidence of functional and structural abnormalities in primary/secondary auditory regions in SZ, the present study examined how superior temporal gyrus (STG) structure relates to auditory STG low-frequency and 40 Hz steady-state activity. Given changes in brain activity as a function of age, age-related associations in STG oscillatory activity were also examined. Thirty-nine individuals with SZ and 29 HC were recruited. 40 Hz amplitude-modulated tones of 1 s duration were presented. MEG and T1-weighted sMRI data were obtained. Using the sources localizing 40 Hz evoked steady-state activity (300 to 950 ms), left and right STG total power and inter-trial coherence were computed. Time-frequency group differences and associations with STG structure and age were also examined. Decreased total power and inter-trial coherence in SZ were observed in the left STG for initial post-stimulus low-frequency activity (~ 50 to 200 ms, ~ 4 to 16 Hz) as well as 40 Hz steady-state activity (~ 400 to 1000 ms). Left STG 40 Hz total power and inter-trial coherence were positively associated with left STG cortical thickness in HC, not in SZ. Left STG post-stimulus low-frequency and 40 Hz total power were positively associated with age, again only in controls. Left STG low-frequency and steady-state gamma abnormalities distinguish SZ and HC. Disease-associated damage to STG gray matter in schizophrenia may disrupt the age-related left STG gamma-band function-structure relationships observed in controls.

Buzzwords and newspeak

NASA Astrophysics Data System (ADS)

Swartz, Clifford E.

2000-03-01

You have to read beneath the lines in this business. Every week I get manuscripts filled with words and phrases fraught with cabalistic meaning. Would you believe, for instance, that in using the modeling method of teaching that the carefully structured development and concept flow would lead through Socratic dialogue to a rich classroom discourse? Perhaps it would help if I reminded you that a model is a primary unit of coherently structured knowledge. Of course, I am speaking only of the essence of models that are at the heart of modeling theory. These depend on student-centered teaching that is research-informed, leading to interactive engagement methods and cooperative learning.

Method and apparatus for efficiently tracking queue entries relative to a timestamp

DOEpatents

Blumrich, Matthias A.; Chen, Dong; Gara, Alan G.; Giampapa, Mark E.; Heidelberger, Philip; Ohmacht, Martin; Salapura, Velentina; Vranas, Pavlos

2014-06-17

An apparatus and method for tracking coherence event signals transmitted in a multiprocessor system. The apparatus comprises a coherence logic unit, each unit having a plurality of queue structures with each queue structure associated with a respective sender of event signals transmitted in the system. A timing circuit associated with a queue structure controls enqueuing and dequeuing of received coherence event signals, and, a counter tracks a number of coherence event signals remaining enqueued in the queue structure and dequeued since receipt of a timestamp signal. A counter mechanism generates an output signal indicating that all of the coherence event signals present in the queue structure at the time of receipt of the timestamp signal have been dequeued. In one embodiment, the timestamp signal is asserted at the start of a memory synchronization operation and, the output signal indicates that all coherence events present when the timestamp signal was asserted have completed. This signal can then be used as part of the completion condition for the memory synchronization operation.

The coherence of synthetic telomeres.

PubMed Central

Acevedo, O L; Dickinson, L A; Macke, T J; Thomas, C A

1991-01-01

The chromosomal telomeres of Oxytricha were synthesized and their ability to cohere examined on non-denaturing acrylamide gels containing the stabilizing cation K+. At least 5 different mobility species were observed, in addition to that of the monomeric telomere. By cohering synthetic telomeres containing different lengths of subtelomeric DNA, we showed that each of the different mobility species was a dimer of two telomeres. Since the different mobility species did not differ in numbers or sequences of nucleotides, they must correspond to different molecular shapes probably caused by different degrees of bending of the dimer. Paradoxically, telomeres with longer subtelomeric stems cohered more efficiently. In the presence of K+, solutions had to be heated to over 90 degrees before the telomeres separated. Various synthetic constructs, restriction endonuclease and dimethyl sulfate protection experiments showed that the only nucleotides involved in the cohered structures were the 16 base 'tails' of sequence 3'G4T4G4T4. Extension of this motif was actually inimical to coherence. Oligomers containing 2 G4T4 motifs protected their GN7 positions by forming dimers, those with 5 G4T4 could do so by internal folding, but the 3' terminal group of G4 was left unprotected. This suggests that only four groups of G4 are necessary for the cohered structure. Single-chain specific nuclease, S1, as well as osmium tetroxide, which oxidizes the thymine residues of single chains, reacted less efficiently with the cohered structures. Synthetic telomeres containing inosine replacing guanosine were not observed to cohere, indicating that the C2-NH2 is strongly stabilizing. The cohered structures appear to be unusually compact and sturdy units in which four G4 blocks form quadruplexes stabilized by K+. A new model for the cohered structure is presented. Images PMID:1648206

Detecting the transport barriers in the Pearl River estuary, Southern China with the aid of Lagrangian coherent structures

NASA Astrophysics Data System (ADS)

Wei, Xing; Zhan, Haigang; Cai, Shuqun; Zhan, Weikang; Ni, Peitong

2018-05-01

Knowledge of horizontal transport pathways is important for the protection of the marine ecosystem in coastal areas. In this paper, we develop a 3D model to simulate hydrodynamics and particle transport in the Pearl River Estuary (PRE), Southern China, to study the barriers to transport in the PRE. Specifically, we use the flow velocity produced by the model to locate Lagrangian coherent structures (LCSs) hidden in ocean surface currents. Our findings show that a remarkable LCS begins upstream near the Humen inlet, extends to the Wanshan Islands via Neilingding Island, and can act as a transport barrier in the estuary. This LCS appeared 1-2 h after high tide and was persistent for 6-7 h during every ebb tide. Particles released on the west side of the LCS moved downstream, exited the estuary by Daxi Channel, and seldom spread to the east side, especially the Hong Kong Sea area. An analysis of several scenarios suggested that the formation of this LCS was due to topography restrictions and tidal forces.

Two-Dimensional Resonance Raman Signatures of Vibronic Coherence Transfer in Chemical Reactions.

PubMed

Guo, Zhenkun; Molesky, Brian P; Cheshire, Thomas P; Moran, Andrew M

2017-11-02

Two-dimensional resonance Raman (2DRR) spectroscopy has been developed for studies of photochemical reaction mechanisms and structural heterogeneity in condensed phase systems. 2DRR spectroscopy is motivated by knowledge of non-equilibrium effects that cannot be detected with traditional resonance Raman spectroscopy. For example, 2DRR spectra may reveal correlated distributions of reactant and product geometries in systems that undergo chemical reactions on the femtosecond time scale. Structural heterogeneity in an ensemble may also be reflected in the 2D spectroscopic line shapes of both reactive and non-reactive systems. In this chapter, these capabilities of 2DRR spectroscopy are discussed in the context of recent applications to the photodissociation reactions of triiodide. We show that signatures of "vibronic coherence transfer" in the photodissociation process can be targeted with particular 2DRR pulse sequences. Key differences between the signal generation mechanisms for 2DRR and off-resonant 2D Raman spectroscopy techniques are also addressed. Overall, recent experimental developments and applications of the 2DRR method suggest that it will be a valuable tool for elucidating ultrafast chemical reaction mechanisms.

Coherent structure coloring: identification of coherent structures from sparse flow trajectories using graph theory

NASA Astrophysics Data System (ADS)

Schlueter, Kristy; Dabiri, John

2016-11-01

Coherent structure identification is important in many fluid dynamics applications, including transport phenomena in ocean flows and mixing and diffusion in turbulence. However, many of the techniques currently available for measuring such flows, including ocean drifter datasets and particle tracking velocimetry, only result in sparse velocity data. This is often insufficient for the use of current coherent structure detection algorithms based on analysis of the deformation gradient. Here, we present a frame-invariant method for detecting coherent structures from Lagrangian flow trajectories that can be sparse in number. The method, based on principles used in graph coloring algorithms, examines a measure of the kinematic dissimilarity of all pairs of flow trajectories, either measured experimentally, e.g. using particle tracking velocimetry; or numerically, by advecting fluid particles in the Eulerian velocity field. Coherence is assigned to groups of particles whose kinematics remain similar throughout the time interval for which trajectory data is available, regardless of their physical proximity to one another. Through the use of several analytical and experimental validation cases, this algorithm is shown to robustly detect coherent structures using significantly less flow data than is required by existing methods. This research was supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

The Interplay of Reader Goals, Working Memory, and Text Structure During Reading

PubMed Central

Bohn-Gettler, Catherine M.; Kendeou, Panayiota

2014-01-01

In the current study we examined the complex interactions of instructional context, text properties, and reader characteristics during comprehension. College students were tasked with the goal of reading for study versus entertainment (instructional context) while thinking-aloud about four different expository text structures (text properties). Working memory also was assessed (reader characteristics). Reading goals and working memory interacted to influence paraphrasing and non-coherence processes when thinking aloud. Reading goals, working memory, and text structure all interacted to influence text-based inferences. Text structure also influenced knowledge-based inferences. Post-reading recall was highest for those with the instructional goal of reading for study (compared to entertainment), as well as for problem-response and compare-contrast texts (compared to descriptive and chronological texts). Implications of the findings are discussed. PMID:25018581

Three-dimensional structure of dominant instabilities in turbulent flow over smooth and rough boundaries

NASA Astrophysics Data System (ADS)

Grass, A. J.; Stuart, R. J.; Mansour-Tehrani, M.

1991-01-01

The current status of knowledge regarding coherent vortical structures in turbulent boundary layers and their role in turbulence generation are reviewed. The investigations reported in the study concentrate attention on rough-wall flows prevailing in the geophysical environment and include an experiment determining the three-dimensional form of the turbulence structures linked to the ejection and inrush events observed over rough walls and an experiment concerned with measuring the actual spanwise scale of the near-wall structures for boundary conditions ranging from hydrodynamically smooth to fully rough. It is demonstrated that horseshoe vortical structures are present and play an important role in rough-wall flows and they increase in scale with increasing wall distance, while a dominant spanwise wavelength occurs in the instantaneous cross-flow distribution of streamwise velocity close to the rough wall.

Exploring the attributes of critical thinking: a conceptual basis.

PubMed

Forneris, Susan G

2004-01-01

Many teaching methods used in nursing education to enhance critical thinking focus on teaching students how to directly apply knowledge; a technically rational approach. While seemingly effective at enhancing students' critical thinking abilities in structured learning situations, these methods don't prepare students to operationalize critical thinking to manage the complexities that actually exist in practice. The work of contemporary educational theorists Paulo Freire, Donald Schon, Chris Argyris, Jack Mezirow, Stephen Brookfield, and Robert Tennyson all share similar perspectives on thinking in practice and the use of reflection to achieve a coherence of understanding. Their perspectives provide insight on how educators can shift from a means-end approach to operationalizing thinking in practice. The author identifies four attributes of critical thinking in practice evidenced in these views, followed by a discussion of specific educational strategies that reflect these attributes, and operationalize a critical thinking process in nursing practice to achieve a coherence of understanding.

The phonological-distributional coherence hypothesis: cross-linguistic evidence in language acquisition.

PubMed

Monaghan, Padraic; Christiansen, Morten H; Chater, Nick

2007-12-01

Several phonological and prosodic properties of words have been shown to relate to differences between grammatical categories. Distributional information about grammatical categories is also a rich source in the child's language environment. In this paper we hypothesise that such cues operate in tandem for developing the child's knowledge about grammatical categories. We term this the Phonological-Distributional Coherence Hypothesis (PDCH). We tested the PDCH by analysing phonological and distributional information in distinguishing open from closed class words and nouns from verbs in four languages: English, Dutch, French, and Japanese. We found an interaction between phonological and distributional cues for all four languages indicating that when distributional cues were less reliable, phonological cues were stronger. This provides converging evidence that language is structured such that language learning benefits from the integration of information about category from contextual and sound-based sources, and that the child's language environment is less impoverished than we might suspect.

Lagrangian motion, coherent structures, and lines of persistent material strain.

PubMed

Samelson, R M

2013-01-01

Lagrangian motion in geophysical fluids may be strongly influenced by coherent structures that support distinct regimes in a given flow. The problems of identifying and demarcating Lagrangian regime boundaries associated with dynamical coherent structures in a given velocity field can be studied using approaches originally developed in the context of the abstract geometric theory of ordinary differential equations. An essential insight is that when coherent structures exist in a flow, Lagrangian regime boundaries may often be indicated as material curves on which the Lagrangian-mean principal-axis strain is large. This insight is the foundation of many numerical techniques for identifying such features in complex observed or numerically simulated ocean flows. The basic theoretical ideas are illustrated with a simple, kinematic traveling-wave model. The corresponding numerical algorithms for identifying candidate Lagrangian regime boundaries and lines of principal Lagrangian strain (also called Lagrangian coherent structures) are divided into parcel and bundle schemes; the latter include the finite-time and finite-size Lyapunov exponent/Lagrangian strain (FTLE/FTLS and FSLE/FSLS) metrics. Some aspects and results of oceanographic studies based on these approaches are reviewed, and the results are discussed in the context of oceanographic observations of dynamical coherent structures.

Interactions among Elaborative Interrogation, Knowledge, and Interest in the Process of Constructing Knowledge from Text

ERIC Educational Resources Information Center

Ozgungor, Sevgi; Guthrie, John T.

2004-01-01

The authors examined the impact of elaborative interrogation on knowledge construction during expository text reading, specifically, the interactions among elaborative interrogation, knowledge, and interest. Three measures of learning were taken: recall, inference, and coherence. Elaborative interrogation affected all aspects of learning measured,…

Conceptual Structure within and between Modalities

PubMed Central

Dilkina, Katia; Lambon Ralph, Matthew A.

2012-01-01

Current views of semantic memory share the assumption that conceptual representations are based on multimodal experience, which activates distinct modality-specific brain regions. This proposition is widely accepted, yet little is known about how each modality contributes to conceptual knowledge and how the structure of this contribution varies across these multiple information sources. We used verbal feature lists, features from drawings, and verbal co-occurrence statistics from latent semantic analysis to examine the informational structure in four domains of knowledge: perceptual, functional, encyclopedic, and verbal. The goals of the analysis were three-fold: (1) to assess the structure within individual modalities; (2) to compare structures between modalities; and (3) to assess the degree to which concepts organize categorically or randomly. Our results indicated significant and unique structure in all four modalities: perceptually, concepts organize based on prominent features such as shape, size, color, and parts; functionally, they group based on use and interaction; encyclopedically, they arrange based on commonality in location or behavior; and verbally, they group associatively or relationally. Visual/perceptual knowledge gives rise to the strongest hierarchical organization and is closest to classic taxonomic structure. Information is organized somewhat similarly in the perceptual and encyclopedic domains, which differs significantly from the structure in the functional and verbal domains. Notably, the verbal modality has the most unique organization, which is not at all categorical but also not random. The idiosyncrasy and complexity of conceptual structure across modalities raise the question of how all of these modality-specific experiences are fused together into coherent, multifaceted yet unified concepts. Accordingly, both methodological and theoretical implications of the present findings are discussed. PMID:23293593

Curriculum coherence: A comparative analysis of elementary science content standards in People's Republic of China and the USA

NASA Astrophysics Data System (ADS)

Huang, Fang

This study examines elementary science content standards curriculum coherence between the People's Republic of China and the United States of America. Three aspects of curriculum coherence are examined in this study: topic inclusion, topic duration, and curriculum structure. Specifically this study centers on the following research questions: (1) What science knowledge is intended for elementary students in each country? (2) How long each topic stays in the curriculum? (3) How these topics sequence and connect with each other? (4) And finally, what is the implication for elementary science curriculum development? Four intended science curriculum frameworks were selected respectively for each country. A technique of General Topic Trace Mapping (GTTM) was applied to generate the composite science content standards out of the selected curriculum for each country. In comparison, the composite USA and Chinese elementary science content standards form a stark contrast: a bunch of broad topics vs. a focus on a set of key topics at each grade; an average of 3.4 year topic duration vs. an average of 1.68 year topic duration; a stress on connections among related ideas vs. a discrete disposition of related ideas; laundry list topic organization vs. hierarchical organization of science topics. In analyzing the interrelationships among these characteristics, this study reached implications for developing coherent science content standards: First, for the overall curriculum, the topic inclusion should reflect the logical and sequential nature of knowledge in science. Second, for each grade level, less, rather than more science topics should be focused. Third, however, it should be clarified that a balance should be made between curriculum breadth and depth by considering student needs, subject matter, and child development. Fourth, the topic duration should not be too long. The lengthy topic duration tends to undermine links among ideas as well as lead to superficial treatment of topics.

Associations between knowledge of disease, depression and anxiety, social support, sense of coherence and optimism with health-related quality of life in an ambulatory sample of adolescents with heart disease.

PubMed

Wang, Qifeng; Hay, Margaret; Clarke, David; Menahem, Samuel

2014-02-01

Advances in overall management have led to an increasing number of adolescents with congenital heart disease reaching adulthood. This study aimed to evaluate the health-related quality of life in adolescents with heart disease, and examine its relationship with the adolescents' knowledge and understanding of their congenital heart disease, its severity, and its relationship to the degree of anxiety and depression, feeling of optimism and sense of coherence experienced by the adolescents together with their social support. Adolescents with heart disease were recruited from an ambulatory setting at a tertiary centre. Patients completed self-report questionnaires including the Paediatric Quality of Life Inventory 3.0-Cardiac Module, a questionnaire assessing the adolescents' knowledge of their cardiac condition, the Hospital Anxiety and Depression Scale, Multidimensional Scale of Perceived Social Support, Life Orientation Test-Revised, and Sense of Coherence-13, supplemented by clinical information provided by the attending cardiologists. A total of 114 patients aged 12-20 years were recruited over 15 months. In all, 98% of patients were in New York Heart Association class I. Their health-related quality of life was found to positively correlate with a low level of anxiety and depression (Pearson correlation, r = -0.57, p < 0.001), a good knowledge of their cardiac condition (r = 0.31, p < 0.01), feelings of optimism (r = 0.39, p < 0.001), adequate social support (r = 0.27, p < 0.01), and a strong sense of coherence (r = 0.24, p < 0.01). Adolescents' knowledge and understanding of their cardiac abnormality together with an improved sense of well-being had a positive influence on their health-related quality of life.

Remote wind sensing with a CW diode laser lidar beyond the coherence regime.

PubMed

Hu, Qi; Rodrigo, Peter John; Pedersen, Christian

2014-08-15

We experimentally demonstrate for the first time (to our knowledge) a coherent CW lidar system capable of wind speed measurement at a probing distance beyond the coherence regime of the light source. A side-by-side wind measurement was conducted on the field using two lidar systems with identical optical designs but different laser linewidths. While one system was operating within the coherence regime, the other was measuring at least 2.4 times the coherence range. The probing distance of both lidars is 85 m and the radial wind speed correlation was measured to be r2=0.965 between the two lidars at a sampling rate of 2 Hz. Based on our experimental results, we describe a practical guideline for designing a wind lidar operating beyond the coherence regime.

Three-dimensional optical coherence tomography of the embryonic murine cardiovascular system

NASA Astrophysics Data System (ADS)

Luo, Wei; Marks, Daniel L.; Ralston, Tyler S.; Boppart, Stephen A.

2006-03-01

Optical coherence tomography (OCT) is an emerging high-resolution real-time biomedical imaging technology that has potential as a novel investigational tool in developmental biology and functional genomics. In this study, murine embryos and embryonic hearts are visualized with an OCT system capable of 2-µm axial and 15-µm lateral resolution and with real-time acquisition rates. We present, to our knowledge, the first sets of high-resolution 2- and 3-D OCT images that reveal the internal structures of the mammalian (murine) embryo (E10.5) and embryonic (E14.5 and E17.5) cardiovascular system. Strong correlations are observed between OCT images and corresponding hematoxylin- and eosin-stained histological sections. Real-time in vivo embryonic (E10.5) heart activity is captured by spectral-domain optical coherence tomography, processed, and displayed at a continuous rate of five frames per second. With the ability to obtain not only high-resolution anatomical data but also functional information during cardiovascular development, the OCT technology has the potential to visualize and quantify changes in murine development and in congenital and induced heart disease, as well as enable a wide range of basic in vitro and in vivo research studies in functional genomics.

Effect of local minima on adiabatic quantum optimization.

PubMed

Amin, M H S

2008-04-04

We present a perturbative method to estimate the spectral gap for adiabatic quantum optimization, based on the structure of the energy levels in the problem Hamiltonian. We show that, for problems that have an exponentially large number of local minima close to the global minimum, the gap becomes exponentially small making the computation time exponentially long. The quantum advantage of adiabatic quantum computation may then be accessed only via the local adiabatic evolution, which requires phase coherence throughout the evolution and knowledge of the spectrum. Such problems, therefore, are not suitable for adiabatic quantum computation.

Complex Networks - A Key to Understanding Brain Function

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sporns, Olaf

2008-01-23

The brain is a complex network of neurons, engaging in spontaneous and evoked activity that is thought to be the main substrate of mental life.  How this complex system works together to process information and generate coherent cognitive states, even consciousness, is not yet well understood.  In my talk I will review recent studies that have revealed characteristic structural and functional attributes of brain networks, and discuss efforts to build computational models of the brain that are informed by our growing knowledge of brain anatomy and physiology.

Complex Networks - A Key to Understanding Brain Function

ScienceCinema

Sporns, Olaf

2017-12-22

The brain is a complex network of neurons, engaging in spontaneous and evoked activity that is thought to be the main substrate of mental life.  How this complex system works together to process information and generate coherent cognitive states, even consciousness, is not yet well understood.  In my talk I will review recent studies that have revealed characteristic structural and functional attributes of brain networks, and discuss efforts to build computational models of the brain that are informed by our growing knowledge of brain anatomy and physiology.

In vivo layer visualization of rat olfactory bulb by a swept source optical coherence tomography and its confirmation through electrocoagulation and anatomy

PubMed Central

Watanabe, Hideyuki; Rajagopalan, Uma Maheswari; Nakamichi, Yu; Igarashi, Kei M.; Madjarova, Violeta Dimitrova; Kadono, Hirofumi; Tanifuji, Manabu

2011-01-01

Here, we report in vivo 3-D visualization of the layered organization of a rat olfactory bulb (OB) by a swept source optical coherence tomography (SS-OCT). The SS-OCT operates at a wavelength of 1334 nm with respective theoretical depth and lateral resolutions of 6.7 μm and 15.4 μm in air and hence it is possible to get a 3D structural map of OB in vivo at the micron level resolution with millimeter-scale imaging depth. Up until now, with methods such as MRI, confocal microscopy, OB depth structure in vivo had not been clearly visualized as these do not satisfy the criterion of simultaneously providing micron-scale spatial resolution and imaging up to a few millimeter in depth. In order to confirm the OB’s layered organization revealed by SS-OCT, we introduced the technique of electrocoagulation to make landmarks across the layered structure. To our knowledge this is such a first study that combines electrocoagulation and OCT in vivo of rat OB. Our results confirmed the layered organization of OB, and moreover the layers were clearly identified by electrocoagulation landmarks both in the OCT structural and anatomical slice images. We expect such a combined study is beneficial for both OCT and neuroscience fields. PMID:21833364

Conceptual Coherence, Comprehension, and Vocabulary Acquisition: A Knowledge Effect?

ERIC Educational Resources Information Center

Cervetti, Gina N.; Wright, Tanya S.; Hwang, HyeJin

2016-01-01

Previous research has documented the role of readers' existing topic knowledge in supporting students' comprehension of text; yet, we know less about how to build students' knowledge in order to support comprehension and vocabulary learning. In the current study, we test the hypothesis that knowledge can be built and leveraged simultaneously in…

Use of passive scalar tagging for the study of coherent structures in the plane mixing layer

NASA Technical Reports Server (NTRS)

Ramaprian, B. R.; Sandham, N. D.; Mungal, M. G.; Reynolds, W. C.

1988-01-01

Data obtained from the numerical simulation of a 2-D mixing layer were used to study the feasibility of using the instantaneous concentration of a passive scalar for detecting the typical coherent structures in the flow. The study showed that this technique works quite satisfactorily and yields results similar to those that can be obtained by using the instantaneous vorticity for structure detection. Using the coherent events educed by the scalar conditioning technique, the contribution of the coherent events to the total turbulent momentum and scalar transport was estimated. It is found that the contribution from the typical coherent events is of the same order as that of the time-mean value. However, the individual contributions become very large during the pairing of these structures. The increase is particularly spectacular in the case of the Reynolds shear stress.

Category Coherence and Category-Based Property Induction

ERIC Educational Resources Information Center

Rehder, Bob; Hastie, Reid

2004-01-01

One important property of human object categories is that they define the sets of exemplars to which newly observed properties are generalized. We manipulated the causal knowledge associated with novel categories and assessed the resulting strength of property inductions. We found that the theoretical coherence afforded to a category by…

Coherent Structures in Plasmas Relevant to Electric Propulsion

DTIC Science & Technology

2016-06-24

AFRL-AFOSR-VA-TR-2016-0229 Coherent Structures in Plasmas Relevant to Electric Propulsion Mark Cappelli LELAND STANFORD JUNIOR UNIV CA Final Report...TITLE AND SUBTITLE Coherent Structures in Plasmas Relevant to Electric Propulsion 5a. CONTRACT NUMBER N/A 5b. GRANT NUMBER FA9550-14-1-0017 5c...to propulsion devices through experimental, theoretical, and numerical studies. 15. SUBJECT TERMS Plasma instabilities in magnetized discharges

COHERENT EVENTS AND SPECTRAL SHAPE AT ION KINETIC SCALES IN THE FAST SOLAR WIND TURBULENCE

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lion, Sonny; Alexandrova, Olga; Zaslavsky, Arnaud, E-mail: sonny.lion@obspm.fr

2016-06-10

In this paper we investigate spectral and phase coherence properties of magnetic fluctuations in the vicinity of the spectral transition from large, magnetohydrodynamic to sub-ion scales using in situ measurements of the Wind spacecraft in a fast stream. For the time interval investigated by Leamon et al. (1998) the phase coherence analysis shows the presence of sporadic quasi-parallel Alfvén ion cyclotron (AIC) waves as well as coherent structures in the form of large-amplitude, quasi-perpendicular Alfvén vortex-like structures and current sheets. These waves and structures importantly contribute to the observed power spectrum of magnetic fluctuations around ion scales; AIC waves contributemore » to the spectrum in a narrow frequency range whereas the coherent structures contribute to the spectrum over a wide frequency band from the inertial range to the sub-ion frequency range. We conclude that a particular combination of waves and coherent structures determines the spectral shape of the magnetic field spectrum around ion scales. This phenomenon provides a possible explanation for a high variability of the magnetic power spectra around ion scales observed in the solar wind.« less

Knowledge representation of rock plastic deformation

NASA Astrophysics Data System (ADS)

Davarpanah, Armita; Babaie, Hassan

2017-04-01

The first iteration of the Rock Plastic Deformation (RPD) ontology models the semantics of the dynamic physical and chemical processes and mechanisms that occur during the deformation of the generally inhomogeneous polycrystalline rocks. The ontology represents the knowledge about the production, reconfiguration, displacement, and consumption of the structural components that participate in these processes. It also formalizes the properties that are known by the structural geology and metamorphic petrology communities to hold between the instances of the spatial components and the dynamic processes, the state and system variables, the empirical flow laws that relate the variables, and the laboratory testing conditions and procedures. The modeling of some of the complex physio-chemical, mathematical, and informational concepts and relations of the RPD ontology is based on the class and property structure of some well-established top-level ontologies. The flexible and extensible design of the initial version of the RPD ontology allows it to develop into a model that more fully represents the knowledge of plastic deformation of rocks under different spatial and temporal scales in the laboratory and in solid Earth. The ontology will be used to annotate the datasets related to the microstructures and physical-chemical processes that involve them. This will help the autonomous and globally distributed communities of experimental structural geologists and metamorphic petrologists to coherently and uniformly distribute, discover, access, share, and use their data through automated reasoning and enhanced data integration and software interoperability.

Determining Correlation and Coherence Lengths in Turbulent Boundary Layer Flight Data

NASA Technical Reports Server (NTRS)

Palumbo, Dan

2012-01-01

Wall pressure data acquired during flight tests at several flight conditions are analysed and the correlation and coherence lengths of the data reported. It is found that the correlation and coherence lengths are influenced by the origin of the structure producing the pressure and the frequency bandwidth over which the analyses are performed. It is shown how the frequency bandwidth biases the correlation length and how the convection of the pressure field might reduce the coherence measured between sensors. A convected form of the cross correlation and cross spectrum is introduced to compensate for the effects of convection. Coherence lengths measured in the streamwise direction appear much longer than expected. Coherent structures detected using the convected cross correlation do not exhibit an exponential coherent power decay.

Limited role of spectra in dynamo theory: coherent versus random dynamos.

PubMed

Tobias, Steven M; Cattaneo, Fausto

2008-09-19

We discuss the importance of phase information and coherence times in determining the dynamo properties of turbulent flows. We compare the kinematic dynamo properties of three flows with the same energy spectrum. The first flow is dominated by coherent structures with nontrivial phase information and long eddy coherence times, the second has random phases and long-coherence time, the third has nontrivial phase information, but short coherence time. We demonstrate that the first flow is the most efficient kinematic dynamo, owing to the presence of sustained stretching and constructive folding. We argue that these results place limitations on the possible inferences of the dynamo properties of flows from the use of spectra alone, and that the role of coherent structures must always be accounted for.

Partially coherent axiconic surface plasmon polariton fields

NASA Astrophysics Data System (ADS)

Chen, Yahong; Norrman, Andreas; Ponomarenko, Sergey A.; Friberg, Ari T.

2018-04-01

We introduce a class of structured polychromatic surface electromagnetic fields, reminiscent of conventional optical axicon fields, through a judicious superposition of partially correlated surface plasmon polaritons. We show that such partially coherent axiconic surface plasmon polariton fields are structurally stable and statistically highly versatile with regard to spectral density, polarization state, energy flow, and degree of coherence. These fields can be created by plasmon coherence engineering and may prove instrumental broadly in surface physics and in various nanophotonics applications.

Cortical thickness as a contributor to abnormal oscillations in schizophrenia?☆

PubMed Central

Edgar, J. Christopher; Chen, Yu-Han; Lanza, Matthew; Howell, Breannan; Chow, Vivian Y.; Heiken, Kory; Liu, Song; Wootton, Cassandra; Hunter, Michael A.; Huang, Mingxiong; Miller, Gregory A.; Cañive, José M.

2013-01-01

Introduction Although brain rhythms depend on brain structure (e.g., gray and white matter), to our knowledge associations between brain oscillations and structure have not been investigated in healthy controls (HC) or in individuals with schizophrenia (SZ). Observing function–structure relationships, for example establishing an association between brain oscillations (defined in terms of amplitude or phase) and cortical gray matter, might inform models on the origins of psychosis. Given evidence of functional and structural abnormalities in primary/secondary auditory regions in SZ, the present study examined how superior temporal gyrus (STG) structure relates to auditory STG low-frequency and 40 Hz steady-state activity. Given changes in brain activity as a function of age, age-related associations in STG oscillatory activity were also examined. Methods Thirty-nine individuals with SZ and 29 HC were recruited. 40 Hz amplitude-modulated tones of 1 s duration were presented. MEG and T1-weighted sMRI data were obtained. Using the sources localizing 40 Hz evoked steady-state activity (300 to 950 ms), left and right STG total power and inter-trial coherence were computed. Time–frequency group differences and associations with STG structure and age were also examined. Results Decreased total power and inter-trial coherence in SZ were observed in the left STG for initial post-stimulus low-frequency activity (~ 50 to 200 ms, ~ 4 to 16 Hz) as well as 40 Hz steady-state activity (~ 400 to 1000 ms). Left STG 40 Hz total power and inter-trial coherence were positively associated with left STG cortical thickness in HC, not in SZ. Left STG post-stimulus low-frequency and 40 Hz total power were positively associated with age, again only in controls. Discussion Left STG low-frequency and steady-state gamma abnormalities distinguish SZ and HC. Disease-associated damage to STG gray matter in schizophrenia may disrupt the age-related left STG gamma-band function–structure relationships observed in controls. PMID:24371794

Coherent exchange of healthcare knowledge in open systems.

PubMed

Buchan, I; Hanka, R

1997-01-01

This paper outlines design philosophies and methods for healthcare knowledge systems. Clinical priorities for knowledge are discussed in terms of temporal and individual needs. Book centred organisation of healthcare knowledge, which has proven effective in clinical practice, is proposed as the basis of virtual libraries available at the point of care for target groups of healthcare professionals.

Propagation and scattering of optical light beams in free space, in atmosphere and in biological media

NASA Astrophysics Data System (ADS)

Sahin, Serkan

With their first production implemented around 1960's, lasers have afterwards proven to be excellent light sources in building the technology. Subsequently, it has been shown that the extraordinary properties of lasers are related to their coherence properties. Recent developments in optics make it possible to synthesize partially coherent light beams from fully coherent ones. In the last several decades it was seen that using partially coherent light sources may be advantageous, in the areas such as laser surface processing, fiber and free-space optical communications, and medical diagnostics. In this thesis, I study extensively the generation, the propagation in different media, and the scattering of partially coherent light beams with respect to their spectral polarization and coherence states. For instance, I analyze the evolution of recently introduced degree of cross-polarization of light fields in free space; then develop a novel partially coherent light source which acquires and keeps a flat intensity profile around the axis at any distance in the far field; and investigate the interaction of electromagnetic random light with the human eye lens. A part of the thesis treats the effect of atmospheric turbulence on random light beams. Due to random variations in the refractive index, atmospheric turbulence modulates all physical and statistical properties of propagating beams. I have explored the possibility of employing the polarimetric domain of the beam for scintillation reduction, which positively affects the performance of free-space communication systems. I also discuss novel techniques for the sensing of rough targets in the turbulent atmosphere by polarization and coherence properties of light. The other contribution to the thesis is the investigation of light scattering from deterministic or random collections of particles, within the validity of first Born approximation. In the case of a random collection, I introduce and model the new quantity (named pair-structure function) describing correlations among particles, the knowledge of which is necessary for the rigorous predictions of scattered radiation's statistics. Also, by introducing the multi-Gaussian family of functions for scattering potentials, we demonstrate a realistic model for semi-hard edges of particles and bubblelike particles.

City of Physics--Analogies to Increase Cognitive Coherence in Physics Learning

ERIC Educational Resources Information Center

Tabor-Morris, A. E.; Froriep, K. A.; Briles, T. M.; McGuire, C. M.

2009-01-01

Physics educators and researchers can be concerned with how students attain cognitive coherence: specifically, how students understand and intra-connect the whole of their knowledge of the "field of physics". Starting instead with the metaphor "city of physics", the implication of applying architectural concepts for the human acquisition of mental…

Sleep Increases Explicit Solutions and Reduces Intuitive Judgments of Semantic Coherence

ERIC Educational Resources Information Center

Zander, Thea; Volz, Kirsten G.; Born, Jan; Diekelmann, Susanne

2017-01-01

Sleep fosters the generation of explicit knowledge. Whether sleep also benefits implicit intuitive decisions about underlying patterns is unclear. We examined sleep's role in explicit and intuitive semantic coherence judgments. Participants encoded sets of three words and after a sleep or wake period were required to judge the potential…

Coherence or Interest: Which Is Most Important in Online Multimedia Learning?

ERIC Educational Resources Information Center

Muller, Derek A.; Lee, Kester J.; Sharma, Manjula D.

2008-01-01

The coherence principle states that all non-essential information in multimedia messages should be eliminated to minimise demands on cognitive resources. This assertion has been empirically verified in controlled laboratory studies with learners who have little prior knowledge and limited interest in the domain of instruction. It has not been…

A Modeling Approach to the Development of Students' Informal Inferential Reasoning

ERIC Educational Resources Information Center

Doerr, Helen M.; Delmas, Robert; Makar, Katie

2017-01-01

Teaching from an informal statistical inference perspective can address the challenge of teaching statistics in a coherent way. We argue that activities that promote model-based reasoning address two additional challenges: providing a coherent sequence of topics and promoting the application of knowledge to novel situations. We take a models and…

Connecting coherent structures and strange attractors

NASA Technical Reports Server (NTRS)

Keefe, Laurence R.

1990-01-01

A concept of turbulence derived from nonlinear dynamical systems theory suggests that turbulent solutions to the Navier-Stokes equations are restricted to strange attractors, and, by implication, that turbulent phenomenology must find some expression or source in the structure of these mathematical objects. Examples and discussions are presented to link coherent structures to some of the commonly known characteristics of strange attractors. Basic to this link is a geometric interpretation of conditional sampling techniques employed to educe coherent structures that offers an explanation for their appearance in measurements as well as their size.

Drawing the line between constituent structure and coherence relations in visual narratives

PubMed Central

Cohn, Neil; Bender, Patrick

2016-01-01

Theories of visual narrative understanding have often focused on the changes in meaning across a sequence, like shifts in characters, spatial location, and causation, as cues for breaks in the structure of a discourse. In contrast, the theory of Visual Narrative Grammar posits that hierarchic “grammatical” structures operate at the discourse level using categorical roles for images, which may or may not co-occur with shifts in coherence. We therefore examined the relationship between narrative structure and coherence shifts in the segmentation of visual narrative sequences using a “segmentation task” where participants drew lines between images in order to divide them into sub-episodes. We used regressions to analyze the influence of the expected constituent structure boundary, narrative categories, and semantic coherence relationships on the segmentation of visual narrative sequences. Narrative categories were a stronger predictor of segmentation than linear coherence relationships between panels, though both influenced participants’ divisions. Altogether, these results support the theory that meaningful sequential images use a narrative grammar that extends above and beyond linear semantic shifts between discourse units. PMID:27709982

Drawing the line between constituent structure and coherence relations in visual narratives.

PubMed

Cohn, Neil; Bender, Patrick

2017-02-01

Theories of visual narrative understanding have often focused on the changes in meaning across a sequence, like shifts in characters, spatial location, and causation, as cues for breaks in the structure of a discourse. In contrast, the theory of visual narrative grammar posits that hierarchic "grammatical" structures operate at the discourse level using categorical roles for images, which may or may not co-occur with shifts in coherence. We therefore examined the relationship between narrative structure and coherence shifts in the segmentation of visual narrative sequences using a "segmentation task" where participants drew lines between images in order to divide them into subepisodes. We used regressions to analyze the influence of the expected constituent structure boundary, narrative categories, and semantic coherence relationships on the segmentation of visual narrative sequences. Narrative categories were a stronger predictor of segmentation than linear coherence relationships between panels, though both influenced participants' divisions. Altogether, these results support the theory that meaningful sequential images use a narrative grammar that extends above and beyond linear semantic shifts between discourse units. (PsycINFO Database Record (c) 2017 APA, all rights reserved).

Structure function analysis of two-scale Scalar Ramps. Part II: Coherent structure scaling and surface renewal applications

USDA-ARS?s Scientific Manuscript database

Structure functions are used to study the dissipation and inertial range scales of turbulent energy, to parameterize remote turbulence measurements, and to characterize ramp features in the turbulent field. The ramp features are associated with turbulent coherent structures, which dominate energy a...

Network-based study of Lagrangian transport and mixing

NASA Astrophysics Data System (ADS)

Padberg-Gehle, Kathrin; Schneide, Christiane

2017-10-01

Transport and mixing processes in fluid flows are crucially influenced by coherent structures and the characterization of these Lagrangian objects is a topic of intense current research. While established mathematical approaches such as variational methods or transfer-operator-based schemes require full knowledge of the flow field or at least high-resolution trajectory data, this information may not be available in applications. Recently, different computational methods have been proposed to identify coherent behavior in flows directly from Lagrangian trajectory data, that is, numerical or measured time series of particle positions in a fluid flow. In this context, spatio-temporal clustering algorithms have been proven to be very effective for the extraction of coherent sets from sparse and possibly incomplete trajectory data. Inspired by these recent approaches, we consider an unweighted, undirected network, where Lagrangian particle trajectories serve as network nodes. A link is established between two nodes if the respective trajectories come close to each other at least once in the course of time. Classical graph concepts are then employed to analyze the resulting network. In particular, local network measures such as the node degree, the average degree of neighboring nodes, and the clustering coefficient serve as indicators of highly mixing regions, whereas spectral graph partitioning schemes allow us to extract coherent sets. The proposed methodology is very fast to run and we demonstrate its applicability in two geophysical flows - the Bickley jet as well as the Antarctic stratospheric polar vortex.

Coherence properties of the radiation from FLASH

NASA Astrophysics Data System (ADS)

Schneidmiller, E. A.; Yurkov, M. V.

2016-02-01

Free electron LASer in Hamburg is the first free electron laser user facility operating in the vacuum ultraviolet and soft X-ray wavelength range. Many user experiments require knowledge of the spatial and temporal coherence properties of the radiation. In this paper, we present a theoretical analysis of the coherence properties of the radiation for the fundamental and for the higher odd frequency harmonics. We show that temporal and spatial coherence reach their maxima close to the free electron laser (FEL) saturation but may degrade significantly in the post-saturation regime. We also find that the pointing stability of short FEL pulses is limited due to the fact that nonazimuthal FEL eigenmodes are not sufficiently suppressed. We discuss possible ways for improving the degree of transverse coherence and the pointing stability.

Propagation of partially coherent Lorentz and Lorentz-Gauss beams through a paraxial ABCD optical system in a turbulent atmosphere

NASA Astrophysics Data System (ADS)

Zhao, Chengliang; Cai, Yangjian

2011-05-01

Based on the generalized Huygens-Fresnel integral, propagation of partially coherent Lorentz and Lorentz-Gauss beams through a paraxial ABCD optical system in a turbulent atmosphere was investigated. Analytical propagation formulae were derived for the cross-spectral densities of partially coherent Lorentz and Lorentz-Gauss beams. As an application example, the focusing properties of partially coherent Gaussian, Lorentz and Lorentz-Gauss beams in a turbulent atmosphere and in free space were studied numerically and comparatively. It is found that the focusing properties of such beams are closely related to the initial coherence length and the structure constant of turbulence. By choosing a suitable initial coherence length, a partially coherent Lorentz beam can be focused more tightly than a Gaussian or Lorentz-Gauss beam in free space or in a turbulent atmosphere with small structure constant at the geometrical focal plane.

Investigating learners' epistemological framings of quantum mechanics

NASA Astrophysics Data System (ADS)

Dini, Vesal

Classical mechanics challenges students to use their intuitions and experiences as a basis for understanding, in effect to approach learning as "a refinement of everyday thinking'' (Einstein, 1936). Moving on to quantum mechanics (QM), students, like physicists, need to adjust this approach, in particular with respect to the roles that intuitive knowledge and mathematics play in the pursuit of coherent understanding (these are adjustments to aspects of their epistemologies). In this dissertation, I explore how some students manage the epistemological transition. I began this work by recruiting both graduate and undergraduate students, interviewing each subject several times as they moved through coursework in QM. The interviews featured, among other things, how students tried to fit ideas together in mutually consistent ways, including with respect to intuitive knowledge, mathematics and experiment, if at all. I modeled these dynamic cognitive processes as different epistemological framings (i.e., tacit, in-the-moment responses to the question "How should I approach knowledge?''). Through detailed qualitative analyses of students' reasoning and a systematic coding of their interviews, I explored how these coherence seeking related framings impacted their learning. The dissertation supports three main findings: (1) students' patterns of epistemological framing are mostly stable within a given course; (2) students who profess epistemologies aligned with the coordination of coherence seeking framings tend to be more stable in demonstrating them; and (3) students aware that their understanding of QM ultimately anchors in its mathematics tend to produce more coherent explanations and perform better in their courses. These findings are consistent with existing research on student epistemologies in QM and imply that epistemologies, in particular whether and how students seek coherence, require greater attention and emphasis in instruction.

Children's Knowledge of the Earth: A New Methodological and Statistical Approach

ERIC Educational Resources Information Center

Straatemeier, Marthe; van der Maas, Han L. J.; Jansen, Brenda R. J.

2008-01-01

In the field of children's knowledge of the earth, much debate has concerned the question of whether children's naive knowledge--that is, their knowledge before they acquire the standard scientific theory--is coherent (i.e., theory-like) or fragmented. We conducted two studies with large samples (N = 328 and N = 381) using a new paper-and-pencil…

Knowledge, expectations, and inductive reasoning within conceptual hierarchies.

PubMed

Coley, John D; Hayes, Brett; Lawson, Christopher; Moloney, Michelle

2004-01-01

Previous research (e.g. Cognition 64 (1997) 73) suggests that the privileged level for inductive inference in a folk biological conceptual hierarchy does not correspond to the "basic" level (i.e. the level at which concepts are both informative and distinct). To further explore inductive inference within conceptual hierarchies, we examine relations between knowledge of concepts at different hierarchical levels, expectations about conceptual coherence, and inductive inference. In Experiments 1 and 2, 5- and 8-year-olds and adults listed features of living kind (Experiments 1 and 2) and artifact (Experiment 2) concepts at different hierarchical levels (e.g. plant, tree, oak, desert oak), and also rated the strength of generalizations to the same concepts. For living kinds, the level that showed a relative advantage on these two tasks differed; the greatest increase in features listed tended to occur at the life-form level (e.g. tree), whereas the greatest increase in inductive strength tended to occur at the folk-generic level (e.g. oak). Knowledge and induction also showed different developmental trajectories. For artifact concepts, the levels at which the greatest gains in knowledge and induction occurred were more varied, and corresponded more closely across tasks. In Experiment 3, adults reported beliefs about within-category similarity for concepts at different levels of animal, plant and artifact hierarchies, and rated inductive strength as before. For living kind concepts, expectations about category coherence predicted patterns of inductions; knowledge did not. For artifact concepts, both knowledge and expectations predicted patterns of induction. Results suggest that beliefs about conceptual coherence play an important role in guiding inductive inference, that this role may be largely independent of specific knowledge of concepts, and that such beliefs are especially important in reasoning about living kinds.

MEG Insight into the Spectral Dynamics Underlying Steady Isometric Muscle Contraction

PubMed Central

Piitulainen, Harri; Zhou, Guangyu

2017-01-01

To gain fundamental knowledge on how the brain controls motor actions, we studied in detail the interplay between MEG signals from the primary sensorimotor (SM1) cortex and the contraction force of 17 healthy adult humans (7 females, 10 males). SM1 activity was coherent at ∼20 Hz with surface electromyogram (as already extensively reported) but also with contraction force. In both cases, the effective coupling was dominant in the efferent direction. Across subjects, the level of ∼20 Hz coherence between cortex and periphery positively correlated with the “burstiness” of ∼20 Hz SM1 (Pearson r ≈ 0.65) and peripheral fluctuations (r ≈ 0.9). Thus, ∼20 Hz coherence between cortex and periphery is tightly linked to the presence of ∼20 Hz bursts in SM1 and peripheral activity. However, the very high correlation with peripheral fluctuations suggests that the periphery is the limiting factor. At frequencies <3 Hz, both SM1 signals and ∼20 Hz SM1 envelope were coherent with both force and its absolute change rate. The effective coupling dominated in the efferent direction between (1) force and the ∼20 Hz SM1 envelope and (2) the absolute change rate of the force and SM1 signals. Together, our data favor the view that ∼20 Hz coherence between cortex and periphery during isometric contraction builds on the presence of ∼20 Hz SM1 oscillations and needs not rely on feedback from the periphery. They also suggest that effective cortical proprioceptive processing operates at <3 Hz frequencies, even during steady isometric contractions. SIGNIFICANCE STATEMENT Accurate motor actions are made possible by continuous communication between the cortex and spinal motoneurons, but the neurophysiological basis of this communication is poorly understood. Using MEG recordings in humans maintaining steady isometric muscle contractions, we found evidence that the cortex sends population-level motor commands that tend to structure according to the ∼20 Hz sensorimotor rhythm, and that it dynamically adapts these commands based on the <3 Hz fluctuations of proprioceptive feedback. To our knowledge, this is the first report to give a comprehensive account of how the human brain dynamically handles the flow of proprioceptive information and converts it into appropriate motor command to keep the contraction force steady. PMID:28951449

The Role of Composing Process and Coherence/Cohesion in FFL Writing

ERIC Educational Resources Information Center

Yetis, Veda Aslim

2017-01-01

The aim of this paper is to examine the role of composing process and knowledge about coherence/cohesion in French foreign language writing skill. Research sample consists of 35 Turkish students studying French language teaching at a Turkish university. The participants were first given a test containing of three parts in order to determine their…

Possible Futures: Using Frameworks of Knowledge to Help Year 9 Connect Past, Present and Future

ERIC Educational Resources Information Center

Nuttall, Dan

2013-01-01

How can we help pupils integrate history into coherent "Big Pictures" or mental frameworks? Building on traditions of classroom research and theorising reported in earlier editions of Teaching History, Dan Nuttall reports how his department set out to help Year 9 build a coherent big picture of twentieth-century history that would…

Coherent startup of an infrared free-electron laser

NASA Astrophysics Data System (ADS)

Jaroszynski, D. A.; Bakker, R. J.; van der Meer, A. F. G.; Oepts, D.; van Amersfoort, P. W.

1993-12-01

Coherent enhancement of the spontaneous undulator radiation by several orders of magnitude has been observed in a free-electron laser at wavelengths from 40 to 100 μm. The coherent emission can be explained by details of the electron-beam micropulse structure. Furthermore, it has been found that the phase of the optical micropulses is fixed by the electron pulse structure and that the coherence extends over successive optical micropulses, which gives rise to interference effects as a function of the optical cavity length in a laser oscillator.

Imaging single cells in a beam of live cyanobacteria with an X-ray laser.

PubMed

van der Schot, Gijs; Svenda, Martin; Maia, Filipe R N C; Hantke, Max; DePonte, Daniel P; Seibert, M Marvin; Aquila, Andrew; Schulz, Joachim; Kirian, Richard; Liang, Mengning; Stellato, Francesco; Iwan, Bianca; Andreasson, Jakob; Timneanu, Nicusor; Westphal, Daniel; Almeida, F Nunes; Odic, Dusko; Hasse, Dirk; Carlsson, Gunilla H; Larsson, Daniel S D; Barty, Anton; Martin, Andrew V; Schorb, Sebastian; Bostedt, Christoph; Bozek, John D; Rolles, Daniel; Rudenko, Artem; Epp, Sascha; Foucar, Lutz; Rudek, Benedikt; Hartmann, Robert; Kimmel, Nils; Holl, Peter; Englert, Lars; Duane Loh, Ne-Te; Chapman, Henry N; Andersson, Inger; Hajdu, Janos; Ekeberg, Tomas

2015-02-11

There exists a conspicuous gap of knowledge about the organization of life at mesoscopic levels. Ultra-fast coherent diffractive imaging with X-ray free-electron lasers can probe structures at the relevant length scales and may reach sub-nanometer resolution on micron-sized living cells. Here we show that we can introduce a beam of aerosolised cyanobacteria into the focus of the Linac Coherent Light Source and record diffraction patterns from individual living cells at very low noise levels and at high hit ratios. We obtain two-dimensional projection images directly from the diffraction patterns, and present the results as synthetic X-ray Nomarski images calculated from the complex-valued reconstructions. We further demonstrate that it is possible to record diffraction data to nanometer resolution on live cells with X-ray lasers. Extension to sub-nanometer resolution is within reach, although improvements in pulse parameters and X-ray area detectors will be necessary to unlock this potential.

Approaches to the construction of a medical informatics glossary and thesaurus.

PubMed

Rada, R; Ghaoui, C; Russell, J; Taylor, M

1993-01-01

In a project concerned with establishing a glossary and thesaurus for the medical informatics domain, various approaches to the task have been investigated. The developers take the view that a glossary should be a coherent system of terms, reflecting a coherent system of concepts that underlies a body of knowledge about a domain. A framework for the conceptual analysis of the concepts/terms underlying the domain has been developed. The emphasis of this framework is on how the concepts relate together. This work has given an important insight into how the practical task of establishing well-structured vocabularies for a field can be better achieved. An eclectic approach to term selection was adopted. Criteria for assessing what constitutes good definitions for concepts in a field were examined. Using all these approaches glossaries, thesauri and domain models of the medical informatics field are being developed. Another aspect of our work of particular interest is the development of attributed definitions from which inheritance patterns can be defined.

Coherent structure in solar wind C{sup 6+}/C{sup 4+} ionic composition data during the quiet-sun conditions of 2008

DOE Office of Scientific and Technical Information (OSTI.GOV)

Edmondson, J. K.; Lepri, S. T.; Zurbuchen, T. H.

2013-11-20

This analysis offers evidence of characteristic scale sizes in solar wind charge state data measured in situ for 13 quiet-Sun Carrington rotations in 2008. Using a previously established novel methodology, we analyze the wavelet power spectrum of the charge state ratio C{sup 6+}/C{sup 4+} measured in situ by ACE/SWICS for 2 hr and 12 minute cadence. We construct a statistical significance level in the wavelet power spectrum to quantify the interference effects arising from filling missing data in the time series, allowing extraction of significant power from the measured data to a resolution of 24 minutes. We analyze each waveletmore » power spectrum for transient coherency and global periodicities resulting from the superposition of repeating coherent structures. From the significant wavelet power spectra, we find evidence for a general upper limit on individual transient coherency of ∼10 days. We find evidence for a set of global periodicities between 4-5 hr and 35-45 days. We find evidence for the distribution of individual transient coherency scales consisting of two distinct populations. Below the ∼2 day timescale, the distribution is reasonably approximated by an inverse power law, whereas for scales ≳2 days, the distribution levels off, showing discrete peaks at common coherency scales. In addition, by organizing the transient coherency scale distributions by wind type, we find that these larger, common coherency scales are more prevalent and well defined in coronal hole wind. Finally, we discuss the implications of our results for current theories of solar wind generation and describe future work for determining the relationship between the coherent structures in our ionic composition data and the structure of the coronal magnetic field.« less

Knowledge-Based Topic Model for Unsupervised Object Discovery and Localization.

PubMed

Niu, Zhenxing; Hua, Gang; Wang, Le; Gao, Xinbo

Unsupervised object discovery and localization is to discover some dominant object classes and localize all of object instances from a given image collection without any supervision. Previous work has attempted to tackle this problem with vanilla topic models, such as latent Dirichlet allocation (LDA). However, in those methods no prior knowledge for the given image collection is exploited to facilitate object discovery. On the other hand, the topic models used in those methods suffer from the topic coherence issue-some inferred topics do not have clear meaning, which limits the final performance of object discovery. In this paper, prior knowledge in terms of the so-called must-links are exploited from Web images on the Internet. Furthermore, a novel knowledge-based topic model, called LDA with mixture of Dirichlet trees, is proposed to incorporate the must-links into topic modeling for object discovery. In particular, to better deal with the polysemy phenomenon of visual words, the must-link is re-defined as that one must-link only constrains one or some topic(s) instead of all topics, which leads to significantly improved topic coherence. Moreover, the must-links are built and grouped with respect to specific object classes, thus the must-links in our approach are semantic-specific , which allows to more efficiently exploit discriminative prior knowledge from Web images. Extensive experiments validated the efficiency of our proposed approach on several data sets. It is shown that our method significantly improves topic coherence and outperforms the unsupervised methods for object discovery and localization. In addition, compared with discriminative methods, the naturally existing object classes in the given image collection can be subtly discovered, which makes our approach well suited for realistic applications of unsupervised object discovery.Unsupervised object discovery and localization is to discover some dominant object classes and localize all of object instances from a given image collection without any supervision. Previous work has attempted to tackle this problem with vanilla topic models, such as latent Dirichlet allocation (LDA). However, in those methods no prior knowledge for the given image collection is exploited to facilitate object discovery. On the other hand, the topic models used in those methods suffer from the topic coherence issue-some inferred topics do not have clear meaning, which limits the final performance of object discovery. In this paper, prior knowledge in terms of the so-called must-links are exploited from Web images on the Internet. Furthermore, a novel knowledge-based topic model, called LDA with mixture of Dirichlet trees, is proposed to incorporate the must-links into topic modeling for object discovery. In particular, to better deal with the polysemy phenomenon of visual words, the must-link is re-defined as that one must-link only constrains one or some topic(s) instead of all topics, which leads to significantly improved topic coherence. Moreover, the must-links are built and grouped with respect to specific object classes, thus the must-links in our approach are semantic-specific , which allows to more efficiently exploit discriminative prior knowledge from Web images. Extensive experiments validated the efficiency of our proposed approach on several data sets. It is shown that our method significantly improves topic coherence and outperforms the unsupervised methods for object discovery and localization. In addition, compared with discriminative methods, the naturally existing object classes in the given image collection can be subtly discovered, which makes our approach well suited for realistic applications of unsupervised object discovery.

Analytical Models of Exoplanetary Atmospheres. V. Non-gray Thermal Structure with Coherent Scattering

NASA Astrophysics Data System (ADS)

Mohandas, Gopakumar; Pessah, Martin E.; Heng, Kevin

2018-05-01

We apply the picket fence treatment to model the effects brought about by spectral lines on the thermal structure of irradiated atmospheres. The lines may be due to pure absorption processes, pure coherent scattering processes, or some combination of absorption and scattering. If the lines arise as a pure absorption process, the surface layers of the atmosphere are cooler, whereas this surface cooling is completely absent if the lines are due to pure coherent isotropic scattering. The lines also lead to a warming of the deeper atmosphere. The warming of the deeper layers is, however, independent of the nature of line formation. Accounting for coherent isotropic scattering in the shortwave and longwave continuum results in anti-greenhouse cooling and greenhouse warming on an atmosphere-wide scale. The effects of coherent isotropic scattering in the line and continuum operate in tandem to determine the resulting thermal structure of the irradiated atmosphere.

Why reread? Evidence from garden-path and local coherence structures.

PubMed

Christianson, Kiel; Luke, Steven G; Hussey, Erika K; Wochna, Kacey L

2017-07-01

Two eye-tracking experiments were conducted to compare the online reading and offline comprehension of main verb/reduced relative garden-path sentences and local coherence sentences. Rereading of early material in garden-path reduced relatives should be revisionary, aimed at reanalysing an earlier misparse; however, rereading of early material in a local coherence reduced relative need only be confirmatory, as the original parse of the earlier portion of these sentences is ultimately correct. Results of online and offline measures showed that local coherence structures elicited signals of reading disruption that arose earlier and lasted longer, and local coherence comprehension was also better than garden path comprehension. Few rereading measures in either sentence type were predicted by structural features of these sentences, nor was rereading related to comprehension accuracy, which was extremely low overall. Results are discussed with respect to selective reanalysis and good-enough processing.

Hippocampal-medial prefrontal circuit supports memory updating during learning and post-encoding rest

PubMed Central

Schlichting, Margaret L.; Preston, Alison R.

2015-01-01

Learning occurs in the context of existing memories. Encountering new information that relates to prior knowledge may trigger integration, whereby established memories are updated to incorporate new content. Here, we provide a critical test of recent theories suggesting hippocampal (HPC) and medial prefrontal (MPFC) involvement in integration, both during and immediately following encoding. Human participants with established memories for a set of initial (AB) associations underwent fMRI scanning during passive rest and encoding of new related (BC) and unrelated (XY) pairs. We show that HPC-MPFC functional coupling during learning was more predictive of trial-by-trial memory for associations related to prior knowledge relative to unrelated associations. Moreover, the degree to which HPC-MPFC functional coupling was enhanced following overlapping encoding was related to memory integration behavior across participants. We observed a dissociation between anterior and posterior MPFC, with integration signatures during post-encoding rest specifically in the posterior subregion. These results highlight the persistence of integration signatures into post-encoding periods, indicating continued processing of interrelated memories during rest. We also interrogated the coherence of white matter tracts to assess the hypothesis that integration behavior would be related to the integrity of the underlying anatomical pathways. Consistent with our predictions, more coherent HPC-MPFC white matter structure was associated with better performance across participants. This HPC-MPFC circuit also interacted with content-sensitive visual cortex during learning and rest, consistent with reinstatement of prior knowledge to enable updating. These results show that the HPC-MPFC circuit supports on- and offline integration of new content into memory. PMID:26608407

Relaxation mechanisms, structure and properties of semi-coherent interfaces

DOE PAGES

Shao, Shuai; Wang, Jian

2015-10-15

In this work, using the Cu–Ni (111) semi-coherent interface as a model system, we combine atomistic simulations and defect theory to reveal the relaxation mechanisms, structure, and properties of semi-coherent interfaces. By calculating the generalized stacking fault energy (GSFE) profile of the interface, two stable structures and a high-energy structure are located. During the relaxation, the regions that possess the stable structures expand and develop into coherent regions; the regions with high-energy structure shrink into the intersection of misfit dislocations (nodes). This process reduces the interface excess potential energy but increases the core energy of the misfit dislocations and nodes.more » The core width is dependent on the GSFE of the interface. The high-energy structure relaxes by relative rotation and dilatation between the crystals. The relative rotation is responsible for the spiral pattern at nodes. The relative dilatation is responsible for the creation of free volume at nodes, which facilitates the nodes’ structural transformation. Several node structures have been observed and analyzed. In conclusion, the various structures have significant impact on the plastic deformation in terms of lattice dislocation nucleation, as well as the point defect formation energies.« less

Generalized Lagrangian coherent structures

NASA Astrophysics Data System (ADS)

Balasuriya, Sanjeeva; Ouellette, Nicholas T.; Rypina, Irina I.

2018-06-01

The notion of a Lagrangian Coherent Structure (LCS) is by now well established as a way to capture transient coherent transport dynamics in unsteady and aperiodic fluid flows that are known over finite time. We show that the concept of an LCS can be generalized to capture coherence in other quantities of interest that are transported by, but not fully locked to, the fluid. Such quantities include those with dynamic, biological, chemical, or thermodynamic relevance, such as temperature, pollutant concentration, vorticity, kinetic energy, plankton density, and so on. We provide a conceptual framework for identifying the Generalized Lagrangian Coherent Structures (GLCSs) associated with such evolving quantities. We show how LCSs can be seen as a special case within this framework, and provide an overarching discussion of various methods for identifying LCSs. The utility of this more general viewpoint is highlighted through a variety of examples. We also show that although LCSs approximate GLCSs in certain limiting situations under restrictive assumptions on how the velocity field affects the additional quantities of interest, LCSs are not in general sufficient to describe their coherent transport.

Dynamical Fano-Like Interference between Rabi Oscillations and Coherent Phonons in a Semiconductor Microcavity System.

PubMed

Yoshino, S; Oohata, G; Mizoguchi, K

2015-10-09

We report on dynamical interference between short-lived Rabi oscillations and long-lived coherent phonons in CuCl semiconductor microcavities resulting from the coupling between the two oscillations. The Fourier-transformed spectra of the time-domain signals obtained from semiconductor microcavities by using a pump-probe technique show that the intensity of the coherent longitudinal optical phonon of CuCl is enhanced by increasing that of the Rabi oscillation, which indicates that the coherent phonon is driven by the Rabi oscillation through the Fröhlich interaction. Moreover, as the Rabi oscillation frequency decreases upon crossing the phonon frequency, the spectral profile of the coherent phonon changes from a peak to a dip with an asymmetric structure. The continuous wavelet transformation reveals that these peak and dip structures originate from constructive and destructive interference between Rabi oscillations and coherent phonons, respectively. We demonstrate that the asymmetric spectral structures in relation to the frequency detuning are well reproduced by using a classical coupled oscillator model on the basis of dynamical Fano-like interference.

Tracking coherent structures in massively-separated and turbulent flows

NASA Astrophysics Data System (ADS)

Rockwood, Matthew; Huang, Yangzi; Green, Melissa

2018-01-01

Coherent vortex structures are tracked in simulations of massively-separated and turbulent flows. Topological Lagrangian saddle points are found using intersections of the positive and negative finite-time Lyapunov exponent ridges, and these points are then followed in order to track individual coherent structure motion both in a complex interacting three-dimensional flow (turbulent channel) and during vortex formation (two-dimensional bluff body shedding). For a simulation of wall-bounded turbulence in a channel flow, tracking Lagrangian saddles shows that the average structure convection speed exhibits a similar trend as a previously published result based on velocity and pressure correlations, giving validity to the method. When this tracking method is applied in a study of a circular cylinder in cross-flow it shows that Lagrangian saddles rapidly accelerate away from the cylinder surface as the vortex sheds. This saddle behavior is compared with the time-resolved static pressure distribution on the circular cylinder, yielding locations on a cylinder surface where common sensors could detect this phenomenon, which is not available from force measurements or vortex circulation calculations. The current method of tracking coherent structures yields insight into the behavior of the coherent structures in both of the diverse flows presented, highlighting the breadth of its potential application.

A perspective on coherent structures and conceptual models for turbulent boundary layer physics

NASA Technical Reports Server (NTRS)

Robinson, Stephen K.

1990-01-01

Direct numerical simulations of turbulent boundary layers have been analyzed to develop a unified conceptual model for the kinematics of coherent motions in low Reynolds number canonical turbulent boundary layers. All classes of coherent motions are considered in the model, including low-speed streaks, ejections and sweeps, vortical structures, near-wall and outer-region shear layers, sublayer pockets, and large-scale outer-region eddies. The model reflects the conclusions from the study of the simulated boundary layer that vortical structures are directly associated with the production of turbulent shear stresses, entrainment, dissipation of turbulence kinetic energy, and the fluctuating pressure field. These results, when viewed from the perspective of the large body of published work on the subject of coherent motions, confirm that vortical structures may be considered the central dynamic element in the maintenance of turbulence in the canonical boundary layer. Vortical structures serve as a framework on which to construct a unified picture of boundary layer structure, providing a means to relate the many known structural elements in a consistent way.

Schema Theory Compared to Text-centered Theory as an Explanation for the Reader's Understanding of a Business Message.

ERIC Educational Resources Information Center

Faris, Kay A.; Smeltzer, Larry R.

1997-01-01

Examines variables affecting reader understanding of business writing. Notes that 57 business students and 82 non-business students read either a coherent or a non-coherent version of the same text and then took a test measuring their comprehension. Finds that background knowledge (schema theory) affected a reader's ability to understand business…

Imaging of dental material by polarization-sensitive optical coherence tomography

NASA Astrophysics Data System (ADS)

Dichtl, Sabine; Baumgartner, Angela; Hitzenberger, Christoph K.; Moritz, Andreas; Wernisch, Johann; Robl, Barbara; Sattmann, Harald; Leitgeb, Rainer; Sperr, Wolfgang; Fercher, Adolf F.

1999-05-01

Partial coherence interferometry (PCI) and optical coherence tomography (OCT) are noninvasive and noncontact techniques for high precision biometry and for obtaining cross- sectional images of biologic structures. OCT was initially introduced to depict the transparent tissue of the eye. It is based on interferometry employing the partial coherence properties of a light source with high spatial coherence ut short coherence length to image structures with a resolution of the order of a few microns. Recently this technique has been modified for cross section al imaging of dental and periodontal tissues. In vitro and in vivo OCT images have been recorded, which distinguish enamel, cemento and dentin structures and provide detailed structural information on clinical abnormalities. In contrast to convention OCT, where the magnitude of backscattered light as a function of depth is imaged, polarization sensitive OCT uses backscattered light to image the magnitude of the birefringence in the sample as a function of depth. First polarization sensitive OCT recordings show, that changes in the mineralization status of enamel or dentin caused by caries or non-caries lesions can result in changes of the polarization state of the light backscattered by dental material. Therefore polarization sensitive OCT might provide a new diagnostic imaging modality in clinical and research dentistry.

Coherency of a Teacher's Proportional Reasoning Knowledge in and out of the Classroom

ERIC Educational Resources Information Center

Brown, Rachael Eriksen; Nagar, Gili Gal; Orrill, Chandra Hawley; Weiland, Travis; Burke, James

2016-01-01

In this exploratory study we considered how one teacher's understanding of proportional reasoning related to his teaching. We used Epistemic Network Analysis to consider the teachers' knowledge organization and connections between knowledge resources as a way to make sense of his understanding. Then, we examined how his understanding was reflected…

Wavelet detection of coherent structures in interplanetary magnetic flux ropes and its role in the intermittent turbulence

NASA Astrophysics Data System (ADS)

Muñoz, P. R.; Chian, A. C.

2013-12-01

We implement a method to detect coherent magnetic structures using the Haar discrete wavelet transform (Salem et al., ApJ 702, 537, 2009), and apply it to an event detected by Cluster at the turbulent boundary layer of an interplanetary magnetic flux rope. The wavelet method is able to detect magnetic coherent structures and extract main features of solar wind intermittent turbulence, such as the power spectral density and the scaling exponent of structure functions. Chian and Muñoz (ApJL 733, L34, 2011) investigated the relation between current sheets, turbulence, and magnetic reconnections at the leading edge of an interplanetary coronal mass ejection measured by Cluster upstream of the Earth's bow shock on 2005 January 21. We found observational evidence of two magnetically reconnected current sheets in the vicinity of a front magnetic cloud boundary layer, where the scaling exponent of structure functions of magnetic fluctuations exhibits multifractal behavior. Using the wavelet technique, we show that the current sheets associated to magnetic reconnection are part of the set of magnetic coherent structures responsible for multifractality. By removing them using a filtering criteria, it is possible to recover a self-similar scaling exponent predicted for homogeneous turbulence. Finally, we discuss an extension of the wavelet technique to study coherent structures in two-dimensional solar magnetograms.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsytovich, Vadim, E-mail: tsytov@lpi.ru; Max Planck Institute for Extraterrestrial Physics, Garching; Gusein-zade, Namik

Dust structuring is a natural and universal process in complex plasmas. The scattering of electromagnetic waves by dust structures is governed by the factor of coherency, i.e., the total number of coherent electrons in a single structure. In the present paper, we consider how the factor of coherency changes due to additional pulse electron heating and show that it obeys a hysteresis. After the end of the pulse heating, the scattering intensity differs substantially from that before heating. There are three necessary conditions for scattering hysteresis: first, the radiation wavelength should be larger than the pattern (structure) size; second, themore » total number of coherent electrons confined by the structure should be large; and third, the heating pulse duration should be shorter than the characteristic time of dust structure formation. We present the results of numerical calculations using existing models of self-consistent dust structures with either positively or negatively charged dust grains. It is shown that, depending on the grain charge and the ionization rate, two types of hysteresis are possible: one with a final increase of the scattering and the other with a final decrease of the scattering. It is suggested that the hysteresis of coherent scattering can be used as a tool in laboratory experiments and that it can be a basic mechanism explaining the observed hysteresis in radar scattering by noctilucent clouds during active experiments on electron heating in mesosphere.« less

Doppler optical coherence microscopy and tomography applied to inner ear mechanics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Page, Scott; Freeman, Dennis M.; Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, Cambridge, Massachusetts

While it is clear that cochlear traveling waves underlie the extraordinary sensitivity, frequency selectivity, and dynamic range of mammalian hearing, the underlying micromechanical mechanisms remain unresolved. Recent advances in low coherence measurement techniques show promise over traditional laser Doppler vibrometry and video microscopy, which are limited by low reflectivities of cochlear structures and restricted optical access. Doppler optical coherence tomography (DOCT) and Doppler optical coherence microscopy (DOCM) both utilize a broadband source to limit constructive interference of scattered light to a small axial depth called a coherence gate. The coherence gate can be swept axially to image and measure sub-nanometermore » motions of cochlear structures throughout the cochlear partition. The coherence gate of DOCT is generally narrower than the confocal gate of the focusing optics, enabling increased axial resolution (typically 15 μm) within optical sections of the cochlear partition. DOCM, frequently implemented in the time domain, centers the coherence gate on the focal plane, achieving enhanced lateral and axial resolution when the confocal gate is narrower than the coherence gate. We compare these two complementary systems and demonstrate their utility in studying cellular and micromechanical mechanisms involved in mammalian hearing.« less

Data-driven sensor placement from coherent fluid structures

NASA Astrophysics Data System (ADS)

Manohar, Krithika; Kaiser, Eurika; Brunton, Bingni W.; Kutz, J. Nathan; Brunton, Steven L.

2017-11-01

Optimal sensor placement is a central challenge in the prediction, estimation and control of fluid flows. We reinterpret sensor placement as optimizing discrete samples of coherent fluid structures for full state reconstruction. This permits a drastic reduction in the number of sensors required for faithful reconstruction, since complex fluid interactions can often be described by a small number of coherent structures. Our work optimizes point sensors using the pivoted matrix QR factorization to sample coherent structures directly computed from flow data. We apply this sampling technique in conjunction with various data-driven modal identification methods, including the proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD). In contrast to POD-based sensors, DMD demonstrably enables the optimization of sensors for prediction in systems exhibiting multiple scales of dynamics. Finally, reconstruction accuracy from pivot sensors is shown to be competitive with sensors obtained using traditional computationally prohibitive optimization methods.

An adaptive deep-coupled GNSS/INS navigation system with hybrid pre-filter processing

NASA Astrophysics Data System (ADS)

Wu, Mouyan; Ding, Jicheng; Zhao, Lin; Kang, Yingyao; Luo, Zhibin

2018-02-01

The deep-coupling of a global navigation satellite system (GNSS) with an inertial navigation system (INS) can provide accurate and reliable navigation information. There are several kinds of deeply-coupled structures. These can be divided mainly into coherent and non-coherent pre-filter based structures, which have their own strong advantages and disadvantages, especially in accuracy and robustness. In this paper, the existing pre-filters of the deeply-coupled structures are analyzed and modified to improve them firstly. Then, an adaptive GNSS/INS deeply-coupled algorithm with hybrid pre-filters processing is proposed to combine the advantages of coherent and non-coherent structures. An adaptive hysteresis controller is designed to implement the hybrid pre-filters processing strategy. The simulation and vehicle test results show that the adaptive deeply-coupled algorithm with hybrid pre-filters processing can effectively improve navigation accuracy and robustness, especially in a GNSS-challenged environment.

Coherent Structures and Extreme Events in Rotating Multiphase Turbulent Flows

NASA Astrophysics Data System (ADS)

Biferale, L.; Bonaccorso, F.; Mazzitelli, I. M.; van Hinsberg, M. A. T.; Lanotte, A. S.; Musacchio, S.; Perlekar, P.; Toschi, F.

2016-10-01

By using direct numerical simulations (DNS) at unprecedented resolution, we study turbulence under rotation in the presence of simultaneous direct and inverse cascades. The accumulation of energy at large scale leads to the formation of vertical coherent regions with high vorticity oriented along the rotation axis. By seeding the flow with millions of inertial particles, we quantify—for the first time—the effects of those coherent vertical structures on the preferential concentration of light and heavy particles. Furthermore, we quantitatively show that extreme fluctuations, leading to deviations from a normal-distributed statistics, result from the entangled interaction of the vertical structures with the turbulent background. Finally, we present the first-ever measurement of the relative importance between Stokes drag, Coriolis force, and centripetal force along the trajectories of inertial particles. We discover that vortical coherent structures lead to unexpected diffusion properties for heavy and light particles in the directions parallel and perpendicular to the rotation axis.

Identification of individual coherent sets associated with flow trajectories using Coherent Structure Coloring

NASA Astrophysics Data System (ADS)

Schlueter-Kuck, Kristy; Dabiri, John

2017-11-01

In recent years, there has been a proliferation of techniques that aim to characterize fluid flow kinematics on the basis of Lagrangian trajectories of collections of tracer particles. Most of these techniques depend on presence of tracer particles that are initially closely-spaced, in order to compute local gradients of their trajectories. In many applications, the requirement of close tracer spacing cannot be satisfied, especially when the tracers are naturally occurring and their distribution is dictated by the underlying flow. Moreover, current methods often focus on determination of the boundaries of coherent sets, whereas in practice it is often valuable to identify the complete set of trajectories that are coherent with an individual trajectory of interest. We extend the concept of Coherent Structure Coloring to achieve identification of the coherent set associated with individual Lagrangian trajectories. This algorithm is proven successful in identifying coherent structures of varying complexities in canonical unsteady flows. Importantly, although the method is demonstrated here in the context of fluid flow kinematics, the generality of the approach allows for its potential application to other unsupervised clustering problems in dynamical systems. This work was supported by the Department of Defense (DoD) through the National Defense Science & Engineering Graduate Fellowship (NDSEG) Program.

Electronic structure and relative stability of the coherent and semi-coherent HfO2/III-V interfaces

NASA Astrophysics Data System (ADS)

Lahti, A.; Levämäki, H.; Mäkelä, J.; Tuominen, M.; Yasir, M.; Dahl, J.; Kuzmin, M.; Laukkanen, P.; Kokko, K.; Punkkinen, M. P. J.

2018-01-01

III-V semiconductors are prominent alternatives to silicon in metal oxide semiconductor devices. Hafnium dioxide (HfO2) is a promising oxide with a high dielectric constant to replace silicon dioxide (SiO2). The potentiality of the oxide/III-V semiconductor interfaces is diminished due to high density of defects leading to the Fermi level pinning. The character of the harmful defects has been intensively debated. It is very important to understand thermodynamics and atomic structures of the interfaces to interpret experiments and design methods to reduce the defect density. Various realistic gap defect state free models for the HfO2/III-V(100) interfaces are presented. Relative energies of several coherent and semi-coherent oxide/III-V semiconductor interfaces are determined for the first time. The coherent and semi-coherent interfaces represent the main interface types, based on the Ga-O bridges and As (P) dimers, respectively.

Photovoltaic concepts inspired by coherence effects in photosynthetic systems

NASA Astrophysics Data System (ADS)

Brédas, Jean-Luc; Sargent, Edward H.; Scholes, Gregory D.

2017-01-01

The past decade has seen rapid advances in our understanding of how coherent and vibronic phenomena in biological photosynthetic systems aid in the efficient transport of energy from light-harvesting antennas to photosynthetic reaction centres. Such coherence effects suggest strategies to increase transport lengths even in the presence of structural disorder. Here we explore how these principles could be exploited in making improved solar cells. We investigate in depth the case of organic materials, systems in which energy and charge transport stand to be improved by overcoming challenges that arise from the effects of static and dynamic disorder -- structural and energetic -- and from inherently strong electron-vibration couplings. We discuss how solar-cell device architectures can evolve to use coherence-exploiting materials, and we speculate as to the prospects for a coherent energy conversion system. We conclude with a survey of the impacts of coherence and bioinspiration on diverse solar-energy harvesting solutions, including artificial photosynthetic systems.

Time-frequency analysis of submerged synthetic jet

NASA Astrophysics Data System (ADS)

Kumar, Abhay; Saha, Arun K.; Panigrahi, P. K.

2017-12-01

The coherent structures transport the finite body of fluid mass through rolling which plays an important role in heat transfer, boundary layer control, mixing, cooling, propulsion and other engineering applications. A synthetic jet in the form of a train of vortex rings having coherent structures of different length scales is expected to be useful in these applications. The propagation and sustainability of these coherent structures (vortex rings) in downstream direction characterize the performance of synthetic jet. In the present study, the velocity signal acquired using the S-type hot-film probe along the synthetic jet centerline has been taken for the spectral analysis. One circular and three rectangular orifices of aspect ratio 1, 2 and 4 actuating at 1, 6 and 18 Hz frequency have been used for creating different synthetic jets. The laser induced fluorescence images are used to study the flow structures qualitatively and help in explaining the velocity signal for detection of coherent structures. The study depicts four regions as vortex rollup and suction region (X/D h ≤ 3), steadily translating region (X/D h ≤ 3-8), vortex breakup region (X/Dh ≤ 4-8) and dissipation of small-scale vortices (X/D h ≤ 8-15). The presence of coherent structures localized in physical and temporal domain is analyzed for the characterization of synthetic jet. Due to pulsatile nature of synthetic jet, analysis of velocity time trace or signal in time, frequency and combined time-frequency domain assist in characterizing the signatures of coherent structures. It has been observed that the maximum energy is in the first harmonic of actuation frequency, which decreases slowly in downstream direction at 6 Hz compared to 1 and 18 Hz of actuation.

Uncovering a new quasi-2D CuO2 plane between the YBa2Cu3O7 and CeO2 buffer layer of coated conductors

NASA Astrophysics Data System (ADS)

Li, Zhi-Xin; Cao, Jin-Jin; Gou, Xiao-Fan; Wang, Tian-Ge; Xue, Feng

2018-01-01

We report a discovery of the quasi-two-dimensional (quasi-2D) CuO2 plane between the superconductor YBa2Cu3O7 (YBCO) and CeO2 buffer layer (mostly used in the fabrication) of coated conductors through the atomistic computer simulations with the molecular dynamics (MD) and first-principle calculations. For an YBCO coated conductor with multilayer structures, the buffer layers deposited onto a substrate are mainly considered to transfer a strong biaxial texture from the substrate to the YBCO layer. To deeply understand the tuning mechanism of the texture transfer, exploring the complete atomic-level picture of the structure between the YBa2Cu3O7/CeO2 interfaces is firstly required. However, the related observation data have not been available due to some big challenges of experimental techniques. With the MD simulations, having tested the accuracy of the potential functions for the YBa2Cu3O7/CeO2 interface, we constructed a total of 54 possible atom stacking models of the interface and identified its most appropriate and stable structure according to the criterion of the interface adhesion energy and the coherent characterization. To further verify the stability of the identified structure, we performed the first-principle calculations to obtain the adhesion energy and developed the general knowledge of the interface structure. Finally, a coherent interface formed with a new built quasi-2D CuO2 plane that is structurally similar to the CuO2 plane inside bulk YBCO was determined.

Imaging of the optic nerve and retinal nerve fiber layer: an essential part of glaucoma diagnosis and monitoring.

PubMed

Kotowski, Jacek; Wollstein, Gadi; Ishikawa, Hiroshi; Schuman, Joel S

2014-01-01

Because glaucomatous damage is irreversible early detection of structural changes in the optic nerve head and retinal nerve fiber layer is imperative for timely diagnosis of glaucoma and monitoring of its progression. Significant improvements in ocular imaging have been made in recent years. Imaging techniques such as optical coherence tomography, scanning laser polarimetry and confocal scanning laser ophthalmoscopy rely on different properties of light to provide objective structural assessment of the optic nerve head, retinal nerve fiber layer and macula. In this review, we discuss the capabilities of these imaging modalities pertinent for diagnosis of glaucoma and detection of progressive glaucomatous damage and provide a review of the current knowledge on the clinical performance of these technologies. Copyright © 2014 Elsevier Inc. All rights reserved.

Coherent Structure Detection using Persistent Homology and other Topological Tools

NASA Astrophysics Data System (ADS)

Smith, Spencer; Roberts, Eric; Sindi, Suzanne; Mitchell, Kevin

2017-11-01

For non-autonomous, aperiodic fluid flows, coherent structures help organize the dynamics, much as invariant manifolds and periodic orbits do for autonomous or periodic systems. The prevalence of such flows in nature and industry has motivated many successful techniques for defining and detecting coherent structures. However, often these approaches require very fine trajectory data to reconstruct velocity fields and compute Cauchy-Green-tensor-related quantities. We use topological techniques to help detect coherent trajectory sets in relatively sparse 2D advection problems. More specifically, we have developed a homotopy-based algorithm, the ensemble-based topological entropy calculation (E-tec), which assigns to each edge in an initial triangulation of advected points a topologically forced lower bound on its future stretching rate. The triangulation and its weighted edges allow us to analyze flows using persistent homology. This topological data analysis tool detects clusters and loops in the triangulation that are robust in the presence of noise and in this case correspond to coherent trajectory sets.

Noise-gating to Clean Astrophysical Image Data

DOE Office of Scientific and Technical Information (OSTI.GOV)

DeForest, C. E.

I present a family of algorithms to reduce noise in astrophysical images and image sequences, preserving more information from the original data than is retained by conventional techniques. The family uses locally adaptive filters (“noise gates”) in the Fourier domain to separate coherent image structure from background noise based on the statistics of local neighborhoods in the image. Processing of solar data limited by simple shot noise or by additive noise reveals image structure not easily visible in the originals, preserves photometry of observable features, and reduces shot noise by a factor of 10 or more with little to nomore » apparent loss of resolution. This reveals faint features that were either not directly discernible or not sufficiently strongly detected for quantitative analysis. The method works best on image sequences containing related subjects, for example movies of solar evolution, but is also applicable to single images provided that there are enough pixels. The adaptive filter uses the statistical properties of noise and of local neighborhoods in the data to discriminate between coherent features and incoherent noise without reference to the specific shape or evolution of those features. The technique can potentially be modified in a straightforward way to exploit additional a priori knowledge about the functional form of the noise.« less

In Silico Mining for Antimalarial Structure-Activity Knowledge and Discovery of Novel Antimalarial Curcuminoids.

PubMed

Viira, Birgit; Gendron, Thibault; Lanfranchi, Don Antoine; Cojean, Sandrine; Horvath, Dragos; Marcou, Gilles; Varnek, Alexandre; Maes, Louis; Maran, Uko; Loiseau, Philippe M; Davioud-Charvet, Elisabeth

2016-06-29

Malaria is a parasitic tropical disease that kills around 600,000 patients every year. The emergence of resistant Plasmodium falciparum parasites to artemisinin-based combination therapies (ACTs) represents a significant public health threat, indicating the urgent need for new effective compounds to reverse ACT resistance and cure the disease. For this, extensive curation and homogenization of experimental anti-Plasmodium screening data from both in-house and ChEMBL sources were conducted. As a result, a coherent strategy was established that allowed compiling coherent training sets that associate compound structures to the respective antimalarial activity measurements. Seventeen of these training sets led to the successful generation of classification models discriminating whether a compound has a significant probability to be active under the specific conditions of the antimalarial test associated with each set. These models were used in consensus prediction of the most likely active from a series of curcuminoids available in-house. Positive predictions together with a few predicted as inactive were then submitted to experimental in vitro antimalarial testing. A large majority from predicted compounds showed antimalarial activity, but not those predicted as inactive, thus experimentally validating the in silico screening approach. The herein proposed consensus machine learning approach showed its potential to reduce the cost and duration of antimalarial drug discovery.

Noise-gating to Clean Astrophysical Image Data

NASA Astrophysics Data System (ADS)

DeForest, C. E.

2017-04-01

I present a family of algorithms to reduce noise in astrophysical images and image sequences, preserving more information from the original data than is retained by conventional techniques. The family uses locally adaptive filters (“noise gates”) in the Fourier domain to separate coherent image structure from background noise based on the statistics of local neighborhoods in the image. Processing of solar data limited by simple shot noise or by additive noise reveals image structure not easily visible in the originals, preserves photometry of observable features, and reduces shot noise by a factor of 10 or more with little to no apparent loss of resolution. This reveals faint features that were either not directly discernible or not sufficiently strongly detected for quantitative analysis. The method works best on image sequences containing related subjects, for example movies of solar evolution, but is also applicable to single images provided that there are enough pixels. The adaptive filter uses the statistical properties of noise and of local neighborhoods in the data to discriminate between coherent features and incoherent noise without reference to the specific shape or evolution of those features. The technique can potentially be modified in a straightforward way to exploit additional a priori knowledge about the functional form of the noise.

Graph theoretical analysis of EEG functional connectivity during music perception.

PubMed

Wu, Junjie; Zhang, Junsong; Liu, Chu; Liu, Dongwei; Ding, Xiaojun; Zhou, Changle

2012-11-05

The present study evaluated the effect of music on large-scale structure of functional brain networks using graph theoretical concepts. While most studies on music perception used Western music as an acoustic stimulus, Guqin music, representative of Eastern music, was selected for this experiment to increase our knowledge of music perception. Electroencephalography (EEG) was recorded from non-musician volunteers in three conditions: Guqin music, noise and silence backgrounds. Phase coherence was calculated in the alpha band and between all pairs of EEG channels to construct correlation matrices. Each resulting matrix was converted into a weighted graph using a threshold, and two network measures: the clustering coefficient and characteristic path length were calculated. Music perception was found to display a higher level mean phase coherence. Over the whole range of thresholds, the clustering coefficient was larger while listening to music, whereas the path length was smaller. Networks in music background still had a shorter characteristic path length even after the correction for differences in mean synchronization level among background conditions. This topological change indicated a more optimal structure under music perception. Thus, prominent small-world properties are confirmed in functional brain networks. Furthermore, music perception shows an increase of functional connectivity and an enhancement of small-world network organizations. Copyright © 2012 Elsevier B.V. All rights reserved.

Forms of Knowledge and Curriculum Coherence

ERIC Educational Resources Information Center

Muller, Johan

2009-01-01

This paper examines what is entailed by taking a socio-epistemic or "knowledge-based" approach to considerations of curriculum and qualifications. The paper begins by examining the roots of disciplinary difference in the medieval universities and their treatment in contemporary scholarly work; discusses implications for curriculum and…

Laser Doppler velocimeter measurements of boundary layer velocity and turbulent intensities in Mach 2.5 flow

NASA Technical Reports Server (NTRS)

Sewell, Jesse; Chew, Larry

1994-01-01

In recent years, the interest in developing a high-speed civil transport has increased. This has led to an increase in research activity on compressible supersonic flows, in particular the boundary layer. The structure of subsonic boundary layers has been extensively documented using conditional sampling techniques which exploit the knowledge of both u and v velocities. Researchers using these techniques have been able to explore some of the complex three-dimensional motions which are responsible for Reynolds stress production and transport in the boundary layer. As interest in turbulent structure has grown to include supersonic flows, a need for simultaneous multicomponent velocity measurements in these flows has developed. The success of conditional analysis in determining the characteristics of coherent motions and structures in the boundary layer relies on accurate, simultaneous measurement of two instantaneous velocity components.

Observation and control of coherent torsional dynamics in a quinquethiophene molecule.

PubMed

Cirmi, Giovanni; Brida, Daniele; Gambetta, Alessio; Piacenza, Manuel; Della Sala, Fabio; Favaretto, Laura; Cerullo, Giulio; Lanzani, Guglielmo

2010-07-28

By applying femtosecond pump-probe spectroscopy to a substituted quinquethiophene molecule in solution, we observe in the time domain the coherent torsional dynamics that drives planarization of the excited state. Our interpretation is based on numerical modeling of the ground and excited state potential energy surfaces and simulation of wavepacket dynamics, which reveals two symmetric excited state deactivation pathways per oscillation period. We use the acquired knowledge on torsional dynamics to coherently control the excited state population with a pump-dump scheme, exploiting the non-stationary Franck-Condon overlap between ground and excited states.

Femtosecond pulse shaping using the geometric phase.

PubMed

Gökce, Bilal; Li, Yanming; Escuti, Michael J; Gundogdu, Kenan

2014-03-15

We demonstrate a femtosecond pulse shaper that utilizes polarization gratings to manipulate the geometric phase of an optical pulse. This unique approach enables circular polarization-dependent shaping of femtosecond pulses. As a result, it is possible to create coherent pulse pairs with orthogonal polarizations in a 4f pulse shaper setup, something until now that, to our knowledge, was only achieved via much more complex configurations. This approach could be used to greatly simplify and enhance the functionality of multidimensional spectroscopy and coherent control experiments, in which multiple coherent pulses are used to manipulate quantum states in materials of interest.

The cohering telomeres of Oxytricha.

PubMed Central

Oka, Y; Thomas, C A

1987-01-01

We have studied the process by which purified Oxytricha macronuclear DNA associates with itself to form large aggregates. The various macronuclear DNA molecules all have the same terminal or telomeric DNA sequences that are shown below. 5' C4A4C4A4C4--mean length----G4T4G4T4G4T4G4T4G4 G4T4G4T4G4T4G4T4G4-----2.4 kb------C4A4C4A4C4. When incubated at high concentrations, these telomeric sequences cohere with one another to form an unusual structure--one that is quite different from any DNA structure so far described. The evidence for this is the following: 1) These sequences cohere albeit slowly, in the presence of relatively high concentrations of Na+, and no other cation tested. This contrasts with the rapid coherence of complementary single-chain terminals of normal DNA (sticky ends) which occurs in the presence of any cation tested. 2) If the cohered form is transferred into buffers containing a special cation, K+, it becomes much more resistant to dissociation by heating. We estimate that K+ increases the thermal stability by 25 degrees or more. The only precedent known (to us) for a cation-specific stabilization is that seen in the quadruplex structure formed by poly I. The thermal stability of double helical macronuclear DNA depends on the cation concentration, but not the cation type. Limited treatment with specific nucleases show that the 3' and 5'-ended strands are essential for the formation of the cohering structure. Once in the cohered form, the telomeric sequences are protected from the action of nucleases. Coherence is inhibited by specific, but not by non-specific, synthetic oligomers, and by short telomeric fragments with or without their terminal single chains. We conclude that the coherence occurs by the formation of a novel condensed structure that involves the terminal nucleotides in three or four chains. Images PMID:3120149

Observation of correlation between route to formation, coherence, noise, and communication performance of Kerr combs

NASA Astrophysics Data System (ADS)

Wang, Pei-Hsun; Ferdous, Fahmida; Miao, Houxun; Wang, Jian; Leaird, Daniel E.; Srinivasan, Kartik; Chen, Lei; Aksyuk, Vladimir; Weiner, Andrew M.

2012-12-01

Microresonator optical frequency combs based on cascaded four-wave mixing are potentially attractive as a multi-wavelength source for on-chip optical communications. In this paper we compare time domain coherence, radio-frequency (RF) intensity noise, and individual line optical communications performance for combs generated from two different silicon nitride microresonators. The comb generated by one microresonator forms directly with lines spaced by a single free spectral range (FSR) and exhibits high coherence, low noise, and excellent 10 Gbit/s optical communications results. The comb generated by the second microresonator forms initially with multiple FSR line spacing, with additional lines later filling to reach single FSR spacing. This comb exhibits degraded coherence, increased intensity noise, and severely degraded communications performance. This study is to our knowledge the first to simultaneously investigate and observe a correlation between the route to comb formation, the coherence, noise, and optical communications performance of a Kerr comb.

Coherent structures in axisymmetric jets

NASA Astrophysics Data System (ADS)

Durao, D. F. G.; Nina, M. N. R.; Pita, G.

Laser Doppler anemometry has been used to measure the mean and rms values of the axial and radial velocity components in jets with Reynolds numbers of up to 28,700. It is shown that even in flows that are not excited externally, coherent structures with Strouhal numbers of about 0.33 and 0.55 can be detected. The coherent structures associated with the higher Strouhal number are shown to result from vorticity at the edge of the jet. The oscillation associated with the lower Strouhal number is related to eddy breakdown and to the preferred vibration mode of axisymmetric jets.

Scale-by-scale energy budgets which account for the coherent motion

NASA Astrophysics Data System (ADS)

F, Thiesset; L, Danaila; A, Antonia R.; T, Zhou

2011-12-01

Scale-by-scale energy budget equations are written for flows where coherent structures may be prominent. Both general and locally isotropic formulations are provided. In particular, the contribution to the production, diffusion and energy transfer terms associated with the coherent motion is highlighted. Preliminary results are presented in the intermediate wake of a circular cylinder for phase-averaged second-and third-order structure functions. The experimental data provide adequate support for the scale-by-scale budgets.

Frequency conversion of structured light.

PubMed

Steinlechner, Fabian; Hermosa, Nathaniel; Pruneri, Valerio; Torres, Juan P

2016-02-15

Coherent frequency conversion of structured light, i.e. the ability to manipulate the carrier frequency of a wave front without distorting its spatial phase and intensity profile, provides the opportunity for numerous novel applications in photonic technology and fundamental science. In particular, frequency conversion of spatial modes carrying orbital angular momentum can be exploited in sub-wavelength resolution nano-optics and coherent imaging at a wavelength different from that used to illuminate an object. Moreover, coherent frequency conversion will be crucial for interfacing information stored in the high-dimensional spatial structure of single and entangled photons with various constituents of quantum networks. In this work, we demonstrate frequency conversion of structured light from the near infrared (803 nm) to the visible (527 nm). The conversion scheme is based on sum-frequency generation in a periodically poled lithium niobate crystal pumped with a 1540-nm Gaussian beam. We observe frequency-converted fields that exhibit a high degree of similarity with the input field and verify the coherence of the frequency-conversion process via mode projection measurements with a phase mask and a single-mode fiber. Our results demonstrate the suitability of exploiting the technique for applications in quantum information processing and coherent imaging.

Coherent structures in wall-bounded turbulence.

PubMed

Dennis, David J C

2015-01-01

The inherent difficulty of understanding turbulence has led to researchers attacking the topic in many different ways over the years of turbulence research. Some approaches have been more successful than others, but most only deal with part of the problem. One approach that has seen reasonable success (or at least popularity) is that of attempting to deconstruct the complex and disorganised turbulent flow field into to a set of motions that are in some way organised. These motions are generally called "coherent structures". There are several strands to this approach, from identifying the coherent structures within the flow, defining their characteristics, explaining how they are created, sustained and destroyed, to utilising their features to model the turbulent flow. This review considers research on coherent structures in wall-bounded turbulent flows: a class of flow which is extremely interesting to many scientists (mainly, but not exclusively, physicists and engineers) due to their prevalence in nature, industry and everyday life. This area has seen a lot of activity, particularly in recent years, much of which has been driven by advances in experimental and computational techniques. However, several ideas, developed many years ago based on flow visualisation and intuition, are still both informative and relevant. Indeed, much of the more recent research is firmly indebted to some of the early pioneers of the coherent structures approach. Therefore, in this review, selected historical research is discussed along with the more contemporary advances in an attempt to provide the reader with a good overview of how the field has developed and to highlight the perspicacity of some of the early researchers, as well as providing an overview of our current understanding of the role of coherent structures in wall-bounded turbulent flows.

COHeRE: Cross-Ontology Hierarchical Relation Examination for Ontology Quality Assurance.

PubMed

Cui, Licong

Biomedical ontologies play a vital role in healthcare information management, data integration, and decision support. Ontology quality assurance (OQA) is an indispensable part of the ontology engineering cycle. Most existing OQA methods are based on the knowledge provided within the targeted ontology. This paper proposes a novel cross-ontology analysis method, Cross-Ontology Hierarchical Relation Examination (COHeRE), to detect inconsistencies and possible errors in hierarchical relations across multiple ontologies. COHeRE leverages the Unified Medical Language System (UMLS) knowledge source and the MapReduce cloud computing technique for systematic, large-scale ontology quality assurance work. COHeRE consists of three main steps with the UMLS concepts and relations as the input. First, the relations claimed in source vocabularies are filtered and aggregated for each pair of concepts. Second, inconsistent relations are detected if a concept pair is related by different types of relations in different source vocabularies. Finally, the uncovered inconsistent relations are voted according to their number of occurrences across different source vocabularies. The voting result together with the inconsistent relations serve as the output of COHeRE for possible ontological change. The highest votes provide initial suggestion on how such inconsistencies might be fixed. In UMLS, 138,987 concept pairs were found to have inconsistent relationships across multiple source vocabularies. 40 inconsistent concept pairs involving hierarchical relationships were randomly selected and manually reviewed by a human expert. 95.8% of the inconsistent relations involved in these concept pairs indeed exist in their source vocabularies rather than being introduced by mistake in the UMLS integration process. 73.7% of the concept pairs with suggested relationship were agreed by the human expert. The effectiveness of COHeRE indicates that UMLS provides a promising environment to enhance qualities of biomedical ontologies by performing cross-ontology examination.

Self organization of exotic oil-in-oil phases driven by tunable electrohydrodynamics

PubMed Central

Varshney, Atul; Ghosh, Shankar; Bhattacharya, S.; Yethiraj, Anand

2012-01-01

Self organization of large-scale structures in nature - either coherent structures like crystals, or incoherent dynamic structures like clouds - is governed by long-range interactions. In many problems, hydrodynamics and electrostatics are the source of such long-range interactions. The tuning of electrostatic interactions has helped to elucidate when coherent crystalline structures or incoherent amorphous structures form in colloidal systems. However, there is little understanding of self organization in situations where both electrostatic and hydrodynamic interactions are present. We present a minimal two-component oil-in-oil model system where we can control the strength and lengthscale of the electrohydrodynamic interactions by tuning the amplitude and frequency of the imposed electric field. As a function of the hydrodynamic lengthscale, we observe a rich phenomenology of exotic structure and dynamics, from incoherent cloud-like structures and chaotic droplet dynamics, to polyhedral droplet phases, to coherent droplet arrays. PMID:23071902

Helical circulations in the typhoon boundary layer

NASA Astrophysics Data System (ADS)

Ellis, Ryan; Businger, Steven

2010-03-01

Low-level wind data from the WSR-88D in Guam obtained in Typhoon Dale (1996) and Typhoon Keith (1997) are analyzed for coherent structures. Consistent with the results of previous studies of Atlantic hurricanes, velocity anomalies associated with coherent structures were found in the boundary layer of both storms. A total of 99 cases of coherent structures, also known as roll vortices, were documented during a 6 h evaluation period for each storm. Storm-relative roll location, roll vorticity, asymmetries in the upward and downward momentum fluxes, and signatures of circulations transverse to the mean flow associated with roll circulations were explored. The effects of terrain and convective precipitation systems, such as rainbands, on the occurrence of rolls were investigated. The results support and extend prior findings of roll observations, and can be used to help validate theoretical and numerical models of coherent structures within tropical cyclones. Moreover, the wind variations documented in this study may have application for wave runup and wind damage potential in tropical cyclones.

Turbulence experiments on the PKU Plasma Test (PPT) device

NASA Astrophysics Data System (ADS)

Xu, Tianchao; Xiao, Chijie; Yang, Xiaoyi; Chen, Yihang; Yu, Yi; Xu, Min; Wang, Long; Lin, Chen; Wang, Xiaogang

2017-10-01

The PKU Plasma Test (PPT) device is a linear plasma device in Peking University, China. It has a vacuum chamber with 1000mm length and 500mm diameter. A pair of Helmholtz coils can generate toroidal magnetic field up to 2000 Gauss, and plasma was generated by a helicon source. Probes and fast camera were used to diagnose the parameters and got the turbulence spectrums, coherent structure, etc. The dynamics of turbulence, coherent structure and parameter profiles have been analyzed, and it has been found that the turbulence states are related to the equilibrium profiles; Some coherent structures exist and show strongly interactions with the background turbulences; The spatial and temporal evolutions of these coherent structures are related to the amplitude of the density gradient and electric field. These results will help on further studies of plasma transport. This work was supported by the National Natural Science Foundation of China under 11575014 and 11375053, CHINA MOST under 2012YQ030142 and ITER-CHINA program 2015GB120001.

Coherent perfect absorbers: linear control of light with light

NASA Astrophysics Data System (ADS)

Baranov, Denis G.; Krasnok, Alex; Shegai, Timur; Alù, Andrea; Chong, Yidong

2017-12-01

The absorption of electromagnetic energy by a material is a phenomenon that underlies many applications, including molecular sensing, photocurrent generation and photodetection. Typically, the incident energy is delivered to the system through a single channel, for example, by a plane wave incident on one side of an absorber. However, absorption can be made much more efficient by exploiting wave interference. A coherent perfect absorber is a system in which the complete absorption of electromagnetic radiation is achieved by controlling the interference of multiple incident waves. Here, we review recent advances in the design and applications of such devices. We present the theoretical principles underlying the phenomenon of coherent perfect absorption and give an overview of the photonic structures in which it can be realized, including planar and guided-mode structures, graphene-based systems, parity-symmetric and time-symmetric structures, 3D structures and quantum-mechanical systems. We then discuss possible applications of coherent perfect absorption in nanophotonics, and, finally, we survey the perspectives for the future of this field.

Coherence Effects in L-Band Active and Passive Remote Sensing of Quasi-Periodic Corn Canopies

NASA Technical Reports Server (NTRS)

Utku, Cuneyt; Lang, Roger H.

2011-01-01

Due to their highly random nature, vegetation canopies can be modeled using the incoherent transport theory for active and passive remote sensing applications. Agricultural vegetation canopies however are generally more structured than natural vegetation. The inherent row structure in agricultural canopies induces coherence effects disregarded by the transport theory. The objective of this study is to demonstrate, via Monte-Carlo simulations, these coherence effects on L-band scattering and thermal emission from corn canopies consisting of only stalks.

Development and calibration of mirrors and gratings for the Soft X-ray materials science beamline at the Linac Coherent Light Source free-electron laser

DOE PAGES

Soufli, Regina; Fernandez-Perea, Monica; Baker, Sherry L.; ...

2012-04-18

This article discusses the development and calibration of the x-ray reflective and diffractive elements for the Soft X-ray Materials Science (SXR) beamline of the Linac Coherent Light Source (LCLS) free-electron laser (FEL), designed for operation in the 500 – 2000 eV region. The surface topography of three Si mirror substrates and two Si diffraction grating substrates was examined by atomic force microscopy (AFM) and optical profilometry. The figure of the mirror substrates was also verified via surface slope measurements with a long trace profiler. A boron carbide (B 4C) coating especially optimized for the LCLS FEL conditions was deposited onmore » all SXR mirrors and gratings. Coating thickness uniformity of 0.14 nm root mean square (rms) across clear apertures extending to 205 mm length was demonstrated for all elements, as required to preserve the coherent wavefront of the LCLS source. The reflective performance of the mirrors and the diffraction efficiency of the gratings were calibrated at beamline 6.3.2 at the Advanced Light Source synchrotron. To verify the integrity of the nanometer-scale grating structure, the grating topography was examined by AFM before and after coating. This is to our knowledge the first time B 4C-coated diffraction gratings are demonstrated for operation in the soft x-ray region.« less

Modeling Coherent Structures in Canopy Flows

NASA Astrophysics Data System (ADS)

Luhar, Mitul

2017-11-01

It is well known that flows over vegetation canopies are characterized by the presence of energetic coherent structures. Since the mean profile over dense canopies exhibits an inflection point, the emergence of such structures is often attributed to a Kelvin-Helmholtz instability. However, though stability analyses provide useful mechanistic insights into canopy flows, they are limited in their ability to generate predictions for spectra and coherent structure. The present effort seeks to address this limitation by extending the resolvent formulation (McKeon and Sharma, 2010, J. Fluid Mech.) to canopy flows. Under the resolvent formulation, the turbulent velocity field is expressed as a superposition of propagating modes, identified via a gain-based (singular value) decomposition of the Navier-Stokes equations. A key advantage of this approach is that it reconciles multiple mechanisms that lead to high amplification in turbulent flows, including modal instability, transient growth, and critical-layer phenomena. Further, individual high-gain modes can be combined to generate more complete models for coherent structure and velocity spectra. Preliminary resolvent-based model predictions for canopy flows agree well with existing experiments and simulations.

Children's Representations of the Earth: A Methodological Comparison

ERIC Educational Resources Information Center

Panagiotaki, Georgia; Nobes, Gavin; Banerjee, Robin

2006-01-01

Investigation of children's understanding of the earth can reveal much about the origins and development of scientific knowledge. Vosniadou and Brewer (1992) claim that children construct coherent, theory-like mental models of the earth. However, more recent research has indicated that children's knowledge of the earth is fragmented and…

Coherent diffraction imaging analysis of shape-controlled nanoparticles with focused hard X-ray free-electron laser pulses.

PubMed

Takahashi, Yukio; Suzuki, Akihiro; Zettsu, Nobuyuki; Oroguchi, Tomotaka; Takayama, Yuki; Sekiguchi, Yuki; Kobayashi, Amane; Yamamoto, Masaki; Nakasako, Masayoshi

2013-01-01

We report the first demonstration of the coherent diffraction imaging analysis of nanoparticles using focused hard X-ray free-electron laser pulses, allowing us to analyze the size distribution of particles as well as the electron density projection of individual particles. We measured 1000 single-shot coherent X-ray diffraction patterns of shape-controlled Ag nanocubes and Au/Ag nanoboxes and estimated the edge length from the speckle size of the coherent diffraction patterns. We then reconstructed the two-dimensional electron density projection with sub-10 nm resolution from selected coherent diffraction patterns. This method enables the simultaneous analysis of the size distribution of synthesized nanoparticles and the structures of particles at nanoscale resolution to address correlations between individual structures of components and the statistical properties in heterogeneous systems such as nanoparticles and cells.

Development of pair distribution function analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vondreele, R.; Billinge, S.; Kwei, G.

1996-09-01

This is the final report of a 3-year LDRD project at LANL. It has become more and more evident that structural coherence in the CuO{sub 2} planes of high-{Tc} superconducting materials over some intermediate length scale (nm range) is important to superconductivity. In recent years, the pair distribution function (PDF) analysis of powder diffraction data has been developed for extracting structural information on these length scales. This project sought to expand and develop this technique, use it to analyze neutron powder diffraction data, and apply it to problems. In particular, interest is in the area of high-{Tc} superconductors, although wemore » planned to extend the study to the closely related perovskite ferroelectric materials andother materials where the local structure affects the properties where detailed knowledge of the local and intermediate range structure is important. In addition, we planned to carry out single crystal experiments to look for diffuse scattering. This information augments the information from the PDF.« less

Visualizing nD Point Clouds as Topological Landscape Profiles to Guide Local Data Analysis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Oesterling, Patrick; Heine, Christian; Weber, Gunther H.

2012-05-04

Analyzing high-dimensional point clouds is a classical challenge in visual analytics. Traditional techniques, such as projections or axis-based techniques, suffer from projection artifacts, occlusion, and visual complexity.We propose to split data analysis into two parts to address these shortcomings. First, a structural overview phase abstracts data by its density distribution. This phase performs topological analysis to support accurate and non-overlapping presentation of the high-dimensional cluster structure as a topological landscape profile. Utilizing a landscape metaphor, it presents clusters and their nesting as hills whose height, width, and shape reflect cluster coherence, size, and stability, respectively. A second local analysis phasemore » utilizes this global structural knowledge to select individual clusters or point sets for further, localized data analysis. Focusing on structural entities significantly reduces visual clutter in established geometric visualizations and permits a clearer, more thorough data analysis. In conclusion, this analysis complements the global topological perspective and enables the user to study subspaces or geometric properties, such as shape.« less

Average CsI Neutron Density Distribution from COHERENT Data

NASA Astrophysics Data System (ADS)

Cadeddu, M.; Giunti, C.; Li, Y. F.; Zhang, Y. Y.

2018-02-01

Using the coherent elastic neutrino-nucleus scattering data of the COHERENT experiment, we determine for the first time the average neutron rms radius of Cs 133 and I 127 . We obtain the practically model-independent value Rn=5.5-1.1+0.9 fm using the symmetrized Fermi and Helm form factors. We also point out that the COHERENT data show a 2.3 σ evidence of the nuclear structure suppression of the full coherence.

Retrieving Coherent Receiver Function Images with Dense Arrays

NASA Astrophysics Data System (ADS)

Zhong, M.; Zhan, Z.

2016-12-01

Receiver functions highlight converted phases (e.g., Ps, PpPs, sP) and have been widely used to study seismic interfaces. With a dense array, receiver functions (RFs) at multiple stations form a RF image that can provide more robust/detailed constraints. However, due to noise in data, non-uniqueness of deconvolution, and local structures that cannot be detected across neighboring stations, traditional RF images are often noisy and hard to interpret. Previous attempts to enhance coherence by stacking RFs from multiple events or post-filtering the RF images have not produced satisfactory improvements. Here, we propose a new method to retrieve coherent RF images with dense arrays. We take advantage of the waveform coherency at neighboring stations and invert for a small number of coherent arrivals for their RFs. The new RF images contain only the coherent arrivals required to fit data well. Synthetic tests and preliminary applications on real data demonstrate that the new RF images are easier to interpret and improve our ability to infer Earth structures using receiver functions.

A synchronized particle image velocimetry and infrared thermography technique applied to an acoustic streaming flow

PubMed Central

Sou, In Mei; Layman, Christopher N.; Ray, Chittaranjan

2013-01-01

Subsurface coherent structures and surface temperatures are investigated using simultaneous measurements of particle image velocimetry (PIV) and infrared (IR) thermography. Results for coherent structures from acoustic streaming and associated heating transfer in a rectangular tank with an acoustic horn mounted horizontally at the sidewall are presented. An observed vortex pair develops and propagates in the direction along the centerline of the horn. From the PIV velocity field data, distinct kinematic regions are found with the Lagrangian coherent structure (LCS) method. The implications of this analysis with respect to heat transfer and related sonochemical applications are discussed. PMID:24347810

[INVITED] Coherent perfect absorption of electromagnetic wave in subwavelength structures

NASA Astrophysics Data System (ADS)

Yan, Chao; Pu, Mingbo; Luo, Jun; Huang, Yijia; Li, Xiong; Ma, Xiaoliang; Luo, Xiangang

2018-05-01

Electromagnetic (EM) absorption is a common process by which the EM energy is transformed into other kinds of energy in the absorber, for example heat. Perfect absorption of EM with structures at subwavelength scale is important for many practical applications, such as stealth technology, thermal control and sensing. Coherent perfect absorption arises from the interplay of interference and absorption, which can be interpreted as a time-reversed process of lasing or EM emitting. It provides a promising way for complete absorption in both nanophotonics and electromagnetics. In this review, we discuss basic principles and properties of a coherent perfect absorber (CPA). Various subwavelength structures including thin films, metamaterials and waveguide-based structures to realize CPAs are compared. We also discuss the potential applications of CPAs.

Ultra-high resolution spectral domain optical coherence tomography using supercontinuum light source

NASA Astrophysics Data System (ADS)

Lim, Yiheng; Yatagai, Toyohiko; Otani, Yukitoshi

2016-04-01

An ultra-high resolution spectral domain optical coherence tomography (SD-OCT) was developed using a cost-effective supercontinuum laser. A spectral filter consists of a dispersive prism, a cylindrical lens and a right-angle prism was built to transmit the wavelengths in range 680-940 nm to the OCT system. The SD-OCT has achieved 1.9 μm axial resolution and the sensitivity was estimated to be 91.5 dB. A zero-crossing fringes matching method which maps the wavelengths to the pixel indices of the spectrometer was proposed for the OCT spectral calibration. A double sided foam tape as a static sample and the tip of a middle finger as a biological sample were measured by the OCT. The adhesive and the internal structure of the foam of the tape were successfully visualized in three dimensions. Sweat ducts was clearly observed in the OCT images at very high resolution. To the best of our knowledge, this is the first demonstration of ultra-high resolution visualization of sweat duct by OCT.

Characterization of PET preforms using spectral domain optical coherence tomography

NASA Astrophysics Data System (ADS)

Hosseiny, Hamid; Ferreira, Manuel João.; Martins, Teresa; Carmelo Rosa, Carla

2013-11-01

Polyethylene terephthalate (PET) preforms are massively produced nowadays with the purpose of producing food and beverages packaging and liquid containers. Some varieties of these preforms are produced as multilayer structures, where very thin inner film(s) act as a barrier for nutrients leakage. The knowledge of the thickness of this thin inner layer is important in the production line. The quality control of preforms production requires a fast approach and normally the thickness control is performed by destructive means out of the production line. A spectral domain optical coherence tomography (SD-OCT) method was proposed to examine the thin layers in real time. This paper describes a nondestructive approach and all required signal processing steps to characterize the thin inner layers and also to improve the imaging speed and the signal to noise ratio. The algorithm was developed by using graphics processing unit (GPU) with computer unified device architecture (CUDA). This GPU-accelerated white light interferometry technique nondestructively assesses the samples and has high imaging speed advantage, overcoming the bottlenecks in PET performs quality control.

The Effect of Experimental Geometry and Initial Conditions on the Shape of Coherent Population Trapping Resonances on the Fine Structure Levels of Thallium Atoms

DOE Office of Scientific and Technical Information (OSTI.GOV)

Karagodova, T.Ya.

2005-06-15

Specific features of the coherent population trapping effect are considered in the generalized {lambda} system whose lower levels are the magnetic sublevels of the fine structure levels of the thallium atom. Numerical experiments were performed aimed at examination of the coherent population trapping for the case of nontrivial, but feasible, initial populations of the upper metastable fine structure level. Such populations may be obtained, for example, due to the photodissociation of TlBr molecules. The possibility of reducing the number of resonances of the coherent population trapping in a multilevel system, which may be useful for high-resolution spectroscopy, is demonstrated. Itmore » is shown that the magnitude and shape of the resonances can be controlled by varying the orientation of the polarization vectors of the light field components with respect to each other and to a magnetic field. In addition, studying the shape of the coherent population trapping resonances for the atoms obtained by photodissociation of molecules may provide information about these molecules.« less

Activating gender stereotypes during online spoken language processing: evidence from Visual World Eye Tracking.

PubMed

Pyykkönen, Pirita; Hyönä, Jukka; van Gompel, Roger P G

2010-01-01

This study used the visual world eye-tracking method to investigate activation of general world knowledge related to gender-stereotypical role names in online spoken language comprehension in Finnish. The results showed that listeners activated gender stereotypes elaboratively in story contexts where this information was not needed to build coherence. Furthermore, listeners made additional inferences based on gender stereotypes to revise an already established coherence relation. Both results are consistent with mental models theory (e.g., Garnham, 2001). They are harder to explain by the minimalist account (McKoon & Ratcliff, 1992) which suggests that people limit inferences to those needed to establish coherence in discourse.

Speckle-modulating optical coherence tomography in living mice and humans.

PubMed

Liba, Orly; Lew, Matthew D; SoRelle, Elliott D; Dutta, Rebecca; Sen, Debasish; Moshfeghi, Darius M; Chu, Steven; de la Zerda, Adam

2017-06-20

Optical coherence tomography (OCT) is a powerful biomedical imaging technology that relies on the coherent detection of backscattered light to image tissue morphology in vivo. As a consequence, OCT is susceptible to coherent noise (speckle noise), which imposes significant limitations on its diagnostic capabilities. Here we show speckle-modulating OCT (SM-OCT), a method based purely on light manipulation that virtually eliminates speckle noise originating from a sample. SM-OCT accomplishes this by creating and averaging an unlimited number of scans with uncorrelated speckle patterns without compromising spatial resolution. Using SM-OCT, we reveal small structures in the tissues of living animals, such as the inner stromal structure of a live mouse cornea, the fine structures inside the mouse pinna, and sweat ducts and Meissner's corpuscle in the human fingertip skin-features that are otherwise obscured by speckle noise when using conventional OCT or OCT with current state of the art speckle reduction methods.

Speckle-modulating optical coherence tomography in living mice and humans

PubMed Central

Liba, Orly; Lew, Matthew D.; SoRelle, Elliott D.; Dutta, Rebecca; Sen, Debasish; Moshfeghi, Darius M.; Chu, Steven; de la Zerda, Adam

2017-01-01

Optical coherence tomography (OCT) is a powerful biomedical imaging technology that relies on the coherent detection of backscattered light to image tissue morphology in vivo. As a consequence, OCT is susceptible to coherent noise (speckle noise), which imposes significant limitations on its diagnostic capabilities. Here we show speckle-modulating OCT (SM-OCT), a method based purely on light manipulation that virtually eliminates speckle noise originating from a sample. SM-OCT accomplishes this by creating and averaging an unlimited number of scans with uncorrelated speckle patterns without compromising spatial resolution. Using SM-OCT, we reveal small structures in the tissues of living animals, such as the inner stromal structure of a live mouse cornea, the fine structures inside the mouse pinna, and sweat ducts and Meissner’s corpuscle in the human fingertip skin—features that are otherwise obscured by speckle noise when using conventional OCT or OCT with current state of the art speckle reduction methods. PMID:28632205

Method and apparatus for molecular imaging using x-rays at resonance wavelengths

DOEpatents

Chapline, G.F. Jr.

Holographic x-ray images are produced representing the molecular structure of a microscopic object, such as a living cell, by directing a beam of coherent x-rays upon the object to produce scattering of the x-rays by the object, producing interference on a recording medium between the scattered x-rays from the object and unscattered coherent x-rays and thereby producing holograms on the recording surface, and establishing the wavelength of the coherent x-rays to correspond with a molecular resonance of a constituent of such object and thereby greatly improving the contrast, sensitivity and resolution of the holograms as representations of molecular structures involving such constituent. For example, the coherent x-rays may be adjusted to the molecular resonant absorption line of nitrogen at about 401.3 eV to produce holographic images featuring molecular structures involving nitrogen.

Speckle-modulating optical coherence tomography in living mice and humans

NASA Astrophysics Data System (ADS)

Liba, Orly; Lew, Matthew D.; Sorelle, Elliott D.; Dutta, Rebecca; Sen, Debasish; Moshfeghi, Darius M.; Chu, Steven; de La Zerda, Adam

2017-06-01

Optical coherence tomography (OCT) is a powerful biomedical imaging technology that relies on the coherent detection of backscattered light to image tissue morphology in vivo. As a consequence, OCT is susceptible to coherent noise (speckle noise), which imposes significant limitations on its diagnostic capabilities. Here we show speckle-modulating OCT (SM-OCT), a method based purely on light manipulation that virtually eliminates speckle noise originating from a sample. SM-OCT accomplishes this by creating and averaging an unlimited number of scans with uncorrelated speckle patterns without compromising spatial resolution. Using SM-OCT, we reveal small structures in the tissues of living animals, such as the inner stromal structure of a live mouse cornea, the fine structures inside the mouse pinna, and sweat ducts and Meissner's corpuscle in the human fingertip skin--features that are otherwise obscured by speckle noise when using conventional OCT or OCT with current state of the art speckle reduction methods.

Method and apparatus for molecular imaging using X-rays at resonance wavelengths

DOEpatents

Chapline, Jr., George F.

1985-01-01

Holographic X-ray images are produced representing the molecular structure of a microscopic object, such as a living cell, by directing a beam of coherent X-rays upon the object to produce scattering of the X-rays by the object, producing interference on a recording medium between the scattered X-rays from the object and unscattered coherent X-rays and thereby producing holograms on the recording surface, and establishing the wavelength of the coherent X-rays to correspond with a molecular resonance of a constituent of such object and thereby greatly improving the contrast, sensitivity and resolution of the holograms as representations of molecular structures involving such constituent. For example, the coherent X-rays may be adjusted to the molecular resonant absorption line of nitrogen at about 401.3 eV to produce holographic images featuring molecular structures involving nitrogen.

Models as Relational Categories

NASA Astrophysics Data System (ADS)

Kokkonen, Tommi

2017-11-01

Model-based learning (MBL) has an established position within science education. It has been found to enhance conceptual understanding and provide a way for engaging students in authentic scientific activity. Despite ample research, few studies have examined the cognitive processes regarding learning scientific concepts within MBL. On the other hand, recent research within cognitive science has examined the learning of so-called relational categories. Relational categories are categories whose membership is determined on the basis of the common relational structure. In this theoretical paper, I argue that viewing models as relational categories provides a well-motivated cognitive basis for MBL. I discuss the different roles of models and modeling within MBL (using ready-made models, constructive modeling, and generative modeling) and discern the related cognitive aspects brought forward by the reinterpretation of models as relational categories. I will argue that relational knowledge is vital in learning novel models and in the transfer of learning. Moreover, relational knowledge underlies the coherent, hierarchical knowledge of experts. Lastly, I will examine how the format of external representations may affect the learning of models and the relevant relations. The nature of the learning mechanisms underlying students' mental representations of models is an interesting open question to be examined. Furthermore, the ways in which the expert-like knowledge develops and how to best support it is in need of more research. The discussion and conceptualization of models as relational categories allows discerning students' mental representations of models in terms of evolving relational structures in greater detail than previously done.

Integrating the epistemic and ontological aspects of content knowledge in science teaching and learning

NASA Astrophysics Data System (ADS)

Papadouris, Nicos; Constantinou, Constantinos P.

2017-04-01

Promoting facility with content knowledge is one of the most important objectives of science teaching. Conventionally, the focus for this objective is placed on the substantive side of content knowledge (e.g. science concepts/laws), whereas its epistemic or ontological aspects (e.g. why do we construct concepts?) rarely receive explicit attention. In this article, we develop a theoretical argument for the value of elevating the attention paid to the epistemic/ontological aspects of content knowledge and integrating them with its substantive side. Our argument is structured in two parts. The first unpacks the epistemic/ontological aspects of content knowledge and their role in science. For this, we focus on two specific aspects (i.e. ontological status and epistemic value of science concepts), which we elaborate in the context of two particular content domains, namely magnetism and energy. The second part of the argument highlights the potential of discourse on epistemic/ontological aspects to facilitate learning in science. We delineate how such discourse could (a) promote coherent conceptual understanding, (b) foster a productive epistemological stance towards science learning, and (c) enhance students' appreciation of ideas associated with the nature of science. The article concludes with a discussion of ensuing implications for science education.

On-the-spot lung cancer differential diagnosis by label-free, molecular vibrational imaging and knowledge-based classification

NASA Astrophysics Data System (ADS)

Gao, Liang; Li, Fuhai; Thrall, Michael J.; Yang, Yaliang; Xing, Jiong; Hammoudi, Ahmad A.; Zhao, Hong; Massoud, Yehia; Cagle, Philip T.; Fan, Yubo; Wong, Kelvin K.; Wang, Zhiyong; Wong, Stephen T. C.

2011-09-01

We report the development and application of a knowledge-based coherent anti-Stokes Raman scattering (CARS) microscopy system for label-free imaging, pattern recognition, and classification of cells and tissue structures for differentiating lung cancer from non-neoplastic lung tissues and identifying lung cancer subtypes. A total of 1014 CARS images were acquired from 92 fresh frozen lung tissue samples. The established pathological workup and diagnostic cellular were used as prior knowledge for establishment of a knowledge-based CARS system using a machine learning approach. This system functions to separate normal, non-neoplastic, and subtypes of lung cancer tissues based on extracted quantitative features describing fibrils and cell morphology. The knowledge-based CARS system showed the ability to distinguish lung cancer from normal and non-neoplastic lung tissue with 91% sensitivity and 92% specificity. Small cell carcinomas were distinguished from nonsmall cell carcinomas with 100% sensitivity and specificity. As an adjunct to submitting tissue samples to routine pathology, our novel system recognizes the patterns of fibril and cell morphology, enabling medical practitioners to perform differential diagnosis of lung lesions in mere minutes. The demonstration of the strategy is also a necessary step toward in vivo point-of-care diagnosis of precancerous and cancerous lung lesions with a fiber-based CARS microendoscope.

Time-resolved measurements of coherent structures in the turbulent boundary layer

NASA Astrophysics Data System (ADS)

LeHew, J. A.; Guala, M.; McKeon, B. J.

2013-04-01

Time-resolved particle image velocimetry was used to examine the structure and evolution of swirling coherent structure (SCS), one interpretation of which is a marker for a three-dimensional coherent vortex structure, in wall-parallel planes of a turbulent boundary layer with a large field of view, 4.3 δ × 2.2 δ. Measurements were taken at four different wall-normal locations ranging from y/ δ = 0.08-0.48 at a friction Reynolds number, Re τ = 410. The data set yielded statistically converged results over a larger field of view than typically observed in the literature. The method for identifying and tracking swirling coherent structure is discussed, and the resulting trajectories, convection velocities, and lifespan of these structures are analyzed at each wall-normal location. The ability of a model in which the entirety of an individual SCS travels at a single convection velocity, consistent with the attached eddy hypothesis of Townsend (The structure of turbulent shear flows. Cambridge University Press, Cambridge, 1976), to describe the data is investigated. A methodology for determining whether such structures are "attached" or "detached" from the wall is also proposed and used to measure the lifespan and convection velocity distributions of these different structures. SCS were found to persist for longer periods of time further from the wall, particularly those inferred to be "detached" from the wall, which could be tracked for longer than 5 eddy turnover times.

Influence of coherent mesoscale structures on satellite-based Doppler lidar wind measurements

NASA Technical Reports Server (NTRS)

Emmitt, G. D.

1985-01-01

The influence of coherent mesoscale structures on satellite based Doppler lidar wind measurements was investigated. Range dependent weighting functions and the single shot SNR of scan angle are examined and a space shuttle lidar experiment which used a fixed beam and rotating shuttle is simulated.

Phase Averaged Measurements of the Coherent Structure of a Mach Number 0.6 Jet. M.S. Thesis

NASA Technical Reports Server (NTRS)

Emami, S.

1983-01-01

The existence of a large scale structure in a Mach number 0.6, axisymmetric jet of cold air was proven. In order to further characterize the coherent structure, phase averaged measurements of the axial mass velocity, radial velocity, and the product of the two were made. These measurements yield information about the percent of the total fluctuations contained in the coherent structure. These measured values were compared to the total fluctuation levels for each quantity and the result expressed as a percent of the total fluctuation level contained in the organized structure at a given frequency. These measurements were performed for five frequencies (St=0.16, 0.32, 0.474, 0.95, and 1.26). All of the phase averaged measurements required that the jet be artificially excited.

The harmonic oscillator and nuclear physics

NASA Technical Reports Server (NTRS)

Rowe, D. J.

1993-01-01

The three-dimensional harmonic oscillator plays a central role in nuclear physics. It provides the underlying structure of the independent-particle shell model and gives rise to the dynamical group structures on which models of nuclear collective motion are based. It is shown that the three-dimensional harmonic oscillator features a rich variety of coherent states, including vibrations of the monopole, dipole, and quadrupole types, and rotations of the rigid flow, vortex flow, and irrotational flow types. Nuclear collective states exhibit all of these flows. It is also shown that the coherent state representations, which have their origins in applications to the dynamical groups of the simple harmonic oscillator, can be extended to vector coherent state representations with a much wider range of applicability. As a result, coherent state theory and vector coherent state theory become powerful tools in the application of algebraic methods in physics.

Structure and symmetry in coherent perfect polarization rotation

NASA Astrophysics Data System (ADS)

Crescimanno, Michael; Zhou, Chuanhong; Andrews, James H.; Baker, Michael A.

2015-01-01

Theoretical investigations of different routes to coherent perfect polarization rotation illustrate its phenomenological connection with coherent perfect absorption. Our study of systems with broken parity, layering, combined Faraday rotation and optical activity, or a rotator-loaded optical cavity highlights their similarity and suggests alternate approaches to improving and miniaturizing optical devices.

Scaling the Fractal Plain: Towards a General View of Knowledge Management

ERIC Educational Resources Information Center

Griffiths, David; Evans, Peter

2011-01-01

Purpose: The purpose of the paper is to explore coherence across key disciplines of knowledge management (KM) for a general model as a way to address performance dissatisfaction in the field. Design/methodology/approach: Research employed an evidence-based meta-analysis (287 aspects of literature), triangulated through an exploratory survey (91…

Funds of Knowledge: An Investigation of Coherence within the Literature

ERIC Educational Resources Information Center

Hogg, Linda

2011-01-01

Two decades ago academics based at the University of Arizona brought the anthropological concept of Funds of Knowledge into the educational realm, providing a new conceptual framework to counter deficit theorizing of Latino students and their families. The growing body of literature evidences the belief and hope of academics in the potential of…

The Impact of Management on Knowledge and Patient Care

ERIC Educational Resources Information Center

Iversen, Hans Petter

2011-01-01

How do approaches to management affect knowledge and patient care? In this paper, the establishment and dismantling of an organisational unit for research and development (R&D) in a mental health department of a Norwegian health enterprise are analysed. The characteristics of two adverse treatment ideologies and their coherence with approaches…

The Role of Dialogic Pedagogy in Teaching Grammar

ERIC Educational Resources Information Center

Jones, Pauline; Chen, Honglin

2016-01-01

The inclusion of the Knowledge about Language strand in the recently introduced Australian Curriculum: English (AC:E) is both promising and challenging. For the first time, students across primary and secondary years of schooling are expected to develop "a coherent, dynamic, and evolving body of knowledge about the English language and how it…

The Significance of Practical Training in Linking Theoretical Studies with Practice

ERIC Educational Resources Information Center

Katajavuori, Nina; Lindblom-Ylanne, Sari; Hirvonen, Jouni

2006-01-01

Today's experts must continuously reconstruct their expertise and be able to apply their theoretical knowledge in actual work. The development of expertise is a long process, during which theoretical, practical and metacognitive elements of expert knowledge are integrated into a coherent whole. It is important to foster student's learning and…

Investigating Coherence among Turkish Elementary Science Teachers' Teaching Belief Systems, Pedagogical Content Knowledge and Practice

ERIC Educational Resources Information Center

Bahcivan, Eralp; Cobern, William W.

2016-01-01

This study investigated comprehensive science teaching belief systems and their relation to science teachers' pedagogical content knowledge and teaching practices. Rokeach's (1968) belief system was used as a framework for representing the hierarchy among in-service teachers' teaching beliefs. This study employed a multiple case study design with…

Attention, motivation, and reading coherence failure: a neuropsychological perspective.

PubMed

Wasserman, Theodore

2012-01-01

Reading coherence, defined as the ability to create appropriate, meaningful connections between the elements within a specific text itself and between elements within a text and the reader's prior knowledge, is one of the key processes involved in reading comprehension. This article describes reading coherence within the context of a neuropsychological model combining recent research in motivation, attention, and working memory. Specifically, a unique neuropsychologically identifiable form of reading coherence failure arising from the attentional and motivational deficiencies, based in altered frontoventral striatal reward circuits associated with noradrenaline (NA) circuitry, consistent with the delay-aversion model (dual-pathway model) of Sonuga-Barke ( 2003 ) is postulated. This article provides a model for this subset of reading disorders of which etiology is based on the executive support processes for reading and not in the mechanics of actual reading such as decoding and phonetics.

Increasing readers' comprehension of health education brochures: a qualitative study into how professional writers make texts coherent.

PubMed

Kools, Marieke; Ruiter, Robert A C; van de Wiel, Margaretha W J; Kok, Gerjo

2004-12-01

The aim of this study was to gain insight into the extent to which health education text writers apply writing principles derived from cognitive psychological theory. Seventeen professional text writers of health education materials participated in a qualitative study, consisting of a rewriting task combined with a think-aloud procedure and a semistructured interview. The verbal data were explored carefully in light of seven text coherence principles that have proven effective in cognitive psychological research to increase text comprehension. Findings indicate text writers vary in their ideas and use of coherence principles to make a text comprehensible. It is argued that the health education profession can benefit greatly from knowledge about cognitive text processing and cognitive coherence principles for realizing effective comprehension of written health education messages.

The influence of category coherence on inference about cross-classified entities.

PubMed

Patalano, Andrea L; Wengrovitz, Steven M; Sharpes, Kirsten M

2009-01-01

A critical function of categories is their use in property inference (Heit, 2000). However, one challenge to using categories in inference is that most entities in the world belong to multiple categories (e.g., Fido could be a dog, a pet, a mammal, or a security system). Building on Patalano, Chin-Parker, and Ross (2006), we tested the hypothesis that category coherence (the extent to which category features go together in light of prior knowledge) influences the selection of categories for use in property inference about cross-classified entities. In two experiments, we directly contrasted coherent and incoherent categories, both of which included cross-classified entities as members, and we found that the coherent categories were used more readily as the source of both property transfer and property extension. We conclude that category coherence, which has been found to be a potent influence on strength of inference for singly classified entities (Rehder & Hastie, 2004), is also central to category use in reasoning about novel cross-classified ones.

Timescales of Coherent Dynamics in the Light Harvesting Complex 2 (LH2) of Rhodobacter sphaeroides.

PubMed

Fidler, Andrew F; Singh, Ved P; Long, Phillip D; Dahlberg, Peter D; Engel, Gregory S

2013-05-02

The initial dynamics of energy transfer in the light harvesting complex 2 from Rhodobacter sphaeroides were investigated with polarization controlled two-dimensional spectroscopy. This method allows only the coherent electronic motions to be observed revealing the timescale of dephasing among the excited states. We observe persistent coherence among all states and assign ensemble dephasing rates for the various coherences. A simple model is utilized to connect the spectroscopic transitions to the molecular structure, allowing us to distinguish coherences between the two rings of chromophores and coherences within the rings. We also compare dephasing rates between excited states to dephasing rates between the ground and excited states, revealing that the coherences between excited states dephase on a slower timescale than coherences between the ground and excited states.

Coherent Bragg nanodiffraction at the hard X-ray Nanoprobe beamline.

PubMed

Hruszkewycz, S O; Holt, M V; Maser, J; Murray, C E; Highland, M J; Folkman, C M; Fuoss, P H

2014-03-06

Bragg coherent diffraction with nanofocused hard X-ray beams provides unique opportunities for quantitative in situ studies of crystalline structure in nanoscale regions of complex materials and devices by a variety of diffraction-based techniques. In the case of coherent diffraction imaging, a major experimental challenge in using nanoscale coherent beams is maintaining a constant scattering volume such that coherent fringe visibility is maximized and maintained over the course of an exposure lasting several seconds. Here, we present coherent Bragg diffraction patterns measured from different nanostructured thin films at the Sector 26 Nanoprobe beamline at the Advanced Photon Source and demonstrate that with nanoscale positional control, coherent diffraction patterns can be measured with source-limited fringe visibilities more than 50% suitable for imaging by coherent Bragg ptychography techniques.

Coherent Bragg nanodiffraction at the hard X-ray Nanoprobe beamline

PubMed Central

Hruszkewycz, S. O.; Holt, M. V.; Maser, J.; Murray, C. E.; Highland, M. J.; Folkman, C. M.; Fuoss, P. H.

2014-01-01

Bragg coherent diffraction with nanofocused hard X-ray beams provides unique opportunities for quantitative in situ studies of crystalline structure in nanoscale regions of complex materials and devices by a variety of diffraction-based techniques. In the case of coherent diffraction imaging, a major experimental challenge in using nanoscale coherent beams is maintaining a constant scattering volume such that coherent fringe visibility is maximized and maintained over the course of an exposure lasting several seconds. Here, we present coherent Bragg diffraction patterns measured from different nanostructured thin films at the Sector 26 Nanoprobe beamline at the Advanced Photon Source and demonstrate that with nanoscale positional control, coherent diffraction patterns can be measured with source-limited fringe visibilities more than 50% suitable for imaging by coherent Bragg ptychography techniques. PMID:24470418

Conceptual design of a coherent optical system of modular imaging collectors (COSMIC). [telescope array deployed by space shuttle in 1990's

NASA Technical Reports Server (NTRS)

Nein, M. E.; Davis, B. G.

1982-01-01

The Coherent Optical System of Modular Imaging Collectors (COSMIC) is the design concept for a phase-coherent optical telescope array that may be placed in earth orbit by the Space Shuttle in the 1990s. The initial system module is a minimum redundancy array whose photon collecting area is three times larger than that of the Space Telescope, and possesses a one-dimensional resoution of better than 0.01 arcsec in the visible range. Thermal structural requirements are assessed. Although the coherent beam combination requirements will be met by an active control system, the COSMIC structural/thermal design must meet more stringent performance criteria than even those of the Space Telescope.

DYNECHARM++: a toolkit to simulate coherent interactions of high-energy charged particles in complex structures

NASA Astrophysics Data System (ADS)

Bagli, Enrico; Guidi, Vincenzo

2013-08-01

A toolkit for the simulation of coherent interactions between high-energy charged particles and complex crystal structures, called DYNECHARM++ has been developed. The code has been written in C++ language taking advantage of this object-oriented programing method. The code is capable to evaluating the electrical characteristics of complex atomic structures and to simulate and track the particle trajectory within them. Calculation method of electrical characteristics based on their expansion in Fourier series has been adopted. Two different approaches to simulate the interaction have been adopted, relying on the full integration of particle trajectories under the continuum potential approximation and on the definition of cross-sections of coherent processes. Finally, the code has proved to reproduce experimental results and to simulate interaction of charged particles with complex structures.

The Effect of Topical Structure Analysis Instruction on University Students' Writing Quality

ERIC Educational Resources Information Center

Liangprayoon, Somlak; Chaya, Walaiporn; Thep-ackraphong, Tipa

2013-01-01

Coherence is considered one of the characteristics of effective writing. Topical structure analysis (TSA) has been taught to students as a revision strategy to raise their awareness of importance of textual coherence and helps them clearly understand its concept. This study aimed to investigate the effectiveness of TSA instruction in improving…

In vivo endoscopic Doppler optical coherence tomography imaging of mouse colon

NASA Astrophysics Data System (ADS)

Welge, Weston A.; Barton, Jennifer K.

2016-03-01

Colorectal cancer remains the second deadliest cancer in the United States, despite the high sensitivity and specificity of colonoscopy and sigmoidoscopy. While these standard imaging procedures can accurately detect medium and large polyps, some studies have shown miss rates up to 25% for polyps less than 5 mm in diameter. An imaging modality capable of detecting small lesions could potentially improve patient outcomes. Optical coherence tomography (OCT) has been shown to be a powerful imaging modality for adenoma detection in a mouse model of colorectal cancer. While previous work has focused on analyzing the structural OCT images based on thickening of the mucosa and changes in light attenuation in depth, imaging the microvasculature of the colon may enable earlier detection of polyps. The structure and function of vessels grown to support tumor growth are markedly different from healthy vessels. Doppler OCT is capable of imaging microvessels in vivo. We developed a method of processing raw fringe data from a commercial swept-source OCT system using a lab-built miniature endoscope to extract microvessels. This method can be used to measure vessel count and density and to measure flow velocities. This may improve early detection and aid in the development of new chemopreventive and chemotherapeutic drugs. We present, to the best of our knowledge, the first endoscopic Doppler OCT images of in vivo mouse colon.

Coherent optical transition radiation and self-amplified spontaneous emission generated by chicane-compressed electron beams

NASA Astrophysics Data System (ADS)

Lumpkin, A. H.; Dejus, R. J.; Sereno, N. S.

2009-04-01

Observations of strongly enhanced optical transition radiation (OTR) following significant bunch compression of photoinjector beams by a chicane have been reported during the commissioning of the Linac Coherent Light Source accelerator and recently at the Advanced Photon Source (APS) linac. These localized transverse spatial features involve signal enhancements of nearly a factor of 10 and 100 in the APS case at the 150-MeV and 375-MeV OTR stations, respectively. They are consistent with a coherent process seeded by noise and may be evidence of a longitudinal space charge microbunching instability which leads to coherent OTR emissions. Additionally, we suggest that localized transverse structure in the previous self-amplified spontaneous emission (SASE) free-electron laser (FEL) data at APS in the visible regime as reported at FEL02 may be attributed to such beam structure entering the FEL undulators and inducing the SASE startup at those “prebunched” structures. Separate beam structures 120 microns apart in x and 2.9 nm apart in wavelength were reported. The details of these observations and operational parameters will be presented.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Zhdankin, Vladimir; Boldyrev, Stanislav; Perez, Jean Carlos

We investigate the intermittency of energy dissipation in magnetohydrodynamic (MHD) turbulence by identifying dissipative structures and measuring their characteristic scales. We find that the probability distribution of energy dissipation rates exhibits a power-law tail with an index very close to the critical value of –2.0, which indicates that structures of all intensities contribute equally to energy dissipation. We find that energy dissipation is uniformly spread among coherent structures with lengths and widths in the inertial range. At the same time, these structures have thicknesses deep within the dissipative regime. As the Reynolds number is increased, structures become thinner and moremore » numerous, while the energy dissipation continues to occur mainly in large-scale coherent structures. This implies that in the limit of high Reynolds number, energy dissipation occurs in thin, tightly packed current sheets which nevertheless span a continuum of scales up to the system size, exhibiting features of both coherent structures and nanoflares previously conjectured as a coronal heating mechanism.« less

Imaging of supersonic flow over a double elliptic surface

NASA Astrophysics Data System (ADS)

Zhang, Qing-Hu; Yi, Shi-He; He, Lin; Zhu, Yang-Zhu; Chen, Zhi

2013-11-01

The coherent structures of flow over a double elliptic surface are experimentally investigated in a supersonic low-noise wind tunnel at Mach number 3 using nano-tracer planar laser scattering (NPLS) and particle image velocimetry (PIV) techniques. High spatiotemporal resolution images and velocity fields of both laminar and turbulent inflows over the test model are captured. Based on the time-correlation images, the spatial and temporal evolutionary characteristics of the coherent structures are investigated. The flow structures in the NPLS images are in good agreement with the velocity fluctuation fields by PIV. From statistically significant ensembles, spatial correlation analysis of both cases is performed to quantify the mean size and the orientation of coherent structures. The results indicate that the mean structure is elliptical in shape and the structural angles in the separated region of laminar inflow are slightly smaller than that of turbulent inflow. Moreover, the structural angles of both cases increase with their distance away from the wall.

Coherent structures in wall-bounded turbulence

NASA Astrophysics Data System (ADS)

Jiménez, Javier

2018-05-01

This article discusses the description of wall-bounded turbulence as a deterministic high-dimensional dynamical system of interacting coherent structures, defined as eddies with enough internal dynamics to behave relatively autonomously from any remaining incoherent part of the flow. The guiding principle is that randomness is not a property, but a methodological choice of what to ignore in the flow, and that a complete understanding of turbulence, including the possibility of control, requires that it be kept to a minimum. After briefly reviewing the underlying low-order statistics of flows at moderate Reynolds numbers, the article examines what two-point statistics imply for the decomposition of the flow into individual eddies. Intense eddies are examined next, including their temporal evolution, and shown to satisfy many of the properties required for coherence. In particular, it is shown that coherent structures larger than the Corrsin scale are a natural consequence of the shear. In wall-bounded turbulence, they can be classified into coherent dispersive waves and transient bursts. The former are found in the viscous layer near the wall and as very-large structures spanning the boundary layer thickness. Although they are shear-driven, these waves have enough internal structure to maintain a uniform advection velocity. Conversely, bursts exist at all scales, are characteristic of the logarithmic layer, and interact almost linearly with the shear. While the waves require a wall to determine their length scale, the bursts are essentially independent from it. The article concludes with a brief review of our present theoretical understanding of turbulent structures, and with a list of open problems and future perspectives.

Coherent fluorescence emission by using hybrid photonic–plasmonic crystals

PubMed Central

Shi, Lei; Yuan, Xiaowen; Zhang, Yafeng; Hakala, Tommi; Yin, Shaoyu; Han, Dezhuan; Zhu, Xiaolong; Zhang, Bo; Liu, Xiaohan; Törmä, Päivi; Lu, Wei; Zi, Jian

2014-01-01

The spatial and temporal coherence of the fluorescence emission controlled by a quasi-two-dimensional hybrid photonic–plasmonic crystal structure covered with a thin fluorescent-molecular-doped dielectric film is investigated experimentally. A simple theoretical model to describe how a confined quasi-two-dimensional optical mode may induce coherent fluorescence emission is also presented. Concerning the spatial coherence, it is experimentally observed that the coherence area in the plane of the light source is in excess of 49 μm2, which results in enhanced directional fluorescence emission. Concerning temporal coherence, the obtained coherence time is 4 times longer than that of the normal fluorescence emission in vacuum. Moreover, a Young's double-slit interference experiment is performed to directly confirm the spatially coherent emission. This smoking gun proof of spatial coherence is reported here for the first time for the optical-mode-modified emission. PMID:25793015

Revisiting the Al/Al₂O₃ interface: coherent interfaces and misfit accommodation.

PubMed

Pilania, Ghanshyam; Thijsse, Barend J; Hoagland, Richard G; Lazić, Ivan; Valone, Steven M; Liu, Xiang-Yang

2014-03-27

We study the coherent and semi-coherent Al/α-Al2O3 interfaces using molecular dynamics simulations with a mixed, metallic-ionic atomistic model. For the coherent interfaces, both Al-terminated and O-terminated nonstoichiometric interfaces have been studied and their relative stability has been established. To understand the misfit accommodation at the semi-coherent interface, a 1-dimensional (1D) misfit dislocation model and a 2-dimensional (2D) dislocation network model have been studied. For the latter case, our analysis reveals an interface dislocation structure with a network of three sets of parallel dislocations, each with pure-edge character, giving rise to a pattern of coherent and stacking-fault-like regions at the interface. Structural relaxation at elevated temperatures leads to a further change of the dislocation pattern, which can be understood in terms of a competition between the stacking fault energy and the dislocation interaction energy at the interface. Our results are expected to serve as an input for the subsequent dislocation dynamics models to understand and predict the macroscopic mechanical behavior of Al/α-Al2O3 composite heterostructures.

Quantum coherence generating power, maximally abelian subalgebras, and Grassmannian geometry

NASA Astrophysics Data System (ADS)

Zanardi, Paolo; Campos Venuti, Lorenzo

2018-01-01

We establish a direct connection between the power of a unitary map in d-dimensions (d < ∞) to generate quantum coherence and the geometry of the set Md of maximally abelian subalgebras (of the quantum system full operator algebra). This set can be seen as a topologically non-trivial subset of the Grassmannian over linear operators. The natural distance over the Grassmannian induces a metric structure on Md, which quantifies the lack of commutativity between the pairs of subalgebras. Given a maximally abelian subalgebra, one can define, on physical grounds, an associated measure of quantum coherence. We show that the average quantum coherence generated by a unitary map acting on a uniform ensemble of quantum states in the algebra (the so-called coherence generating power of the map) is proportional to the distance between a pair of maximally abelian subalgebras in Md connected by the unitary transformation itself. By embedding the Grassmannian into a projective space, one can pull-back the standard Fubini-Study metric on Md and define in this way novel geometrical measures of quantum coherence generating power. We also briefly discuss the associated differential metric structures.

Coherent structure diffusivity in the edge region of Reversed Field Pinch experiments

NASA Astrophysics Data System (ADS)

Spolaore, M.; Antoni, V.; Spada, E.; Bergsåker, H.; Cavazzana, R.; Drake, J. R.; Martines, E.; Regnoli, G.; Serianni, G.; Vianello, N.

2005-01-01

Coherent structures emerging from the background turbulence have been detected by electrostatic measurements in the edge region of two Reversed Field Pinch experiments, RFX (Padua) and Extrap-T2R (Stockholm). Measurements have been performed by arrays of Langmuir probes which allowed simultaneous measurements of temperature, potential and density to be carried out. These structures have been interpreted as a dynamic balance of dipolar and monopolar vortices, whose relative population are found to depend on the local mean E × B flow shear. The contribution to the anomalous transport of these structures has been investigated and it has been found that the corresponding diffusion coeffcient accounts up to 50% of the total diffusivity. The experimental findings indicate that the diffusion coeffcient associated to the coherent structures depends on the relative population of the two types of vortices and is minimum when the two populations are equal. An interpretative model is proposed to explain this feature.

Three-dimensional localized coherent structures of surface turbulence: Model validation with experiments and further computations.

PubMed

Demekhin, E A; Kalaidin, E N; Kalliadasis, S; Vlaskin, S Yu

2010-09-01

We validate experimentally the Kapitsa-Shkadov model utilized in the theoretical studies by Demekhin [Phys. Fluids 19, 114103 (2007)10.1063/1.2793148; Phys. Fluids 19, 114104 (2007)]10.1063/1.2793149 of surface turbulence on a thin liquid film flowing down a vertical planar wall. For water at 15° , surface turbulence typically occurs at an inlet Reynolds number of ≃40 . Of particular interest is to assess experimentally the predictions of the model for three-dimensional nonlinear localized coherent structures, which represent elementary processes of surface turbulence. For this purpose we devise simple experiments to investigate the instabilities and transitions leading to such structures. Our experimental results are in good agreement with the theoretical predictions of the model. We also perform time-dependent computations for the formation of coherent structures and their interaction with localized structures of smaller amplitude on the surface of the film.

Coherent Structures and Spectral Energy Transfer in Turbulent Plasma: A Space-Filter Approach.

PubMed

Camporeale, E; Sorriso-Valvo, L; Califano, F; Retinò, A

2018-03-23

Plasma turbulence at scales of the order of the ion inertial length is mediated by several mechanisms, including linear wave damping, magnetic reconnection, the formation and dissipation of thin current sheets, and stochastic heating. It is now understood that the presence of localized coherent structures enhances the dissipation channels and the kinetic features of the plasma. However, no formal way of quantifying the relationship between scale-to-scale energy transfer and the presence of spatial structures has been presented so far. In the Letter we quantify such a relationship analyzing the results of a two-dimensional high-resolution Hall magnetohydrodynamic simulation. In particular, we employ the technique of space filtering to derive a spectral energy flux term which defines, in any point of the computational domain, the signed flux of spectral energy across a given wave number. The characterization of coherent structures is performed by means of a traditional two-dimensional wavelet transformation. By studying the correlation between the spectral energy flux and the wavelet amplitude, we demonstrate the strong relationship between scale-to-scale transfer and coherent structures. Furthermore, by conditioning one quantity with respect to the other, we are able for the first time to quantify the inhomogeneity of the turbulence cascade induced by topological structures in the magnetic field. Taking into account the low space-filling factor of coherent structures (i.e., they cover a small portion of space), it emerges that 80% of the spectral energy transfer (both in the direct and inverse cascade directions) is localized in about 50% of space, and 50% of the energy transfer is localized in only 25% of space.

Coherent Structures and Spectral Energy Transfer in Turbulent Plasma: A Space-Filter Approach

NASA Astrophysics Data System (ADS)

Camporeale, E.; Sorriso-Valvo, L.; Califano, F.; Retinò, A.

2018-03-01

Plasma turbulence at scales of the order of the ion inertial length is mediated by several mechanisms, including linear wave damping, magnetic reconnection, the formation and dissipation of thin current sheets, and stochastic heating. It is now understood that the presence of localized coherent structures enhances the dissipation channels and the kinetic features of the plasma. However, no formal way of quantifying the relationship between scale-to-scale energy transfer and the presence of spatial structures has been presented so far. In the Letter we quantify such a relationship analyzing the results of a two-dimensional high-resolution Hall magnetohydrodynamic simulation. In particular, we employ the technique of space filtering to derive a spectral energy flux term which defines, in any point of the computational domain, the signed flux of spectral energy across a given wave number. The characterization of coherent structures is performed by means of a traditional two-dimensional wavelet transformation. By studying the correlation between the spectral energy flux and the wavelet amplitude, we demonstrate the strong relationship between scale-to-scale transfer and coherent structures. Furthermore, by conditioning one quantity with respect to the other, we are able for the first time to quantify the inhomogeneity of the turbulence cascade induced by topological structures in the magnetic field. Taking into account the low space-filling factor of coherent structures (i.e., they cover a small portion of space), it emerges that 80% of the spectral energy transfer (both in the direct and inverse cascade directions) is localized in about 50% of space, and 50% of the energy transfer is localized in only 25% of space.

Stability and Interaction of Coherent Structure in Supersonic Reactive Wakes

NASA Technical Reports Server (NTRS)

Menon, Suresh

1983-01-01

A theoretical formulation and analysis is presented for a study of the stability and interaction of coherent structure in reacting free shear layers. The physical problem under investigation is a premixed hydrogen-oxygen reacting shear layer in the wake of a thin flat plate. The coherent structure is modeled as a periodic disturbance and its stability is determined by the application of linearized hydrodynamic stability theory which results in a generalized eigenvalue problem for reactive flows. Detailed stability analysis of the reactive wake for neutral, symmetrical and antisymmetrical disturbance is presented. Reactive stability criteria is shown to be quite different from classical non-reactive stability. The interaction between the mean flow, coherent structure and fine-scale turbulence is theoretically formulated using the von-Kaman integral technique. Both time-averaging and conditional phase averaging are necessary to separate the three types of motion. The resulting integro-differential equations can then be solved subject to initial conditions with appropriate shape functions. In the laminar flow transition region of interest, the spatial interaction between the mean motion and coherent structure is calculated for both non-reactive and reactive conditions and compared with experimental data wherever available. The fine-scale turbulent motion determined by the application of integral analysis to the fluctuation equations. Since at present this turbulence model is still untested, turbulence is modeled in the interaction problem by a simple algebraic eddy viscosity model. The applicability of the integral turbulence model formulated here is studied parametrically by integrating these equations for the simple case of self-similar mean motion with assumed shape functions. The effect of the motion of the coherent structure is studied and very good agreement is obtained with previous experimental and theoretical works for non-reactive flow. For the reactive case, lack of experimental data made direct comparison difficult. It was determined that the growth rate of the disturbance amplitude is lower for reactive case. The results indicate that the reactive flow stability is in qualitative agreement with experimental observation.

Coherent diffraction surface imaging in reflection geometry.

PubMed

Marathe, Shashidhara; Kim, S S; Kim, S N; Kim, Chan; Kang, H C; Nickles, P V; Noh, D Y

2010-03-29

We present a reflection based coherent diffraction imaging method which can be used to reconstruct a non periodic surface image from a diffraction amplitude measured in reflection geometry. Using a He-Ne laser, we demonstrated that a surface image can be reconstructed solely from the reflected intensity from a surface without relying on any prior knowledge of the sample object or the object support. The reconstructed phase image of the exit wave is particularly interesting since it can be used to obtain quantitative information of the surface depth profile or the phase change during the reflection process. We believe that this work will broaden the application areas of coherent diffraction imaging techniques using light sources with limited penetration depth.

Low-dimensional representation of near-wall dynamics in shear flows, with implications to wall-models.

PubMed

Schmid, P J; Sayadi, T

2017-03-13

The dynamics of coherent structures near the wall of a turbulent boundary layer is investigated with the aim of a low-dimensional representation of its essential features. Based on a triple decomposition into mean, coherent and incoherent motion and a dynamic mode decomposition to recover statistical information about the incoherent part of the flow field, a driven linear system coupling first- and second-order moments of the coherent structures is derived and analysed. The transfer function for this system, evaluated for a wall-parallel plane, confirms a strong bias towards streamwise elongated structures, and is proposed as an 'impedance' boundary condition which replaces the bulk of the transport between the coherent velocity field and the coherent Reynolds stresses, thus acting as a wall model for large-eddy simulations (LES). It is interesting to note that the boundary condition is non-local in space and time. The extracted model is capable of reproducing the principal Reynolds stress components for the pretransitional, transitional and fully turbulent boundary layer.This article is part of the themed issue 'Toward the development of high-fidelity models of wall turbulence at large Reynolds number'. © 2017 The Author(s).

Go With the Flow, on Jupiter and Snow. Coherence from Model-Free Video Data Without Trajectories

NASA Astrophysics Data System (ADS)

AlMomani, Abd AlRahman R.; Bollt, Erik

2018-06-01

Viewing a data set such as the clouds of Jupiter, coherence is readily apparent to human observers, especially the Great Red Spot, but also other great storms and persistent structures. There are now many different definitions and perspectives mathematically describing coherent structures, but we will take an image processing perspective here. We describe an image processing perspective inference of coherent sets from a fluidic system directly from image data, without attempting to first model underlying flow fields, related to a concept in image processing called motion tracking. In contrast to standard spectral methods for image processing which are generally related to a symmetric affinity matrix, leading to standard spectral graph theory, we need a not symmetric affinity which arises naturally from the underlying arrow of time. We develop an anisotropic, directed diffusion operator corresponding to flow on a directed graph, from a directed affinity matrix developed with coherence in mind, and corresponding spectral graph theory from the graph Laplacian. Our methodology is not offered as more accurate than other traditional methods of finding coherent sets, but rather our approach works with alternative kinds of data sets, in the absence of vector field. Our examples will include partitioning the weather and cloud structures of Jupiter, and a local to Potsdam, NY, lake effect snow event on Earth, as well as the benchmark test double-gyre system.

Evidence of Large Fluctuations of Stock Return and Financial Crises from Turkey: Using Wavelet Coherency and Varma Modeling to Forecast Stock Return

NASA Astrophysics Data System (ADS)

Oygur, Tunc; Unal, Gazanfer

Shocks, jumps, booms and busts are typical large fluctuation markers which appear in crisis. Models and leading indicators vary according to crisis type in spite of the fact that there are a lot of different models and leading indicators in literature to determine structure of crisis. In this paper, we investigate structure of dynamic correlation of stock return, interest rate, exchange rate and trade balance differences in crisis periods in Turkey over the period between October 1990 and March 2015 by applying wavelet coherency methodologies to determine nature of crises. The time period includes the Turkeys currency and banking crises; US sub-prime mortgage crisis and the European sovereign debt crisis occurred in 1994, 2001, 2008 and 2009, respectively. Empirical results showed that stock return, interest rate, exchange rate and trade balance differences are significantly linked during the financial crises in Turkey. The cross wavelet power, the wavelet coherency, the multiple wavelet coherency and the quadruple wavelet coherency methodologies have been used to examine structure of dynamic correlation. Moreover, in consequence of quadruple and multiple wavelet coherence, strongly correlated large scales indicate linear behavior and, hence VARMA (vector autoregressive moving average) gives better fitting and forecasting performance. In addition, increasing the dimensions of the model for strongly correlated scales leads to more accurate results compared to scalar counterparts.

DOE Office of Scientific and Technical Information (OSTI.GOV)

Shao, Shuai; Wang, Jian

In this work, using the Cu–Ni (111) semi-coherent interface as a model system, we combine atomistic simulations and defect theory to reveal the relaxation mechanisms, structure, and properties of semi-coherent interfaces. By calculating the generalized stacking fault energy (GSFE) profile of the interface, two stable structures and a high-energy structure are located. During the relaxation, the regions that possess the stable structures expand and develop into coherent regions; the regions with high-energy structure shrink into the intersection of misfit dislocations (nodes). This process reduces the interface excess potential energy but increases the core energy of the misfit dislocations and nodes.more » The core width is dependent on the GSFE of the interface. The high-energy structure relaxes by relative rotation and dilatation between the crystals. The relative rotation is responsible for the spiral pattern at nodes. The relative dilatation is responsible for the creation of free volume at nodes, which facilitates the nodes’ structural transformation. Several node structures have been observed and analyzed. In conclusion, the various structures have significant impact on the plastic deformation in terms of lattice dislocation nucleation, as well as the point defect formation energies.« less

Investigation of a broadband coherent perfect absorber in a multi-layer structure by using the transfer matrix method

NASA Astrophysics Data System (ADS)

Na, Jihoon; Noh, Heeso

2018-01-01

We investigated a multi-layer structure for a broadband coherent perfect absorber (CPA). The transfer matrix method (TMM) is useful for analyzing the optical properties of structures and optimizing multi-layer structures. The broadband CPA strongly depends on the phase of the light traveling in one direction and the light reflected within the structure. The TMM simulation shows that the absorption bandwidth is increased by 95% in a multi-layer CPA compared to that in a single-layer CPA.

The relationship between free-stream coherent structures and near-wall streaks at high Reynolds numbers

PubMed Central

Deguchi, K.; Hall, P.

2017-01-01

The present work is based on our recent discovery of a new class of exact coherent structures generated near the edge of quite general boundary layer flows. The structures are referred to as free-stream coherent structures and were found using a large Reynolds number asymptotic approach to describe equilibrium solutions of the Navier–Stokes equations. In this paper, first we present results for a new family of free-stream coherent structures existing at relatively large wavenumbers. The new results are consistent with our earlier theoretical result that such structures can generate larger amplitude wall streaks if and only if the local spanwise wavenumber is sufficiently small. In a Blasius boundary layer, the local wavenumber increases in the streamwise direction so the wall streaks can typically exist only over a finite interval. However, here it is shown that they can interact with wall curvature to produce exponentially growing Görtler vortices through the receptivity process by a novel nonparallel mechanism. The theoretical predictions found are confirmed by a hybrid numerical approach. In contrast with previous receptivity investigations, it is shown that the amplitude of the induced vortex is larger than the structures in the free-stream which generate it. This article is part of the themed issue ‘Toward the development of high-fidelity models of wall turbulence at large Reynolds number’. PMID:28167574

The relationship between free-stream coherent structures and near-wall streaks at high Reynolds numbers.

PubMed

Deguchi, K; Hall, P

2017-03-13

The present work is based on our recent discovery of a new class of exact coherent structures generated near the edge of quite general boundary layer flows. The structures are referred to as free-stream coherent structures and were found using a large Reynolds number asymptotic approach to describe equilibrium solutions of the Navier-Stokes equations. In this paper, first we present results for a new family of free-stream coherent structures existing at relatively large wavenumbers. The new results are consistent with our earlier theoretical result that such structures can generate larger amplitude wall streaks if and only if the local spanwise wavenumber is sufficiently small. In a Blasius boundary layer, the local wavenumber increases in the streamwise direction so the wall streaks can typically exist only over a finite interval. However, here it is shown that they can interact with wall curvature to produce exponentially growing Görtler vortices through the receptivity process by a novel nonparallel mechanism. The theoretical predictions found are confirmed by a hybrid numerical approach. In contrast with previous receptivity investigations, it is shown that the amplitude of the induced vortex is larger than the structures in the free-stream which generate it.This article is part of the themed issue 'Toward the development of high-fidelity models of wall turbulence at large Reynolds number'. © 2017 The Author(s).

Science, Religion, and the Quest for Knowledge and Truth: An Islamic Perspective

ERIC Educational Resources Information Center

Guessoum, Nidhal

2010-01-01

This article consists of two parts. The first one is to a large extent a commentary on John R. Staver's "Skepticism, truth as coherence, and constructivist epistemology: grounds for resolving the discord between science and religion?" The second part is a related overview of Islam's philosophy of knowledge and, to a certain degree, science. In…

Zombies, Cyborgs, and other Labor Organizers: An Introduction to Representations of Adult Learning Theories and HRD in Popular Culture

ERIC Educational Resources Information Center

Wright, Robin Redmon

2013-01-01

Too often, educators, researchers, and practitioners in the fields of adult education and human resource development rely on traditional curricular materials and an academic body of knowledge for teaching, evaluating, and training adults. This assumes a coherent body of prior knowledge, assumptions, worldviews, and experiences in their students…

Developing Number Knowledge: Assessment, Teaching and Intervention with 7-11 Year Olds. Math Recovery

ERIC Educational Resources Information Center

Wright, Robert J.; Ellemor-Collins, David; Tabor, Pamela D.

2011-01-01

This fourth book in the Mathematics Recovery series equips teachers with detailed pedagogical knowledge and resources for teaching number to 7 to 11-year olds. Drawing on extensive programs of research, curriculum development, and teacher development, the book offers a coherent, up-to-date approach emphasizing computational fluency and the…

Undergraduate Students' Ability to Revise Text Effectively: Relationships with Topic Knowledge and Working Memory

ERIC Educational Resources Information Center

Adams, Anne-Marie; Simmons, Fiona; Willis, Catherine; Pawling, Ralph

2010-01-01

In order to communicate understanding, students are often required to produce texts which present an explicit, coherent argument. This study examined the extent to which individual differences in undergraduates' topic knowledge and working memory skills were related to their ability to revise texts to better fulfil these goals. Forty-seven…

Single-shot observation of optical rogue waves in integrable turbulence using time microscopy

PubMed Central

Suret, Pierre; Koussaifi, Rebecca El; Tikan, Alexey; Evain, Clément; Randoux, Stéphane; Szwaj, Christophe; Bielawski, Serge

2016-01-01

Optical fibres are favourable tabletop laboratories to investigate both coherent and incoherent nonlinear waves. In particular, exact solutions of the one-dimensional nonlinear Schrödinger equation such as fundamental solitons or solitons on finite background can be generated by launching periodic, specifically designed coherent waves in optical fibres. It is an open fundamental question to know whether these coherent structures can emerge from the nonlinear propagation of random waves. However the typical sub-picosecond timescale prevented—up to now—time-resolved observations of the awaited dynamics. Here, we report temporal ‘snapshots' of random light using a specially designed ‘time-microscope'. Ultrafast structures having peak powers much larger than the average optical power are generated from the propagation of partially coherent waves in optical fibre and are recorded with 250 femtoseconds resolution. Our experiment demonstrates the central role played by ‘breather-like' structures such as the Peregrine soliton in the emergence of heavy-tailed statistics in integrable turbulence. PMID:27713416

Explaining TeV cosmic-ray anisotropies with non-diffusive cosmic-ray propagation

DOE PAGES

Harding, James Patrick; Fryer, Chris Lee; Mendel, Susan Marie

2016-05-11

Constraining the behavior of cosmic ray data observed at Earth requires a precise understanding of how the cosmic rays propagate in the interstellar medium. The interstellar medium is not homogeneous; although turbulent magnetic fields dominate over large scales, small coherent regions of magnetic field exist on scales relevant to particle propagation in the nearby Galaxy. Guided propagation through a coherent field is significantly different from random particle diffusion and could be the explanation of spatial anisotropies in the observed cosmic rays. We present a Monte Carlo code to propagate cosmic particle through realistic magnetic field structures. We discuss the detailsmore » of the model as well as some preliminary studies which indicate that coherent magnetic structures are important effects in local cosmic-ray propagation, increasing the flux of cosmic rays by over two orders of magnitude at anisotropic locations on the sky. Furthermore, the features induced by coherent magnetic structure could be the cause of the observed TeV cosmic-ray anisotropy.« less

EXPLAINING TEV COSMIC-RAY ANISOTROPIES WITH NON-DIFFUSIVE COSMIC-RAY PROPAGATION

DOE Office of Scientific and Technical Information (OSTI.GOV)

Harding, J. Patrick; Fryer, Chris L.; Mendel, Susan, E-mail: jpharding@lanl.gov, E-mail: fryer@lanl.gov, E-mail: smendel@lanl.gov

2016-05-10

Constraining the behavior of cosmic ray data observed at Earth requires a precise understanding of how the cosmic rays propagate in the interstellar medium. The interstellar medium is not homogeneous; although turbulent magnetic fields dominate over large scales, small coherent regions of magnetic field exist on scales relevant to particle propagation in the nearby Galaxy. Guided propagation through a coherent field is significantly different from random particle diffusion and could be the explanation of spatial anisotropies in the observed cosmic rays. We present a Monte Carlo code to propagate cosmic particle through realistic magnetic field structures. We discuss the detailsmore » of the model as well as some preliminary studies which indicate that coherent magnetic structures are important effects in local cosmic-ray propagation, increasing the flux of cosmic rays by over two orders of magnitude at anisotropic locations on the sky. The features induced by coherent magnetic structure could be the cause of the observed TeV cosmic-ray anisotropy.« less

Quantum imaging with incoherently scattered light from a free-electron laser

NASA Astrophysics Data System (ADS)

Schneider, Raimund; Mehringer, Thomas; Mercurio, Giuseppe; Wenthaus, Lukas; Classen, Anton; Brenner, Günter; Gorobtsov, Oleg; Benz, Adrian; Bhatti, Daniel; Bocklage, Lars; Fischer, Birgit; Lazarev, Sergey; Obukhov, Yuri; Schlage, Kai; Skopintsev, Petr; Wagner, Jochen; Waldmann, Felix; Willing, Svenja; Zaluzhnyy, Ivan; Wurth, Wilfried; Vartanyants, Ivan A.; Röhlsberger, Ralf; von Zanthier, Joachim

2018-02-01

The advent of accelerator-driven free-electron lasers (FEL) has opened new avenues for high-resolution structure determination via diffraction methods that go far beyond conventional X-ray crystallography methods. These techniques rely on coherent scattering processes that require the maintenance of first-order coherence of the radiation field throughout the imaging procedure. Here we show that higher-order degrees of coherence, displayed in the intensity correlations of incoherently scattered X-rays from an FEL, can be used to image two-dimensional objects with a spatial resolution close to or even below the Abbe limit. This constitutes a new approach towards structure determination based on incoherent processes, including fluorescence emission or wavefront distortions, generally considered detrimental for imaging applications. Our method is an extension of the landmark intensity correlation measurements of Hanbury Brown and Twiss to higher than second order, paving the way towards determination of structure and dynamics of matter in regimes where coherent imaging methods have intrinsic limitations.

Towards clarification of convergent concepts: sense of coherence, will to meaning, locus of control, learned helplessness and hardiness.

PubMed

Sullivan, G C

1993-11-01

The multidisciplinary field of stress and stress-related health outcomes has generated theoretical and practical knowledge which is of interest to nurses. Theoretical developments which have assumed a prominent role in the study of stress, health and coping include the identification of various 'stress buffers' several of which bear a strong conceptual resemblance to one another. Antonovsky has developed a Salutogenic Model of stress and resistance, which is presented in this paper. The model's central concept, the sense of coherence, is described and analysed. The sense of coherence, with its three components (meaningfulness, comprehensibility and manageability), is then compared and contrasted with similar concepts. The convergent theoretical notions which are distinguished from Antonovsky's coherence are: will to meaning, locus of control, learned helplessness and hardiness. It is hoped that this analysis will provide greater conceptual clarity for nurses who study and use these concepts in education, practice or research.

Phase-and-amplitude recovery from a single phase-contrast image using partially spatially coherent x-ray radiation

NASA Astrophysics Data System (ADS)

Beltran, Mario A.; Paganin, David M.; Pelliccia, Daniele

2018-05-01

A simple method of phase-and-amplitude extraction is derived that corrects for image blurring induced by partially spatially coherent incident illumination using only a single intensity image as input. The method is based on Fresnel diffraction theory for the case of high Fresnel number, merged with the space-frequency description formalism used to quantify partially coherent fields and assumes the object under study is composed of a single-material. A priori knowledge of the object’s complex refractive index and information obtained by characterizing the spatial coherence of the source is required. The algorithm was applied to propagation-based phase-contrast data measured with a laboratory-based micro-focus x-ray source. The blurring due to the finite spatial extent of the source is embedded within the algorithm as a simple correction term to the so-called Paganin algorithm and is also numerically stable in the presence of noise.

Multiple defocused coherent diffraction imaging: method for simultaneously reconstructing objects and probe using X-ray free-electron lasers.

PubMed

Hirose, Makoto; Shimomura, Kei; Suzuki, Akihiro; Burdet, Nicolas; Takahashi, Yukio

2016-05-30

The sample size must be less than the diffraction-limited focal spot size of the incident beam in single-shot coherent X-ray diffraction imaging (CXDI) based on a diffract-before-destruction scheme using X-ray free electron lasers (XFELs). This is currently a major limitation preventing its wider applications. We here propose multiple defocused CXDI, in which isolated objects are sequentially illuminated with a divergent beam larger than the objects and the coherent diffraction pattern of each object is recorded. This method can simultaneously reconstruct both objects and a probe from the coherent X-ray diffraction patterns without any a priori knowledge. We performed a computer simulation of the prposed method and then successfully demonstrated it in a proof-of-principle experiment at SPring-8. The prposed method allows us to not only observe broad samples but also characterize focused XFEL beams.

Adaptive receiver structures for asynchronous CDMA systems

NASA Astrophysics Data System (ADS)

Rapajic, Predrag B.; Vucetic, Branka S.

1994-05-01

Adaptive linear and decision feedback receiver structures for coherent demodulation in asynchronous code division multiple access (CDMA) systems are considered. It is assumed that the adaptive receiver has no knowledge of the signature waveforms and timing of other users. The receiver is trained by a known training sequence prior to data transmission and continuously adjusted by an adaptive algorithm during data transmission. The proposed linear receiver is as simple as a standard single-user detector receiver consisting of a matched filter with constant coefficients, but achieves essential advantages with respect to timing recovery, multiple access interference elimination, near/far effect, narrowband and frequency-selective fading interference suppression, and user privacy. An adaptive centralized decision feedback receiver has the same advantages of the linear receiver but, in addition, achieves a further improvement in multiple access interference cancellation at the expense of higher complexity. The proposed receiver structures are tested by simulation over a channel with multipath propagation, multiple access interference, narrowband interference, and additive white Gaussian noise.

Shock modon: a new type of coherent structure in rotating shallow water.

PubMed

Lahaye, Noé; Zeitlin, Vladimir

2012-01-27

We show that a new type of coherent structure, a shock modon, exists in a rotating shallow water model at large Rossby numbers. It is a combination of an asymmetric vortex dipole with a stationary hydraulic jump. The structure is long living, despite the energy dissipation by the hydraulic jump, and moving along a circular path. Collisions of shock modons can be elastic, or lead to formation of shock tripoles.

Fluid transport and coherent structures of translating and flapping wings.

PubMed

Eldredge, Jeff D; Chong, Kwitae

2010-03-01

The Lagrangian coherent structures (LCSs) of simple wing cross sections in various low Reynolds number motions are extracted from high-fidelity numerical simulation data and examined in detail. The entrainment process in the wake of a translating ellipse is revealed by studying the relationship between attracting structures in the wake and upstream repelling structures, with the help of blocks of tracer particles. It is shown that a series of slender lobes in the repelling LCS project upstream from the front of the ellipse and "pull" fluid into the wake. Each lobe is paired with a corresponding wake vortex, into which the constituent fluid particles are folded. Flexible and rigid foils in flapping motion are studied, and the resulting differences in coherent structures are used to elucidate their differences in force generation. The clarity with which these flow structures are revealed, compared to the vorticity or velocity fields, provides new insight into the vortex shedding mechanisms that play an important role in unsteady aerodynamics.

Solitary waves and nonlinear dynamic coherent structures in magnetic metamaterials

NASA Astrophysics Data System (ADS)

Tankeyev, A. P.; Smagin, V. V.; Borich, M. A.; Zhuravlev, A. S.

2009-03-01

Within the framework of the extended nonlinear Schrödinger equation (ENSE), two types of nonlinear states of magnetization in a ferromagnet-dielectric-metal metamagnetic structure have been obtained and investigated. These states have an internal structure; e.g., a periodic sequence of compound solitons is formed by kink-antikink pairs (shock waves), and coherent periodic breather structures are formed by “bright” quasi-solitons. Conditions have been found under which the envelope of these states is described by a modified Korteweg-de Vries (mKdV) equation. It is shown that the compound solitons are described by an mKdV equation with repulsion, and the breather structures, by an mKdV equation with attraction. It is shown also that the characteristic properties of the solutions are determined by the sign of the group-velocity dispersion rather than by the sign of the group velocity itself. The results obtained can be used for searching new nonlinear dynamic coherent structures, e.g., compound solitons and breathers in high-dispersion magnetic metamaterials.

A joint estimation detection of Glaucoma progression in 3D spectral domain optical coherence tomography optic nerve head images

NASA Astrophysics Data System (ADS)

Belghith, Akram; Bowd, Christopher; Weinreb, Robert N.; Zangwill, Linda M.

2014-03-01

Glaucoma is an ocular disease characterized by distinctive changes in the optic nerve head (ONH) and visual field. Glaucoma can strike without symptoms and causes blindness if it remains without treatment. Therefore, early disease detection is important so that treatment can be initiated and blindness prevented. In this context, important advances in technology for non-invasive imaging of the eye have been made providing quantitative tools to measure structural changes in ONH topography, an essential element for glaucoma detection and monitoring. 3D spectral domain optical coherence tomography (SD-OCT), an optical imaging technique, has been commonly used to discriminate glaucomatous from healthy subjects. In this paper, we present a new framework for detection of glaucoma progression using 3D SD-OCT images. In contrast to previous works that the retinal nerve fiber layer (RNFL) thickness measurement provided by commercially available spectral-domain optical coherence tomograph, we consider the whole 3D volume for change detection. To integrate a priori knowledge and in particular the spatial voxel dependency in the change detection map, we propose the use of the Markov Random Field to handle a such dependency. To accommodate the presence of false positive detection, the estimated change detection map is then used to classify a 3D SDOCT image into the "non-progressing" and "progressing" glaucoma classes, based on a fuzzy logic classifier. We compared the diagnostic performance of the proposed framework to existing methods of progression detection.

A joint estimation detection of Glaucoma progression in 3D spectral domain optical coherence tomography optic nerve head images.

PubMed

Belghith, Akram; Bowd, Christopher; Weinreb, Robert N; Zangwill, Linda M

2014-03-18

Glaucoma is an ocular disease characterized by distinctive changes in the optic nerve head (ONH) and visual field. Glaucoma can strike without symptoms and causes blindness if it remains without treatment. Therefore, early disease detection is important so that treatment can be initiated and blindness prevented. In this context, important advances in technology for non-invasive imaging of the eye have been made providing quantitative tools to measure structural changes in ONH topography, an essential element for glaucoma detection and monitoring. 3D spectral domain optical coherence tomography (SD-OCT), an optical imaging technique, has been commonly used to discriminate glaucomatous from healthy subjects. In this paper, we present a new framework for detection of glaucoma progression using 3D SD-OCT images. In contrast to previous works that the retinal nerve fiber layer (RNFL) thickness measurement provided by commercially available spectral-domain optical coherence tomograph, we consider the whole 3D volume for change detection. To integrate a priori knowledge and in particular the spatial voxel dependency in the change detection map, we propose the use of the Markov Random Field to handle a such dependency. To accommodate the presence of false positive detection, the estimated change detection map is then used to classify a 3D SDOCT image into the "non-progressing" and "progressing" glaucoma classes, based on a fuzzy logic classifier. We compared the diagnostic performance of the proposed framework to existing methods of progression detection.

Probing coherence in microcavity frequency combs via optical pulse shaping

NASA Astrophysics Data System (ADS)

Ferdous, Fahmida; Miao, Houxun; Wang, Pei-Hsun; Leaird, Daniel E.; Srinivasan, Kartik; Chen, Lei; Aksyuk, Vladimir; Weiner, Andrew M.

2012-09-01

Recent investigations of microcavity frequency combs based on cascaded four-wave mixing have revealed a link between the evolution of the optical spectrum and the observed temporal coherence. Here we study a silicon nitride microresonator for which the initial four-wave mixing sidebands are spaced by multiple free spectral ranges (FSRs) from the pump, then fill in to yield a comb with single FSR spacing, resulting in partial coherence. By using a pulse shaper to select and manipulate the phase of various subsets of spectral lines, we are able to probe the structure of the coherence within the partially coherent comb. Our data demonstrate strong variation in the degree of mutual coherence between different groups of lines and provide support for a simple model of partially coherent comb formation.

A case study of a multiply talented savant with an autism spectrum disorder: neuropsychological functioning and brain morphometry.

PubMed

Wallace, Gregory L; Happé, Francesca; Giedd, Jay N

2009-05-27

Neuropsychological functioning and brain morphometry in a savant (case GW) with an autism spectrum disorder (ASD) and both calendar calculation and artistic skills are quantified and compared with small groups of neurotypical controls. Good memory, mental calculation and visuospatial processing, as well as (implicit) knowledge of calendar structure and 'weak' central coherence characterized the cognitive profile of case GW. Possibly reflecting his savant skills, the superior parietal region of GW's cortex was the only area thicker (while areas such as the superior and medial prefrontal, middle temporal and motor cortices were thinner) than that of a neurotypical control group. Taken from the perspective of learning/practice-based models, skills in domains (e.g. calendars, art, music) that capitalize upon strengths often associated with ASD, such as detail-focused processing, are probably further enhanced through over-learning and massive exposure, and reflected in atypical brain structure.

A case study of a multiply talented savant with an autism spectrum disorder: neuropsychological functioning and brain morphometry

PubMed Central

Wallace, Gregory L.; Happé, Francesca; Giedd, Jay N.

2009-01-01

Neuropsychological functioning and brain morphometry in a savant (case GW) with an autism spectrum disorder (ASD) and both calendar calculation and artistic skills are quantified and compared with small groups of neurotypical controls. Good memory, mental calculation and visuospatial processing, as well as (implicit) knowledge of calendar structure and ‘weak’ central coherence characterized the cognitive profile of case GW. Possibly reflecting his savant skills, the superior parietal region of GW's cortex was the only area thicker (while areas such as the superior and medial prefrontal, middle temporal and motor cortices were thinner) than that of a neurotypical control group. Taken from the perspective of learning/practice-based models, skills in domains (e.g. calendars, art, music) that capitalize upon strengths often associated with ASD, such as detail-focused processing, are probably further enhanced through over-learning and massive exposure, and reflected in atypical brain structure. PMID:19528026

Learning the Gestalt rule of collinearity from object motion.

PubMed

Prodöhl, Carsten; Würtz, Rolf P; von der Malsburg, Christoph

2003-08-01

The Gestalt principle of collinearity (and curvilinearity) is widely regarded as being mediated by the long-range connection structure in primary visual cortex. We review the neurophysiological and psychophysical literature to argue that these connections are developed from visual experience after birth, relying on coherent object motion. We then present a neural network model that learns these connections in an unsupervised Hebbian fashion with input from real camera sequences. The model uses spatiotemporal retinal filtering, which is very sensitive to changes in the visual input. We show that it is crucial for successful learning to use the correlation of the transient responses instead of the sustained ones. As a consequence, learning works best with video sequences of moving objects. The model addresses a special case of the fundamental question of what represents the necessary a priori knowledge the brain is equipped with at birth so that the self-organized process of structuring by experience can be successful.

[NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 18:] Scientific and Technical Information (STI) policy and the competitive position of the US aerospace industry

NASA Technical Reports Server (NTRS)

Hernon, Peter; Pinelli, Thomas E.

1992-01-01

With its contribution to trade, its coupling with national security, and its symbolism of U.S. technological strength, the U.S. aerospace industry holds a unique position in the Nation's industrial structure. Federal science and technology policy and Federal scientific and technical information (STI) policy loom important as strategic contributions to the U.S. aerospace industry's leading competitive position. However, three fundamental policy problems exist. First, the United States lacks a coherent STI policy and a unified approach to the development of such a policy. Second, policymakers fail to understand the relationship of STI to science and technology policy. Third, STI is treated as a part of general information policy, without any recognition of its uniqueness. This paper provides an overview of the Federal information policy structure as it relates to STI and frames the policy issues that require resolution.

NASA/DOD Aerospace Knowledge Diffusion Research Project. Paper 18: Scientific and Technical Information (STI) policy and the competitive position of the US aerospace industry

NASA Technical Reports Server (NTRS)

Hernon, Peter; Pinelli, Thomas E.

1992-01-01

With its contribution to trade, its coupling with national security, and its symbolism of U.S. technological strength, the U.S. aerospace industry holds a unique position in the Nation's industrial structure. Federal science and technology policy and Federal scientific and technical information (STI) policy loom important as strategic contributions to the U.S. aerospace industry's leading competitive position. However, three fundamental policy problems exist. First, the United States lacks a coherent STI policy and a unified approach to the development of such a policy. Second, policymakers fail to understand the relationship of STI to science and technology policy. Third, STI is treated as a part of general information policy, without any recognition of its uniqueness. This paper provides an overview of the Federal information policy structure as it relates to STI and frames the policy issues that require resolution.

The pieces fit: Constituent structure and global coherence of visual narrative in RSVP.

PubMed

Hagmann, Carl Erick; Cohn, Neil

2016-02-01

Recent research has shown that comprehension of visual narrative relies on the ordering and timing of sequential images. Here we tested if rapidly presented 6-image long visual sequences could be understood as coherent narratives. Half of the sequences were correctly ordered and half had two of the four internal panels switched. Participants reported whether the sequence was correctly ordered and rated its coherence. Accuracy in detecting a switch increased when panels were presented for 1 s rather than 0.5 s. Doubling the duration of the first panel did not affect results. When two switched panels were further apart, order was discriminated more accurately and coherence ratings were low, revealing that a strong local adjacency effect influenced order and coherence judgments. Switched panels at constituent boundaries or within constituents were most disruptive to order discrimination, indicating that the preservation of constituent structure is critical to visual narrative grammar. Copyright © 2016 Elsevier B.V. All rights reserved.

Holographic Optical Coherence Imaging of Rat Osteogenic Sarcoma Tumor Spheroids

NASA Astrophysics Data System (ADS)

Yu, Ping; Mustata, Mirela; Peng, Leilei; Turek, John J.; Melloch, Michael R.; French, Paul M. W.; Nolte, David D.

2004-09-01

Holographic optical coherence imaging is a full-frame variant of coherence-domain imaging. An optoelectronic semiconductor holographic film functions as a coherence filter placed before a conventional digital video camera that passes coherent (structure-bearing) light to the camera during holographic readout while preferentially rejecting scattered light. The data are acquired as a succession of en face images at increasing depth inside the sample in a fly-through acquisition. The samples of living tissue were rat osteogenic sarcoma multicellular tumor spheroids that were grown from a single osteoblast cell line in a bioreactor. Tumor spheroids are nearly spherical and have radial symmetry, presenting a simple geometry for analysis. The tumors investigated ranged in diameter from several hundred micrometers to over 1 mm. Holographic features from the tumors were observed in reflection to depths of 500-600 µm with a total tissue path length of approximately 14 mean free paths. The volumetric data from the tumor spheroids reveal heterogeneous structure, presumably caused by necrosis and microcalcifications characteristic of some human avascular tumors.

Coherent Exciton Dynamics in GaAs-Based Semiconductor Structures

NASA Astrophysics Data System (ADS)

Colocci, M.; Bogani, F.; Ceccherini, S.; Gurioli, M.

We show that a very powerful tool in the investigation of the coherent exciton dynamics in semiconductors is provided by the study of the emitted light after resonant excitation from pairs of phase-locked femtosecond pulses. Under these conditions, not only the full dynamics of the coherent transients (dephasing times, quantum beat periods, etc.) can be obtained from linear experiments, but it can also be obtained a straightforward discrimination between the coherent or incoherent character of the emission by means of spectral filtering.

Advances in the Surface Renewal Flux Measurement Method

NASA Astrophysics Data System (ADS)

Shapland, T. M.; McElrone, A.; Paw U, K. T.; Snyder, R. L.

2011-12-01

The measurement of ecosystem-scale energy and mass fluxes between the planetary surface and the atmosphere is crucial for understanding geophysical processes. Surface renewal is a flux measurement technique based on analyzing the turbulent coherent structures that interact with the surface. It is a less expensive technique because it does not require fast-response velocity measurements, but only a fast-response scalar measurement. It is therefore also a useful tool for the study of the global cycling of trace gases. Currently, surface renewal requires calibration against another flux measurement technique, such as eddy covariance, to account for the linear bias of its measurements. We present two advances in the surface renewal theory and methodology that bring the technique closer to becoming a fully independent flux measurement method. The first advance develops the theory of turbulent coherent structure transport associated with the different scales of coherent structures. A novel method was developed for identifying the scalar change rate within structures at different scales. Our results suggest that for canopies less than one meter in height, the second smallest coherent structure scale dominates the energy and mass flux process. Using the method for resolving the scalar exchange rate of the second smallest coherent structure scale, calibration is unnecessary for surface renewal measurements over short canopies. This study forms the foundation for analysis over more complex surfaces. The second advance is a sensor frequency response correction for measuring the sensible heat flux via surface renewal. Inexpensive fine-wire thermocouples are frequently used to record high frequency temperature data in the surface renewal technique. The sensible heat flux is used in conjunction with net radiation and ground heat flux measurements to determine the latent heat flux as the energy balance residual. The robust thermocouples commonly used in field experiments underestimate the sensible heat flux, yielding results that are less than 50% of the sensible heat flux measured with finer sensors. We present the methodology for correcting the thermocouple signal to avoid underestimating the heat flux at both the smallest and the second smallest coherent structure scale.

Emergence of electron coherence and two-color all-optical switching in MoS2 based on spatial self-phase modulation

PubMed Central

Wu, Yanling; Wu, Qiong; Sun, Fei; Cheng, Cai; Meng, Sheng; Zhao, Jimin

2015-01-01

Generating electron coherence in quantum materials is essential in optimal control of many-body interactions and correlations. In a multidomain system this signifies nonlocal coherence and emergence of collective phenomena, particularly in layered 2D quantum materials possessing novel electronic structures and high carrier mobilities. Here we report nonlocal ac electron coherence induced in dispersed MoS2 flake domains, using coherent spatial self-phase modulation (SSPM). The gap-dependent nonlinear dielectric susceptibility χ(3) measured is surprisingly large, where direct interband transition and two-photon SSPM are responsible for excitations above and below the bandgap, respectively. A wind-chime model is proposed to account for the emergence of the ac electron coherence. Furthermore, all-optical switching is achieved based on SSPM, especially with two-color intraband coherence, demonstrating that electron coherence generation is a ubiquitous property of layered quantum materials. PMID:26351696

Method and apparatus for thickness measurement using microwaves

DOEpatents

Woskov, Paul [Bedford, MA; Lamar, David A [West Richland, WA

2001-01-01

The method for measuring the thickness of a material which transmits a detectable amount of microwave radiation includes irradiating the material with coherent microwave radiation tuned over a frequency range. Reflected microwave radiation is detected, the reflected radiation having maxima and minima over the frequency range as a result of coherent interference of microwaves reflected from reflecting surfaces of the material. The thickness of the material is determined from the period of the maxima and minima along with knowledge of the index of refraction of the material.

Label-free imaging of the dynamics of cell-to-cell string-like structure bridging in the free-space by low-coherent quantitative phase microscopy

NASA Astrophysics Data System (ADS)

Yamauchi, Toyohiko; Iwai, Hidenao; Yamashita, Yutaka

2013-03-01

We succeeded in utilizing our low-coherent quantitative phase microscopy (LC-QPM) to achieve label-free and three-dimensional imaging of string-like structures bridging the free-space between live cells. In past studies, three dimensional morphology of the string-like structures between cells had been investigated by electron microscopies and fluorescence microscopies and these structures were called "membrane nanotubes" or "tunneling nanotubes." However, use of electron microscopy inevitably kills these cells and fluorescence microscopy is itself a potentially invasive method. To achieve noninvasive imaging of live cells, we applied our LC-QPM which is a reflection-type, phase resolved and full-field interference microscope employing a low-coherent light source. LC-QPM is able to visualize the three-dimensional morphology of live cells without labeling by means of low-coherence interferometry. The lateral (diffraction limit) and longitudinal (coherence-length) spatial resolution of LC-QPM were respectively 0.49 and 0.93 micrometers and the repeatability of the phase measurement was 0.02 radians (1.0 nm). We successfully obtained three-dimensional morphology of live cultured epithelial cells (cell type: HeLa, derived from cervix cancer) and were able to clearly observe the individual string-like structures interconnecting the cells. When we performed volumetric imaging, a 80 micrometer by 60 micrometer by 6.5 micrometer volume was scanned every 5.67 seconds and 70 frames of a three-dimensional movie were recorded for a duration of 397 seconds. Moreover, the optical phase images gave us detailed information about the three-dimensional morphology of the string-like structure at sub-wavelength resolution. We believe that our LC-QPM will be a useful tool for the study of three-dimensional morphology of live cells.

Investigating molecule-semiconductor interfaces with nonlinear spectroscopies

NASA Astrophysics Data System (ADS)

Giokas, Paul George

Knowledge of electronic structures and transport mechanisms at molecule-semiconductor interfaces is motivated by their ubiquity in photoelectrochemical cells. In this dissertation, optical spectroscopies are used uncover the influence of electronic coupling, coherent vibrational motion, and molecular geometry, and other factors on dynamics initiated by light absorption at such interfaces. These are explored for a family of ruthenium bipyridyl chromophores bound to titanium dioxide. Transient absorption measurements show molecular singlet state electron injection in 100 fs or less. Resonance Raman intensity analysis suggests the electronic excitations possess very little charge transfer character. The connections drawn in this work between molecular structure and photophysical behavior contribute to the general understanding of photoelectrochemical cells. Knowledge of binding geometry in nanocrystalline films is challenged by heterogeneity of semiconductor surfaces. Polarized resonance Raman spectroscopy is used to characterize the ruthenium chromophore family on single crystal titanium dioxide . Chromophores display a broad distribution of molecular geometries at the interface, with increased variation in binding angle due to the presence of a methylene bridge, as well as additional phosphonate anchors. This result implies multiple binding configurations for chromophores which incorporate multiple phosphonate ligands, and indicates the need for careful consideration when developing surface-assembled chromophore-catalyst cells. Electron transfer transitions occurring on the 100 fs time scale challenge conventional second-order approximations made when modeling these reactions. A fourth-order perturbative model which includes the relationship between coincident electron transfer and nuclear relaxation processes is presented. Insights provided by the model are illustrated for a two-level donor molecule. The presented fourth-order rate formula constitutes a rigorous and intuitive framework for understanding sub-picosecond photoinduced electron transfer dynamics. Charge transfer systems fit by this model include catechol-sensitized titanium dioxide nanoparticles and a closely-related molecular complex. These systems exhibit vibrational coherence coincident with back-electron transfer in the first picosecond after excitation, which suggests that intramolecular nuclear motion strongly influences the electronic transfer process and plays an important role in the dynamics of interfacial systems following light absorption.

Temporal coherence among tropical coastal lagoons: a search for patterns and mechanisms.

PubMed

Caliman, A; Carneiro, L S; Santangelo, J M; Guariento, R D; Pires, A P F; Suhett, A L; Quesado, L B; Scofield, V; Fonte, E S; Lopes, P M; Sanches, L F; Azevedo, F D; Marinho, C C; Bozelli, R L; Esteves, F A; Farjalla, V F

2010-10-01

Temporal coherence (i.e., the degree of synchronicity of a given variable among ecological units within a predefined space) has been shown for several limnological features among temperate lakes, allowing predictions about the structure and function of ecosystems. However, there is little evidence of temporal coherence among tropical aquatic systems, where the climatic variability among seasons is less pronounced. Here, we used data from long-term monitoring of physical, chemical and biological variables to test the degree of temporal coherence among 18 tropical coastal lagoons. The water temperature and chlorophyll-a concentration had the highest and lowest temporal coherence among the lagoons, respectively, whereas the salinity and water colour had intermediate temporal coherence. The regional climactic factors were the main factors responsible for the coherence patterns in the water temperature and water colour, whereas the landscape position and morphometric characteristics explained much of the variation of the salinity and water colour among the lagoons. These results indicate that both local (lagoon morphometry) and regional (precipitation, air temperature) factors regulate the physical and chemical conditions of coastal lagoons by adjusting the terrestrial and marine subsidies at a landscape-scale. On the other hand, the chlorophyll-a concentration appears to be primarily regulated by specific local conditions resulting in a weak temporal coherence among the ecosystems. We concluded that temporal coherence in tropical ecosystems is possible, at least for some environmental features, and should be evaluated for other tropical ecosystems. Our results also reinforce that aquatic ecosystems should be studied more broadly to accomplish a full understanding of their structure and function.

E-learning implementation in superior technical educational system

NASA Astrophysics Data System (ADS)

Musca, Gavril; Mihalache, Andrei; Musca, Elena

2016-11-01

E-learning methods apply to most modern and various domains but also represent a great tool for the mechanical educational system where there are a lot of sustained efforts for its implementation. Using, administrating and maintaining an e-learning system for a certain field of study requires knowledge related to computation system's utilization but also the understanding the working mechanisms behind it that allows the system to be fully customized in order to be perfect fitted to the user's needs and requirements. A Moodle based test is evaluated from several points of views such as coherence clarity, concise content, information synthesis capacity and the presentation mode which makes the difference between clear or fuzzy graphical representations or terms. The authors appreciate that the ability of managing information in real time by the professor is a decisive decision in order to successfully implement an e-learning web platform. Updating information and structuring trainee's activities from thoroughgoing study up to their individual proposals for conceived applications leads to a better understanding and practical knowledge of theory.

Misconceptions Yesterday, Today, and Tomorrow

PubMed Central

Kalinowski, Steven T.; Andrews, Tessa C.

2014-01-01

A recent essay in CBE—Life Sciences Education criticized biology education researchers’ use of the term misconceptions and recommended that, in order to be up-to-date with education research, biology education researchers should use alternative terms for students’ incorrect ideas in science. We counter that criticism by reviewing the continued use and the meaning of misconceptions in education research today, and describe two key debates that account for the controversy surrounding the term. We then identify and describe two areas of research that have real implications for tomorrow's biology education research and biology instruction: 1) hypotheses about the structure of student knowledge (coherent vs. fragmented) that gives rise to misconceptions; and 2) the “warming trend” that considers the effects of students’ motivation, beliefs about the nature of knowledge and learning (their epistemic beliefs), and learning strategies (their cognitive and metacognitive skills) on their ability to change their misconceptions in science. We conclude with a description of proposed future work in biology education research related to misconceptions. PMID:26086651

Geostrophic Vortex Dynamics

DTIC Science & Technology

1988-10-01

Generalized Kirchhoff Vortices 176 B. The 2-Level Rankine Vortex: Critical Points & Stability 181 C. Tripolar Coherent Euler Vortices 186 7...spontaneously in spectral simulations. One such example is provided by the tripolar vortex structureE which will be examined in detail in Chapter 6. It...of the tripolar coherent vortex structures that have recently been observed in very high resolution numerical simulations of two- dimensional

Optical coherence tomography of dental structures

NASA Astrophysics Data System (ADS)

Baumgartner, Angela; Hitzenberger, Christoph K.; Dichtl, Sabine; Sattmann, Harald; Moritz, Andreas; Sperr, Wolfgang; Fercher, Adolf F.

1998-04-01

In the past ten years Partial Coherence Interferometry (PCI) and Optical Coherence Tomography (OCT) have been successfully developed for high precision biometry and tomography of biological tissues. OCT employs the partial coherence properties of a superluminescent diode and the Doppler principle yielding resolution and precision figures of the order of a few microns. Presently, the main application fields of this technique are biometry and imaging of ocular structures in vivo, as well as its clinical use in dermatology and endoscopic applications. This well established length measuring and imaging technique has now been applied to dentistry. First in vitro OCT images of the cemento (dentine) enamel junction of extracted sound and decayed human teeth have been recorded. These images distinguish dentine and enamel structures that are important for assessing enamel thickness and diagnosing caries. Individual optical A-Scans show that the penetration depth into enamel is considerably larger than into dentine. First polarization sensitive OCT recordings show localized changes of the polarization state of the light backscattered by dental material. Two-dimensional maps of the magnitude of the interference intensity and of the total phase difference between two orthogonal polarization states as a function of depth can reveal important structural information.

Revisiting the Al/Al 2O 3 Interface: Coherent Interfaces and Misfit Accommodation

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pilania, Ghanshyam; Thijsse, Barend J.; Hoagland, Richard G.

We report the coherent and semi-coherent Al/α-Al 2O 3 interfaces using molecular dynamics simulations with a mixed, metallic-ionic atomistic model. For the coherent interfaces, both Al-terminated and O-terminated nonstoichiometric interfaces have been studied and their relative stability has been established. To understand the misfit accommodation at the semi-coherent interface, a 1-dimensional (1D) misfit dislocation model and a 2-dimensional (2D) dislocation network model have been studied. For the latter case, our analysis reveals an interface dislocation structure with a network of three sets of parallel dislocations, each with pure-edge character, giving rise to a pattern of coherent and stacking-fault-like regions atmore » the interface. Structural relaxation at elevated temperatures leads to a further change of the dislocation pattern, which can be understood in terms of a competition between the stacking fault energy and the dislocation interaction energy at the interface. In conclusion, our results are expected to serve as an input for the subsequent dislocation dynamics models to understand and predict the macroscopic mechanical behavior of Al/α-Al 2O 3 composite heterostructures.« less

Revisiting the Al/Al 2O 3 Interface: Coherent Interfaces and Misfit Accommodation

DOE PAGES

Pilania, Ghanshyam; Thijsse, Barend J.; Hoagland, Richard G.; ...

2014-03-27

We report the coherent and semi-coherent Al/α-Al 2O 3 interfaces using molecular dynamics simulations with a mixed, metallic-ionic atomistic model. For the coherent interfaces, both Al-terminated and O-terminated nonstoichiometric interfaces have been studied and their relative stability has been established. To understand the misfit accommodation at the semi-coherent interface, a 1-dimensional (1D) misfit dislocation model and a 2-dimensional (2D) dislocation network model have been studied. For the latter case, our analysis reveals an interface dislocation structure with a network of three sets of parallel dislocations, each with pure-edge character, giving rise to a pattern of coherent and stacking-fault-like regions atmore » the interface. Structural relaxation at elevated temperatures leads to a further change of the dislocation pattern, which can be understood in terms of a competition between the stacking fault energy and the dislocation interaction energy at the interface. In conclusion, our results are expected to serve as an input for the subsequent dislocation dynamics models to understand and predict the macroscopic mechanical behavior of Al/α-Al 2O 3 composite heterostructures.« less

Modulating the amplitude and phase of the complex spectral degree of coherence with plasmonic interferometry

NASA Astrophysics Data System (ADS)

Li, Dongfang; Pacifici, Domenico

The spectral degree of coherence describes the correlation of electromagnetic fields, which plays a key role in many applications, including free-space optical communications and speckle-free bioimaging. Recently, plasmonic interferometry, i.e. optical interferometry that employs surface plasmon polaritons (SPPs), has enabled enhanced light transmission and high-sensitivity biosensing, among other applications. It offers new ways to characterize and engineer electromagnetic fields using nano-structured thin metal films. Here, we employ plasmonic interferometry to demonstrate full control of spatial coherence at length scales comparable to the wavelength of the incident light. Specifically, by measuring the diffraction pattern of several double-slit plasmonic structures etched on a metal film, the amplitude and phase of the degree of spatial coherence is determined as a function of slit-slit separation distance and incident wavelength. When the SPP contribution is turned on (i.e., by changing the polarization of the incident light from TE to TM illumination mode), strong modulation of both amplitude and phase of the spatial coherence is observed. These findings may help design compact modulators of optical spatial coherence and other optical elements to shape the light intensity in the far-field.

Maintaining research traditions on place: diversity of thought and scientific progress

Treesearch

Michael E. Patterson; Daniel R. Williams

2005-01-01

Since the 1990s, numerous authors have expressed concerns about lack of conceptual clarity in research on place. Some authors suggest that place research has failed to evolve into a systematic and coherent body of knowledge. We believe recent critiques do not adequately characterize the state of knowledge in place research, but responding to the issues raised requires...

Developing Conceptual Understanding and Procedural Fluency for Junior High School Students through Model-Facilitated Learning (MFL)

ERIC Educational Resources Information Center

Laswadi; Kusumah, Yaya S.; Darwis, Sutawanir; Afgani, Jarnawi D.

2016-01-01

Conceptual understanding (CU) and procedural fluency (PF) are two important mathematical competencies required by students. CU helps students organizing their knowledge into a coherent whole, and PF helps them to find the right solution of a problem. In order to enhance CU and PF, students need learning experiences in constructing knowledge and…

Optimal spectral structure for simultaneous Stimulated Brillouin Scattering suppression and coherent property preservation in high power coherent beam combination system

NASA Astrophysics Data System (ADS)

Han, Kai; Xu, Xiaojun; Liu, Zejin

2013-05-01

Based on the spectral manipulation technique, the Stimulated Brillouin Scattering (SBS) suppression effect and the coherent beam combination (CBC) effect in multi-tone CBC system are researched theoretically and experimentally. To get satisfactory SBS suppression, the frequency interval of the multi-tone seed laser should be large enough, at least larger than the SBS gain bandwidth. In order to attain excellent CBC effect, the spectra of the multi-tone seed laser need to be matched with the optical path differences among the amplifier chains. Hence, a sufficiently separated matching spectrum is capable at both SBS mitigation and coherent property preservation. By comparing the SBS suppression effect and the CBC effect at various spectra, the optimal spectral structure for simultaneous SBS suppression and excellent CBC effect is found.

Enhancing the isotropy of lateral resolution in coherent structured illumination microscopy

PubMed Central

Park, Joo Hyun; Lee, Jae Yong; Lee, Eun Seong

2014-01-01

We present a method to improve the isotropy of spatial resolution in a structured illumination microscopy (SIM) implemented for imaging non-fluorescent samples. To alleviate the problem of anisotropic resolution involved with the previous scheme of coherent SIM that employs the two orthogonal standing-wave illumination, referred to as the orthogonal SIM, we introduce a hexagonal-lattice illumination that incorporates three standing-wave fields simultaneously superimposed at the orientations equally divided in the lateral plane. A theoretical formulation is worked out rigorously for the coherent image formation with such a simultaneous multiple-beam illumination and an explicit Fourier-domain framework is derived for reconstructing an image with enhanced resolution. Using a computer-synthesized resolution target as a 2D coherent sample, we perform numerical simulations to examine the imaging characteristics of our three-angle SIM compared with the orthogonal SIM. The investigation on the 2D resolving power with the various test patterns of different periods and orientations reveal that the orientation-dependent undulation of lateral resolution can be reduced from 27% to 8% by using the three-angle SIM while the best resolution (0.54 times the resolution limit of conventional coherent imaging) in the directions of structured illumination is slightly deteriorated by 4.6% from that of the orthogonal SIM. PMID:24940548

Characterization of turbulent coherent structures in square duct flow

NASA Astrophysics Data System (ADS)

Atzori, Marco; Vinuesa, Ricardo; Lozano-Durán, Adrián; Schlatter, Philipp

2018-04-01

This work is aimed at a first characterization of coherent structures in turbulent square duct flows. Coherent structures are defined as connected components in the domain identified as places where a quantity of interest (such as Reynolds stress or vorticity) is larger than a prescribed non-uniform threshold. Firstly, we qualitatively discuss how a percolation analysis can be used to assess the effectiveness of the threshold function, and how it can be affected by statistical uncertainty. Secondly, various physical quantities that are expected to play an important role in the dynamics of the secondary flow of Prandtl’s second kind are studied. Furthermore, a characterization of intense Reynolds-stress events in square duct flow, together with a comparison of their shape for analogous events in channel flow at the same Reynolds number, is presented.

Polarimetric subspace target detector for SAR data based on the Huynen dihedral model

NASA Astrophysics Data System (ADS)

Larson, Victor J.; Novak, Leslie M.

1995-06-01

Two new polarimetric subspace target detectors are developed based on a dihedral signal model for bright peaks within a spatially extended target signature. The first is a coherent dihedral target detector based on the exact Huynen model for a dihedral. The second is a noncoherent dihedral target detector based on the Huynen model with an extra unknown phase term. Expressions for these polarimetric subspace target detectors are developed for both additive Gaussian clutter and more general additive spherically invariant random vector clutter including the K-distribution. For the case of Gaussian clutter with unknown clutter parameters, constant false alarm rate implementations of these polarimetric subspace target detectors are developed. The performance of these dihedral detectors is demonstrated with real millimeter-wave fully polarimetric SAR data. The coherent dihedral detector which is developed with a more accurate description of a dihedral offers no performance advantage over the noncoherent dihedral detector which is computationally more attractive. The dihedral detectors do a better job of separating a set of tactical military targets from natural clutter compared to a detector that assumes no knowledge about the polarimetric structure of the target signal.

Children's conceptions of mental illness: a naïve theory approach.

PubMed

Fox, Claudine; Buchanan-Barrow, Eithne; Barrett, Martyn

2010-09-01

This paper reports two studies that investigated children's conceptions of mental illness using a naïve theory approach, drawing upon a conceptual framework for analysing illness representations which distinguishes between the identity, causes, consequences, curability, and timeline of an illness. The studies utilized semi-structured interviewing and card selection tasks to assess 6- to 11-year-old children's conceptions of the causes and consequences (Study 1) and the curability and timeline (Study 2) of different mental and physical illnesses/ailments. The studies revealed that, at all ages, the children held coherent causal-explanatory ideas about the causes, consequences, curability, and timeline of both mental and physical illnesses/ailments. However, while younger children tended to rely on their knowledge of common physical illnesses when thinking about mental illnesses, providing contagion and contamination explanations of cause, older children demonstrated differences in their thinking about mental and physical illnesses. No substantial gender differences were found in the children's thinking. It is argued that children hold coherent conceptions of mental illness at all ages, but that mental illness only emerges as an ontologically distinct conceptual domain by the end of middle childhood.

Multimodality bonchoscopic imaging of tracheopathica osteochondroplastica

NASA Astrophysics Data System (ADS)

Colt, Henri; Murgu, Septimiu D.; Ahn, Yeh-Chan; Brenner, Matt

2009-05-01

Results of a commercial optical coherence tomography system used as part of a multimodality diagnostic bronchoscopy platform are presented for a 61-year-old patient with central airway obstruction from tracheopathica osteochondroplastica. Comparison to results of white-light bronchoscopy, histology, and endobronchial ultrasound examination are accompanied by a discussion of resolution, penetration depth, contrast, and field of view of these imaging modalities. White-light bronchoscopy revealed irregularly shaped, firm submucosal nodules along cartilaginous structures of the anterior and lateral walls of the trachea, sparing the muscular posterior membrane. Endobronchial ultrasound showed a hyperechoic density of 0.4 cm thickness. optical coherence tomography (OCT) was performed using a commercially available, compact time-domain OCT system (Niris System, Imalux Corp., Cleveland, Ohio) with a magnetically actuating probe (two-dimensional, front imaging, and inside actuation). Images showed epithelium, upper submucosa, and osseous submucosal nodule layers corresponding with histopathology. To our knowledge, this is the first time these commercially available systems are used as part of a multimodality bronchoscopy platform to study diagnostic imaging of a benign disease causing central airway obstruction. Further studies are needed to optimize these systems for pulmonary applications and to determine how new-generation imaging modalities will be integrated into a multimodality bronchoscopy platform.

Determination of secondary flow morphologies by wavelet analysis in a curved artery model with physiological inflow

NASA Astrophysics Data System (ADS)

Bulusu, Kartik V.; Hussain, Shadman; Plesniak, Michael W.

2014-11-01

Secondary flow vortical patterns in arterial curvatures have the potential to affect several cardiovascular phenomena, e.g., progression of atherosclerosis by altering wall shear stresses, carotid atheromatous disease, thoracic aortic aneurysms and Marfan's syndrome. Temporal characteristics of secondary flow structures vis-à-vis physiological (pulsatile) inflow waveform were explored by continuous wavelet transform (CWT) analysis of phase-locked, two-component, two-dimensional particle image velocimeter data. Measurements were made in a 180° curved artery test section upstream of the curvature and at the 90° cross-sectional plane. Streamwise, upstream flow rate measurements were analyzed using a one-dimensional antisymmetric wavelet. Cross-stream measurements at the 90° location of the curved artery revealed interesting multi-scale, multi-strength coherent secondary flow structures. An automated process for coherent structure detection and vortical feature quantification was applied to large ensembles of PIV data. Metrics such as the number of secondary flow structures, their sizes and strengths were generated at every discrete time instance of the physiological inflow waveform. An autonomous data post-processing method incorporating two-dimensional CWT for coherent structure detection was implemented. Loss of coherence in secondary flow structures during the systolic deceleration phase is observed in accordance with previous research. The algorithmic approach presented herein further elucidated the sensitivity and dependence of morphological changes in secondary flow structures on quasiperiodicity and magnitude of temporal gradients in physiological inflow conditions.

The dynamics of coherent flow structures within a submerged permeable bed

NASA Astrophysics Data System (ADS)

Blois, G.; Best, J.; Sambrook Smith, G.; Hardy, R. J.; Lead, J.

2009-12-01

The existence of complex 3D coherent vortical structures in turbulent boundary layers has been widely reported from experimental observations (Adrian et al., 2007, Christensen and Adrian, 2001) and investigations of natural open channel flows (e.g. Kostaschuk and Church, 1993; Best, 2005). The interaction between these flow structures and the solid boundary that is responsible for their generation is also receiving increasing attention due to the central role played by turbulence in governing erosion-deposition processes. Yet, for the majority of studies, the bed roughness has been represented using rough impermeable surfaces. While not inherently acknowledged, most research in this area is thus only strictly applicable to those natural river beds composed either of bedrock or clay, or that have armoured, impermeable, surfaces. Recently, many researchers have noted the need to account for the role of bed permeability in order to accurately reproduce the true nature of flow over permeable gravel-bed rivers. For these cases, the near-bed flow is inherently and mutually linked to the interstitial-flow occurring in the porous solid matrix. This interaction is established through turbulence mechanisms occurring across the interface that may be important for influencing the incipient motion of cohesionless sediment. However, the nature of this turbulence and the formation of coherent structures within such permeable beds remain substantially unresolved due to the technical challenges of collecting direct data in this region. In this paper, we detail the existence and dynamic nature of coherent vortical structures within the individual pore spaces of a permeable bed submerged by a free stream flow. Laboratory experiments are reported in which a permeable flume bed was constructed using spheres packed in an offset cubic arrangement. We applied a high resolution E-PIV (Endoscopic Particle Image Velocimetry) approach in order to fully resolve the instantaneous structure of flow within the permeable bed, which allowed visualisation of coherent vortices in the pore space, and investigation of their formative mechanisms and spatio-temporal evolution. The spatial scale of these structures is found to be of the order of the pore space, with jet flows occurring between interconnected pores and interacting with the spherical particles constituting the solid matrix. Such jets are hypothesized to be triggered by the interstitial pressure gradients between interconnected pores, which in turn are linked to large-scale coherent flow structures in the free-flow that advect and propagate through the permeable bed. As the jet flow interacts with the matrix around the pore space, coherent flow structures are generated with both clockwise and anticlockwise rotation. The nature of these subsurface turbulent flow patterns will be presented, which allows new insight into flows within permeable beds and the hydrodynamic processes triggering the motion of sediment.

Scatter sensitive microscopic techniques to identify contrasting mucosal structures in ultrahigh-resolution optical coherence tomograms of mouse colon

NASA Astrophysics Data System (ADS)

Tumlinson, Alexandre R.; Hariri, Lida P.; Drexler, Wolfgang; Barton, Jennifer K.

2008-02-01

Optical coherence tomography, optical coherence microscopy, reflectance confocal microscopy, and darkfield microscopy all derive contrast from the intensity of endogenous tissue scatter. We have imaged excised mouse colon tissue with these complimentary technologies to make conclusions about structural origins of scatter in the mouse colonic mucosa observed with endoscopic OCT. We find hyperintense scattering both from the cytoplasm of epithelial cells and from the boundary between epithelia and the lamina propria. We find almost no scatter from the portion of epithelial cells containing the nucleus. These observations substantiate explanations for the appearance of colonic crypts and the luminal surface.

Communication: Coherences observed in vivo in photosynthetic bacteria using two-dimensional electronic spectroscopy

NASA Astrophysics Data System (ADS)

Dahlberg, Peter D.; Norris, Graham J.; Wang, Cheng; Viswanathan, Subha; Singh, Ved P.; Engel, Gregory S.

2015-09-01

Energy transfer through large disordered antenna networks in photosynthetic organisms can occur with a quantum efficiency of nearly 100%. This energy transfer is facilitated by the electronic structure of the photosynthetic antennae as well as interactions between electronic states and the surrounding environment. Coherences in time-domain spectroscopy provide a fine probe of how a system interacts with its surroundings. In two-dimensional electronic spectroscopy, coherences can appear on both the ground and excited state surfaces revealing detailed information regarding electronic structure, system-bath coupling, energy transfer, and energetic coupling in complex chemical systems. Numerous studies have revealed coherences in isolated photosynthetic pigment-protein complexes, but these coherences have not been observed in vivo due to the small amplitude of these signals and the intense scatter from whole cells. Here, we present data acquired using ultrafast video-acquisition gradient-assisted photon echo spectroscopy to observe quantum beating signals from coherences in vivo. Experiments were conducted on isolated light harvesting complex II (LH2) from Rhodobacter sphaeroides, whole cells of R. sphaeroides, and whole cells of R. sphaeroides grown in 30% deuterated media. A vibronic coherence was observed following laser excitation at ambient temperature between the B850 and the B850∗ states of LH2 in each of the 3 samples with a lifetime of ˜40-60 fs.

Broken Symmetries and Magnetic Dynamos

NASA Technical Reports Server (NTRS)

Shebalin, John V.

2007-01-01

Phase space symmetries inherent in the statistical theory of ideal magnetohydrodynamic (MHD) turbulence are known to be broken dynamically to produce large-scale coherent magnetic structure. Here, results of a numerical study of decaying MHD turbulence are presented that show large-scale coherent structure also arises and persists in the presence of dissipation. Dynamically broken symmetries in MHD turbulence may thus play a fundamental role in the dynamo process.

The influence of instructional interactions on students’ mental models about the quantization of physical observables: a modern physics course case

NASA Astrophysics Data System (ADS)

Didiş Körhasan, Nilüfer; Eryılmaz, Ali; Erkoç, Şakir

2016-01-01

Mental models are coherently organized knowledge structures used to explain phenomena. They interact with social environments and evolve with the interaction. Lacking daily experience with phenomena, the social interaction gains much more importance. In this part of our multiphase study, we investigate how instructional interactions influenced students’ mental models about the quantization of physical observables. Class observations and interviews were analysed by studying students’ mental models constructed in a modern physics course during an academic semester. The research revealed that students’ mental models were influenced by (1) the manner of teaching, including instructional methodologies and content specific techniques used by the instructor, (2) order of the topics and familiarity with concepts, and (3) peers.

Cognitive Metaphor Theory and the Metaphysics of Immediacy.

PubMed

Madsen, Mathias W

2016-05-01

One of the core tenets of cognitive metaphor theory is the claim that metaphors ground abstract knowledge in concrete, first-hand experience. In this paper, I argue that this grounding hypothesis contains some problematic conceptual ambiguities and, under many reasonable interpretations, empirical difficulties. I present evidence that there are foundational obstacles to defining a coherent and cognitively valid concept of "metaphor" and "concrete meaning," and some general problems with singling out certain domains of experience as more immediate than others. I conclude from these considerations that whatever the facts are about the comprehension of individual metaphors, the available evidence is incompatible with the notion of an underlying conceptual structure organized according to the immediacy of experience. Copyright © 2015 Cognitive Science Society, Inc.

Analyzing beliefs and practices of a Mexican high school biology teacher

NASA Astrophysics Data System (ADS)

Verjovsky, Janet; Waldegg, Guillermina

2005-04-01

This article explores the beliefs and practices of a high school biology teacher through three interrelated theoretical frameworks: common knowledge, collaborative learning, and communities of practice. The data were obtained from an in-depth case study of Maria, a biology teacher from a Mexican public high school that was participating in a 4-year international science project using collaborative learning and information and communication technology. Her beliefs and practices were explored by means of questionnaires, semi-structured interviews, and nonparticipant observation of classes. Through the use of the three-component framework, the degrees of coherence between practice and beliefs that guide the teacher's daily behavior became apparent, as well as the difficulties of incorporating innovations due to institutional constraints.

Theoretical model for VITA-educed coherent structures in the wall region of a turbulent boundary layer

NASA Technical Reports Server (NTRS)

Landahl, Marten T.

1988-01-01

Experiments on wall-bounded shear flows (channel flows and boundary layers) have indicated that the turbulence in the region close to the wall exhibits a characteristic intermittently formed pattern of coherent structures. For a quantitative study of coherent structures it is necessary to make use of conditional sampling. One particularly successful sampling technique is the Variable Integration Time Averaging technique (VITA) first explored by Blackwelder and Kaplan (1976). In this, an event is assumed to occur when the short time variance exceeds a certain threshold multiple of the mean square signal. The analysis presented removes some assumptions in the earlier models in that the effects of pressure and viscosity are taken into account in an approximation based on the assumption that the near-wall structures are highly elongated in the streamwise direction. The appropriateness of this is suggested by the observations but is also self consistent with the results of the model which show that the streamwise dimension of the structure grows with time, so that the approximation should improve with the age of the structure.

Cell membrane as a possible site of Fröhlich's coherent oscillations

NASA Astrophysics Data System (ADS)

Blinowska, K. J.; Lech, W.; Wittlin, A.

1985-05-01

The microwave absorption spectra of erythrocytes and their ghosts have a resonant structure and reveal a close resemblance, indicating that the cell membrane is the primary site of Fröhlich's coherent oscillations.

An extended transfer operator approach to identify separatrices in open flows

NASA Astrophysics Data System (ADS)

Lünsmann, Benedict; Kantz, Holger

2018-05-01

Vortices of coherent fluid volume are considered to have a substantial impact on transport processes in turbulent media. Yet, due to their Lagrangian nature, detecting these structures is highly nontrivial. In this respect, transfer operator approaches have been proven to provide useful tools: Approximating a possibly time-dependent flow as a discrete Markov process in space and time, information about coherent structures is contained in the operator's eigenvectors, which is usually extracted by employing clustering methods. Here, we propose an extended approach that couples surrounding filaments using "mixing boundary conditions" and focuses on the separation of the inner coherent set and embedding outer flow. The approach refrains from using unsupervised machine learning techniques such as clustering and uses physical arguments by maximizing a coherence ratio instead. We show that this technique improves the reconstruction of separatrices in stationary open flows and succeeds in finding almost-invariant sets in periodically perturbed flows.

3D coherent X-ray diffractive imaging of an Individual colloidal crystal grain

NASA Astrophysics Data System (ADS)

Shabalin, A.; Meijer, J.-M.; Sprung, M.; Petukhov, A. V.; Vartanyants, I. A.

Self-assembled colloidal crystals represent an important model system to study nucleation phenomena and solid-solid phase transitions. They are attractive for applications in photonics and sensorics. We present results of a coherent x-ray diffractive imaging experiment performed on a single colloidal crystal grain. The full three-dimensional (3D) reciprocal space map measured by an azimuthal rotational scan contained several orders of Bragg reflections together with the coherent interference signal between them. Applying the iterative phase retrieval approach, the 3D structure of the crystal grain was reconstructed and positions of individual colloidal particles were resolved. We identified an exact stacking sequence of hexagonal close-packed layers including planar and linear defects. Our results open up a breakthrough in applications of coherent x-ray diffraction for visualization of the inner 3D structure of different mesoscopic materials, such as photonic crystals. Present address: University of California - San Diego, USA.

From "Bored Witless" to "Rhetorical Nous": Teacher Orientation to Knowledge about Language and Strengthening Student Persuasive Writing

ERIC Educational Resources Information Center

Love, Kristina; Sandiford, Carmel; Macken-Horarik, Mary; Unsworth, Len

2014-01-01

We report in this paper on one aspect of a project designed to support teachers with the demands of the Language strand of the Australian Curriculum for English as this guides their development of a coherent account of knowledge about language and their implementation of this in building their students' literacy repertoires. We map the changing…

Implication of Culture: User Roles in Information Fusion for Enhanced Situational Understanding

DTIC Science & Technology

2009-07-01

situational understanding through assessment of the environment to determine a coherent state of affairs. The information is integrated with knowledge to...Implication of Culture: User Roles in Information Fusion for Enhanced Situational Understanding Erik Blasch Air Force Research Lab 2241...enhanced tacit knowledge understanding by (1) display fusion for data presentation (e.g. cultural segmentation), (2) interactive fusion to allow the

Nature of Science and Science Content Learning: The Relation between Students' Nature of Science Understanding and Their Learning about the Concept of Energy

ERIC Educational Resources Information Center

Michel, Hanno; Neumann, Irene

2016-01-01

Besides viewing knowledge about the nature of science (NOS) as important for its own value with respect to scientific literacy, an adequate understanding of NOS is expected to improve science content learning by fostering the ability to interrelate scientific concepts and, thus, coherently acquire scientific content knowledge. However, there is a…

Passive control of coherent structures in a modified backwards-facing step flow

NASA Astrophysics Data System (ADS)

Ormonde, Pedro C.; Cavalieri, André V. G.; Silva, Roberto G. A. da; Avelar, Ana C.

2018-05-01

We study a modified backwards-facing step flow, with the addition of two different plates; one is a baseline, impermeable plate and the second a perforated one. An experimental investigation is carried out for a turbulent reattaching shear layer downstream of the two plates. The proposed setup is a model configuration to study how the plate characteristics affect the separated shear layer and how turbulent kinetic energies and large-scale coherent structures are modified. Measurements show that the perforated plate changes the mean flow field, mostly by reducing the intensity of reverse flow close to the bottom wall. Disturbance amplitudes are significantly reduced up to five step heights downstream of the trailing edge of the plate, more specifically in the recirculation region. A loudspeaker is then used to introduce phase-locked, low-amplitude perturbations upstream of the plates, and phase-averaged measurements allow a quantitative study of large-scale structures in the shear-layer. The evolution of such coherent structures is evaluated in light of linear stability theory, comparing the eigenfunction of the Kelvin-Helmholtz mode to the experimental results. We observe a close match of linear-stability eigenfunctions with phase-averaged amplitudes for the two tested Strouhal numbers. The perforated plate is found to reduce the amplitude of the Kelvin-Helmholtz coherent structures in comparison to the baseline, impermeable plate, a behavior consistent with the predicted amplification trends from linear stability.

Conditional sampling technique to test the applicability of the Taylor hypothesis for the large-scale coherent structures

NASA Technical Reports Server (NTRS)

Hussain, A. K. M. F.

1980-01-01

Comparisons of the distributions of large scale structures in turbulent flow with distributions based on time dependent signals from stationary probes and the Taylor hypothesis are presented. The study investigated an area in the near field of a 7.62 cm circular air jet at a Re of 32,000, specifically having coherent structures through small-amplitude controlled excitation and stable vortex pairing in the jet column mode. Hot-wire and X-wire anemometry were employed to establish phase averaged spatial distributions of longitudinal and lateral velocities, coherent Reynolds stress and vorticity, background turbulent intensities, streamlines and pseudo-stream functions. The Taylor hypothesis was used to calculate spatial distributions of the phase-averaged properties, with results indicating that the usage of the local time-average velocity or streamwise velocity produces large distortions.

Online Knowledge-Based Model for Big Data Topic Extraction.

PubMed

Khan, Muhammad Taimoor; Durrani, Mehr; Khalid, Shehzad; Aziz, Furqan

2016-01-01

Lifelong machine learning (LML) models learn with experience maintaining a knowledge-base, without user intervention. Unlike traditional single-domain models they can easily scale up to explore big data. The existing LML models have high data dependency, consume more resources, and do not support streaming data. This paper proposes online LML model (OAMC) to support streaming data with reduced data dependency. With engineering the knowledge-base and introducing new knowledge features the learning pattern of the model is improved for data arriving in pieces. OAMC improves accuracy as topic coherence by 7% for streaming data while reducing the processing cost to half.

Machine learning research 1989-90

NASA Technical Reports Server (NTRS)

Porter, Bruce W.; Souther, Arthur

1990-01-01

Multifunctional knowledge bases offer a significant advance in artificial intelligence because they can support numerous expert tasks within a domain. As a result they amortize the costs of building a knowledge base over multiple expert systems and they reduce the brittleness of each system. Due to the inevitable size and complexity of multifunctional knowledge bases, their construction and maintenance require knowledge engineering and acquisition tools that can automatically identify interactions between new and existing knowledge. Furthermore, their use requires software for accessing those portions of the knowledge base that coherently answer questions. Considerable progress was made in developing software for building and accessing multifunctional knowledge bases. A language was developed for representing knowledge, along with software tools for editing and displaying knowledge, a machine learning program for integrating new information into existing knowledge, and a question answering system for accessing the knowledge base.

Effects of quantum coherence on work statistics

NASA Astrophysics Data System (ADS)

Xu, Bao-Ming; Zou, Jian; Guo, Li-Sha; Kong, Xiang-Mu

2018-05-01

In the conventional two-point measurement scheme of quantum thermodynamics, quantum coherence is destroyed by the first measurement. But as we know the coherence really plays an important role in the quantum thermodynamics process, and how to describe the work statistics for a quantum coherent process is still an open question. In this paper, we use the full counting statistics method to investigate the effects of quantum coherence on work statistics. First, we give a general discussion and show that for a quantum coherent process, work statistics is very different from that of the two-point measurement scheme, specifically the average work is increased or decreased and the work fluctuation can be decreased by quantum coherence, which strongly depends on the relative phase, the energy level structure, and the external protocol. Then, we concretely consider a quenched one-dimensional transverse Ising model and show that quantum coherence has a more significant influence on work statistics in the ferromagnetism regime compared with that in the paramagnetism regime, so that due to the presence of quantum coherence the work statistics can exhibit the critical phenomenon even at high temperature.

Pointing Knowledge for SPARCLE and Space-Based Doppler Wind Lidars in General

NASA Technical Reports Server (NTRS)

Emmitt, G. D.; Miller, T.; Spiers, G.

1999-01-01

The SPAce Readiness Coherent Lidar Experiment (SPARCLE) will fly on a space shuttle to demonstrate the use of a coherent Doppler wind lidar to accurately measure global tropospheric winds. To achieve the LOS (Line of Sight) accuracy goal of approx. m/s, the lidar system must be able to account for the orbiter's velocity (approx. 7750 m/s) and the rotational component of the earth's surface motion (approx. 450 m/s). For SPARCLE this requires knowledge of the attitude (roll, pitch and yaw) of the laser beam axis within an accuracy of 80 microradians. (approx. 15 arcsec). Since SPARCLE can not use a dedicated star tracker from its earth-viewing orbiter bay location, a dedicated GPS/INS (Global Positioning System/Inertial Navigation System) will be attached to the lidar instrument rack. Since even the GPS/INS has unacceptable drifts in attitude information, the SPARCLE team has developed a way to periodically scan the instrument itself to obtain less than 10 microradian (2 arcsec) attitude knowledge accuracy that can then be used to correct the GPS/INS output on a 30 minute basis.

Time evolution of coherent structures in networks of Hindmarch Rose neurons

NASA Astrophysics Data System (ADS)

Mainieri, M. S.; Erichsen, R.; Brunnet, L. G.

2005-08-01

In the regime of partial synchronization, networks of diffusively coupled Hindmarch-Rose neurons show coherent structures developing in a region of the phase space which is wider than in the correspondent single neuron. Such structures are kept, without important changes, during several bursting periods. In this work, we study the time evolution of these structures and their dynamical stability under damage. This system may model the behavior of ensembles of neurons coupled through a bidirectional gap junction or, in a broader sense, it could also account for the molecular cascades present in the formation of flash and short time memory.

Coherent control of a single nitrogen-vacancy center spin in optically levitated nanodiamond

DOE PAGES

Pettit, Robert M.; Neukirch, Levi Patrick; Zhang, Yi; ...

2017-05-12

Here, we report the first observation, to the best of our knowledge, of electron spin transients in single negatively charged nitrogen-vacancy (NV -) centers, contained within optically trapped nanodiamonds, in both atmospheric pressure and low vacuum. It is shown that, after an initial exposure to low vacuum, the trapped nanodiamonds remain at temperatures near room temperature even in low vacuum. Furthermore, the transverse coherence time of the NV - center spin, measured to be T 2=101.4 ns, is robust over the range of trapping powers considered in this study.

First demonstration and field trial on multi-user UDWDM-PON full duplex PSK-PSK with single monolithic integrated dual-output-DFB-SOA based ONUs.

PubMed

Chu, GuangYong; Maho, Anaëlle; Cano, Iván; Polo, Victor; Brenot, Romain; Debrégeas, Hélène; Prat, Josep

2016-10-15

We demonstrate a monolithically integrated dual-output DFB-SOA, and conduct the field trial on a multi-user bidirectional coherent ultradense wavelength division multiplexing-passive optical network (UDWDM-PON). To the best of our knowledge, this is the first achievement of simplified single integrated laser-based neighboring coherent optical network units (ONUs) with a 12.5 GHz channel spaced ultra-dense access network, including both downstream and upstream, taking the benefits of low footprint and low-temperature dependence.

Quantifying Motor Experience in the Infant Brain: EEG Power, Coherence, and Mu Desynchronization

PubMed Central

Gonzalez, Sandy L.; Reeb-Sutherland, Bethany C.; Nelson, Eliza L.

2016-01-01

The emergence of new motor skills, such as reaching and walking, dramatically changes how infants engage with the world socially and cognitively. Several examples of how motor experience can cascade into cognitive and social development have been documented, yet a significant knowledge gap remains in our understanding of whether these observed behavioral changes are accompanied by underlying neural changes. We propose that electroencephalography (EEG) measures such as power, coherence, and mu desynchronization are optimal tools to quantify motor experience in the infant brain. In this mini-review, we will summarize existing infant research that has separately assessed the relation between motor, cognitive, or social development with coherence, power, or mu desynchronization. We will discuss how the reviewed neural changes seen in seemingly separate developmental domains may be linked based on existing behavioral evidence. We will further propose that power, coherence, and mu desynchronization be used in research exploring the links between motor experience and cognitive and social development. PMID:26925022

Highly coherent octave-spanning supercontinuum generation in CS2-filled photonic crystal fiber with strong slow nonlinearity

NASA Astrophysics Data System (ADS)

Wang, Liyun; Yuan, Jinhui; Wang, Kuiru; Kang, Zhe; Sang, Xinzhu; Yu, Chongxiu; Yan, Binbin

2016-11-01

In this paper, the supercontinuum (SC) generation in a carbon disulfide (CS2)-filled photonic crystal fiber (PCF) with strong slow nonlinearity is investigated. When the PCF is pumped at 1.55 μm in the anomalous dispersion region, we obtain highly coherent SC spanning from 0.99 to 2.32 μm, at -40 dB level. Moreover, the influences of the slow nonlinearity, the input pulse width, the pulse peak power, the fiber length, and the temperature on the supercontinuum generation (SCG) are studied. The role of the slow nonlinearity in enhancing the coherence of SC is proved. To our best knowledge, this is the first demonstration on generating the octave-spanning SC with high coherence using the slow nonlinearity of CS2. CS2 is a material that has high nonlinearity coefficient and well transparency in infrared. What's more, the slow nonlinearity is very strong in this material.

Reversing expectations during discourse comprehension

PubMed Central

Xiang, Ming; Kuperberg, Gina

2014-01-01

In two ERP experiments, we asked whether comprehenders used the concessive connective, even so, to predict upcoming events. Participants read coherent and incoherent scenarios, with and without even so, e.g. “Elizabeth had a history exam on Monday. She took the test and aced/failed it. (Even so), she went home and celebrated wildly.”, as they rated coherence (Experiment 1) or simply answered intermittent comprehension questions (Experiment 2). The semantic function of even so was used to reverse real-world knowledge predictions, leading to an attenuated N400 to coherent versus incoherent target words (“celebrated”). Moreover, its pragmatic communicative function enhanced predictive processing, leading to more N400 attenuation to coherent targets in scenarios with than without even so. This benefit however, did not come for free: the detection of failed event predictions triggered a later posterior positivity and/or an anterior negativity effect, and costs of maintaining alternative likelihood relations manifest as a sustained negativity effect on sentence-final words. PMID:25914891

Pragmatic competence of children with autism spectrum disorder. Impact of theory of mind, verbal working memory, ADHD symptoms, and structural language.

PubMed

Baixauli-Fortea, Inmaculada; Miranda Casas, Ana; Berenguer-Forner, Carmen; Colomer-Diago, Carla; Roselló-Miranda, Belén

2017-11-21

The primary aim of this study is to increase the existing knowledge about the pragmatic skills of children with autism spectrum disorders (ASD). Specifically, the study has two objectives. The first is to provide a profile of characteristics based on The Children's Communication Checklist (CCC-2) pragmatics scales (inappropriate initiation, stereotyped language, use of context, nonverbal communication, and general pragmatics) and narrative task indicators. To this end, children with ASD will be compared to children with typical development (TD), controlling the effects of sex and structural language (speech, syntax, semantics, coherence). The second objective is to analyze whether theory of mind (ToM), verbal working memory, ADHD symptoms, and structural language can predict pragmatic competence in children with ASD without intellectual disability (ID). The results showed worse performance in the group with ASD on the majority of the pragmatic aspects evaluated. In addition, the application of ToM skills and structural language were significant predictors of the pragmatic skills of the children with ASD. These findings reinforce the importance of focusing intervention programs on mentalist abilities through experiences in real social scenarios, along with strengthening structural language components.

Optical threshold secret sharing scheme based on basic vector operations and coherence superposition

NASA Astrophysics Data System (ADS)

Deng, Xiaopeng; Wen, Wei; Mi, Xianwu; Long, Xuewen

2015-04-01

We propose, to our knowledge for the first time, a simple optical algorithm for secret image sharing with the (2,n) threshold scheme based on basic vector operations and coherence superposition. The secret image to be shared is firstly divided into n shadow images by use of basic vector operations. In the reconstruction stage, the secret image can be retrieved by recording the intensity of the coherence superposition of any two shadow images. Compared with the published encryption techniques which focus narrowly on information encryption, the proposed method can realize information encryption as well as secret sharing, which further ensures the safety and integrality of the secret information and prevents power from being kept centralized and abused. The feasibility and effectiveness of the proposed method are demonstrated by numerical results.

Studies of electrode structures and dynamics using coherent X-ray scattering and imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

You, H.; Liu, Y.; Ulvestad, A.

2017-08-01

Electrochemical systems studied in situ with advanced surface X-ray scattering techniques are reviewed. The electrochemical systems covered include interfaces of single-crystals and nanocrystals with respect to surface modification, aqueous dissolution, surface reconstruction, and electrochemical double layers. An emphasis will be given on recent results by coherent X-ray techniques such as X-ray photon correlation spectroscopy, Bragg coherent diffraction imaging, and surface ptychography.

Coherency strain engineered decomposition of unstable multilayer alloys for improved thermal stability

NASA Astrophysics Data System (ADS)

Forsén, R.; Ghafoor, N.; Odén, M.

2013-12-01

A concept to improve hardness and thermal stability of unstable multilayer alloys is presented based on control of the coherency strain such that the driving force for decomposition is favorably altered. Cathodic arc evaporated cubic TiCrAlN/Ti1-xCrxN multilayer coatings are used as demonstrators. Upon annealing, the coatings undergo spinodal decomposition into nanometer-sized coherent Ti- and Al-rich cubic domains which is affected by the coherency strain. In addition, the growth of the domains is restricted by the surrounding TiCrN layer compared to a non-layered TiCrAlN coating which together results in an improved thermal stability of the cubic structure. A significant hardness increase is seen during decomposition for the case with high coherency strain while a low coherency strain results in a hardness decrease for high annealing temperatures. The metal diffusion paths during the domain coarsening are affected by strain which in turn is controlled by the Cr-content (x) in the Ti1-xCrxN layers. For x = 0 the diffusion occurs both parallel and perpendicular to the growth direction but for x > =0.9 the diffusion occurs predominantly parallel to the growth direction. Altogether this study shows a structural tool to alter and fine-tune high temperature properties of multicomponent materials.

Minimum uncertainty and squeezing in diffusion processes and stochastic quantization

NASA Technical Reports Server (NTRS)

Demartino, S.; Desiena, S.; Illuminati, Fabrizo; Vitiello, Giuseppe

1994-01-01

We show that uncertainty relations, as well as minimum uncertainty coherent and squeezed states, are structural properties for diffusion processes. Through Nelson stochastic quantization we derive the stochastic image of the quantum mechanical coherent and squeezed states.

Evaluation of the Environmentalist Dimension of Ecotourism at the Dadia Forest Reserve (Greece)

NASA Astrophysics Data System (ADS)

Hovardas, Tasos; Poirazidis, Kostas

2006-11-01

Environmental education and financial support of nature conservation are considered among the primary components of the environmentalist dimension of ecotourism. The potential of environmental education calls for enhancing visitor environmental knowledge and prompting change of visitor behavior. The present study addressed the evaluation of the environmentalist dimension of ecotourism in the Dadia Forest Reserve. The first objective of the research was to study the influence of variables determined prior to the visit, namely, visitor and visit characteristics, visitor environmental information sources, visitor pro-environmental behavior, and visitation goals, on variables determined during the visit, that is, visitor participation in and satisfaction from ecotourism activities. The second objective was to study the effect of selected variables on visitor knowledge and behavior intentions. Visitor participation in and satisfaction from ecotourism activities were primarily controlled by visit characteristics. Levels of visitor knowledge were quite satisfactory; however, coherence among knowledge items was rather loose. On the other hand, behavior intention items revealed the highest possible degree of coherence, which should be attributed to the pervasive influence of visitor satisfaction from watching birds at the Bird Observatory within the Dadia Forest Reserve. Ecotourism activities, during which the main part of environmental knowledge was offered, exerted no effect on visitor knowledge; all the same, they significantly influenced visitor behavior intentions. Overall, visitor behavior intentions revealed a considerable potential of financing environmental protection and providing voluntary work in the frame of the environmental management of the Dadia Forest Reserve.

Evaluation of the environmentalist dimension of ecotourism at the Dadia Forest Reserve (Greece).

PubMed

Hovardas, Tasos; Poirazidis, Kostas

2006-11-01

Environmental education and financial support of nature conservation are considered among the primary components of the environmentalist dimension of ecotourism. The potential of environmental education calls for enhancing visitor environmental knowledge and prompting change of visitor behavior. The present study addressed the evaluation of the environmentalist dimension of ecotourism in the Dadia Forest Reserve. The first objective of the research was to study the influence of variables determined prior to the visit, namely, visitor and visit characteristics, visitor environmental information sources, visitor pro-environmental behavior, and visitation goals, on variables determined during the visit, that is, visitor participation in and satisfaction from ecotourism activities. The second objective was to study the effect of selected variables on visitor knowledge and behavior intentions. Visitor participation in and satisfaction from ecotourism activities were primarily controlled by visit characteristics. Levels of visitor knowledge were quite satisfactory; however, coherence among knowledge items was rather loose. On the other hand, behavior intention items revealed the highest possible degree of coherence, which should be attributed to the pervasive influence of visitor satisfaction from watching birds at the Bird Observatory within the Dadia Forest Reserve. Ecotourism activities, during which the main part of environmental knowledge was offered, exerted no effect on visitor knowledge; all the same, they significantly influenced visitor behavior intentions. Overall, visitor behavior intentions revealed a considerable potential of financing environmental protection and providing voluntary work in the frame of the environmental management of the Dadia Forest Reserve.

An algorithm for improving the quality of structural images of turbid media in endoscopic optical coherence tomography

NASA Astrophysics Data System (ADS)

Potlov, A. Yu.; Frolov, S. V.; Proskurin, S. G.

2018-04-01

High-quality OCT structural images reconstruction algorithm for endoscopic optical coherence tomography of biological tissue is described. The key features of the presented algorithm are: (1) raster scanning and averaging of adjacent Ascans and pixels; (2) speckle level minimization. The described algorithm can be used in the gastroenterology, urology, gynecology, otorhinolaryngology for mucous membranes and skin diagnostics in vivo and in situ.

Illness perceptions of fatigue and the association with sense of coherence and stress in patients one year after myocardial infarction.

PubMed

Alsén, Pia; Eriksson, Monica

2016-02-01

To explore the associations between illness perceptions of fatigue, sense of coherence and stress in patients one year after myocardial infarction. Post-myocardial infarction fatigue is a stressful symptom that is difficult to cope with. Patients' illness perceptions of fatigue guide professionals in predicting how individuals will respond emotionally and cognitively to symptoms. Individuals' sense of coherence can be seen as a coping resource in managing stressors. A cross-sectional study design was used. One year post-myocardial infarction, a total of 74 patients still experiencing fatigue completed four questionnaires: the Multidimensional Fatigue Scale Inventory-20, the Brief Illness Perception Questionnaire, the Sense of Coherence scale (sense of coherence-13) and a single-item measure of stress symptoms. Descriptive statistics, correlations and stepwise regression analysis were carried out. Strong negative associations were found between illness perceptions of fatigue, sense of coherence and stress. Sense of coherence has an impact on illness perceptions of fatigue. Of the dimensions of sense of coherence, comprehensibility seemed to play the greatest role in explaining illness perceptions of fatigue one year after myocardial infarction. To strengthen patients' coping resources, health-care professionals should create opportunities for patients to gain individual-level knowledge that allows them to distinguish between common fatigue symptoms and warning signs for myocardial infarction. There is a need to improve strategies for coping with fatigue. It is also essential to identify patients with fatigue after myocardial infarction, as they need explanations for their symptoms and extra support. © 2016 John Wiley & Sons Ltd.

Pathogenic changes of dispersion and contrast of coherent images of biotissues

NASA Astrophysics Data System (ADS)

Pishak, Olga V.

2002-02-01

The paper presents the results of polarization-correlation investigation of multifractal collagen structure of physiologically normal and pathologically changed tissues of women's reproductive sphere and of skin. The technique of polarization selection of coherent biotissues' images with the following determination of their autocorrelation functions and spectral densities is suggested. The correlation-optical criteria of early diagnostics of pathological changes' appearance of myometry (forming of the germ of fibromyoma) and of skin(psoriasis) are determined. The suggested paper is directed to investigation of the possibilities of pathological changes of biotissues' morphological structure by means of determining the polarizationally filtered autocorrelation functions (ACF) and corresponding spectral densities of their coherent images.

Beyond crystallography: Diffractive imaging using coherent x-ray light sources

DOE Office of Scientific and Technical Information (OSTI.GOV)

Miao, J.; Ishikawa, T.; Robinson, I. K.

X-ray crystallography has been central to the development of many fields of science over the past century. It has now matured to a point that as long as good-quality crystals are available, their atomic structure can be routinely determined in three dimensions. However, many samples in physics, chemistry, materials science, nanoscience, geology, and biology are noncrystalline, and thus their three-dimensional structures are not accessible by traditional x-ray crystallography. Overcoming this hurdle has required the development of new coherent imaging methods to harness new coherent x-ray light sources. Here we review the revolutionary advances that are transforming x-ray sources and imagingmore » in the 21st century.« less

Air motions inside dome room of Big Telescope Alt-azimuth at Special Astrophysical Observatory RAS. Numerical solutions of Navier-Stokes equations

NASA Astrophysics Data System (ADS)

Nosov, V. V.; Lukin, V. P.; Nosov, E. V.; Torgaev, A. V.

2017-11-01

The structure of air turbulent motion inside the closed dome room of Big Telescope Alt-azimuth at Special Astrophysical Observatory of the Russian Academy of Sciences (RAS) has been experimentally and theoretically studied. Theoretical results have been reached by numerical solving of boundary value problem for Navier-Stokes equations. Solitary large vortices (coherent structures, topological solitons) are observed indoors. Coherent breakdown of these vortices leads to the coherent turbulence. In the case of identical boundary conditions the pattern of air motions as a result of the simulation and the pattern, registered experimentally using the compact portable ultrasonic weather station, are practically the same.

Incoherent Diffractive Imaging via Intensity Correlations of Hard X Rays

NASA Astrophysics Data System (ADS)

Classen, Anton; Ayyer, Kartik; Chapman, Henry N.; Röhlsberger, Ralf; von Zanthier, Joachim

2017-08-01

Established x-ray diffraction methods allow for high-resolution structure determination of crystals, crystallized protein structures, or even single molecules. While these techniques rely on coherent scattering, incoherent processes like fluorescence emission—often the predominant scattering mechanism—are generally considered detrimental for imaging applications. Here, we show that intensity correlations of incoherently scattered x-ray radiation can be used to image the full 3D arrangement of the scattering atoms with significantly higher resolution compared to conventional coherent diffraction imaging and crystallography, including additional three-dimensional information in Fourier space for a single sample orientation. We present a number of properties of incoherent diffractive imaging that are conceptually superior to those of coherent methods.

Ultrafast infrared spectroscopy reveals water-mediated coherent dynamics in an enzyme active site.

PubMed

Adamczyk, Katrin; Simpson, Niall; Greetham, Gregory M; Gumiero, Andrea; Walsh, Martin A; Towrie, Michael; Parker, Anthony W; Hunt, Neil T

2015-01-01

Understanding the impact of fast dynamics upon the chemical processes occurring within the active sites of proteins and enzymes is a key challenge that continues to attract significant interest, though direct experimental insight in the solution phase remains sparse. Similar gaps in our knowledge exist in understanding the role played by water, either as a solvent or as a structural/dynamic component of the active site. In order to investigate further the potential biological roles of water, we have employed ultrafast multidimensional infrared spectroscopy experiments that directly probe the structural and vibrational dynamics of NO bound to the ferric haem of the catalase enzyme from Corynebacterium glutamicum in both H 2 O and D 2 O. Despite catalases having what is believed to be a solvent-inaccessible active site, an isotopic dependence of the spectral diffusion and vibrational lifetime parameters of the NO stretching vibration are observed, indicating that water molecules interact directly with the haem ligand. Furthermore, IR pump-probe data feature oscillations originating from the preparation of a coherent superposition of low-frequency vibrational modes in the active site of catalase that are coupled to the haem ligand stretching vibration. Comparisons with an exemplar of the closely-related peroxidase enzyme family shows that they too exhibit solvent-dependent active-site dynamics, supporting the presence of interactions between the haem ligand and water molecules in the active sites of both catalases and peroxidases that may be linked to proton transfer events leading to the formation of the ferryl intermediate Compound I. In addition, a strong, water-mediated, hydrogen bonding structure is suggested to occur in catalase that is not replicated in peroxidase; an observation that may shed light on the origins of the different functions of the two enzymes.

From neurons to epidemics: How trophic coherence affects spreading processes.

PubMed

Klaise, Janis; Johnson, Samuel

2016-06-01

Trophic coherence, a measure of the extent to which the nodes of a directed network are organised in levels, has recently been shown to be closely related to many structural and dynamical aspects of complex systems, including graph eigenspectra, the prevalence or absence of feedback cycles, and linear stability. Furthermore, non-trivial trophic structures have been observed in networks of neurons, species, genes, metabolites, cellular signalling, concatenated words, P2P users, and world trade. Here, we consider two simple yet apparently quite different dynamical models-one a susceptible-infected-susceptible epidemic model adapted to include complex contagion and the other an Amari-Hopfield neural network-and show that in both cases the related spreading processes are modulated in similar ways by the trophic coherence of the underlying networks. To do this, we propose a network assembly model which can generate structures with tunable trophic coherence, limiting in either perfectly stratified networks or random graphs. We find that trophic coherence can exert a qualitative change in spreading behaviour, determining whether a pulse of activity will percolate through the entire network or remain confined to a subset of nodes, and whether such activity will quickly die out or endure indefinitely. These results could be important for our understanding of phenomena such as epidemics, rumours, shocks to ecosystems, neuronal avalanches, and many other spreading processes.

From neurons to epidemics: How trophic coherence affects spreading processes

NASA Astrophysics Data System (ADS)

Klaise, Janis; Johnson, Samuel

2016-06-01

Trophic coherence, a measure of the extent to which the nodes of a directed network are organised in levels, has recently been shown to be closely related to many structural and dynamical aspects of complex systems, including graph eigenspectra, the prevalence or absence of feedback cycles, and linear stability. Furthermore, non-trivial trophic structures have been observed in networks of neurons, species, genes, metabolites, cellular signalling, concatenated words, P2P users, and world trade. Here, we consider two simple yet apparently quite different dynamical models—one a susceptible-infected-susceptible epidemic model adapted to include complex contagion and the other an Amari-Hopfield neural network—and show that in both cases the related spreading processes are modulated in similar ways by the trophic coherence of the underlying networks. To do this, we propose a network assembly model which can generate structures with tunable trophic coherence, limiting in either perfectly stratified networks or random graphs. We find that trophic coherence can exert a qualitative change in spreading behaviour, determining whether a pulse of activity will percolate through the entire network or remain confined to a subset of nodes, and whether such activity will quickly die out or endure indefinitely. These results could be important for our understanding of phenomena such as epidemics, rumours, shocks to ecosystems, neuronal avalanches, and many other spreading processes.

Paradigms, Exemplars and Social Change

ERIC Educational Resources Information Center

Lawson, Hal A.

2009-01-01

Researchers' social-cultural organization influences the scope, quality, quantity, coherence, dissemination, utilization and impact of research-based, theoretically sound knowledge. Five concepts--paradigm, exemplar, segment, network and gatekeeper--are salient to research on researchers' organization. Autobiographical reflections signal these…

Coherent Structures in Magnetic Confinement Systems

NASA Astrophysics Data System (ADS)

Horton, W.

2006-04-01

Coherent structures are long-lived, nonlinear localized solutions of the selfconsistient plasma-electromagnetic field equations. They contain appreciable energy density and control various transport and magnetic reconnection processes in plasmas. These structures are self-binding from the nonlinearity balancing, or overcoming, the wave dispersion of energy in smaller amplitude structures. The structures evolve out of the nonlinear interactions in various instabilities or external driving fields. The theoretical basis for these structures are reviewed giving examples from various plasma instabilities and their reduced descriptions from the appropriate partial differential equations. A classic example from drift waves is the formation of monopole, dipole and tripolar vortex structures which have been created in both laboratory and simulation experiments. For vortices, the long life-time and nonlinear interactions of the structures can be understood with conservation laws of angular momentum given by the vorticity field associated with dynamics. Other morphologies include mushrooms, Kelvin-Helmholtz vorticity roll-up, streamers and blobs. We show simulation movies of various examples drawn from ETG modes in NSTX, H-mode like shear flow layers in LAPD and the vortices measured with soft x-ray tomography in the GAMMA 10 tandem mirror. Coherent current-sheet structures form in driven magnetic reconnection layers and control the rate of transformation of magnetic energy to flow and thermal energy.

Coherent Terahertz Radiation from Multiple Electron Beams Excitation within a Plasmonic Crystal-like structure.

PubMed

Zhang, Yaxin; Zhou, Yucong; Gang, Yin; Jiang, Guili; Yang, Ziqiang

2017-01-23

Coherent terahertz radiation from multiple electron beams excitation within a plasmonic crystal-like structure (a three-dimensional holes array) which is composed of multiple stacked layers with 3 × 3 subwavelength holes array has been proposed in this paper. It has been found that in the structure the electromagnetic fields in each hole can be coupled with one another to construct a composite mode with strong field intensity. Therefore, the multiple electron beams injection can excite and efficiently interact with such mode. Meanwhile, the coupling among the electron beams is taken place during the interaction so that a very strong coherent terahertz radiation with high electron conversion efficiency can be generated. Furthermore, due to the coupling, the starting current density of this mechanism is much lower than that of traditional electron beam-driven terahertz sources. This multi-beam radiation system may provide a favorable way to combine photonics structure with electronics excitation to generate middle, high power terahertz radiation.

Coherent Terahertz Radiation from Multiple Electron Beams Excitation within a Plasmonic Crystal-like structure

PubMed Central

Zhang, Yaxin; Zhou, Yucong; Gang, Yin; Jiang, Guili; Yang, Ziqiang

2017-01-01

Coherent terahertz radiation from multiple electron beams excitation within a plasmonic crystal-like structure (a three-dimensional holes array) which is composed of multiple stacked layers with 3 × 3 subwavelength holes array has been proposed in this paper. It has been found that in the structure the electromagnetic fields in each hole can be coupled with one another to construct a composite mode with strong field intensity. Therefore, the multiple electron beams injection can excite and efficiently interact with such mode. Meanwhile, the coupling among the electron beams is taken place during the interaction so that a very strong coherent terahertz radiation with high electron conversion efficiency can be generated. Furthermore, due to the coupling, the starting current density of this mechanism is much lower than that of traditional electron beam-driven terahertz sources. This multi-beam radiation system may provide a favorable way to combine photonics structure with electronics excitation to generate middle, high power terahertz radiation. PMID:28112234

Aligned and Unaligned Coherence: A New Diagnostic Tool

NASA Technical Reports Server (NTRS)

Miles, Jeffrey Hilton

2006-01-01

The study of combustion noise from turbofan engines has become important again as the noise from other sources like the fan and jet are reduced. A method has been developed to help identify combustion noise spectra using an aligned and unaligned coherence technique. When used with the well known three signal coherent power method and coherent power method it provides new information by separating tonal information from random process information. Examples are presented showing the underlying tonal structure which is buried under broadband noise and jet noise. The method is applied to data from a Pratt and Whitney PW4098 turbofan engine.

Coherent multilayer crystals and method of making

DOEpatents

Schuller, Ivan K.; Falco, Charles M.

1984-01-01

A new material consisting of a multilayer crystalline structure which is coherent perpendicular to the layers and where each layer is composed of a single crystalline element. The individual layers may vary from 2.ANG. to 100.ANG. or more in thickness.

Toward a structural understanding of turbulent drag reduction: nonlinear coherent states in viscoelastic shear flows.

PubMed

Stone, Philip A; Waleffe, Fabian; Graham, Michael D

2002-11-11

Nontrivial steady flows have recently been found that capture the main structures of the turbulent buffer layer. We study the effects of polymer addition on these "exact coherent states" (ECS) in plane Couette flow. Despite the simplicity of the ECS flows, these effects closely mirror those observed experimentally: Structures shift to larger length scales, wall-normal fluctuations are suppressed while streamwise ones are enhanced, and drag is reduced. The mechanism underlying these effects is elucidated. These results suggest that the ECS are closely related to buffer layer turbulence.

Evidence and Clinical Trials.

NASA Astrophysics Data System (ADS)

Goodman, Steven N.

1989-11-01

This dissertation explores the use of a mathematical measure of statistical evidence, the log likelihood ratio, in clinical trials. The methods and thinking behind the use of an evidential measure are contrasted with traditional methods of analyzing data, which depend primarily on a p-value as an estimate of the statistical strength of an observed data pattern. It is contended that neither the behavioral dictates of Neyman-Pearson hypothesis testing methods, nor the coherency dictates of Bayesian methods are realistic models on which to base inference. The use of the likelihood alone is applied to four aspects of trial design or conduct: the calculation of sample size, the monitoring of data, testing for the equivalence of two treatments, and meta-analysis--the combining of results from different trials. Finally, a more general model of statistical inference, using belief functions, is used to see if it is possible to separate the assessment of evidence from our background knowledge. It is shown that traditional and Bayesian methods can be modeled as two ends of a continuum of structured background knowledge, methods which summarize evidence at the point of maximum likelihood assuming no structure, and Bayesian methods assuming complete knowledge. Both schools are seen to be missing a concept of ignorance- -uncommitted belief. This concept provides the key to understanding the problem of sampling to a foregone conclusion and the role of frequency properties in statistical inference. The conclusion is that statistical evidence cannot be defined independently of background knowledge, and that frequency properties of an estimator are an indirect measure of uncommitted belief. Several likelihood summaries need to be used in clinical trials, with the quantitative disparity between summaries being an indirect measure of our ignorance. This conclusion is linked with parallel ideas in the philosophy of science and cognitive psychology.

Large-Eddy Simulation of Coherent Flow Structures within a Cubical Canopy

NASA Astrophysics Data System (ADS)

Inagaki, Atsushi; Castillo, Marieta Cristina L.; Yamashita, Yoshimi; Kanda, Manabu; Takimoto, Hiroshi

2012-02-01

Instantaneous flow structures "within" a cubical canopy are investigated via large-eddy simulation. The main topics of interest are, (1) large-scale coherent flow structures within a cubical canopy, (2) how the structures are coupled with the turbulent organized structures (TOS) above them, and (3) the classification and quantification of representative instantaneous flow patterns within a street canyon in relation to the coherent structures. We use a large numerical domain (2,560 m × 2,560 m × 1,710 m) with a fine spatial resolution (2.5 m), thereby simulating a complete daytime atmospheric boundary layer (ABL), as well as explicitly resolving a regular array of cubes (40 m in height) at the surface. A typical urban ABL is numerically modelled. In this situation, the constant heat supply from roof and floor surfaces sustains a convective mixed layer as a whole, but strong wind shear near the canopy top maintains the surface layer nearly neutral. The results reveal large coherent structures in both the velocity and temperature fields "within" the canopy layer. These structures are much larger than the cubes, and their shapes and locations are shown to be closely related to the TOS above them. We classify the instantaneous flow patterns in a cavity, specifically focusing on two characteristic flow patterns: flushing and cavity-eddy events. Flushing indicates a strong upward motion, while a cavity eddy is characterized by a dominant vortical motion within a single cavity. Flushing is clearly correlated with the TOS above, occurring frequently beneath low-momentum streaks. The instantaneous momentum and heat transport within and above a cavity due to flushing and cavity-eddy events are also quantified.

Using domain knowledge and domain-inspired discourse model for coreference resolution for clinical narratives

PubMed Central

Roth, Dan

2013-01-01

Objective This paper presents a coreference resolution system for clinical narratives. Coreference resolution aims at clustering all mentions in a single document to coherent entities. Materials and methods A knowledge-intensive approach for coreference resolution is employed. The domain knowledge used includes several domain-specific lists, a knowledge intensive mention parsing, and task informed discourse model. Mention parsing allows us to abstract over the surface form of the mention and represent each mention using a higher-level representation, which we call the mention's semantic representation (SR). SR reduces the mention to a standard form and hence provides better support for comparing and matching. Existing coreference resolution systems tend to ignore discourse aspects and rely heavily on lexical and structural cues in the text. The authors break from this tradition and present a discourse model for “person” type mentions in clinical narratives, which greatly simplifies the coreference resolution. Results This system was evaluated on four different datasets which were made available in the 2011 i2b2/VA coreference challenge. The unweighted average of F1 scores (over B-cubed, MUC and CEAF) varied from 84.2% to 88.1%. These experiments show that domain knowledge is effective for different mention types for all the datasets. Discussion Error analysis shows that most of the recall errors made by the system can be handled by further addition of domain knowledge. The precision errors, on the other hand, are more subtle and indicate the need to understand the relations in which mentions participate for building a robust coreference system. Conclusion This paper presents an approach that makes an extensive use of domain knowledge to significantly improve coreference resolution. The authors state that their system and the knowledge sources developed will be made publicly available. PMID:22781192

Ketamine-Induced Oscillations in the Motor Circuit of the Rat Basal Ganglia

PubMed Central

Alegre, Manuel; Pérez-Alcázar, Marta; Iriarte, Jorge; Artieda, Julio

2011-01-01

Oscillatory activity can be widely recorded in the cortex and basal ganglia. This activity may play a role not only in the physiology of movement, perception and cognition, but also in the pathophysiology of psychiatric and neurological diseases like schizophrenia or Parkinson's disease. Ketamine administration has been shown to cause an increase in gamma activity in cortical and subcortical structures, and an increase in 150 Hz oscillations in the nucleus accumbens in healthy rats, together with hyperlocomotion. We recorded local field potentials from motor cortex, caudate-putamen (CPU), substantia nigra pars reticulata (SNr) and subthalamic nucleus (STN) in 20 awake rats before and after the administration of ketamine at three different subanesthetic doses (10, 25 and 50 mg/Kg), and saline as control condition. Motor behavior was semiautomatically quantified by custom-made software specifically developed for this setting. Ketamine induced coherent oscillations in low gamma (50 Hz), high gamma (80 Hz) and high frequency (HFO, 150 Hz) bands, with different behavior in the four structures studied. While oscillatory activity at these three peaks was widespread across all structures, interactions showed a different pattern for each frequency band. Imaginary coherence at 150 Hz was maximum between motor cortex and the different basal ganglia nuclei, while low gamma coherence connected motor cortex with CPU and high gamma coherence was more constrained to the basal ganglia nuclei. Power at three bands correlated with the motor activity of the animal, but only coherence values in the HFO and high gamma range correlated with movement. Interactions in the low gamma band did not show a direct relationship to movement. These results suggest that the motor effects of ketamine administration may be primarily mediated by the induction of coherent widespread high-frequency activity in the motor circuit of the basal ganglia, together with a frequency-specific pattern of connectivity among the structures analyzed. PMID:21829443

Intermittent bilateral coherence in physiological and essential hand tremor.

PubMed

Chakraborty, Soma; Kopecká, Jana; Šprdlík, Otakar; Hoskovcová, Martina; Ulmanová, Olga; Růžička, Evžen; Zapotocky, Martin

2017-04-01

To investigate the prevalence and the temporal structure of bilateral coherence in physiological (PT) and essential (ET) hand tremor. Triaxial accelerometric recordings from both hands in 30 healthy subjects and 34 ET patients were analyzed using spectral coherence and wavelet coherence methods. In 12 additional healthy subjects, the relation between the hand tremor and the chest wall acceleration was evaluated using partial coherence analysis. The majority of both PT and ET subjects displayed significant bilateral coherence. While in PT, bilateral coherence was most frequently found in resting hand position (97% of subjects), in ET the prevalence was comparable for resting (54%) and postural (49%-57%) positions. In both PT and ET, epochs of strong coherence lasting several to a dozen seconds were separated by intervals of insignificant coherence. In PT, bilateral coherence at the main tremor frequency (8-12Hz) was coupled with the ballistocardiac rhythm. The oscillations of the two hands are intermittently synchronized in both PT and ET. We propose that in postural PT, bilateral coherence at the main tremor frequency arises from transient simultaneous entrainment of the left and right hand oscillations to ballistocardiac forcing. Bilateral coherence of hand kinematics provides a sensitive measure of synchronizing influences on the left and right tremor oscillators. Copyright © 2017 International Federation of Clinical Neurophysiology. Published by Elsevier B.V. All rights reserved.

Coherent Optical Control of Electronic Excitations in Wide-Band-Gap Semiconductor Structures

DTIC Science & Technology

2015-05-01

ABSTRACT The main objective of this research is to study coherent quantum effects, such as Rabi oscillations in optical spectra of wide- band-gap...field corresponds to the rotation of the B vector about the pseudo field vector, Ω, with components determined by the effective Rabi frequency ( )e...to examine coherent quantum effects, such as Rabi oscillations and quantum entanglement in optical spectra of wide-band-gap materials, and to

Coherent vs Incoherent Emission from Semiconductor Structures after Resonant Femtosecond Excitation

NASA Astrophysics Data System (ADS)

Gurioli, Massimo; Bogani, Franco; Ceccherini, Simone; Colocci, Marcello

1997-04-01

We show that an interferometric correlation measurement with fs time resolution provides an unambiguous discrimination between coherent and incoherent emission after resonant femtosecond excitation. The experiment directly probes the most important difference between the two emissions, that is, the phase correlation with the excitation pulse. The comparison with cw frequency resolved measurements demonstrates that the relationship between coherent and incoherent emission is similar under femtosecond and steady-state excitation.

Description of quantum coherence in thermodynamic processes requires constraints beyond free energy.

PubMed

Lostaglio, Matteo; Jennings, David; Rudolph, Terry

2015-03-10

Recent studies have developed fundamental limitations on nanoscale thermodynamics, in terms of a set of independent free energy relations. Here we show that free energy relations cannot properly describe quantum coherence in thermodynamic processes. By casting time-asymmetry as a quantifiable, fundamental resource of a quantum state, we arrive at an additional, independent set of thermodynamic constraints that naturally extend the existing ones. These asymmetry relations reveal that the traditional Szilárd engine argument does not extend automatically to quantum coherences, but instead only relational coherences in a multipartite scenario can contribute to thermodynamic work. We find that coherence transformations are always irreversible. Our results also reveal additional structural parallels between thermodynamics and the theory of entanglement.

Description of quantum coherence in thermodynamic processes requires constraints beyond free energy

NASA Astrophysics Data System (ADS)

Lostaglio, Matteo; Jennings, David; Rudolph, Terry

2015-03-01

Recent studies have developed fundamental limitations on nanoscale thermodynamics, in terms of a set of independent free energy relations. Here we show that free energy relations cannot properly describe quantum coherence in thermodynamic processes. By casting time-asymmetry as a quantifiable, fundamental resource of a quantum state, we arrive at an additional, independent set of thermodynamic constraints that naturally extend the existing ones. These asymmetry relations reveal that the traditional Szilárd engine argument does not extend automatically to quantum coherences, but instead only relational coherences in a multipartite scenario can contribute to thermodynamic work. We find that coherence transformations are always irreversible. Our results also reveal additional structural parallels between thermodynamics and the theory of entanglement.

Coherence Evolution and Transfer Supplemented by Sender's Initial-State Restoring

NASA Astrophysics Data System (ADS)

Fel'dman, E. B.; Zenchuk, A. I.

2017-12-01

The evolution of quantum coherences comes with a set of conservation laws provided that the Hamiltonian governing this evolution conserves the spin-excitation number. At that, coherences do not intertwist during the evolution. Using the transmission line and the receiver in the initial ground state we can transfer the coherences to the receiver without interaction between them, although the matrix elements contributing to each particular coherence intertwist in the receiver's state. Therefore we propose a tool based on the unitary transformation at the receiver side to untwist these elements and thus restore (at least partially) the structure of the sender's initial density matrix. A communication line with two-qubit sender and receiver is considered as an example of implementation of this technique.

Description of quantum coherence in thermodynamic processes requires constraints beyond free energy

PubMed Central

Lostaglio, Matteo; Jennings, David; Rudolph, Terry

2015-01-01

Recent studies have developed fundamental limitations on nanoscale thermodynamics, in terms of a set of independent free energy relations. Here we show that free energy relations cannot properly describe quantum coherence in thermodynamic processes. By casting time-asymmetry as a quantifiable, fundamental resource of a quantum state, we arrive at an additional, independent set of thermodynamic constraints that naturally extend the existing ones. These asymmetry relations reveal that the traditional Szilárd engine argument does not extend automatically to quantum coherences, but instead only relational coherences in a multipartite scenario can contribute to thermodynamic work. We find that coherence transformations are always irreversible. Our results also reveal additional structural parallels between thermodynamics and the theory of entanglement. PMID:25754774

Characterization of human scalp hairs by optical low-coherence reflectometry

NASA Astrophysics Data System (ADS)

Wang, X. J.; Milner, T. E.; Dhond, R. P.; Sorin, W. V.; Newton, S. A.; Nelson, J. S.

1995-03-01

Optical low-coherence reflectometry is used to investigate the internal structure and optical properties of human scalp hair. Regardless of hair color, the refractive index of the cortical region remains within the range of 1.56-1.59. The amplitude of the backscattered infrared light coupled into different-colored hair confirms the relative melanin content. Discontinuities in the refractive index permit identification of distinct structural layers within the hair shaft.

Imaging fully hydrated whole cells by coherent x-ray diffraction microscopy.

PubMed

Nam, Daewoong; Park, Jaehyun; Gallagher-Jones, Marcus; Kim, Sangsoo; Kim, Sunam; Kohmura, Yoshiki; Naitow, Hisashi; Kunishima, Naoki; Yoshida, Takashi; Ishikawa, Tetsuya; Song, Changyong

2013-03-01

Nanoscale imaging of biological specimens in their native condition is of long-standing interest, in particular with direct, high resolution views of internal structures of intact specimens, though as yet progress has been limited. Here we introduce wet coherent x-ray diffraction microscopy capable of imaging fully hydrated and unstained biological specimens. Whole cell morphologies and internal structures better than 25 nm can be clearly visualized without contrast degradation.

Investigation of the Dynamics of Coherent Structure, BBF, and Intermittent Turbulence in Earth's Magnetotail: A Study of Complexity in Nonlinear Space Plasmas

NASA Technical Reports Server (NTRS)

Chang, Tom

2005-01-01

We have achieved all the goals stated in our grant proposal. Specifically, these include: 1. The understanding of the complexity induced nonlinear spatiotemporal coherent structures and the coexisting propagating modes. 2. The understanding of the intermittent turbulence and energization process of the observed Bursty Bulk Flows (BBF's) in the Earth s magnetotail. 3. The development of "anisotropic three-dimensional complexity" in the plasma sheet due to localized merging and interactions of the magnetic coherent structures. 4. The study of fluctuation-induced nonlinear instabilities and their role in the reconfiguration of magnetic topologies in the magnetotail based on the concepts of the dynamic renormalization group. 5. The acceleration of ions due to the intermittent turbulence of propagating and nonpropagating fluctuations. In the following, we include lists of our published papers, invited talks, and professional activities. A detailed description of our accomplished research results is given..

EFFECT OF COHERENT STRUCTURES ON ENERGETIC PARTICLE INTENSITY IN THE SOLAR WIND AT 1 AU

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tessein, Jeffrey A.; Matthaeus, William H.; Wan, Minping

2015-10-10

We present results from an analysis of Advanced Composition Explorer (ACE) observations of energetic particles in the 0.047–4.78 MeV range associated with shocks and discontinuities in the solar wind. Previous work found a strong correlation between coherent structures and energetic particles measured by ACE/EPAM. Coherent structures are identified using the Partial Variance of Increments (PVI) method, which is essentially a normalized vector increment. The correlation was based on a superposed epoch analysis using over 12 years of data. Here, we examine many individual high-PVI events to better understand this association emphasizing intervals selected from data with shock neighborhoods removed. Wemore » find that in many cases the local maximum in PVI is in a region of rising or falling energetic particle intensity, which suggests that magnetic discontinuities may act as barriers inhibiting the motion of energetic particles across them.« less

Leadership of healthcare commissioning networks in England: a mixed-methods study on clinical commissioning groups

PubMed Central

Zachariadis, Markos; Oborn, Eivor; Barrett, Michael; Zollinger-Read, Paul

2013-01-01

Objective To explore the relational challenges for general practitioner (GP) leaders setting up new network-centric commissioning organisations in the recent health policy reform in England, we use innovation network theory to identify key network leadership practices that facilitate healthcare innovation. Design Mixed-method, multisite and case study research. Setting Six clinical commissioning groups and local clusters in the East of England area, covering in total 208 GPs and 1 662 000 population. Methods Semistructured interviews with 56 lead GPs, practice managers and staff from the local health authorities (primary care trusts, PCT) as well as various healthcare professionals; 21 observations of clinical commissioning group (CCG) board and executive meetings; electronic survey of 58 CCG board members (these included GPs, practice managers, PCT employees, nurses and patient representatives) and subsequent social network analysis. Main outcome measures Collaborative relationships between CCG board members and stakeholders from their healthcare network; clarifying the role of GPs as network leaders; strengths and areas for development of CCGs. Results Drawing upon innovation network theory provides unique insights of the CCG leaders’ activities in establishing best practices and introducing new clinical pathways. In this context we identified three network leadership roles: managing knowledge flows, managing network coherence and managing network stability. Knowledge sharing and effective collaboration among GPs enable network stability and the alignment of CCG objectives with those of the wider health system (network coherence). Even though activities varied between commissioning groups, collaborative initiatives were common. However, there was significant variation among CCGs around the level of engagement with providers, patients and local authorities. Locality (sub) groups played an important role because they linked commissioning decisions with patient needs and brought the leaders closer to frontline stakeholders. Conclusions With the new commissioning arrangements, the leaders should seek to move away from dyadic and transactional relationships to a network structure, thereby emphasising on the emerging relational focus of their roles. Managing knowledge mobility, healthcare network coherence and network stability are the three clinical leadership processes that CCG leaders need to consider in coordinating their network and facilitating the development of good clinical commissioning decisions, best practices and innovative services. To successfully manage these processes, CCG leaders need to leverage the relational capabilities of their network as well as their clinical expertise to establish appropriate collaborations that may improve the healthcare services in England. Lack of local GP engagement adds uncertainty to the system and increases the risk of commissioning decisions being irrelevant and inefficient from patient and provider perspectives. PMID:23430596

Coherent multilayer crystals and method of making

DOEpatents

Schuller, I.K.; Falco, C.M.

A new material consisting of a multilayer crystalline structure is described which is coherent perpendicular to the layers and where each layer is composed of a single crystallilne element. The individual layers may vary from 2A to 100A or more in thickness.

Absence of auditory 'global interference' in autism.

PubMed

Foxton, Jessica M; Stewart, Mary E; Barnard, Louise; Rodgers, Jacqui; Young, Allan H; O'Brien, Gregory; Griffiths, Timothy D

2003-12-01

There has been considerable recent interest in the cognitive style of individuals with Autism Spectrum Disorder (ASD). One theory, that of weak central coherence, concerns an inability to combine stimulus details into a coherent whole. Here we test this theory in the case of sound patterns, using a new definition of the details (local structure) and the coherent whole (global structure). Thirteen individuals with a diagnosis of autism or Asperger's syndrome and 15 control participants were administered auditory tests, where they were required to match local pitch direction changes between two auditory sequences. When the other local features of the sequence pairs were altered (the actual pitches and relative time points of pitch direction change), the control participants obtained lower scores compared with when these details were left unchanged. This can be attributed to interference from the global structure, defined as the combination of the local auditory details. In contrast, the participants with ASD did not obtain lower scores in the presence of such mismatches. This was attributed to the absence of interference from an auditory coherent whole. The results are consistent with the presence of abnormal interactions between local and global auditory perception in ASD.

A Parametric Study of Nonlinear Seismic Response Analysis of Transmission Line Structures

PubMed Central

Wang, Yanming; Yi, Zhenhua

2014-01-01

A parametric study of nonlinear seismic response analysis of transmission line structures subjected to earthquake loading is studied in this paper. The transmission lines are modeled by cable element which accounts for the nonlinearity of the cable based on a real project. Nonuniform ground motions are generated using a stochastic approach based on random vibration analysis. The effects of multicomponent ground motions, correlations among multicomponent ground motions, wave travel, coherency loss, and local site on the responses of the cables are investigated using nonlinear time history analysis method, respectively. The results show the multicomponent seismic excitations should be considered, but the correlations among multicomponent ground motions could be neglected. The wave passage effect has a significant influence on the responses of the cables. The change of the degree of coherency loss has little influence on the response of the cables, but the responses of the cables are affected significantly by the effect of coherency loss. The responses of the cables change little with the degree of the difference of site condition changing. The effect of multicomponent ground motions, wave passage, coherency loss, and local site should be considered for the seismic design of the transmission line structures. PMID:25133215

Quantum coherence in the reflection of above barrier wavepackets

NASA Astrophysics Data System (ADS)

Petersen, Jakob; Pollak, Eli

2018-02-01

The quantum phenomenon of above barrier reflection is investigated from a time-dependent perspective using Gaussian wavepackets. The transition path time distribution, which in principle is experimentally measurable, is used to study the mean flight times ⟨t⟩R and ⟨t⟩T associated with the reflection and the transmission over the barrier paying special attention to their dependence on the width of the barrier. Both flight times, and their difference Δt, exhibit two distinct regimes depending on the ratio of the spatial width of the incident wavepacket and the length of the barrier. When the ratio is larger than unity, the reflection and transmission dynamics are coherent and dominated by the resonances above the barrier. The flight times ⟨t⟩R/T and the flight time difference Δt oscillate as a function of the barrier width (almost in phase with the transmission probability). These oscillations reflect a momentum filtering effect related to the coherent superposition of the reflected and transmitted waves. For a ratio less than unity, the barrier reflection and transmission dynamics are incoherent and the oscillations are absent. The barrier width which separates the coherent and incoherent regimes is identified analytically. The oscillatory structure of the time difference Δt as a function of the barrier width in the coherent regime is absent when considered in terms of the Wigner phase time delays for reflection and transmission. We conclude that the Wigner phase time does not correctly describe the temporal properties of above barrier reflection. We also find that the structure of the reflected and transmitted wavepackets depends on the coherence of the process. In the coherent regime, the wavepackets can have an overlapping peak structure, but the peaks are not fully resolved. In the incoherent regime, the wavepackets split in time into distinct separated Gaussian like waves, each one reflecting the number of times the wavepacket crosses the barrier region before exiting. A classical Wigner approximation, using classical trajectories which upon reaching an edge of the barrier are reflected or transmitted as if the edge was a step potential, is quantitative in the incoherent regime. The implications of the coherence observed on resonance reactive scattering are discussed.

The spatial coherence structure of infrasonic waves: analysis of data from International Monitoring System arrays

NASA Astrophysics Data System (ADS)

Green, David N.

2015-04-01

The spatial coherence structure of 30 infrasound array detections, with source-to-receiver ranges of 25-6500 km, has been measured within the 0.25-1 Hz passband. The data were recorded at International Monitoring System (IMS) microbarograph arrays with apertures of between 1 and 4 km. Such array detections are of interest for Comprehensive Nuclear-Test-Ban Treaty monitoring. The majority of array detections (e.g. 80 per cent of recordings in the third-octave passband centred on 0.63 Hz) exhibit spatial coherence loss anisotropy that is consistent with previous lower frequency atmospheric acoustic studies; coherence loss is more rapid perpendicular to the acoustic propagation direction than parallel to it. The thirty array detections display significant interdetection variation in the magnitude of spatial coherence loss. The measurements can be explained by the simultaneous arrival of wave fronts at the recording array with angular beamwidths of between 0.4 and 7° and velocity bandwidths of between 2 and 40 m s-1. There is a statistically significant positive correlation between source-to-receiver range and the magnitude of coherence loss. Acoustic multipathing generated by interactions with fine-scale wind and temperature gradients along stratospheric propagation paths is qualitatively consistent with the observations. In addition, the study indicates that to isolate coherence loss generated by propagation effects, analysis of signals exhibiting high signal-to-noise ratios (SNR) is required (SNR2 > 11 in this study). The rapid temporal variations in infrasonic noise observed in recordings at IMS arrays indicates that correcting measured coherence values for the effect of noise, using pre-signal estimates of noise power, is ineffective.

The Observation of the Structure of M23C6/ γ Coherent Interface in the 100Mn13 High Carbon High Manganese Steel

NASA Astrophysics Data System (ADS)

Xu, Zhenfeng; Ding, Zhimin; Liang, Bo

2018-03-01

The M23C6 carbides precipitate along the austenite grain boundary in the 100Mn13 high carbon high manganese steel after 1323 K (1050 °C) solution treatment and subsequent 748 K (475 °C) aging treatment. The grain boundary M23C6 carbides not only spread along the grain boundary and into the incoherent austenite grain, but also grow slowly into the coherent austenite grain. On the basis of the research with optical microscope, a further investigation for the M23C6/ γ coherent interface was carried out by transmission electron microscope (TEM). The results show that the grain boundary M23C6 carbides have orientation relationships with only one of the adjacent austenite grains in the same planes: (\\bar{1}1\\bar{1})_{{{M}_{ 2 3} {C}_{ 6} }} //(\\bar{1}1\\bar{1})_{γ } , (\\bar{1}11)_{{{M}_{ 2 3} {C}_{ 6} }} //(\\bar{1}11)_{γ } ,[ 1 10]_{{{M}_{ 2 3} {C}_{ 6} }} //[ 1 10]_{γ } . The flat M23C6/ γ coherent interface lies on the low indexed crystal planes {111}. Moreover, in M23C6/ γ coherent interface, there are embossments which stretch into the coherent austenite grain γ. Dislocations distribute in the embossments and coherent interface frontier. According to the experimental observation, the paper suggests that the embossments can promote the M23C6/ γ coherent interface move. Besides, the present work has analyzed chemical composition of experimental material and the crystal structures of austenite and M23C6, which indicates that the transformation can be completed through a little diffusion for C atoms and a simple variant for austenite unit cell.

Frobenius-norm-based measures of quantum coherence and asymmetry

PubMed Central

Yao, Yao; Dong, G. H.; Xiao, Xing; Sun, C. P.

2016-01-01

We formulate the Frobenius-norm-based measures for quantum coherence and asymmetry respectively. In contrast to the resource theory of coherence and asymmetry, we construct a natural measure of quantum coherence inspired from optical coherence theory while the group theoretical approach is employed to quantify the asymmetry of quantum states. Besides their simple structures and explicit physical meanings, we observe that these quantities are intimately related to the purity (or linear entropy) of the corresponding quantum states. Remarkably, we demonstrate that the proposed coherence quantifier is not only a measure of mixedness, but also an intrinsic (basis-independent) quantification of quantum coherence contained in quantum states, which can also be viewed as a normalized version of Brukner-Zeilinger invariant information. In our context, the asymmetry of N-qubit quantum systems is considered under local independent and collective transformations. In- triguingly, it is illustrated that the collective effect has a significant impact on the asymmetry measure, and quantum correlation between subsystems plays a non-negligible role in this circumstance. PMID:27558009

Nonlocal Electron Coherence in MoS2 Flakes Correlated through Spatial Self Phase Modulation

NASA Astrophysics Data System (ADS)

Wu, Yanling; Wu, Qiong; Sun, Fei; Tian, Yichao; Zuo, Xu; Meng, Sheng; Zhao, Jimin

2015-03-01

Electron coherence among different flake domains of MoS2 has been generated using ultrafast or continuous wave laser beams. Such electron coherence generates characteristic far-field diffraction patterns through a purely coherent nonlinear optical effect--spatial self-phase modulation (SSPM). A wind-chime model is developed to describe the establishment of the electron coherence through correlating the photo-excited electrons among different flakes using coherent light. Owing to its finite gap band structure, we find different mechanisms, including two-photon processes, might be responsible for the SSPM in MoS2 [with a large nonlinear dielectric susceptibility χ (3) = 1.6 × 10-9 e.s.u. (SI: 2.23 × 10-17 m2/V2) per layer]. Finally, we realized all optical switching based on SSPM, demonstrating that the electron coherence generation we report here is a ubiquitous property of layered quantum materials, by which novel optical applications are accessible. National Natural Science Foundation of China (11274372).

Three-dimensional wide-field pump-probe structured illumination microscopy

PubMed Central

Kim, Yang-Hyo; So, Peter T.C.

2017-01-01

We propose a new structured illumination scheme for achieving depth resolved wide-field pump-probe microscopy with sub-diffraction limit resolution. By acquiring coherent pump-probe images using a set of 3D structured light illumination patterns, a 3D super-resolution pump-probe image can be reconstructed. We derive the theoretical framework to describe the coherent image formation and reconstruction scheme for this structured illumination pump-probe imaging system and carry out numerical simulations to investigate its imaging performance. The results demonstrate a lateral resolution improvement by a factor of three and providing 0.5 µm level axial optical sectioning. PMID:28380860

Atmospheric propagation and combining of high-power lasers.

PubMed

Nelson, W; Sprangle, P; Davis, C C

2016-03-01

In this paper, we analyze beam combining and atmospheric propagation of high-power lasers for directed-energy (DE) applications. The large linewidths inherent in high-power fiber and slab lasers cause random phase and intensity fluctuations that occur on subnanosecond time scales. Coherently combining these high-power lasers would involve instruments capable of precise phase control and operation at rates greater than ∼10  GHz. To the best of our knowledge, this technology does not currently exist. This presents a challenging problem when attempting to phase lock high-power lasers that is not encountered when phase locking low-power lasers, for example, at milliwatt power levels. Regardless, we demonstrate that even if instruments are developed that can precisely control the phase of high-power lasers, coherent combining is problematic for DE applications. The dephasing effects of atmospheric turbulence typically encountered in DE applications will degrade the coherent properties of the beam before it reaches the target. Through simulations, we find that coherent beam combining in moderate turbulence and over multikilometer propagation distances has little advantage over incoherent combining. Additionally, in cases of strong turbulence and multikilometer propagation ranges, we find nearly indistinguishable intensity profiles and virtually no difference in the energy on the target between coherently and incoherently combined laser beams. Consequently, we find that coherent beam combining at the transmitter plane is ineffective under typical atmospheric conditions.

Rotating coherent flow structures as a source for narrowband tip clearance noise from axial fans

NASA Astrophysics Data System (ADS)

Zhu, Tao; Lallier-Daniels, Dominic; Sanjosé, Marlène; Moreau, Stéphane; Carolus, Thomas

2018-03-01

Noise from axial fans typically increases significantly as the tip clearance is increased. In addition to the broadband tip clearance noise at the design flow rate, narrowband humps also associated with the tip flow are observed in the far-field acoustic spectra at lower flow rate. In this study, both experimental and numerical methods are used to shed more light on the noise generation mechanism of this narrowband tip clearance noise and provide a unified description of this source. Unsteady aeroacoustic predictions with the Lattice-Boltzmann Method (LBM) are successfully compared with experiment. Such a validation allows using LBM data to conduct a detailed modal analysis of the pressure field for detecting rotating coherent flow structures which might be considered as noise sources. As previously found in ring fans the narrowband humps in the far-field noise spectra are found to be related to the tip clearance noise that is generated by an interaction of coherent flow structures present in the tip region with the leading edge of the impeller blades. The visualization of the coherent structures shows that they are indeed part of the unsteady tip clearance vortex structures. They are hidden in a complex, spatially and temporally inhomogeneous flow field, but can be recovered by means of appropriate filtering techniques. Their pressure trace corresponds to the so-called rotational instability identified in previous turbomachinery studies, which brings a unified picture of this tip-noise phenomenon for the first time.

Coherent structures in the Es layer and neutral middle atmosphere

NASA Astrophysics Data System (ADS)

Mošna, Zbyšek; Knížová, Petra Koucká; Potužníková, Kateřina

2015-12-01

The present paper shows results from the summer campaign performed during geomagnetically quiet period from June 1 to August 31, 2009. Within time-series of stratospheric and mesospheric temperatures at pressure levels 10-0.1 hPa, mesospheric winds measured in Collm, Germany, and the sporadic E-layer parameters foEs and hEs measured at the Pruhonice station we detected specific coherent wave-bursts in planetary wave domain. Permanent wave-like activity is observed in all analyzed data sets. However, the number of wave-like structures persistent in large range of height from the stratosphere to lower ionosphere is limited. The only coherent modes that are detected on consequent levels of the atmosphere are those corresponding to eigenmodes of planetary waves.

Beyond crystallography: diffractive imaging using coherent x-ray light sources.

PubMed

Miao, Jianwei; Ishikawa, Tetsuya; Robinson, Ian K; Murnane, Margaret M

2015-05-01

X-ray crystallography has been central to the development of many fields of science over the past century. It has now matured to a point that as long as good-quality crystals are available, their atomic structure can be routinely determined in three dimensions. However, many samples in physics, chemistry, materials science, nanoscience, geology, and biology are noncrystalline, and thus their three-dimensional structures are not accessible by traditional x-ray crystallography. Overcoming this hurdle has required the development of new coherent imaging methods to harness new coherent x-ray light sources. Here we review the revolutionary advances that are transforming x-ray sources and imaging in the 21st century. Copyright © 2015, American Association for the Advancement of Science.

Coherent manipulation of spontaneous emission spectra in coupled semiconductor quantum well structures.

PubMed

Chen, Aixi

2014-11-03

In triple coupled semiconductor quantum well structures (SQWs) interacting with a coherent driving filed, a coherent coupling field and a weak probe field, spontaneous emission spectra are investigated. Our studies show emission spectra can easily be manipulated through changing the intensity of the driving and coupling field, detuning of the driving field. Some interesting physical phenomena such as spectral-line enhancement/suppression, spectral-line narrowing and spontaneous emission quenching may be obtained in our system. The theoretical studies of spontaneous emission spectra in SQWS have potential application in high-precision spectroscopy. Our studies are based on the real physical system [Appl. Phys. Lett.86(20), 201112 (2005)], and this scheme might be realizable with presently available techniques.

Coherent organization in gene regulation: a study on six networks

NASA Astrophysics Data System (ADS)

Aral, Neşe; Kabakçıoğlu, Alkan

2016-04-01

Structural and dynamical fingerprints of evolutionary optimization in biological networks are still unclear. Here we analyze the dynamics of genetic regulatory networks responsible for the regulation of cell cycle and cell differentiation in three organisms or cell types each, and show that they follow a version of Hebb's rule which we have termed coherence. More precisely, we find that simultaneously expressed genes with a common target are less likely to act antagonistically at the attractors of the regulatory dynamics. We then investigate the dependence of coherence on structural parameters, such as the mean number of inputs per node and the activatory/repressory interaction ratio, as well as on dynamically determined quantities, such as the basin size and the number of expressed genes.

Keeping time: could quantum beating in microtubules be the basis for the neural synchrony related to consciousness?

PubMed

Craddock, Travis J A; Priel, Avner; Tuszynski, Jack A

2014-06-01

This paper discusses the possibility of quantum coherent oscillations playing a role in neuronal signaling. Consciousness correlates strongly with coherent neural oscillations, however the mechanisms by which neurons synchronize are not fully elucidated. Recent experimental evidence of quantum beats in light-harvesting complexes of plants (LHCII) and bacteria provided a stimulus for seeking similar effects in important structures found in animal cells, especially in neurons. We argue that microtubules (MTs), which play critical roles in all eukaryotic cells, possess structural and functional characteristics that are consistent with quantum coherent excitations in the aromatic groups of their tryptophan residues. Furthermore we outline the consequences of these findings on neuronal processes including the emergence of consciousness.

Observation of electromigration in a Cu thin line by in situ coherent x-ray diffraction microscopy

NASA Astrophysics Data System (ADS)

Takahashi, Yukio; Nishino, Yoshinori; Furukawa, Hayato; Kubo, Hideto; Yamauchi, Kazuto; Ishikawa, Tetsuya; Matsubara, Eiichiro

2009-06-01

Electromigration (EM) in a 1-μm-thick Cu thin line was investigated by in situ coherent x-ray diffraction microscopy (CXDM). Characteristic x-ray speckle patterns due to both EM-induced voids and thermal deformation in the thin line were observed in the coherent x-ray diffraction patterns. Both parts of the voids and the deformation were successfully visualized in the images reconstructed from the diffraction patterns. This result not only represents the first demonstration of the visualization of structural changes in metallic materials by in situ CXDM but is also an important step toward studying the structural dynamics of nanomaterials using x-ray free-electron lasers in the near future.

Propagation of a partially coherent hollow vortex Gaussian beam through a paraxial ABCD optical system in turbulent atmosphere.

PubMed

Zhou, Guoquan; Cai, Yangjian; Chu, Xiuxiang

2012-04-23

The propagation of a partially coherent hollow vortex Gaussian beam through a paraxial ABCD optical system in turbulent atmosphere has been investigated. The analytical expressions for the average intensity and the degree of the polarization of a partially coherent hollow vortex Gaussian beam through a paraxial ABCD optical system are derived in turbulent atmosphere, respectively. The average intensity distribution and the degree of the polarization of a partially coherent hollow vortex Gaussian beam in turbulent atmosphere are numerically demonstrated. The influences of the beam parameters, the topological charge, the transverse coherent lengths, and the structure constant of the atmospheric turbulence on the propagation of a partially coherent hollow vortex Gaussian beam in turbulent atmosphere are also examined in detail. This research is beneficial to the practical applications in free-space optical communications and the remote sensing of the dark hollow beams. © 2012 Optical Society of America

Ultra-broadband ptychography with self-consistent coherence estimation from a high harmonic source

NASA Astrophysics Data System (ADS)

Odstrčil, M.; Baksh, P.; Kim, H.; Boden, S. A.; Brocklesby, W. S.; Frey, J. G.

2015-09-01

With the aim of improving imaging using table-top extreme ultraviolet sources, we demonstrate coherent diffraction imaging (CDI) with relative bandwidth of 20%. The coherence properties of the illumination probe are identified using the same imaging setup. The presented methods allows for the use of fewer monochromating optics, obtaining higher flux at the sample and thus reach higher resolution or shorter exposure time. This is important in the case of ptychography when a large number of diffraction patterns need to be collected. Our microscopy setup was tested on a reconstruction of an extended sample to show the quality of the reconstruction. We show that high harmonic generation based EUV tabletop microscope can provide reconstruction of samples with a large field of view and high resolution without additional prior knowledge about the sample or illumination.

Temporal characterization of the wave-breaking flash in a laser plasma accelerator

NASA Astrophysics Data System (ADS)

Miao, Bo; Feder, Linus; Goers, Andrew; Hine, George; Salehi, Fatholah; Wahlstrand, Jared; Woodbury, Daniel; Milchberg, Howard

2017-10-01

Wave-breaking injection of electrons into a relativistic plasma wake generated in near-critical density plasma by sub-terawatt laser pulses generates an intense ( 1 μJ) and ultra-broadband (Δλ 300 nm) radiation flash. In this work we demonstrate the spectral coherence of this radiation and measure its temporal width using single-shot supercontinuum spectral interferometry (SSSI). The measured temporal width is limited by measurement resolution to 50 fs. Spectral coherence is corroborated by PIC simulations which show that the spatial extent of the acceleration trajectory at the trapping region is small compared to the radiation center wavelength. To our knowledge, this is the first temporal and coherence characterization of wave-breaking radiation. This work is supported by the US Department of Energy, the National Science Foundation, and the Air Force Office of Scientific Research.

Estimation of signal coherence threshold and concealed spectral lines applied to detection of turbofan engine combustion noise.

PubMed

Miles, Jeffrey Hilton

2011-05-01

Combustion noise from turbofan engines has become important, as the noise from sources like the fan and jet are reduced. An aligned and un-aligned coherence technique has been developed to determine a threshold level for the coherence and thereby help to separate the coherent combustion noise source from other noise sources measured with far-field microphones. This method is compared with a statistics based coherence threshold estimation method. In addition, the un-aligned coherence procedure at the same time also reveals periodicities, spectral lines, and undamped sinusoids hidden by broadband turbofan engine noise. In calculating the coherence threshold using a statistical method, one may use either the number of independent records or a larger number corresponding to the number of overlapped records used to create the average. Using data from a turbofan engine and a simulation this paper shows that applying the Fisher z-transform to the un-aligned coherence can aid in making the proper selection of samples and produce a reasonable statistics based coherence threshold. Examples are presented showing that the underlying tonal and coherent broad band structure which is buried under random broadband noise and jet noise can be determined. The method also shows the possible presence of indirect combustion noise.

Online Knowledge-Based Model for Big Data Topic Extraction

PubMed Central

Khan, Muhammad Taimoor; Durrani, Mehr; Khalid, Shehzad; Aziz, Furqan

2016-01-01

Lifelong machine learning (LML) models learn with experience maintaining a knowledge-base, without user intervention. Unlike traditional single-domain models they can easily scale up to explore big data. The existing LML models have high data dependency, consume more resources, and do not support streaming data. This paper proposes online LML model (OAMC) to support streaming data with reduced data dependency. With engineering the knowledge-base and introducing new knowledge features the learning pattern of the model is improved for data arriving in pieces. OAMC improves accuracy as topic coherence by 7% for streaming data while reducing the processing cost to half. PMID:27195004

Bacillus thuringiensis and Its Pesticidal Crystal Proteins

PubMed Central

Schnepf, E.; Crickmore, N.; Van Rie, J.; Lereclus, D.; Baum, J.; Feitelson, J.; Zeigler, D. R.; Dean, D. H.

1998-01-01

During the past decade the pesticidal bacterium Bacillus thuringiensis has been the subject of intensive research. These efforts have yielded considerable data about the complex relationships between the structure, mechanism of action, and genetics of the organism’s pesticidal crystal proteins, and a coherent picture of these relationships is beginning to emerge. Other studies have focused on the ecological role of the B. thuringiensis crystal proteins, their performance in agricultural and other natural settings, and the evolution of resistance mechanisms in target pests. Armed with this knowledge base and with the tools of modern biotechnology, researchers are now reporting promising results in engineering more-useful toxins and formulations, in creating transgenic plants that express pesticidal activity, and in constructing integrated management strategies to insure that these products are utilized with maximum efficiency and benefit. PMID:9729609

Retinal Evaluation Using Optical Coherence Tomography (OCT) During Deep Space Gateway Missions

NASA Astrophysics Data System (ADS)

Stenger, M. B.; Laurie, S. S.; Macias, B. R.; Barr, Y. R.

2018-02-01

Optical Coherence Tomography (OCT) imaging will be conducted before, during, and after Deep Space Gateway missions to evaluate changes in the retina and, in particular, the optic nerve head and surrounding structures. Additional parameters will be collected before and after flight.

Quantum coherence selective 2D Raman–2D electronic spectroscopy

PubMed Central

Spencer, Austin P.; Hutson, William O.; Harel, Elad

2017-01-01

Electronic and vibrational correlations report on the dynamics and structure of molecular species, yet revealing these correlations experimentally has proved extremely challenging. Here, we demonstrate a method that probes correlations between states within the vibrational and electronic manifold with quantum coherence selectivity. Specifically, we measure a fully coherent four-dimensional spectrum which simultaneously encodes vibrational–vibrational, electronic–vibrational and electronic–electronic interactions. By combining near-impulsive resonant and non-resonant excitation, the desired fifth-order signal of a complex organic molecule in solution is measured free of unwanted lower-order contamination. A critical feature of this method is electronic and vibrational frequency resolution, enabling isolation and assignment of individual quantum coherence pathways. The vibronic structure of the system is then revealed within an otherwise broad and featureless 2D electronic spectrum. This method is suited for studying elusive quantum effects in which electronic transitions strongly couple to phonons and vibrations, such as energy transfer in photosynthetic pigment–protein complexes. PMID:28281541

A ridge tracking algorithm and error estimate for efficient computation of Lagrangian coherent structures.

PubMed

Lipinski, Doug; Mohseni, Kamran

2010-03-01

A ridge tracking algorithm for the computation and extraction of Lagrangian coherent structures (LCS) is developed. This algorithm takes advantage of the spatial coherence of LCS by tracking the ridges which form LCS to avoid unnecessary computations away from the ridges. We also make use of the temporal coherence of LCS by approximating the time dependent motion of the LCS with passive tracer particles. To justify this approximation, we provide an estimate of the difference between the motion of the LCS and that of tracer particles which begin on the LCS. In addition to the speedup in computational time, the ridge tracking algorithm uses less memory and results in smaller output files than the standard LCS algorithm. Finally, we apply our ridge tracking algorithm to two test cases, an analytically defined double gyre as well as the more complicated example of the numerical simulation of a swimming jellyfish. In our test cases, we find up to a 35 times speedup when compared with the standard LCS algorithm.

Direct measurement of the propagation velocity of defects using coherent X-rays

DOE PAGES

Ulbrandt, Jeffrey G.; Rainville, Meliha G.; Wagenbach, Christa; ...

2016-03-28

The properties of artificially grown thin films are often strongly affected by the dynamic relationships between surface growth processes and subsurface structure. Coherent mixing of X-ray signals promises to provide an approach to better understand such processes. Here, we demonstrate the continuously variable mixing of surface and bulk scattering signals during realtime studies of sputter deposition of a-Si and a-WSi2 films by controlling the X-ray penetration and escape depths in coherent grazing-incidence small-angle X-ray scattering. Under conditions where the X-ray signal comes from both the growth surface and the thin film bulk, oscillations in temporal correlations arise from coherent interferencemore » between scattering from stationary bulk features and from the advancing surface. We also observe evidence that elongated bulk features propagate upwards at the same velocity as the surface. Moreover, a highly surface-sensitive mode is demonstrated that can access the surface dynamics independently of the subsurface structure.« less

[Meaning in life and mental health: personal meaning systems of psychotherapists and psychotherapy patients].

PubMed

Löffler, Sabine; Knappe, Rainer; Joraschky, Peter; Pöhlmann, Karin

2010-01-01

This study investigated differences in the personal meaning systems of psychotherapists and psychotherapy patients as well as correlations between meaning in life and mental health. We qualitatively assessed the content and structure of the personal meaning systems of 41 psychotherapists and 77 psychotherapy patients. In addition, the participants completed questionnaires measuring meaning in life (LRI-r-d), sense of coherence (SOC-9L), self-esteem (RSES), satisfaction with life (SWLS), self-efficacy (SWK), and depression (BDI). The personal meaning systems of psychotherapists were more complex and coherent compared to psychotherapy patients. In the group of psychotherapy patients, a more elaborate structure of the personal meaning system correlated with the subjective sense of meaning. We were able to confirm correlations between meaning in life and mental health for most of the instances. Psychotherapists had more elaborate and coherent meaning systems than psychotherapy patients. Especially for psychotherapy patients elaborate and coherent meaning systems turned out to be important for mental health.

Accelerating Time-Varying Hardware Volume Rendering Using TSP Trees and Color-Based Error Metrics

NASA Technical Reports Server (NTRS)

Ellsworth, David; Chiang, Ling-Jen; Shen, Han-Wei; Kwak, Dochan (Technical Monitor)

2000-01-01

This paper describes a new hardware volume rendering algorithm for time-varying data. The algorithm uses the Time-Space Partitioning (TSP) tree data structure to identify regions within the data that have spatial or temporal coherence. By using this coherence, the rendering algorithm can improve performance when the volume data is larger than the texture memory capacity by decreasing the amount of textures required. This coherence can also allow improved speed by appropriately rendering flat-shaded polygons instead of textured polygons, and by not rendering transparent regions. To reduce the polygonization overhead caused by the use of the hierarchical data structure, we introduce an optimization method using polygon templates. The paper also introduces new color-based error metrics, which more accurately identify coherent regions compared to the earlier scalar-based metrics. By showing experimental results from runs using different data sets and error metrics, we demonstrate that the new methods give substantial improvements in volume rendering performance.

Beam wander and M2-factor of partially coherent electromagnetic hollow Gaussian beam propagating through non-Kolmogorov turbulence

NASA Astrophysics Data System (ADS)

Xu, Yonggen; Tian, Huanhuan; Dan, Youquan; Feng, Hao; Wang, Shijian

2017-04-01

Propagation formulae for M2-factor and beam wander of partially coherent electromagnetic hollow Gaussian (PCEHG) beam in non-Kolmogorov turbulence are derived based on the extended Huygens-Fresnel principle and the second-order moments of the Wigner distribution function. Our results indicate that the normalized M2-factors of PCEHG beam with larger beam order, waist width, inner scale of turbulence, the generalized exponent parameter, and smaller transverse coherent widths, outer scale of turbulence, the generalized structure parameter are less affected by the turbulence. The root mean square beam wander and relative beam wander are more obvious for PCEHG beam with smaller beam order, larger inner and outer scales of turbulence, exponent parameter, transverse coherent widths, and the generalized structure parameter. What is more, the beam wander properties of PCEHG beam in non-Kolmogorov turbulence are very different from M2-factor and spreading properties of beam in turbulence.

Defending a coherent autobiography: when past events appear incoherent, mortality salience prompts compensatory bolstering of the past's significance and the future's orderliness.

PubMed

Landau, Mark J; Greenberg, Jeff; Sullivan, Daniel

2009-08-01

Drawing on terror management theory, we propose that maintaining a coherent autobiography protects the individual from mortality concerns by imbuing experience over time with significance and order. Two studies test whether mortality salience combined with a threat to autobiographical coherence (induced by an alphabetical organization of past events) prompts compensatory bolstering of the significance and orderliness of temporal experience. In Study 1, whereas exclusion-primed participants led to organize past events alphabetically perceived their past as less significant, mortality salient participants showed a compensatory boost in perceptions of their past's significance. In Study 2, mortality salience and an alphabetic event organization led participants high in personal need for structure to parse their future into clearly defined temporal intervals. This research is the first to experimentally assess the role of existential concerns in people's motivation to defend the significance and structure of their temporal experience against threats to autobiographical coherence.

Coherent wavepackets in the Fenna-Matthews-Olson complex are robust to excitonic-structure perturbations caused by mutagenesis

NASA Astrophysics Data System (ADS)

Maiuri, Margherita; Ostroumov, Evgeny E.; Saer, Rafael G.; Blankenship, Robert E.; Scholes, Gregory D.

2018-02-01

Femtosecond pulsed excitation of light-harvesting complexes creates oscillatory features in their response. This phenomenon has inspired a large body of work aimed at uncovering the origin of the coherent beatings and possible implications for function. Here we exploit site-directed mutagenesis to change the excitonic level structure in Fenna-Matthews-Olson (FMO) complexes and compare the coherences using broadband pump-probe spectroscopy. Our experiments detect two oscillation frequencies with dephasing on a picosecond timescale—both at 77 K and at room temperature. By studying these coherences with selective excitation pump-probe experiments, where pump excitation is in resonance only with the lowest excitonic state, we show that the key contributions to these oscillations stem from ground-state vibrational wavepackets. These experiments explicitly show that the coherences—although in the ground electronic state—can be probed at the absorption resonances of other bacteriochlorophyll molecules because of delocalization of the electronic excitation over several chromophores.

Determination of the effective transverse coherence of the neutron wave packet as employed in reflectivity investigations of condensed-matter structures. I. Measurements

NASA Astrophysics Data System (ADS)

Majkrzak, Charles F.; Metting, Christopher; Maranville, Brian B.; Dura, Joseph A.; Satija, Sushil; Udovic, Terrence; Berk, Norman F.

2014-03-01

The primary purpose of this investigation is to determine the effective coherent extent of the neutron wave packet transverse to its mean propagation vector k when it is prepared in a typical instrument used to study the structure of materials in thin film form via specular reflection. There are two principal reasons for doing so. One has to do with the fundamental physical interest in the characteristics of a free neutron as a quantum object, while the other is of a more practical nature, relating to the understanding of how to interpret elastic scattering data when the neutron is employed as a probe of condensed-matter structure on an atomic or nanometer scale. Knowing such a basic physical characteristic as the neutron's effective transverse coherence can dictate how to properly analyze specular reflectivity data obtained for material film structures possessing some amount of in-plane inhomogeneity. In this study we describe a means of measuring the effective transverse coherence length of the neutron wave packet by specular reflection from a series of diffraction gratings of different spacings. Complementary nonspecular measurements of the widths of grating reflections were also performed, which corroborate the specular results. (This paper principally describes measurements interpreted according to the theoretical picture presented in a companion paper.) Each grating was fabricated by lift-off photolithography patterning of a nickel film (approximately 1000 Å thick) formed by physical vapor deposition on a flat silicon crystal surface. The grating periods ranged from 10 μm (5 μm Ni stripe, 5 μm intervening space) to several hundred microns. The transverse coherence length, modeled as the width of the wave packet, was determined from an analysis of the specular reflectivity curves of the set of gratings.

Revealing retroperitoneal liposarcoma morphology using optical coherence tomography

NASA Astrophysics Data System (ADS)

Carbajal, Esteban F.; Baranov, Stepan A.; Manne, Venu G. R.; Young, Eric D.; Lazar, Alexander J.; Lev, Dina C.; Pollock, Raphael E.; Larin, Kirill V.

2011-02-01

A new approach to distinguish normal fat, well-differentiated (WD), and dedifferentiated liposarcoma (LS) tumors is demonstrated, based on the use of optical coherence tomography (OCT). OCT images show the same structures seen with conventional histological methods. Our visual grading analysis is supported by numerical analysis of observed structures for normal fat and WDLS samples. Further development could apply the real-time and high resolution advantages of OCT for use in liposarcoma diagnosis and clinical procedures.

Lensless Tomographic Imaging of Near Surface Structures of Frozen Hydrated Malaria-Infected Human Erythrocytes by Coherent X-Ray Diffraction Microscopy.

PubMed

Frank, Viktoria; Chushkin, Yuriy; Fröhlich, Benjamin; Abuillan, Wasim; Rieger, Harden; Becker, Alexandra S; Yamamoto, Akihisa; Rossetti, Fernanda F; Kaufmann, Stefan; Lanzer, Michael; Zontone, Federico; Tanaka, Motomu

2017-10-26

Lensless, coherent X-ray diffraction microscopy has been drawing considerable attentions for tomographic imaging of whole human cells. In this study, we performed cryogenic coherent X-ray diffraction imaging of human erythrocytes with and without malaria infection. To shed light on structural features near the surface, "ghost cells" were prepared by the removal of cytoplasm. From two-dimensional images, we found that the surface of erythrocytes after 32 h of infection became much rougher compared to that of healthy, uninfected erythrocytes. The Gaussian roughness of an infected erythrocyte surface (69 nm) is about two times larger than that of an uninfected one (31 nm), reflecting the formation of protein knobs on infected erythrocyte surfaces. Three-dimensional tomography further enables to obtain images of the whole cells with no remarkable radiation damage, whose accuracy was estimated using phase retrieval transfer functions to be as good as 64 nm for uninfected and 80 nm for infected erythrocytes, respectively. Future improvements in phase retrieval algorithm, increase in degree of coherence, and higher flux in combination with complementary X-ray fluorescence are necessary to gain both structural and chemical details of mesoscopic architectures, such as cytoskeletons, membraneous structures, and protein complexes, in frozen hydrated human cells, especially under diseased states.

Deriving Lifetime Maps in the Time/Frequency Domain of Coherent Structures in the Turbulent Boundary Layer

NASA Technical Reports Server (NTRS)

Palumbo, Dan

2008-01-01

The lifetimes of coherent structures are derived from data correlated over a 3 sensor array sampling streamwise sidewall pressure at high Reynolds number (> 10(exp 8)). The data were acquired at subsonic, transonic and supersonic speeds aboard a Tupolev Tu-144. The lifetimes are computed from a variant of the correlation length termed the lifelength. Characteristic lifelengths are estimated by fitting a Gaussian distribution to the sensors cross spectra and are shown to compare favorably with Efimtsov s prediction of correlation space scales. Lifelength distributions are computed in the time/frequency domain using an interval correlation technique on the continuous wavelet transform of the original time data. The median values of the lifelength distributions are found to be very close to the frequency averaged result. The interval correlation technique is shown to allow the retrieval and inspection of the original time data of each event in the lifelength distributions, thus providing a means to locate and study the nature of the coherent structure in the turbulent boundary layer. The lifelength data are converted to lifetimes using the convection velocity. The lifetime of events in the time/frequency domain are displayed in Lifetime Maps. The primary purpose of the paper is to validate these new analysis techniques so that they can be used with confidence to further characterize the behavior of coherent structures in the turbulent boundary layer.

The organization of prospective thinking: evidence of event clusters in freely generated future thoughts.

PubMed

Demblon, Julie; D'Argembeau, Arnaud

2014-02-01

Recent research suggests that many imagined future events are not represented in isolation, but instead are embedded in broader event sequences-referred to as event clusters. It remains unclear, however, whether the production of event clusters reflects the underlying organizational structure of prospective thinking or whether it is an artifact of the event-cuing task in which participants are explicitly required to provide chains of associated future events. To address this issue, the present study examined whether the occurrence of event clusters in prospective thought is apparent when people are left to think freely about events that might happen in their personal future. The results showed that the succession of events participants spontaneously produced when envisioning their future frequently included event clusters. This finding provides more compelling evidence that prospective thinking involves higher-order autobiographical knowledge structures that organize imagined events in coherent themes and sequences. Copyright © 2014 Elsevier Inc. All rights reserved.

Categorizing words through semantic memory navigation

NASA Astrophysics Data System (ADS)

Borge-Holthoefer, J.; Arenas, A.

2010-03-01

Semantic memory is the cognitive system devoted to storage and retrieval of conceptual knowledge. Empirical data indicate that semantic memory is organized in a network structure. Everyday experience shows that word search and retrieval processes provide fluent and coherent speech, i.e. are efficient. This implies either that semantic memory encodes, besides thousands of words, different kind of links for different relationships (introducing greater complexity and storage costs), or that the structure evolves facilitating the differentiation between long-lasting semantic relations from incidental, phenomenological ones. Assuming the latter possibility, we explore a mechanism to disentangle the underlying semantic backbone which comprises conceptual structure (extraction of categorical relations between pairs of words), from the rest of information present in the structure. To this end, we first present and characterize an empirical data set modeled as a network, then we simulate a stochastic cognitive navigation on this topology. We schematize this latter process as uncorrelated random walks from node to node, which converge to a feature vectors network. By doing so we both introduce a novel mechanism for information retrieval, and point at the problem of category formation in close connection to linguistic and non-linguistic experience.

Coherent nonlinear coupling between a long-wavelength mode and small-scale turbulence in the TEXT tokamak

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tsui, H.Y.W.; Rypdal, K.; Ritz, C.P.

1993-04-26

Bispectral analysis of Langmuir probe data indicates that coherent nonlinear coupling, in addition to the noncoherent turbulent interactions, exists in the edge plasma of the tokamak TEXT. Not all the modes involved reside within the spectral region of the usual broadband turbulence. At a major resonant surface the small-scale turbulent activity interacts [ital coherently] with a localized long-wavelength mode; a signature of regular or coherent structure. By the observed coupling to the transport related turbulence, the long-wavelength mode can influence plasma confinement indirectly. These observations signify the influence of low-order resonant surfaces on the edge turbulence in tokamaks.

Partially coherent polarized atmospheric transmission characteristics and application technology research

NASA Astrophysics Data System (ADS)

Fu, Qiang; Gao, Duorui; Liu, Zhi; Chen, Chunyi; Lou, Yan; Jiang, Huilin

2014-11-01

Based on partially coherent polarized light transmission characteristics of the atmosphere, an intensity expression of completely coherent flashing light is derived from Andrews scale modulation method. According to the generalized Huygens-Fresnel principle and Rytov theory, the phase fluctuation structure function is obtained on condition that the refractive index profile in the atmosphere meet Von Karman spectrum, then get the arrival Angle fluctuation variance. Through the RMS beam width of gaussian beams in turbulent atmosphere, deviation angle formula of fully coherent gaussian beams in turbulence atmosphere is attained, then get the RMS beam width of partially coherent and derivation angle expression of GSM beam in turbulent atmosphere. Combined with transmission properties of radial polarized laser beam, cross spectral density matrix of partially coherent radially polarized light can be gained by using generalized huygens-fresnel principle. And light intensity and polarization after transmission can be known according to the unity of coherence and polarization theory. On the basis of the analysis model and numerical simulation, the simulation results show that: the light spot caused by atmospheric turbulence of partially coherent polarization will be superior to completely polarized light.Taking advantage of this feature, designed a new wireless suppression technology of atmospheric turbulence, that is the optimization criterion of initial degree of coherent light beam. The optimal initial degree of coherent light beam will change along with the change of atmospheric turbulence conditions,make control the beam's initial degree of coherence to realize the initial degree of coherence of light beam in real time and dynamic control. A spatial phase screen before emission aperture of fully coherent light is to generate the partially coherent light, liquid crystal spatial light modulator is is a preferable way to realize the dynamic random phase. Finally look future of the application research of partially coherent light.

Three-Dimensional parton structure of light nuclei

NASA Astrophysics Data System (ADS)

Scopetta, Sergio; Del Dotto, Alessio; Kaptari, Leonid; Pace, Emanuele; Rinaldi, Matteo; Salmè, Giovanni

2018-03-01

Two promising directions beyond inclusive deep inelastic scattering experiments, aimed at unveiling the three dimensional structure of the bound nucleon, are reviewed, considering in particular the 3He nuclear target. The 3D structure in coordinate space can be accessed through deep exclusive processes, whose non-perturbative part is encoded in generalized parton distributions. In this way, the distribution of partons in the transverse plane can be obtained. As an example of a deep exclusive process, coherent deeply virtual Compton scattering off 3He nuclei, important to access the neutron generalized parton distributions (GPDs), will be discussed. In Impulse Approximation (IA), the sum of the two leading twist, quark helicity conserving GPDs of 3He, H and E, at low momentum transfer, turns out to be dominated by the neutron contribution. Besides, a technique, able to take into account the nuclear effects included in the Impulse Approximation analysis, has been developed. The spin dependent GPD \\tilde H of 3He is also found to be largely dominated, at low momentum transfer, by the neutron contribution. The knowledge of the GPDs H,E and \\tilde H of 3He is relevant for the planning of coherent DVCS off 3He measurements. Semi-inclusive deep inelastic scattering processes access the momentum space 3D structure parameterized through transverse momentum dependent parton distributions. A distorted spin-dependent spectral function has been recently introduced for 3He, in a non-relativistic framework, to take care of the final state interaction between the observed pion and the remnant in semi-inclusive deep inelastic electron scattering off transversely polarized 3He. The calculation of the Sivers and Collins single spin asymmetries for 3He, and a straightforward procedure to effectively take into account nuclear dynamics and final state interactions, will be reviewed. The Light-front dynamics generalization of the analysis is also addressed.

Stability limits and defect dynamics in Ag nanoparticles probed by Bragg coherent diffractive imaging

DOE PAGES

Liu, Y.; Lopes, P. P.; Cha, W.; ...

2017-02-10

Dissolution is critical to nanomaterial stability, especially for partially dealloyed nanoparticle catalysts. Unfortunately, highly active catalysts are often not stable in their reactive environments, preventing widespread application. Thus, focusing on the structure–stability relationship at the nanoscale is crucial and will likely play an important role in meeting grand challenges. Recent advances in imaging capability have come from electron, X-ray, and other techniques but tend to be limited to specific sample environments and/or two-dimensional images. Here, we report investigations into the defect-stability relationship of silver nanoparticles to voltage-induced electrochemical dissolution imaged in situ in three dimensional detail by Bragg coherent diffractivemore » imaging. We first determine the average dissolution kinetics by stationary probe rotating disk electrode in combination with inductively coupled plasma mass spectrometry, which allows in situ measurement of Ag+ ion formation. We then observe the dissolution and redeposition processes in single nanocrystals, providing unique insight about the role of surface strain, defects, and their coupling to the dissolution chemistry. Finally, the methods developed and the knowledge gained go well beyond a “simple” silver electrochemistry and are applicable to all electrocatalytic reactions where functional links between activity and stability are controlled by structure and defect dynamics.« less

High-resolution contrast-enhanced optical coherence tomography in mice retinae

NASA Astrophysics Data System (ADS)

Sen, Debasish; SoRelle, Elliott D.; Liba, Orly; Dalal, Roopa; Paulus, Yannis M.; Kim, Tae-Wan; Moshfeghi, Darius M.; de la Zerda, Adam

2016-06-01

Optical coherence tomography (OCT) is a noninvasive interferometric imaging modality providing anatomical information at depths of millimeters and a resolution of micrometers. Conventional OCT images limit our knowledge to anatomical structures alone, without any contrast enhancement. Therefore, here we have, for the first time, optimized an OCT-based contrast-enhanced imaging system for imaging single cells and blood vessels in vivo inside the living mouse retina at subnanomolar sensitivity. We used bioconjugated gold nanorods (GNRs) as exogenous OCT contrast agents. Specifically, we used anti-mouse CD45 coated GNRs to label mouse leukocytes and mPEG-coated GNRs to determine sensitivity of GNR detection in vivo inside mice retinae. We corroborated OCT observations with hyperspectral dark-field microscopy of formalin-fixed histological sections. Our results show that mouse leukocytes that otherwise do not produce OCT contrast can be labeled with GNRs leading to significant OCT intensity equivalent to a 0.5 nM GNR solution. Furthermore, GNRs injected intravenously can be detected inside retinal blood vessels at a sensitivity of ˜0.5 nM, and GNR-labeled cells injected intravenously can be detected inside retinal capillaries by enhanced OCT contrast. We envision the unprecedented resolution and sensitivity of functionalized GNRs coupled with OCT to be adopted for longitudinal studies of retinal disorders.

The right hemisphere's contribution to discourse processing: A study in temporal lobe epilepsy.

PubMed

Lomlomdjian, Carolina; Múnera, Claudia P; Low, Daniel M; Terpiluk, Verónica; Solís, Patricia; Abusamra, Valeria; Kochen, Silvia

2017-08-01

Discourse skills - in which the right hemisphere has an important role - enables verbal communication by selecting contextually relevant information and integrating it coherently to infer the correct meaning. However, language research in epilepsy has focused on single word analysis related mainly to left hemisphere processing. The purpose of this study was to investigate discourse abilities in patients with right lateralized medial temporal lobe epilepsy (RTLE) by comparing their performance to that of patients with left temporal lobe epilepsy (LTLE). 74 pharmacoresistant temporal lobe epilepsy (TLE) patients were evaluated: 34 with RTLE and 40 with LTLE. Subjects underwent a battery of tests that measure comprehension and production of conversational and narrative discourse. Disease related variables and general neuropsychological data were evaluated. The RTLE group presented deficits in interictal conversational and narrative discourse, with a disintegrated speech, lack of categorization and misinterpretation of social meaning. LTLE group, on the other hand, showed a tendency to lower performance in logical-temporal sequencing. RTLE patients showed discourse deficits which have been described in right hemisphere damaged patients due to other etiologies. Medial and anterior temporal lobe structures appear to link semantic, world knowledge, and social cognition associated areas to construct a contextually related coherent meaning. Copyright © 2017 Elsevier Inc. All rights reserved.

Using optical coherence tomography to rapidly phenotype and quantify congenital heart defects associated with prenatal alcohol exposure

PubMed Central

Karunamuni, Ganga; Gu, Shi; Doughman, Yong Qiu; Noonan, Amanda I.; Rollins, Andrew M.; Jenkins, Michael W.; Watanabe, Michiko

2014-01-01

Background The most commonly used method to analyze congenital heart defects involves serial sectioning and histology. However, this is often a time-consuming process where the quantification of cardiac defects can be difficult due to problems with accurate section registration. Here we demonstrate the advantages of using optical coherence tomography, a comparatively new and rising technology, to phenotype avian embryo hearts in a model of Fetal Alcohol Syndrome where a binge-like quantity of alcohol/ethanol was introduced at gastrulation. Results The rapid, consistent imaging protocols allowed for the immediate identification of cardiac anomalies, including ventricular septal defects and misaligned/missing vessels. Interventricular septum thicknesses and vessel diameters for three of the five outflow arteries were also significantly reduced. Outflow and atrio-ventricular valves were segmented using image processing software and had significantly reduced volumes compared to controls. This is the first study to our knowledge that has 3-D reconstructed the late-stage cardiac valves in precise detail in order to examine their morphology and dimensions. Conclusion We believe therefore that OCT, with its ability to rapidly image and quantify tiny embryonic structures in high resolution, will serve as an excellent and cost-effective preliminary screening tool for developmental biologists working with a variety of experimental/disease models. PMID:25546089

Stability limits and defect dynamics in Ag nanoparticles probed by Bragg coherent diffractive imaging

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, Y.; Lopes, P. P.; Cha, W.

Dissolution is critical to nanomaterial stability, especially for partially dealloyed nanoparticle catalysts. Unfortunately, highly active catalysts are often not stable in their reactive environments, preventing widespread application. Thus, focusing on the structure–stability relationship at the nanoscale is crucial and will likely play an important role in meeting grand challenges. Recent advances in imaging capability have come from electron, X-ray, and other techniques but tend to be limited to specific sample environments and/or two-dimensional images. Here, we report investigations into the defect-stability relationship of silver nanoparticles to voltage-induced electrochemical dissolution imaged in situ in three dimensional detail by Bragg coherent diffractivemore » imaging. We first determine the average dissolution kinetics by stationary probe rotating disk electrode in combination with inductively coupled plasma mass spectrometry, which allows in situ measurement of Ag+ ion formation. We then observe the dissolution and redeposition processes in single nanocrystals, providing unique insight about the role of surface strain, defects, and their coupling to the dissolution chemistry. Finally, the methods developed and the knowledge gained go well beyond a “simple” silver electrochemistry and are applicable to all electrocatalytic reactions where functional links between activity and stability are controlled by structure and defect dynamics.« less

Coupling fine-scale root and canopy structure using ground-based remote sensing

DOE PAGES

Hardiman, Brady S.; Gough, Christopher M.; Butnor, John R.; ...

2017-02-21

Ecosystem physical structure, defined by the quantity and spatial distribution of biomass, influences a range of ecosystem functions. Remote sensing tools permit the non-destructive characterization of canopy and root features, potentially providing opportunities to link above- and belowground structure at fine spatial resolution in functionally meaningful ways. To test this possibility, we employed ground-based portable canopy LiDAR (PCL) and ground penetrating radar (GPR) along co-located transects in forested sites spanning multiple stages of ecosystem development and, consequently, of structural complexity. We examined canopy and root structural data for coherence (i.e., correlation in the frequency of spatial variation) at multiple spatialmore » scales 10 m within each site using wavelet analysis. Forest sites varied substantially in vertical canopy and root structure, with leaf area index and root mass more becoming even vertically as forests aged. In all sites, above- and belowground structure, characterized as mean maximum canopy height and root mass, exhibited significant coherence at a scale of 3.5–4 m, and results suggest that the scale of coherence may increase with stand age. Our findings demonstrate that canopy and root structure are linked at characteristic spatial scales, which provides the basis to optimize scales of observation. Lastly, our study highlights the potential, and limitations, for fusing LiDAR and radar technologies to quantitatively couple above- and belowground ecosystem structure.« less

Coupling fine-scale root and canopy structure using ground-based remote sensing

DOE Office of Scientific and Technical Information (OSTI.GOV)

Hardiman, Brady S.; Gough, Christopher M.; Butnor, John R.

Ecosystem physical structure, defined by the quantity and spatial distribution of biomass, influences a range of ecosystem functions. Remote sensing tools permit the non-destructive characterization of canopy and root features, potentially providing opportunities to link above- and belowground structure at fine spatial resolution in functionally meaningful ways. To test this possibility, we employed ground-based portable canopy LiDAR (PCL) and ground penetrating radar (GPR) along co-located transects in forested sites spanning multiple stages of ecosystem development and, consequently, of structural complexity. We examined canopy and root structural data for coherence (i.e., correlation in the frequency of spatial variation) at multiple spatialmore » scales 10 m within each site using wavelet analysis. Forest sites varied substantially in vertical canopy and root structure, with leaf area index and root mass more becoming even vertically as forests aged. In all sites, above- and belowground structure, characterized as mean maximum canopy height and root mass, exhibited significant coherence at a scale of 3.5–4 m, and results suggest that the scale of coherence may increase with stand age. Our findings demonstrate that canopy and root structure are linked at characteristic spatial scales, which provides the basis to optimize scales of observation. Lastly, our study highlights the potential, and limitations, for fusing LiDAR and radar technologies to quantitatively couple above- and belowground ecosystem structure.« less

Facilitating Coherence across Qualitative Research Papers

ERIC Educational Resources Information Center

Chenail, Ronald J.; Duffy, Maureen; St. George, Sally; Wulff, Dan

2011-01-01

Bringing the various elements of qualitative research papers into coherent textual patterns presents challenges for authors and editors alike. Although individual sections such as presentation of the problem, review of the literature, methodology, results, and discussion may each be constructed in a sound logical and structural sense, the…

Tomographic PIV investigation on coherent vortex structures over shark-skin-inspired drag-reducing riblets

NASA Astrophysics Data System (ADS)

Yang, Shao-Qiong; Li, Shan; Tian, Hai-Ping; Wang, Qing-Yi; Jiang, Nan

2016-04-01

Nature has shown us that the microstructure of the skin of fast-swimming sharks in the ocean can reduce the skin friction drag due to the well-known shark-skin effect. In the present study, the effect of shark-skin-inspired riblets on coherent vortex structures in a turbulent boundary layer (TBL) is investigated. This is done by means of tomographic particle image velocimetry (TPIV) measurements in channel flows over an acrylic plate of drag-reducing riblets at a friction Reynolds number of 190. The turbulent flows over drag-reducing riblets are verified by a planar time-resolved particle image velocimetry (TRPIV) system initially, and then the TPIV measurements are performed. Two-dimensional (2D) experimental results with a drag-reduction rate of around 4.81 % are clearly visible over triangle riblets with a peak-to-peak spacing s+ of 14, indicating from the drag-reducing performance that the buffer layer within the TBL has thickened; the logarithmic law region has shifted upward and the Reynolds shear stress decreased. A comparison of the spatial topological distributions of the spanwise vorticity of coherent vortex structures extracted at different wall-normal heights through the improved quadrant splitting method shows that riblets weaken the amplitudes of the spanwise vorticity when ejection (Q2) and sweep (Q4) events occur at the near wall, having the greatest effect on Q4 events in particular. The so-called quadrupole statistical model for coherent structures in the whole TBL is verified. Meanwhile, their spatial conditional-averaged topological shapes and the spatial scales of quadrupole coherent vortex structures as a whole in the overlying turbulent flow over riblets are changed, suggesting that the riblets dampen the momentum and energy exchange between the regions of near-wall and outer portion of the TBL by depressing the bursting events (Q2 and Q4), thereby reducing the skin friction drag.

Transient quantum coherent effects in the acetylene-filled hollow-core photonic crystal fiber

NASA Astrophysics Data System (ADS)

Stepanov, S.; Rodríguez Casillas, N.; Ocegueda Miramontes, M.; Hernández Hernández, E.

2017-02-01

Low-pressure acetylene in the hollow-core photonic crystal structure fibers is an excellent medium for the room-temperature investigation of the coherent quantum effects in communication wavelength region. Pulsed excitation enables observation of new coherent phenomena like optical nutation or photon echo and evaluation of important temporal characteristics of the light-molecule interactions. We also report original experimental results on the pulsed excitation of the electromagnetically induced transparency in co- and counter-propagation configurations.

Polarization-Dependent Interference of Coherent Scattering from Orthogonal Dipole Moments of a Resonantly Excited Quantum Dot.

PubMed

Chen, Disheng; Lander, Gary R; Solomon, Glenn S; Flagg, Edward B

2017-01-20

Resonant photoluminescence excitation (RPLE) spectra of a neutral InGaAs quantum dot show unconventional line shapes that depend on the detection polarization. We characterize this phenomenon by performing polarization-dependent RPLE measurements and simulating the measured spectra with a three-level quantum model. The spectra are explained by interference between fields coherently scattered from the two fine structure split exciton states, and the measurements enable extraction of the steady-state coherence between the two exciton states.

Silicon photonic integrated circuit swept-source optical coherence tomography receiver with dual polarization, dual balanced, in-phase and quadrature detection.

PubMed

Wang, Zhao; Lee, Hsiang-Chieh; Vermeulen, Diedrik; Chen, Long; Nielsen, Torben; Park, Seo Yeon; Ghaemi, Allan; Swanson, Eric; Doerr, Chris; Fujimoto, James

2015-07-01

Optical coherence tomography (OCT) is a widely used three-dimensional (3D) optical imaging method with many biomedical and non-medical applications. Miniaturization, cost reduction, and increased functionality of OCT systems will be critical for future emerging clinical applications. We present a silicon photonic integrated circuit swept-source OCT (SS-OCT) coherent receiver with dual polarization, dual balanced, in-phase and quadrature (IQ) detection. We demonstrate multiple functional capabilities of IQ polarization resolved detection including: complex-conjugate suppressed full-range OCT, polarization diversity detection, and polarization-sensitive OCT. To our knowledge, this is the first demonstration of a silicon photonic integrated receiver for OCT. The integrated coherent receiver provides a miniaturized, low-cost solution for SS-OCT, and is also a key step towards a fully integrated high speed SS-OCT system with good performance and multi-functional capabilities. With further performance improvement and cost reduction, photonic integrated technology promises to greatly increase penetration of OCT systems in existing applications and enable new applications.

Silicon photonic integrated circuit swept-source optical coherence tomography receiver with dual polarization, dual balanced, in-phase and quadrature detection

PubMed Central

Wang, Zhao; Lee, Hsiang-Chieh; Vermeulen, Diedrik; Chen, Long; Nielsen, Torben; Park, Seo Yeon; Ghaemi, Allan; Swanson, Eric; Doerr, Chris; Fujimoto, James

2015-01-01

Optical coherence tomography (OCT) is a widely used three-dimensional (3D) optical imaging method with many biomedical and non-medical applications. Miniaturization, cost reduction, and increased functionality of OCT systems will be critical for future emerging clinical applications. We present a silicon photonic integrated circuit swept-source OCT (SS-OCT) coherent receiver with dual polarization, dual balanced, in-phase and quadrature (IQ) detection. We demonstrate multiple functional capabilities of IQ polarization resolved detection including: complex-conjugate suppressed full-range OCT, polarization diversity detection, and polarization-sensitive OCT. To our knowledge, this is the first demonstration of a silicon photonic integrated receiver for OCT. The integrated coherent receiver provides a miniaturized, low-cost solution for SS-OCT, and is also a key step towards a fully integrated high speed SS-OCT system with good performance and multi-functional capabilities. With further performance improvement and cost reduction, photonic integrated technology promises to greatly increase penetration of OCT systems in existing applications and enable new applications. PMID:26203382

Misalignment sensitivity in an intra-cavity coherently combined crossed-Porro resonator configuration

NASA Astrophysics Data System (ADS)

Alperovich, Z.; Buchinsky, O.; Greenstein, S.; Ishaaya, A. A.

2017-08-01

We investigate the misalignment sensitivity in a crossed-Porro resonator configuration when coherently combining two pulsed multimode Nd:YAG laser channels. To the best of our knowledge, this is the first reported study of this configuration. The configuration is based on a passive intra-cavity interferometric combiner that promotes self-phase locking and coherent combining. Detailed misalignment sensitivity measurements are presented, examining both translation and angular deviations of the end prisms and combiner, and are compared to the results for standard flat end-mirror configurations. The results show that the most sensitive parameter in the crossed-Porro resonator configuration is the angular tuning of the intra-cavity interferometric combiner, which is ~±54 µrad. In comparison, with the flat end mirror configuration, the most sensitive parameter in the resonator is the angular tuning of the output coupler, which is ~±11 µrad. Thus, with the crossed-Porro configuration, we obtain significantly reduced sensitivity. This ability to reduce the misalignment sensitivity in coherently combined solid-state configurations may be beneficial in paving their way into practical use in a variety of demanding applications.

Detection and analysis of diamond fingerprinting feature and its application

NASA Astrophysics Data System (ADS)

Li, Xin; Huang, Guoliang; Li, Qiang; Chen, Shengyi

2011-01-01

Before becoming a jewelry diamonds need to be carved artistically with some special geometric features as the structure of the polyhedron. There are subtle differences in the structure of this polyhedron in each diamond. With the spatial frequency spectrum analysis of diamond surface structure, we can obtain the diamond fingerprint information which represents the "Diamond ID" and has good specificity. Based on the optical Fourier Transform spatial spectrum analysis, the fingerprinting identification of surface structure of diamond in spatial frequency domain was studied in this paper. We constructed both the completely coherent diamond fingerprinting detection system illuminated by laser and the partially coherent diamond fingerprinting detection system illuminated by led, and analyzed the effect of the coherence of light source to the diamond fingerprinting feature. We studied rotation invariance and translation invariance of the diamond fingerprinting and verified the feasibility of real-time and accurate identification of diamond fingerprint. With the profit of this work, we can provide customs, jewelers and consumers with a real-time and reliable diamonds identification instrument, which will curb diamond smuggling, theft and other crimes, and ensure the healthy development of the diamond industry.

Neuronal bases of structural coherence in contemporary dance observation.

PubMed

Bachrach, Asaf; Jola, Corinne; Pallier, Christophe

2016-01-01

The neuronal processes underlying dance observation have been the focus of an increasing number of brain imaging studies over the past decade. However, the existing literature mainly dealt with effects of motor and visual expertise, whereas the neural and cognitive mechanisms that underlie the interpretation of dance choreographies remained unexplored. Hence, much attention has been given to the action observation network (AON) whereas the role of other potentially relevant neuro-cognitive mechanisms such as mentalizing (theory of mind) or language (narrative comprehension) in dance understanding is yet to be elucidated. We report the results of an fMRI study where the structural coherence of short contemporary dance choreographies was manipulated parametrically using the same taped movement material. Our participants were all trained dancers. The whole-brain analysis argues that the interpretation of structurally coherent dance phrases involves a subpart (superior parietal) of the AON as well as mentalizing regions in the dorsomedial prefrontal cortex. An ROI analysis based on a similar study using linguistic materials (Pallier et al., 2011) suggests that structural processing in language and dance might share certain neural mechanisms. Copyright © 2015 Elsevier Inc. All rights reserved.

Using hyperbolic Lagrangian coherent structures to investigate vortices in bioinspired fluid flows

PubMed Central

Green, Melissa A.; Rowley, Clarence W.; Smits, Alexander J.

2010-01-01

We use direct Lyapunov exponents to identify Lagrangian coherent structures (LCSs) in a bioinspired fluid flow: the wakes of rigid pitching panels with a trapezoidal planform geometry chosen to model idealized fish caudal fins. When compared with commonly used Eulerian criteria, the Lagrangian method has previously exhibited the ability to define structure boundaries without relying on a preselected threshold. In addition, qualitative changes in the LCS have previously been shown to correspond to physical changes in the vortex structure. For this paper, digital particle image velocimetry experiments were performed to obtain the time-resolved velocity fields for Strouhal numbers of 0.17 and 0.27. A classic reverse von Kármán vortex street pattern was observed along the midspan of the near wake at low Strouhal number, but at higher Strouhal number the complexity of the wake increased downstream of the trailing edge. The spanwise vortices spread transversely across the wake and lose coherence, and this event was shown to correspond to a qualitative change in the LCS at the same time and location. PMID:20370300

Intermittent nature of acceleration in near wall turbulence.

PubMed

Lee, Changhoon; Yeo, Kyongmin; Choi, Jung-Il

2004-04-09

Using direct numerical simulation of a fully developed turbulent channel flow, we investigate the behavior of acceleration near a solid wall. We find that acceleration near the wall is highly intermittent and the intermittency is in large part associated with the near wall organized coherent turbulence structures. We also find that acceleration of large magnitude is mostly directed towards the rotation axis of the coherent vortical structures, indicating that the source of the intermittent acceleration is the rotational motion associated with the vortices that causes centripetal acceleration.

Big Data: The Future of Biocuration

USDA-ARS?s Scientific Manuscript database

This report is a white paper that describes the roles of biocurators in linking biologists to their data. Roles include: to extract knowledge from published papers; to connect information from different sources in a coherent and comprehensible way; to inspect and correct automatically predicted gene...

Wavelet tree structure based speckle noise removal for optical coherence tomography

NASA Astrophysics Data System (ADS)

Yuan, Xin; Liu, Xuan; Liu, Yang

2018-02-01

We report a new speckle noise removal algorithm in optical coherence tomography (OCT). Though wavelet domain thresholding algorithms have demonstrated superior advantages in suppressing noise magnitude and preserving image sharpness in OCT, the wavelet tree structure has not been investigated in previous applications. In this work, we propose an adaptive wavelet thresholding algorithm via exploiting the tree structure in wavelet coefficients to remove the speckle noise in OCT images. The threshold for each wavelet band is adaptively selected following a special rule to retain the structure of the image across different wavelet layers. Our results demonstrate that the proposed algorithm outperforms conventional wavelet thresholding, with significant advantages in preserving image features.

A review of quasi-coherent structures in a numerically simulated turbulent boundary layer

NASA Technical Reports Server (NTRS)

Robinson, S. K.; Kline, S. J.; Spalart, P. R.

1989-01-01

Preliminary results of a comprehensive study of the structural aspects of a numerically simulated number turbulent boundary layer are presented. A direct Navier-Stokes simulation of a flat-plate, zero pressure gradient boundary layer at Re0 = 670 was used. Most of the known nonrandom, coherent features of turbulent boundary layers are confirmed in the simulation, and several new aspects of their spatial character are reported. The spatial relationships between many of the various structures are described, forming the basis for a more complete kinematical picture of boundary layer physics than has been previously known. In particular, the importance of vortex structures of various forms to the generation of Reynolds shear stress is investigated.

Inverse problems and coherence

NASA Astrophysics Data System (ADS)

Baltes, H. P.; Ferwerda, H. A.

1981-03-01

A summary of current inverse problems of statistical optics is presented together with a short guide to the pertinent review-type literature. The retrieval of structural information from the far-zone degree of coherence and the average intensity distribution of radiation scattered by a superposition of random and periodic scatterers is discussed.

Conversational Coherency. Technical Report No. 95.

ERIC Educational Resources Information Center

Reichman, Rachel

To analyze the process involved in maintaining conversational coherency, the study described in this paper used a construct called a "context space" that grouped utterances referring to a single issue or episode. The paper defines the types of context spaces, parses individual conversations to identify the underlying model or structure,…

SENSITIVITY AND SPECIFICITY OF DETECTING POLYPOIDAL CHOROIDAL VASCULOPATHY WITH EN FACE OPTICAL COHERENCE TOMOGRAPHY AND OPTICAL COHERENCE TOMOGRAPHY ANGIOGRAPHY.

PubMed

de Carlo, Talisa E; Kokame, Gregg T; Kaneko, Kyle N; Lian, Rebecca; Lai, James C; Wee, Raymond

2018-03-20

Determine sensitivity and specificity of polypoidal choroidal vasculopathy (PCV) diagnosis with structural en face optical coherence tomography (OCT) and OCT angiography (OCTA). Retrospective review of the medical records of eyes diagnosed with PCV by indocyanine green angiography with review of diagnostic testing with structural en face OCT and OCTA by a trained reader. Structural en face OCT, cross-sectional OCT angiograms alone, and OCTA in its entirety were reviewed blinded to the findings of indocyanine green angiography and each other to determine if they could demonstrate the PCV complex. Sensitivity and specificity of PCV diagnosis was determined for each imaging technique using indocyanine green angiography as the ground truth. Sensitivity and specificity of structural en face OCT were 30.0% and 85.7%, of OCT angiograms alone were 26.8% and 96.8%, and of the entire OCTA were 43.9% and 87.1%, respectively. Sensitivity and specificity were improved for OCT angiograms and OCTA when looking at images taken within 1 month of PCV diagnosis. Sensitivity of detecting PCV was low using structural en face OCT and OCTA but specificity was high. Indocyanine green angiography remains the gold standard for PCV detection.

Elliptic jets, part 2. Dynamics of coherent structures: Pairing

NASA Technical Reports Server (NTRS)

Husain, Hyder S.; Hussain, Fazle

1992-01-01

The dynamics of the jet column mode of vortex pairing in the near field of an elliptic jet was investigated. Hot-wire measurements and flow visualization were used to examine the details of the pairing mechanism of nonplanar vortical elliptic structures and its effect on such turbulence measures as coherent velocities, incoherent turbulence intensities, incoherent and coherent Reynolds, stresses, turbulence production, and mass entrainment. It was found that pairing of elliptic vortices in the jet column does not occur uniformly around the entire perimeter, unlike in a circular jet. Merger occurs only in the initial major-axis plane. In the initial minor-axis plane, the trailing vortex rushes through the leading vortex without pairing and then breaks down violently, producing considerably greater entrainment and mixing than in circular or plane jets.

A spatial length scale analysis of turbulent temperature and velocity fluctuations within and above an orchard canopy

USGS Publications Warehouse

Wang, Y.S.; Miller, D.R.; Anderson, D.E.; Cionco, R.M.; Lin, J.D.

1992-01-01

Turbulent flow within and above an almond orchard was measured with three-dimensional wind sensors and fine-wire thermocouple sensors arranged in a horizontal array. The data showed organized turbulent structures as indicated by coherent asymmetric ramp patterns in the time series traces across the sensor array. Space-time correlation analysis indicated that velocity and temperature fluctuations were significantly correlated over a transverse distance more than 4m. Integral length scales of velocity and temperature fluctuations were substantially greater in unstable conditions than those in stable conditions. The coherence spectral analysis indicated that Davenport's geometric similarity hypothesis was satisfied in the lower frequency region. From the geometric similarity hypothesis, the spatial extents of large ramp structures were also estimated with the coherence functions.

Application of Soft Computing in Coherent Communications Phase Synchronization

NASA Technical Reports Server (NTRS)

Drake, Jeffrey T.; Prasad, Nadipuram R.

2000-01-01

The use of soft computing techniques in coherent communications phase synchronization provides an alternative to analytical or hard computing methods. This paper discusses a novel use of Adaptive Neuro-Fuzzy Inference Systems (ANFIS) for phase synchronization in coherent communications systems utilizing Multiple Phase Shift Keying (MPSK) modulation. A brief overview of the M-PSK digital communications bandpass modulation technique is presented and it's requisite need for phase synchronization is discussed. We briefly describe the hybrid platform developed by Jang that incorporates fuzzy/neural structures namely the, Adaptive Neuro-Fuzzy Interference Systems (ANFIS). We then discuss application of ANFIS to phase estimation for M-PSK. The modeling of both explicit, and implicit phase estimation schemes for M-PSK symbols with unknown structure are discussed. Performance results from simulation of the above scheme is presented.

Improvement in ultraviolet based decontamination rate using meta-materials

NASA Astrophysics Data System (ADS)

Enaki, Nicolae A.; Bazgan, Sergiu; Ciobanu, Nellu; Turcan, Marina; Paslari, Tatiana; Ristoscu, Carmen; Vaseashta, Ashok; Mihailescu, Ion N.

2017-09-01

We propose a method of decontamination using photon-crystals consisting of microspheres and fiber optics structures with various geometries. The efficient decontamination using the surface of the evanescent zone of meta-materials opens a new perspective in the decontamination procedures. We propose different topological structures of meta-materials to increase the contact surface of UV radiation with contaminated liquid. Recent observation of the trapping of dielectric particles along the fibers help us propose a new perspective on the new possibilities to trap the viruses, bacteria and other microorganisms from liquids, in this special zone, where the effective UV coherent Raman decontamination becomes possible. The nonlinear theory of the excitation of vibration modes of bio-molecule of viruses and bacteria is revised, taking into consideration the bimodal coherent states in coherent Raman excitation of biomolecules.

In vivo photothermal optical coherence tomography of gold nanorods in the mouse eye (Conference Presentation)

NASA Astrophysics Data System (ADS)

Lapierre-Landry, Maryse; Gordon, Andrew Y.; Penn, John S.; Skala, Melissa C.

2017-02-01

Optical coherence tomography (OCT) has become standard in retinal imaging at the pre-clinical and clinical level by allowing non-invasive, three-dimensional imaging of the tissue structure. However, OCT lacks specificity to contrast agents that could be used for in vivo molecular imaging. We have performed in vivo photothermal optical coherence tomography (PT-OCT) of targeted gold nanorods in the mouse retina after the mice were injected systemically with the contrast agent. To our knowledge, we are the first to perform PT-OCT in the eye and image targeted gold nanorods with this technology. As a model of age-related wet macular degeneration, lesions were induced by laser photocoagulation in each mouse retina (n=12 eyes). Untargeted and targeted (anti-mouse CD102 antibody, labeling neovasculature) gold nanorods (peak absorption λ=750nm) were injected intravenously by tail-vein injection five days after lesion induction, and imaged the same day with PT-OCT. Our instrument is a spectral domain OCT system (λ=860nm) with a Titanium:Sapphire laser (λ=750nm) added to the beam path using a 50:50 coupler to heat the gold nanorods. We acquired PT-OCT volumes of one lesion per mouse eye. There was a significant increase in photothermal intensity per unit area of the lesion in the targeted gold nanorods group versus the saline control group and the untargeted gold nanorods group. This experiment demonstrates the feasibility of PT-OCT to image the distribution of molecular contrast agents in the mouse retina, including in highly scattering lesions. In the future we will use this method to identify new biomarkers linked with retinal disease.

Evaluation of partial coherence correction in X-ray ptychography

DOE PAGES

Burdet, Nicolas; Shi, Xiaowen; Parks, Daniel; ...

2015-02-23

Coherent X-ray Diffraction Imaging (CDI) and X-ray ptychography both heavily rely on the high degree of spatial coherence of the X-ray illumination for sufficient experimental data quality for reconstruction convergence. Nevertheless, the majority of the available synchrotron undulator sources have a limited degree of partial coherence, leading to reduced data quality and a lower speckle contrast in the coherent diffraction patterns. It is still an open question whether experimentalists should compromise the coherence properties of an X-ray source in exchange for a higher flux density at a sample, especially when some materials of scientific interest are relatively weak scatterers. Amore » previous study has suggested that in CDI, the best strategy for the study of strong phase objects is to maintain a high degree of coherence of the illuminating X-rays because of the broadening of solution space resulting from the strong phase structures. In this article, we demonstrate the first systematic analysis of the effectiveness of partial coherence correction in ptychography as a function of the coherence properties, degree of complexity of illumination (degree of phase diversity of the probe) and sample phase complexity. We have also performed analysis of how well ptychographic algorithms refine X-ray probe and complex coherence functions when those variables are unknown at the start of reconstructions, for noise-free simulated data, in the case of both real-valued and highly-complex objects.« less

Inter-hemispheric Functional Connectivity Changes with Corpus Callosum Morphology in Multiple Sclerosis

PubMed Central

Zito, Giancarlo; Luders, Eileen; Tomasevic, Leo; Lupoi, Domenico; Toga, Arthur W.; Thompson, Paul M.; Rossini, Paolo M.; Filippi, Maria M.; Tecchio, Franca

2014-01-01

Multiple sclerosis (MS) affects myelin sheaths within the central nervous system, concurring to cause brain atrophy and neurodegeneration as well as gradual functional disconnections. To explore early signs of altered connectivity in MS from a structural and functional perspective, the morphology of corpus callosum (CC) was correlated with a dynamic inter-hemispheric connectivity index. Twenty mildly disabled patients affected by a relapsing-remitting (RR) form of MS (EDSS ≤ 3.5) and 15 healthy subjects underwent structural MRI to measure CC thickness over 100 sections and electroencephalography to assess a spectral coherence index between primary regions devoted to hand control, at rest and during an isometric handgrip. In patients, an overall CC atrophy was associated with increased lesion load. A less efficacious inter-hemispheric coherence during movement was associated with CC atrophy in sections interconnecting homologous primary motor areas (anterior mid-body). In healthy controls, less efficacious inter-hemispheric coherence at rest was associated with a thinner CC splenium. Our data suggest that in mildly disabled RR-MS patients a covert impairment may be detected in the correlation between the structural (CC thickness) and functional (inter-hemispheric coherence) measures of homologous networks, whereas these two counterparts do not yet differ individually from controls. PMID:24486438

Plasmonic antennas as design elements for coherent ultrafast nanophotonics.

PubMed

Brinks, Daan; Castro-Lopez, Marta; Hildner, Richard; van Hulst, Niek F

2013-11-12

Broadband excitation of plasmons allows control of light-matter interaction with nanometric precision at femtosecond timescales. Research in the field has spiked in the past decade in an effort to turn ultrafast plasmonics into a diagnostic, microscopy, computational, and engineering tool for this novel nanometric-femtosecond regime. Despite great developments, this goal has yet to materialize. Previous work failed to provide the ability to engineer and control the ultrafast response of a plasmonic system at will, needed to fully realize the potential of ultrafast nanophotonics in physical, biological, and chemical applications. Here, we perform systematic measurements of the coherent response of plasmonic nanoantennas at femtosecond timescales and use them as building blocks in ultrafast plasmonic structures. We determine the coherent response of individual nanoantennas to femtosecond excitation. By mixing localized resonances of characterized antennas, we design coupled plasmonic structures to achieve well-defined ultrafast and phase-stable field dynamics in a predetermined nanoscale hotspot. We present two examples of the application of such structures: control of the spectral amplitude and phase of a pulse in the near field, and ultrafast switching of mutually coherent hotspots. This simple, reproducible and scalable approach transforms ultrafast plasmonics into a straightforward tool for use in fields as diverse as room temperature quantum optics, nanoscale solid-state physics, and quantum biology.

Optimal laser pulse design for transferring the coherent nuclear wave packet of H+2

NASA Astrophysics Data System (ADS)

Zhang, Jun; He, Guang-Qiang; He, Feng

2014-07-01

Within the Franck-Condon approximation, the single ionisation of H2 leaves H+2 in a coherent superposition of 19 nuclear vibrational states. We numerically design an optimal laser pulse train to transfer such a coherent nuclear wave packet to the ground vibrational state of H+2. Frequency analysis of the designed optimal pulse reveals that the transfer principle is mainly an anti-Stokes transition, i.e. the H+2 in 1sσg with excited nuclear vibrational states is first pumped to 2pσg state by the pulse at an appropriate time, and then dumped back to 1sσg with lower excited or ground vibrational states. The simulation results show that the population of the ground state after the transfer is more than 91%. To the best of our knowledge, this is the highest transition probability when the driving laser field is dozens of femtoseconds.

Cognitive flexibility in young children: General or task-specific capacity?

PubMed

Deák, Gedeon O; Wiseheart, Melody

2015-10-01

Cognitive flexibility is the ability to adapt to changing tasks or problems. To test whether cognitive flexibility is a coherent cognitive capacity in young children, we tested 3- to 5-year-olds' performance on two forms of task switching, rule-based (Three Dimension Changes Card Sorting, 3DCCS) and inductive (Flexible Induction of Meaning-Animates and Objects, FIM-Ob and FIM-An), as well as tests of response speed, verbal working memory, inhibition, and reasoning. Results suggest that cognitive flexibility is not a globally coherent trait; only the two inductive word-meaning (FIM) tests showed high inter-test coherence. Task- and knowledge-specific factors also determine children's flexibility in a given test. Response speed, vocabulary size, and causal reasoning skills further predicted individual and age differences in flexibility, although they did not have the same predictive relation with all three flexibility tests. Copyright © 2015 Elsevier Inc. All rights reserved.

Linking Sediment Transport to Coherent Flow Structures: First Results Using 2-Phase PIV and Considerations of the Origin of Large-Scale Turbulence

NASA Astrophysics Data System (ADS)

Best, J.

2004-05-01

The origin and scaling of large-scale coherent flow structures has been of central interest in furthering understanding of the nature of turbulent boundary layers, and recent work has shown the presence of large-scale turbulent flow structures that may extend through the whole flow depth. Such structures may dominate the entrainment of bedload sediment and advection of fine sediment in suspension. However, we still know remarkably little of the interactions between the dynamics of coherent flow structures and sediment transport, and its implications for ecosystem dynamics. This paper will discuss the first results of two-phase particle imaging velocimetry (PIV) that has been used to visualize large-scale turbulent flow structures moving over a flat bed in a water channel, and the motion of sand particles within these flows. The talk will outline the methodology, involving the fluorescent tagging of sediment and its discrimination from the fluid phase, and show results that illustrate the key role of these large-scale structures in the transport of sediment. Additionally, the presence of these structures will be discussed in relation to the origin of vorticity within flat-bed boundary layers and recent models that envisage these large-scale motions as being linked to whole-flow field structures. Discussion will focus on if these recent models simply reflect the organization of turbulent boundary layer structure and vortex packets, some of which are amply visualised at the laminar-turbulent transition.

Optical coherence tomography platforms and parameters for glaucoma diagnosis and progression.

PubMed

Mwanza, Jean-Claude; Budenz, Donald L

2016-03-01

Optical coherence tomography (OCT) aids in the diagnosis and long-term monitoring of various ocular diseases, including glaucoma. Initially, the retinal nerve fiber layer was the only OCT structural parameter used in glaucoma. Subsequent research has resulted in more retinal and optic nerve head parameters. In addition, OCT is being investigated for its ability to assess ocular hemodynamics. This review summarizes these spectral domain-optical coherence tomography (SDOCT) parameters in the context of glaucoma. Several new SDOCT retinal nerve fiber layer, optic nerve head, and macular parameters with good glaucoma diagnostic ability have been added to existing ones recently. The combination of SDOCT and Doppler or angiography has also resulted in hemodynamic parameters that may prove to be useful in the functional assessment in glaucoma. OCT technology is advancing not only as a tool for structural assessment, but also as a multimodality tool to assess both structure and function to enhance our understanding of glaucoma, and ultimately clinical decisions.

Near-surface coherent structures explored by large eddy simulation of entire tropical cyclones.

PubMed

Ito, Junshi; Oizumi, Tsutao; Niino, Hiroshi

2017-06-19

Taking advantage of the huge computational power of a massive parallel supercomputer (K-supercomputer), this study conducts large eddy simulations of entire tropical cyclones by employing a numerical weather prediction model, and explores near-surface coherent structures. The maximum of the near-surface wind changes little from that simulated based on coarse-resolution runs. Three kinds of coherent structures appeared inside the boundary layer. The first is a Type-A roll, which is caused by an inflection-point instability of the radial flow and prevails outside the radius of maximum wind. The second is a Type-B roll that also appears to be caused by an inflection-point instability but of both radial and tangential winds. Its roll axis is almost orthogonal to the Type-A roll. The third is a Type-C roll, which occurs inside the radius of maximum wind and only near the surface. It transports horizontal momentum in an up-gradient sense and causes the largest gusts.

Fluid theory and simulations of instabilities, turbulent transport and coherent structures in partially-magnetized plasmas of \\mathbf{E}\\times \\mathbf{B} discharges

NASA Astrophysics Data System (ADS)

Smolyakov, A. I.; Chapurin, O.; Frias, W.; Koshkarov, O.; Romadanov, I.; Tang, T.; Umansky, M.; Raitses, Y.; Kaganovich, I. D.; Lakhin, V. P.

2017-01-01

Partially-magnetized plasmas with magnetized electrons and non-magnetized ions are common in Hall thrusters for electric propulsion and magnetron material processing devices. These plasmas are usually in strongly non-equilibrium state due to presence of crossed electric and magnetic fields, inhomogeneities of plasma density, temperature, magnetic field and beams of accelerated ions. Free energy from these sources make such plasmas prone to various instabilities resulting in turbulence, anomalous transport, and appearance of coherent structures as found in experiments. This paper provides an overview of instabilities that exist in such plasmas. A nonlinear fluid model has been developed for description of the Simon-Hoh, lower-hybrid and ion-sound instabilities. The model also incorporates electron gyroviscosity describing the effects of finite electron temperature. The nonlinear fluid model has been implemented in the BOUT++ framework. The results of nonlinear simulations are presented demonstrating turbulence, anomalous current and tendency toward the formation of coherent structures.

Coherent convergent-beam time-resolved X-ray diffraction

PubMed Central

Spence, John C. H.; Zatsepin, Nadia A.; Li, Chufeng

2014-01-01

The use of coherent X-ray lasers for structural biology allows the use of nanometre diameter X-ray beams with large beam divergence. Their application to the structure analysis of protein nanocrystals and single particles raises new challenges and opportunities. We discuss the form of these coherent convergent-beam (CCB) hard X-ray diffraction patterns and their potential use for time-resolved crystallography, normally achieved by Laue (polychromatic) diffraction, for which the monochromatic laser radiation of a free-electron X-ray laser is unsuitable. We discuss the possibility of obtaining single-shot, angle-integrated rocking curves from CCB patterns, and the dependence of the resulting patterns on the focused beam coordinate when the beam diameter is larger or smaller than a nanocrystal, or smaller than one unit cell. We show how structure factor phase information is provided at overlapping interfering orders and how a common phase origin between different shots may be obtained. Their use in refinement of the phase-sensitive intensity between overlapping orders is suggested. PMID:24914153

Lagrangian based methods for coherent structure detection

NASA Astrophysics Data System (ADS)

Allshouse, Michael R.; Peacock, Thomas

2015-09-01

There has been a proliferation in the development of Lagrangian analytical methods for detecting coherent structures in fluid flow transport, yielding a variety of qualitatively different approaches. We present a review of four approaches and demonstrate the utility of these methods via their application to the same sample analytic model, the canonical double-gyre flow, highlighting the pros and cons of each approach. Two of the methods, the geometric and probabilistic approaches, are well established and require velocity field data over the time interval of interest to identify particularly important material lines and surfaces, and influential regions, respectively. The other two approaches, implementing tools from cluster and braid theory, seek coherent structures based on limited trajectory data, attempting to partition the flow transport into distinct regions. All four of these approaches share the common trait that they are objective methods, meaning that their results do not depend on the frame of reference used. For each method, we also present a number of example applications ranging from blood flow and chemical reactions to ocean and atmospheric flows.

Two-photon interference and coherent control of single InAs quantum dot emissions in an Ag-embedded structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liu, X., E-mail: iu.xiangming@nims.go.jp; National Institute for Materials Science, 1-1 Namiki, Tsukuba 305-0044; Kumano, H.

2014-07-28

We have recently reported the successful fabrication of bright single-photon sources based on Ag-embedded nanocone structures that incorporate InAs quantum dots. The source had a photon collection efficiency as high as 24.6%. Here, we show the results of various types of photonic characterizations of the Ag-embedded nanocone structures that confirm their versatility as regards a broad range of quantum optical applications. We measure the first-order autocorrelation function to evaluate the coherence time of emitted photons, and the second-order correlation function, which reveals the strong suppression of multiple photon generation. The high indistinguishability of emitted photons is shown by the Hong-Ou-Mandel-typemore » two-photon interference. With quasi-resonant excitation, coherent population flopping is demonstrated through Rabi oscillations. Extremely high single-photon purity with a g{sup (2)}(0) value of 0.008 is achieved with π-pulse quasi-resonant excitation.« less

Dynamic isoperimetry and the geometry of Lagrangian coherent structures

NASA Astrophysics Data System (ADS)

Froyland, Gary

2015-10-01

The study of transport and mixing processes in dynamical systems is particularly important for the analysis of mathematical models of physical systems. We propose a novel, direct geometric method to identify subsets of phase space that remain strongly coherent over a finite time duration. This new method is based on a dynamic extension of classical (static) isoperimetric problems; the latter are concerned with identifying submanifolds with the smallest boundary size relative to their volume. The present work introduces dynamic isoperimetric problems; the study of sets with small boundary size relative to volume as they are evolved by a general dynamical system. We formulate and prove dynamic versions of the fundamental (static) isoperimetric (in)equalities; a dynamic Federer-Fleming theorem and a dynamic Cheeger inequality. We introduce a new dynamic Laplace operator and describe a computational method to identify coherent sets based on eigenfunctions of the dynamic Laplacian. Our results include formal mathematical statements concerning geometric properties of finite-time coherent sets, whose boundaries can be regarded as Lagrangian coherent structures. The computational advantages of our new approach are a well-separated spectrum for the dynamic Laplacian, and flexibility in appropriate numerical approximation methods. Finally, we demonstrate that the dynamic Laplace operator can be realised as a zero-diffusion limit of a newly advanced probabilistic transfer operator method [9] for finding coherent sets, which is based on small diffusion. Thus, the present approach sits naturally alongside the probabilistic approach [9], and adds a formal geometric interpretation.

Nanometer resolution optical coherence tomography using broad bandwidth XUV and soft x-ray radiation

DOE PAGES

Fuchs, Silvio; Rödel, Christian; Blinne, Alexander; ...

2016-02-10

Optical coherence tomography (OCT) is a non-invasive technique for cross-sectional imaging. It is particularly advantageous for applications where conventional microscopy is not able to image deeper layers of samples in a reasonable time, e.g. in fast moving, deeper lying structures. However, at infrared and optical wavelengths, which are commonly used, the axial resolution of OCT is limited to about 1 μm, even if the bandwidth of the light covers a wide spectral range. Here, we present extreme ultraviolet coherence tomography (XCT) and thus introduce a new technique for non-invasive cross-sectional imaging of nanometer structures. XCT exploits the nanometerscale coherence lengthsmore » corresponding to the spectral transmission windows of, e.g., silicon samples. The axial resolution of coherence tomography is thus improved from micrometers to a few nanometers. Tomographic imaging with an axial resolution better than 18 nm is demonstrated for layer-type nanostructures buried in a silicon substrate. Using wavelengths in the water transmission window, nanometer-scale layers of platinum are retrieved with a resolution better than 8 nm. As a result, XCT as a nondestructive method for sub-surface tomographic imaging holds promise for several applications in semiconductor metrology and imaging in the water window.« less

From coherent to incoherent mismatched interfaces: A generalized continuum formulation of surface stresses

NASA Astrophysics Data System (ADS)

Dingreville, Rémi; Hallil, Abdelmalek; Berbenni, Stéphane

2014-12-01

The equilibrium of coherent and incoherent mismatched interfaces is reformulated in the context of continuum mechanics based on the Gibbs dividing surface concept. Two surface stresses are introduced: a coherent surface stress and an incoherent surface stress, as well as a transverse excess strain. The coherent surface stress and the transverse excess strain represent the thermodynamic driving forces of stretching the interface while the incoherent surface stress represents the driving force of stretching one crystal while holding the other fixed and thereby altering the structure of the interface. These three quantities fully characterize the elastic behavior of coherent and incoherent interfaces as a function of the in-plane strain, the transverse stress and the mismatch strain. The isotropic case is developed in detail and particular attention is paid to the case of interfacial thermo-elasticity. This exercise provides an insight on the physical significance of the interfacial elastic constants introduced in the formulation and illustrates the obvious coupling between the interface structure and its associated thermodynamics quantities. Finally, an example based on atomistic simulations of Cu/Cu2O interfaces is given to demonstrate the relevance of the generalized interfacial formulation and to emphasize the dependence of the interfacial thermodynamic quantities on the incoherency strain with an actual material system.

From coherent to incoherent mismatched interfaces. A generalized continuum formulation of surface stresses

DOE PAGES

Dingreville, Rémi; Hallil, Abdelmalek; Berbenni, Stéphane

2014-08-19

The equilibrium of coherent and incoherent mismatched interfaces is reformulated in the context of continuum mechanics based on the Gibbs dividing surface concept. Two surface stresses are introduced: a coherent surface stress and an incoherent surface stress, as well as a transverse excess strain. Additionally, the coherent surface stress and the transverse excess strain represent the thermodynamic driving forces of stretching the interface while the incoherent surface stress represents the driving force of stretching one crystal while holding the other fixed and thereby altering the structure of the interface. These three quantities fully characterize the elastic behavior of coherent andmore » incoherent interfaces as a function of the in-plane strain, the transverse stress and the mismatch strain. The isotropic case is developed in detail and particular attention is paid to the case of interfacial thermo-elasticity. This exercise provides an insight on the physical significance of the interfacial elastic constants introduced in the formulation and illustrates the obvious coupling between the interface structure and its associated thermodynamics quantities. Finally, an example based on atomistic simulations of Cu/Cu 2O interfaces is given to demonstrate the relevance of the generalized interfacial formulation and to emphasize the dependence of the interfacial thermodynamic quantities on the incoherency strain with an actual material system.« less

Effect of inhibitory firing pattern on coherence resonance in random neural networks

NASA Astrophysics Data System (ADS)

Yu, Haitao; Zhang, Lianghao; Guo, Xinmeng; Wang, Jiang; Cao, Yibin; Liu, Jing

2018-01-01

The effect of inhibitory firing patterns on coherence resonance (CR) in random neuronal network is systematically studied. Spiking and bursting are two main types of firing pattern considered in this work. Numerical results show that, irrespective of the inhibitory firing patterns, the regularity of network is maximized by an optimal intensity of external noise, indicating the occurrence of coherence resonance. Moreover, the firing pattern of inhibitory neuron indeed has a significant influence on coherence resonance, but the efficacy is determined by network property. In the network with strong coupling strength but weak inhibition, bursting neurons largely increase the amplitude of resonance, while they can decrease the noise intensity that induced coherence resonance within the neural system of strong inhibition. Different temporal windows of inhibition induced by different inhibitory neurons may account for the above observations. The network structure also plays a constructive role in the coherence resonance. There exists an optimal network topology to maximize the regularity of the neural systems.

Angular rheology study of colloidal nanocrystals using Coherent X-ray Diffraction

NASA Astrophysics Data System (ADS)

Liang, Mengning; Harder, Ross; Robinson, Ian

2007-03-01

A new method using coherent x-ray diffraction provides a way to investigate the rotational motion of a colloidal suspension of crystals in real time. Coherent x-ray diffraction uses the long coherence lengths of synchrotron sources to illuminate a nanoscale particle coherently over its spatial dimensions. The penetration of high energy x-rays into various media allows for in-situ measurements making it ideal for suspensions. This technique has been used to image the structure of nanocrystals for some time but also has the capability of providing information about the orientation and dynamics of crystals. The particles are imaged in a specific diffraction condition allowing us to determine their orientation and observe how they rotate in real time with exceptional resolution. Such sensitivity allows for the study of rotational Brownian motion of nanocrystals in various suspensions and conditions. We present a study of the angular rheology of alumina and TiO2 colloidal nanocrystals in media using coherent x-ray diffraction.

Polarization-correlation study of biotissue multifractal structure

NASA Astrophysics Data System (ADS)

Olar, O. I.; Ushenko, A. G.

2003-09-01

This paper presents the results of polarization-correlation study of multifractal collagen structure of physiologically normal and pathologically changed tissues of women"s reproductive sphere and skin. The technique of polarization selection of coherent images of biotissues with further determination of their autocorrelation functions and spectral densities is suggested. The correlation-optical criteria of early diagnostics of appearance of pathological changes in the cases of myometry (forming the germ of fibromyoma) and skin (psoriasis) are determined. This study is directed to investigate the possibilities of recognition of pathological changes of biotissue morphological structure by determining the polarization-dependent autocorrelation functions (ACF) and corresponding spectral densities of tissue coherent images.

Polarization-correlation investigation of biotissue multifractal structure and diagnostics of its pathological change

NASA Astrophysics Data System (ADS)

Angelsky, Oleg V.; Pishak, Vasyl P.; Ushenko, Alexander G.; Burkovets, Dimitry N.; Pishak, Olga V.

2001-05-01

The paper presents the results of polarization-correlation investigation of multifractal collagen structure of physiologically normal and pathologically changed tissues of women's reproductive sphere and of skin. The technique of polarization selection of coherent biotissues' images followed by determination of their autocorrelation functions and spectral densities is suggested. The correlation- optical criteria of early diagnostics of pathological changes' appearance of myometry (forming of the germ of fibromyoma) and of skin (psoriasis) are determined. The present paper examines the possibilities of diagnostics of pathological changes of biotissues' morphological structure by means of determining the polarizationally filtered autocorrelation functions (ACF) and corresponding spectral densities of their coherent images.

Coherent structures and dynamical systems

NASA Technical Reports Server (NTRS)

Jimenez, Javier

1987-01-01

Any flow of a viscous fluid has a finite number of degrees of freedom, and can therefore be seen as a dynamical system. A coherent structure can be thought of as a lower dimensional manifold in whose neighborhood the dynamical system spends a substantial fraction of its time. If such a manifold exists, and if its dimensionality is substantially lower that that of the full flow, it is conceivable that the flow could be described in terms of the reduced set of degrees of freedom, and that such a description would be simpler than one in which the existence of structure was not recognized. Several examples are briefly summarized.

Coherent structures and anomalous transport in reversed field pinch plasmas

NASA Astrophysics Data System (ADS)

Antoni, V.; Drake, J. R.; Spada, E.; Spolaore, M.; Vianello, N.; Bergsåker, H.; Cavazzana, R.; Cecconello, M.; Martines, E.; Serianni, G.

2006-02-01

The results leading to the identification of coherent structures emerging from the background turbulence in the edge region of the reversed field pinch experiments EXTRAP-T2R and RFX are reviewed. These structures have traits of vortices in velocity field and blobs in density, and the reconstruction of their spatial structure and of their time evolution is discussed focusing on the analysis tools applied. The role of these structures in the particle anomalous transport is addressed, showing that their collisions can contribute up to 50% the total particle losses.This process is shown to be responsible for bursts in particle flux and it is found to set a characteristic collision time, which is in agreement with the statistical properties of laminar times for particle flux bursts.

Important Questions of Comparative Studies in Asian Countries

ERIC Educational Resources Information Center

Pazyura, Natalia

2015-01-01

The issue of the "identity" of comparative education as a field of study or a discipline has been discussed for decades. Yet a kind of systematic structure that provides the basic principles for a coherent exposition of the field remains open. "Comparative education" is no longer conceived as an imaginary field's coherence but,…

(Pea)nuts and Bolts of Visual Narrative: Structure and Meaning in Sequential Image Comprehension

ERIC Educational Resources Information Center

Cohn, Neil; Paczynski, Martin; Jackendoff, Ray; Holcomb, Phillip J.; Kuperberg, Gina R.

2012-01-01

Just as syntax differentiates coherent sentences from scrambled word strings, the comprehension of sequential images must also use a cognitive system to distinguish coherent narrative sequences from random strings of images. We conducted experiments analogous to two classic studies of language processing to examine the contributions of narrative…

Naturalism and Educational Administration: New Directions

ERIC Educational Resources Information Center

Evers, Colin W.; Lakomski, Gabriele

2015-01-01

The purpose of this paper is to outline some new developments in a mature research program that sees administrative theory as cohering with natural science and uses a coherence theory of epistemic justification to shape the content and structure of administrative theory. Three main developments are discussed. First, the paper shows how to deal…

The Usefulness of a Suggested Paradigm for Improving Paragraph Coherence

ERIC Educational Resources Information Center

Siu, Fiona Kwai-peng

2016-01-01

This study aims to explore the effectiveness of a paradigm to teach native Cantonese-speaking university students the hierarchical structure of expository prose to improve paragraph coherence. Most of the diagnostic argumentative essays the participants in this study wrote in the course were incoherent, failing to meet readers' expectation of…

Zombie states for description of structure and dynamics of multi-electron systems

NASA Astrophysics Data System (ADS)

Shalashilin, Dmitrii V.

2018-05-01

Canonical Coherent States (CSs) of Harmonic Oscillator have been extensively used as a basis in a number of computational methods of quantum dynamics. However, generalising such techniques for fermionic systems is difficult because Fermionic Coherent States (FCSs) require complicated algebra of Grassmann numbers not well suited for numerical calculations. This paper introduces a coherent antisymmetrised superposition of "dead" and "alive" electronic states called here Zombie State (ZS), which can be used in a manner of FCSs but without Grassmann algebra. Instead, for Zombie States, a very simple sign-changing rule is used in the definition of creation and annihilation operators. Then, calculation of electronic structure Hamiltonian matrix elements between two ZSs becomes very simple and a straightforward technique for time propagation of fermionic wave functions can be developed. By analogy with the existing methods based on Canonical Coherent States of Harmonic Oscillator, fermionic wave functions can be propagated using a set of randomly selected Zombie States as a basis. As a proof of principles, the proposed Coupled Zombie States approach is tested on a simple example showing that the technique is exact.

Nano-sized Superlattice Clusters Created by Oxygen Ordering in Mechanically Alloyed Fe Alloys

NASA Astrophysics Data System (ADS)

Hu, Yong-Jie; Li, Jing; Darling, Kristopher A.; Wang, William Y.; Vanleeuwen, Brian K.; Liu, Xuan L.; Kecskes, Laszlo J.; Dickey, Elizabeth C.; Liu, Zi-Kui

2015-07-01

Creating and maintaining precipitates coherent with the host matrix, under service conditions is one of the most effective approaches for successful development of alloys for high temperature applications; prominent examples include Ni- and Co-based superalloys and Al alloys. While ferritic alloys are among the most important structural engineering alloys in our society, no reliable coherent precipitates stable at high temperatures have been found for these alloys. Here we report discovery of a new, nano-sized superlattice (NSS) phase in ball-milled Fe alloys, which maintains coherency with the BCC matrix up to at least 913 °C. Different from other precipitates in ferritic alloys, this NSS phase is created by oxygen-ordering in the BCC Fe matrix. It is proposed that this phase has a chemistry of Fe3O and a D03 crystal structure and becomes more stable with the addition of Zr. These nano-sized coherent precipitates effectively double the strength of the BCC matrix above that provided by grain size reduction alone. This discovery provides a new opportunity for developing high-strength ferritic alloys for high temperature applications.

Zero Quantum Coherence in a Series of Covalent Spin-Correlated Radical Pairs.

PubMed

Nelson, Jordan N; Krzyaniak, Matthew D; Horwitz, Noah E; Rugg, Brandon K; Phelan, Brian T; Wasielewski, Michael R

2017-03-23

Photoinitiated subnanosecond electron transfer within covalently linked electron donor-acceptor molecules can result in the formation of a spin-correlated radical pair (SCRP) with a well-defined initial singlet spin configuration. Subsequent coherent mixing between the SCRP singlet and triplet m s = 0 spin states, the so-called zero quantum coherence (ZQC), is of potential interest in quantum information processing applications because the ZQC can be probed using pulse electron paramagnetic resonance (pulse-EPR) techniques. Here, pulse-EPR spectroscopy is utilized to examine the ZQC oscillation frequencies and ZQC dephasing in three structurally well-defined D-A systems. While transitions between the singlet and triplet m s = 0 spin states are formally forbidden (Δm s = 0), they can be addressed using specific microwave pulse turning angles to map information from the ZQC onto observable single quantum coherences. In addition, by using structural variations to tune the singlet-triplet energy gap, the ZQC frequencies determined for this series of molecules indicate a stronger dependence on the electronic g-factor than on electron-nuclear hyperfine interactions.

Coherent generation of symmetry-forbidden phonons by light-induced electron-phonon interactions in magnetite

NASA Astrophysics Data System (ADS)

Borroni, S.; Baldini, E.; Katukuri, V. M.; Mann, A.; Parlinski, K.; Legut, D.; Arrell, C.; van Mourik, F.; Teyssier, J.; Kozlowski, A.; Piekarz, P.; Yazyev, O. V.; Oleś, A. M.; Lorenzana, J.; Carbone, F.

2017-09-01

Symmetry breaking across phase transitions often causes changes in selection rules and emergence of optical modes which can be detected via spectroscopic techniques or generated coherently in pump-probe experiments. In second-order or weakly first-order transitions, fluctuations of the ordering field are present above the ordering temperature, giving rise to intriguing precursor phenomena, such as critical opalescence. Here, we demonstrate that in magnetite (Fe3O4 ) light excitation couples to the critical fluctuations of the charge order and coherently generates structural modes of the ordered phase above the critical temperature of the Verwey transition. Our findings are obtained by detecting coherent oscillations of the optical constants through ultrafast broadband spectroscopy and analyzing their dependence on temperature. To unveil the coupling between the structural modes and the electronic excitations, at the origin of the Verwey transition, we combine our results from pump-probe experiments with spontaneous Raman scattering data and theoretical calculations of both the phonon dispersion curves and the optical constants. Our methodology represents an effective tool to study the real-time dynamics of critical fluctuations across phase transitions.

Imaging deep skeletal muscle structure using a high-sensitivity ultrathin side-viewing optical coherence tomography needle probe

PubMed Central

Yang, Xiaojie; Lorenser, Dirk; McLaughlin, Robert A.; Kirk, Rodney W.; Edmond, Matthew; Simpson, M. Cather; Grounds, Miranda D.; Sampson, David D.

2013-01-01

We have developed an extremely miniaturized optical coherence tomography (OCT) needle probe (outer diameter 310 µm) with high sensitivity (108 dB) to enable minimally invasive imaging of cellular structure deep within skeletal muscle. Three-dimensional volumetric images were acquired from ex vivo mouse tissue, examining both healthy and pathological dystrophic muscle. Individual myofibers were visualized as striations in the images. Degradation of cellular structure in necrotic regions was seen as a loss of these striations. Tendon and connective tissue were also visualized. The observed structures were validated against co-registered hematoxylin and eosin (H&E) histology sections. These images of internal cellular structure of skeletal muscle acquired with an OCT needle probe demonstrate the potential of this technique to visualize structure at the microscopic level deep in biological tissue in situ. PMID:24466482

Broadband light generation by femtosecond pulse amplification with stimulated Raman scattering in a high-power erbium-doped fiber amplifier

DOE Office of Scientific and Technical Information (OSTI.GOV)

Tamura, K.; Yoshida, E.; Sugawa, T.

1995-08-01

It is shown for the first time to our knowledge that short-pulse amplification in high-power erbium-doped fiber amplifiers, simultaneously accompanied by stimulated Raman scattering, generates a broadband optical spectrum at high output power (270 mW). At 20 dB down from the peak the continuum extended over 329 nm, from 1427 to 1756 nm. The FWHM bandwidth was 125 nm, centered at 1650 nm. The coherence was measured to be 15 fringes, which corresponds to a 25-{mu}m coherence length. {copyright} {ital 1995} {ital Optical} {ital Society} {ital of} {ital America}.

Coherent Backscattering by Polydisperse Discrete Random Media: Exact T-Matrix Results

NASA Technical Reports Server (NTRS)

Mishchenko, Michael I.; Dlugach, Janna M.; Mackowski, Daniel W.

2011-01-01

The numerically exact superposition T-matrix method is used to compute, for the first time to our knowledge, electromagnetic scattering by finite spherical volumes composed of polydisperse mixtures of spherical particles with different size parameters or different refractive indices. The backscattering patterns calculated in the far-field zone of the polydisperse multiparticle volumes reveal unequivocally the classical manifestations of the effect of weak localization of electromagnetic waves in discrete random media, thereby corroborating the universal interference nature of coherent backscattering. The polarization opposition effect is shown to be the least robust manifestation of weak localization fading away with increasing particle size parameter.

Image cloning beyond diffraction based on coherent population trapping in a hot rubidium vapor.

PubMed

Ding, Dong-Sheng; Zhou, Zhi-Yuan; Shi, Bao-Sen

2014-01-15

Following recent theoretical predictions, we report on an experimental realization of image cloning beyond usual diffraction, through the coherent population trapping (CPT) effect in a hot rubidium vapor. In our experiment, an alphabet letter image was transferred from a coupling field to a probe field, based on the CPT effect. Furthermore, we demonstrate that the cloned probe field carrying the image is transmitted without the usual diffraction. To our best knowledge, this is the first experimental report about image cloning beyond diffraction. We believe this mechanism, based on CPT, has definite and important applications in image metrology, image processing, and biomedical imaging.

Assessing school-aged children's inference-making: the effect of story test format in listening comprehension.

PubMed

Freed, Jenny; Cain, Kate

2017-01-01

Comprehension is critical for classroom learning and educational success. Inferences are integral to good comprehension: successful comprehension requires the listener to generate local coherence inferences, which involve integrating information between clauses, and global coherence inferences, which involve integrating textual information with background knowledge to infer motivations, themes, etc. A central priority for the diagnosis of comprehension difficulties and our understanding of why these difficulties arise is the development of valid assessment instruments. We explored typically developing children's ability to make local and global coherence inferences using a novel assessment of listening comprehension. The aims were to determine whether children were more likely to make the target inferences when these were asked during story presentation versus after presentation of the story, and whether there were any age differences between conditions. Children in Years 3 (n = 29) and 5 (n = 31) listened to short stories presented either in a segmented format, in which questions to assess local and global coherence inferences were asked at specific points during story presentation, or in a whole format, when all the questions were asked after the story had been presented. There was developmental progression between age groups for both types of inference question. Children also scored higher on the global coherence inference questions than the local coherence inference questions. There was a benefit of the segmented format for younger children, particularly for the local inference questions. The results suggest that children are more likely to make target inferences if prompted during presentation of the story, and that this format is particularly facilitative for younger children and for local coherence inferences. This has implications for the design of comprehension assessments as well as for supporting children with comprehension difficulties in the classroom. © 2016 Royal College of Speech and Language Therapists.

Low-cost coherent receiver for long-reach optical access network using single-ended detection.

PubMed

Zhang, Xuebing; Li, Zhaohui; Li, Jianping; Yu, Changyuan; Lau, Alan Pak Tao; Lu, Chao

2014-09-15

A low-cost coherent receiver using two 2×3 optical hybrids and single-ended detection is proposed for long-reach optical access network. This structure can detect the two polarization components of polarization division multiplexing (PDM) signals. Polarization de-multiplexing and signal-to-signal beat interference (SSBI) cancellation are realized by using only three photodiodes. Simulation results for 40 Gb/s PDM-OFDM transmissions indicate that the low-cost coherent receiver has 3.2 dB optical signal-to-noise ratio difference compared with the theoretical value.

Identification of muscle necrosis in the mdx mouse model of Duchenne muscular dystrophy using three-dimensional optical coherence tomography

NASA Astrophysics Data System (ADS)

Klyen, Blake R.; Shavlakadze, Thea; Radley-Crabb, Hannah G.; Grounds, Miranda D.; Sampson, David D.

2011-07-01

Three-dimensional optical coherence tomography (3D-OCT) was used to image the structure and pathology of skeletal muscle tissue from the treadmill-exercised mdx mouse model of human Duchenne muscular dystrophy. Optical coherence tomography (OCT) images of excised muscle samples were compared with co-registered hematoxylin and eosin-stained and Evans blue dye fluorescence histology. We show, for the first time, structural 3D-OCT images of skeletal muscle dystropathology well correlated with co-located histology. OCT could identify morphological features of interest and necrotic lesions within the muscle tissue samples based on intrinsic optical contrast. These findings demonstrate the utility of 3D-OCT for the evaluation of small-animal skeletal muscle morphology and pathology, particularly for studies of mouse models of muscular dystrophy.

Pragmatics in discourse performance: insights from aphasiology.

PubMed

Ulatowska, Hanna K; Olness, Gloria Streit

2007-05-01

This article examines the preservation of pragmatic abilities of individuals with aphasia, as manifested in the discourse they produce. The construct of coherence is used as a framework for understanding this pragmatic preservation. Discourse coherence is largely derived from the structure, selection, and highlighting of information expressed in a discourse. Personal narratives, as one type of discourse, represent an extended turn-in-conversation on a topic of personal relevance to the speaker, common in everyday life. As such, they provide a valuable source of information about a speaker's pragmatic ability. Examples of personal narratives told by individuals with aphasia are used to illustrate and discuss the means by which discourse coherence is achieved. These include a tightly structured temporal-causal event line, development of theme, and evaluation of information. Possible approaches to clinical assessment are considered, including use of global rating systems.

Coherent perfect absorption and laser modes in a cylindrical structure of conjugate metamaterials

NASA Astrophysics Data System (ADS)

Fu, Yangyang; Xu, Yadong; Chen, Huanyang; Cummer, Steven A.

2018-01-01

In this work, we theoretically find that coherent perfect absorption (CPA) and laser modes can be realized in a two-dimensional cylindrical structure composed of conjugate metamaterials (CMs). The required phase factors of CMs for achieving CPA and laser modes are determined by the geometric size of the CM cylinder, which is a unique feature compared with other non-Hermitian optical systems. Based on this property, we also demonstrate that CPA and laser modes can exist simultaneously in a CM cylinder with an extremely large size, where the excitations of CPA and laser modes depend on the angular momentum of coherent incident light. Therefore, compared with the well known parity time symmetry, our work opens up a brand-new path to obtaining CPA and laser modes, and is a significant advance in non-Hermitian optical systems.

Electron coherent diffraction tomography of a nanocrystal

NASA Astrophysics Data System (ADS)

Dronyak, Roman; Liang, Keng S.; Tsai, Jin-Sheng; Stetsko, Yuri P.; Lee, Ting-Kuo; Chen, Fu-Rong

2010-05-01

Coherent diffractive imaging (CDI) with electron or x-ray sources is a promising technique for investigating the structure of nanoparticles down to the atomic scale. In electron CDI, a two-dimensional reconstruction is demonstrated using highly coherent illumination from a field-emission gun as a source of electrons. In a three-dimensional (3D) electron CDI, we experimentally determine the morphology of a single MgO nanocrystal using the Bragg diffraction geometry. An iterative algorithm is applied to invert the 3D diffraction pattern about a (200) reflection of the nanoparticle measured at an angular range of 1.8°. The results reveal a 3D image of the sample at ˜8 nm resolution, and agree with a simulation. Our work demonstrates an alternative approach to obtain the 3D structure of nanocrystals with an electron microscope.

Mesoscale variations in acoustic signals induced by atmospheric gravity waves.

PubMed

Chunchuzov, Igor; Kulichkov, Sergey; Perepelkin, Vitaly; Ziemann, Astrid; Arnold, Klaus; Kniffka, Anke

2009-02-01

The results of acoustic tomographic monitoring of the coherent structures in the lower atmosphere and the effects of these structures on acoustic signal parameters are analyzed in the present study. From the measurements of acoustic travel time fluctuations (periods 1 min-1 h) with distant receivers, the temporal fluctuations of the effective sound speed and wind speed are retrieved along different ray paths connecting an acoustic pulse source and several receivers. By using a coherence analysis of the fluctuations near spatially distanced ray turning points, the internal wave-associated fluctuations are filtered and their spatial characteristics (coherences, horizontal phase velocities, and spatial scales) are estimated. The capability of acoustic tomography in estimating wind shear near ground is shown. A possible mechanism describing the temporal modulation of the near-ground wind field by ducted internal waves in the troposphere is proposed.

Optical frequency modulation continuous wave coherent laser radar for spacecraft safe landing vector velocity measurement

NASA Astrophysics Data System (ADS)

Sui, Xiao-lin; Zhou, Shou-huan

2013-05-01

The design and performance of Optical frequency modulation continuous wave (OFMCW) coherent laser radar is presented. By employing a combination of optical heterodyne and linear frequency modulation techniques and utilizing fiber optic technologies, highly efficient, compact and reliable laser radar suitable for operation in a space environment is being developed.We also give a hardware structure of the OFMCW coherent laser radar. We made a detailed analysis of the measurement error. Its accuracy in the speed range is less than 0.5%.Measurement results for the movement of the carrier has also made a detailed assessment. The results show that its acceleration vector has better adaptability. The circuit structure is also given a detailed design. At the end of the article, we give the actual authentication method and experimental results.

Two-color surface-emitting lasers by a GaAs-based coupled multilayer cavity structure for coherent terahertz light sources

NASA Astrophysics Data System (ADS)

Lu, Xiangmeng; Ota, Hiroto; Kumagai, Naoto; Minami, Yasuo; Kitada, Takahiro; Isu, Toshiro

2017-11-01

Two-color surface-emitting lasers were fabricated using a GaAs-based coupled multilayer cavity structure grown by molecular beam epitaxy. InGaAs/GaAs multiple quantum wells were introduced only in the upper cavity for two-mode emission in the near-infrared region. Two-color lasing of the device was successfully demonstrated under pulsed current operations at room temperature. We also observed good temporal coherence of the two-color laser light using a Michelson interferometer. A coherent terahertz source is expected when a wafer-bonded coupled cavity consisting of (0 0 1) and non-(0 0 1) epitaxial films is used for the two-color laser device, in which the difference-frequency generation can be enabled by the second-order nonlinear response in the lower cavity.

Two Decades of Structure Building

PubMed Central

Gernsbacher, Morton Ann

2014-01-01

During the past decade I have been developing a very simple framework for describing the cognitive processes and mechanisms involved in discourse comprehension. I call this framework the Structure Building Framework, and it is based on evidence provided during the first decade of discourse processing research. According to the Structure Building Framework, the goal of comprehension is to build coherent mental representations or structures. Comprehenders build each structure by first laying a foundation. Comprehenders develop mental structures by mapping on new information when that information coheres or relates to previous information. However, when the incoming information is less related, comprehenders shift and attach a new substructure. The building blocks of mental structures are memory nodes, which are activated by incoming stimuli and controlled by two cognitive mechanisms: suppression and enhancement. In this article, first I review the seminal work on which the Structure Building Framework is based (the first decade of structure building research); then I recount the research I have conducted to test the Structure Building Framework (the second decade of structure building research). PMID:25484476

Comparison of Wechsler Memory Scale-Fourth Edition (WMS-IV) and Third Edition (WMS-III) dimensional structures: improved ability to evaluate auditory and visual constructs.

PubMed

Hoelzle, James B; Nelson, Nathaniel W; Smith, Clifford A

2011-03-01

Dimensional structures underlying the Wechsler Memory Scale-Fourth Edition (WMS-IV) and Wechsler Memory Scale-Third Edition (WMS-III) were compared to determine whether the revised measure has a more coherent and clinically relevant factor structure. Principal component analyses were conducted in normative samples reported in the respective technical manuals. Empirically supported procedures guided retention of dimensions. An invariant two-dimensional WMS-IV structure reflecting constructs of auditory learning/memory and visual attention/memory (C1 = .97; C2 = .96) is more theoretically coherent than the replicable, heterogeneous WMS-III dimension (C1 = .97). This research suggests that the WMS-IV may have greater utility in identifying lateralized memory dysfunction.

Sound production due to large-scale coherent structures. [and identification of noise mechanisms in turbulent shear flow

NASA Technical Reports Server (NTRS)

Gatski, T. B.

1979-01-01

The sound due to the large-scale (wavelike) structure in an infinite free turbulent shear flow is examined. Specifically, a computational study of a plane shear layer is presented, which accounts, by way of triple decomposition of the flow field variables, for three distinct component scales of motion (mean, wave, turbulent), and from which the sound - due to the large-scale wavelike structure - in the acoustic field can be isolated by a simple phase average. The computational approach has allowed for the identification of a specific noise production mechanism, viz the wave-induced stress, and has indicated the effect of coherent structure amplitude and growth and decay characteristics on noise levels produced in the acoustic far field.

Children's knowledge of the earth: a new methodological and statistical approach.

PubMed

Straatemeier, Marthe; van der Maas, Han L J; Jansen, Brenda R J

2008-08-01

In the field of children's knowledge of the earth, much debate has concerned the question of whether children's naive knowledge-that is, their knowledge before they acquire the standard scientific theory-is coherent (i.e., theory-like) or fragmented. We conducted two studies with large samples (N=328 and N=381) using a new paper-and-pencil test, denoted the EARTH (EArth Representation Test for cHildren), to discriminate between these two alternatives. We performed latent class analyses on the responses to the EARTH to test mental models associated with these alternatives. The naive mental models, as formulated by Vosniadou and Brewer, were not supported by the results. The results indicated that children's knowledge of the earth becomes more consistent as children grow older. These findings support the view that children's naive knowledge is fragmented.

Leadership Preparation in an Education Doctorate Program

ERIC Educational Resources Information Center

Ryerson, Dean

2011-01-01

This was a study of an education doctorate program at a small, private college. It examined the following nine components: theory of leadership for school improvement; candidate recruitment and selection based on leadership; coherent curriculum; use of active learning strategies; knowledgeable faculty; high quality internships; social and…

Toward a Critical Utopian and Pedagogical Methodology

ERIC Educational Resources Information Center

Firth, Rhiannon

2013-01-01

This article explores the possibility of developing an ethico-politically coherent and practical research framework for studying the learning and knowledge-production and dissemination processes of utopian groups and movements. It seeks to develop understanding of utopias by identifying and conceptualizing their pedagogical aspects. At the same…

The Integrated Business Curriculum: An Examination of Perceptions and Practices

ERIC Educational Resources Information Center

Athavale, Manoj; Davis, Rod; Myring, Mark

2008-01-01

Constituents often criticize business schools for failing to provide students with a comprehensive understanding of how business organizations function. Business schools have responded to the mandate with attempts to integrate discipline-specific functional knowledge into a coherent understanding of the evolving business organization. Successful…

Estimation of Signal Coherence Threshold and Concealed Spectral Lines Applied to Detection of Turbofan Engine Combustion Noise

NASA Technical Reports Server (NTRS)

Miles, Jeffrey Hilton

2010-01-01

Combustion noise from turbofan engines has become important, as the noise from sources like the fan and jet are reduced. An aligned and un-aligned coherence technique has been developed to determine a threshold level for the coherence and thereby help to separate the coherent combustion noise source from other noise sources measured with far-field microphones. This method is compared with a statistics based coherence threshold estimation method. In addition, the un-aligned coherence procedure at the same time also reveals periodicities, spectral lines, and undamped sinusoids hidden by broadband turbofan engine noise. In calculating the coherence threshold using a statistical method, one may use either the number of independent records or a larger number corresponding to the number of overlapped records used to create the average. Using data from a turbofan engine and a simulation this paper shows that applying the Fisher z-transform to the un-aligned coherence can aid in making the proper selection of samples and produce a reasonable statistics based coherence threshold. Examples are presented showing that the underlying tonal and coherent broad band structure which is buried under random broadband noise and jet noise can be determined. The method also shows the possible presence of indirect combustion noise. Copyright 2011 Acoustical Society of America. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the Acoustical Society of America.

Engineering the vibrational coherence of vision into a synthetic molecular device.

PubMed

Gueye, Moussa; Manathunga, Madushanka; Agathangelou, Damianos; Orozco, Yoelvis; Paolino, Marco; Fusi, Stefania; Haacke, Stefan; Olivucci, Massimo; Léonard, Jérémie

2018-01-22

The light-induced double-bond isomerization of the visual pigment rhodopsin operates a molecular-level optomechanical energy transduction, which triggers a crucial protein structure change. In fact, rhodopsin isomerization occurs according to a unique, ultrafast mechanism that preserves mode-specific vibrational coherence all the way from the reactant excited state to the primary photoproduct ground state. The engineering of such an energy-funnelling function in synthetic compounds would pave the way towards biomimetic molecular machines capable of achieving optimum light-to-mechanical energy conversion. Here we use resonance and off-resonance vibrational coherence spectroscopy to demonstrate that a rhodopsin-like isomerization operates in a biomimetic molecular switch in solution. Furthermore, by using quantum chemical simulations, we show why the observed coherent nuclear motion critically depends on minor chemical modifications capable to induce specific geometric and electronic effects. This finding provides a strategy for engineering vibrationally coherent motions in other synthetic systems.

Contributions to the understanding of large-scale coherent structures in developing free turbulent shear flows

NASA Technical Reports Server (NTRS)

Liu, J. T. C.

1986-01-01

Advances in the mechanics of boundary layer flow are reported. The physical problems of large scale coherent structures in real, developing free turbulent shear flows, from the nonlinear aspects of hydrodynamic stability are addressed. The presence of fine grained turbulence in the problem, and its absence, lacks a small parameter. The problem is presented on the basis of conservation principles, which are the dynamics of the problem directed towards extracting the most physical information, however, it is emphasized that it must also involve approximations.

Analysis of Sub-Grid Boundary-Layer Processes Observed by the P-3 Doppler Wind Lidar in Support of the Western Pacific Tropical Cyclone Structure 2008 Experiment

DTIC Science & Technology

2012-02-02

flight hours to one significant atmospheric phenomena. OBJECTIVES The P-3 Doppler Wind Lidar (P3DWL) uses the latest version of a coherent ... Doppler transceiver developed at Lockheed Martin Coherent Technologies. The lidar , with the exception of the scanner, is shown on the top in Figure 1...Processes Observed by the P-3 Doppler Wind Lidar in Support of the Western Pacific Tropical Cyclone Structure 2008 Experiment Ralph Foster Applied

Comparing High-latitude Ionospheric and Thermospheric Lagrangian Coherent Structures

NASA Astrophysics Data System (ADS)

Wang, N.; Ramirez, U.; Flores, F.; Okic, D.; Datta-Barua, S.

2015-12-01

Lagrangian Coherent Structures (LCSs) are invisible boundaries in time varying flow fields that may be subject to mixing and turbulence. The LCS is defined by the local maxima of the finite time Lyapunov exponent (FTLE), a scalar field quantifying the degree of stretching of fluid elements over the flow domain. Although the thermosphere is dominated by neutral wind processes and the ionosphere is governed by plasma electrodynamics, we can compare the LCS in the two modeled flow fields to yield insight into transport and interaction processes in the high-latitude IT system. For obtaining thermospheric LCS, we use the Horizontal Wind Model 2014 (HWM14) [1] at a single altitude to generate the two-dimensional velocity field. The FTLE computation is applied to study the flow field of the neutral wind, and to visualize the forward-time Lagrangian Coherent Structures in the flow domain. The time-varying structures indicate a possible thermospheric LCS ridge in the auroral oval area. The results of a two-day run during a geomagnetically quiet period show that the structures are diurnally quasi-periodic, thus that solar radiation influences the neutral wind flow field. To find the LCS in the high-latitude ionospheric drifts, the Weimer 2001 [2] polar electric potential model and the International Geomagnetic Reference Field 11 [3] are used to compute the ExB drift flow field in ionosphere. As with the neutral winds, the Lagrangian Coherent Structures are obtained by applying the FTLE computation. The relationship between the thermospheric and ionospheric LCS is analyzed by comparing overlapping FTLE maps. Both a publicly available FTLE solver [4] and a custom-built FTLE computation are used and compared for validation [5]. Comparing the modeled IT LCSs on a quiet day with the modeled IT LCSs on a storm day indicates important factors on the structure and time evolution of the LCS.

Dynamics of plasmonic field polarization induced by quantum coherence in quantum dot-metallic nanoshell structures.

PubMed

Sadeghi, S M

2014-09-01

When a hybrid system consisting of a semiconductor quantum dot and a metallic nanoparticle interacts with a laser field, the plasmonic field of the metallic nanoparticle can be normalized by the quantum coherence generated in the quantum dot. In this Letter, we study the states of polarization of such a coherent-plasmonic field and demonstrate how these states can reveal unique aspects of the collective molecular properties of the hybrid system formed via coherent exciton-plasmon coupling. We show that transition between the molecular states of this system can lead to ultrafast polarization dynamics, including sudden reversal of the sense of variations of the plasmonic field and formation of circular and elliptical polarization.

Coherent structures and flow topology of transitional separated-reattached flow over two and three dimensional geometrical shapes

NASA Astrophysics Data System (ADS)

Diabil, Hayder Azeez; Li, Xin Kai; Abdalla, Ibrahim Elrayah

2017-09-01

Large-scale organized motions (commonly referred to coherent structures) and flow topology of a transitional separated-reattached flow have been visualised and investigated using flow visualisation techniques. Two geometrical shapes including two-dimensional flat plate with rectangular leading edge and three-dimensional square cylinder are chosen to shed a light on the flow topology and present coherent structures of the flow over these shapes. For both geometries and in the early stage of the transition, two-dimensional Kelvin-Helmholtz rolls are formed downstream of the leading edge. They are observed to be twisting around the square cylinder while they stay flat in the case of the two-dimensional flat plate. For both geometrical shapes, the two-dimensional Kelvin-Helmholtz rolls move downstream of the leading edge and they are subjected to distortion to form three-dimensional hairpin structures. The flow topology in the flat plate is different from that in the square cylinder. For the flat plate, there is a merging process by a pairing of the Kelvin-Helmholtz rolls to form a large structure that breaks down directly into many hairpin structures. For the squire cylinder case, the Kelvin-Helmholtz roll evolves topologically to form a hairpin structure. In the squire cylinder case, the reattachment length is much shorter and a forming of the three-dimensional structures is closer to the leading edge than that in the flat plate case.

On the nonlinear trapping nature of undamped, coherent structures in collisionless plasmas and its impact on stability

NASA Astrophysics Data System (ADS)

Schamel, Hans; Mandal, Debraj; Sharma, Devendra

2017-03-01

An outstanding notion for collisionless plasmas is the essential nonlinear character of their coherent structures, which in the stationary, weak amplitude limit are described by a continuum of cnoidal electron and ion hole modes governed by a multiparametric nonlinear dispersion relation. The well-known discrete structure of undamped linear plasma modes is seamlessly embedded in this nonlinear continuum as the microscopic texture of plasma begins to reveal itself in the high temperature collisionless plasma limit. This transforms the linear-threshold-based operating mechanism of plasma turbulence into a fundamental nonlinear, multifaceted one. Based on a comprehensive three-level description of increasing profundity, a proof of this novel dictum is presented, which makes use of the joint properties of such structures, their coherency and stationarity, and uses in succession a fluid, linear Vlasov and a full Vlasov description. It unifies discrete and continuum limits by resolving the inevitable resonant region and shows that coherent electrostatic equilibria are generally controlled by kinetic particle trapping and are hence fundamentally nonlinear. By forging a link between damped and growing wave solutions, these modes render plasma stability complex and difficult to evaluate due to the entangled pattern of the stability boundary in function and parameter space, respectively. A direct consequence is the existence of negative energy modes of arbitrarily small amplitudes in the subcritical region of the two-stream instability as well as the failure of linear Landau (Vlasov, van Kampen) theory, whenever resonant particles are involved, in addressing the onset of instability in a current-carrying plasma. Responsible for this subtle phase space behavior is hence the thresholdless omnipresence of the trapping nonlinearity originating from coherency. A high resolution, exact-mass-ratio, multispecies, and collisionless plasma simulation is employed to illustrate exemplarily how tiny seed fluctuations in phase-space can act as a triggering agent for a subcritical plasma excitation verifying an access to these modes in the noisy, collisionless plasma limit.

Micro-optical coherence tomography of the mammalian cochlea

PubMed Central

Iyer, Janani S.; Batts, Shelley A.; Chu, Kengyeh K.; Sahin, Mehmet I.; Leung, Hui Min; Tearney, Guillermo J.; Stankovic, Konstantina M.

2016-01-01

The mammalian cochlea has historically resisted attempts at high-resolution, non-invasive imaging due to its small size, complex three-dimensional structure, and embedded location within the temporal bone. As a result, little is known about the relationship between an individual’s cochlear pathology and hearing function, and otologists must rely on physiological testing and imaging methods that offer limited resolution to obtain information about the inner ear prior to performing surgery. Micro-optical coherence tomography (μOCT) is a non-invasive, low-coherence interferometric imaging technique capable of resolving cellular-level anatomic structures. To determine whether μOCT is capable of resolving mammalian intracochlear anatomy, fixed guinea pig inner ears were imaged as whole temporal bones with cochlea in situ. Anatomical structures such as the tunnel of Corti, space of Nuel, modiolus, scalae, and cell groupings were visualized, in addition to individual cell types such as neuronal fibers, hair cells, and supporting cells. Visualization of these structures, via volumetrically-reconstructed image stacks and endoscopic perspective videos, represents an improvement over previous efforts using conventional OCT. These are the first μOCT images of mammalian cochlear anatomy, and they demonstrate μOCT’s potential utility as an imaging tool in otology research. PMID:27633610

Diagnosis of Magnetic Structures and Intermittency in Space Plasma Turbulence using the Method of Surrogate Data

NASA Technical Reports Server (NTRS)

Sahraoui, Fouad; Goldstein, Melvyn

2008-01-01

Several observations in space plasmas have reported the presence of coherent structures at different plasma scales. Structure formation is believed to be a direct consequence of nonlinear interactions between the plasma modes, which depend strongly on phase synchronization of those modes. Despite this important role of the phases in turbulence, very limited work has been however devoted to study the phases as a potential tracers of nonlinearities in comparison with the wealth of literature on power spectra of turbulence where phases are totally missed. We present a method based on surrogate data to systematically detect coherent structures in turbulent signals. The new method has been applied successfully to magnetosheath turbulence (Sahraoui, Phys. Rev. E, 2008, in press), where the relationship between the identified phase coherence and intermittency (classically identified as non Gaussian tails of the PDFs) as well as the energy cascade has been studied. Here we review the main results obtained in that study and show further applications to small scale solar wind turbulence. Implications of the results on theoretical modelling of space turbulence (applicability of weak/wave turbulence, its validity limits and its connection to intermittency) will be discussed.

Health-related quality of life, sense of coherence and leisure-time physical activity in women after an acute myocardial infarction.

PubMed

Løvlien, Mona; Mundal, Liv; Hall-Lord, Marie-Louise

2017-04-01

To examine the relationship between leisure-time physical activity, health-related quality of life and sense of coherence in women after an acute myocardial infarction, and further to investigate whether these aspects were associated with age. Physical activity and health-related quality of life are vital aspects for patients after an acute myocardial infarction. Cross-sectional. All eligible women diagnosed with acute myocardial infarction received a postal questionnaire two to three months after hospital discharge, and 142 women were included. To measure health-related quality of life and sense of coherence, The MacNew Heart disease questionnaire and the Sense of coherence-13 scale was used. Respondents reporting at least one type of physical activity had significantly higher health-related quality of life as compared to respondents reporting no kind of physical activity. Respondents reporting physical activity for at least 30 minutes twice a week had significantly higher health-related quality of life scores than respondents being active less than twice a week. A weak association was found between physical activity level and sense of coherence. Reduction in physical activity after the acute myocardial infarction was associated with reduced health-related quality of life and sense of coherence. Sense of coherence was significantly associated with age, as respondents 75 years and older had significantly higher scores than respondents younger than 75 years. Physical activity, even at a low level, is significantly associated with increased health-related quality of life and to some extent to sense of coherence. Tailoring women after an acute myocardial infarction about lifestyle changes must include knowledge about the benefits of leisure-time physical activity, and that even a small amount of activity is associated with a better health-related quality of life. The utmost important assignment is to motivate the women for regular physical activity in their leisure-time. Older women need special attention. © 2016 John Wiley & Sons Ltd.

IMAGING WITH MULTIMODAL ADAPTIVE-OPTICS OPTICAL COHERENCE TOMOGRAPHY IN MULTIPLE EVANESCENT WHITE DOT SYNDROME: THE STRUCTURE AND FUNCTIONAL RELATIONSHIP.

PubMed

Labriola, Leanne T; Legarreta, Andrew D; Legarreta, John E; Nadler, Zach; Gallagher, Denise; Hammer, Daniel X; Ferguson, R Daniel; Iftimia, Nicusor; Wollstein, Gadi; Schuman, Joel S

2016-01-01

To elucidate the location of pathological changes in multiple evanescent white dot syndrome (MEWDS) with the use of multimodal adaptive optics (AO) imaging. A 5-year observational case study of a 24-year-old female with recurrent MEWDS. Full examination included history, Snellen chart visual acuity, pupil assessment, intraocular pressures, slit lamp evaluation, dilated fundoscopic exam, imaging with Fourier-domain optical coherence tomography (FD-OCT), blue-light fundus autofluorescence (FAF), fundus photography, fluorescein angiography, and adaptive-optics optical coherence tomography. Three distinct acute episodes of MEWDS occurred during the period of follow-up. Fourier-domain optical coherence tomography and adaptive-optics imaging showed disturbance in the photoreceptor outer segments (PR OS) in the posterior pole with each flare. The degree of disturbance at the photoreceptor level corresponded to size and extent of the visual field changes. All findings were transient with delineation of the photoreceptor recovery from the outer edges of the lesion inward. Hyperautofluorescence was seen during acute flares. Increase in choroidal thickness did occur with each active flare but resolved. Although changes in the choroid and RPE can be observed in MEWDS, Fourier-domain optical coherence tomography, and multimodal adaptive optics imaging localized the visually significant changes seen in this disease at the level of the photoreceptors. These transient retinal changes specifically occur at the level of the inner segment ellipsoid and OS/RPE line. En face optical coherence tomography imaging provides a detailed, yet noninvasive method for following the convalescence of MEWDS and provides insight into the structural and functional relationship of this transient inflammatory retinal disease.

An Objective Rationale for the Choice of Regularisation Parameter with Application to Global Multiple-Frequency S-Wave Tomography

NASA Astrophysics Data System (ADS)

Zaroli, C.; Sambridge, M.; Leveque, J. J.; Debayle, E.; Nolet, G.

2014-12-01

In a linear ill-posed inverse problem, the regularisation parameter (damping) controls the balance between minimising both the residual data misfit and the model norm. Poor knowledge of data uncertainties often makes the selection of damping rather arbitrary. To go beyond that subjectivity, an objective rationale for the choice of damping is presented, which is based on the coherency of delay-time estimates in different frequency bands. Our method is tailored to the problem of global Multiple-Frequency Tomography, using a data set of 287078 S-wave delay-times measured in five frequency bands (10, 15, 22, 34, 51 s central periods). Whereas for each ray path the delay-time estimates should vary coherently from one period to the other, the noise most likely is not coherent. Thus, the lack of coherency of the information in different frequency bands is exploited, using an analogy with the cross-validation method, to identify models dominated by noise.In addition, a sharp change of behaviour of the model infinity-norm, as the damping becomes lower than a threshold value, is interpreted as the signature of data noise starting to significantly pollute at least one model component. Models with damping larger than this threshold are diagnosed as being constructed with poor data exploitation.Finally, a preferred model is selected from the remaining range of permitted model solutions. This choice is quasi-objective in terms of model interpretation, as the selected model shows a high degree of similarity with almost all other permitted models. The obtained tomographic model is displayed in mid lower-mantle (660-1910 km depth), and is shown to be mostly compatible with three other recent global shear-velocity models, while significant differences can be noticed. A wider application of the presented rationale should permit us to converge towards more objective seismic imaging of the Earth's mantle, using as much as possible of the relevant structural information in the data. This work was recently published: Zaroli, C., Sambridge, M., Lévêque, J.-J., Debayle, E., and Nolet, G. (2013) - Solid Earth, 4, 357-371, doi:10.5194/se-4-357-2013

Experimental observation of the effect of generic singularities in polychromatic dark hollow beams.

PubMed

Yadav, Bharat Kumar; Joshi, Stuti; Kandpal, Hem Chandra

2014-08-15

This Letter presents the essence of our recent experimental study on generic singularities carrying spatially partially coherent, polychromatic dark hollow beams (PDHBs). To the best of our knowledge, this is the first experimental demonstration of generic singularities-induced wavefront tearing in focused polychromatic beams.

Reviewing the Connection between Paradigms and Theories to Understand Adolescent Drug Use

ERIC Educational Resources Information Center

Clark, Trenette T.

2010-01-01

Approaches to studying social phenomenon are fundamentally based upon personal beliefs about the nature of knowledge, reality, and order. Scholars, researchers, and practitioners can benefit from utilizing a coherent method that organizes the wide array of perspectives that exist and the theories, practice, prevention interventions, and policies…

A Conceptual Framework for Web-Based Learning Design

ERIC Educational Resources Information Center

Alomyan, Hesham

2017-01-01

The purpose of this paper is to provide a coherent framework to present the relationship between individual differences and web-based learning. Two individual difference factors have been identified for investigation within the present paper: Cognitive style and prior knowledge. The importance of individual differences is reviewed and previous…

ATP: A Coherent View for School Advanced Level Studies in Biology.

ERIC Educational Resources Information Center

Gayford, Chris

1986-01-01

Discusses how instruction of biological concepts as ATP cellular energetics is related to fundamental physical science understandings. Reviews areas of common misconceptions and confusions. Summarizes results of a study which investigated students' knowledge and perception of difficulty associated with the topic of energy and ATP. (ML)

A Longitudinal Study of Children's Developing Knowledge and Reasoning in Science

ERIC Educational Resources Information Center

Tytler, Russell; Peterson, Suzanne

2005-01-01

The growth in science understanding and reasoning of 12 children is being traced through their primary school years. The paper reports findings concerning children's growing understandings of evaporation, and their changing responses to exploration activities, that show the complexity and coherence of learning pathways. Children's responses to…

Coherence in Professional Education: Does It Foster Dedication and Identification?

ERIC Educational Resources Information Center

Heggen, Kåre; Terum, Lars Inge

2013-01-01

This article examines the impact of professional education on students' dedication to and identification with a profession. The premise is that professional education is not only about knowledge acquisition and reasoning but also about attitudes and aspirations. In fostering dedication and identification, students' experiences of relevance seem to…

Design of Automated Guidance to Support Effortful Revisions and Knowledge Integration in Science Learning

ERIC Educational Resources Information Center

Tansomboon, Charissa

2017-01-01

Students studying complex science topics can benefit from receiving immediate, personalized guidance. Supporting students to revise their written explanations in science can help students to integrate disparate ideas and develop a coherent, generative account of complex scientific topics. Using natural language processing to analyze student…

Exploring Lecturers' Views of First-Year Health Science Students' Misconceptions in Biomedical Domains

ERIC Educational Resources Information Center

Badenhorst, Elmi; Mamede, Sílvia; Hartman, Nadia; Schmidt, Henk G.

2015-01-01

Research has indicated that misconceptions hamper the process of knowledge construction. Misconceptions are defined as persistent ideas not supported by current scientific views. Few studies have explored how misconceptions develop when first year health students conceptually move between anatomy and physiology to construct coherent knowledge…

Strategic Questions: A Means of Building Metacognitive Language

ERIC Educational Resources Information Center

Deed, Craig

2008-01-01

Conversations between educators and students about choices and strategies are an important pedagogical mechanism to examine the abstract concept of learning. Although students have tacit knowledge about their approach to learning, they are often unable to coherently communicate their ideas. Drawing on the theory of metacognition, the technique of…

HyperMinds for HyperTimes: The Demise of Rational, Logical Thought?

ERIC Educational Resources Information Center

Campbell, Robert J.

1998-01-01

Contrasts rational thought with "hyperthinking" where individuals have no concept of how to gather, evaluate, and use information to create coherent arguments. Examines hypermind characteristics: lack of self-knowledge, prey to sensory stimulation, poor communication and thinking skills, lack of metacognitive abilities, and inability to…

The Living Dead: Transformative Experiences in Modelling Natural Selection

ERIC Educational Resources Information Center

Petersen, Morten Rask

2017-01-01

This study considers how students change their coherent conceptual understanding of natural selection through a hands-on simulation. The results show that most students change their understanding. In addition, some students also underwent a transformative experience and used their new knowledge in a leisure time activity. These transformative…

Disciplinary Authority and Accountability in Scientific Practice and Learning

ERIC Educational Resources Information Center

Ford, Michael

2008-01-01

This article explores the relation between how scientific knowledge is created and the reasoning involved in learning content with understanding. Although an asserted parallel between these underpins reform, little is actually known about this relation. This article offers a model of this relation that draws coherent connections between the…

A Simple View of Linguistic Complexity

ERIC Educational Resources Information Center

Pallotti, Gabriele

2015-01-01

Although a growing number of second language acquisition (SLA) studies take linguistic complexity as a dependent variable, the term is still poorly defined and often used with different meanings, thus posing serious problems for research synthesis and knowledge accumulation. This article proposes a simple, coherent view of the construct, which is…

Common Guidelines for Education Research and Development

ERIC Educational Resources Information Center

Institute of Education Sciences, 2013

2013-01-01

In January 2011, a Joint Committee of representatives from the U.S. Department of Education (ED) and the U.S. National Science Foundation (NSF) began work to establish cross-agency guidelines for improving the quality, coherence, and pace of knowledge development in science, technology, engineering and mathematics (STEM) education. Although the…

Unstable flow structures in the Blasius boundary layer.

PubMed

Wedin, H; Bottaro, A; Hanifi, A; Zampogna, G

2014-04-01

Finite amplitude coherent structures with a reflection symmetry in the spanwise direction of a parallel boundary layer flow are reported together with a preliminary analysis of their stability. The search for the solutions is based on the self-sustaining process originally described by Waleffe (Phys. Fluids 9, 883 (1997)). This requires adding a body force to the Navier-Stokes equations; to locate a relevant nonlinear solution it is necessary to perform a continuation in the nonlinear regime and parameter space in order to render the body force of vanishing amplitude. Some states computed display a spanwise spacing between streaks of the same length scale as turbulence flow structures observed in experiments (S.K. Robinson, Ann. Rev. Fluid Mech. 23, 601 (1991)), and are found to be situated within the buffer layer. The exact coherent structures are unstable to small amplitude perturbations and thus may be part of a set of unstable nonlinear states of possible use to describe the turbulent transition. The nonlinear solutions survive down to a displacement thickness Reynolds number Re * = 496 , displaying a 4-vortex structure and an amplitude of the streamwise root-mean-square velocity of 6% scaled with the free-stream velocity. At this Re* the exact coherent structure bifurcates supercritically and this is the point where the laminar Blasius flow starts to cohabit the phase space with alternative simple exact solutions of the Navier-Stokes equations.

[From relativism to evaluation. Recent trends in the historiography of science and the humanities].

PubMed

Jonker, Ed

2011-01-01

Historians of science have taken leave of finalism. No longer do they write teleological histories of scientific progress. Instead of a grand narrative on the triumph of science they now tend to write small stories on local knowledge. This is the result of several decades of criticism of Whig history. Starting with neo-marxist critique in the interwar years, enhanced in the social history of the 1970s, science was seen as an economic commodity and as a social product. Cultural history and anthropology added the view that scientists and scholars are mere mortals, muddling through messy life. This critique was topped off with postmodern criticism of knowledge as power, which translates into the accusation that historiography is only legitimating cultural and political oppression. To counter these allegations, many historians have insulated themselves into a kind of retro-historicism that shies away from any teleology, coherence, meaning and evaluation. It depicts the production of knowledge as a practical, local activity that is strictly limited to its cultural context. No claims to truth, validity, let alone progress or even development were allowed. This situation of rampant relativism could not last. Total abstinence of any evaluation of knowledge claims, quality of research or success of theories has proven unsatisfactory. The need has arisen to study broader issues of traveling knowledge and longer lines of scientific development. There is a shift of interest into traditions of knowledge that spring the bonds of locality and context. Why do some scientific theories and research practices succeed in surpassing paradigms and bridging epistemic ruptures? In this respect disciplines are in the process of being rehabilitated. Instead of oppressive structures they become the vehicles of sustained knowledge growth. Especially the role of education and academic training is focused on. Facing up to the charges of conceptual anachronism, historians of knowledge now opt for a cautiously evaluative history. The alternative would be an intellectually barren historicism.

Stripe-like nanoscale structural phase separation in superconducting BaPb 1-xBi xO 3

DOE PAGES

Giraldo-Gallo, P.; Zhang, Y.; Parra, C.; ...

2015-09-16

The phase diagram of BaPb 1-xBi xO 3 exhibits a superconducting “dome” in the proximity of a charge density wave phase. For the superconducting compositions, the material coexists as two structural polymorphs. Here we show, via high resolution transmission electron microscopy, that the structural dimorphism is accommodated in the form of partially disordered nanoscale stripes. Identification of the morphology of the nanoscale structural phase separation enables determination of the associated length scales, which we compare to the Ginzburg-Landau coherence length. Thus, we find that the maximum T c occurs when the superconducting coherence length matches the width of the partiallymore » disordered stripes, implying a connection between the structural phase separation and the shape of the superconducting dome.« less

Optical coherence tomography as an accurate inspection and quality evaluation technique in paper industry

NASA Astrophysics Data System (ADS)

Prykäri, Tuukka; Czajkowski, Jakub; Alarousu, Erkki; Myllylä, Risto

2010-05-01

Optical coherence tomography (OCT), a technique for the noninvasive imaging of turbid media, based on low-coherence interferometry, was originally developed for the imaging of biological tissues. Since the development of the technique, most of its applications have been related to the area of biomedicine. However, from early stages, the vertical resolution of the technique has already been improved to a submicron scale. This enables new possibilities and applications. This article presents the possible applications of OCT in paper industry, where submicron or at least a resolution close to one micron is required. This requirement comes from the layered structure of paper products, where layer thickness may vary from single microns to tens of micrometers. This is especially similar to the case with high-quality paper products, where several different coating layers are used to obtain a smooth surface structure and a high gloss. In this study, we demonstrate that optical coherence tomography can be used to measure and evaluate the quality of the coating layer of a premium glossy photopaper. In addition, we show that for some paper products, it is possible to measure across the entire thickness range of a paper sheet. Furthermore, we suggest that in addition to topography and tomography images of objects, it is possible to obtain information similar to gloss by tracking the magnitude of individual interference signals in optical coherence tomography.

Structure of turbulent shear flows

NASA Technical Reports Server (NTRS)

Hussain, A. K. M. F.; Jeong, J.; Kim, J.

1987-01-01

Activities are summarized for each of the three topics discussed: eduction of coherent structures; measurement of propagation velocities of perturbation in turbulent flows; and direct evaluation of the Taylor hypothesis.

Ballistic pulse propagation in quantum wire waveguides: Toward localization and control of electron wave packets in space and time

NASA Astrophysics Data System (ADS)

Hayata, K.; Tsuji, Y.; Koshiba, M.

1992-10-01

A theoretical formulation of electron pulse propagation in quantum wire structures with mesoscopic scale cross sections is presented, assuming quantum ballistic transport of electron wave packets over a certain characteristic length. As typical mesoscopic structures for realizing coherent electron transmission, two traveling-wave configurations are considered: straight quantum wire waveguides and quantum wire bend structures (quantum whispering galleries). To estimate temporal features of the pulse during propagation, the walk off, the dispersion, and the pulse coherence lengths are defined as useful characteristic lengths. Numerical results are shown for ultrashort pulse propagation through rectangular wire waveguides. Effects due to an external electric field are discussed as well.

Modelling the effect of perceived interdependence among mental healthcare professionals on their work role performance.

PubMed

Markon, Marie-Pierre; Chiocchio, François; Fleury, Marie-Josée

2017-07-01

The purpose of mental healthcare system reform was to enhance service efficiency by strengthening primary mental healthcare and increasing service integration in communities. Reinforcing interprofessional teamwork also intended to address the extensive and multidimensional needs of patients with mental disorders by bringing together a broader array of expertise. In this context, mental healthcare professionals (MHCPs) from various health and social care professions are more interdependent in many aspects of their work (tasks, resources, and goals). We wanted to examine the effect of perceived interdependence among MHCPs on their work role performance in the context of mental healthcare. For this purpose, we developed and tested a model coherent with the Input-Mediator-Outcome-Input (IMOI) framework of team effectiveness. Data from questionnaires administered to 315 MHCPs from four local health service networks in Quebec, Canada were analysed through structural equation modelling and mediation analysis. The structural equation model provided a good fit for the data and explained 51% of the variance of work role performance. Perceived collaboration, confidence in the advantages of interprofessional collaboration, involvement in the decision process, knowledge sharing, and satisfaction with the nature of the work partially mediated the effect of perceived interdependence among team members on work role performance. Therefore, perceived interdependence among team members had a positive impact on the work role performance of MHCPs mostly through its effect on favourable team functioning features. This implies, in practice, that increased interdependence of MHCPs would be more likely to truly enhance work role performance if team-based interventions to promote collaborative work and interprofessional teaching and training programs to support work within interprofessional teams were jointly implemented. Participation in the decision process and knowledge sharing should also be fostered, for instance, by adopting knowledge management best practices.

Correlation between polarization sensitive optical coherence tomography and SHG microscopy in articular cartilage

NASA Astrophysics Data System (ADS)

Zhou, Xin; Ju, Myeong Jin; Huang, Lin; Tang, Shuo

2017-02-01

Polarization-sensitive optical coherence tomography (PS-OCT) and second harmonic generation (SHG) microscopy are two imaging modalities with different resolutions, field-of-views (FOV), and contrasts, while they both have the capability of imaging collagen fibers in biological tissues. PS-OCT can measure the tissue birefringence which is induced by highly organized fibers while SHG can image the collagen fiber organization with high resolution. Articular cartilage, with abundant structural collagen fibers, is a suitable sample to study the correlation between PS-OCT and SHG microscopy. Qualitative conjecture has been made that the phase retardation measured by PS-OCT is affected by the relationship between the collagen fiber orientation and the illumination direction. Anatomical studies show that the multilayered architecture of articular cartilage can be divided into four zones from its natural surface to the subchondral bone: the superficial zone, the middle zone, the deep zone, and the calcified zone. The different zones have different collagen fiber orientations, which can be studied by the different slopes in the cumulative phase retardation in PS-OCT. An algorithm is developed based on the quantitative analysis of PS-OCT phase retardation images to analyze the microstructural features in swine articular cartilage tissues. This algorithm utilizes the depth-dependent slope changing of phase retardation A-lines to segment structural layers. The results show good consistency with the knowledge of cartilage morphology and correlation with the SHG images measured at selected depth locations. The correlation between PS-OCT and SHG microscopy shows that PS-OCT has the potential to analyze both the macro and micro characteristics of biological tissues with abundant collagen fibers and other materials that may cause birefringence.

Spectral Domain Optical Coherence Tomography in Glaucoma: Qualitative and Quantitative Analysis of the Optic Nerve Head and Retinal Nerve Fiber Layer (An AOS Thesis)

PubMed Central

Chen, Teresa C.

2009-01-01

Purpose: To demonstrate that video-rate spectral domain optical coherence tomography (SDOCT) can qualitatively and quantitatively evaluate optic nerve head (ONH) and retinal nerve fiber layer (RNFL) glaucomatous structural changes. To correlate quantitative SDOCT parameters with disc photography and visual fields. Methods: SDOCT images from 4 glaucoma eyes (4 patients) with varying stages of open-angle glaucoma (ie, early, moderate, late) were qualitatively contrasted with 2 age-matched normal eyes (2 patients). Of 61 other consecutive patients recruited in an institutional setting, 53 eyes (33 patients) met inclusion/exclusion criteria for quantitative studies. Images were obtained using two experimental SDOCT systems, one utilizing a superluminescent diode and the other a titanium:sapphire laser source, with axial resolutions of about 6 μm and 3 μm, respectively. Results: Classic glaucomatous ONH and RNFL structural changes were seen in SDOCT images. An SDOCT reference plane 139 μm above the retinal pigment epithelium yielded cup-disc ratios that best correlated with masked physician disc photography cup-disc ratio assessments. The minimum distance band, a novel SDOCT neuroretinal rim parameter, showed good correlation with physician cup-disc ratio assessments, visual field mean deviation, and pattern standard deviation (P values range, .0003–.024). RNFL and retinal thickness maps correlated well with disc photography and visual field testing. Conclusions: To our knowledge, this thesis presents the first comprehensive qualitative and quantitative evaluation of SDOCT images of the ONH and RNFL in glaucoma. This pilot study provides basis for developing more automated quantitative SDOCT-specific glaucoma algorithms needed for future prospective multicenter national trials. PMID:20126502

Optical Coherence Tomography Angiography in Retinal Diseases.

PubMed

Chalam, K V; Sambhav, Kumar

2016-01-01

Optical coherence tomography angiography (OCTA) is a new, non-invasive imaging system that generates volumetric data of retinal and choroidal layers. It has the ability to show both structural and blood flow information. Split-spectrum amplitude-decorrelation angiography (SSADA) algorithm (a vital component of OCTA software) helps to decrease the signal to noise ratio of flow detection thus enhancing visualization of retinal vasculature using motion contrast. Published studies describe potential efficacy for OCTA in the evaluation of common ophthalmologic diseases such as diabetic retinopathy, age related macular degeneration (AMD), retinal vascular occlusions and sickle cell disease. OCTA provides a detailed view of the retinal vasculature, which allows accurate delineation of microvascular abnormalities in diabetic eyes and vascular occlusions. It helps quantify vascular compromise depending upon the severity of diabetic retinopathy. OCTA can also elucidate the presence of choroidal neovascularization (CNV) in wet AMD. In this paper, we review the knowledge, available in English language publications regarding OCTA, and compare it with the conventional angiographic standard, fluorescein angiography (FA). Finally, we summarize its potential applications to retinal vascular diseases. Its current limitations include a relatively small field of view, inability to show leakage, and tendency for image artifacts. Further larger studies will define OCTA's utility in clinical settings and establish if the technology may offer a non-invasive option of visualizing the retinal vasculature, enabling us to decrease morbidity through early detection and intervention in retinal diseases.

Optical Coherence Tomography Angiography in Retinal Diseases

PubMed Central

Chalam, K. V.; Sambhav, Kumar

2016-01-01

Optical coherence tomography angiography (OCTA) is a new, non-invasive imaging system that generates volumetric data of retinal and choroidal layers. It has the ability to show both structural and blood flow information. Split-spectrum amplitude-decorrelation angiography (SSADA) algorithm (a vital component of OCTA software) helps to decrease the signal to noise ratio of flow detection thus enhancing visualization of retinal vasculature using motion contrast. Published studies describe potential efficacy for OCTA in the evaluation of common ophthalmologic diseases such as diabetic retinopathy, age related macular degeneration (AMD), retinal vascular occlusions and sickle cell disease. OCTA provides a detailed view of the retinal vasculature, which allows accurate delineation of microvascular abnormalities in diabetic eyes and vascular occlusions. It helps quantify vascular compromise depending upon the severity of diabetic retinopathy. OCTA can also elucidate the presence of choroidal neovascularization (CNV) in wet AMD. In this paper, we review the knowledge, available in English language publications regarding OCTA, and compare it with the conventional angiographic standard, fluorescein angiography (FA). Finally, we summarize its potential applications to retinal vascular diseases. Its current limitations include a relatively small field of view, inability to show leakage, and tendency for image artifacts. Further larger studies will define OCTA's utility in clinical settings and establish if the technology may offer a non-invasive option of visualizing the retinal vasculature, enabling us to decrease morbidity through early detection and intervention in retinal diseases. PMID:27195091

Altered spontaneous activity in antisocial personality disorder revealed by regional homogeneity.

PubMed

Tang, Yan; Liu, Wangyong; Chen, Jingang; Liao, Jian; Hu, Dewen; Wang, Wei

2013-08-07

There is increasing evidence that antisocial personality disorder (ASPD) stems from brain abnormalities. However, there are only a few studies investigating brain structure in ASPD. The aim of this study was to find regional coherence abnormalities in resting-state functional MRI of ASPD. Thirty-two ASPD individuals and 34 controls underwent a resting-state functional MRI scan. The regional homogeneity (ReHo) approach was used to examine whether ASPD was related to alterations in resting-state neural activity. Support vector machine discriminant analysis was used to evaluate the sensitivity/specificity characteristics of the ReHo index in discriminating between the ASPD individuals and controls. The results showed that, compared with controls, ASPD individuals show lower ReHo in the right cerebellum posterior lobe (Crus1) and the right middle frontal gyrus, as well as higher ReHo in the right middle occipital gyrus (BA 19), left inferior temporal gyrus (BA 37), and right inferior occipital gyrus (cuneus, BA 18). All alternation regions reported a predictive accuracy above 70%. To our knowledge, this study was the first to study the change in regional activity coherence in the resting brain of ASPD individuals. These results not only elucidated the pathological mechanism of ASPD from a resting-state functional viewpoint but also showed that these alterations in ReHo may serve as potential markers for the detection of ASPD.

Instruction in information structuring improves Bayesian judgment in intelligence analysts.

PubMed

Mandel, David R

2015-01-01

An experiment was conducted to test the effectiveness of brief instruction in information structuring (i.e., representing and integrating information) for improving the coherence of probability judgments and binary choices among intelligence analysts. Forty-three analysts were presented with comparable sets of Bayesian judgment problems before and immediately after instruction. After instruction, analysts' probability judgments were more coherent (i.e., more additive and compliant with Bayes theorem). Instruction also improved the coherence of binary choices regarding category membership: after instruction, subjects were more likely to invariably choose the category to which they assigned the higher probability of a target's membership. The research provides a rare example of evidence-based validation of effectiveness in instruction to improve the statistical assessment skills of intelligence analysts. Such instruction could also be used to improve the assessment quality of other types of experts who are required to integrate statistical information or make probabilistic assessments.

Chimera States in Continuous Media: Existence and Distinctness

NASA Astrophysics Data System (ADS)

Nicolaou, Zachary G.; Riecke, Hermann; Motter, Adilson E.

2017-12-01

The defining property of chimera states is the coexistence of coherent and incoherent domains in systems that are structurally and spatially homogeneous. The recent realization that such states might be common in oscillator networks raises the question of whether an analogous phenomenon can occur in continuous media. Here, we show that chimera states can exist in continuous systems even when the coupling is strictly local, as in many fluid and pattern forming media. Using the complex Ginzburg-Landau equation as a model system, we characterize chimera states consisting of a coherent domain of a frozen spiral structure and an incoherent domain of amplitude turbulence. We show that in this case, in contrast with discrete network systems, fluctuations in the local coupling field play a crucial role in limiting the coherent regions. We suggest these findings shed light on new possible forms of coexisting order and disorder in fluid systems.

Study of coherent reflectometer for imaging internal structures of highly scattering media

NASA Astrophysics Data System (ADS)

Poupardin, Mathieu; Dolfi, Agnes

1996-01-01

Optical reflectometers are potentially useful tools for imaging internal structures of turbid media, particularly of biological media. To get a point by point image, an active imaging system has to distinguish light scattered from a sample volume and light scattered by other locations in the media. Operating this discrimination of light with reflectometers based on coherence can be realized in two ways: assuring a geometric selection or a temporal selection. In this paper we present both methods, showing in each case the influence of the different parameters on the size of the sample volume under the assumption of single scattering. We also study the influence on the detection efficiency of the coherence loss of the incident light resulting from multiple scattering. We adapt a model, first developed for atmospheric lidar in turbulent atmosphere, to get an analytical expression of this detection efficiency in the function of the optical coefficients of the media.

Optimized suppression of coherent noise from seismic data using the Karhunen-Loève transform

NASA Astrophysics Data System (ADS)

Montagne, Raúl; Vasconcelos, Giovani L.

2006-07-01

Signals obtained in land seismic surveys are usually contaminated with coherent noise, among which the ground roll (Rayleigh surface waves) is of major concern for it can severely degrade the quality of the information obtained from the seismic record. This paper presents an optimized filter based on the Karhunen-Loève transform for processing seismic images contaminated with ground roll. In this method, the contaminated region of the seismic record, to be processed by the filter, is selected in such way as to correspond to the maximum of a properly defined coherence index. The main advantages of the method are that the ground roll is suppressed with negligible distortion of the remnant reflection signals and that the filtering procedure can be automated. The image processing technique described in this study should also be relevant for other applications where coherent structures embedded in a complex spatiotemporal pattern need to be identified in a more refined way. In particular, it is argued that the method is appropriate for processing optical coherence tomography images whose quality is often degraded by coherent noise (speckle).

Coherence and incoherence collective behavior in financial market

NASA Astrophysics Data System (ADS)

Zhao, Shangmei; Xie, Qiuchao; Lu, Qing; Jiang, Xin; Chen, Wei

2015-10-01

Financial markets have been extensively studied as highly complex evolving systems. In this paper, we quantify financial price fluctuations through a coupled dynamical system composed of phase oscillators. We find that a Financial Coherence and Incoherence (FCI) coexistence collective behavior emerges as the system evolves into the stable state, in which the stocks split into two groups: one is represented by coherent, phase-locked oscillators, the other is composed of incoherent, drifting oscillators. It is demonstrated that the size of the coherent stock groups fluctuates during the economic periods according to real-world financial instabilities or shocks. Further, we introduce the coherent characteristic matrix to characterize the involvement dynamics of stocks in the coherent groups. Clustering results on the matrix provides a novel manifestation of the correlations among stocks in the economic periods. Our analysis for components of the groups is consistent with the Global Industry Classification Standard (GICS) classification and can also figure out features for newly developed industries. These results can provide potentially implications on characterizing the inner dynamical structure of financial markets and making optimal investment into tragedies.

Secure fingerprint identification based on structural and microangiographic optical coherence tomography.

PubMed

Liu, Xuan; Zaki, Farzana; Wang, Yahui; Huang, Qiongdan; Mei, Xin; Wang, Jiangjun

2017-03-10

Optical coherence tomography (OCT) allows noncontact acquisition of fingerprints and hence is a highly promising technology in the field of biometrics. OCT can be used to acquire both structural and microangiographic images of fingerprints. Microangiographic OCT derives its contrast from the blood flow in the vasculature of viable skin tissue, and microangiographic fingerprint imaging is inherently immune to fake fingerprint attack. Therefore, dual-modality (structural and microangiographic) OCT imaging of fingerprints will enable more secure acquisition of biometric data, which has not been investigated before. Our study on fingerprint identification based on structural and microangiographic OCT imaging is, we believe, highly innovative. In this study, we performed OCT imaging study for fingerprint acquisition, and demonstrated the capability of dual-modality OCT imaging for the identification of fake fingerprints.